Can anyone point me towards theretical as well as rules of thumb of tuning two nested PID loops? I have velocity loop is inside a position loop in my application. I am just starting out in this field and would like to learn. Any help will be very much appreciated.

 

A point of view I've found useful is to consider the response time of the processes under control, even if only as a mental exercise, and don't try to control any faster than that. The integral time might then be set to twice (or more) the loop response time. With nested loops, the inner loop must have a faster response time than the outer loop.

Another way to look at nested loops, i.e., where the outer loop establishes the setpoint for the inner loop, is to think about how fast you could change (e.g., manually) the inner loop's setpoint and expect to have good control. This is really the same as above.

Ken

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Ken Irving