Compensation of VCM Actuator Pivot Friction Based on an Operator Modeling Method

The pivot friction of voice-coil-motor (VCM) actuator is measured for a 1.8-in small disk drive with disk rotating and slider flying. The measurement is carried out under the conditions that the actuator is controlled and the head movement amplitude is growing by changing the references. The hysteresis of friction versus head position is then obtained. An operator-based modeling approach is adopted for the hysteresis, and an optimal model is obtained by minimizing the energy gain between the head position and the modeling error. It is also found that the frequency response of the actuator model with the inclusion of the hyteresis model matches well with the measured frequency response of the actuator. A friction compensation method based on the nonlinear hysteresis model is thus proposed. The simulation and implementation results demonstrate a significant improvement in disturbance rejection at low frequencies.