Motion Control Of Linear Servo System Of Air Bearing Precision Positioning Stage

Precision positioning stage can be widely used in the fields ofintegrated circuit and optical detection. As technology advances, therequirements for accuracy, speed and acceleration of the positioning stageare increasingly higher. Traditional rotary motor with ball screw structurehas been difficult to meet the demands. Due to the advantage of linearservo system’s structure, it can adapt to the high-speed and highacceleration occasions better. In recent years, linear servo systems havebeen found widespread used in these fields.Conventional linear servo systems typically use contact guide rail forlinear motor. Friction will be introduced into the systems inevitably. Andfriction force, as a complex non-linear phenomenon, has great impact onthe realization of precision positioning. Friction can be minimized by usingair bearing stage. Therefore, motion accuracy can be improved and it iseasier to achieve higher speed and acceleration. However, there are someinherent problems with air bearing system. Since there is no intermediatetransmission and it is almost zero damping in the direction of movement,the load disturbance, force ripple and other uncertain disturbance factorswill directly role in the output of the system. The motion performance ofthe stage will be affected.This dissertation focuses on the air bearing precision positioning stagefor optical detection, and studies the precision positioning control strategyof the linear servo system. Firstly, an experiment system with three axesand2-DOF, including its electrical control module, was build. The maingoal of the research is to achieve the performance requirements, such asthe positioning accuracy, speed of movement and stabilization time. The main contributions of this dissertation can be summarized as follows:1. With regard to the performance requirements, finished calculatingand selection of the hardware of the electromechanical systems.2. In according with relevant laws of physics, analyzed themechanism of the electrical system and concluded themathematical model of linear servo system. Designed systemidentification experiment and obtain model parameters from theexperiment. Provided the basis for controller design.Comprehensively analyzed the disturbance factors and theperturbation mechanism in order to design targeted controller tosuppress the disturbance.3. Designed the controller for single axis. By combination of cascadecontrol, feedforward control, disturbance observer and reasonabletrajectory planning, achieved the goal of point-to-point high-speedpositioning.4. Designed synchronous control strategy for gantry structure of thesystem. For the coupling effect of X-axis and Y-axis, builddynamic model of gantry structure and designed feedforwardcontroller based on the dynamic model. Mitigated multi-axis loaddisturbance.