High speed contouring control of biaxial systems based on task polar coordinate frame

Contouring control based on task coordinate frames (TCF) can improve the contouring performance directly by strengthening the tracking capability along contour-following direction. A novel task polar coordinate frame (TPCF) is proposed for the biaxial system contouring control, based on circular approximation. Compared with the classical TCF using tangent line approximation, TPCF can achieve more accurate contouring error estimation for free-form contours. The controller is designed in TPCF via linearizing the transformed error dynamics which is strong coupling and nonlinear. Different dynamics are assigned to the radial (representing the contour following direction) and the angular (representing the trajectory tracking direction) with a strong emphasis on minimizing the contouring error. Experiments on an XY-stage verified that TPCF based contouring control could decrease the contouring error much more evidently compared with classical TCF based, especially in high speed and/or large curvature cases.