A C3 continuous toolpath corner smoothing method for a hybrid machining robot

Abstract

A high-order continuity of a five-axis toolpath helps avoid problems such as equipment resonance, allowing high-quality and high-efficiency machining to be achieved. This paper presents a semi-analytical C3 continuous toolpath corner smoothing method for a 5-DOF (degree of freedom) hybrid robot. Based upon curvature derivative continuity conditions, the tool position and orientation paths can be directly smoothed by inserting quintic B-splines. Benefitting from an analytical error expression, orientation error can be accurately predicted and controlled with improved computational efficiency. Then, by converting the remaining position and orientation segments into the specially designed 7th-degree B-spline, the C3 continuity of the geometrically smoothed toolpath is mathematically guaranteed without iterative calculations. Additionally, a path adjustment strategy is developed to enhance the performance of the proposed approach. Finally, simulations and experiments are carried out on the TriMule-800 mobile robot machining system by incorporating a jerk-continuous feedrate profile. The feasibility of the proposed approach in addressing a general five-axis toolpath is verified.