Combined H2 and KYP lemma based control for positioning error minimization and specific narrowband disturbance rejections

A control design method which combines the generalized Kalman-Yakubovich-Popov (KYP) lemma and the H₂ control is proposed to attenuate specific narrowband disturbance and simultaneously minimize the positioning error of the control system. Two specific narrowband disturbance near the bandwidth are rejected sufficiently via the KYP lemma based design, and moreover the enhancement of the overall positioning accuracy of the control system is achieved via H₂ control design to minimize the positioning error. The proposed control design method is applied in the feedback servo loop design for a lead-zirconate-titanate (PZT) micro-actuator in hard disk drives (HDDs) to attenuate disturbances at 650 Hz and 2 kHz and also minimize the positioning error such that the system positioning accuracy is enhanced ultimately. Simulation and experimental results are shown and demonstrate the effectiveness of the proposed method.