8 Degrees of freedom human lower extremity kinematic and dynamic model development and control for exoskeleton robot based physical therapy

Abstract

The World Health Organization reports that approximately 15% of the world’s population is disabled. Physiotherapy helps promote functional recovery in upper and lower extremity impairment. An exoskeleton robot-based exercise tool for neurorehabilitation is an appealing solution to treat many disabled people. Knowledge of anatomical characteristics and anthropometrical properties are equally important for mechanical design, as well as modeling, and control of exoskeleton robots. However, most of the anthropometrical data is not readily available from a single source. Additionally, eight degrees of freedom human lower extremity kinematic and dynamic models are also not available. This paper presents dynamic modeling and simulation of the human lower extremity (HLE). A comprehensive review of HLE anatomical characteristics, degrees of freedom, and range of motion of various joints are presented. The Lagrange energy method is used for developing the dynamic model. The developed model includes both linear and rotational displacements of the knee joint. The dynamic simulation uses a sliding mode controller. Simulation results show the performance of the controller, joint torque, and power requirements for tracking specified trajectories. It is also shown that sliding mode control (SMC) is a robust control scheme that works effectively even in the presence of external disturbances and parameter variations. The simulation results indicate that SMC is a suitable choice for controlling a physical exoskeleton robot.