Motion Impedance Control Study Of Quadruped Robot Foot

The quadruped robot has the advantages in environmental adaptability and kinematic dexterity compared to the wheeled robot.And this legged mobile platform will have broad application prospects.However,the quadruped robot foot usually has rigid structure,which affects the stability of the robot.Therefore,this thesis makes a research on impedance control of a small bionic quadruped robot to realize the compliant interaction between robot foot and the environment.And the contact force is controlled by the combined action of joint torques.The main work of this thesis is completed as follows:Firstly,the differential gear mechanism of robot leg and the quadruped robot's mechanical structure is analyzed.For the need of position control in impedance system,the floating base system analysis method is introduced,kinematic model of the robot in floating base coordinate system is set up and the Jacobian matrix of robot leg is deduced.Secondly,the robot dynamics in floating base coordinate system and the robot leg contact characteristics with environment are analyzed.The QR decomposition of transposed matrix of Jacobian is proposed to decouple the actuated joint torques and an algorithm is designed to estimate the contact force.The robot dynamics is set up.Besides,the motion impedance control strategy of robot foot based on impedance control algorithm is designed and the stability boundary is calculated.The influence of impedance parameters on the performance of the control system are also analyzed.The free space control model as well as the constrained space control model are respectively established by Simulink and ADAMS.The motion of the robot leg caused by an instantaneous impact is simulated and the feasibility of the control strategy is verified through the simulation results.In the end,aiming at the limitation of the basic impedance control algorithm,the adaptive control strategy of robot foot is designed and the stability problem is analyzed to determine the update rate of the algorithm.The simulations are carried out under different environment stiffness and desired force.The feasibility of the control strategy is verified through the simulation results.At last,two algorithms are compared through the two aspects of position and force control.