Research on Nonlinear PID Position Controller of CNC System

Abstract

The position control arithmetic is crucial to the rapidity, stability and accuracy of CNC system. When adopting conventional PID position controller, the CNC system is difficult to obtain rapid response and satisfied overshoot at the same time because of the PID control coefficient invariance. A nonlinear PID position controller model is developed to achieve flexible control on CNC system in the paper, where the integral controlled quantity U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> expression and differential control efficient K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> are adjusted automatically along with the tracking error variation on the basis of analyzing the drawback of the conventional PID position controller in detail. The control simulation aimed at the typical step input signal shows that the developed nonlinear PID position controller can reduce the overshoot to zero, get rapid response and enhance the tracking performance of the CNC system in the meantime. The conclusion is significant to high speed and high accuracy CNC machining.