Design and Research of a Variable Stiffness Compliant Joint Based on Torsional Spring

doi:10.3901/JME.2021.13.114

Abstract

Abstract: Human-robot safe interaction in unstructured environment can be realized by variable stiffness joints due to the intrinsic attribute of flexibility. A compact compliant joint with nonlinear stiffness is proposed at the change of pitch diameter of torsional spring, which is applicable to the common force scenario characterized by low load, low stiffness, high load and high stiffness. First, given the model design of the flexible joint with variable stiffness with torsional spring and the split sleeve as the basic elastic components, the position of the nut slider is adjusted to push the steel ball to squeeze the split sleeve and change the internal diameter of the torsional spring, thereby adjusting the stiffness of the joint. Second, the mechanical constitutive equation and the section stress distribution law of the elastic element in the joint model are analyzed and described according to the theory of elastic deformation, and the relations among the angle, torque and stiffness of the flexible joint are derived. Finally, the simulation data of torque and stiffness were obtained by rotating the joint to different angles and exerting different loads. The results show that the flexible joint is designed with effectiveness. At the same time, the research can serve as a theoretical reference for studying the mechanical behaviors of same type of torsional spring with variable stiffness.

Key words: compliant joint, torsional spring, variable stiffness, mechanical model

CLC Number:

TP242

QU Xiangxu, CAO Dongxing, ZHANG Shan. Design and Research of a Variable Stiffness Compliant Joint Based on Torsional Spring[J]. Journal of Mechanical Engineering, 2021, 57(13): 114-123.

References

[1] YU H, HUANG G, CHEN G, et al. Human-robot interaction control of rehabilitation robots with series elastic actuators[J]. IEEE Transactions on Robotics, 2015, 31(5):1089-1100.
[2] PAN Y, GAO F, QI C, et al. Human-tracking strategies for a six-legged rescue robot based on distance and view[J]. Chinese Journal of Mechanical Engineering, 2016, 29(2):219-230.
[3] XUE L, ZOU Y, HUANG J, et al. Constant speed control for complex cross-section welding using robot based on angle self-test[J]. Chinese Journal of Mechanical Engineering, 2014, 27(2):260-268.
[4] VANDERBORGHT B, ALBUSCHAEFFER A, BICCHI A, et al.Variable impedance actuators:A review[J]. Robot and Autonomous Systems, 2013, 61(12):1601-1614.
[5] R.V. HAM R V, SUGAR B, VANDERBORGHT K, et al. Compliant actuator designs[J]. IEEE Robot & Automation Magazine, 2009, 3(16):81-94.
[6] JAFARI A, TSAGARAKIS N G, VANDERBORGHT B, et al. A novel actuator with adjustable stiffness (Aw AS)[C]//International Conference on Intelligent Robots and Systems. Piscataway, USA:IEEE, 2010:4201-4206.
[7] JAFARI A, TSAGARAKIS N G, CALDWELL D G. A novel intrinsically energy efficient actuator with adjustable stiffness (AWAS)[J]. IEEE/ASME Transactions on Mechatronics, 2013, 18(1):355-365.
[8] JAFARI A, TSAGARAKIS N G, SARDELLITTI I, et al. A new actuator with adjustable stiffness based on a variable ratio lever mechanism[J]. IEEE/ASME Transactions on Mechatronics, 2014, 19(1):55-63.
[9] TSAGARAKIS N G, SARDELLITTI I, CALDWELL D G. A new variable stiffness actuator (Comp Act-VSA):Design and modelling[C]//IEEE/RSJ International Conference on Intelligent Robots and Systems. San Francisco, USA:IEEE, 2011:378-383.
[10] CHOI J, HONG S, LEE W, et al. A robot joint with variable stiffness using leaf springs[J]. IEEE Transactions on robotics, 2011, 27(2):229-238.
[11] 史延雷, 张小俊, 张明路. 主-被动复合变刚度柔性关节设计与分析[J]. 机械工程学报, 2018, 54(3):55-62.SHI Yanlei, ZHANG Xiaojun, ZHANG Minglu. Design and analysis of a active-passive variable stiffness flexible joint[J]. Journal of Mechanical Engineering, 2018, 54(3):55-62.
[12] 王伟, 刘立冬, 魏来, 等. 柔性齿条式变刚度关节驱动器设计与研究[J]. 机械工程学报, 2016, 52(1):26-33. WANG Wei, LIU Lidong, WEI Lai, et al. Design and Research of rack-based variable stiffness actuator[J]. Journal of Mechanical Engineering, 2016, 52(1):26-33.
[13] MIGLIORE S A, BROWN E A, DEWEERTH S P. Biologically inspired joint stiffness control[C]//IEEE International Conference on Robotics and Automation, Barcelona:IEEE, 2006:4508-4513.
[14] TONIETTI G, SCHIAVI R, BICCHI A. Design and control of a variable stiffness actuator for safe and fast physical Human/Robot interaction[C]//IEEE International Conference on Robotics and Automation, Barcelona:IEEE, 2005:526-531.
[15] ZHOU X, JUN S K, KROVI V. A cable based active variable stiffness module with decoupled tension[J], Journal of Mechanisms and Robotics, 2015, 7(1):1-5.
[16] CUI Z, PENG Y, QIAN D, et al. Design and modelling of a novel linkage mechanism based variable stiffness actuator[C]//Robotics and Biomimetics (ROBIO), Shenzhen:IEEE, 2013:97-102.
[17] HOLLANDER K W, SUGAR T G, GERRING D E. Adjustable robotic tendon using a ‘Jack Spring’^TM[C]//International Conference on Rehabilitation Robotics, Chicago:IEEE, 2005:113-118.
[18] PALLI G, BERSELLI G, MELCHIORRI C, et al. Design of a variable stiffness actuator based on flexures[J]. Journal of Mechanisms and Robotics-Transactions of the ASME, 2011, 3(3):034501.
[19] DRAGONI E, STROZZI A. Analysis of a split ring inserted into a circular housing[J]. Journal of Strain Analysis for Engineering Design, 1986, 21:59-70.
[20] 张英会, 刘辉航, 王德成. 弹簧手册[M]. 北京:机械工业出版社, 2008. ZHANG Yinghui, LIU Huihang, WANG Decheng. Springs handbook[M]. Beijing:China Machine Press, 2008.
[21] 曹东兴, 王强, 张琦, 等. 一种主-被动变刚度关节:中国, 201920259193.0[P]. 2019-10-29. CAO Donxing, WANG Qiang, ZHANG Qi, et al. The active-passive variable stiffness joint:China, 201920259193.0[P]. 2019-10-29.