Re: Team 121 Traction Control
 

Thats pretty awesome. I have one question though, what kinda feed back are you using from the robot to use your traction control off of. We have some ideas and want to see how others are doing it.

Re: Team 121 Traction Control
 

Can you explain what you mean by traction control? Like, what was different between traction control and non-traction control?

Re: Team 121 Traction Control
 

What surface are you using? Is the the real "regolith" material that will be used in the crater?

Re: Team 121 Traction Control
 

Traction control basically senses if your wheels are spinning and if you're moving. If the wheels are just spinning and you aren't moving it slows the wheels until the robot starts to accelerate.

And yes, it appears to be regolith from what I can see

Re: Team 121 Traction Control
 

How did you do it? I'm asking all teams with working traction control. I see traction control threads, but as of yet I don't see one where someone says how they successfully did it.

Re: Team 121 Traction Control
 

I too would enjoy hearing the mechanism/electronics and logic used to achieve this result.

Re: Team 121 Traction Control
 

Great work! The traction control performs better than I thought! It also looks like you're controlling two wheels with one motor! Much simpler than four wheel drive and it still seems to do quite well! I'm dying to know if you guys used the accelerometer or an idler encoder wheel as feedback. Again, great job!

Re: Team 121 Traction Control
 

That's a nice encoder / idler wheel setup you've got under there. Looks mighty familiar. I wonder where I've seen it before.....

Re: Team 121 Traction Control
 

I count 5 wheels in contact with the ground. Big difference looks good. The only good video our team has of traction control is when i got stuck in the ditch heading home from a meeting...

There are generally two ways of achieving traction control.

1) wheel based; uses a 5th wheel (or 7th), high traction wheel to get the speed of the robot (this is legal, per a Q&A post by the GDC), then it compares the speed that the traction wheel is turning at (the speed of the robot), and the speed of the other wheels (that drive the robot), and it attempts to get them spinning at the close to the same speed so your CoF (friction constant) gets closer to the static friction CoF (a different friction constant, larger by definition), to better the drive the robot.

2) accelerometer based; integrates the accelerometer input to get velocity, instead of the using a spare wheel..

that is how Traction control works in FRC (or at least how my team is doing it)

Re: Team 121 Traction Control
 

Yes, this is the actual field surface.

The theory is simple, actually implementing it is a bit harder. The basic concept is, throttle back an appropriate amount when your ground speed is less than your wheel speed (indicates your wheels are spinning).

Ground speed can be calculated by either a follower drag wheel, or an accelerometer. We're using the follower wheel.

At this point the software is only reading 4 encoder inputs, 2 on each AndyMark gearbox, and 2 in the follower drag wheels. We have current sensors mounted, and in the coming days/weeks we hope to have a finer control of maintaining the delicate balance between maximum acceleration, and spinning out of control (it's a very fine line).

There are many good articles/thesis papers online that have incredibly detailed technical workings of how to successfully implement this. We obviously aren't the first to come up with this kind of system, i'm sure many teams will have similar systems. Maybe this year in Atlanta we can have a robot pushing competition after hours.


Why re-invent the (follower) wheel?


Getting there :)

Re: Team 121 Traction Control
 

Does this set up make it easy to write traction control programs for turning, since you have a follower wheel for each side of your skid steer drive train? Definitely proof that traction control makes a huge difference, thanks for posting the video!

Re: Team 121 Traction Control
 

very nice how long did the code take your team?

Re: Team 121 Traction Control
 

Many thanks for sharing this. It provides a benchmark comparison that will be invaluable to my team and to others.

Re: Team 121 Traction Control
 

I can't watch the video yet; work has most team sites blocked since they're not categorized as 'safe' (they're just 'none'). So I'll see it in a few hours. Now, I say this next statement because I know our programmer lead who's at the school right now may watch this video and perhaps forget that there are still many other things to be done that have a higher priority...

Make sure you guys/gals are sticking to your goals and strategies -- retrogressing just to get a third-order traction control system implemented will severely hinder your progress, and therefore your overall performance. If you have a plan and traction control wasn't included, stick to the plan (but perhaps speed it up a bit ;)). We're in this situation, but tonight we made huge progress so maybe we'll have a little bit of time left over around ship date.

Re: Team 121 Traction Control
 

I'm going off topic from this team, but has any other team had success with traction control without an idler wheel? If so, please share! I am interested in hearing other success stories.