VCNC CONTOUR FOLLOWING TASKS USING ROBUST QFT CONTROLLER

Document Type: Research Paper

Authors

1 Dept. of Mechanical Engineering, Mashhad Branch, Islamic Azad University, Mashhad, I. R. of Iran

2 Dept. of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, I. R. of Iran

Abstract

In this paper, the Quantitative Feedback Theory (QFT) is proposed to design a
controller for feed drive of Virtual Computer Numerical Control (VCNC) systems. The designed
robust 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 position
commands 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 robust
QFT controller and also FC and SMC controllers are designed to achieve the allowable tolerance
contour error. The simulation results for the "heart" and "omega" contour following tasks with the
aforementioned controllers were analyzed and discussed. It is found that the designed QFT
controller 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 contour
following applications in VCNC systems.

Keywords