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Originally Posted by Andy A.
It turned out to be a mess. I think we faced the same problem. It was difficult to account for the friction of the wheel against the carpet in the steering motors programing. Basically, we could never get the ramp up and ramp down curves right, so the wheels would over or under shoot their target positions. We got close, but had to forever tweak them, and only really got it to work on a cement floor. Compounding that problem where the poor pots we used. They tended to drift and developed big dead bands at seemingly random points along their range. It was maddening.
My suggestion is to gear the servo motors way down and reduce youre overall speed. At high speed I think you will just have to much stuff moving with to much momentum for the computing side of the bot to keep up. The lower ratios will help your servos 'sneak up' on the target position.
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I know it wont help you now but here are a few ideas that might help you in the future. Instead of ramping up / ramping down the servo (motor) use a 2 (or 3) speed shift on the fly transmission on your Ackerman steering servo. This can give you Gross / (medium) / fine adjustment while giving you the torque you need when friction gets high (due to low speed and high friction surface) and will avoid hunting (classic oscillation). Also widening your deadband will help minimize hunting.
Also, potentiometers (especially multi turn types) do not like side loading and will tend to create dead spots as the wiper arm wears away at the carbon inside. To avoid this you need to support the shaft of the potentiometer with a bearing (a bushing might work but you need to watch for galling).