Model Reduction and Parametric Uncertainty Identification for Robust H2 Control Synthesis for Dual-Stage Hard Disk Drives

This paper presents a systematic, semi-automated method for identifying parameters and parametric uncertainty for a set of dual-stage hard disk drives. A modal analysis technique is selected to extract parameters from a batch of frequency response data. In order to avoid redundancy in modal parameters, two methods are presented to reduce model order. One method combines experimental data to directly extract fewer parameters. The second method uses an optimized model truncation methodology. Finally, convex optimization and singular value decomposition are employed to obtain a minimally conservative, lower-order approximation of uncertain parameters. The result is a reduced-order state space model with parametric uncertainty to be used in robust H₂ control synthesis for a track-following hard disk drive servo.