Federico Marcassa

Track-following control with active vibration damping of a PZT-actuated suspension dual-stage servo system

This paper discusses the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration-damping controller is designed using the Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.

Hard disk drive with voltage-driven voice coil motor and model-based control

The paper presents a novel approach for driving a voice coil motor (VCM) in a hard disk drive (HDD), based on an adaptive voltage driver. The adaptation of the driver compensates for the variations of VCM resistance and is performed either during seek operations and track following. As a result, the performance of the proposed driver matches closely that of a standard current driver

Track-Following Control with Active Vibration Damping of a PZT-Actuated Suspension Dual-Stage Servo System

In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration damping controller is designed using Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.

Disturbance rejection in hard disk drives with multi-rate estimated state feedback

Multi-rate control has been proposed as a solution to improve the performance of Hard Disk Drives (HDDs) head servo positioning. Some authors report unexpected decrease in performance when using this approach. This paper presents an analytical method to obtain the closed-loop sensitivity function of a multi-rate control system, with estimated state feedback. By using this tool, it is shown why disturbance rejection in multi-rate control may be worse than in single-rate. The paper reports both simulation and experimental results, confirming the possible decrease in performance, when using a standard design for the multi-rate control, even when a first-order hold is used. The paper also presents a novel design procedure for the multi-rate estimator, which takes into account the spectral distribution of disturbances and yields to a better performance, compared to both single-rate and standard multi-rate control.

Disturbance Rejection in Hard Disk Drives with Multi-Rate Estimated State Feedback

Abstract Multi-rate control has been proposed as a solution to improve the performance of Hard Disk Drives (HDDs). Some authors report unexpected decrease in performance when using this approach. This paper presents an analytical method to obtain the closed loop sensitivity function of a multi-rate control system, realized through estimated state feedback. By using this tool, it is shown how disturbance rejection in multi-rate control may be worse than in single-rate. The paper reports both simulation and experimental results, which confirm the possible decrease in performance.