Smoothness-oriented path optimization for robotic milling processes
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oothness-oriented path optimization for robotic milling processes 1
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PENG JingFu , DING Ye , ZHANG Gang & DING Han 1
State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China; 2 HUST-Wuxi Research Institute, Wuxi 214174, China Received December 12, 2019; accepted January 15, 2020; published online May 18, 2020
Industrial robots are increasingly used for five-axis machining operations, where the rotation of the end effector along the toolaxis direction is functionally redundant. This functional redundancy should be carefully resolved when planning the robot path according to the tool path generated by a computer-aided manufacturing (CAM) system. Improper planning of the redundancy may cause drastic variations of the joint motions, which could significantly decrease the machining efficiency as well as the machining accuracy. To tackle this problem, this paper presents a new optimization-based methodology to globally resolve the functional redundancy for the robotic milling process. Firstly, a global performance index concerning the smoothness of the robot path at the joint acceleration level is proposed. By minimizing the smoothness performance index while considering the avoidance of joint limits and the singularity and the constraint of the stiffness performance, the resolution of the redundancy is formulated as a constrained optimization problem. To efficiently solve the problem, the sequential linearization programming method is employed to improve the initial solution provided by the conventional graph-based method. Then, simulations for a given tool path are presented. Compared with the graph-based method, the proposed method can generate a smoother robot path in which a significant reduction of the magnitude of the maximum joint acceleration is obtained, resulting in a smoother tool-tip feedrate profile. Finally, the experiment on the robotic milling system is also presented. The results show that the optimized robot path of the proposed method obtains better surface quality and higher machining efficiency, which verifies the effectiveness of the proposed method. robot milling, functional redundancy, path optimization, smoothness, sequential linear programming Citation:
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Peng J F, Ding Y, Zhang G, et al. Smoothness-oriented path optimization for robotic milling processes. Sci China Tech Sci, 2020, 63, https://doi.org/ 10.1007/s11431-019-1529-x
Introduction
Recently, industrial robots (IRs) are increasingly used for machining applications in industries due to advantages of large workspace, great flexibility, and relatively low cost [1–3]. However, the market share of the IRs for machining is still poor compared to that of IRs for repetitive tasks such as handling and palletizing. One important reason is that the programming of IRs for machining applications is much more complex compared to that for pick-and-place opera*Corresponding author (email: [email protected])
tions [4]. When IRs are applied to a 5-axis machining task, the robot path is
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