Study Of Modeling And Simulation Of Hexapod Robots Based On Flexibility And Back Drive Characteristics

Hexapod robot is an important type of legged robots Its demand of application in the extreme conditions of emergency relief,supplies transportation,and so on,is increasingly prominent.The complex working environment puts forward higher standard for the design of mechanical structure and control system,which making the experiment more risky and difficult.The high-fidelity simulation is an important method to address this problem.Contact problem is an important issue of dynamic simulation.There are two main kinds of contact for a normal hexapod robot: the first of which is the dynamic contact between the foot and terrain;and the second is the intra-friction of the joints.For the purpose of simulating these two kinds of contact,the foot-terrain interaction mechanics and inverse dynamic of robot joint with consideration of joint friction are studied in this paper.A foot-terrain interaction mechanics model is proposed.The two-stage transmission is analyzed focusing on its back-drive behavior,and a coupled model of the motor torque and the joint load,velocity,position and power is proposed.The parameters of the model are identified and the model is validated by experiments.However,the hexapod robot and the terrain make up a statically indeterminate system while static walking.Therefore,the contact model in the single-foot level can not completely solve the problem of hexapod robot simulation.Analysis in the total system level is required.To address this problem,the compliance analysis and kinematics of the robot structure is studied in this paper based on the screw theory.A coupled compliance model as well as the corresponding pseudo-rigid-body model of the robot is established.On combining the foot-terrain interaction model,the equilibrium equation of robot-terrain system is established.The dynamics model of the system is established based on the Kane's dynamic equations.Based on the foot-terrain mechanics model,compliance model,kinematics model and the dynamics model,the method of locomotion control of hexapod robot is studied.The motion of the robot is planned with the walking speed and the steering radius as input to conform to the driving habits of mankind.The method of slipping prevention and inhibition of the robot foot on a small friction terrain is studied.Motion control of the robot joint is studied based on the compliance and dynamics model to accomplish the robot motion control.A numerical simulation of hexapod robot is built using the foot-terrain mechanics model,compliance model,kinematics model,dynamics model and the control model proposed in this paper for the use of development and testing of models;By replacing the dynamic solving module of the numerical by the Vortex dynamic engine and introduce the function of visual simulation,a virtual simulation is proposed to develop and test the control algorithms;By replacing the manipulation and control module of the visual simulation by real-world hardware,a hardware-in-the-loop simulation is presented,which is used to test the hardware of the robot.The verification and validation method of simulation system of robot is studied and experiments are conducted using the hexapod robot prototype,El Spider,to validate the models and simulation proposed in this paper.The control algorithm is implemented and validated using the validated simulation.This paper studied the high-fidelity simulation of hexapod robot along the line of modeling,implementing,and application.The research results can be widely used in the field of structure design and control system research of hexapod robot,which is of theorectical guiding significance and practical values.