Design Analysis of Quasi-passive Variable Stiffness Assisted Exoskeleton with Ankle

doi:10.3901/JME.2025.15.196

Abstract

Abstract: In order to reduce the torque generated during plantar flexion of the human ankle and alleviate leg muscle fatigue, a quasi passive variable stiffness ankle assisted exoskeleton is designed. By using plantar pressure signals to control the electromagnetic clutch, energy storage and release of the energy storage unit are achieved. Firstly, the variable stiffness mechanism adjusts the preload force of the assist spring through geometric structure, achieving non-linear joint output stiffness and reducing energy consumption during human walking. Secondly, a simulation model of human ankle exoskeleton wearing is established, and dynamic simulation is conducted to verify the rationality of the exoskeleton mechanical structure and its good assistance effect. Finally, an experimental platform for testing the function of ankle assisted exoskeletons is established, and the performance of the variable stiffness energy storage mechanism is tested. The results showed that the average EMG signals of the tibialis anterior muscle and gastrocnemius muscle decreased by 12.29% and 39.26% after wearing exoskeletons, indicating that wearing exoskeletons effectively reduces muscle fatigue and provides a new method for the design of wearable exoskeletons.

Key words: quasi-passive, variable stiffness, ankle assistance, exoskeleton design, reduce fatigue

CLC Number:

TG156

TANG Xinyao, YANG Jiayin, WANG Xupeng, YIN Rong, LIU Xiaoyi. Design Analysis of Quasi-passive Variable Stiffness Assisted Exoskeleton with Ankle[J]. Journal of Mechanical Engineering, 2025, 61(15): 196-208.

References

[1] BASTIEN G J,WILLEMS P A,SCHEPENS B,et al.Effect of load and speed on the energetic cost of human walking[J]. Eur. J. Appl. Physiol.,2005,94(1-2):76-83.
[2] 黄彬鑫.搬运助力外骨骼结构设计与仿真分析[J].装备制造技术,2022(4):57-60.HUANG Binxin. Structural design and simulation analysis of handling-assisted exoskeleton[J]. Equipment Manufacturing Technology,2022(4):57-60.
[3] TANG X,WANG X,JI X,et al. A wearable lower limb exoskeleton:Reducing the energy cost of human movement[J]. Micromachines,2022,13(6):900.
[4] CHEN J,HAN J,ZHANG J. Design and evaluation of a mobile ankle exoskeleton with switchable actuation configurations[J]. IEEE/ASME Transactions on Mechatronics,2022,27(4):1846-1853.
[5] 曾德政,吕继亮,屈盛官,等.基于SVMBP的下肢外骨骼步态检测及识别研究[J].机械工程学报,2022,58(12):29-38.ZENG Dezheng,LÜJiliang,QU Shengguan,et al.Research on gait detection and recognition of lower limb exoskeleton based on SVMBP[J]. Journal of Mechanical Engineering,2022,58(12):29-38.
[6] 郑凯,刘利利,王永奉,等.无动力下肢外骨骼机器人研究综述及发展趋势[J].机械传动,2021,45(4):166-176.ZHENG Kai,LIU Lili,WANG Yongfeng,et al. Research summary and development trend of unpowered lower limb exoskeleton robot[J]. Mechanical Transmission,2021,45(4):166-176.
[7] WANG X,GUO S,QU B. et al. Design of a passive gait-based ankle-foot exoskeleton with self-adaptive capability[J]. Chinese Journal of Mechanical Engineering,2020,33(1):49.
[8] CHANG Y,WANG W,FU C. A lower limb exoskeleton recycling energy from knee and ankle to assist push-off[J].Journal of Mechanisms and Robotics,2020,12(5):1-17.
[9] 何谦,郁祉杰,叶礼贤,等.下肢外骨骼柔性踝关节设计及助力研究[J].机械工程师,2024(3):1-5.HE Qian,YU Zhijie,YE Lixian,et al. Design of flexible ankle of lower limb exoskeleton and research on its assistance[J]. Mechanical Engineer,2024(3):1-5.
[10] YANDELL M B,TACCA J R,ZELIK K E. Design of a low profile,unpo wered ankle exoskeleton that fits under clothes:overcoming practical barriers to widespread societal adoption[J]. IEEE Transactions on Neural Systems and Rehabilitati on Engineering:A Publication of the IEEE Engineering in Medicine and Biology Society,2019,27(4):298-302.
[11] SUTRISNO A,BRAUN D J. Enhancing mobility with quasi-passive variable stiffness exoskeletons[J]. IEEE Transactions on Neural Systems and Rehabilitation Engineering:A Publication of the IEEE Engineering in Medicine and Biology Society,2019,27(3):76-87.
[12] VAN CREY N,CAVALLIN M,SHEPHERD M,et al.Design of a quasi-passive ankle-foot orthosis with customizable,variable stiffness[C]//2023 International Conference on Rehabilitation Robotics (ICORR),2023:1-6.
[13] 王颜,房立金.机械式仿骨骼肌变刚度机构原理及设计[J].机器人,2015,37(4):506-512.WANG Yan, FANG Lijin. Principle and design of mechanical skeletal muscle-like variable stiffness mechanism[J]. Robot,2015,37(4):506-512.
[14] SAURAV K,MATTHEW Z. Extremum seeking control for stiffness auto-tuning of a quasi-passive ankle exoskeleton[J]. IEEE Robotics and Automation Letters,2020,25:99.
[15] 白子兴,曹旭含,孙承颐,等.步态周期中踝关节有限元模型的构建及生物力学分析[J].中国组织工程研究,2022,26(9):1362-1366.BAI Zixing, CAO Xuhan, SUN Chengyi, et al.Construction of finite element model of ankle in gait cycle and biomechanical analysis[J]. China Tissue Engineering Research,2022,26(9):1362-1366.
[16] LEE M,KIM J,HYUNG S,et al. A compact ankle exoskeleton with a multi-axis parallel linkage mechanism[J]. IEEE/ASME Transactions on Mechatronics,2021,26,191-202.
[17] 王伟,丁建全,汪毅,等.踝关节外骨骼助行模式对下肢肌肉激活与协调模式的影响[J].生物医学工程学杂志,2022,39(1):92-98.WANG Wei,DING Jianquan,WANG Yi,et al. Effect of ankle exoskeleton on lower limb muscle activation and coordination[J]. Journal of Biomedical Engineering,2022,39(1):92-98.
[18] SUTHERLAND D H. The evolution of clinical gait analysis Part II kinematics[J]. Gait&Posture,2002,16(2):159-179.
[19] CHEN Z,GUO Q,XIONG H,et al. Control and implementation of 2-DOF lower limb exoskeleton experiment platform[J]. Chinese Journal of Mechanical Engineering,2021,34(1):22.
[20] 曹恩国,徐祺,沈峰岑,等.多运动复合型被动式下肢外骨骼设计及其智能交互评估[J].机械工程学报,2023,59(11):43-53.CAO Enguo,XU Qi,SHEN Fengcen,et al. Multi-motion compound passive lower limb exoskeleton design and its intelligent interaction evaluation[J]. Journal of Mechanical Engineering,2023,59(11):43-53.