Local asymmetrical corner trajectory smoothing with bidirectional planning and adjusting algorithm for CNC machining

• Published in: Robotics and computer-integrated manufacturing Vol. 68; p. 102058
• Main Authors: Wang, Weixin, Hu, Chuxiong, Zhou, Kai, He, Suqin, Zhu, Limin
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2021; Elsevier BV
• Subjects: Algorithms; Asymmetrical corner smoothing; Asymmetry; Bidirectional planning and adjusting; Cornering; Cycle time; Deceleration; Exact solutions; Jerk limit; Machine shops; Machine tools; Machining; Numerical controls; Short-segmented toolpath; Smoothing; Structural vibration; Trajectory generation; Trajectory planning; Bidirectional planning and adjusting; Trajectory generation; Asymmetrical corner smoothing; Jerk limit; Short-segmented toolpath
• ISSN: 0736-5845; 1879-2537
• DOI: 10.1016/j.rcim.2020.102058

•Analytical asymmetrical corner trajectory smoothing that can realize accelerated/decelerated cornering transition.•Be able to generate same trajectories at corresponding corners of Zigzag paths.•Propose bidirectional planning and adjusting algorithm, and prove its feasibility.•Generate a jerk-limited trajectory, while respecting the user-specified tolerance. The linear motion command (G01) is a widely used command format in CNC machining. However, the tangential direction discontinuity at the corner junction will cause velocity fluctuations and excite the structural vibration of machine tools. Corner smoothing methods with controlled tolerance are used to obtain continuous smooth motion. Typically, most methods generate a symmetrical cornering trajectory around the angle bisector, and the trajectory generally decelerates first and then accelerates, which limits the velocity increase. In this paper, a novel local asymmetrical corner trajectory smoothing method is proposed, which can realize accelerated/decelerated cornering transition. The proposed method can obtain the analytical solution in one step, which is different from two-step geometric-based corner path smoothing, and can generate the same cornering trajectory in back-and-forth parallel toolpath. In addition, this paper proposes a bidirectional planning and adjusting algorithm for the situation where smoothed cornering paths are close to each other or even overlap. The algorithm can generate a jerk-limited trajectory by coordinating the cornering error of adjacent corners, while respecting the user-specified tolerance. Experimental results demonstrate the effectiveness of the proposed method in contour accuracy and cycle time for CNC machining along short-segmented toolpath.