Design of a Biomimetic Knee Joint Orthosis for Motion Rehabilitation Assistance

Based on the principles of knee joint anatomy combined with X-ray imaging analysis of bone positions during knee motion, a Revolute-Prismatic-Revolute (RPR) kinematic model has been innovatively established to accurately describe tibial motion relative to the femur while eliminating skin motion artifacts. Building upon screw theory fundamentals, the pitch curves of two meshing cams were innovatively formulated through biomimetic design principles to develop a biologically inspired rotating knee joint mechanism. Power transmission is achieved through two wires driven by a specifically designed double-crankshaft coupling mechanism mounted on the motor rotor. As a result, a novel biomimetic knee joint rehabilitation exoskeleton robot has been developed, which is capable of facilitating both knee flexion-extension rehabilitation training and rotational assistance. The innovative implementation of a double-crankshaft coupling mechanism combined with dual parallel linkage pulley systems enables single-motor dual-output actuation with quadruple joint torque amplification. Prototype experiments have shown that the developed robot has improved in terms of human-machine interaction comfort and biomimetic motion fidelity compared to conventional fixed-axis joint rotation systems.