Robust biaxial contouring controller design incorporating frictional dynamics

The performance of a contouring action is evaluated by the geometric deviation called contour error. By analysis, this error is significantly affected by coordination of axes, frictional effects and load variations. To improve the contouring performance, both the coordination control and the friction compensation should be incorporated into controller synthesis. Besides, friction forces are also found tending to vary quantitatively with position and time, which can be termed as parametric uncertainties in the friction modeling. Therefore, this paper provides an integrated structure such that all the factors can be combined into a single formulation, and a robust chattering-free output feedback sliding mode contouring controller design is proposed based on this formulation such that the coordination control, friction compensation, load variation and parametric uncertainties can be together solved by a systematic procedure. Numerical results with 20% system parametric uncertainties are shown consistent to the theoretical analysis, and reveal the effectiveness and the robustness of the proposed method.