Bionic Research On Hip Joints Of Biped Robots With Variable Stiffness Of Flexible Drive Device

The hip joints of humanoid robots are the center of lower limb motor system and the starting point of lower limb kinematic chain, its structure, movement, and driving characteristics will generate great influence on bipedal walking. Based on the theory of bionics, referring to the anatomic structure of human hip joint, the hip and its driving model with the characteristics of flexible variable stiffness was designed, and it was added to the lower limb model for the analysis and research of dynamic characteristics.This thesis mainly includes three aspects of content:Firstly, the overall scheme of variable stiffness of flexible drive device of the hip was proposed preliminarily, that is a motor driven cam-connecting rod combined mechanism with flexible components and rigidity adjusting device added in the middle. Imitating the structure and muscle distribution of human hip joint, taking the angular displacement-phase curve of human hip as the design target and according to the theory of variable stiffness, the main modules of the mechanism were designed respectively; Secondly, based on the designed main modules and combined with the relationship between previous experimental subjects'lower limb body segments and height, the lower limb geometry model was established unitedly in Pro/E and ADAMS software; Thirdly, in the ADAMS software, by defining the model's inertial parameters, constraints and drives, etc., the dynamic model of lower limbs was created. After setting reasonable simulation parameters, we began to take the gait simulation of the model, and then the hip angular displacement curve and the torque curve were obtained. Compared the results with the achievements of predecessors, we can verify the rationality and feasibility of the design organization. The design results of cam-cable-spring mechanism was given, and the static strength analysis of key parts were carried in ANSYS to verify the reliability.The results of dynamics simulation show that:The camshaft turns a round corresponding to a gait cycle, and its uniform circular motion was transformed to the accurate intermittent movement to realize two legs alternating movement; The added flexible parts and variable stiffness mechanism improved the dynamic characteristic of the output component.