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Tommy_T
08-31-2010, 05:52 AM
Hello Forum, This is a first post and as it turns out a first personal project for me.

My First Project: General Lawn care Mule.

P - Programmable
A- Autonomous
C - Controlled

M - Motorized
U - Utilitarian
L - Lawn/Garden
E - Equipment


Project budget $2500.00

Because I still have to work I'm giving myself 1 year to complete the project.

Tasks it most perform
1) carry payload of 150lb (at least 2 bags of potting soil)
2) mow grass (both manually(remote control) and autonomously(with supervision))
3) clear snow for drive and walkways manually(remote control)
4) simple to control (even my 75yr old mother can use in her garden)


The main controller is going to be a net-book PC(or my dual core laptop if needed)
remote control operation will be Bluetooth(wireless keyboard) and WiFi.

Servo control is analog(0V to 5V).
Speed controller RobotQ Ax2550 - (Sabertooth 2x25(for testing) and Peripheral Attachments )
Transducers Phidgets 3/3/3, Phidgets 8/8/8, Phidgets high speed encoder cards(at least 2) ,at least 2 encoders.
Analog output Labjack U3-LV

Test bed will be a used power wheelchair.

While disassembling the test bed I got a look at the drive that came with it (Penny&Giles 50/70 Amp VSI speed control).
And I gotta say it is a sweet drive, and if theres a way of using it I could shave $500 off the budget.
The other sweet thing about that drive is it has built in safety features like battery level inductions, differential
analog monitoring ,analog voltage level monitoring and Motor current monitoring.(shorted or stalled motor can't take out a drive..sweet)

using the P&G drive would remove the need for a Microprocessor as a hart beat also saving $100.

But it has a built in acceleration/Deceleration loops that would cause me issues while under autonomous control.

First question: Has anyone ever tried to remove or change the Speed profiles on a Penny&Giles 50/70 Amp VSI speed control ?.

I goggled it and found references to a Speed profile programmer for Dealers, OEMs and Manufactures, but none for end users.

If I can find a way to use the P&G drive I could slip the below item into the budget. (which would be sweet)
http://www.snowblowersdirect.com/Ariens-72600500/p829.html?utm_source=froogle&utm_medium=shop+portals



Feel free to correct me when you see I'm wrong.

Tommy

jdolecki
09-01-2010, 10:40 AM
I'm doing the same thing for a robot base but i have a Jazzy power chair base. ( 100 Dollars craigslist) I have an e-mail into P&G about the drives thay make.

This was the first reply


The parts number you gave are for our VR2 based systems. These have no external input devices except the joystick and an attendant module since these are made primarily for wheelchairs. The R-net system, which is our higher end rehab controller does have modules that handle other input devices.


They R-net is expensive.


So I asked about the communication protocal between the Joystick (Which the also make) and the controler which im waiting for a reply now.


I still need 2 new batteries 12v 35ah $140


Im using a ZOTEC mother board for a brain and running MSRS to control it.


I also was told to just put that controller and joystick on e-bay to offset the cost of a motor controller. Which I will end up doing I think.


So for a 2500 budget you should be able to put together a nice bot.

Tommy_T
09-01-2010, 09:17 PM
So I asked about the communication protocal between the Joystick (Which the also make) and the controler which im waiting for a reply now.
jdolecki
I also tried to get the wiring for the joystick to the drive from them, but got no help. But after
opening the joystick it was easy to interface with 2 analog voltages DAC0 for speed DAC1 for
turning. it will only work between 1 and 4V with 2.5 as stop. If you don't want to add analog
you could also control the drive with 2 RC servos.

If I could overcome the Acc/Dec problem I would love to use the P&G drive.

I may be interested in that drive if you are thinking about unloading it, they are very sweet drives.


So for a 2500 budget you should be able to put together a nice bot.
Right now I'm looking at navigation and tracking(not using boundary wire). every idea I come up with
seems to take big bucks from the budget.

Because I come from the manufacturing industries the first direction I'm heading is looking at it as a CNC
machine programed in G-code(it's not working out good for me).


Tommy

zoomkat
09-03-2010, 01:23 AM
Not sure why people try to build lawn mowing devices from scratch, but probably not such a good idea (poor cutting and possibly dangerous). A better deal would be to convert an existing riding mower for autonomous/remote control. Mowers like below can haul 200+lb on top (aka fat people), have onboard electric start/generator, and with larger gas tanks can run for many hours/miles. Once the project is done, one still has a riding mower that can be used as origional or sold to recover some of the cost. On the local Craigs list old working riding mowers can be had for $150 and up.


http://www.walmart.com/ip/Weed-Eater-One-WE261-Riding-Lawn-Mower/13346325

Tommy_T
09-03-2010, 06:42 AM
Not sure why people try to build lawn mowing devices from scratch
zoomkat
I bet that type question comes up often when ever some teen age girl wants to sail around the world
solo, or that 75 year old grandpa wants to climb mount everest. I can't even figure a motive for either
of the above examples, but for myself I gravitate towards projects that have not been completed
yet. I understand that thousands of people have taken on the lawn mowing project(some can even fly),
but no one has cracked Autonomous lawn mower nut yet. I also understand that for far less
money I can buy a cute little toy that could mow my mother's lawn almost(they are very
limited currently in size of lawn ,slops, dog crap and attractive cutting paths).


build lawn mowing devices from scratch
At this point I'm thinking it would be cheaper to design and build from scratch, then mod. a wheelchair frame
to the task.(I'm on my second one as a test bed, trying six wheels on the ground, not four).


and with larger gas tanks can run for many hours/miles.
Part of the project is to think GREEN, while not in the current budget at some time solar cells will
be added to charge the batteries.

Tommy

lnxfergy
09-03-2010, 09:08 AM
zoomkat
I bet that type question comes up often when ever some teen age girl wants to sail around the world
solo, or that 75 year old grandpa wants to climb mount everest. I can't even figure a motive for either of the above examples, but for myself I gravitate towards projects that have not been completed yet.

+Rep.

-Fergs

DresnerRobotics
09-03-2010, 01:22 PM
Not sure why people try to build lawn mowing devices from scratch, but probably not such a good idea (poor cutting and possibly dangerous). A better deal would be to convert an existing riding mower for autonomous/remote control. Mowers like below can haul 200+lb on top (aka fat people), have onboard electric start/generator, and with larger gas tanks can run for many hours/miles. Once the project is done, one still has a riding mower that can be used as origional or sold to recover some of the cost. On the local Craigs list old working riding mowers can be had for $150 and up.


http://www.walmart.com/ip/Weed-Eater-One-WE261-Riding-Lawn-Mower/13346325

Some people like actually building things instead of just talking about it.

zoomkat
09-03-2010, 02:53 PM
Some people like actually building things instead of just talking about it.
Well, so far all of this has just been talk, so I'm not sure as to the point of your statement. That being said, I think this project as currently described will probably fade away as a collection of half built parts. The difficult part of "Autonomous" operation does not appear to have been addressed. I've seen various lawn mowing bot pix on the web and have my opinions as to their good/bad points. If the most difficult parts of a project isn't resolved early on, then generally a lot of time and $$$ is waisted. Having ~1 acre of grass to cut every so often, I'm familiar with real world grass cutting issues. Just giving some practical opinions to the project person before he finds himself "in the weeds" with his project.

DresnerRobotics
09-03-2010, 03:36 PM
Well, so far all of this has just been talk, so I'm not sure as to the point of your statement. That being said, I think this project as currently described will probably fade away as a collection of half built parts. The difficult part of "Autonomous" operation does not appear to have been addressed. I've seen various lawn mowing bot pix on the web and have my opinions as to their good/bad points. If the most difficult parts of a project isn't resolved early on, then generally a lot of time and $$$ is waisted. Having ~1 acre of grass to cut every so often, I'm familiar with real world grass cutting issues. Just giving some practical opinions to the project person before he finds himself "in the weeds" with his project.

I was mostly referring to your posting style in general, not this thread in particular. That is, that you tend to lean on the negative side of things in most of your posts, yet have failed to show any real work of your own that would validate your largely negative and opinionated stance.

Tommy_T
09-03-2010, 04:30 PM
I think this project as currently described will probably fade away as a collection of half built parts
zoomkat
While my chances of cracking the Autonomous nut may only be 10% within the one year time frame,
I still have a useful tool for my mom.

I would love to post a few pictures, but with the frame covering being 10lb of duct tape, 4 yd of cardboard,
plastic tarp I even think theres some bailing twine in there someplace. I'v run it in the rain with no problems
so the duct tapes is working, it just looks like hell.

cosmetics never made it to the budget.

Tommy

jdolecki
09-03-2010, 04:43 PM
Tommy what are you running for a motor controller?

Have you gotton any reading on the amps the motors draw?

My whole goal right now is to develop the programming for the AI

putting a payload or mower on it is easy

thanks john

I will post pics this weekend.

zoomkat
09-03-2010, 05:02 PM
I was mostly referring to your posting style in general, not this thread in particular. That is, that you tend to lean on the negative side of things in most of your posts, yet have failed to show any real work of your own that would validate your largely negative and opinionated stance.
I think I would be providing a disservice to the poster if I kept quiet about potential issues and solutions I think might be important for the project. I guess some might consider "wear a lifejacket" as negative if they really don't to wear one. I often see projects that have critical issues that are ignored/overlooked and the projects usually fail. As to my fun projects/tinkering, I generally only do things to verify an idea I have is valid, using the minimum parts and $$$ required to get it done. I usually do my own car/truck/motorcycle repairs along with fixing the usual household problems, so actual bot building is currently down the elective list.

Tommy_T
09-03-2010, 07:35 PM
Tommy what are you running for a motor controller?
jdolecki
I have 2 drives I'm using for setting up the control software, a
Sabertooth 2X25 (would like to have a 2X50 but can't find one)
and a P&G dual 70Amp drive that came with the first testbed
I now also have a MK5 drive from the new testbed but have not
looked at interfacing it yet(picked up last night), I'll look at that this weekend.


Have you gotton any reading on the amps the motors draw?
Everything tells me these motor have a stall current of @40Amp.
I have not taken any direct reading just what I'v found on the net.

Tommy

jdolecki
09-05-2010, 07:28 PM
Here are 2 pics
First bare chassis no batteries or motor controller
Second is placementof the Zotac Mother Board

http://forums.trossenrobotics.com/attachment.php?attachmentid=2084&stc=1&d=1283732660

http://forums.trossenrobotics.com/attachment.php?attachmentid=2085&stc=1&d=1283732660

Tommy_T
09-05-2010, 08:41 PM
jdolecki
Nice looking platform you have there, them motors look sweet, I have a set
of them foam filled wheels also. I find I do have to replace them due to slipping
on the grass while pushing a 20" mowing deck on my lawn with 20+ deg. slops.

My footprint is not much different then yours, that includes weight distribution,
but I found that if it has to stop fast it would nose over, in my case the mowing
deck would bottom out on the lawn, digging dirt at times. right now I using the
battery that came with the mowing deck which is much lighter then the 2 car
batteries that are going to be installed soon, that should help with traction and
help keep it from nosing over. if not 2 small casters should do the trick.

One of the issues I have to answer is the lost motion in the gearbox. both sets
of motors I have(each about 6 years old) have about 1 deg of Backlash. the fact
that I have 2 casters in the back and that my lawn is uneven them 2 caster cause
uneven forces on the frame(only one caster on the ground,the forces want to turn it that way,
Backlash lets it turn that way). the testbed I just picked up has a gearbox connected
to a 8" ball screw for seat tilting, looks like the thing can lift 300lb. I'm going to use that
to raise and lower a single wheel between the caster for when it is moving forward,
when turning it would be raised to let the caster take the load. this should help with
gear backlash and let me use the P&G drive because smaller corrections on uneven surfaces
would be needed(I think). if not I could try replacing the casters with fixed wheels and raise
and lower a caster for turning.

This is a trick dump trucks use I believe.

Tommy

I gotta think if there was one place where all the information learned doing
these projects could be found, I'm sure this nut could be cracked much faster.

Adrenalynn
09-06-2010, 02:17 AM
Have you torn the motor controllers apart and looked at the boards? A lot of these controllers are actually OEM Curtis. And documentation/pinouts are fairly easy to come by.

High-current/high-voltage motor controllers are actually pretty available, as they're common in combat robotics.

I've used RobotPower / Sidewinder's that are 80A or even 160A / channel. I have other controllers that are up to double that.

Tommy_T
09-06-2010, 07:10 AM
Have you torn the motor controllers apart and looked at the boards?
Adrenalynn
Yes, while putting a scope on it to find a way to interface it to my main controller(netbook PC)
I did get at look at it, it seems it's a Pic based motor speed controller, the OEM has a serial
programmer to set speed profile which is also available to Dealer, but not end users(for liability reasons they say).


High-current/high-voltage motor controllers are actually pretty available
That is true, and I had planed to use the http://www.roboteq.com/brushed-dc-motor-controllers/ax2550-ax2850-dual-120a-brushed-dc-motor-controller.html
but after interfacing the P&G drive to the main controller(netbook PC) and using it, the more I liked
it(for safety reasons), also the $600 cost could then be moved to tracking and navigation senors or
a set of tracks(not sure about them yet).

After playing with this project all week I'm beginning to think the problem is not the Acc/Dec loops.
In my head I figured once I get the feedback loops connected and programed the Sabertooth drive
could do the job under light loading(only 25Amps so could not stall the motor without frying the drive)
, but it had similar issues, much better, but not perfect.

possible problems.
1) Lost motion in the drive train. (a CNC with linear feedback and .010" lost motions would not be sable)
I currently have 155 encoder counts of lost motion, in the CNC machine world the only fix would
be to remove the backlash, or put the encoder on the motor for semi-closed loop control and add
backlash comp. I'm looking at adding a way to push the lost motion always in the same direction (see last post about adding third wheel)

2) A two wheel drive mixed platform is not sable enough for uneven terrain. this can be seen when
running open loop(no feedback), if one wheel hits a curb the platform will turn that direction.

still wondering if three wheeled would be better then four?(see last post about adding third wheel)

3) Programming, it's possible my "Tim the toolman" thinking is wrong. throwing a few hundred Amps
at the problem is not going to help. in my case I'v been increasing the opposing wheel's viscosity to force it
back on course. with the P&G drive as OEM programed the Dec. loop is ten times shorter then the
Acc. loop, maybe I should program it to decrease the opposing wheel's viscosity to let it catch up,
which should reduce the overshoot errors. the problem I see with that is the thing would get stuck
often. It's also possible to use the feedback devises to track it's location(dead reckoning) then use
the software to make correction in an absolute mode.(line follower where the line is in software)
The problem I see here is related to the only abs feedback I have is a Phigets 3/3/3 but
that can only give me a few degs. accuracy(ouch!).

Feel free to add to the list.


Tommy

Adrenalynn
09-06-2010, 12:49 PM
>> the more I liked it(for safety reasons)

I have to ask what those "safety reasons" versus a combat robot motor controller would be.

>> also the $600 cost

That's about double the cost of a good 160A 2-channel motor controller, or half again the cost of an outstanding multi-channel.

>> a CNC with linear feedback and .010" lost motions

Fortunately, you're not building a mobile CNC, you're building a lawn mower... Now, if'n you're wanting to machine your yard, that's probably a whole different topic. Your CNC table [had better be] a darned site more level and your reference frame a whole lot more fixed, not to mention that the tables tend to be a pretty good bit smaller. ;)

Robots, with hobby technology, oscillate a bit. What you're needing is a PID loop and maybe some good Kalman filtering to tame it down as much as you can.

Tommy_T
09-06-2010, 02:08 PM
jdolecki
If you can man-up and post pictures I should be able to swallow my pride and post some also

the last two pictures are of the new(to me) testbed I got this week, it has very strong 4 pole
motors, and wheels that should give good traction(they are the same size as my current tires).
seems like a very stable platform, but only has 2.5" ground clearance, if I'm going to use it, that
will have to change.

first picture is my current testbed with the mower deck attachment(snow attachment not made yet),
I have not installed the payload dump box yet.

Tommy

Tommy_T
09-06-2010, 03:20 PM
I have to ask what those "safety reasons" versus a combat robot motor controller would be.
Adrenalynn
Keep in mind I understand all the safety features built in the the P&G drive can be mimicked with a
microprocessor and a few solid-state relays, but when your dealing in the higher amps solid-state
relays get kind of pricey.

Safety features in the P&G drive
1) differential analog voltage from the joystick(which is where I interface to the Main controller(netbook PC)
to the P&G drive. this arrangement is less susceptible to EMF noise, the P&G hall-effect joystick has
5 analog outputs, if any one of these are missing or out of range the drive will shut down and flag a
fault.

2) If the main controller(netbook PC) shuts down for any reason, or the analog output unit fails the
P&G drive will shut down and flag a fault. all battle bot drives will take off full reverse. a good
example of this can be seen when powering up the drive with the main controller turned off, the
P&G drive will shut down and flag a fault, battle bot drive will take off.

3) built in current limiting, built in temp. monitoring, built in battery level monitoring.

4) built in motor brake control (24vdc)



What you're needing is a PID loop and maybe some good Kalman filtering to tame it down as much as you can.
Granted I have only spent maybe 20 hours trying to tune the PID loop(without the results I want), but I see the days getting shorter
and the nights getting cooler and I feel compelled to find an answer soon.

Tommy

Adrenalynn
09-06-2010, 03:35 PM
I'd be careful with the "all will ____". None of my large controllers will do any such thing if they lose either analog or PCM.

But regardless - I don't really care what motor controller you decide to use. I was just curious.

The real meat there was PID and filtering.

Tommy_T
09-06-2010, 03:52 PM
I'd be careful with the "all will ____". None of my large controllers will do any such thing if they lose either analog or PCM.
Adrenalynn
You are correct, That line should read "All the low cost units I looked at so far"
I should have "First project syndrome" tattooed on my forehead so everyone knows my
information is very limited, I do appreciate it when I'm corrected .

I also come to agree with you about the drive not being the problem.

I do have sweet feedback
Q axis to +/-.006 Deg.(incremental encoder 10000 x 4 CPR )
A axis to +/-1 Deg. Abs.(Phidget 3/3/3)
X axis +/- .010"(incremental encoder 600 x 4 CPR with 8" wheel)

The answer can be found in properly using the feedback in software.

A good example of why I suspected the Dec/Acc as the problem. If I turned off it's X axis feedback
it would Acc as programed, if I then turned it back on while the drive was at it's max set point the
testbed would continue bucking between Acc/Dec trying to catch up to the PID. while that problem
did not show up with the Sabertooth drive. but that could be dealt with in software, simple as pause
the program if the Analog voltage gets to the max set point.


My bad!
Tommy

jdolecki
09-06-2010, 06:50 PM
Tommy the mower look good your way ahead of me.

Im approaching it from the Navigation standpoint first cause if I cant get it to stay in the yard by itself and not run over the flowers and hit the trees this is futile project and will just be a RC lawnmower which aint so bad either.

Also i would like to enter it in the robo Magellen contest here at Chibots

If I Can get that sorted I will then just build a custom mower deck probably a tripod design with 3 wheel steering and the mower being in the center of the tripod. See design pic of powered castor.

I been researching the tires and rims online and there are not may choices so I will build two adaptors to run wider tires which are a couple buck on sale at harbor freight and there is a lot of choices for tires.

I been researching the Drives online and I really like the Saxbertooth 2x50.

I thought about using the P and G drives but it will be too much work, and they dont seem to be intrested in supporting the robotics community plus the combat robots have really sorted all the issues out already its just a matter of how much money I want to spend on a drive.

So I will replace it all in 3 weeks with the sabertooth drive after I save my pennies.

http://forums.trossenrobotics.com/attachment.php?attachmentid=2091&stc=1&d=1283816023

Tommy_T
09-06-2010, 07:18 PM
I been researching the Drives online and I really like the Saxbertooth 2x50.
jdolecki
I also have the hots for a Sabertooth 2x50, but can't seem to find one, I got the sabertooth 2x25
for my original design for a mower deck, 3 Scott classic reel mowers powered by two motors,
the earthwise 20" i'm using for tests is a cordless 24vdc which made interfacing a breeze. I'm
using the sabertooth 2x25 to trouble shoot my drive software, but I have to be careful with it.

Tommy

zoomkat
09-06-2010, 08:33 PM
I also have the hots for a Sabertooth 2x50, but can't seem to find one, I got the sabertooth 2x25 for my original design for a mower deck

If I already had a 2x25, I think I wold look at paralleling in another set of MOSFETs to increase the current capacity.

Tommy_T
09-06-2010, 09:06 PM
If I already had a 2x25, I think I wold look at paralleling in another set of MOSFETs to increase the current capacity.
zoomkat
I looked at it, but as I get older connecting to surface mounted boards seems to be getting harder.
Fact is I'm going back to the P&G for a main motor drive, the Sabertooth 2x25 is going to run the
motor on the linear actuator to raise and lower the third wheel?, the other channel could be used
to raise or lower a snow plow blade.

Tommy

zoomkat
09-06-2010, 09:25 PM
The below motor controller might be a less expensive alternative to the sabertooth. How much current does your linear actuator require, and does it contain an internal pot?.

http://secure.oatleyelectronics.com//product_info.php?cPath=94&products_id=206&osCsid=30093449b694ae247d94c2bcce5d0560

Tommy_T
09-07-2010, 06:03 AM
How much current does your linear actuator require
zoomkat
All I can do is guess at this point, the device was made by SKF but all the motor
characteristics are not listed, on close inspection it seems they were never printed
on the label. they did have a wheelchair manufacture's label and part number, but
when goggled, gives me the GPD of china.

My best guess is it stalls at @10-15Amp, with @2-4Amp no load.


and does it contain an internal pot?
The actuator has no internal feedback(just 24vdc gearmotor connected to a ball screw), but I did get one analog tilt senor, a reed tilt switch and
two limit switches which I'm sure I can find a place for.

Tommy

Tommy_T
09-08-2010, 06:47 AM
Fortunately, you're not building a mobile CNC

What if it was?. or at least I thought of it that way.

If I was going to have an industrial robot(Fancu,Yaskawa..ect) do a job for me chances
are I would program it in G-Code.

Simple example:
N010 G90; (this line sets Abs mode, G91 would be incremental)
N020 M4; (this line would turn on the spindle CW, in my case it would turn on Mower)
N030 A190.5 S10; (this line tells A axis to go to 190.5deg at 10deg per sec)
N040 X123.250 F10; (this line tells X axis to go to 123 1/4" at 10" per sec)
N050 M3; (this line would turn off the spindle , in my case it would turn off Mower)
%; (End of program a M99 would have it repeat the program)

The sweet thing about G-Code is it can be edited with notepad, excel or any text editor,
also there are lots of CAD/CAM programs to automate G-Code programing and implementation.

theres been a big push in the manufacturing industries over the last ten years in digitizing parts
to aid in CAD/CAM production, and they have made good progress, why can't them systems or
methods be used for this type project.


Also i would like to enter it in the robo Magellen contest here at Chibots
jdolecki
I wonder if you used the above thinking, would it improve your chances of winning?

Tommy

lnxfergy
09-08-2010, 07:55 AM
theres been a big push in the manufacturing industries over the last ten years in digitizing parts
to aid in CAD/CAM production, and they have made good progress, why can't them systems or
methods be used for this type project.

Because an autonomous mobile robot is *not* a CNC machine. For at least 2 major reasons:


With CNC, dynamics are not as important -- a single motor controllers movement in a single axis. When you move the X-axis, you don't get angular rotation or Y-axis drift. With your robot, which uses differential drive, there are two motors whose difference in speed controls angular velocity -- driving forward in a straight line means the motors have to be perfectly in sync at all times (something that generally can't be achieved all the time, for instance, if the robot hits a rock on one side, that wheel suddenly loads up a bit and it will take a short time for the PID to catch up).
With CNC you are firmly attached to your frame of reference. If you want to know your location within the real world, you need to measure travel relative to the world -- but the odometry from encoders is only one part of it. Even if you were able to get the motors perfectly aligned for all time, how are you going to make sure the wheels *never* slip, ever, in a million years? Because that's what dead reckoning would require -- if you have wheel slip, you'll eventually get off the intended course, and you need to correct for that.

The typical approach to mobile robot navigation is to maintain sensor readings in a locally consistent frame of reference (one centered around the robot, or a frame maintaining the odometry), and then to *localize* the robot periodically through the use of some sensor (typically a laser scanner, GPS + filtering techniques, or a visual approach). By localizing the robot, you cancel out the error in the odometry/drivetrain.

Now, you could build a G-code interpreter on top of such an approach in order to give motion commands, but underneath it, you'll need a localization routine (especially for something like RoboMagellan, where the distance and terrain covered are sure to impede any dead reckoning approach).

-Fergs

Tommy_T
09-08-2010, 05:21 PM
Now, you could build a G-code interpreter on top of such an approach in order to give motion commands, but underneath it, you'll need a localization routine (especially for something like RoboMagellan, where the distance and terrain covered are sure to impede any dead reckoning approach).
lnxfergy
After reading the rules for the RoboMagellan contest, I can see the above working.


you'll need a localization routine
As it turns out CNC machines have to also, they have sub routines to check the tool with
edge finders, lasers and optical systems to account for things like tool wear.

In my case maybe I could use a G45 [X value] [Feed rate value] this would buffer the current bearing,
then zero the gyro, Acc to Feed rate value using the gyro for directional feedback until math.Abs(Q) < 1 (@3sec),
then Q axis would be used for directional feedback until end of line.

A G46 [X value] [Feed rate value] This would buffer the current bearing, Acc to Feed rate value using
the digital tilt comped compass (Phidget 3/3/3) for directional feedback

The next thing I'll look at is ultrasonics, I see they have some that go out to 200"+
I still have room for 4 analog inputs.

Any feedback on ultrasonic transducers would be much welcomed.

My net-book main controller draws the line at video while checking the feedback devices at 50Hz.

Tommy

Adrenalynn
09-08-2010, 05:35 PM
That's hardly localization...

Tommy_T
09-08-2010, 06:17 PM
Adrenalynn
Quick question, on an uneven surface would 3 wheel be more stable then 4?
with 4 wheels I can see one rear wheel being in the air at some time which could
cause it to pull that way, where one rear wheel would always be on the ground
(220lb platform) and if it hit a rock I could see it pulling more evenly on both drive
wheels. but I could be wrong.


That's hardly localization...
I should also mention I'm not a machinist.

My day job is systems integration which means I never get to work on any one technology
long enough to gain the experience my age would suggest. With that said, I can see a connection
between a CNC machine counting turns of a ball screw to get to a location and dead reckoning
and then use some type of device or method to re index the physical and software values. In
todays CNC industries they may be looking at +/- .0001" and they can do with high count encoders
and ground ball screws, I only need +/- 2", so I wounder if I could use a similar approach
for my project.

example:
Use high count encoders for dead reckoning then from time to time call a sub routine that would
take the mule to one of four fixed markers(one each corner, or center of lawn?) that it could then
use to correct for any missed counts.

These markers could be rectangular with each side a different length. I did some tests with a
rotary laser($7+shipping e-bay) and a web cam (second picture below). I can also see this
type device giving me feedback on grass height and even whats been cut for minimum overlap.

Picture 3 shows why I like the G-Code approach.
Each of the zones could be a sub routine defined by it's start location, Length and width.
if for any reason it aborts the program, it can be restarted at any Zone, or if my mom wants
to make her deck bigger only them zones would need to be reprogrammed.

A program may look like below
N05 T1; {this sets the offset for a 20" dia. mower}
N010 G90; {sets Abs mode}
N015 G58; {this runs sub routine to align itself to Marker #1 and zeros X and Q axis} this is the main Datum point
N020 G35 [X value] [Time value]; { this turns on the routine to re-index on Marker #5, when X
moves the amount of X value or Time has past the Time value(which ever comes first)}
N025 G01 [X value] [Y value] [Feed rate]; {this would move the mule to start of Zone 1}
N030 M4; {this turns on Mower, and Turns are CW, M5 the turns are CCW}
N035 G41 [X start] [Y start] [X length] [Y length] [feed rate]; {starts sub routine to pocket mow Zone 1}
N040 M3; {turns off mower}



If these ideas have been kicked around a lot making these posts (kicking a dead horse) please let me know.
this is all very new to me.
Tommy

Tommy_T
09-14-2010, 08:05 AM
After much internal debate it seems testing would be the best way to
find out if 3 or 4 wheels would be best for uneven surfaces(like a lawn).

the lowest cost would be 3 wheels, thats where I started.

While my first tests on blacktop worked out sweet, the lawn is the real test.

Picture below is the rear caster area of the Mule.

Tommy

jdolecki
09-20-2010, 05:18 AM
Hey Tommy

Have you seen this pump?

HYD pump from American Science and Surplus.

For people with bigger bots this seems to be a good deal for 49.00.

http://www.sciplus.com/categorySpecial.cfm

Tommy_T
09-20-2010, 07:40 AM
HYD pump from American Science and Surplus.
jdolecki
You may be right, Hydraulics would be a good option for raising and lowering the rear stabilizing wheel,
With the electric drive I'm using which can pick up 300+lb it takes 2sec. per inch at full speed.

As it turns out I'm now looking at adding one more linear movement, Lifting and repositioning Q axis,
I should say I hope to do it with only one linear movement(Thinking V-shaped fork design could lift and turn).


Also I'm now thinking the rear wheel should be a drive wheel, I thought the rear wheel as designed,
would also give me a way of pushing the lost motion in my main drive gears one direction so it could
be comped. but I have to turn to take advantage of it, if the rear wheel was a Drive wheel I could
then push the lost motion while going straight(using a Current feedback loop, I think).

I looked at the American Science pump, but the only stats they list is the line limit Psi @3
I find it hard to believe that @7Amps could only supply 3Psi (I'l look for more PDFs on the pump).

I was just working at a company that made Hydr pumps(SPX), their dumpster was full of different types of
pump parts.

Tommy

Tommy_T
09-25-2010, 07:19 PM
Busy week for my PC for work so had little time to work on the software for my Mule
But I did get the front wheels change out.

new wheel 9.5" wide, 17.5" tall
old wheel 3" wide, 14" tall

found these at a place called Tracker Supply at $60us each with the rim

While I only had a few hours to test them out, they are sweet very stable, but they do draw more
current. with the test mower deck installed and a 15deg slope I'm drawing 30amp with the old wheels
it was about 20Amp.

Picture below old wheel next to new wheels installed.

Tommy

Tommy_T
11-02-2010, 08:22 AM
Some changes, some playing, some progress.

The broom idea for moving leaves around didn't fly. rotating sweeper seems like the way to go.

Tommy

jdolecki
11-03-2010, 03:47 AM
Looks good.

I did see in the Robo Magellan rules there is a weight limit.

So I dont think we willl qualify unless they make a heavy weight / unlimited class?

Tommy_T
11-03-2010, 05:00 AM
I did see in the Robo Magellan rules there is a weight limit.
jdolecki
With a 50lb weight limit you'd would be hard pressed to use wheelchair motors that
weigh 15lb each, I changed out my motors for larger four polled ones that weigh 25lb
each, so I couldn't even enter my motors taped to a laptop. I'd think with the 100lb
ballast(2 sand bags) I added my Mule is at 295lb without any attachments.


Looks good.
Thanks for being kind, but looks never was part of my project. but my Mule has been
sitting out exposed to the environment for the last two weeks without any water
damage(Sweet!), we even had a large storm come through last week with 60mph(wind gusts)
and lots of rain(but no snow, which I was hoping for so I can test out my new snow plow).



Do you have any pictures of your current platform?

Tommy

Tommy_T
11-30-2010, 08:00 PM
With the 18" wheels the mule could move 20mph in a runaway condition(like loss of feedback)
somewhere there should be a rule written that you should not let your Mule run faster then you
can. so I geared it down to 7mph max.

through test I found one rear caster to be unreliable, testing two now but see me replacing the
casters completely with a rear drive wheel

Tommy

jRaskell
12-01-2010, 08:09 AM
somewhere there should be a rule written that you should not let your Mule run faster then you


If that is spoken from experience then I think we need to hear more.

Tommy_T
12-02-2010, 03:43 AM
If that is spoken from experience then I think we need to hear more.
jRaskell
The mule has been very well behaved so far, while there has been a few software oops in the
beginning, each time they happened I immediately checked to see if any seen it(no one did). Maybe
that should also be a rule, if no one seen it, it didn't happen.

The reason I'm more concerned now is I'm in the house while the Mule is outside plowing snow, before
I'm standing next to the Mule ready to hit the E-Stop if theres a problem.

Tommy

jes1510
12-02-2010, 12:24 PM
I love these projects! Video! We demand video!

Tommy_T
12-02-2010, 06:57 PM
Video!
As soon as we get some snow to plow I'l get some footage.

My lover knows how much I'm been looking forward to some snow, and yesterday as I was
driving to chicago, it did start to snow(flurries) at home, so she calls me telling me the Mule
is outside yelling my name and watching the snow come down. guess she had to rub it in
that we were getting snow but I couldn't be there. by the time I got home the snow was all
gone.

Tommy

Tommy_T
12-03-2010, 07:00 PM
There comes a time in every young Mule's life when it needs to man-up(wear chains)

Tommy

Tommy_T
12-04-2010, 06:43 PM
The Mule's first snow


YouTube - george_0001.wmv

Tommy

jes1510
12-04-2010, 08:54 PM
Nice! A salt spreader on the back may be helpful as well. Great work!

Tommy_T
12-05-2010, 05:56 PM
A salt spreader on the back may be helpful as well
I talked to my mom about this but she said salt hurts her dog's paws:confused:
maybe sand spreader?

Tommy

darkback2
12-05-2010, 08:12 PM
That is really cool! Now you just need a wireless camera on the front so you can plow the drive way from the comfort of the living room couch! Your making me wish it snowed more where I live!

DB

Tommy_T
12-05-2010, 08:46 PM
Now you just need a wireless camera
darkback2
The Mule has a 3meg webcam that I'm working on, with the netbook wifi connected to the house
PC(laptop) and running a webcam there is a very large lag time in commands to the Mule, without the
cam running the lag is not present, working on that soon, most everything I'v worked on lately to
get ready for the snow was machination, wheels,weight,plow,weatherproofing.. etc..

As is I can sit at the kitchen table with my laptop so I can keep an eye on it at all times



Tommy

jRaskell
12-06-2010, 08:11 AM
running a webcam there is a very large lag time in commands to the Mule, without the cam running the lag is not present


If the webcam is loading the PC more than 80%, try adjusting the priority of the webcam process and your command/control process. Increase the priority of the process receiving/processing commands and/or decrease the priority of the webcam process.

darkback2
12-06-2010, 08:22 AM
Either way its still really cool. Great Job.

DB

Tommy_T
12-07-2010, 04:55 AM
If the webcam is loading the PC more than 80%
jRaskell
Is it that, or because everything is running through a single USB hub?
1) Analog Output for the drives, and digital I/Os (limit switches, and switching)
2) Phidgets 3/3/3 for feedback(digital compass, gyro, acc)
3) Phidgets High Speed Encoder card for feedback
4) Webcam

I now have a US Digital USB4 to replace the Analog Output, I/O and High Speed counter with a single unit
but have not install yet.
http://usdigital.com/products/interfaces/pc/usb/usb4/

Tommy

Tommy_T
12-19-2010, 07:05 AM
try adjusting the priority of the webcam process and your command/control process
jRaskell
You were right, seems by reducing the sampling rate of the gyro(was 10 msec, now 100 msec) the problem is gone(Sweet!, and Thanks!)

But, while doing the plowing in video below the Mule sheared a bolt that held the wheel hub to the drive
axle, causing one wheel to stop turning(what a drag). replaced single 1/4-20 bolt with two harden steel .25" dowel pins.

YouTube - George_0003.wmv

Tommy

Tommy_T
12-24-2010, 10:28 AM
Life is Sweet!

Today my mom got a chance to play with the Mule, she said she like it and would use it, once I fix the depth perception issue.

Shouldn't be too hard.

Tommy

jRaskell
12-28-2010, 08:33 AM
Glad to see you're getting the kinks ironed out. That's a cool little remote plow you have there.

Tommy_T
02-01-2011, 08:09 AM
If I put a snorkel on the Mule, it could now be an ROV


once I fix the depth perception issue.
Putting a camera up by the upper headlight facing down over the plow
fixes the depth perception problem.

Tommy

jdolecki
02-01-2011, 09:18 PM
You should be getting a lot of practice tonight !!

This blizzard should be a great test .

john

Tommy_T
02-02-2011, 01:03 PM
This blizzard should be a great test .
jdolecki, that storm spanked the mule.

need to add at least 300lb I'm thinking.

YouTube - george_0005.wmv

Tommy

jdolecki
02-03-2011, 08:04 AM
I like the view from the "Mule Cam"

jdolecki
02-08-2011, 12:29 AM
What you need are tracks! After a search for Snow blower tracks this came up.

http://www.snowblowersdirect.com/Images/Ariens-72600500/i829.html

They are made by Ariens.

You should call Ariens ask nicely and say you will put an Ariens sticker on the side. And they might give you a set.

I gottn many free thing just by making a phone call and explainning what im doing and offer to put there name on it.

seesoe
02-08-2011, 11:23 AM
What you need are tracks! After a search for Snow blower tracks this came up.

http://www.snowblowersdirect.com/Images/Ariens-72600500/i829.html

nice project, i agree with jdolecki, tracks would be nice on there.

very interesting link, i've thought about tracks for my project for a while, but now that i've gone 2wd not going back to tank steering.

Tommy_T
02-09-2011, 07:12 AM
What you need are tracks!

i agree with jdolecki
I would also, if, I had to ever go outside to get the Mule unstuck, or if the Mule didn't
have to start mowing grass again this summer.

tracks would do a lot of damage to the lawn.

While yes the Mule got spanked by that last snow storm, it did teach me a few things.

1) Need more weight. (added 140lb of sand to test how much weight is needed)

2) Theres only so much a 50" plow can do, a snow blower can deal with 5ft drifts.
I'v seen 24Vdc snow blows, but they are very small. I'd need a 40" electric snow blower.

the other option is plow when under 8", in last snow it would needed plowing every 2hrs.

Tommy

jdolecki
02-11-2011, 07:27 PM
Didi you see this one? Came up on the Parallax fourms

http://www.youtube.com/watch_popup?v=tPg1ZMiC9pA

Tommy_T
02-13-2011, 07:45 AM
These have been given to me for inspiration
http://www.robotshop.com/blog/roboplow-snowplow-robot-311
http://www.treehugger.com/files/2009/01/worlds-first-solar-powered-autonomous-snow-plow.php
http://dvice.com/archives/2007/02/roombalike_snowplow_robot_uses.php
http://hackaday.com/2010/02/01/snow-blower-robot/
http://www.motherearthnews.com/Do-It-Yourself/DIY-Human-Powered-Snowplow.aspx
http://conceptpop.com/radio-controlled-robotic-snow-plow

Didi you see this one?
jdolecki, sweet peace of work, that Roboplow. But.


Tommy

Tommy_T
02-21-2011, 07:05 AM
As the Mule gets heavier(added 200lb of sand as ballast) and the Mule gets farther away
from home (over 450ft), I get to thinking "what if", while I have programed it to stop if WiFi
is lost(ping the base Pc each second), and if the PC shuts down the drives do go into fault,
and the Mule has never runaway(yet this winter),as I start to venture farther it's harder to have that
warm&fuzzy feeling I love so much with all the what ifs.

So I added a remote Mule shutdown button.

I got a Cobra microTalk GMRS Walkie Talkie from Walmart that listed a 20 mile range(tested at 2 Miles
non-line of sight, Sweet!). I stopped at Staples and got one of them "Thats Easy" buttons (seemed cute)
which I wired to one of the Cobra's call buttons. From RadioShack I got a SPDT 5V micromini
relay and a 1000uf cap. the relay when energized sends the Mules drives into fault.

A long range remote warm and fuzzy feeling for under $50, is a sweet thing.

Tommy

Pabble
03-06-2011, 09:36 PM
Hi all, new here. Very good material, I like the Mule, it's cool and very advanced compared to my mower project. It's RC operated at present. I will be adding a camera and a Sabertooth 2x50 soon. I also plan to try to make my project a multitasting machine with autonomous operation. I've experimented with building my own motor driver but had too many problems blowing the mosfets. I will be looking @ the Ardupilot as it may be useful, anyway maybe I can post some useful info here.
Good job on the mule.

jdolecki
03-08-2011, 11:34 AM
Peep this out tommy just got off craigslist. Friendlly Robotics Mowbot.

Will take the cover off this weekend and post more pictures.

Tommy_T
03-10-2011, 06:31 PM
Sabertooth 2x50 soon
Pabble, I also would like to try a 2X50, I did try a 2X25 only because everyone was out of the 2X50's,
but after burning up two of them, which they replaced at no cost(other then shipping) I stayed with
a P&G drive I had. any way sweet work on your lawn mower.


Peep this out
Sweet find jdolecki!, one of them would be hours of fun to play with. If I had one now(in the winter) I'm
sure I would run the perimeter wire around my living room to test it out.

like both of you my mind is turning to lawn mowing again(stopped at three different places looking
at reel type mowers) in fact I must have been thinking this winter was done teaching me things, but
just the other day we got a little snow(3 to 4") I sent the Mule out at 290lb without a thought, but
soon had to return home to add more weight(added 140lb) because the snow was so wet.

Tommy

Pabble
03-14-2011, 06:20 PM
like both of you my mind is turning to lawn mowing again(stopped at three different places looking
at reel type mowers)
Tommy
Thanks,
Ebay has alot of reel mowers. Probably the gang style reel mower would be best since it is made to be towed. That's a good idea btw, I also will look into that style.

Have you had any experience with the Arduino and if so which do you prefer, the Arduino or the Phidget? I have some experience with the Arduino and I tend to like it, the price is very good compared to alot of microcontrollers out there.

My motor controller is due to be delivered tomorrow, I will be changing my sprockets out in order to speed it up a bit. I'm wanting a fast walk speed, currently it's a little too slow.

Tommy_T
03-15-2011, 06:40 AM
I also will look into that style.
Pabble
I'v used a standard rotary 24Vdc mower(Earthwise) on the Mule last fall, and
it was fast and simple to implement, but to get a +40" cut path I would need
about three of them which would increase the Mule's footprint too much, also
camera angles would need changing when going from snow plowing to mowing if
rotary type are used.
My hope is that three reel mowers could be mounted the same as the 50" snow
plow.

I found one of the units in picture below, it has a chain drive system for the blade
which would simplify motorizing(if needed, which I'm sure its going to)

I'm now testing a single 14" low cost reel mower.

With the wet ground now that most of the snow is gone, is an idea time to test
the Mule's 10" wide turf safe tires(without the chains) for lawn damage, and all
test so far are sweet, even while doing zero radius turns.


Arduino or the Phidget?
The Mule's on-board controller is an net-book PC, I have not tested any Arduino's
yet. I do have a few Phidgets I'v been testing but have not found a place for yet
due to limitations of the units or technologies.


Tommy

Pabble
03-17-2011, 06:37 AM
Very good Tommy T.

I received my 2x50 motor controller the other day and I am very impressed with it so far.

I ordered a Mow Pro 21" reel mower and I'm hoping I have the power to pull it. I've never used one so I don't know alot about them. I will tow it behind my current setup and see how well it does. If all goes well then I will design a new chasis and go from there.

Tommy is your bot remotely controlled or is it working autonomously?

I will post pictures as soon as I get everything together which maybe a month from now.

Tommy_T
03-18-2011, 06:43 AM
Tommy is your bot remotely controlled or is it working autonomously?
The Mule has four current modes it can operate in.

1) Wifi networked to PC in house for remote control with network camera(3) feedback.
2) Bluetooth wireless keyboard(Palm sized) for direct control of on-board PC
3) Wired joystick as backup when all else fails.
4) Programmable cut path, I do it once with Wifi or Bluetooth and record feedback
values(Velocity, Yaw) every 20msec for playback.

I'm still testing for best localization tools.
in my head I see http://www.havahartwireless.com/store/wireless-dog-fence/5144g
as being a sweet tool.

Lowest cost option seems to be on-board web cams for locating fixed targets.

Tommy

maleche
03-24-2011, 06:20 PM
Did anyone "master" the P&G drive controller?

I have been doing research on electric wheelchair controllers to modify for robotics projects. Information is really tight lipped!

Most all (at least newer) electric wheel chair controller use a protocol call "Multiple Master - Multiple Slave" (M3S). Google it and you will find that the controller has a lot of safety features built in, including joystick and command validations. The best idea is to hack the joystick and mimic commands or position control assoicated with the brand of wheelchair/controller.

Let's keep in touch!
Thanks!

Tommy_T
03-24-2011, 06:53 PM
Did anyone "master" the P&G drive controller?
maleche, I'm using the P&G VSI speed controller on the mule now, not
sure about the master part because I have not over come it's programed
acceleration/deceleration profiles. But I do like the drive, lots of safety
back ups.

Tommy

Pabble
03-28-2011, 08:40 PM
Here are a couple of pics. I tried the reel and it works great, does a good job on the lawn. I also attached a camera and transmitter so I can control it while sitting in my shop. The receiver is attached to 36" HDTV. There is a draw back in that I did suffer some motion sickness :( I will try to take some photos of what it looks like on TV. I have a dialup connection so uploading a video is out of the question. Maybe I can go to a coffee shop and upload there. All works well, I will work on a new design now and concentrate on autonomous operation. Keep in touch, don't let the thread die.

Tommy_T
03-29-2011, 12:09 PM
concentrate on autonomous operation.
Pabble, have you any idea how your going to deal with localization yet?


While I'm sure winter has not finished teaching or entertaining me yet I also have
been doing some mower testing.

I got one of the three test reel mowers temperately mounted on the Mule.

Tommy

Pabble
03-29-2011, 07:58 PM
Cool setup Tommy.


Pabble, have you any idea how your going to deal with localization yet?

Tommy

Not alot of thought yet but maybe using laser rangefinders for x,y + optical interupter to stay within a certain range and maybe sonar for object avoidance. It's certainly not going to be easy.
I don't believe GPS will work in a small area. I honestly don't think I will be able to make it work reliably but I'm going to try. I give myself about a year on the task. Alot to learn. Maybe one can use GPS to find itself and work from there. I refuse to use any buried wire. I have 3 acres to mow :happy: Anyway this is just for fun anyway. What are your thoughts?

Tommy_T
03-29-2011, 10:18 PM
What are your thoughts?
I'm thinking wireless dog fences that uses time of flight technology.

But if these reel mowers could be used it may be possible to mow at night and use light
beacons(could be IR) and cameras for localization. last fall I tested a 24Vdc rotary mower
on the Mule but the noise was as much if not more then a gas engine, no way I could get
away with mowing at night with one or more of them.

Tommy

Pabble
04-01-2011, 06:43 AM
But if these reel mowers could be used it may be possible to mow at night and use light
beacons(could be IR) and cameras for localization.

Tommy

Good idea Tommy, I've just ordered a sonar device and IR sensor to play with. Not sure how I will use them exactly yet.
I will probably use pic microcontrollers and the Atmega328, time will tell, lots to learn since I'm new to alot of this. I do like the night time idea.

parallax
04-01-2011, 10:17 AM
Hi Tommy_T,

I have a quick question for you:

Correct me if I am wrong, but I believe you are controlling the Mule through a wireless home network. Do you find when you are operating the Mule in a really bad snow storm that your connection to the robot suffers significantly? Also, what kind of usable range are you getting from your connection (both in clear weather and in a blizzard)?

Thanks!

Tommy_T
04-01-2011, 03:48 PM
Do you find when you are operating the Mule in a really bad snow storm that your connection to the robot suffers significantly?
parallax
I have the Mule's wireless router(NetGear) mounted outside, and yes I have had connection
issues during heavy snow falls, which I figured was caused by the router being covered with
snow(router sitting on roof of house), after I clear the router of snow I'm back to plowing.


what kind of usable range are you getting from your connection (both in clear weather and in a blizzard)?
Can't give a good answer to that question, because all my wireless range tests have been
done without heavy snow fall.

As is with the router outside(on the roof) the Mule's PC to router range is 450ft, Mule's network
cameras to route range is 300ft.

Tommy

parallax
04-01-2011, 05:25 PM
Thanks for your quick reply! :)

BTW, I am a big fan of your project. It's executed cleanly, has a well-defined purpose, and is simply awesome. Great work!

The reason why I'm asking about these ranges:

I have been in the early stages of designing a general purpose farm-bot for a close friend of mine's family. More like a feasibility test, actually. I'm seeing if some of the things they would like it to do are reasonable at their location. They would love to have a similar plowing/mowing functionality as your Mule if possible.

However I am hitting a range roadblock. The family's driveway is close to 450 yds long (more like a road than a driveway) and other areas of the farm are even further away. I have toyed with setting up repeaters down the length of it, but it seems like a logistical nightmare to try and setup/maintain. After hearing your experience with usable ranges via WiFi, I think I may have to explore alternate methods.

Just a thought~ signals in the 2.4GHz range are severely degraded when traveling through water. Have you ever noticed any performance hit on a rainy day?

Tommy_T
04-03-2011, 07:50 AM
I think I may have to explore alternate methods.
I agree

it seems the best option are not always the easiest. Wifi while being very easy
to incorporate into most any system, has a number of shortcomings in outdoors
applications.

I gave the Mule the processing power to do it's tasks without the need for me to
look over it's shoulders(network cameras), but because of limitations of the
available transducers or my shortsighted use of them all tests this winter have
been under Wifi remote control.

This week I'm pulling the Wifi cameras and start using the processing power I gave the
Mule to accomplish it's tasks(easier said then done).

Tommy

Stobs
04-06-2011, 03:29 PM
Is the signal inhibition being caused by direct contact of the snow? If so, encapsulating the router in a transmission transparent material may help? Something simple like a suitably sized plastic cake storage piece with cover comes to mind - some are made so that the cake can sit on the cover for serving. The cover can be secured to a separate platform for easy mounting/dismounting to the roof.

Tommy_T
04-15-2011, 09:18 AM
Got the other two test mower mounted, now to look at spring loading.

Tommy

Stobs
04-15-2011, 10:30 AM
So I guess my post didn't even warrant the courtesy of a reply? I thought it might be helpful and certainly didn't intend to waste our time.

parallax
04-15-2011, 11:36 AM
Sorry Stobs! No one means to offend you. I guess your post just slipped through the cracks.

To answer your question:

I'm reasonably sure that the cause of the signal inhibition that Tommy_T has commented on is caused by the encapsulation of the router by the snow and not direct contact. 2.4GHz signals degrade very fast when travelling through water and although snow is frozen, its essentially still just water molecules in a solid state. In this case, using a container like you described wouldn't help much. Good thinking, though!

Stobs
04-15-2011, 01:38 PM
Thank you very much for the reply parallax - although I'm confused as to why you replied instead of Tommy_T! ^.o

I sent my inquiry as an IM because I didn't want to post anything that could've been construed as inflammatory, but since I sent it to the wrong party I owe Tommy_T an apology for the faux pas and gratitude for passing the message on to you.

I've been following this thread pretty closely and have been inspired by its successes - I'm keeping a similar project in mind for a year or two down the road, as I become more familiar (and hopefully competent!) with robotics.

And thanks for the kind words, even though the idea wasn't really very helpful at all; being given the benefit of the doubt is appreciated! :}

PS: Well, let's make that two of a kind then. O.o I thought I'd sent the above post (#88) as an IM to Tommy_T, so explaining that may clear up some confusion I may have injected here. I hadn't seen that post up there until after I'd sent Tommy_T a "follow-up" IM and then refreshed the page. My additional apologies to you parallax and to the community at large.

Tommy_T
04-15-2011, 06:15 PM
Stobs, I'm thinking Wifi is not the answer for this project. yes it was easy to implement
giving me more time to work on weights,power and control issues the Mule's first winter.(I learned a lot)
But it is unreliable at distances greater then @300ft or non-line of sight of @200ft.
I gave the Mule the processing power to accomplish it's tasks, IMO it's time to use it.
Time to start thinking outside the box for ways to keep the Mule in it's box(my yard).

Tommy

Stobs
04-16-2011, 02:36 AM
I really don't know much about communications, but what about working with cell phones? They seem to work in any weather - well, if you believe the commercials anyway :} and some models have USB connections. The family plan that I belong to lets us upgrade our lines at two year intervals, depending on when we started service/last upgraded; might be able to make a contact at one or more of the local phone outlets and see if you can put up a wanted notice for someone's old phone? That wouldn't work that well with my service plan, but if yours is high/unlimited minutes and reasonable data rates it might be worth looking into.

Tommy_T
04-16-2011, 08:02 AM
but what about working with cell phones?
As is I have a USB 2G/3G aircard(for car's PC) with unlimited air time, but this august the mule
is going to my mom, she would say no thanks if it costs $60+ a month on top of the charging costs.
I'm also shy about connecting the Mule to the Net, all tests with Wifi have been with routers not
connected to the net.

I'm testing creative ways to use a webcam so the Mule can follow a programmed path.


Tommy

Stobs
04-18-2011, 01:49 AM
...if it costs $60+ a month...

Exactly why it wouldn't work for me either, at least not with my current plan.

Tommy_T
05-16-2011, 05:39 AM
Completed tests of friction drive Reel mowers on the Mule, and while it had it's advantages
it couldn't give repeatable results, too many things can stop the Reel from turning, which
does makes for a very safe(as mowers go) mowing deck, but requires human intervention
to remove object before it can continue. would work for gulf coarse greens, but not large
lawns with trees or bordering corn fields(like my test area). Also with six fixed wheels in
contact with the ground while mowing lots of energy is needed to maintain a straight cut
path.

Next testing electric motored conventional rotary mowers(I got one last fall)

Tommy

Pabble
05-22-2011, 09:00 AM
I agree with Tommy, the reel mowers are great as long as you clear the yard of limbs and such before you start mowing.

I have been experimenting on a small scale with the use of GPS. I have had some success but so far the accuracy is not there. I may purchase a more accurate module later if budget permits.

Something I have been running around in my mindseye is using object recognition and have the mower place cones or other objects at the end of each run. The object would be tracked keeping the mower inline with the object. When the mower reaches the object, it picks the object up and places it in the path of the second run. This process would require 2 objects for each end of the yard area. I have used Keyence Cameras with object recognition at work and they work really well. Not sure how well it would work with such a busy environment and with changing perspective.

Anyways I am on hold until the flood waters of the mighty Mississippi have subsided. I have not had water problems yet and probably will not but just in case I have most of my hardware stored in safe keeping until then.

Tommy_T
05-25-2011, 06:29 PM
I have been experimenting on a small scale with the use of GPS.
Pabble, I also have been testing a GPS(Phidgets), I can't use a digital compass to get
the Mule's bearing because of the EMF of the electric motors, both drive and 38" electric
mower deck, I hope to get that information from the GPS.


my mindseye is using object recognition and have the mower place cones or other objects at the end of each run.
Not a bad idea, but would try this first(seems simpler) http://www.petsbycsn.com/Loc8tor-LOC8TORPLUS-LKR1001.html?cv=



I duct taped a 38" electric mowing deck together.

Tommy

coppertubing
05-26-2011, 11:56 AM
I'm testing creative ways to use a webcam so the Mule can follow a programmed path.


Tommy

Tommy, take a look at Roborealm (http://www.roborealm.com/help/AVM_Navigator.php). It has the ability to process webcam video and use it to navigate a robot. There is a module available that will record the webcam video of a driven path and use it to drive the robot. The navigation module can also plot its own obstacle avoidance path.

BTW, I am also building a large rover based on a Jet 3 Ultra wheelchair and want to use it for lawn mowing. So I have been following your project with great interest. The mower I'm looking at is the Fiskars Momentum (http://www2.fiskars.com/Products/Yard-and-Garden/Reel-Mowers), which uses a flywheel to turn the blades, and is a push not pull reel mower.

Tommy_T
05-28-2011, 09:10 PM
I have been experimenting on a small scale with the use of GPS.
Pabble, A good way to test a GPS device would be to record the GPS data(say every second)
then overlay that data on say a Google Earth image.

In the example below the light colored line is the GPS data, I used a joystick to run the Mule
around the mowing area recording the Lat,Lon data to a file. As shown below trees do skew
the GPS values, while open spaces does a very good.


take a look at Roborealm.
coppertubing, I have yet to check out any of the ROS packages, all examples I'v seen are small
indoors robots, hard to see a connection with the Mule.


BTW, I am also building a large rover based on a Jet 3 Ultra wheelchair
If your not going to use the P&G motor drive and would like to unload it, let me know.

Tommy

Pabble
05-29-2011, 07:53 AM
Pabble, A good way to test a GPS device would be to record the GPS data(say every second)
then overlay that data on say a Google Earth image.

In the example below the light colored line is the GPS data, I used a joystick to run the Mule
around the mowing area recording the Lat,Lon data to a file. As shown below trees do skew
the GPS values, while open spaces does a very good.


Tommy

Very cool Tommy, I will have to experiment with that.

Were you driving the Mule by camera while gathering data? If so you seem to be getting a very good range and I would be very grateful to know what you are using for a transmitter/receiver. The best I can get by camera around buildings and such is roughly a couple of acres. I get a very good range in open field with no obstacles.
Mostly I enjoy mowing the yard on my riding mower but when it gets windy and dry with all the dust and pollen then my sinuses and eyes suffer. Thinking of modifying one of my motorcycle helmets to wear while mowing hehe:happy:
My Video receiver is hooked to a 32" LCD HDTV and I tend to get motion sickness if I drive by camera very long and mowing remotely gets very boring hence the search for autonomous operation.

Pabble
05-29-2011, 09:01 AM
I duct taped a 38" electric mowing deck together.

Tommy

Some creative use of Duct Tape, I like it:happy: Looks like two mowers side by side. Are you drawing power from the Mule? How long can you mow per charge?

Tommy_T
05-29-2011, 01:20 PM
Were you driving the Mule by camera while gathering data?
Pabble, No I was walking along with the Mule while recording the data. I pulled the
cameras off the Mule as soon as I figured the chances of snow was over. IMO the
cameras was slowing down implementation of autonomous operation(was a crutch IMO
because the cameras would never give me the range needed).without them I'm forced
to work on the sensors.

Video receiver is hooked to a 32" LCD HDTV and I tend to get motion sickness if I drive by camera very long
Last winter I could spend over three hours running the Mule by camera, I installed wide angle
lens on all the cameras, that may help.

I like it Looks like two mowers side by side
Thats it, two 20" mowers pivoted 25deg so they overlap with no gap.

Are you drawing power from the Mule?
Yes, I removed the batteries that came with the mowers(20Ah).

How long can you mow per charge?
The Mule can mow for 1.5 hours with the current batteries, I got room for 4 more car
on the Mule when needed(right now I have steel weights in place of those missing batteries).
seems the Mule needs to weigh 500lb for both plowing snow and mowing.

Tommy

coppertubing
05-30-2011, 07:03 AM
I have yet to check out any of the ROS packages, all examples I'v seen are small indoors robots, hard to see a connection with the Mule.

If your not going to use the P&G motor drive and would like to unload it, let me know.
Tommy

Roborealm would be suitable for any size rover that uses a PC for its brains. There are modules for Sabertooth motor controllers (I'm using a 2x25), Phidgets sensors and servo controllers, GPS, and lots more. It makes it very easy to coordinate servos, sensors and motors to provide autonomous operation to your robot. I don't think GPS by itself will allow your mule to navigate accurately enough. You're going to need some kind of vision processing, and that's what Roborealm can do.

No, I won't be using the P&G so make me an offer.

Tommy_T
05-30-2011, 08:02 AM
You're going to need some kind of vision processing
coppertubing, You may be right, but I do have try one other idea thats floating in my head(beacons).

The idea...
The absolute position senor is the beacons, but it limited to only four of them, and it takes up to five
seconds to get a good position fix. to over come the four beacon limit the GPS is used, because it can
track the Mule to within 20ft,that position is used to determined which four to use(my house's four
beacons or my mom's four beacons). The Yaw sensor is used to overcome the five second limitation
of the beacons, the Yaw sensor can track the Mule to within ~.1 inch and .005 deg. at mowing speeds
and uses this information in between beacon updates to help keep the Mule on coarse.

I'm thinking because the Mule has to operate in rain, snow, fog, day, night. implementing a vision
navigation system would be tough.


I won't be using the P&G so make me an offer.
does it have the connectors in the picture below? and work?. is so, I'd try $50 + shipping

Tommy

coppertubing
05-31-2011, 12:10 PM
Good point about the vision processing in all weather conditions. Although I haven't tried it, it seems like Roborealm can do all manner of video processing, which may allow it to work in those conditions. I know it can track a laser dot, and it has a module for the Kinect which can use infrared cameras for obstacle avoidance. Once I get to that stage, I'll see what it can handle.

As for the controller, your plug looks like it is for the Jet 3 - this one (http://www.monsterscooterparts.com/4-key-50-amp-vsi-joystick-controller-right-angle.html). Mine is the Jet 3 Ultra. Don't know why they're different, but this (http://www.monsterscooterparts.com/4-key-50-amp-vsi-joystick-controller-flying-leads.html) is the controller for it. Since they go for $600 new, I guess I'll put it up on ebay.

Tommy_T
06-01-2011, 08:10 PM
I guess I'll put it up on ebay.
coppertubing, if you get no bidders keep me in mind, I do have a sabertooth 2X25(Never used) That I would trade.

Tommy

Tommy_T
06-26-2011, 06:11 AM
Mule's first try at mowing in a confined area in CNC mode


http://www.youtube.com/watch?v=-9qfBXX8_Rg



Tommy

Tommy_T
09-23-2011, 05:32 AM
Tasks it most perform
1) carry payload of 150lb (at least 2 bags of potting soil)
2) mow grass (both manually(remote control) and autonomously(with supervision))
3) clear snow for drive and walkways manually(remote control)
4) simple to control (even my 75yr old mother can use in her garden)

While I expect years of tinkering ,fun and use of the Mule, this project is complete.

time for the next project.

Tommy

Gertlex
09-23-2011, 12:50 PM
Props to you for this project, Tommy (I had followed you on SoR, but was delighted to stumble upon the lengthy thread here :) )

Tommy_T
04-01-2012, 06:39 AM
time for the next project.
I got ahead of myself.

While yes the mower deck does cut grass, it sucks!. very under powered, very noisy and too big.

my first try was using three reel mowers in their stock friction drive configuration, I'd pick them
up when making turns,then lower them down to mow. this setup cut very nice, was small and
quite, but small sticks, corn cobs or barbie dolls would stop the mower causing the mower's
wheels to slip.

Next I tried stock battery powered electric rotary style mowers(Earthwise cordless 24vdc)
but as stated above, they suck for my application.

So my next option seems to be putting motors and casters on the reel style mowers.

Tommy

tician
04-01-2012, 07:08 AM
Ever try adding a small grating in front of the reel mowers to catch debris and push it to the side (think cattle catcher on a steam locomotive)? Or maybe an auger, like on the front of a combine, to direct debris to the sides? Or invert the auger to direct debris to a small conveyor belt in the center to collect debris into a container (pine cones friggin' hurt when they make it out from under a rotary lawnmower)? Or a 'jamming' gripper on a small-ish arm to grab debris sighted by a camera observing its path (collect or throw away)?

Can you tell I've wanted to build a robotic lawnmower? I had once considered using a reciprocating-type clipper akin to a hedge trimmer, but that seems to have the worst parts of both a reel and rotary mower (still needs some sort of protection like a reel mower and a power source like a rotary mower).

Tommy_T
04-01-2012, 07:24 AM
Ever try adding a small grating in front of the reel mowers to catch debris and push it to the side (think cattle catcher on a steam locomotive)?
tician, good idea!
I have not tried so far, one reason a rotary style mower cut so good is it sucks the grass up as it's cutting,
a rake in front of a reel mower may help stand the grass up for a better cut, and help keep the barbie dolls
out of the blades.

Tommy

Tommy_T
11-04-2012, 05:44 PM
Would seem I have a design problem.

in last two years I'v broken each of the drive axles once, the axle is 1.000" dia. steel turned to .800" dia. for the
bearing, each failure occurred at this turned surface. the first was in the middle between the bearings, yesterday
it was the other side at the output edge of the bearings.

I'll change the bearings to 1.000" ID dia. and use retaining rings, in place of the turned .800" shoulder.

Tommy

Th232
11-04-2012, 06:37 PM
You've already got a fix lined up, but what was the corner radius at the shoulder? Sharp internal corners are great stress concentrators.

The first failure sounds interesting though, did you figure out a cause?

tician
11-04-2012, 07:51 PM
Any sort of surface defect on a shaft will become a stress concentration point, and not just the shoulder - although the shoulder radius is an extremely important parameter during design. Get any sort of wear in one location of the shaft, and odds are that will be where it fails.

What really stands out to me as a likely cause of failure is directly supporting the wheel with the output shaft. Shafts are intended to withstand the large shear stress of torsion, and having the wheel cantilevered so far out on the shaft will cause significant bending (tension/compression) stress that they are not so capable of withstanding.

Another question to ask is: what type of steel were the shafts? Because not all steel is created equal.

Tommy_T
11-04-2012, 08:36 PM
The first failure sounds interesting though, did you figure out a cause?
Th232, it seems when I made the bearing blocks I didn't make sure the bearings were fully seated
(press fit), one bearing was cocked a little, over time it caused the axle fail.

but what was the corner radius at the shoulder?
.020" is the corner radius the failure happened @.090" from the corner radius.



what type of steel were the shafts? Because not all steel is created equal.
tician, the shafts used were 1045 steel with a hardness of brinell 150(Rockwell 80).

Get any sort of wear in one location of the shaft, and odds are that will be where it fails.
when they were assembled there was a slip fit between the bearings and the shaft, now there seems to be .012" over on the outside bearing.

Tommy

Tommy_T
11-05-2012, 08:44 PM
What really stands out to me as a likely cause of failure is directly supporting the wheel with the output shaft.
The reason I don't suspect the shaft steel or wheel placement.
The wheel hub shoulder is .670" dia. , the bearing shoulder is .800" dia.
none of the failures occurred at the smallest dia.(wheel hub).

I believe all the failures are a result of the bearings, or bearing fit/installation.

on a side note:
if you gotta cut grass with batteries the reel style seems to work best.


Tommy

Tommy_T
11-08-2012, 06:19 AM
What really stands out to me as a likely cause of failure is directly supporting the wheel with the output shaft.
tician, I'm being to see it(I get slower as I get older).

each of the failures showed excess wear on the shaft at outside bearing, with no measurable wear on the inside
bearing. the bearings are rated at 2900lb, even with 140lb of sand bags(when wet heavy snow) the load on the
wheel is under 350lb, but because I'm powering the wheel(motor sprocket) on the same side as the load carrying
wheel it is causing excess wear at that bearing(outside bearing).

I increased the dia. at that bearing from .800" to 1.00" and I'm beginning to see all I did was postpone the next failure.

A better fix would be to make room to move the motor sprocket to the other side of the spindle(inside bearing side)
in hopes of evening out the wear between inside and outside bearing surfaces.

Tommy

tician
11-08-2012, 08:31 AM
Honestly, this thread has been stuck in my head since I first read about the shaft failure. Shortening the shaft so that the wheels are closer to the frame should help increase the life a bit as it should decrease the bending stress a bit (the bending forces are what causes the bearing to eat into the shaft). Ideally there would be a space frame of some sort to connect the wheel to the bot's frame (to support the weight and forward forces) instead of using the shaft to do it all. This would permit a smaller diameter shaft since it would no longer be supporting the weight of the bot, just the torque between the drive sprocket and the wheels (with a not so small radial force caused by the drive sprocket). If I have time this weekend, I may break out the mechanical engineering textbooks and notebooks and do the math (mostly been EE the last while, so the ME has suffered).

If I am thinking correctly, the axle can be approximated as a cantilever beam. The wheel end of the shaft has an upward reaction force equal to the weight of the bot applied at the bearings, the forward reaction force caused by the wheel (due to the torque applying a force at the ground via the wheel), and the reaction to the applied torque. The wheel end is unconstrained (free to rotate and translate in all dimensions). There will be a very small bending moment at the end of the shaft when the weight of the bot causes the wheel to canter inward (caused by the reaction force of the weight not being applied directly to the end of the shaft, but slightly further out), but given the width and conformal nature of the pneumatic tires you are using, I think it should be safe to assume this bending moment is negligible.

The bearing end of the shaft is fixed in translation three dimensions and fixed in rotation in two dimensions. It will have the downward force of the bot at the bearing and a backward reaction force to counter the forward force from the wheel end. Because the bearing end is fixed in 5 degrees of freedom, there will be reaction moments to counter the bending moments caused by the two forces at the wheel end (the upward reaction force to the weight and the forward force to drive the bot). The longer the shaft and/or the larger the reaction forces at the wheel, then the larger these reaction moments at the wheel (higher stress) and the larger the deflection of the wheel end (the edge of the bearing will bite into the shaft as it deflects). This is of course ignoring the torque and reaction force from the drive sprocket, but its location will affect where these forces are found.

Tommy_T
11-12-2012, 05:49 AM
Shortening the shaft so that the wheels are closer to the frame should help increase the life a bit
tician, because I'm using a 42" wide snow plow, with two wheeled prepositional steering, shortening the wheelbase would have
an adverse effect on controlling the plow's path.

the surface for the bearings is 2.75" wide, the ball bearing surface used is 0.5"(1.0" total for both bearings), if I used roller bearings
in place of the ball bearings, it would increase the surface used and in turn reduce the wear at them locations.

lucky for me when the shaft failed it was near my place(50ft), if it was further away recovering the device would have been very
difficult because of the weight of the device. I need to come up with a recovery option(other then calling to tow truck).
maybe something like picture below.

Tommy

Tommy_T
02-03-2013, 07:55 AM
https://www.youtube.com/watch?v=RV-4XTY2dXQ


Tommy

Tommy_T
11-13-2014, 06:45 AM
The Mule lost half it's duct tape and went to a 54" cut path

Tommy

jwatte
11-13-2014, 11:55 AM
That is so awesome! Wish I had had that when growing up :-)

tician
11-13-2014, 11:27 PM
Very nice. I've still not gotten around to building myself a little outdoor rover with spinning sticks of terror made from 15mil full hard 301-SS and 50mil 6061-Al plates brazed together. Theory (based a bit on rodent teeth) goes that the thicker, softer aluminum provides mechanical support for the thinner, harder steel while also wearing down faster to keep a sharp, thin steel cutting edge on a thick stiff blade.

Any more broken drive shafts? What I was unable to describe so long ago was 'build a proper wheel hub', so that the bearings and support structure/suspension would be almost directly mated to the rim, as happens in most road vehicles, which would keep the length of the unsupported/cantilevered shaft very short.

Tommy_T
11-14-2014, 05:57 AM
Wish I had had that when growing up :-)
jwatte (http://forums.trossenrobotics.com/member.php?7432-jwatte), your never to old to have some fun, even while doing some of these repetitive tasks(mowing,plowing).



Any more broken drive shafts?
tician (http://forums.trossenrobotics.com/member.php?4806-tician) , so far, so good.


which would keep the length of the unsupported/cantilevered shaft very short.
I also see this as a problem with my original design, the problem becomes more pronounced when
plowing snow because of the 200lb of sand I add. when the next shaft fails I'l re-design it.


Tommy

jwatte
11-14-2014, 10:46 AM
jwatte, your never to old to have some fun, even while doing some of these repetitive tasks(mowing,plowing).

True -- although these days, the chickens pick the back yard clean, and I live in a place where yards are small and it never snows...
I have enough projects anyway! :-)

Tommy_T
11-29-2015, 08:20 AM
while the Original Design offered some advantages(more room for batteries)
, cost savings(used bearings and wheel hubs I had) and kept the center of gravity low.
but the shortcomings have forced me to redesign the drive system.

6310

Gertlex
11-30-2015, 10:51 AM
Going to have the new design implemented in time for heavy snow?

jwatte
11-30-2015, 01:57 PM
interesting!

Does the axle nub that sticks out about 1.5" beyond the sprocket go into the bearing? Is that enough to bear the load, or is there some other suspension?

Tommy_T
11-30-2015, 08:24 PM
Going to have the new design implemented in time for heavy snow?
Gertlex (http://forums.trossenrobotics.com/member.php?5786-Gertlex), NOAA is saying this is an El NiƱo year, so I'm hoping that will buy me some time. because
it's not only the drive system that is getting changed. I'm adding a front loading option.
6315

Tommy_T
11-30-2015, 08:40 PM
Does the axle nub that sticks out about 1.5" beyond the sprocket go into the bearing?
jwatte (http://forums.trossenrobotics.com/member.php?7432-jwatte) , there is no other suspension, even with the Mule's weight of 320lb and the 280lb of sandbags added
when plowing snow the bearing have held up for fours years.

all the failures happened at a turned down shoulder, the new design has no shoulders(1" keyed shaft the full length)


6316

Tommy_T
01-26-2018, 09:08 AM
71317132713371347135713671377138

jwatte
01-26-2018, 08:53 PM
Mmmm, steel!
(Nice Bridgeport conversion, too!)

Are you using lead acid batteries for cost, or do they work better than lithium in cold weather?
(I imagine the batteries would warm themselves while running, though?)

Tommy_T
01-26-2018, 09:51 PM
Are you using lead acid batteries for cost
jwatte, Using Lead acid Batteries for cost and weight, I have two commercial grade batteries
19"x 8"x 8" that give me about 100lb each, then five 60Ah deep cycle batteries that give me
about 60lb each. all but one of the batteries are configured for 24v for the drives, one deep cycle
battery is used for controls, cameras, and lights.

when this design is done(i'm very slow) it will have four commercial batteries and eight 60Ah batteries.
which should give it close to 1200lb of weigh on the four wheels. that should be enough to push my 50"
plow through 12" of snow.

7140

Tommy_T
01-27-2018, 05:42 AM
going to have this type of setup(someday)

7141

when I made the motor brackets, I made all four of them

7142

tician
01-28-2018, 03:25 AM
Was there any particular reason for using the motor mounting plates as the central structural element of the new design? It would be much stronger and more reliable to replace the two short bars attaching the casters (and other two bars on the battery/plow side) to the motor mounts with longer, continuous bars extending the entire length of the bot and then mount everything to those bars. The battery holder and plow attachment section of the frame uses additional reinforcement to bolt to both ends of the motor mounting plates which helps a bit in distributing forces, but the casters just hang off the end of the motor mount plates with only one bolt per side. Making the casters cantilevered like that with the only bolt so close to the edge of the motor mounting plate will put a lot of stress on that area and risk the bolts being torn out of the motor mounting plate.

Tommy_T
01-28-2018, 05:47 AM
Was there any particular reason for using the motor mounting plates as the central structural element of the new design?
tician, the mule has multiple jobs to do, mowing grass,hauling stuff,plowing snow and collecting dead leaves. most of it's tasks can only
be done with two wheel drive(four wheel drive would tare up the lawn), the connecting bolts for the attachments are 1/2"-13 bolts.

7143

the snow plow with the two front wheels is an attachment.
7144

Tommy_T
01-28-2018, 06:12 AM
risk the bolts being torn out of the motor mounting plate.
tician, the motor brackets are .625" hardened steel, and the bolts are 1/2"-13 grade 8.

made blue chips when cutting the 1/2" holes at 300rpm in the brackets(very hard steel).

tician
01-28-2018, 06:49 AM
posted without refreshing:

What I was getting at is: three short bars bolted together at one or two points within a few thicknesses of their overlapping edges is much weaker than a single continuous bar. Even butt welding them together would be far superior to bolting like that. Extending the short bars under the entire length of the motor mounts so that bolts can be used at both ends will greatly reduce the stress experienced by the mounting plates, bars, and bolts. With just the one bolt connecting the caster bars at the end, the bolt is subjected to significant shear stress any time the bars are subjected to bending (batteries not properly balanced over pneumatic wheels, plow being forced upwards by ground/snow, extra weight added between casters and pneumatic wheels, etc.). With longer bars secured at both ends of the mounting plates, the bolts experience very little shear stress which makes them much less likely to fail or to tear out of the mounting plates or caster bars.

Imagine attaching two halves of a truck together with a short thick plate (<3" long) and just a couple bolts in the bottom flat of the frame rails located only an inch or so away from the joint - it will have essentially no resistance to bending and will very quickly tear the bolts out of the frame rail.
Using a much longer plate with regularly spaced bolts attaching up to a foot or so from the joint will greatly reduce the chance of the bolts shearing or tearing out, but does not help much in overall strength because of the small area moment of inertia of flat plate versus angle/channel/tube. Adding additional plate and bolts to the top flat of the frame rails significantly increases its strength and stiffness because the top and bottom are spaced by the height of the web to greatly increase the area moment of inertia.

Tommy_T
01-28-2018, 07:04 AM
the bolts experience very little shear stress which makes them much less likely to fail or to tear out of the mounting plates or caster bars.
tician, I wish I could apply the forces needed to cause the 1/2"-13 bolts to fail.

jdolecki
01-28-2018, 07:32 AM
I like them wheelchair motors for projects.


https://m.youtube.com/watch?v=nsiwWWMe-ZQ

Tommy_T
01-28-2018, 07:52 AM
7145
working on cameras

Tommy_T
01-28-2018, 07:57 AM
I like them wheelchair motors for projects.
they are sweet motors, I have some with factory encoders in them.

jwatte
01-28-2018, 11:18 AM
I like the light mount. Seems like it should get enough distance to give a more even spread than if it was just placed in front like headlights?

jwatte
01-28-2018, 11:37 AM
I think Tician's point is that forces, over time, may fatigue the metal when all the stress is concentrated. Building a "chassis" of two long bars, and bolting things onto that, would generally distribute the stresses better. If stresses aren't big enough, then it kind-of doesn't matter, which seems to be your assessment?

I have no idea whether your mule is actually close to a critical point or safely designed, I'm just interesting in running the numbers pointed out by Tician.

I looked up 1/2" steel bolts. Safe working load for a 1/2" bolt (grade 2/5/8) is 940 pounds shear, 760 pounds tensile. (Catastrophic failure, i e immedite breakage, load is about 10-20x higher, depending on grade.) Will your bot weigh 760 pounds or more? Will it rock left/right such that weight is unevenly balanced? Will it get stuck and apply more torque, or bump into uneven terrain so the load is increased by inertia? If so, 1/2" bolts may fail over time. The table I used: http://www.rdfasteners.com/pdf/boltstrength.pdf


"hardened steel"


If durability under bending stress is what you want, hardened will crack sooner than less hard steel. It of course depends on the specific loads, but too much carbon makes it brittle. There is also tempering where you harden, then "back off" by relaxing in medium heat for a bit, which gives a better trade-off between brittle and touch. Maybe that's what you're using?

Gertlex
01-28-2018, 11:46 AM
I bet it will survive the few years before his next iteration! :D

Looking marvelous as always, Tommy!

Tommy_T
01-28-2018, 11:46 AM
I like the light mount.
jwatte, a work in progress, the parts I have done so far are the snow plowing attachment, but I want the lighting and cameras systems
on the main unit(back section not made yet).

Tommy_T
01-28-2018, 12:21 PM
the best I can do is 300lb per tire.


If I had to question something, it would be the main axle brackets.
but the last frame used the same setup and held for four years.

7146

Tommy_T
11-05-2018, 04:59 PM
7337

Sucks to be me.
they are talking about snow in the forecast, yet the snow bucket is still not installed.

Tommy_T
11-06-2018, 07:12 AM
7338
It seems I'm the reason for the slow down.

over thinking it.

jwatte
11-06-2018, 11:42 AM
yet the snow bucket is still not installed

Well, who's fault is that?


It seems I'm the reason for the slow down

Oh, right then.

What fun would it be without overthinking? :-)

Else you would just weld a 3/8" steel plate on front at a diagonal, that would plow just fine as long as you keep up when it's coming down. No fun in that. (Other than saving the work of doing the plowing manually.)

Tommy_T
11-11-2018, 05:48 AM
What fun would it be without overthinking? :-)
jwatte, I'm still scratching my head about what type drive to use to lift the bucket.
I have a ballscrew from a bridgeport mill, but with a pitch of .200" and a motor with 180rpm
it would take some time to lift the bucket(@20sec. with 4 to 1 gearing of the gearbox).

if I went to a chain drive, I could get it down to 5sec.

jwatte
11-11-2018, 12:00 PM
Also, could you bolt lifting arms to the side, to give you a longer lever? Put the pivot point at the back of the bot, lift somewhere in the middle, and put the bucket in front, for additional speed gain (and, of course, torque loss, so that counteracts your 4:1 gearbox ...)
Really, just add a harder/better/faster/stronger motor and call it good, I guess? :-D

I think this is why professional gear uses hydraulics... Build high pressure in a storage tank, use it when needed to actuate with high forces quickly, as long as you're OK with some mush in the system and some lag in the control loop.

Also, how far do you really need to lift the bucket? You don't really need to lift it much more than the regular ground clearance of the 'bot, right?

Tommy_T
11-12-2018, 05:05 AM
how far do you really need to lift the bucket?
jwatte, with the way the bucket was made I have to lift it 18" just to dump it.
I'm thinking of lifting a total of 34".


I think this is why professional gear uses hydraulics.
jwatte, this is where the overthinking come in...
hydraulics would be a easy to implement setup, I can get stuff at farm&fleet to do the job.
but, I need to start playing at 5 am so I can still get some work done that day, and with 30
neighbors that would be in range of the sounds the hydraulic pump, they may not let me play
in their space at that time. (that would suck!)

I have the same issue with electric winches.(too loud)

jwatte
11-12-2018, 03:31 PM
30 neighbors that would be in range of the sounds the hydraulic pump

My neighbors don't worry about their lawn crews using weed trimmers at 6am, soo ....
Buy a shotgun, ignore the neighbors? :-D

Tommy_T
11-18-2018, 06:57 AM
for the first try, I'm going with a #50 chain for the bucket lift and bucket dump drives systems.
7341


I'm going to have the frame welded together this week.

baby steps.

jwatte
11-18-2018, 08:20 PM
Ooh, those look like linear guides! That is, indeed, overkill ;-)

Tommy_T
11-19-2018, 04:52 AM
Ooh, those look like linear guides! That is, indeed, overkill ;-)
jwatte, have to agree with you on that one, but it should be a very quiet lift.

the motors I planed to use for the lift&dump systems were motors I had
used a few years ago for an electric bike project(very fun project).
7342

but, it seems I removed the electric brakes from them(crap!)
and for the lift& dump systems brakes are needed.

back to ebay.

Tommy_T
11-19-2018, 06:17 AM
when I started the mule project for convenience I had two battery groups,
12vdc and 24vdc with two different charging systems.

the 12vdc for PC , cameras and lighting, and 24vdc for the motor drives.

this year all batteries are going to be in one group, 24vdc.

(4) 12vdc 100ah batteries.

7343

I'm also removing the PC(in the mule) and replacing with 2 Arduino Nano,
and replacing the wifi control communications with an Xbee.


while I should have some fixed 24vdc to 12vdc/5vdc regulators show up
this week, I'm still installing a 24vdc to 110vac inverter in case I need to
run an air compressor,110vac lighting or heater.

Tommy_T
11-19-2018, 09:38 AM
the only time I've had Arduino's lock up on me are when
I have serial port conflicts, so even with using 2 Arduinos(one is for safety checks)
I'm going to use I2c 16bit DAC(0-5vdc) for controlling all the drives, I2c 16bit ADC(0-5vdc)
for feedback.

7344

jwatte
11-19-2018, 12:28 PM
Are those Teensy 2 boards on the sides? Or some Arduino Leonardo clones, perhaps?

Tommy_T
11-19-2018, 01:24 PM
Are those Teensy 2 boards on the sides?
jwatte, they are Arduino Nano V3.1 boards

https://www.mouser.com/ProductDetail/Gravitech/ARD-NANO30NP?qs=sGAEpiMZZMvq007EO%252bXAYdh8vxKmOPAO

jwatte
11-19-2018, 10:43 PM
Ah, yes, and you even said so in your post!

Tommy_T
11-21-2018, 07:08 AM
While waiting on parts for the bucket build I should think about
rebuilding the current handheld mule remote controller.

It's in a very sad shape.

7346

Tommy_T
11-21-2018, 04:21 PM
lucky for me, I had someone else weld the frame for me.
and it turned out very sweet!.
(if I did it, even using cold rolled steel it would have been spaghetti.)

7347

plan A
7348
plan B

7349

Tommy_T
11-22-2018, 07:11 PM
Baby steps.
7350

7351

7352

7353

Tommy_T
11-23-2018, 10:44 AM
baby steps.

7354

7355

jwatte
11-23-2018, 08:21 PM
Did you cut that circular pocket on a manual mill without a rotary table? Or are there stepper motors somwhere I'm not seeing them? :-D

Tommy_T
11-24-2018, 07:00 AM
Did you cut that circular pocket on a manual mill without a rotary table?
Jwatte, that's one of the things that makes the 1.5 hour drive(each way) to the office worth
the drive, the Mill has a conversational control on it(very sweet!), a lathe, surface grinder,
and Steel in the stock rack(life is good).

the ability to mill bearing seats or turn snap ring grooves comes in very handy with this type project.
7358

7356

7357

Tommy_T
11-24-2018, 08:19 AM
I only have a single axis motor drive sitting around(sabertooth 50), and
I can't see a need to lift and dumping at the same time. so I got
a 80A DPDT 24vdc relay to switch between motors(lift/dump) using
the single sabertooth motor Drive.

to simplify the first setup, I'm going to have very basic controls for the lift/dump.

(2) toggle switches
(1) momentary push button

one toggle switch for Up/Down for lift
one toggle switch for Up/Dump for bucket
the momentary switch is an enable button.

I have (4) 5vdc NPN inductive prox switches for each end of travels.

jwatte
11-24-2018, 01:22 PM
Sounds like a simple way to get things going with what you have in the parts bin :-)

Although I wonder if you couldn't just drive it all with relays, cheaper than the motor controller, if you don't need PWM...

Tommy_T
11-24-2018, 03:04 PM
Although I wonder if you couldn't just drive it all with relays, cheaper than the motor controller,
jwatte, while the 80A relays are cheap, the solid state relays needed for the arduino to control them are not, and
I don't have a lot of them in my parts bin. because I have the sabertooth already that is the cheapest way to go.

there's also the gearing issue, the lifting chain sprockets are #50 13 teeth @3" dia., they are on a 1" shaft with
a drive sprocket #40 30 teeth @5" dia. , then the motor has #40 9 teeth @1.5" dia.

the motors are 1000W 180rpm.

I'm going to need the speed controller to get the right lifting and dumping speeds right.

Tommy_T
11-24-2018, 05:07 PM
I was thinking of using this SPST 300A 24Vdc relay for the Drive enable relay.
It was listed as continuous duty, but still gets very hot after prolonged use.
and it draws .5amps

7359

this is the new remote controller enclosure(I think)

7360

tician
11-24-2018, 08:05 PM
How hot is hot? What is the maximum running current of the entire drive system?

Tommy_T
11-24-2018, 09:05 PM
How hot is hot?
tician, too hot to touch, that was with no load.

Just relay connected to 24vdc battery over night.

Tommy_T
11-25-2018, 05:21 AM
two of these in series should give me a warm&fuzzy for a Drive enable relay(s).

7361

two of them should draw .400 Amps (coil listed as 60 ohm)

Tommy_T
11-25-2018, 07:14 AM
baby steps.
which sucks because we got 6" of snow on way.

7362

tician
11-25-2018, 12:11 PM
two of these in series should give me a warm&fuzzy for a Drive enable relay(s).

two of them should draw .400 Amps (coil listed as 60 ohm)
Two 60 Ohm coils in series would be 120 Ohm. 24V / 120 Ohm == 0.2A and ~4.8W of power (most of it as heat once the relay has been closed). 2.4W in a small plastic package might not be much of an improvement compared to 12W in a heavy metal enclosure that is supposed to be bolted to a metal chassis (heat sink).

jwatte
11-25-2018, 01:28 PM
Cost saving tip: You can drive the coils of the 80A relays with a simple MOSFET from the Arduino!

The BS170 turns on at about 2V gate voltage, and is good up to 500 mA coil current depending on specific package/cooling. You could also use a much higher rated MOSFET with logic level gate, like AOTF2618L or whatever.

Anyway, if you need speed control, then relays are out anyway. Just thought I'd mention this easy way to do it, in case this threads shows up on Google sometime.

7366

Tommy_T
11-25-2018, 07:31 PM
Two 60 Ohm coils in series would be 120 Ohm.
tician, my bad. I'm going to be running the load output contacts in series.
that way if the contacts stick on one of relays the other can still drop the drive voltage
in case of emergency.

my drive power fuse is 100A. the relay is rated as 120A, too close for a warm&fuzzy feeling
but, two in series could.

Tommy_T
11-25-2018, 07:54 PM
Cost saving tip: You can drive the coils of the 80A relays with a simple MOSFET from the Arduino!
jwatte, very good advice.

I started using EATON solid state relays 15yrs ago for work, and over the years have found them to be
very reliable, but not cheap @$36.00 for the 15A units, @$26.00 2A units.

I also like using them because they isolate the 5vdc(control voltage) from the 24vdc(load voltage) in case of failure.

7367

tician
11-26-2018, 09:37 AM
Mechanical relay ratings are mostly about thermal limits of the contacts and wiring, and not about welding itself closed. Since a relay failing closed is most likely to happen during the sparking current surge at turn on (arc welding the contacts together), it would be far better to just add a proper pre-charge circuit to eliminate that sparking. A smaller ~10A relay and a low value, multi-watt resistor (e.g. 100 Ohm / 5W) connected from the battery to the load to slowly bring the motor drivers up to ~20V before turning on the main relay/contactor will largely eliminate the risk of the main relay/contactor failing closed.

Tommy_T
11-26-2018, 10:21 AM
it would be far better to just add a proper pre-charge circuit to eliminate that sparking.
tician, I agree, something like a RC snubber would add to the warm&fuzzy feeling.

jwatte
11-26-2018, 11:29 AM
If the motor controller isn't running, then the current during close is negligible (unless it has really big/low-ESR capacitors.)
You can also pre-charge with a 10 kOhm resistor in parallel, but really, not closing the contact straight into load is the best solution :-)
(If you use raw relays without a controller, you don't have that opportunity.)

Tommy_T
11-26-2018, 04:51 PM
baby steps.

7372

7371

I should have the remote controller done by time the lift is ready.

when this mod. is complete there should be 3 sabertooth 2x60 speed controllers,
and I found an extra 4 channel thermocouple board (spi) so it would be nice to
monitor the drive temperatures on the PC software control screen.

7373

Tommy_T
11-27-2018, 05:30 AM
mother nature must be checking in on this topic, 20 miles south of me got 10" of snow this week.
she dropped none on me.


I was thinking of using 2 Arduino Nano's for controlling the mule, but I got intermittent results
using the software serial on the Nano at 115200 baud. "SoftwareSerial mySerial(9, 10); // RX, TX"
not sure if it's some type of conflict(maybe spi), but because I have a few Mega clones in the parts bin
I'm going to use 1 Mega and one Nano.

the Nano is only for Drive Enable and uses no serial comm, using the Mega also gives me the option
of adding GPS and other sensors.(hours of entertainment)

I'm interested in testing GPS when the leafs are off the trees.(it's very bad when they are on the trees)

jwatte
11-27-2018, 05:43 PM
SoftwareSerial is always intermittent at speeds above 9600 bps :-(
The interrupts used to drive functions such as millis() end up causing the conflict even if you don't do anything else.

For what it's worth, the Teensy 3.2 is about the same size as the Nano, except it has more capabilities than a Mega (except not as many pins -- the Teensy 3.5 gets close, though!)

Tommy_T
11-28-2018, 06:04 AM
Teensy 3.2 is about the same size as the Nano
jwatte, I've never worked or played with a Teensy yet. sounds like a good
way to spend a winter.(testing Teensy's,Pi's and Edison's)


I'm also not going to be able the use the cheap plastic relays, while they are Big!(sames as sabertooth 50)
I could find room for them but, within 20min. I started smelling melting plastic, hard to get a warm&fuzzy
with that smell.

It's possible it would go way after awhile, but I'm chucking them in a bad parts storage bin.
plan C should be in the mail today.

7374

jwatte
11-28-2018, 12:18 PM
within 20min. I started smelling melting plastic

Oh, yeah, some relays have a limited duty cycle -- for starter motors that aren't intended to run all the time.
In the end, MOSFETs almost always win for longevity! And that's where the Sabretooths of the world come in.
Although, honestly, one could probably build a much cheaper simple H-bridge board with enormous power capacity ... Maybe a business opportunity? :-)

Tommy_T
11-28-2018, 04:26 PM
one could probably build a much cheaper simple H-bridge board with enormous power capacity
jwatte, if plan D fails I may just do something like that.

plan D is to use the same thing I would use to enable a drive on a machine.
I can get these with 24Vdc coils.
7375

Tommy_T
11-29-2018, 04:54 AM
these passed the 24 hour heat test.
7376

they also have a 200A version with the same foot print.
which I'll most likely use when both sabertooth 2x60's are in use.

when I made the motor mount brackets, I made all four at same time.
but, not sure if I'll get all four installed this season(I'm slow).
7377

Tommy_T
11-29-2018, 07:27 PM
baby steps
7380

7381

7402 7403

I'm going to test lifting the bucket while still just bolted together, before I take it back
to the welder. the bucket with dump motor and brackets is only 160lb.

jwatte
11-30-2018, 12:10 PM
"only"

Tommy_T
11-30-2018, 08:33 PM
"only"
Lucky for me I ordered a manufactured steel bucket(80lb) from Home Depot, if I made it,
chances are it would weigh 300lb.(like the lifting frame I'm working on)

there is lots of aluminium in the stock rack at work, but it's for current jobs, there's lots
of steel that is left over from past jobs that I can use for free(free is good, but very heavy)

with the bucket lift installed on the mule I shouldn't have to add any sand bags for weight
to get traction.

7405

jwatte
11-30-2018, 11:30 PM
Free material is best material!
(Or, as I prefer to think of it: Made of pure scrapbinium!)

Tommy_T
12-01-2018, 07:00 PM
I should have the bucket mounted to the lift soon

7406

7407

7408

7409

Tommy_T
12-02-2018, 06:58 PM
plan A is to use one 1000W motor for lifting and one for dumping.

plan B is to use two 1000W motors for lifting and one for dumping.

7410

7411

7412

7413

Tommy_T
12-03-2018, 03:13 PM
the lift works as envisioned, 5 sec. for full lift height, tested lifting 290lb, it lifted
it with no measurable slow down.(Sweet!) the braking system worked perfect also.

everything very smooth, and very quiet.

now for the dumping system.

Tommy_T
12-09-2018, 07:33 PM
baby steps.

got the prox switches for the lift installed.

7415

also moved the bucket out 2" to give me room to mount the dump
motor under the bucket support arm(so it doesn't block camera view) .

jwatte
12-09-2018, 11:35 PM
seeing where you go is important :-)

Tommy_T
12-10-2018, 07:05 AM
seeing where you go is important :-)
jwatte, nothing gives that warm&fuzzy feeling like good visibility.

While I couldn't use the ballscrews I have available for the lifting of the bucket(too slow, small pitch)
they may work out best for the dumping(only 10" travel)

looking for a 4 sec. dump time(2 sec. down, 2 sec. back up)

Tommy_T
12-11-2018, 02:06 PM
smooth!


https://youtu.be/ngi4qHbGw-M

Tommy_T
12-12-2018, 06:42 AM
with all the effort & costs that went into making the lifting frame, I'm going
to install a second prox switch on each end of travel, that shuts down drive
and turns on the brake.

or the sabertooth drive has a current limiting pot, while it can lift 500lb+
there's no reason to for snow. maybe just adjusting to a point where it
can't damage the frame would be best?

jwatte
12-13-2018, 11:10 AM
That looks awesome!

You probably should do both current limiting and safety limit switches.

Tommy_T
12-15-2018, 08:35 PM
Not sure about the plan A for dumping.

the gear motor I plan to use has a 180rpm output, and the sprocket on the buckets
only turns 90deg. to make it at least reasonable if things go sideways, I got 9 teeth
on the motor 45 teeth on the dump shaft, then 12 teeth on the dump shaft output to
the buckets 36 teeth sprocket, which should give it a 8 to 1 gear reduction.

7416

7417

7418

Tommy_T
12-16-2018, 08:36 PM
hope to test the dumping setup this week(waiting on motor with brake)

7419
7420
7421
7422
7423

Tommy_T
12-17-2018, 10:46 AM
to set the height of the blade I had these welded on($25.00 sweet!)
for small casters and a orange plow marker flag(should show up on camera).

7424

I'm going to one more shaft, 12 teeth and 45 teeth get a slower
speed on the dumping setup.
5

Tommy_T
12-19-2018, 06:33 AM
I was able to test the dumping drive setup.
the speed is manageable but, even with a 1" shaft because of
the amount it's unsupported on each end it acts like a leaf spring(crap).

7425

Tommy_T
12-21-2018, 05:29 AM
https://www.youtube.com/watch?v=_qXii29on2g

jwatte
12-21-2018, 10:39 AM
Looks quite robust! Now all you need is another foot of snow ;-)

Tommy_T
12-21-2018, 06:37 PM
jwatte, truth is, I'm not ready for snow.

I'm going to try plan B for the dumping setup.
I did get the new motor and tested the brake to insure
it can hold the bucket up.

heading back to office.

Tommy_T
12-22-2018, 06:43 AM
The way I first tested to do it the only way to adjust the chain tension was to
shim the bucket support arm.
7427

and the motor brake had to hold all the weight that I put in
the bucket.

plan B is to replace the lower chain with an Arm off the dump output shaft,
if when the bucket is in the up position and the arm is at top dead center
the dump output shaft should hold must of the weight not the motor brake.

top dead center should be something like this
7428

Tommy_T
12-22-2018, 09:29 PM
baby steps.
7429

7430

Tommy_T
12-23-2018, 03:59 PM
now with limit switches installed, and the plan B arm completed
the dump setup can be tested(sweet).

7431

7432

Tommy_T
12-25-2018, 11:09 AM
plan B for dumping worked out good enough to play with some snow.(kinda fast)

with the bucket dump all the way up, it's tilted back a small amount(to help keep snow in bucket when lifting)
I programmed a button on the controller to release the brake on the dump motor to let it tilt to the ground
by it's own weight, but because I have it at top dead center it does not float down on it's own.(crap)


https://www.youtube.com/watch?v=UKvGd1JUFG0&amp;feature=youtu.be

jwatte
12-25-2018, 08:29 PM
From what I've learned from hand-pulled snow scoops, you may want to support up to 20 degrees backwards tilt to keep the scooped snow on the bucket. It's annoying when you try to lift things, but they fall off in front...

Anyway, I like the speed, it looks powerful and smooth!

Tommy_T
12-26-2018, 06:48 AM
I hope mother nature delivers some snow soon, I need to
test with snow now.

jwatte, I can only tilt back 10deg with the current bucket support arm.
and because that arm is the weakest link(1/8" tube steel), replacing it
would not hurt my feeling.

I hope to have the cameras on this weekend(back to the office)

Tommy_T
01-05-2019, 05:02 PM
After playing with the bucket for a short time it became clear
the switch idea isn't going to fly, too much time.

so I added a few more push buttons to the remote controller.
7433

I like this better because I can lift or dump while the Mule is
moving. much better.

I kept the switches on the remote controller because I'm sure
I'l find a use for them sometime.

Tommy_T
01-19-2019, 09:10 AM
I was wondering if I could tilt the bucket back enough to keep
the snow in the bucket when lifting.

7436

7437

but, not ideas are good ideas.
I was thinking it would be nice to have all systems running off
one battery bank and needing only one charger, not a good idea..
if a heavy load is placed on the drives,it drives the battery voltage
below the cutoff voltage for the 110ac inverter which then drops the
wifi and cameras.(crap)

jwatte
01-19-2019, 09:23 PM
I imagine the WiFi and cameras use wall warts plugged into the 110V inverter?

I then imagine you could use a wide-input-range buck regulator (or two) to output the appropriate voltage for each of those things, without going up through 110V. You'd just need to wrap it up in some silicone tape or a Bud box with a seal or something to get it out of the weather.
Tons of cheap buck converters from Pololu or Amazon ...

Tommy_T
01-20-2019, 06:21 AM
I imagine the WiFi and cameras use wall warts plugged into the 110V inverter?
jwatte, that is correct.

7438

I got a few of these last year for that purpose, but the 110vac inverter was just too
easy to implement (plug & play). I guess easy isn't always best(or workable).

some cameras need 12vdc, some need 5vdc.

Tommy_T
01-22-2019, 09:11 PM
because we have 6" snow coming in tonight I heated my
home work space and made the power supply changes.

removed Wifi router and cameras form the 110vac inverter.

the only thing running on 110vac is the lights.

and it tested good, under heavy load (lifting weight and driving hard only the overhead lights drop out)

7439

jwatte
01-23-2019, 04:40 PM
Such an awesome remote drone :-)

Tommy_T
01-23-2019, 05:01 PM
Such an awesome remote drone
jwatte, it's too limited by the small front casters right now, but once the back half
is complete(4 wheel drive)...then it's going to be something to behold.

even with it's current limitation i'd call it a SNOW MONSTER

Tommy_T
01-25-2019, 06:28 AM
current camera setup

7440

the snow bank is made by the bucket

Tommy_T
01-25-2019, 07:01 AM
because I can limp along(get the job done).
the next issue needing attention is charging.

I have a few 24V chargers, 5 Amp, 7 Amp (but wanted 20 Amp).

my price range at the time of the lift build was very low.
I found a cheap 24V 10 Amp charger on amazon(under $40)

and was not shocked when it only charged at 7 Amp max.

but I do need better chargers, back to amazon......

with current chargers it takes 15Hr to charge(lost play time)

Tommy_T
01-28-2019, 12:55 PM
https://www.youtube.com/watch?v=fMdravj3FDA&amp;feature=youtu.be

jwatte
01-28-2019, 01:01 PM
Looks cold. Better the robot than me :-)

Lead-Acid are slow-charging batteries; there's really no (safe) way around that. You can charge them with a benchtop power supply set at constant-voltage constant-current limitations if you need to, and dial up the constant-current to whatever charge rate you're comfortable risking. (Beware gassing and possible explosive spray, though!)

If you want faster charging, you're going to have to go LiPo or perhaps LiFePO. Or swappable battery banks.

Tommy_T
01-28-2019, 01:33 PM
Or swappable battery banks.
jwatte, seems doable

Tommy_T
01-28-2019, 05:31 PM
the two outside batteries could quickly changed out.

7441

these type connectors should make the change over
plug&play,some more.

7442

but they each weight about 100lb, so going to have to make
some kind of dolly for the batteries.

I could easily move the lights on the battery cover to some other
location to make changing simplified.

jwatte
01-28-2019, 05:51 PM
Btw, the CC/CV lead/acid cycle that works for me is:

- Set constant voltage to 14.5 V
- Set constant current to something less than the Ah rating of your battery, but in A (i e, <= 1C rate)
- Wait until the battery is drawing < 0.1 of the set A limit
- lower the CV to 13.6V for floating.

Tommy_T
02-23-2019, 04:53 PM
Can't win them all.

the motor I planed to use for the tilting of the bucket use an inline 250Watt.
7457

and with it being only 250W I made it's brackets out of aluminum,
but, the first motor I used I got from ebay for $36.00 and it failed
after one month of daily use. I found a direct replacement motor on
ebay for $125.00 but, it started smoking after just a few times tilting
the bucket.(crap)

I didn't continue testing the replacement motor for fear of it causing
the sabertooth 50 to fail. (that would also suck)

So I changed the motor to a 1000Watt (same as used for the lifting)
7458

I'm not happy with how high it sticks up so I'll look
around for a 1000W inline motor, I'v seen some four
pole inline motors use in hoverround's.

I'l also have to remake the motor bracket in steel.

jwatte
02-23-2019, 06:43 PM
It's the torque, more than the power, that matters for your bracket. Think of it this way: A motor that is stalled develops zero power (at the shaft) but develops a lot of force at the mount!
You can calculate the torque of the mounts, and compare to yield strength of the material at the given thickness/area, and if you're > 10x away, you've got plenty of margin.

Very simplistic rule-of-thumb: torque divided by distance from center of axle to center of hole equals force.
Divide by number of holes equals force per hole.
Calculate projected cross section of each hole wall -- bolt diameter times hole thickness.
Get yield strength in PSI and multiply by cross section of hole wall (in square inches) and compare to force calculated per hole.

So, let's say you have torque of 100 foot-pounds. (That's a lot, btw.)
Your shaft-to-hole distance could be about 2.5 inches. 100 footpounds divided by 2.5 inches equals about 500 pounds of force.
500 pounds of force on four holes is 125 pounds per hole.
Cross section of a 5/8 bolt in a 1/2" plate is 0.3 square inches.
0.3 square inches times 6061 yield strength of 16000 psi times 0.3 square inches means the aluminum should stand up to 4800 pounds per hole.
Your ratio is 38:1 ! (I totally guessed on all the values, though -- I may be totally off.)

Now, this is not a cerfied-engineer calculation by the book, and it's not a FEM analysis in a CAD package, so take it with a shaker of salt, but I've found this gets me to the right ballpark. It seems to me that if your aluminum bracket is anything like this calculation, you're fine.

tician
02-24-2019, 06:06 PM
That's actually the rough process for determining tear-out limits for fasteners in holes, but it says nothing about the rest of the bracket surviving. Also, non-ferrous materials have finite lifespans and low temperatures reduce further ductility/durability. If you have a bit of steel, you can design the part such that the cyclic loading is small enough to allow the part to have effectively 'infinite' lifespan, but non-ferrous materials do not display that property.

jwatte
02-24-2019, 11:35 PM
Sure, aluminum will fatigue and break, but, you know, they make airplanes out of it. With enough safety margin, you'll be fine :-)

Anyway, if he wants to make another bracket because he enjoys making, go for it! If he just wants to plow snow, that seems like maybe not a 100% necessary re-work, of course dependent on the specifics.

I agree that if there are narrower sections or pinch points in other places in the bracket that are more exposed, that would be a problem, too.

tician
02-25-2019, 07:15 PM
Yet airplanes still break apart more often than you would hope because stress fractures can be difficult to impossible to detect visually. They are detected/tracked during scheduled maintenance/inspections, but if they show up too rapidly/severely then the airframe possibly gets grounded then maybe scrapped well ahead of expected lifetime.

jwatte
02-25-2019, 09:11 PM
Only one way to settle this: Build TWO snow plowing mules, one with an aluminum bracket, and one with steel, and measure what the relevant bracket lifetimes are under equivalent workloads!

@Tommy_T, you heard @tician: Get building! :-D

Tommy_T
02-25-2019, 09:56 PM
My concern is not some much that the bracket
could fail, but that it could flex enough to let
the chain jump a tooth.

With a steel bracket the motor would stall before it jump a tooth.

Tommy_T
02-25-2019, 10:04 PM
I would like to try to make the lifting frame out of aluminum and 10" more travel

but all the brackets out of steel

breaking up ice on the streets is very hard work on the mules

also it does't give me a warm&fuzzy feeling watching the tilt motor bounce around
on the camera as it's doing it's work

jwatte
02-26-2019, 09:37 PM
Interesting!

How do you figure out where the main flex is coming from? Do you have video from the sides while it's doing it?

Tommy_T
02-27-2019, 11:10 AM
With the bigger motor it's pointing up and is visible in the camera facing
down on the bucket attachments.

when I get back to Wisconsin Sunday I'll post video of it bouncing around

this week I'm in San Francisco for work, if they got snow here they would be screwed
with these steep angle streets.

Tommy_T
03-04-2019, 01:07 PM
7461

the flexing of this aluminum bracket is due to
the 6" distance between the mounting bolts and
the chain sprocket.

7462

it could be minimized with a gusset added.

I'll test what would happen if a limit switch fails
after I change it to steel.

jwatte
03-04-2019, 05:38 PM
That sounds exciting!

Curiousity killing cats:
How is the "L" part attached? Welded?
How thick is the plate that the bolts go through?

Tommy_T
03-04-2019, 06:54 PM
jwatte, the current motor bracket is made from 2pc .5" x 2.5" 6061 aluminium plate.
the plates are bolted together by (4) 1/4-20 SHCS (grade 8) .

Tommy_T
03-04-2019, 07:48 PM
I'm also not happy with the bracket design when used with the bigger motors.

these bigger motors have OEM mounting holes (6-M6 tapped holes), but I added
(8) 10-32 tapped holes to be able used the current bracket design and current
chain length.

I have 6 of these motors sitting around, but only one that has a 10-32 bolt circle.

if I have to swap motors it would be a pain.

Tommy_T
03-06-2019, 05:22 PM
I just looked up and noticed that it's march.
time to turn attention to mowing, big build this season for dealing with grass.

Lots of fun this winter! looking forwards to next winter.
the bucket turned out to be a very useful attachment.

Tommy_T
03-21-2019, 07:06 PM
the bucket also makes changing mower blades easier.

7468

7469

jwatte
03-21-2019, 11:27 PM
It's a robot controlled lift! Stylish!