Robust H2 Synthesis for Dual-stage Multi-sensing Track-following Servo Systems in HDDs

This paper presents a robust H₂ synthesis technique for designing a track-following servo system for a hard disk drive (HDD) product line. The goal is to design a single robust controller that minimizes the worst case H₂ performance of an entire disk drive product line, assuming that dynamic variations in the product line (i.e. variations from one unit to another) are accurately characterized by affine variations in several of the actuator´s model parameters, such as variations in the resonance frequency or damping ratio of a resonance mode. The advantages and disadvantages of the proposed method are discussed and an illustrative realistic example is presented