Design and Implementation of a Lower Extremity Exoskeleton for Walking Assist

doi:10.13209/j.0479-8023.2017.056

Abstract

Abstract:

The weight support manner is proposed to enhance wear comfort of the wearable exoskeleton. The design of one-way clutch with the mechanism of ratchets and pawls reduces the weight of the exoskeleton. In the aspect of control, through gait analysis and the feedback control which is the current PID control in PID mode as the inner ring and the plantar sensor and the seat sensor as the outer loop, it achieves intelligent human-computer interaction. The exoskeleton weighs nearly 12.5 kg. The support is about 10 kg for standing and 3 kg for walking. The battery life is more than 2 hours.

Key words: exoskeleton, walking assist, PID control, clutch

摘要：

使用体重支撑的方式可以提高行走辅助外骨骼穿戴的舒适性, 设计以棘轮棘爪组合机构为核心的单向离合装置来减轻设备重量。通过对步态的分析, 以转矩模式下的 PID 电流控制为内环, 增加了足底压力传感和座椅传感构成的外环反馈控制, 实现智能化的人机交互过程。最终实现外骨骼重量 12.5 kg, 站立时辅助支撑约10 kg, 行走中平均辅助支撑约 3 kg, 续航时间大于2小时。

关键词: 外骨骼, 行走辅助, PID控制, 离合装置

Zheng XIE, Mingjiang WANG, Wulong HUANG, Shanshan YONG, Xin’an WANG. Design and Implementation of a Lower Extremity Exoskeleton for Walking Assist[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(6): 989-996.

谢峥, 王明江, 黄武龙, 雍珊珊, 王新安. 一种行走辅助型下肢外骨骼的设计与实现[J]. 北京大学学报自然科学版, 2017, 53(6): 989-996.

Figures/Tables 16

Fig. 1 Forces involved in walking[12]

Fig. 2 Strategy for weight support

Fig. 3 A side view of the exoskeleton structure

Fig. 4 A front view of the exoskeleton structure

Fig. 5 Clutch design

Fig. 6 Control system architecture

Table 1 DC torque motor parameters

参数	峰值堵转	连续堵转
质量/kg	0.76	0.76
最大空载转速/(r · min^-1)	1500	1500
转矩/(N·m)	0.84	0.28
电流/A	5.60	1.87
电压/V	27	9
功率/W	151.20	16.83

Fig. 7 DC torque motor mechanical characteristic curve

Table 2 Harmonic reducer parameters

参数	数值
减速比	120
起动/停止时容许的峰值转矩/(N · m)	70
平均负载转矩的容许最大值/(N · m)	51
瞬时容许最大转矩/(N · m)	112

Fig. 8 Plantar pressure sensor distribution

Fig. 9 Crotch support pressure sensor distribution

Fig. 10 Film pressure sensor resistance-pressure characteristic curve

Table 3 Motor driver parameters

参数	数值
电源电压/V	12~48
最大连续输出电流/A	5
最大峰值输出电流/A	10
PWM频率/kHz	50
输出编码器电源	5 V/100 mA
编码器输入最高频率/kHz	200
控制信号电平/V	高: 3~5; 低: 0~0.3
欠压保护/V	10.5
通讯端口	RS232串口(波特率9600/19200 bps)
温度保护	< -10ºC或> 70ºC
工作温度范围	-10~70ºC

Fig. 11 Control algorithm

Fig. 12 Exoskeleton prototype

Fig. 13 PID parameter adjustment

References 13

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