Why and when use Derivative in PID control? The vast majority of PID controllers are tuned with Proportional and Integral action only, while in some cases controller performance could be improved by including the D-action. Read in this blog what derivative action is and what to expect of the webinar ‘Don’t be afraid of the D’.
PID tuning parameters: Derivative
PID is an acronym for Proportional, Integral, and Derivative. These PID parameters can be used, adjusted, and controlled individually and collectively. You can have, for example, a P controller, a PI controller, or a PID controller. Each parameter can be adjusted and controlled individually, and each parameter used for specific purposes.
The derivative action is the amount of controller output due to the change of the error (or measurement). In other words, it adds a contribution to the output according to how the error/measurement changes. When the error/measurement is positive but is starting to decline the D action, it will reduce the output of the controller.
It’s acting as a brake that tries to avoid overshoot. It reduces the oscillations induced by the other two actions. It can speed up the controller response to the setpoint changes if that's what we want to achieve.
How to use PID derivative control
Like the webinar says: DCS engineers are often afraid of the derivative in PID tuning. The reason for this fear is that in a lot of loops it’s not needed or desired to use the derivative parameter. It’s not a common practice and engineers who never use it is growing. In some cases, they experience that D has causes nervous control behavior. However, this doesn’t mean that you shouldn't consider using the derivative parameter at all because :
- D action can improven (speed up) tracking behaviour
- D action can improve reducting oscillations (slow)
When you do consider D action, keep some considerations in mind:
- When using the derivative, make sure you do it for the right reason (apply it to the correct loop)
- When using the derivative, make sure you use the proper equation type.
- When you have a noisy measurement, the Derivative-action can cause amplification of noise to the controller output. So, do not use Derivative without applying a derivative filter ( and tune it correctly )
Webinar: Don’t be afraid of the D (in PID tuning)
The webinar will explain in more detail the behaviour of the Proportional, Integral and Derivative parameters. Explain how to use derivative control and will discuss the pros and cons of using the PID derivative based on common PID control problems. The following PID situations will be discussed:
- PID on error reference case
- I on error and P, D on PV
- P, I on error and D on PV
- Derivative filtering
After these situations, a solution will be shown based on practical examples of a temperature control loop and level in a waste heat boiler.
Curious how to overcome your fear of the D? Watch the webinar here.