Type Synthesis of a Novel 4-Degrees-of-Freedom Parallel Bipedal Mechanism for Walking Robot

In this study, the conventional virtual chain method is refined and a 4-degrees-of-freedom (DOF) parallel bipedal mechanism (PBM) for walking robots is presented. The proposed design has the advantages of low inertia, high load-to-weight ratio, and impact resistance. First, to solve the redundant motion-transmission problem, a refined virtual chain method is proposed for the type synthesis of the 4-DOF parallel thigh mechanism. Second, the relationship equation for each actuated wrench component in a reasonable actuated joint arrangement is derived, and the number and location of the actuated joints are determined. Third, by optimizing the design of the hip joint as a 2-DOF counter-centered five-link spherical mechanism with different rotation centers, passive knee and ankle joints are designed based on the bionic principle. This design is performed to make the PBM isotropic and minimize inertia. The proposed PBM can withstand heavy loads and impacts owing to its humanoid crossed four-link knee joint mechanism and compliant calf mechanism. Finally, the prototype is processed, and the rationality of the design and excellent performance of the PBM design are verified by dynamic and static simulations and gait experiments. Herein, a parallel bipedal mechanism for walking robot is presented using the refined virtual chain method. The design of the hip joint of 2-degrees-of-freedom counter-centered five-link spherical mechanism, knee joint of crossed four-link mechanism, and humanoid calf mechanism makes the robot have significant advantages in the comprehensive performance of load-to-weight ratio, mechanism strength, movement inertia, and impact resistance.image (c) 2023 WILEY-VCH GmbH