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Hello,
I'm simulating a basic PID control system in excel. I've got Proportional and Integral action working fine, but when I add in Derivative action, it doesn't seem to follow the form expected.
As I understand it, Derivative action reduces overshoot and shortens settling time (with appropriate tuning of P and I), but I am finding that Derivative action increases overshoot and settling time, eventually sending my system into oscillation.
Given the basic PID formula of:
Pout = Kp.e + Ki.{integral}e(t) + Kd.(de/Dt)
I can't see how the derivative component could achieve this "damping" effect in any case, as surely, as the rate of change of e increases, so Kd.(de/Dt) also increases, throwing the system out of control.
If somebody could explain this to me, I would be very grateful.
Many thanks,
Paul
I'm simulating a basic PID control system in excel. I've got Proportional and Integral action working fine, but when I add in Derivative action, it doesn't seem to follow the form expected.
As I understand it, Derivative action reduces overshoot and shortens settling time (with appropriate tuning of P and I), but I am finding that Derivative action increases overshoot and settling time, eventually sending my system into oscillation.
Given the basic PID formula of:
Pout = Kp.e + Ki.{integral}e(t) + Kd.(de/Dt)
I can't see how the derivative component could achieve this "damping" effect in any case, as surely, as the rate of change of e increases, so Kd.(de/Dt) also increases, throwing the system out of control.
If somebody could explain this to me, I would be very grateful.
Many thanks,
Paul