Quote:
Originally Posted by joeweber
The reason we do not drive the wheels straight off the Bainbot shaft is to allow for straight driving. You know that the motors drive faster one direction than the other direction...
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That's much less of an issue than you might think. The CIM motors in particular have negligible directional bias. What I've discovered is that the
Victor bias is the real troublemaker. With factory calibration, the neutral point on the Victor corresponds to about 132 on the IFI PWM scale. If you treat 128 as the neutral, you end up with a tendency for the motor to run faster in reverse than in forward.
We had a robot a few years ago that would unexpectedly turn slightly under autonomous control. Calibrating the Victors to the RC output fixed the problem completely. We've made it a point to calibrate them ever since, even including a special function in the robot code to sweep a selected PWM output from full forward to full reverse and back to neutral. (Last year, we defined full forward as 228 and full reverse as 28, and we did a similar calibration for our joysticks. It made working with the code a tiny bit easier to have the valid range of both control and output values be +/- 100.)