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 singleinput-single-output systems. This paper presents a new extension of the DOB idea to dual-input-single-output systems, and discusses an optimal Q-filter design. The proposed 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.