基于人行走能耗分析的踝关节外骨骼设计

Design of Ankle Exoskeleton Based on Analysis on Energy Cost of Human Walking

基于对人体行走的能耗分析,设计了一种新型有源无动力踝关节外骨骼。首先,基于耦合摆模型建立人体行走摆动相动力学方程并采用打靶法求解。根据动量守恒原理分别计算摆动腿膝关节锁定、脚跟着地以及关节摩擦引起的能耗率。计算结果表明,脚跟着地引起的能耗率远大于膝关节锁定和关节摩擦引起的能耗率。然后,基于该能耗分析结果设计了一种足底弹性储能机构将脚跟着地时的能耗存储起来,在跖屈蹬地阶段释放助力。通过前脚掌压力信号控制电磁铁驱动的离合机构,实现对助力弹簧夹紧与释放的状态切换。样机实验结果表明:足底储能机构可以提高外骨骼的输出力矩和功率,提升助行能力;外骨骼的最大输出力矩为19N·m;穿戴该外骨骼行走时小腿三头肌激活度相较于不穿戴时最大下降约8.6%。踝关节角度测量结果表明,在摆动相期间外骨骼很少干扰穿戴者踝关节的正常活动。

A new type of active unpowered ankle exoskeleton is designed based on the analysis on the energy cost of human walking.Firstly, dynamical equations of swing phase of human walking are built based on a coupled pendulum model and shooting method is used to solve the equations. Energy cost rate of knee-lock, heel-strike and joint friction of the swing leg are calculated based on the principle of momentum conservation. The calculation results show that the energy cost rate of heel-strike is much greater than the energy cost rate resulted from knee-lock and joint friction. Then, based on the results of analysis of the energy cost, an plantar elastic storage mechanism is designed to store the energy cost of heel-strike, which is released during the plantar flexion push-off phase.Pressure signals from forefoot are used to control the clutch mechanism driven by electromagnet, the clamping and releasing states switching of assistive spring is achieved. Experimental results of the prototype shown that plantar energy storage mechanism can increase the output torque and power of the ankle exoskeleton, enhance the ability of assisting walking. The maximum output torque is 19 Nm. The muscle activity of the triceps surae is reduced by 8.6% when wearing the exoskeleton compared with the state without wearing the exoskeleton. The measurement results of ankle joint angle show that the exoskeleton rarely interferes with the normal range of motion of the wearer’s ankle during swing phase.