Trot Gait Planning Of Quadruped Robot Based On Double Generating Functions Method

To control a robot walking in a complex environment,it is necessary to adjust various gait parameters such as its step length,walking speed,gait cycle,etc,and complex planning requirements will bring a heavy calculation load to the robot.In recent years,a gait planning method based on a double generating functions was proposed,whose advantage is that gait parameters can be easily changed during planning,and it has a low computational load.This paper mainly explores the feasibility of the double generating functions method for trot gait planning of a quadruped robot,and finally achieves the control of robots with adjustable gait parameters and stable walking.Firstly,taking the cheetah as a bionic object,a simplified diagram of the quadruped robot mechanism is obtained by simplifying its skeleton structure.The D-H coordinate system was established,and the single leg was subjected to positive kinematics analysis.The relationship between the swinging of the robot's leg joints and the trunk forward under the mechanism was analyzed.According to the virtual leg technology,the quadruped model is simplified to a biped model,the Euler-Lagrange energy method is used to solve the dynamic equations,and the robot model is linearized by the second-order Taylor expansion method.Secondly,design a quadratic cost function,the gait planning problem of quadruped robot is transformed into an optimal control problem,and the general form of linear quadratic optimal control problems.Based on a pair of generating functions,a method for solving the optimal control problem is designed.By solving the coefficients in the generating functions,the reference gait of the robot linear model is planned.A PD control system is built,and the optimal gait of the original robot nonlinear model is obtained by PD trajectory tracking.Then,the stability conditions of the quadruped robot walking in trot gait are analyzed,and the value range of some gait parameters is given.Single-step and continuous-step simulations verity the feasibility of the double generating functions method for planning gait.Simulation comparison was made with CPG method(biological control-based method)and single generating function method(model-based gait planning method),in terms of gait fine planning and online planning time.Finally,based on theoretical and model analysis,an experimental platform for gait testing of quadruped robots was built.The experimental results verify the correctness of the theoretical analysis of the robot's diagonal gait horizontal stable walking,and also verify the effectiveness of the dual generator function method to plan the quadruped diagonal gait.