Digital control of dual actuator hard disk drive systems.

摘要

In this dissertation, we investigate the design of digital controllers for dual actuator hard disk drive systems. The dual actuator disk drive system consists of a coarse actuator (voice coil motor, VCM) and a fine actuator (piezoelectric transducer, PZT). Three aspects of dual actuator disk servo are studied: track following control, track settling and seeking control, and multi-rate control for computational saving.; First, the track following problem is addressed for dual actuator disk drive systems. We present the design of digital controllers for dual actuator servo systems and the analysis of their robust stability and performance. The design is divided into two steps. In the first step, the stability of the coarse actuator loop is an important consideration. In the second step, the fine actuator loop is designed by loop shaping for superior performance of the overall system. Robustness is studied by mu-analysis after the closed loop system is augmented with various weightings. Simulation and experimental results demonstrate the effectiveness of the proposed design.; Next, the track settling and seeking control is presented for the dual actuator hard disk drive system. The control design method is called the dual actuator reference trajectory re-design (RTRD). In RTRD, the original minimum jerk reference trajectory for VCM and another "redesigned" minimum jerk reference trajectory are combined to determine the reference trajectory for PZT for faster settling of the recording head on the target track. The RTRD is divided into three steps. In the first step, the coarse actuator controller is designed to be stable and achieve the basic performance. In the second step, the fine actuator controller is designed for superior performance of the overall system. Finally the reference signals are generated for both VCM and PZT actuators. Simulations and experimental results demonstrate the effectiveness of the proposed scheme.; Finally, multi-rate control is studied for computation saving. The dual actuator disk drive system involves two actuators, i.e. VCM and PZT, with different bandwidths, and the two feedback loops are closed at different rates: a fast rate for a high bandwidth PZT loop and a slow rate for a low bandwidth VCM loop. The slow rate VCM controller is further decomposed and interlaced so that computational saving by multi-rate control may be distributed uniformly at all fast rate sampling instances. The experimental results show that the multi-rate implementations achieve regulation performance of the position error signal at about the same level as the single-rate implementation while realizing significant computational saving.