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Design of a novel auxiliary standing knee exoskeleton with variable stiffness

Published online by Cambridge University Press:  16 October 2025

Gong Cheng Open the ORCID record for Gong Cheng [Opens in a new window] ,
Yanjiang Huang ,
Kai Wang Open the ORCID record for Kai Wang [Opens in a new window]  and
Xianmin Zhang
Gong Cheng
Affiliation:
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou, China Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, South China University of Technology, Guangzhou, China
Yanjiang Huang*
Affiliation:
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou, China Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, South China University of Technology, Guangzhou, China
Kai Wang
Affiliation:
School of Mechatronics Engineering and Automation, Foshan University, Foshan, China
Xianmin Zhang
Affiliation:
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou, China Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology, South China University of Technology, Guangzhou, China
*
Corresponding author: Yanjiang Huang; Email: mehuangyj@scut.edu.cn
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Abstract

With increasing age, many elderly individuals will not be able to stand normally. To solve this problem, a knee exoskeleton is designed. The knee joint is designed as a variable stiffness structure. It can adjust its stiffness according to the body’s movement state, ensuring precise assistance while also enhancing human comfort. The variable stiffness mechanism consists of an elastic output actuator and a stiffness-adjusting actuator. The elastic output actuator is mainly responsible for the output of the joint torque. The stiffness-adjusting actuator is mainly responsible for adjusting the joint stiffness. These two mechanisms are analysed separately. Based on their relationship with the whole mechanism, a stiffness model of the entire knee joint is established. Experiments are subsequently conducted to evaluate the variable stiffness joint. The stiffness identification experiment indicates that the actual stiffness of the whole knee joint is essentially consistent with the theoretical value. The trajectory tracking experiment demonstrates that the joint exhibits excellent trajectory tracking capability, although stiffness has a certain effect. The exoskeleton assistive effect experiment demonstrates the ability of the exoskeleton to assist in standing. Additionally, the experiment on subjects with exoskeletons of different stiffnesses determines the impact of stiffness on human comfort.

Keywords

exoskeletonvariable stiffnesssit to standstiffness identificationtrajectory tracking

Information

Type
Research Article
Information
Robotica , First View , pp. 1 - 18
Copyright
© The Author(s), 2025. Published by Cambridge University Press

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References

Lin, D. and Cui, J., “Transport and mobility needs for an ageing society from a policy perspective: Review and implications,” Int. J. Environ. Res. Public Health 18(22), 11802 (2021).CrossRefGoogle ScholarPubMed
Chuy, O., Hirata, Y., Wang, Z. and Kosuge, K., “Approach in Assisting a Sit-to-Stand Movement Using Robotic Walking Support System,” In: 2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE (2006) pp. 4343–4348.Google Scholar
Kim, S.-W., Song, J., Suh, S., Lee, W. and Kang, S., “Design and Experiment of a Passive Sit-to-Stand and Walking (STSW) Assistance Device for the Elderly,” In: 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), IEEE (2018) pp. 1781–1784.Google Scholar
Hou, C., Chen, Q., Chen, P., Li, X. and Li, K., “Brain-machine interaction and assist effect evaluation of a single-degree-of-freedom sit-to-stand transfer robot,” Robotica 43(7), 2644–2673 (2025).10.1017/S0263574725101781CrossRefGoogle Scholar
Hiyama, T., Kato, Y. and Inoue, T., “Sit-to-Stand Assistance System Based on Using EMG to Predict Movement,” In: 2017 26th IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN), IEEE (2017) pp. 81–87.Google Scholar
Bettella, F., Tortora, S., Menegatti, E., Petrone, N. and Felice, A. D., “A scoping review on lower limb exoskeleton actuation’s description and characteristics,” Robotica 43(4), 1572–1589 (2025).10.1017/S0263574725000220CrossRefGoogle Scholar
Arefeen, A. and Xiang, Y., “Subject specific optimal control of powered knee exoskeleton to assist human lifting tasks under controlled environment,” Robotica 41(9), 2809–2828 (2023).CrossRefGoogle Scholar
Eguchi, Y., Kadone, H. and Suzuki, K., “Standing mobility device with passive lower limb exoskeleton for upright locomotion,” IEEE/ASME Trans. Mechatronics 23(4), 1608–1618 (2018).CrossRefGoogle Scholar
Daines, K., Lemaire, E. D., Smith, A. and Herbert-Copley, A., “Sit-to-Stand and Stand-to-Sit Crutch Use for Lower Extremity Powered Exoskeletons,” In: 2017 IEEE International Symposium on Robotics and Intelligent Sensors (IRIS), IEEE (2017) pp. 358–363.Google Scholar
Sarkisian, S. V., Gunnell, A. J., Foreman, K. B. and Lenzi, T., “Knee Exoskeleton Reduces Muscle Effort and Improves Balance During Sit-to-Stand Transitions After Stroke: A Case Study,” In: 2022 International Conference on Rehabilitation Robotics (ICORR), IEEE (2022) pp. 1–6.Google Scholar
Furukawa, J.-I., Okajima, S., An, Q., Nakamura, Y. and Morimoto, J., “Selective assist strategy by using lightweight carbon frame exoskeleton robot,” IEEE Robot. Autom. Lett. 7(2), 3890–3897 (2022).10.1109/LRA.2022.3148799CrossRefGoogle Scholar
Huo, W., Mohammed, S., Amirat, Y. and Kong, K., “Active Impedance Control of a Lower Limb Exoskeleton to Assist Sit-to-Stand Movement,” In: 2016 IEEE international conference on robotics and automation (ICRA), IEEE (2016) pp. 3530–3536.Google Scholar
Nesler, C., Thomas, G., Divekar, N., Rouse, E. J. and Gregg, R. D., “Enhancing voluntary motion with modular, backdrivable, powered hip and knee orthoses,” IEEE Robot. Autom. Lett. 7(3), 6155–6162 (2022).10.1109/LRA.2022.3145580CrossRefGoogle ScholarPubMed
Zhou, L., Chen, W., Chen, W., Bai, S., Zhang, J. and Wang, J., “Design of a passive lower limb exoskeleton for walking assistance with gravity compensation,” Mech. Mach. Theory 150, 103840 (2020).CrossRefGoogle Scholar
Kimura, M., Pham, H., Kawanishi, M. and Narikiyo, T., “EMG-Force-Sensorless Power Assist System Control Based on Multi-Class Support Vector Machine,” In: 11th IEEE International Conference on Control & Automation (ICCA), IEEE (2014) pp. 284–289.Google Scholar
Choi, G., Lee, D., Kang, I. and Young, A. J., “Effect of Assistance Timing in Knee Extensor Muscle Activation During Sit-to-Stand Using a Bilateral Robotic Knee Exoskeleton,” In: 2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), IEEE (2021) pp. 4879–4882.Google Scholar
Chen, B., Zhong, C.-H., Ma, H., Guan, X., Qin, L.-Y., Chan, K.-M., Law, S.-W., Qin, L. and Liao, W.-H., “Sit-to-stand and stand-to-sit assistance for paraplegic patients with cuhk-exo exoskeleton,” Robotica 36(4), 535–551 (2018).10.1017/S0263574717000546CrossRefGoogle Scholar
Shepherd, M. K. and Rouse, E. J., “Design and Characterization of a Torque-controllable Actuator for Knee Assistance During Sit-to-Stand,” In: 2016 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), IEEE (2016) pp. 2228–2231.Google Scholar
Shepherd, M. K. and Rouse, E. J., “Design and validation of a torque-controllable knee exoskeleton for sit-to-stand assistance,” IEEE/ASME Trans. Mechatronics 22(4), 1695–1704 (2017).CrossRefGoogle Scholar
Kamali, K., Akbari, A. A. and Akbarzadeh, A., “Trajectory generation and control of a knee exoskeleton based on dynamic movement primitives for sit-to-stand assistance,” Adv. Robotics 30(13), 846–860 (2016).10.1080/01691864.2016.1154800CrossRefGoogle Scholar
Pfeifer, S., Vallery, H., Hardegger, M., Riener, R. and Perreault, E. J., “Model-based estimation of knee stiffness,” IEEE Trans. Biomed. Eng. 59(9), 2604–2612 (2012).CrossRefGoogle ScholarPubMed
Sun, J., Guo, Z., Sun, D., He, S. and Xiao, X., “Design, modeling and control of a novel compact, energy-efficient, and rotational serial variable stiffness actuator (SVSA-II),” Mech. Mach. Theory 130, 123–136 (2018).10.1016/j.mechmachtheory.2018.07.024CrossRefGoogle Scholar
Li, Z., Chen, W., Zhang, J., Li, Q., Wang, J., Fang, Z. and Yang, G., “A novel cable-driven antagonistic joint designed with variable stiffness mechanisms,” Mech. Mach. Theory 171, 104716 (2022).10.1016/j.mechmachtheory.2021.104716CrossRefGoogle Scholar
Zhu, Y., Wu, Q., Chen, B., Zhang, Q. and Wu, H., “Adaptive command filter backstepping sliding mode control for variable stiffness exoskeleton with input saturation constraint,” IEEE Trans. Instrum. Meas. 73, 1–12 (2024).Google Scholar
Zhu, Y., Wu, Q., Chen, B., Zhao, Z. and Liang, C., “Physical human–robot interaction control of variable stiffness exoskeleton with sEMG-based torque estimation,” IEEE Trans. Ind. Inform. 19(10), 10601–10612 (2023).10.1109/TII.2023.3240749CrossRefGoogle Scholar
Zhu, Y., Wu, Q., Chen, B., Xu, D. and Shao, Z., “Design and evaluation of a novel torque-controllable variable stiffness actuator with reconfigurability,” IEEE/ASME Trans. Mechatronics 27(1), 292–303 (2021).10.1109/TMECH.2021.3063374CrossRefGoogle Scholar
Liu, L., Hong, Z., Penzlin, B., Misgeld, B. J. E., Ngo, C., Bergmann, L. and Leonhardt, S., “Low impedance-guaranteed gain-scheduled geso for torque-controlled vsa with application of exoskeleton-assisted sit-to-stand,” IEEE/ASME Trans. Mechatronics 26(4), 2080–2091 (2020).CrossRefGoogle Scholar
Zhou, Y., Shao, Y., Di, S., Feng, Y., Ding, X. and Zhang, W., “Design and preliminary validation of a compatible lower limb exoskeleton with variable stiffness actuation,” Robotica 43(5), 1675–1690 (2025).10.1017/S0263574725000451CrossRefGoogle Scholar