Adaptive IMC design for HDD servo control

Controllers are designed based on mathematical models of the system to be controlled. In HDD systems, the modeling errors may come from mechanical resonance modes, different operating conditions, variations in actuator parameters from drive to drive, model simplification, etc. The modeling error leads to certain performance deterioration, and may even cause system instability. In order that a robust performance would be demonstrated not only in the nominal system, but also in the real system, an internal model control (IMC) structure based on a traditional state feedback controller is proposed in this paper. The traditional MRA method is modified, and low-pass filters have been introduced in the MRA scheme to handle the high frequency mechanical modes and disturbances.