There are generally three settings you must adjust to make a PID based controller work correctly:
Ziegler / Nichols Starting Point: There are several ways to tune a PID controller, these steps present the Ziegler / Nichols closed loop method as a starting point. Further "trial and error" tuning should certainly be used: (Commands for the BOB PID system will be shown in parenthesis after each step... your systems commands may vary. For e.g. Arduino or other hard coded systems, adjust the parameters in the sketch before programming each time.)
Now try moving back and forth and see how the system reacts. Make both short and long jumps, small and large movements. e.g. (10{enter}1{enter}200{enter}1{enter}...) If it starts oscillating out of control, disable the motor and continue with troubleshooting below. ({space}) Be sure to give it time to settle at each point, and ensure it really does make it to exactly the desired point (mark the shaft if you can).
Once you have the tuning done, save the values to non-volatile memory {321w}
Oscillation: If you have a very heavy shaft, meaning a lot of mass turning on the shaft especially away from the center of rotation; this has nothing to do with the weight of the load being moved unless that load is spinning with the shaft, then increase D until you start to hear shuddering or vibration as it approaches a new setpoint. If you have a lot of overshoot when approaching a new setpoint, decrease I. Otherwise, decrease P.
Slow approach to setpoint: If you have a lot of friction in the system, increase I. If the system "grinds" or "shudders" or vibrates as it approaches the setpoint, decrease D. Otherwise increase P.
Overshoot (without oscillation): Decrease P.
See also:
file: /Techref/io/SERVO/PID-tuning.htm, 6KB, , updated: 2016/5/9 09:08, local time: 2024/10/13 18:38,
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