Motion controller design for contour-following tasks based on real-time contour error estimation

Reduction of contour error is an important issue in contour-following applications. One of the common approaches to this problem is to design a controller based on contour error information. However, for the free-form contour-following tasks, there is a lack of effective algorithms for calculating contour errors in real time. To deal with this problem, this paper proposes a real-time contour error estimation algorithm. In addition, a motion control scheme that combines a position loop controller (which utilizes a velocity command feedforward) with a tangential-contouring controller (TCC) is employed to improve the contour-following accuracy. When implementing the TCC, a coordinate transformation matrix is needed. Unfortunately, it is difficult to calculate the coordinate transformation matrix when performing the free-form contour-following task. To overcome this difficulty and facilitate the use of contour controllers, a systematic approach is employed to derive the coordinate transformation matrix for the free-form contour-following tasks. Experimental results demonstrate the effectiveness of the proposed contour error estimation algorithm and the motion control scheme.