Phase stabilized design of a hard disk drive servo using the complex lag compensator

This paper introduces a new technique for the phase stabilized design (PSD) of a HDD servo, based on the use of complex lag compensators. Such compensators have several benefits compared to standard ones and they offer additional degrees of freedom in control design. This paper presents a case study comparing the performance of the PSD using the complex lag compensator with the performance of a PID plus notch filter design, and the performance of a PSD using a real lag compensator. The designs are performed for a realistic model of a disk drive derived from experimental data. The new approach significantly outperforms the other with respect to step response, rejection of disturbance response at the plant input, and rejection of periodic and windage disturbances.