Estimation of the User’s Muscular Torque for an Over-ground Gait Rehabilitation Robot Using Torque and Insole Pressure Sensors

Abstract

This study demonstrates a method to precisely estimate the muscular torque of a human user precisely during the use of over-ground gait rehabilitation robot which features the lower limb exoskeleton equipped with torque sensors in the hip and knee joints. The muscular torque is a very important criterion on the state of rehabilitation. The torque sensors in each joint, however, do not provide the exact muscular efforts since the dynamics of lower limb and the ground reaction forces (GRF) affect the torque. In this research, the limb dynamics are formulated, and their parameters are identified for each user to precisely compensate for the dynamic effect from the torque measurement during the swing motion. In addition, the method of estimating the user’s muscular torque in consideration of the vertical GRF during stance phase is suggested. A shoe insole with pressure sensors measures the vertical GRF, and the effect of vertical GRF on hip and knee joint torque is formulated for the inverse-dynamicsbased muscular torque estimation. The EMG has been used to analyze the muscular torque and the function of muscle in many studies and was used to validate the accuracy of the proposed method of muscular torque estimation. The experimental comparison between the estimated torque and EMG measurements show that the torque sensors and insole pressure sensors accurately estimate the muscular torque during the swing and stance phase of over-ground walking.