Tradeoffs in Anti-aliasing Notch Filter Design for Multi-rate Digital Servo Systems

This paper presents a data-driven frequency-domain notch filter optimization framework to mitigate aliasing effect in multi-rate control systems. The plants are assumed to be experimentally-measured frequency response data. The process for quantifying the aliasing effect in the form of folding error is formulated. The optimization problem is then outlined, aiming at minimizing the phase loss introduced by the multi-rate notch filters subject to an upperbound on the magnitude of the folding error. A population of 100 hard disk drive micro-actuator plant data is adopted as a case study to demonstrate the effectiveness of the proposed method. The data are also used to demonstrate various tradeoffs in the design objectives and variables, including the relations between phase retention and aliasing mitigation, robustness and performance, as well as computational burden and performance. The proposed method provides a practical solution for optimal multi-rate notch filter design for digital servo systems.