Maxtor Corporation

Scott E Chase

Randall C Bauck

James W Hargarten

Jim Hargarten

Gary Counts

An actuator control loop for controlling head position in a rotating media data storage system. The invention applies the compensation zero to the PES prior to summing it with the integrator. This scheme reduces transients caused by the integrator initialization step because the zero does not 'see' the integrator initialization step. Transients that can result from coupling the integrator initialization to the zero can cause overshoot and ringing in the actuator, increasing settling time and reducing system performance. The present invention also provides a first sample velocity compensation scheme that removes the velocity correction factor from the PES signal in the first sample after a seek. This significantly reduces settling time and improves system performance. In one embodiment, the microprocessor of the present invention calculates a velocity compensation factor based on the PES signal. This signal is then superimposed on the integrator output. In another embodiment, the zero is moved during the first sample after a seek, so that no velocity correction is undertaken. In subsequent sample periods, the zero is returned to its desired frequency.

Actuator servo compensation method

An automatic digital control system includes a proportional integral derivative (PID) compensator in which the digital differentiator portion, with its associated zero-order hold, is implemented according to an algorithm that reduces phase loss as a function of frequency. The digital differentiator is based only on a present error sample so that the output of the digital differentiator (with its ZOH) is made to resemble an amplitude-balanced step function (i.e., a doublet) during a given sample period T. The step transition occurs at one-half of the period (i.e., at T/2). Another embodiment further reduces phase loss by confining the output waveform of the differentiator to some fraction of the total sampling period. During the remaining portion of the sampling period the digital differentiator (again, with its associated ZOH) is forced to some desired reference level.

Growing community of inventors

Longmont, CO, United States of America

Scott E Chase