VCNC CONTOUR FOLLOWING TASKS USING ROBUST QFT CONTROLLER

Abstract

In this paper, the Quantitative Feedback Theory (QFT) is proposed to design acontroller for feed drive of Virtual Computer Numerical Control (VCNC) systems. The designedrobust QFT controller is also compared to two commonly used controller design methods, i.e.Fuzzy Control (FC) and Sliding Mode Control (SMC), for contour tracking problem. The positioncommands required for contour following task are evaluated by the Non-Uniform Rational BSpline(NURBS) curve interpolator with the S-shape feedrate profile for two contours, i.e. "heart"and "omega" as the case studies. After modeling the feed drive of the VCNC system, the robustQFT controller and also FC and SMC controllers are designed to achieve the allowable tolerancecontour error. The simulation results for the "heart" and "omega" contour following tasks with theaforementioned controllers were analyzed and discussed. It is found that the designed QFTcontroller not only achieves the tight contour error but also yields better satisfactory performance,especially at the corners of the tool path, compared to the other controllers used in contourfollowing applications in VCNC systems.