2809 - Traction Control Demo

[Mentor_Mike]

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.

Cheers,
M_M and JNo.

[Tanner]

That's pretty neat. Quite cool.

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

-Tanner

[Mentor_Mike]

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]

Originally Posted by Mentor_Mike

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

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]

Thanks!
You too.

M_M

[thefro526]

That's sick.

Someone deserves a high five.

*High Five*

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

[Jonathan Norris]

Originally Posted by thefro526

Someone deserves a high five.

*High Five*

Already Done.

[MOE]

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

[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. [I'm convinced those new-fangled "gamer mouses" would work, but we don't have the $$$ to test this theory.]

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

[dtengineering]

Originally Posted by 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. [I'm convinced those new-fangled "gamer mouses" would work, but we don't have the $$$ to test this theory.]

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

[360skier]

Originally Posted by 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. [I'm convinced those new-fangled "gamer mouses" would work, but we don't have the $$$ to test this theory.]

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

The method you're using appears to be the TLS method, in which the speed of the driven wheels is compared with the speed of the undriven wheels. However, since no wheels are idle than there must be another way of sensing your speed. You aren't using an optical sensor or an accelerometer, and ultrasonic sensors would get too much interference from other robots.

My only other idea would be attaching a free-swinging pendulum to the robot. An encoder or Gyro attached to the axel of this device could then be used exactly the same as an accelerometer but without the noise. This does seem like a lot of work though. Does anyone else have a simpler solution to detecting speed?

[FRC4ME]

Originally Posted by 360skier

The method you're using appears to be the TLS method, in which the speed of the driven wheels is compared with the speed of the undriven wheels. However, since no wheels are idle than there must be another way of sensing your speed. You aren't using an optical sensor or an accelerometer, and ultrasonic sensors would get too much interference from other robots.

My only other idea would be attaching a free-swinging pendulum to the robot. An encoder or Gyro attached to the axel of this device could then be used exactly the same as an accelerometer but without the noise. This does seem like a lot of work though. Does anyone else have a simpler solution to detecting speed?

Here's a hint; you don't need any bearing at all on the robot's position, speed, or acceleration to prevent slipping. You don't need current sensors, either; just an encoder on each drive wheel.

I assume 2809 is probably doing what we're doing this year. More details to come on Monday (if it works).

[Mentor_Mike]

Originally Posted by 360skier

The method you're using appears to be the TLS method, in which the speed of the driven wheels is compared with the speed of the undriven wheels. However, since no wheels are idle than there must be another way of sensing your speed. You aren't using an optical sensor or an accelerometer, and ultrasonic sensors would get too much interference from other robots.

My only other idea would be attaching a free-swinging pendulum to the robot. An encoder or Gyro attached to the axel of this device could then be used exactly the same as an accelerometer but without the noise. This does seem like a lot of work though. Does anyone else have a simpler solution to detecting speed?

Dude, that sounds WAY complicated. The trouble we're finding is that with the bumpiness (is that even a word?) of the surface, anytype of sensor like that creates (or created in our case as we stayed FAR away from it) a lot of noise. Never thought of a pendulum though, that would be kinda neat. But again, with the vibration I feel like the dampening system would need to be quite intense.

[petek]

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]

Great Job Team!!

Very Impressive