DECOUPLED DISTURBANCE OBSERVERS FOR DUAL-INPUT-SINGLE-OUTPUT SYSTEMS WITH APPLICATION TO VIBRATION REJECTION IN DUAL-STAGE HARD DISK DRIVES

The disturbance observer (DOB) has been one effective robust control approach for servo enhancement in single-input-single-output systems. This paper presents a new extension of the DOB idea to dual-input-single-output sys-tems, and discusses an optimal Q-filter design. The pro-posed decoupled disturbance observer (DDOB) provides a flexible approach to use the most suitable actuators for compensating disturbances at different frequencies. Such a scheme is helpful, e.g., for modern dual-stage hard disk drives, where enhanced servo design is becoming more and more essential in the presence of audio vibrations.