Repetitive controller design for minimum TMR in HDD

This paper presents a design method for repetitive controller in the sense of minimum TMR. For TMR prediction, disturbances acting on a disk drive are identified and servo performance is estimated using identification result. The validity of the identification and estimation procedure is proved through experiments. As a repetitive controller, an add-on type is adopted, and PID controller is used for base tracking controller. Each controller is optimized for minimum TMR. Whole system performance is simulated and design criterion is suggested. For improved response in both transient and steady state, two kinds of gain-switching method (discrete, continuous) are applied and switching effect also investigated.