Design and analysis of robust track-following controllers for dual-stage servo systems with an instrumented suspension

This paper discusses the design and analysis of two robust track-following controllers for a dual-stage servo system containing a MEMS microactuator and an instrumented suspension in hard disk drives. The first controller is designed using the so-called PQ method, which is a kind of sequential single-input/single-output (SISO) frequency shaping design techniques. Actuation interference is explicitly addressed in this design. The second controller is designed using a multi-objective optimization technique via linear matrix inequalities (LMIs). Stability robustness to plant uncertainty can be explicitly considered by imposing some H_∞ norm bounds. In both cases, compensation of airflow-excited suspension vibration is implemented first by using the strain sensor output from the instrumented suspension. Detailed analysis and comparison are carried out on system dynamics, robust stability, robust performance, and implementation complexity.