A Comparison of Multi-Objective Servo Controller Synthesis Methodologies in Dual-Stage Hard Disk Drives

This work provides a comprehensive comparison of four mixed H2-H∞-optimal control synthesis methodologies for dual-stage hard disk drives (HDD). Combinations of the commonly-used H2 and H∞ objective functions and constraining metrics on the voice-coil motor (VCM), piezoelectric (PZT) actuator, and the position error signal (PES) drive the comparative analysis to better understand the control tradeoffs involved in their choice. The controllers are given identical design inputs and are synthesized using linear-matrix-inequality-based optimization. A simulated disturbance environment is used to analyze the closed-loop frequency response, and demonstrate the performance and benefits of each control method. This work demonstrates where each of the constraint metrics excel, which serves as a basis for tailored design based on the need of the HDD control engineer.