Are anti-aliasing filters really necessary for sampled-data control?

Abstract

In the paper the role of anti-aliasing filters is revised based on control quality assessment of various setups of analog filters used prior to sampling, or their lack. Numerical results show that contrary to common belief possible benefits gained from anti-aliasing filters are very restricted.

Impact of anti-aliasing filters on optimal sampled-data PID control

“…The best results in the latter case are obtained when the continuous-time output is passed through a continuous-time Kalman filter before being sampled. Similar results were observed in PID control systems [6], [7], [8] In the present paper we study these issues in the context of optimal discrete-time PID control and compare the results with LQG minimum-variance control.…”

“…In [4], [5] we studied the impact of antialiasing filters for pure signal processing while in [7] in the discrete-time LQG control context, and we have found that there is no reason for using them in the noiseless case, and practically no use in the case of noisy measurements. The best results in the latter case are obtained when the continuous-time output is passed through a continuous-time Kalman filter before being sampled.…”

On the effect of anti-aliasing filters on sampled-data PID control

“…Anti-aliasing filters usually take the form of Butterworth filters whose cutoff frequency equals to the so called Nyquist frequency ω N = π/h depending solely on sampling period h. As an alternative, so called integrating or averaging samplers are considered in [4,5,7,8]. In [4,5] we studied the impact of antialiasing filters for pure signal processing while in [6] in the discrete-time LQG control context, and we have found that there is no reason for using them in the noiseless case, and practically no use in the case of noisy measurements. The best results in the latter case are obtained when the continuous-time output is passed through a continuous-time Kalman filter before being sampled.…”

Frequency stabilized lasers for space applications

“…As is well known, any signal content above the Nyquist sampling rate become aliased. The standard approach of adding an analog anti-aliasing filter does not always improve performance 35,36 . The advantage of rolling off noise and resonant dynamics must be weighed against the added phase delay to the closed loop system and the loss in performance from this lag.…”