Experimental Verification of Dynamic Contour Error Estimation for High-Precision Contouring of Two-Axis Servo-Systems

High-precision contouring is important in machining. A practically proven method to improve contouring precision is adding a cross-coupling algorithm, which acts on contour error, to the existing position control loops. The contour error estimate (CEE) significantly affects performance of the cross-coupling algorithm. Conventional CEE methods rely on static single-point algorithms. A Newton-based CEE algorithm which effectively improves CEE and dramatically reduces contouring error has recently been proposed [22]. In this paper, instead of a separate cross-coupling control it is proposed to modify the position control loops, in this case integral sliding mode control, to incorporate the contour error in the control loop. Various experiments to identify the effect of 1) number of required iterations of the Newton-based CEE, 2) reference feedrate and curvature, and 3) sharp corners on overall performance of the proposed cross-coupling algorithm are reported. The experimental setup includes a two-axis servo-system. Control and estimation algorithms are implemented on two sbRIO 9632 from National Instruments.