Lower Extremity Exoskeleton Simulation Model with Variable Stiffness Actuation for Vertical Locomotion

This paper proposes a lower extremity exoskeleton simulation model for more effective control in vertical locomotion when patients need to move from static seating configuration to walking-ready configuration. Variable impedance actuators (VIA) or variable stiffness actuators (VSA) are considered as the primary source of generating and translating controlled torque values with elastic compliance properties to movement elements of a discussed system using PID control with dynamic compensation. The model-applied torque can be divided into two torques, one about gravity compensation and another about acceleration. The simulink environment with simscape library was used to create a simulation process of the working mechanism. Data on angles, torques, and velocities were obtained and considered for correctness in natural human locomotion. Calculations provide upper limit for the required torque to stand up, which can be used as a basis to select a proper actuator.