Track-following control of hard disk drives using multi-rate sampled-data H∞ control

In hard disk drives (HDDs), the sampling period of a position error signal (PES) is restricted. Thus, the multi-rate control design has been a popular subject in HDDs. This paper proposes a design method of read/write head-positioning controller using multi-rate sampled-data H_∞ control theory. This method can design multi-rate controller directly considering inter-sample performance and robust stability. The structure of generalized plant and the selection of weighting functions are discussed. The obtained performance is compared with the single-rate sampled-data H_∞ controller and single-rate/multi-rate discrete-time H_∞ controller through experimentation.