- The research investigates the design and performance capabilities of a voice-coil motor actuator (VCMA) for a disc drive with a nonlinear magnetic bias. A VCMA is designed to meet specific seek performance requirements. A nonlinear magnetic bias is independently designed to compensate for non-operational shock. A model-based adaptive controller was developed to meet the seek performance requirements and simultaneously handle effects of the nonlinear bias. The performance criteria was based on minimizing the time required for a seek maneuver without controller saturation. The proposed adaptive controller was compared to an often used linear state-feedback controller with the magnetic bias present. Simulations were conducted to verify the results.