2809 - Traction Control Demo

Mentor_Mike · February 12, 2009, 8:59pm

Video: http://www.youtube.com/watch?v=l1Qk2YPdCY8

Hi All,

So, here’s are preliminary traction control demo. Don’t mind the flooring or the two very dillusional people muttering away.:ahh:

Cheers,
M_M and JNo.

Tanner · February 12, 2009, 9:02pm

That’s pretty neat. Quite cool.

How are you guys detecting a loss of traction? Encoders are my only guess…

-Tanner

Mentor_Mike · February 12, 2009, 9:06pm

Yep, there’s an encoder in the system. Actually there’s two, and some secret sauce.

It’s amazing how 2 years of kinematics can actually be applied to real life.

And no, there’s no accelerometers, or idle wheels.

M_M

Tanner · February 12, 2009, 9:08pm

Wow, very amazing guys. I’m not even sure how we would do that…

Thumbs up to ya’ll! Good luck with it.

-Tanner

Mentor_Mike · February 12, 2009, 9:10pm

Thanks!
You too.

M_M

thefro526 · February 12, 2009, 9:13pm

That’s sick.

Someone deserves a high five.

High Five

Care to elaborate on the mechanics and the programming theory behind it?

Jonathan_Norris · February 12, 2009, 10:16pm

Already Done.

MOE · February 13, 2009, 12:43am

Helloooo from the North East:D
Oh Boy that is a great job… DRIVE the bot and lots of great times will be ahead for your Team …:yikes:
GOOD LUCK in 2009;)
MOE and Team 88 TJ2 TYE DYE for ever oh yeah ??? OH YEAH !!!:o

Mentor_Mike · February 13, 2009, 9:30am

Well, I’d love to tell you all exactly how this was pulled off, but I’m honestly not sure how much detail I"m allowed to reveal. (We haven’t had a discussion with the team about this yet, so I don’t want to jump the gun.)

Here’s what I can tell you though:

We use two encoders, one per side, in addition to another type of sensor.
We found the accelerometers WAY too noisey, especially with the bumpy playing surface.
All four (well, 3 and a bit wheels) are driven, we have no idlers.
Haven’t worked out (unfortunately) how to implement any type of optical sensor to figure out linear velocity. *

That video is no where near the final product btw. We have to calibrate and optimize for the playing surface and the weight of the trainer.

Anyway, I’ll tell you what I can. Please feel free to ask quesitons. If anyone can guess what we did I’d be happy to PM you with our solution. It can be a game of sorts.
BUT, I’ll probably have a white paper drawn out by our first regional (Toronto) and it’ll be posted for all to see.

M_M*

petek · February 13, 2009, 9:40am

I’m glad to hear that you won’t be littering the field with wheel spinach. I don’t think the Swifter would be much help in cleaning up that kind of mess!

Seriously, that looks like a really good traction control system. From the demo it looks like the robot is a lot easier to push around with the system turned off. Is that true?

Team_1708_Dave · February 13, 2009, 9:45am

Great Job Team!!

Very Impressive

mrnoble · February 13, 2009, 6:02pm

This is the most efficient and incredible traction control system our team has ever seen. We would like to use the encoder as well to assist in our traction control. Can you help us?

Mentor_Mike · February 13, 2009, 7:03pm

Sure, what do you want to know?

dani190 · February 13, 2009, 7:18pm

wow guys well done…

Is there any way you guys can share that and help us out?

mrnoble · February 13, 2009, 7:45pm

We would like to use the encoder to measure the rotations of the wheel per second then multiply by the radius of the wheel in order to find the distance the wheel should be traveling (theoretical distance). Then we would use another sensor to measure the distance our robot has actually traveled. If the actual distance is less than the theoretical distance our wheel is slipping. Do you have any suggestions on the sensor we should use to measure the actual distance traveled or any suggested code we could use in order for the change in speed of the motor, in turn lowering or speeding up the rev/sec., to be automatic?

Smoores · February 14, 2009, 12:19am

that robot looks a whole lot better than my team’s rookie bot

nathanww · February 14, 2009, 12:28am

Does your ystem work for acceleration as well, or just shoving? It would be nice to see a comparison of acceleration with and without TC. The pushing thing–it looks nice, but have you collected more empirical data than “he stumbles back more with traction control on”?

crake · February 14, 2009, 12:53am

Really impressive - I’m really looking forward to watching these bots in action! In what language did you implement the traction code?

dtengineering · February 14, 2009, 2:04am

Mentor_Mike:

Well, I’d love to tell you all exactly how this was pulled off, but I’m honestly not sure how much detail I"m allowed to reveal. (We haven’t had a discussion with the team about this yet, so I don’t want to jump the gun.)

Here’s what I can tell you though:

We use two encoders, one per side, in addition to another type of sensor.

We found the accelerometers WAY too noisey, especially with the bumpy playing surface.

All four (well, 3 and a bit wheels) are driven, we have no idlers.

Haven’t worked out (unfortunately) how to implement any type of optical sensor to figure out linear velocity. *

BUT, I’ll probably have a white paper drawn out by our first regional (Toronto) and it’ll be posted for all to see.

M_M*

Well, if I had to hazard a guess at what that other sensor might be, I’d be willing to guess that it is a current sensor. Since torque is proportional to motor current, you could monitor the current draw of your motor to determine at what torque your wheels started to spin, then put in some fairly simple code to limit current to that maximum amount.

Not sure why you’d need encoders with that setup… hmmm… perhaps rather than measuring current, you are measuring voltage across the motors and comparing it to motor speed.

It looks like Ontario has spawned another great team. Good luck at Hershey Centre, GTR is a great tournament.

Jason

Vikesrock · February 14, 2009, 3:24am

If you listen to the audio on the video you can hear the traction control at work. With the TC off you can hear the motors whirring away and the wheels spinning even when the robot is held stationary. With the TC on you can hear that the sound is very different, the wheels are not spinning even though the robot is being told to go forward, but held from doing so.