Modeling And Coordinating Control Research Of A Dual-stage Actuator System

With the development of information technology, biological technology, ultra-precisionmachining technology and so on, the higher requirement to achieve precision positioning withinthe scope of big trip on drive feeding technology is put forward. The dual-stage actuator(DSA)system combines the traditional actuator which is of long travel range with thesmart-material-based actuator which is of high precision. Meanwhile, it effectively solves thecontradiction between the long travel and high precision.In this dissertation, the mathematical models are established and the controllers aredesigned for the first actuator and the second actuator respectively, and the two actuators areunited through a coordination factor, the major works include:(1) The mathematical model is established and the controller is designed for the firstactuator.The first actuator uses conventional servo motor. Via the analysis of the physicalcharacteristics and driving method, the mathematical model is built. The controller design isbased on proximate time-optimal servomechanism. Then the preview control algorithm is addedto the first controller to reduce the redundancy between the first actuator and the second actuator.The simulation results illustrate the practicability of the proposed method.(2) The mathematical model is established and the controller is designed for the secondactuator.The second actuator system is divided into known and unknown control direction.Hysteresis phenomenon which is non-smooth and multi-valued mapping in smart-material-basedactuators is also considered in this dissertation. The Bouc-Wen model is employed to describehysteresis phenomenon for the nonlinear system with known control direction. A backsteppingcontroller combining with error transformation is proposed. First, the prescribed performancefunction is used to confine the error to residual set with variable property in Bouc-Wen modelexplored. Then the output error transformation is introduced to transform the original constrainedsystem into an equivalent unconstrained one. Finally, a backstepping controller is designed forthe hysteresis systems. For a class of nonlinear systems with hysteresis and unknown controldirection, a hysteretic operator is developed to construct an expanded input space so as totransform the multi-valued mapping of hysteresis into a one-to-one mapping which enables neural networks to model the hysteresis. RBF neural networks are used to approximate theunknown functions and the unknown control direction is solved by Nussbaum function. Finally,error transformation is used to confine the error to a predefined residual set and a adaptivecontroller is proposed based on backstepping technique. The control schemes can not onlyguarantee the tracking accuracy, but also improve the transient and steady-state performance.The simulation results show that the control scheme is feasible.(3) The coordinating controller is designed for the DSA system.A coordination factor is designed to realize the coordination of two actuators and overcomethe default of long setting time caused by designing separated controllers for the DSA system.The adjustable parameter of the coordination factor is selected by the integrated performanceindex. To demonstrate the effectiveness of this scheme, we simulate this scheme, the resultsshow that can reduce the setting time effectively.