Design and Optimization of Human-machine Compatibility of Knee-ankle Exoskeletons

doi:10.3969/j.issn.1004-132X.2025.10.026

Abstract

Abstract:

To address the challenges of poor compatibility in current exoskeletons and human legs， a knee-ankle exoskeleton was designed based on human-machine compatibility. The spatiotemporal data of lower limb joint movements were collected through a motion capture system. A four-bar mechanism with a J-shaped motion trajectory that might adapt to the instantaneous center of human knee joint movement was designed based on the physiological characteristics of knee joint rolling and sliding motions. A linkage mechanism optimization design method for simulating knee joint motions was proposed. The optimized four-bar mechanism was validated through numerical simulation to fit human motion well. The development of an power-assisted exoskeleton control system was achieved by combining angle sensors， and the effectiveness of the power-assisted exoskeleton performance was verified through gait and electromyography experiments. The experimental results show that the peak change in knee joint angle after wearing is less than 5%， the knee joint torque decreases， and the activity of muscles such as the lateral thigh muscle， gastrocnemius muscle， and biceps longus muscle decreases.

Key words: knee and ankle joint, knee transient, power-assisted exoskeleton, human-machine coupling simulation analysis, experimental validation

摘要：

针对现有外骨骼与人体腿部协调性差的问题，设计了一种基于人机匹配性的膝踝关节外骨骼。通过动作捕捉系统采集下肢关节运动的时空数据，结合生理膝关节滚滑运动特性，设计了能够适应人体膝关节运动瞬心的J字形运动轨迹的四杆机构，提出了模拟膝关节运动的连杆机构优化设计方法。数值模拟验证了优化后四杆机构能够很好地贴合人体运动，结合角度传感器实现了助力外骨骼控制系统的开发，进而借助步态和肌电实验对助力外骨骼性能有效性进行了验证。实验结果表明，穿戴后膝关节角度峰值变化幅度小于5%，膝关节力矩减小，股外侧肌、腓肠肌、股二头长头肌等肌肉活动度下降。

关键词: 膝踝关节, 膝关节瞬心, 助力外骨骼, 人机耦合仿真分析, 实验验证

CLC Number:

TP242

Xinyao TANG, Rong YIN, Xupeng WANG, Jiayin YANG, Xiaoyi LIU, Yuyang HAO. Design and Optimization of Human-machine Compatibility of Knee-ankle Exoskeletons[J]. China Mechanical Engineering, 2025, 36(10): 2369-2378.

唐欣尧, 殷榕, 王旭鹏, 杨佳音, 刘晓宜, 郝雨阳. 膝踝关节外骨骼人机匹配性设计与优化[J]. 中国机械工程, 2025, 36(10): 2369-2378.

Figures/Tables 30

Fig.1 Lower limb dynamics model

Fig.2 Changes in knee and ankle angles

Fig.3 Instantaneous trajectory of knee

Fig.4 Four-bar kinematic model of knee

Fig.5 Theoretical instantaneous and fitting trajectory of knee

Tab.1 Optimized dimensions of four-bar linkage

$l 1$ /mm	$l 2$ /mm	$l 3$ /mm	$l 4$ /mm	$θ 1$ /（°）	$θ 3$ /（°）
33.45	38.30	51.74	41.00	59.82	25.63

Tab.1 Optimized dimensions of four-bar linkage

$l 1$ /mm	$l 2$ /mm	$l 3$ /mm	$l 4$ /mm	$θ 1$ /（°）	$θ 3$ /（°）
33.45	38.30	51.74	41.00	59.82	25.63

Fig.6 Clutch control circuit diagram

Fig.7 Test of the clutch closed state

Fig.8 Test of the clutch disconnected state

Fig.9 Principle of exoskeleton assistance

Fig.10 Integral structure design of exoskeleton

Fig.11 Design of energy storage mechanism

Fig.12 Motor clutch and transmission mechanism

Fig.13 Design of four-bar linkage mechanism

Fig.14 ADAMS added constraint diagram

Fig.15 Comparison of three coordinate trajectories

Fig.16 Exoskeleton connection pair

Fig.17 Spring force replacing compression spring group

Fig.18 Gait cycle of human simulation model

Fig.19 Human-machine coupling simulation model

Fig.20 Comparison of knee torque before and after assistance

Fig.21 Comparison of joint angles before and after wearing exoskeleton

Fig.22 Marker and EMG block positions

Fig.23 Exoskeleton entity model

Fig.24 Volunteers without wearing exoskeletons

Fig.25 Experimental state of wearing exoskeleton assistance

Fig.26 Knee and ankle angles before and after wearing the exoskeleton

Fig.27 Knee moment before and after wearing exoskeleton

Fig.28 Knee power before and after wearing exoskeleton

Fig.29 Comparison of EMG signals before and after wearing exoskeleton

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