机器人的几何参数误差导致其绝对定位精度较差，会制约其在离线编程方面的应用。协作机器人关节刚度小，受其自重和末端负载的影响柔性变形大，会进一步降低其定位精度。针对该问题，对相邻3轴（2~4轴）平行型协作机器人展开运动学标定方法研究，并面向工程实际开发了相应的标定软件。首先，提出一种非线性的几何参数辨识模型，并利用模型非线性方程组的逆函数原理进行模型冗余性分析；进一步建立关节刚度辨识模型；考虑到几何参数辨识和关节刚度辨识是互相干扰的，提出一种基于迭代思想的综合辨识方法。应用该方法对UR5机器人进行标定实验，实验结果显示，标定后机器人空载和负载时的绝对定位精度相比标定前分别提高75.5%和85.1%，验证了本文标定方法的有效性。
The geometric parameter error of robot leads to its poor absolute positioning accuracy, which restricts its application in off-line programming. The joint stiffness of the collaborative robot is small, so its flexible deformation is largely affected by its self-weight and end load, which further reduce its positioning accuracy. Aiming at this problem, the kinematics calibration method of adjacent three-axis parallel(2-4 axis) cooperative robot is studied, and the corresponding calibration software is developed to apply the method to engineering practice. Firstly, a nonlinear geometric parameter identification model is proposed, and the redundancy of the model parameters is analyzed by using the inverse function principle of the model's nonlinear equations. Further, a joint stiffness identification model is established. Considering the mutual interference between geometric parameter identification and joint stiffness identification, a comprehensive identification method based on iterative thought is proposed. The calibration experiment of UR5 robot is carried out using this method. The experimental results show that the absolute positioning accuracy of the robot under no-load and load after calibration is improved by 75.5% and 85.1%, respectively, compared with that before calibration, which verifies the effectiveness of the calibration method in this paper.
[1] 侯士杰.工业机器人结构参数辨识与位姿误差补偿研究[D].南京:南京航空航天大学,2012. DOI:CNKI:CDMD:2.1014.005829.
[2] Judd R P, Knasinski A B. A technique to calibrate industrial robots with experimental verification[J]. IEEE Transactions on Robotics and Automation, 1990, 6(1):20-30. DOI:10.1109/70.88114.
[3] Veitschegger W K, Wu C H. Robot calibration and compensation[J]. IEEE Journal on Robotics and Automation, 1988, 4(6):643-656. DOI:10.1109/56.9302.
[4] Grotjahn M, Daemi M, Heimann B. Friction and rigid body identification of robot dynamics[J]. International Journal of Solids and Structures, 2001, 38(10/11/12/13):1889-1902.DOI:10.1016/S0020-7683(00)00141-4.
[5] Renders J M, Rossignol E, Becquet M, et al. Kinematic calibration and geometrical parameter identification for robots[J]. IEEE Transactions on Robotics and Automation, 1991, 7(6):721-732. DOI:10.1109/70.105381.
[6] Kim D H, Cook K H, Oh J H. Identification and compensation of a robot kinematic parameter for positioning accuracy improvement[J]. Robotica, 1991,9(1):99-105.DOI:10.1017/s0263574700015617.
[7] 田聚峰, 王攀峰, 刘世博, 等.考虑关节刚度的轻型模块化机器人标定方法[J].机械科学与技术,2018,37(8):1217-1222.DOI:10.13433/j.cnki.1003-8728.20180015.
[8] Abele E, Weigold M, Rothenbücher S. Modeling and identification of an industrial robot for machining applications[J]. CIRP Annals, 2007, 56(1):387-390. DOI:10.1016/j.cirp.2007.05.090.
[9] Dumas C, Caro S, Cherif M, et al. Joint stiffness identification of industrial serial robots[J].Robotica, 2012,30(4):649-659.DOI:10.1017/s0263574711000932.
[10] 芮平, 乔贵方, 温秀兰, 等.串联6自由度机器人关节刚度辨识与误差补偿研究[J].机械传动,2019, 43(6):37-42.DOI:10.16578/j.issn.1004.2539.2019.06.007.
[11] 张晓平.六自由度关节型机器人参数标定方法与实验研究[D].武汉:华中科技大学,2013. DOI:10.7666/d.D608509.
[12] 铁隆正. "工业4.0"环境下的人机协作机器人[J].电器工业,2015(8):62-63. DOI:10.3969/j.issn.1009-5578.2015.08.025.
[13] Siciliano B, Khatib O. Springer handbook of robotics[M]. 2nd ed. Berlin:Springer, 2016. DOI:10.1007/978-3-319-32552-1.
[14] Meggiolaro M A, Dubowsky S. An analytical method to eliminate the redundant parameters in robot calibration[C]//Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings (Cat. No.00CH37065). April 24-28, 2000, San Francisco, CA, USA.IEEE, 2000:3609-3615.DOI:10.1109/ROBOT.2000.845294.
[15] 奥特加,莱因博尔特. 多元非线性方程组迭代解法[M]. 朱季纳译. 北京:科学出版社, 1983.
[16] 中华人民共和国国家质量监督检验检疫总局, 中国国家标准化管理委员会. 工业机器人性能规范及其试验方法:GB/T 12642-2013[S]. 北京:中国标准出版社, 2014.
