DISC DRIVE MODEL REFERENCE SEEK ALGORITHM

Herein is disclosed a method and apparatus for controlling the excitation of a servomechanism in a disc drive with a low frequency stimulus, yet necessitating the control system to include only a model of the servomechanism's response to having been excited by a high frequency stimulus (square-wave). The invention uses a square wave as a feedforward input signal. This feedforward input signal is low-pass filtered and used as a stimulus to excite the servomechansim, during seek operations. The response of the servomechanism is measured at intervals. The response of the servomechanism is predicted, by a servomechanism model, as if the servomechanism had been excited by the feedforward square-wave signal, rather than its filtered counterpart. The predicted response of the servomechanism is then filtered, using a similar low-pass filter. The difference between filtered modeled responses and the measured responses are used to subsequently adjust the signal that stimulates the servomechanism.