Low-hump sensitivity function design for dual-stage HDD systems with different microactuators

The paper focusses on a control design that aims to achieve a low hump sensitivity function for dual stage servo systems in hard disk drives. Two microactuator models are studied, a MEMS (microelectromechanical system) actuator and a PZT (piezoelectric) actuator. A nearly flat sensitivity function is accomplished in the continuous-time domain for the dual-stage servo loop using the H∞-loop shaping method and an LMI (linear matrix inequality) approach. The implementation result for the parallel dual-stage system with a PZT-actuated suspension demonstrates the effectiveness of the proposed design and the hump of the sensitivity function is shown to be lower than 3 dB.