| Optimization Design |
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| Design and optimization of a passive exoskeleton mechanical foot |
| REN Meng-yi1, CAO En-guo2, ZHAO Yong-wu1, YANG Bin2, CUI Yu-tian2 |
1.School of Mechanical Engineering, Jiangnan University, Wuxi 214122, China;
2.School of Design, Jiangnan University, Wuxi 214122, China |
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Abstract Passive exoskeleton can reduce walking energy consumption for human and doesn't require electric energy, it has a wide range of applying prospect in military and civilian fields. Aiming at the problem that existing passive exoskeleton saves less energy and cannot adapt to different walking configurations, the multi-level energy lock principle was proposed and a passive exoskeleton mechanical foot was designed according to this principle. Based on multi-level energy lock principle, human-machine coupling ADAMS (automatic dynamic analysis of mechanical systems) dynamics models during energy storing phase and energy releasing phase in support phase during human walking were established. Subsequently, the passive exoskeleton mechanical foot was optimized: based on the dynamics models, the effect of two structure parameters including the spring position and spring release angle on the assist performance of the mechanical foot was analyzed, and the optimal values of the parameters were obtained by combining the heel height. Based on walking experiment and finite element analysis, the strength, stiffness, smoothness and comfort of the passive exoskeleton mechanical foot were optimized. After the optimization, the mass of the mechanical foot was reduced 500 g, the safety factor reached 3.04, smoothness and comfort had a comprehensive improvement. The research showed that the energy releasing phase was the key phase for the exoskeleton mechanical foot to play a role; spring release angle had a significant effect on the assist performance of the mechanical foot during the energy releasing phase, and thus became a key parameter affecting the assist performance of the mechanical foot. This research will provide an important reference for exoskeleton design.
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Received: 08 November 2018
Published: 28 April 2020
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一种被动式外骨骼机械足的结构设计及优化
被动式外骨骼可以减少行走能量消耗且不耗费电能，在军事、民用领域具有广阔的应用前景。针对现有被动式外骨骼节省的能量较少且无法适应不同行走配置等问题，提出了多级能量锁原理，并根据此原理设计了一款被动式外骨骼机械足。首先，基于多级能量锁原理，建立人体行走时支撑相储能阶段和释能阶段的人机耦合ADAMS(automatic dynamic analysis of mechanical systems，机械系统动力学自动分析)动力学模型。然后，对被动式外骨骼机械足进行了优化：基于所建立的动力学模型分析了弹簧位置和弹簧释放角度这2个结构参数对机械足助力性能的影响规律，并结合足跟高度求得了这2个参数的最优解。最后，基于行走实验和有限元仿真分析，对被动式外骨骼机械足的强度、刚度、流畅性和舒适性等进行了优化，优化后机械足的质量约减轻500 g，安全系数达到了3.04，运行流畅性和舒适性显著提升。结果表明，释能阶段是被动式外骨骼机械足发挥作用的关键阶段；弹簧释放角度对释能阶段机械足助力性能的影响较为显著，即为影响机械足助力性能的关键参数。研究结果可为外骨骼设计提供重要参考。
关键词：
被动式外骨骼,
结构设计,
动力学,
优化,
助力性能
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