Advanced Motion Control: An Industrial Perspective*

Industrial feedback motion controllers are tuned using manual loopshaping, according to certain design rules. This controller tuning serves as a benchmark for robust control research as applied to optical and magnetic disk drive storage systems. The design and implementation of robust controllers for the focus servo of a compact disk and the tracking servo of a hard disk mechanism is investigated. The design objective is to achieve good track-following performance in the presence of disk disturbances. H∞ robust control is used to systematically include disturbance and specification models in the standard plant framework. The control design iteration is based on disturbance identification, including implementation within the design cycle. The industrial relevance of robust control is discussed and areas for academic research in robust control are indicated, as feedback from industry.