ABSTRACT
Chapter 3 has presented the feedback controller design, simulation, and experimental testing results for the dual-stage actuation system with the thermal microactuator as the secondary actuator, and a 6 kHz servo bandwidth has been achieved. It is known that there is a saturation problem for microactuators, and the saturation will degrade the control system performance or even cause instability. The saturation occurs easily when the dual-stage actuators are doing long distance seeking or working under external vibrations such as large audio vibe. To help avoid the saturation, an enough stroke is thus required for microactuators. In this chapter, an anti-windup method is used to control the saturation as an additional compensation in the feedback loop. The anti-windup compensator will not affect the closed-loop system when there is no input saturation in the loop. In the presence of saturation in the loop, the anti-windup compensator can achieve good closed-loop performance as close as possible to the nominal linear control system, while the time period during which the control input is saturated is minimized. In this chapter, the anti-windup saturation compensator is designed via an LMI (linear matrix inequality) approach [1,2] based on the rigid part of the thermal microactuator only [3], and thus can be done separately from the basis feedback controller.
