Preview control of dual-stage actuators

The vast majority of control theory has focused on the stability of dynamical systems as opposed to their performance, a consequence of the fact that an unstable system may be considered an engineering disaster. However, it is according to how well a system performs that it is defined as good or bad, making stability a necessary, but not sufficient condition for a successful design. Any closed loop system should simultaneously achieve the necessary stability property along with the desirable performance criteria. In motion control, performance criteria commonly concerns the system’s ability to accurately and promptly track a desired reference. Of paramount importance towards the improvement of both these goals was the development of the Dual-Stage Actuators (DSA) concept. This thesis exposes the author's and collaborators work on the development of new control methods that improve the DSA ability to promptly transition its output from one reference level to another. The main achievements of this work include the design and control of a novel DSA prototype, the development of new fast tracking servomechanisms focused on improving the performance of the slow actuator, and a novel integrated design that fully explores the redundancy of actuators. The integrated DSA control design makes use of future information in order to compute a pair of inputs to be applied before the output transition time, hence, it came to be known as Preview Control. The author hopes the material presented in this thesis will show that the integration of the novel fast tracking servomechanisms with the Preview Control strategy provides remarkable performance improvements to dual-stage systems. Experimental results are presented throughout the thesis in order to clarify and validate the proposed designs.