Control of power-augmenting lower extremity exoskeleton while walking with heavy payload

Byunghun Choi,Byungun Kim,Sanghoon Lee,Changhoon Seo

doi:10.1177/1729881419830535

Byunghun Choi, Byungun Kim + Show 2 more

Open Access

https://doi.org/10.1177/1729881419830535

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Abstract

This article presents a design and control framework for a prototype of lower extremity exoskeleton to enhance the human strength during locomotion. The hybrid control strategy is practically applied according to the two gait phases, that is, stance and swing. The weight shift method based on human’s weight shift information was proposed and implemented to acquire the detection of gait phase. In the stance phase, a stiff virtual wall method is applied to support the entire weight of the exoskeleton while carrying a heavy payload. Direct feedback and feed-forward torque control are used to reduce mechanical impedance in the swing phase. In experiments, to verify the performance of the proposed control strategy, a human subject wearing the prototype of power-augmenting lower extremity exoskeleton was able to walk with a 50-kg (110-lb) payload at a maximum speed of 1.67 m/s (6 km/h). Satisfactory results were obtained with regard to walking experiments with the heavy payload.

Highlights

A lower extremity exoskeleton (LEE) attached to the outer surface of the lower body of a human has been extensively developed and studied to assist human’s locomotion abilities in various fields.[1,2] Depending on its purpose, an LEE can be roughly divided into either a power-assisting or a poweraugmenting exoskeleton
We considered that the normal walking speed was set from 0 to 6 km/h and the effective weight of the heavy payload was set to 50 kg based on the military report.[20]
We propose a weight shift method (GP in Figure 3) based on the weight shift change of the human

Summary

Introduction

A lower extremity exoskeleton (LEE) attached to the outer surface of the lower body of a human has been extensively developed and studied to assist human’s locomotion abilities in various fields.[1,2] Depending on its purpose, an LEE can be roughly divided into either a power-assisting or a poweraugmenting exoskeleton. In the stance motion phase, it was well-known that the variation in the joint angle was small and the required torque was large In this experiment, the interaction torques (Figure 8(c)) can be roughly estimated from the difference between the measured torques obtained from the torque sensors (Figure 8(d)) and the assistive torques generated by the controller. The estimated interaction torques applied to the user were relatively small (i.e. within 15 Nm) These results showed that the assistive torques generated by the proposed stance controller played an important role to support the heavy payload in the single stance motion phase. As stated in “Introduction,” there are not many military LEEs operating at a walking speed of 6 km/h while supporting the load of 50 kg shown in this study

Conclusions

Findings

Declaration of conflicting interests