why the derivative in PID is always set to zero?

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why the derivative in PID is always set to zero?..

Answer / abhijt n. sonar

Derivative gain is used to take the preventive action in
control. i.e. it gives the corrective action for future
based on the nature of present error. And Derivative action
is used to fast the porcess.
Due to this property of Derivative gain, the process may
become fast and unstable. To avoid this, generally
Derivative gain is kept as minimum as possible i.e. zero.

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why the derivative in PID is always set to zero?..

Answer / kyle condran

derivative works on rate of change of error(slope of error) and assumes that the process will continue changing at that rate and tries to overcompensate for it.

so for fast processes upsets or step changes have high error slopes, sometimes almost infinite or straight up, so the control goes nuts trying to compensate for error. There is usually an option to suppress derivative is for step changes but for fast processes is should be zero.

You will see derivative on laggy slow processes such as some temperature and large volume level loops.

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why the derivative in PID is always set to zero?..

Answer / snehchudasama@gmail.com

yes i m agree with this ans that process is fast.but can anyone tell me why process is fast if i increase the derivative gain?or how can system predicted by considering old values?

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