Increased disturbance rejection in magnetic disk drives by acceleration feedforward control and parameter adaptation

As the density of data on magnetic disk drives increases, so does the need for more precise position control of the read/write head, especially in the presence of internal and external disturbances. This is achieved by measuring the acceleration of the drive and feeding the sensor information forward to the actuator. By matching the electromechanical impedance between the disturbance and the position error, the feedforward controller can cancel the effects of the disturbance. Two techniques are presented for designing the feedforward controller. The first method is an infinite impulse response filter that is designed off-line, and the second is a finite impulse response filter that is adapted on-line using the filtered-x LMS algorithm. Both techniques are tested through shake-table experiments, resulting in reductions of the position error signal between 50% and 95%. Copyright (C) 1997 Elsevier Science Ltd.