New wheels / floor and encoders for position.

[EricVanWyk]

The hard part of using the mouse is interfacing to it. The new controller doesn't have any USB inputs on the Robot side, so you would either have to add a microcontroller or learn the PS/2 standard.

Alternatively, you can poke directly into the chip inside the mouse. There is no guarantee that this is a standard protocol - each vendor can use their own. This is the route we chose.

[Jeff Pahl]

The kit also came with a nice accelerometer. If the wheel speed does not match the expected value from the accelerometer, then .....

I think the encoders are going to be very useful this year.

And my gut feeling is that anything touching the floor other than the approved wheels is going to not pass inspection.

[Dave Flowerday]

Originally Posted by EricVanWyk

Alternatively, you can poke directly into the chip inside the mouse. There is no guarantee that this is a standard protocol - each vendor can use their own. This is the route we chose.

Back in 2004 when we worked with Technokats to rework an optical mouse to detect robot movement, we interfaced directly into the chip in the optical mouse and bit-banged the protocol. It was pretty easy with the IFI RC. At that time, there was only 1 manufacturer of the optical interface chips (probably due to patents etc). Not sure if that has changed since then.

[chmp09]

You could use a combination of encoders and an accelerometer to create a traction control system. Traction control works by transferring power to the wheel(s) that is not slipping (ex. if you're driving a car and one of your powered wheels is on ice and the other is on pavement). This wont work when all your drive wheels are on the same surface.

Preventing your driver from spinning out the wheels is the best that you can do (this will provide rolling friction rather than sliding friction). Anti-lock braking wouldn't be a bad idea either.

As far as telling where you are at, a system using an accelerometer and gyro should do the job.

[Tom Line]

Using the accelerometer and gyro for traction control are a bit more difficult that people have been saying without a pretty decent bit of math.

The accelerometer gives linear acceleration.

The gyro can give angular acceleration.

You will need to combine the two mathmatically and integrate to get the expected wheel speed.

Most quadrature encoders that are reasonably expensive are 256 counts a turn (or thereabouts).

When you start to compare the wheel speeds to the expected speeds, the error introduced by the integration of the acceleration and the inaccuracies due to the counts / turn calculation of wheel speed create a very non-trivial problem to keep your wheels from slipping all the time.

Most people I know who have traction control turn it off in the snow. Many times you NEED to floor it, and the traction control simply won't let you. Plus, you can't accelerate at all.

This isn't ice - it's simply low friction. Desensitized joysticks and careful drivers will likely be a better idea than traction control for 'most' teams.