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Unread 04-01-2009, 19:27
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FRC #1718 (The Fighting Pi)
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Re: New wheels / floor and encoders for position.

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.