Optimization, Design and Experiment of Knee Joint Mechanism for Hydraulic Bipedal Robot

Hydraulically actuated bipedal robots offer good dynamic locomotion capabilities but face critical challenges in knee joint design, requiring a careful balance between torque output, load-bearing capacity, and thermal dissipation. This study presents an integrated optimization methodology that addresses the limitations of conventional designs by synergistically optimizing the dimensions of the knee joint linkage and the embedded thermal dissipation structure. Key advantages of the proposed methodology include a substantial improvement in motion control accuracy, achieved through multi-constrained optimization of the linkage mechanism (considering geometric parameters, range of motion, and moment arm), which enhances both output motion linearity and positioning accuracy. Additionally, an innovative integrated thermal dissipation design incorporates a robot femur structure with a passive thermal regulation mechanism, offering the combined benefits of structural reinforcement and seamless integration of internal hydraulic circuits. Crucially, the hydraulic manifold incorporates an engineered finned thermal dissipation system that leverages aerodynamic convection to efficiently dissipate servo valve waste heat. This integrated approach eliminates the space and weight penalties typically associated with conventional external radiator designs. Simulation experiments based on models of the hydraulic cylinder, servo valve, and six-bar linkage mechanism demonstrate that this methodology effectively enhances the overall knee joint performance. This approach paves the way for more capable and reliable bipedal robots by simultaneously optimizing key performance metrics through the integrated design of mechanical and thermal dissipation systems.