Track-following control of four-bar structured HDD via parameter-dependent pre-compensation

This paper considers track-following control of four-bar structured hard disk drive systems. Compared with the traditional single-arm HDD, four-bar structure potentially leads to higher achievable close-loop bandwidth, but also brings challenges in control design due to nonlinearity. In track-following control design, exact linearization is impossible in practice due to mechanic resonances and measurement constraint. In this paper, instead of exact linearization, we propose a kind of pre-filter to compensate for the low-frequency nonlinearities so that the compensated system has the same linear approximation at different track positions subject to different high-frequency resonances. With this pre-filter, many existing track-following control methods can be applied to the compensated plant. In this paper, H-infinity loop shaping is used and the simulation results show that the resulting controller preserves similar track-following performance at different track positions.