Positioning control of XY table

Ong, Yee Teng (2014) Positioning control of XY table. Project Report. UTeM. (Submitted)

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Abstract

In this project, the design of a two-degree-of-freedom (2-DOF) PID controller for an AC Servo Ball Screw Driven XY table is considered. XY table is commonly used in CNC machines and other industries which emphasizes motion control especially point-to-point (PTP) and tracking positioning control. XY table has the advantage of being low cost and high availability. Many types of controllers had been designed for positioning control of XY table. The most common type of controller is 1-DOF conventional type PID controller. This controller has satisfactory performance and simple structure. However, in most cases, 1-DOF PID controller can only achieve either good set-point response or good disturbance response. Thus, 2-DOF PID controller which is easy to design yet can achieve both good set-point response and good disturbance response is introduced. A 2-DOF PID controller is designed in this project for accurate tracking purpose. The effectiveness of 2-DOF PID controller is validated at the end of project too. 2-DOF PID controller is controller that has two tuning elements, which means more tuning parameters. The 2-DOF PID controller is designed using two-steps-tuning-method. Disturbance response are optimized by tuning parameters of Kp, Ti, and T0 using Ziegler-Nichols 2nd method, followed by optimization of set-point response by tuning of 2-DOF parameters, a and f3. Tracking control performance of 2-DOF PID controller is evaluated by comparing with PI and 1-DOF PID controller. The effectiveness of 2-DOF PID controller in tracking control is validated by examining sinusoidal inputs of different frequency and amplitude in experiments. Maximum absolute error, sum of absolute error, and mean square error are analyzed for all tracking performance of compensated system. Result shows that tracking error compensation (set-point response) of l~DOF PID controller is better than 2-DOF PID controller. However, this is due to tuning of a and f3 parameters in simulation in this project. a and f3 values should be tuned experimentally. Disturbance response of 1-DOF PID and 2-DOF PID are almost similar due to same Kp, Ti, and T0 values are used in both controllers.

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