Preview Control Of Dual-Stage Actuators System

As one of the high precision devices, the dual-stage actuators system (DSA) has drawn world-wide interest in recent years due to its advantages such as high precision, large route, strong robustness and so on. It has been successfully applied in high precision engineering including mechanical hard discs, electronic scanners, grating machine and miniature robots and so on. With the development of science and technology, more and more high precision are required. Nowadays the storage capacity of disks increase exponentially and the gap between the tracks becomes smaller and smaller, so the problems come:how to improve the positioning accuracy and positioning speed of head. In the21century when the nanotechnology become hottest research point, how to improve the scan accuracy of electronic scanner. These problems need to be solved. In this article, the positioning speed and scan accuracy of the dual-stage actuators system are improved by taking the preview control into the system. Through getting future movement and disturb information, and using these information to compensate, the properties of the controlled object have been improved. It could achieve better results than traditional control. This article focuses on the two common applications of the dual-stage actuators, the preview control was designed in to the positioning and scan, and the positioning speed and scan accuracy of the system are improved, the details are below:1The introduction of the dual-stage actuators system’s theories, characteristics and applications and the show of importance of a two-stage driver in the field of precision engineering. Analysis the common structure of a dual-stage driver and summarize the advantages and disadvantages of decoupling structure of dual stage actuators system.2Building physical model of the dual-stage actuators system driver, eliminating the impact of the primary actuator’s friction and nonlinear factor through model reference control and building the primary actuator’s model close to the double integral model, then the algorithm of the primary actuator can be simple.3A fast positioning method based on preview control of the dual-stage driver was proposed at the first time. The primary actuator tracks the known future reference, and the secondary actuator compensates the tracking error of the primary actuator. When the tracking error of the primary actuator is kept in the range of the secondary actuator, the output of the entire dual-stage actuators system will be stabilized at target value. Appling the thought of approximate optimal time control, the flutter near the target value can be eliminated.4A high accuracy scan method of the dual stage actuators system based on preview control is proposed at the first time. When the primary actuator tracks triangle wave, the minimization of the largest error can be achieved. Because that the tracking error of the primary actuator is reduced to12.5%of the value that the non-preview control shows, the output of the secondary actuator will not be saturated during it compensates the tracking error of the primary actuator. It can improve not only the scan accuracy but also the scan speed of the dual-stage actuators system. In the field of high precision scanning instruments, the algorithm has a wide application prospects.