More Mule then Rover?

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/Ari...m=shop+portals



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

Tommy

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.

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

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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.

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

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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

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...Mower/13346325

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Not sure why people try to build lawn mowing devices from scratch

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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).

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build lawn mowing devices from scratch

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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).

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and with larger gas tanks can run for many hours/miles.

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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

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Originally Posted by Tommy_T

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.

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+Rep.

-Fergs

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Originally Posted by zoomkat

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...Mower/13346325

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

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Originally Posted by Tyberius

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

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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.

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Originally Posted by zoomkat

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.

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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.

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I think this project as currently described will probably fade away as a collection of half built parts

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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

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.

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Originally Posted by Tyberius

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.

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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.

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Tommy what are you running for a motor controller?

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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.

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

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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

Here are 2 pics
First bare chassis no batteries or motor controller
Second is placementof the Zotac Mother Board

http://forums.trossenrobotics.com/at...1&d=1283732660

http://forums.trossenrobotics.com/at...1&d=1283732660

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.

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.

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Have you torn the motor controllers apart and looked at the boards?

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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).

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High-current/high-voltage motor controllers are actually pretty available

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That is true, and I had planed to use the http://www.roboteq.com/brushed-dc-mo...ontroller.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

>> 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.

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

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

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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)

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What you're needing is a PID loop and maybe some good Kalman filtering to tame it down as much as you can.

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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

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.

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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.

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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

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/at...1&d=1283816023

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

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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

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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

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

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

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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

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/...94c2bcce5d0560

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How much current does your linear actuator require

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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.

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and does it contain an internal pot?

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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

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Fortunately, you're not building a mobile CNC

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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.

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

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jdolecki
I wonder if you used the above thinking, would it improve your chances of winning?

Tommy

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Originally Posted by Tommy_T

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.

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

1. 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).
2. 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

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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).

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lnxfergy
After reading the rules for the RoboMagellan contest, I can see the above working.

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you'll need a localization routine

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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

That's hardly localization...

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.

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That's hardly localization...

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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

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

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

Quote:

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HYD pump from American Science and Surplus.

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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

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

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

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?

Quote:

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

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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.

Quote:

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Looks good.

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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