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Originally Posted by Larry Barello
The problem is that if your position setpoint is moving all the time (plus & minus, typical for an arm) the integral needed going forward is precisely the wrong thing for moving in reverse! Best to just leave out.
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True, the integral is going to be in the wrong direction at times, and you are going to have a slower response time because your joystick is not hooked directly to the motor values coming from your program. But best to leave out? No...
Without an integral in our program there would be no way for us to control our arm, much less control it with a ball. The integral needs to build up to maintain zero velocity when the lever arm and torque is great, or the arm will simply fall. There really is no way to manage it dynamically otherwise.
We suggest you use the PID loop to control velocity, because that's what's coming out of your joystick. Position may be very tricky, and as Jay and I said, the position system just generates its own velocity value. Don't knock PI loops until you've tried them! We would never have done so well without it.