Designing controllers for two stage disk drive actuator systems using the PQ method and the sbode plot

The PQ method is a technique for transforming the problem of designing controllers for dual-input/single-output (DISO) systems to two single-input/single-output (SISO) design problems, and the sbode plot is a new modification of the traditional bode plot which facilitates loop shaping design for SISO systems. This paper shows how to employ the two tools to meet aggressive closed-loop performance specifications for a disk drive system with a piezoelectric active suspension and a voice coil motor.