A novel contouring error estimation method for contouring control

Contouring error estimation is the basis of contouring control. In this paper a novel computationally efficient contouring error estimation method for contouring control is presented that eliminates sudden change of contouring error vector directions that are encountered by traditional contouring error estimationmethods in regions of large curvature. The proposed new method first localizes the large curvature regions by identifying sudden changes in the number of backward steps between the current reference position and the nearest reference position to the actual position. It then modifies the contouring error vectors to smoothly sweep through the corner. Experiments were conducted on an X-Y table to compare the proposed method with two existing methods and study the effects of the sampling interval on the proposed method. In these experiments, the proposed method eliminated the sudden change of contouring error vector directions in large curvature regions. Moreover, the method was also applied to a cross coupled controller where it drew the actual trajectory closer to the reference trajectory while simultaneously reducing the second derivative of the contouring error vectors.