Abstract
Exoskeletons have been widely used in the field of human body function enhancement, and the application scenarios of exoskeletons have gradually diversified. The current application environment is characterized by high mobility, long periodicity, and uncertainty. To adapt to these characteristics, in the present study, an active and passive control system for a variable-stiffness knee exoskeleton based on a shape memory alloy (SMA) is developed. To enhance the mobility of the knee exoskeleton, the stiffness adjustment function is realized by SMA wires. To adapt to the long periodicity of application scenarios, the passive control mode is constructed, during which the exoskeleton drives human legs. Moreover, to address the uncertainty of the application scenarios, the active control mode is constructed, during which the exoskeleton follows the human leg movement when the wearer is in an irregular movement state. A gait recognition system is used to switch between the active and the passive control modes. Based on the prototype, a comprehensive experimental verification of the control system was carried out. The experimental results show that the constructed control system can realize the active and passive control function. In addition, the variable-stiffness function of the knee exoskeleton has the effect of reducing the driving error in scenarios with high mobility requirements.
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All data, models generated or used during the study are available from the corresponding author by request.
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Acknowledgments
This work was supported in part by the National Natural Science Foundation of China (61873045) and in part by the Fundamental Research Funds for the Central Universities (DUT20LAB303).
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Jiaqi Zhang and Ming Cong conceived and designed the study. Dong Liu, Yu Du, and Hongjiang Ma performed the experiments. Jiaqi Zhang and Dong Liu wrote the paper. Ming Cong, Jiaqi Zhang, Yu Du, Dong Liu, and Hongjiang Ma reviewed and edited the manuscript. All authors read and approved the manuscript.
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All code generated or used during the study are available from the corresponding author by request.
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Zhang, J., Cong, M., Liu, D. et al. Design of an Active and Passive Control System for a Knee Exoskeleton with Variable Stiffness Based on a Shape Memory Alloy. J Intell Robot Syst 101, 45 (2021). https://doi.org/10.1007/s10846-021-01319-z
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DOI: https://doi.org/10.1007/s10846-021-01319-z