7 Degrees of Freedom Passive Exoskeleton for Human Gait Analysis: Human Joint Motion Sensing and Torque Estimation during Walking

In order to provide insightful information for the effective diagnosis of a patient's abnormal gait, this paper presents a 7-DOF passive exoskeleton which can deliver both kinematic information and estimated human joint torque during walking. This paper introduces both a hardware implementation and an algorithm to obtain kinematic information and human joint torque. To measure the joint kinematic and ground contact force; encoders, gyroscopes and smart shoes are used and attached to the passive exoskeleton. However, human joint torque information cannot be directly measured due to the impracticality of installing a torque sensor inside the human joint. Therefore, a dynamic model of human walking used for estimating the human joint torque is proposed. Since the kinematic constraints of the lower-limb extremity during walking vary depending on gait phases, the dynamic model of human walking is described by multiple sub-dynamic models, which are derived using Lagrangian mechanics. The joint kinematic measurements and estimated human joint torque results are verified by experiments.