Modeling of nonlinear dynamics at low frequencies in hard disk drive and its adaptive compensation

In hard disk drive servo system, the rejection of disturbances at low frequencies is degraded due to the nonlinearities of pivot friction and flex-cable bias. In this paper, a novel parametrized dynamic model is proposed with the parameters being functions of position. The proposed model provides good matching in both time domain and frequency domain. Based on this nonlinear parametrized model, a feedforward controller with adaptive gain is designed and implemented. The simulation and experimental results show that the proposed method can improve the servo performance effectively.