Track-Following Control of Four-Bar Structured HDD via Parameter-Dependent Low-Frequency Precompensation

This paper considers track-following control of four-bar structured hard disk drive (HDD) systems. Compared with the traditional single-arm HDD, the four-bar structure potentially leads to higher achievable closed-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 constraints. In this paper, instead of exact linearization, we propose a kind of prefilter to compensate for the low-frequency nonlinearities so that the compensated system has the same linear approximation at different track positions subjected to different high-frequency resonances. With this prefilter, many existing track-following control methods can be applied to the compensated plant. In this paper, H_∞ loop shaping is used and simulation results show that the resulting controller preserves similar track-following performance at different track positions.