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Unread 30-01-2011, 21:03
EricVanWyk EricVanWyk is offline
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Re: Jaguar Speed Control Only Reaches 50% of Setpoint

By definition, it is impossible to stably hit your set point with a P only control loop. You must have an I term.

A PID loop is calculated with respect to the error, or difference between what you want and what you have. As you approach the setpoint, the error approaches 0. Therefore, the output of the P term approaches 0. Therefore, with a P only loop you will always undershoot your target. You can jack the P gain up to reduce the undershoot, but it will never be zero. If you jack it up too high, noise will dominate and the whole thing will go unstable.

Keep the P where you have it (hitting half your goal) and add a bit of I.
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