Study On Control Method And Structure Optimization For Leg Mechanism Of Hydraulic-Actuated Quadruped Robot

In recent years,with the continuous development of science and technology,humans have made some breakthroughs in the study of the step foot mobile robots.the step foot mobile robots have gradually attracted more and more attention from researchers due to their ability to adapt to complex terrain,and have become research hotspots.However,the foot robot is much more complicated than the wheeled robot.Whether it is the control algorithm or the body structure,the foot robot still needs a lot of research.As a kind of step foot mobile robot,quadruped robot is more stable than biped robot and more concise than hexapod robot.A single-leg system with excellent performance is essential to the study of step foot mobile robot.Therefore,we will focus on the single-leg system of the hydraulically driven quadruped robot,and the research work is carried out from the following aspects.Kinematics modeling and calculation of the relationship between joint speed and acceleration and hydraulic cylinder speed and acceleration.Kinematics includes forward kinematics and inverse kinematics,we solve forward and inverse kinematics respectively,and then based on the kinematics,the relationship between the joint speed and acceleration of the single-leg system and the speed and acceleration of the hydraulic cylinder is solved.Single-leg system dynamics modeling.This article first calculates the simplified dynamics of the single-leg system,only considering the mass of the body,thighs,and shank.Through simulation,it is found that the fitting accuracy with the virtual prototype simulation results is not good enough.Therefore,we derives complete dynamics on the basis of simplified dynamics where the mass of the hydraulic cylinder and the hydraulic cylinder rod are considered.The trajectory planning of the single-leg system is carried out by different methods,and the results of the trajectory planning are input into the established valve-controlled asymmetric cylinder position control model for calculation.First,the approximate solution of the SLIP model is used to plan the trajectory of the single-leg system's center of mass.Then,based on the cosine motion of the center of mass speed,another set of trajectory planning methods is derived.Subsequently,the correctness was verified by joint simulation of Adams and Simulink.The single-leg system is based on dynamic control.By deducing the dynamics content,the Simulink control module is built,and the verification is completed through joint simulation with Adams.Aiming at different optimization functions and different optimization parameters,the structure optimization of single-leg system is carried out respectively.First of all,with the maximum joint swing amplitude as the goal,optimize the joint parameters of the thigh and lower leg joints;second,with the minimum power of the single-leg system as the goal,optimize the mass distribution and mass size of the single leg;and finally,take the total power of the single-leg system and the single Multiply the working space area of the leg system by the minimum sum of weights to optimize the parameters of each rod length of the single-leg system.