Fast High Precision Position Control Of Servo System Driven By Linear Motor With High Acceleration

High-speed and high-precision motion is one of the most important techniques in electronic manufacturing machines. In IC packing, with the reduction in chip size and the increase in productivity, it needs higher acceleration, higher velocity and higher precision, which challenges designing such controllers with high performance.This dissertation analyzes the motion of the IC packaging machines first to find out that it is a repetitive fast motion between two points with high acceleration and high position accuracy, while the requirement for tracking error during the motion is modest. Thus it can be regarded as a repetitive fast point-to-point motion. Then indices about the point-to-point motion are proposed. At last, based on a servo system with high acceleration, an X-Y position platform driven by linear motors, some controllers are proposed to make the platform position quickly with high precision.The key factors on fast high-precision position control of high-acceleration systems are the inertia and the outside disturbances, since that the inertia slows down the system's response and the disturbances degrade the position accuracy. Work in this dissertation is mainly about how to deal with these two factors. The controllers designed and the results are described as follows. 1. An adaptive controller is used to decide feedforward control effort for compensating the effects of the inertia, fiction and load force, while a robust sliding controller is utilized to suppress other disturbances. Combining the adaptive controller and the robust sliding one, an adaptive robust sliding controller is proposed. The adaptive controller and the robust sliding one are decoupled and thus can be designed independently. In point-to-point motion experiments, stable position error is less than 5 microns with no overshoot.2. The point-to-point motion is divided into two stages, one is the high-speed motion and the other is the high-precision positioning. In the high-speed motion stage, with the help of an iterative learning algorithm which decides the switch position, a bang-bang controller is utilized to make full use of the motor to accelerate or decelerate the platform, thus eliminates the slowing-down effects of the inertia. Subsequently, a sliding controller is designed to suppress disturbances in the high-precision positioning stage. Combing these two controllers leads to the iterative learning variable structure controller. Experiment results show it takes 67ms to move 4mm with the position error less than 5 microns and the response is of no overshoot.3. A cascaded controller with with PI controller in velocity loop and P controller in position loop is used to suppress the disturbances. During the motion the cascaded controller keeps unchanged while the reference command is adjusted by A-type ILC cycle by cycle to compensate the effects of the inertia and the disturbances. That is, a reference adjustment control algorithm is proposed and it is suitable for the case in which machines allow users do no manipulation on the controller except decide the controller parameters and the desired motions. In point-to-point motion experiments, an S-motion profile with the maximum acceleration 4.07g and the maximum velocity 0.4mm/ms is generated first, and then the platform is driven to track such reference command. Results show that it takes 31ms to move 4 mm with position error being less than 2 microns.4. A P+A-ILC controller is designed for systems whose relative order is 2. It combines P controller and A-type ILC. A-ILC is used to compensate for the effects of the inertia and the repetitive disturbances, while P controller is to suppress the non-repetitive disturbances. Compared to the related papers in literatures, P+A-ILC is more robust and the parameters can be chosen more easily. In point-to-point motion experiments, an S-motion profile with the maximum acceleration about 8.15g and the maximum velocity 0.48mm/ms is generated first, and then the platform is driven to track such reference command. Results show that it takes 27ms to move 4 mm with position error being less than 3 microns, which almost reaches to the performance limit.This dissertation gives the general control strategies to deal with the inetia and the outside disturbances, i.e., the two key fators on fast high-precision position control of high-acceleration systems. And then based on the control strategies, four controllers are designed. It is hopeful that the achievement will support the further research on high-speed and high-precision motion control in electronic manufacturing machines.