Research On Gait Control Method Of Quadruped Robot

Among typical footed mobile robots,quadruped robots have excellent kinematic performance and are widely used.Compared with biped robots,quadruped robots are more stable and can withstand larger loads.Compared with the multi-legged robot,the quadruped robot has a simpler structure and has more leg movement space.Therefore,quadruped robots have increasingly become a research hotspot in the field of mobile robots at home and abroad in recent years.This thesis takes the quadruped robot as the research object,through three levels of theoretical analysis,digital simulation and simulation experiments,the kinematics and dynamics of the quadruped robot,the standing posture planning and control of the quadruped robot,the gait planning and control of the quadruped robot,the quadruped robot Four aspects of the robot’s environmental adaptability are studied.The main research contents of this thesis are as follows:1.In the movement of the robot,the reasonable movement of each leg is the basis of the movement of the quadruped robot.Therefore,this thesis introduces and analyzes the basic theory of single-leg motion of quadruped robot.This thesis first analyzes the structure of the Spot Mini robot developed by Boston Dynamics,and calculates the DH parameters of the robot’s single leg.Then,according to the D-H parameters,the construction of the coordinate system of the single-leg link of the robot is completed,and its model is established on the MATLAB platform using the robot toolbox written by Professor Peter Corke.Then,the forward motion and reverse motion of the robot’s single leg were theoretically deduced,and two kinds of robot foot-end motion trajectories of the robot’s single leg were planned,which were verified on the MATLAB model respectively.Finally,the dynamic analysis of the whole body of the robot is carried out,the stability of the quadruped robot is introduced,and the analysis method of the stability of the quadruped robot in this thesis is determined.2.During the movement of the robot,such as squatting,twisting,and leaning forward,the posture of the body will change continuously.This thesis analyzes this movement phenomenon.When the robot is standing,the feet are always in contact with the ground and the relative position does not change.In this thesis,according to the different motion requirements of the robot,the position vector of each leg is calculated,and then the reverse motion of the robot is planned according to the position vector to complete the quadruped robot.Motion planning and control while standing.3.The coordination and stability of gait play a very important role in the movement process of the quadruped robot.The robot needs to take active control during the process of traveling to ensure the stable state of the robot body.In addition,the robot must be stationary or Walk at a very low speed when performing tasks such as handling substances,collecting,and measuring,so a statically stable gait is required.Aiming at this problem,this thesis analyzes the motion process of the quadruped robot under static gait.Static gait requires at least three legs of the quadruped robot to land on the ground at any time.To ensure the smooth movement of the robot under static gait,the planning of the robot’s center of gravity must be involved.Therefore,the motion of the robot in static gait is divided into the adjustment process of the center of gravity in the stage of simultaneous contact with the four legs and the movement process of the center of gravity in the stage of three-leg support.In the quadruped support stage,the center of gravity of the robot needs to be smoothly and continuously transferred to the next support triangle,so the quintic polynomial interpolation method is used to plan the trajectory of the center of gravity at this stage.In the swinging leg movement stage,the swinging foot adopts two kinds of foot trajectories: rectangular and sinusoidal respectively.In this stage,the robot moves forward at a constant speed,so the center of gravity of the robot also moves forward at a constant speed.The trajectory planning of the center of gravity in these two stages ensures the feasibility of the robot Walking in static gait.4.The static gait of keeping three legs on the ground at any time limits the traveling speed of the robot.In order to make the robot produce a natural coordinated gait and realize fast and stable gait transition,this thesis adopts the control method of Central Pattern Generator(CPG)to obtain a dynamic and stable gait,so as to improve the traveling speed of the robot.In this thesis,the mathematical structure of CPG is firstly0 analyzed and verified,and then the CPG is used in the robot’s single leg to obtain the control signal of the single-leg joint.Then the CPG is applied to the whole robot,and different parameters are set to obtain the control signals of the different synchronous states of the robot,and finally the robot can switch between different synchronous states.This control method abandons the tedious and complex dynamics modeling,and avoids the contradiction between single-cycle planning and continuous control.,stable and varied movements.5.Terrain adaptability is particularly important for quadruped robots for unstructured environment applications,and is the premise of robot practicality.Therefore,this thesis analyzes the environmental adaptability of the quadruped robot.This thesis considers three simple situations for research: the robot Walking on a slope,the robot crossing a ground obstacle,and the robot’s motion with lateral acceleration.In slope Walking,the CPG equations of the robot during the uphill and downhill processes are given by imitating the vestibular reflex of mammals.When crossing the ground obstacle,imitating the flexor reflex of mammals,the motion of the robot is divided into pre-swing phase reflex and post-swing phase reflex,and the robot motion process of pre-swing phase and post-swing phase is planned respectively.When there is lateral acceleration,a set of CPG equations associated with the hip lateral swing joints are added to obtain the joint control signals of the robot under lateral motion.