ABSTRACT
This chapter discusses dual-stage systems and control using a commercial Hard Disk Drive (HDD) as a classical example of high-performance mechatronic system without loss of generality. It describes the dual-stage system employing the Voice Coil Motor (VCM) as primary actuator and the suspension-based Lead-Zirconate-Titanate (PZT) active suspension as secondary actuator in an HDD. The chapter identifies the mathematical models of the VCM and PZT active suspension using continuous- and discrete-time measurements. It outlines the various methods of mechanical resonant modes compensation using gain-stabilization, inverse compensation, and phase-stabilization. The chapter presents the notion of multi-sensing servo systems where additional sensors and advanced control methodologies are used for active vibration control in dual-stage systems. It explores the various dual-stage control configurations, and an example of dual-stage control. For system identification of the VCM using continuous-time signals, a swept sine voltage excitation is generated from a Dynamic Signal Analyzer and is injected into the VCM via a current amplifier.
