Contour tracking control in position domain for CNC machines

A common problem with modern manufacturing processes that utilize high speed machining is the ability to accurately track a contour of the end-effector. Various control methods have been developed to increase axial tracking performance in the time domain. This paper discusses a new control method developed in the position domain, and the developed position domain control is applied to a 3-axis CNC machine for contour tracking purpose. In theory, the contour tracking of a position domain controller should be improved when compared to an equivalent time domain controller. This is the case since the tracking error of a reference axis in the position domain does not contribute to the overall contouring error. Simulation of the position domain controller and time domain controller yielded positive result for the position domain controller with improved contour tracking for both linear and circular end-effector motions.