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ArduTank
01-07-2013, 08:04 PM
http://i1252.photobucket.com/albums/hh568/slowstickk/IMG_0105.jpg

My MW bot: M-O

9 HS-311 servos
Arduino & Raspberry pi for brains
A Battery for the servos, and one for the Raspberry pi and Arduino
Will have a "defender" style gun.
Control is over WiFi


Yes, I know that hobby servos suck, but I got 7 hobby servos for the price of 1.5 AX-12's, and I know hobby servos better.

Video will come when I have him walking.

Th232
01-07-2013, 10:47 PM
What's the projected weight? I'm concerned that the servos might overheat under continuous use.

DresnerRobotics
01-08-2013, 08:47 AM
I think you're about to learn a valuable lesson on servos. There is no free lunch. :)

ArduTank
01-08-2013, 02:46 PM
Projected weight: 3 lbs

Tyberius, I know that this goes against what you know, but I can make this work.

DresnerRobotics
01-08-2013, 03:52 PM
Quite the contrary, my 3rd robot was a 2dof quadruped using HS-311. I'm well aware of the payload capabilities and performance, and I was using a leverage system on the vertical axis.

Also, I can't stress enough that control via Wifi is a terrible idea. You're going to have one channel to broadcast video and send control data to. If that falters at any point you'll DQ. There is a reason that the people who have been competing in this competition for 4 years now use Xbee for control, not wifi.

If you want to build a cheap hobby servo based walker, the way to do it is with a mechanical lever advantage, so that when it's standing the weight rests on the shaft of the servo requiring very little power to stand. Lifting legs only lift themselves while the planted legs support the weight on the shaft. Your coxa's will need reinforcement in the form of a rear idler opposite of the servo shaft.

Perfect examples found here:

http://www.lynxmotion.com/images/html/build041.htm

http://www.lynxmotion.com/images/data/qp2-v1.pdf

jwatte
01-08-2013, 06:58 PM
control via Wifi is a terrible idea

Are there any actual descriptions of what the problems are?
I can't believe that you can use WiFi for a camera stream, yet can't get a 20 kbit/second control stream through that same network.

DresnerRobotics
01-08-2013, 07:06 PM
Are there any actual descriptions of what the problems are?
I can't believe that you can use WiFi for a camera stream, yet can't get a 20 kbit/second control stream through that same network.

The issue is reliability more than anything. Until you've witnessed Robogames and its inherit 2.4ghz spectrum nightmare it's hard to explain. Camera feeds will work fine for one hour, next hour be almost un-usable. This is exactly why we're testing 5.8ghz this year. Even with the massive upgrades to our wifi system last year and relocation to the other side of a concrete barrier, we still had to put matches on hold until it cleared up, multiple times. Wifi is not a reliable signal at Robogames, so putting something critical like your control on something that is prone to lag and interference is not a good plan.

Video feeds lagging a bit or occasionally timing out is one thing, you add in the possibility of lag/timeouts to your control system as well and you're not going to have a good time.

For anyone reading-by all means, use wifi as your control system. Learning is sometimes best done by making mistakes, but I can almost guarantee you will be sorely wishing you'd taken my advice come April. :)

ArduTank
01-08-2013, 07:06 PM
I can get this to work. I have worked with wifi and interference more than you think. video will be via mjpg-streamer, and control will be via TightVNC. And i'm not sure what your criteria for DoF is, but the bot will be able to side-step.

DresnerRobotics
01-08-2013, 07:07 PM
I can get this to work. I have worked with wifi and interference more than you think. video will be via mjpg-streamer, and control will be via TightVNC. And i'm not sure what your criteria for DoF is, but the bot will be able to side-step.

Go for it then. I'm just sharing my personal experience with such robots and this event.

ArduTank
01-08-2013, 07:10 PM
Go for it then. I'm just sharing my personal experience with such robots and this event.

I know that you are, but I'm just saying, I can make it work.

jwatte
01-08-2013, 11:07 PM
ArduTank: I look forward to battling you come April! I'm also using a Raspberry Pi, and I'm also planning on using WiFi.

Tyberious' advice is pretty important to me. If I still have time, I will create a backup link using some wireless connection modules I have laying around.

Or perhaps I'll "just" enter as autonomous instead ;-)

ArduTank
01-09-2013, 03:44 PM
Jwatte, if you mean the event in California, I won't be at that one. I will be at the West Virginia one, due to the fact that I live in Indiana.

Tyberius, is wood doweling a legal material to use in a bot???

DresnerRobotics
01-09-2013, 05:41 PM
If there are not specific rules stating that something is disallowed, it is allowed. There are no specific rules citing anything about build materials, I leave that up to the builders.

jwatte
01-09-2013, 06:16 PM
Jwatte, if you mean the event in California, I won't be at that one. I will be at the West Virginia one, due to the fact that I live in Indiana.

I did mean the one in California, but... do you have the link to the West Virginia one? I have some frequent flier miles I need to use before they expire...

ArduTank
01-09-2013, 06:47 PM
It's on the website. There's a question in the FAQ for locations. It's the Shep Robo Fest location.

@Tyberius: That's all I wanted to know. I'm making a set of mechanical advantage legs for him and I'm making them out of 1/4" wood dowel rod.

jwatte
01-09-2013, 09:41 PM
It's on the website. There's a question in the FAQ for locations. It's the Shep Robo Fest location.


Awww. Registration is closed :-( And it's right before RoboGames, too, so it'd be the perfect dry run...

lnxfergy
01-10-2013, 04:14 AM
Awww. Registration is closed :-( And it's right before RoboGames, too, so it'd be the perfect dry run...

I'm thinking that registration page might be from 2012... I can't imagine they already closed for this years event. I'd drop an email to somebody and see.

-Fergs

ArduTank
01-10-2013, 05:46 PM
http://i1252.photobucket.com/albums/hh568/slowstickk/IMG_0109.jpg

M-O version 2:

I upgraded his legs to be better. the previous design was having problems with torque on the knee servos.

Th232
01-10-2013, 06:12 PM
I figured that'd be the case. How much mechanical advantage does the linkage system give you?

ArduTank
01-10-2013, 06:25 PM
Quite a bit more. I haven't powered him up yet to check. It should make walking easier. Also, it looks better. :)

jwatte
01-10-2013, 10:23 PM
Another benefit of wood: It takes paint very well, once you're done with the engineering part :-)

ArduTank
01-11-2013, 03:11 PM
True. I powered him up last night and his servos weren't straining at all to stand and move. Still finishing walking gait.

ArduTank
01-16-2013, 03:39 PM
I won't be competing this year unless I find some way to get the scoring system much cheaper. I will only be able to afford one scoring panel by the time the event in west virginia rolls around.

DresnerRobotics
01-17-2013, 03:09 PM
If you post a video of your mech fully functional and operating in a competition ready state, I will personally sponsor an entire scoring system for you.

ArduTank
01-17-2013, 05:05 PM
That I might be able to do. I'll then have to only worry about getting it done and the date of the event.

EDIT: I still won't be able to go this year. My parents have already vetoed that, due to the fact they don't have enough money to get me there this year. And any offers for transportation will be promptly turned down.

sarendt
01-18-2013, 12:55 PM
ArduTank

What if we started a fund to get you to the event? It seems you have enough interest on the site I think we might be able to raise enough money to get you there with your parents? We could post here with how much we could give, and if Andrew thinks your good we could pay via paypal etc to trossen (maybe?) and andrew could send the money along with the scoring system?

I'm willing to put in $50 for this if Andrew thinks its ok to try.

Cheers,
Scott

ArduTank
01-18-2013, 03:33 PM
That wouldn't work either. My mom is saying not this year period, due to us having too many things going on and not enough time or money to get there.

sarendt
01-19-2013, 04:25 PM
Well, in the mean time I look forward to more videos of your bots!

Cheers,
Scott

ArduTank
01-20-2013, 12:01 PM
http://youtu.be/W7Rr5JpGsMM

This is him trying to walk. the lame leg is due to a glitch in the code making 2 of the legs decide to set back down again far too early.

ArduTank
02-03-2013, 07:58 PM
M-O Version 2:

Yes, he is a biped.


http://i1252.photobucket.com/albums/hh568/slowstickk/M-O2001_zps83a058df.jpg

http://i1252.photobucket.com/albums/hh568/slowstickk/M-O2002_zpsb20b235d.jpg


I decided to go to this bipedal design due to the lower number of servos, and the fact that for me, bipeds are easier to code. I will get him wired up and started on the code tomorrow.

One question though: Can target plates legally be used to protect electronics that run the bot?? Such as covering the RasPi I am using with the back 3x3 one?

cire
02-03-2013, 08:12 PM
I don't think you are even required to protect your electronics, but yes you can use your target panel to protect them, as long as the mounting follows the rules. Your biped looks very lightweight. How do you plan on turning?

jwatte
02-03-2013, 10:36 PM
I love how you use the wood sticks with the servo mounts and horns. Absolutely no wasted weight there!

Yes, you can use the target panels as enclosure. Or, rather, you can build a fully exposed mech, and then mount the target panels in a way that makes them easy to shoot at for the enemy -- and if that happens to cover your exposed belly, well, goody for you :-)

That being said: I don't see how you'll be able to mount battery, gun, ammo, and sensors on that body. I don't think it'll be robust enough. I would *love* to be proven wrong, so keep at it :-)

ArduTank
02-04-2013, 05:44 AM
@cire: he will turn by putting his feet with one forward of the body and one behind the body and then moving them back to center

@jwatte: yeah, in fact the leg design is based off of the Star Wars at-st and the mech warrior 4 mercs flea. The battery will be in the hips, the gun will be on the turret, the camera will be mounted to the gun, and the raspberry pi will hang off the back with the arduino in the turret. And you know that he'll stand easy when I can get him to stand without powering up or connecting servos

ArduTank
02-19-2013, 07:08 PM
Update: the legs are getting a redesign due to drilling errors when I made the mounting holes in the wood doweling. Next design will be thin metal *or some material stronger than wood doweling*.