Measurement noise filtering for PID controllers

• Measurement noise attenuation for PID control using a second order filter has been investigated.
• The filter time constant effects on performance and noise attenuations was explored.
• A new criterion named SDU is proposed to characterize measurement noise attenuation.
• Simple design rules for choosing the filter time constant have been developed.
• Filtering reduces control actions due to measurement noise with moderate decrease of performance.

Measurement noise can generate undesired control activity resulting in wear of actuators and reduced performance. The effects of measurement noise can be alleviated by filtering the measurement signal. The design of the filter is then a trade-off; heavy filtering reduces the undesired control activity but performance is degraded. In this paper we discuss the trade-offs for PID control. Based on the insight gained we introduce two quantities that characterize the effect of measurement noise the SDU, which is a measure of noise activity analog to the IAE commonly used to characterize load disturbance response, and the noise gain kn, which tells how fluctuations in the filtered measurement signal are reflected in variations of the control signal. Simple rules for choosing the filter time constant for PI and PID controllers are also given. The results are illustrated by simulations and lab experiments.