A Novel Control for Gait Assistance and Resistance with a Robotic Hip Exoskeleton Using Compact Soft Force Sensors

Abstract

Severa1 recent studies suggest that monitoring the interaction force is crucial for safe and efficient control of wearable robots. This paper presents a novel control of a hip exoskeleton for gait assistance and resistance, which directly introduces human-robot interaction force as feedback for torque control. The real-time interaction force between the human thigh and the robot is measured through a soft pneumatic force sensor system. Thus the delivered torque could be directly monitored in a lightweight, low-cost way using the proposed method, in contrast with traditional torque calculating approaches through the motor current. Furthermore, the soft force sensor-based system was preliminarily applied to control a single-joint hip exoskeleton for gait assistance, resistance, and transparent control modes during level walking. Experimental results show the feasibility of the proposed method in portable exoskeleton control, such as daily assistive or resistive gait training. The advantages of our proposed method include: the good adaptability of the soft sensor to the human body, real-time monitoring of human-robot interaction force via compact sensors, and providing a unified framework for assistive and resistive control of partially-assist exoskeletons.