A Musculoskeletal Simulation of Human-Mechanism Interaction: Biomechanical Analysis of a Single-DOF Gait Rehabilitation Device

Gait rehabilitation robots present promising solutions for delivering tailored training while optimizing clinical resources. This study presents an OpenSim simulation of the Mech-Walker, an innovative single-degree-of-freedom (DOF) gait rehabilitation device. By integrating the Mech-Walker with a detailed musculoskeletal model, we conduct a comprehensive investigation of walking dynamics and human-robot interaction. The device utilizes an 8-bar Jansen mechanism actuated by a single motor, enabling precise control of lower-limb motion, and incorporates an adaptable weight suspension system. Our simulation provides a detailed analysis of the interaction between the Mech-Walker and the human user, with particular focus on forces and torques at contact points and joints. Results indicate that the primary interaction forces at the pelvis-seat and foot-pedal interfaces are directly proportional to the user's body weight, with a peak vertical seat force of approximately 750 N for a 75 kg user. The mechanism effectively replicated hip and knee joint kinematics within normative ranges, while ankle trajectory exhibited greater deviation. This study establishes a validated simulation framework to support the design and refinement of gait rehabilitation robots.