| Legged robots are the product of learning from nature.Compared with traditional wheeled/tracked robots,the discrete motion of legged robots has a better ability to pass through unstructured terrain.Among them,quadruped robots rely on their structure The advantages of simplicity and stable performance have been extensively studied.For quadruped robots that rely only on proprioception,the complexity and unpredictability of unstructured terrain bring great challenges to its motion control methods.Aiming at the above problems,this dissertation studies the kinematic modeling,gait planning,terrain adaptive and dynamic control of quadruped robot.The specific contents are as follows:(1)Based on the DH method,the kinematics of the quadruped robot is modeled,and the forward and inverse kinematics equations and geometric Jacobian matrix are derived,and the corresponding closed solutions are given.On this basis,the workspace of the quadruped robot foot is drawn by Monte Carlo method and its range is approximately solved,which provides the model basis for the motion planning and dynamics control of the quadruped robot.(2)The closed-loop gait control system of quadruped robot was constructed by adding the foot contact feedback branch.On this basis,the gait planning strategy and algorithm based on ground touch detection were proposed,and the traditional strategy based on time planning was improved to solve the problem of the quadruped robot swinging legs contacting the ground too early or too late in unstructured terrain.The stability and integrity of gait of quadruped robot in unstructured terrain are guaranteed.Then,based on forward kinematics and leg phase state set,a strategy and method for estimating terrain parameters is proposed,and an adaptive control algorithm for quadruped robot fuselage attitude and height of mass center is proposed by using the estimated terrain parameter information,which realizes the stable walking of the quadruped robot on the unstructured terrain such as slope and rough road surface,and improves the adaptability of the robot to the unstructured terrain.(3)Based on the single rigid body dynamics model,the dynamics control model of the quadruped robot was established.The expected foot contact force was solved by quadratic programming method with friction cone constraint.On this basis,a dynamic control system based on contact force feedforward was constructed to realize the dynamics control of the quadruped robot.The virtual model control method was used to optimize the force control system based on contact force feedforward,and the whole body force control system based on contact force feedforward was proposed to solve the adaptation problem of leg configuration to the motion planning of the center of mass.An approximate method for estimating the friction cone direction of foot contact surface is proposed to improve the accuracy of expected foot contact force.In addition,for the control of the swinging leg,the landing position of the leg is given based on the Raibert method and the capture point theory,and the swing trajectory of the foot is designed based on the Bessel curve.Finally,impedance control is used to realize the flexibility control of the swinging leg.The effectiveness and reliability of the proposed algorithm are verified by simulation experiments. |
