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Unread 01-09-2009, 10:46 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

I'm not sure who said it but i know some one mentioned before about using an accelerometer to sense drift and turn the wheels perpendicular to the direction of unwanted travel... my team also had a similar idea but threw it out ( for now) due to the fact that this will only make a difference if the deflection of the floor is a [i]relatively[i] significant amount.. We started to reconsider when we found the regolith is over the carpet (or so we've heard) but are still unsure if it will have any useful effect.. if the floor doesn't deflect enough you get the same effect by just locking the wheels, or are we misunderstanding this concept?
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Unread 01-10-2009, 08:52 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

If there is a project for trying to implement a common code base for the base of this an ABS-system-like idea, my team has a couple of programmers who would be willing to help... it could really be an interesting project to implement it together in a codebase for everyone
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Unread 01-19-2009, 09:02 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

Wow, what a thread. Wish I understood what half of it meant, although I did get a chance to learn the first, second, third derivatives of wheel positon are velocity, acceleration, and jerk.

We just started working on this today. We use a potentiometer to measure the rate the wheels are turning. If we see an increase of > 20% in the rate, we reduce the power to the wheels by 20%. Power keeps reducing until the rotational rate gets back below 20%.

May not be absolutely perfect, but we will hopefully get enough of an advantage to beat the teams that don't have traction control.

Unfortunately I think this puts us in the 'tinkerer' category isn't the second first derivative of tinkerer = engineer once you add in the velocity heading towards being able to calculate the results?
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Unread 01-20-2009, 06:02 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

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Originally Posted by rsisk View Post
Unfortunately I think this puts us in the 'tinkerer' category isn't the second first derivative of tinkerer = engineer once you add in the velocity heading towards being able to calculate the results?
Tinkerer + math => engineer
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Unread 01-20-2009, 06:07 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

We're going with a reverse-ABS route for our first attempt:
-If slippage detected, reduce motor power somewhat, then gradually increase it again

Slippage will be detected by comparing the reported acceleration of our encoders with the reported acceleration from our accelerometer.
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Unread 01-20-2009, 07:40 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

For the Tinkerers out there. Please keep one thing in mind. ABS, ESP, Stability control..... All of these get tuned by very skilled evaluator/engineers. I have a friend who does this work for Bosch. Testing and tuning is not simply tinkering, it is engineering. They do however had a pretty good idea of what their algoritms need to look like and then tune them in.

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Unread 01-20-2009, 06:21 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

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Originally Posted by MikeE View Post
Tinkerer + math => engineer
This is the only field where being a tinkerer will mean that your robot will end up in twenty thousand little itty bitty pieces as it thrashes it around because your tinkering resulted in a system that mathematically would blow up the world (An Texas Instruments engineers words not mine) if it were not for the fact that your robot is powered by a battery.
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Last edited by Adam Y. : 01-20-2009 at 06:28 PM.
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Unread 01-21-2009, 09:16 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

Our programmer challenged our 2 year driver to try and beat the traction controlled robot from one side of our field to the other.
The driver lost EVERY time!!

In conclusion, implement it if you can........
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  #84   Spotlight this post!  
Unread 01-21-2009, 10:19 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

Quote:
Originally Posted by rsisk View Post
We use a potentiometer to measure the rate the wheels are turning.
A potentiometer? Not exactly an optimal sensor, look up "encoder" for a better choice
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Originally Posted by rsisk View Post
first derivative of tinkerer = engineer once you add in the velocity heading towards...
Quote:
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Tinkerer + math => engineer
The difference between a Tinkerer and an Engineer is that the Engineer will be able to tell you the results before you start.
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Unread 01-22-2009, 11:03 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

Our team is looking into implementing an algorithm we found for a four-independent-wheel-drive electric vehicle ETS, using four encoders and a gyroscopic yaw-rate sensor. We will be enhancing it with the accelerometer to detect sideways skid and report to the driver, if not correct it.
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Unread 01-22-2009, 03:25 PM
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Re: Implementing Traction Control for an advantage in the 2009 game

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Originally Posted by agmlego View Post
Our team is looking into implementing an algorithm we found for a four-independent-wheel-drive electric vehicle ETS, using four encoders and a gyroscopic yaw-rate sensor. We will be enhancing it with the accelerometer to detect sideways skid and report to the driver, if not correct it.
Right now Warren B and I are trying to get our arms around Paul's "middle income" solution. But for those of you going for the "super rich" solution, I have found a few interesting places to look:

http://scholar.lib.vt.edu/theses/ava...ed/Thesis2.pdf

and here's some observer and alpha-beta filter explanations:

http://www.mstarlabs.com/control.html


Check out "rough Data, Smooth signals" and "When One feedback isn't enough"

I expect SPAM'll compete with the "middle income" solution at the Florida regional

cool stuff
Eric
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Unread 01-23-2009, 08:08 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

Hey, cool! I will definitely have the guys look in on those.
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Unread 01-23-2009, 08:26 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

Just a note:
We went to implement our accelerometer/encoder solution last night, and it wasn't as good as expected. This was partly because I hadn't totally thought it through and thought that simply comparing accelerations was going to be sufficient. I failed to realize the obvious fact that the encoder acceleration would not STAY above the accelerometer acceleration for long, so it is not a good way of telling when the wheelspin stopped. It was an excellent way of telling when your wheel started spinning, but since you can't easily detect when they stop spinning, the algorithm as I described it is not ideal.

We're going to have to get a bit more complicated, with either an estimated velocity from the accelerometer or a trailing wheel to get this working properly.

Last edited by Bongle : 01-23-2009 at 08:31 AM.
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Unread 01-23-2009, 09:11 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

You can try integrating the acceleration signal to get velocity, and then comparing velocities to detect slip. The problem is that a noisy accelerometer signal looks even worse once it's integrated. For this and other reasons (one being the simplicity of an apples to apples speed comparison in code), non-driven encoder wheels lead to a better solution to this problem in my opinion.
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Unread 01-23-2009, 09:34 AM
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Re: Implementing Traction Control for an advantage in the 2009 game

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Originally Posted by Abwehr View Post
You can try integrating the acceleration signal to get velocity, and then comparing velocities to detect slip. The problem is that a noisy accelerometer signal looks even worse once it's integrated. For this and other reasons (one being the simplicity of an apples to apples speed comparison in code), non-driven encoder wheels lead to a better solution to this problem in my opinion.
Yeah, that's exactly what I'm thinking. Even with our rolling-average filtering, the accelerometer is ridiculously noisy.
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