The effectiveness of contouring control and a design for three-dimensional machining

Although many researches have been conducted on contouring control for machine tool feed drive systems, to the best of authors’ knowledge, its effectiveness has been verified only through comparative experiments with industrial non-contouring (independent axial) controllers, or conventional contouring controllers such as the cross-coupling controller. Because control performance largely depends on controller gains, such comparisons involve some difficulties in demonstrating the effectiveness of contouring control. In other words, a similar control performance can be achieved if the non-contouring controller gains are appropriately assigned. This paper discusses the effectiveness of contouring controllers both analytically and experimentally. A new contouring controller design for three-dimensional machining is presented, which is extended from the authors’ biaxial design based on coordinate transformation. The contouring controller is concluded to be effective through an analysis of the proposed design, in that it provides performance comparable to non-contouring controllers with less control input variance. This property reduces the damage to machine tool systems and saves control energy. In addition, because an inherent contour error exists in the coordinate transformation approach, a method for reducing this error is presented to enhance the effectiveness of the contouring controller. Experimental results support the claims of this paper.