Direct Contour Error Compensation for Biaxial Contouring Control Systems Based on a Global Fixed Coordinate Frame

In the tasks of contour following, two important issues are required to be concerned. They are the real-time contour error estimation and compensation. Recent research shows that the accuracy of real-time contour error estimation can be improved by the approach of circular approximation. However, in such an approach, the estimated contour error is calculated from the artificial moving coordinate frame and has to be transformed back to the fixed coordinate frame for compensation. In this paper, an approach to estimate and compensate the real-time contour error based on the global fixed coordinate frame is proposed. In this method, the real-time contour error can be obtained from the tracking error decomposition to the global fixed coordinate frame via a projection map. Based on this estimation, direct contour error compensation will be performed with respect to the global fixed coordinate frame through modifying the reference position inputs. Experiments show that the estimation accuracy of the direct tracking error decomposition is the same as that of the circular estimation and the tracking performance of the contouring system is evidently improved after the compensation.