Stiffness analysis and optimization in robotic drilling application

• Published in: Precision engineering Vol. 49; pp. 388 - 400
• Main Authors: Bu, Yin, Liao, Wenhe, Tian, Wei, Zhang, Jin, Zhang, Lin
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.07.2017
• Subjects: Aircraft assembly; Drilling; Industrial robot; Processing performance index; Stiffness optimization; Processing performance index; Drilling; Industrial robot; Stiffness optimization; Aircraft assembly
• ISSN: 0141-6359; 1873-2372
• DOI: 10.1016/j.precisioneng.2017.04.001

•The main outcome of this work is mainly on the relationship between robot stiffness properties and drilling hole quality.•A Cartesian compliance model is proposed to describe the robot stiffness in Cartesian space. Based on the compliance model, quantitative evaluation index of robot processing performance is defined.•By choosing a proper drilling posture, performance index in cutting tool direction is optimized.•From the perspective of robot processing mechanism, the key role of per-load pressing force is first indicated. By applying per-load pressing force, performance index on machining plane is improved, which leads to better hole diameter accuracy. Low stiffness characteristics limit the application of industrial robots in the field of precision manufacturing. This paper focuses primarily on the stiffness properties of drilling robots by further studying the stiffness ellipsoid model. A Cartesian compliance model is proposed to describe the robot stiffness in Cartesian space. Based on the compliance model, a quantitative evaluation index of the robot’s processing performance is defined. By choosing a proper drilling posture, the performance index in the cutting tool direction is optimized. Higher accuracy of the countersink depth and hole axial direction can be guaranteed. From the perspective of the robot processing mechanism, the key role of the per-load pressing force is first indicated. By applying a per-load pressing force, the performance index on the machining plane is enhanced. Hole diameter accuracy is improved significantly. A stiffness improving factor used to evaluate the stiffness promotion degree is also proposed. Finally, experiments were conducted to verify the correctness of the proposed model. Drilling experiments were performed to investigate the effectiveness of the robot processing performance index improving methods The principle of pressing force used in engineering applications is given based on processing parameters.