PID output delay after long period of regulation

[konrad.gl...@gmail.com]

Hi,

I have a problem with PID output (standard arduino PID library). I have remote controled winch based on two arduinos hooked to nRF24. One is just reading potentiometer volatge and sends value in % to the other one, where it is converted to % of force that I set at the startup. Job of PID is to control throttle of motor via servo to maintain the desired winching force. So setpoint is changing. This works fine unless I leave arduino on for some time without the motor running. PID sends for longer time maximal output value to servo (180*), but of course it can't get to the setpoint, beacuse the motor is off. When I turn on the motor PID keeps sending the maximal output, despite that the force is already way over the setpoint. I noticed that the time before it starts to decrease the output is equal to the time I left it without the motor running. What causes this behaviour?

My values:

#define KP 40
#define KI 40
#define KD 15

[Pieter S]

If you work in % check your pid output limits. Default is [0,255]

https://playground.arduino.cc/Code/PIDLibrarySetOutputLimits/

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[konrad.gl...@gmail.com]

Alright, I found what was the issue - Windup --> http://brettbeauregard.com/blog/2011/04/improving-the-beginner%e2%80%99s-pid-reset-windup/ . The PID was accumulating error and it took time before it could overcome it