Biomechanical design and control of an eight DOF human lower extremity rehabilitation exoskeleton robot

Abstract

Exoskeleton robot-assisted physical therapy has received a lot of research attention due to its positive impact on human upper and lower extremity rehabilitation. The exoskeleton robot attaches closely to the human limbs and facilitates natural movements at the joints. The effectiveness of the exoskeleton robot-assisted physical therapy is influenced by the mechanical design of the manipulator. An ergonomic design helps the user exercise for an extended period. In this paper, the mechanical design of an 8 degrees of freedom human lower extremity exoskeleton robot for rehabilitation is presented. Among the 8 degrees of freedom, 7 are actively actuated and 1 is passively actuated. A cam follower mechanism is developed to replicate the complex motion at the knee joint. To make the exoskeleton comfortable and easy to use for the users, ergonomic design rules are followed. A dynamic model of the human lower extremity exoskeleton robot is also developed for controlling the robot. A Sliding mode controller with super twisting algorithm is employed to simulate the dynamic model. Results for stability analysis of the developed controller are also presented.