A local toolpath smoothing method for a five-axis hybrid machining robot

Smooth transitions between two adjacent five-axis toolpaths can reduce feedrate fluctuation, improving machining quality and efficiency. Hybrid robots’ flexibility to adjust the orientation is advantageous in five-axis machining, but their kinematic issues raise challenges for toolpath smoothing. This paper proposes a G3 continuous toolpath smoothing method for a hybrid robot. B-splines in the machine coordinate system (MCS) are inserted at corners to synchronize five-axis transitions. The transition errors of the tool position and orientation paths are estimated with the golden section method. These approximation errors are constrained by adaptively modifying the B-splines, i.e., adding anchor points and optimizing the control points. A bisection search method is proposed for these geometric modifications, guaranteeing the user-defined error tolerance limit. Compared to the method based on the workpiece coordinate system (WCS), the proposed framework generates a smoother trajectory under the same error tolerance limit. Simulations and experiments are provided to validate the effectiveness.