Research On Disturbance Rejection And Trajectory Tracking Control Of Quadruped Robot

The quadruped robot is a complex system with strong coupling,multivariable and time-varying parameters.To realize the the assigned task,it is necessary to consider its own disturbance and external disturbance in the process of motion,and ensure that the trajectory of robot accurately follows the desired.The quadruped robot has its own disturbance,such as mechanical error,modeling error,joint position tracking error.The uncertain factors in the moving environment lead to the existence of external unknown disturbance.The existence of any disturbance will affect the trajectory of the robot.In order to follow the desired trajectory and achieve the desired task when the robot is disturbed,it is important to detect the state information of the robot and adjust the driving parameters in real time.Therefore,this paper studies the disturbance suppression and trajectory tracking to improve the motion stability of the robot.In this paper,according to the characteristics of real-time attitude change of quadruped robot in the process of motion,the kinematic equation of the whole quadruped robot is established.The mathematical mapping relationship between foot end,leg joint and velocity is analysised.According to the attitude information of the robot torso,the trajectory of the quadruped robot is planned based on the inverse kinematics analysis.The trajectory planning simulation experiment of quadruped robot verified that the proposed trajectory planning method based on torso attitude feedback can better track the desired trajectory.In order to improve the stability of quadruped robot motion and restrain the influence of disturbance on the robot,the disturbance suppression algorithm of quadruped robot based on torso attitude information,dynamic model and virtual force model is studied.The mechanism of the disturbance is analyzed,and the dynamic analysis model considering the torso speed,torso acceleration,connecting rod speed and connecting rod acceleration is established,therelationship between the force of each component of the robot and the torso balance is obtained.The virtual force model of robot legs based on torso position control and attitude control is established,and the mapping relationship between joint torque and virtual force of quadruped robot is obtained.The whole control of quadruped robot is realized by controlling the forward direction and lateral motion,torso height and fuselage attitude angle.In view of the disturbance suppression of quadruped robot,the joint torque generated by inverse dynamics model is used to compensate the model error of robot,and the virtual force model is used to compensate the unstable feedback action of quadruped robot.Based on the trajectory tracking requirements of quadruped robot,in order to improve the accuracy and stability of the motion trajectory of robot,the anti disturbance trajectory tracking algorithm is studied.The tracking model and error model of quadruped robot are established.Based on the inequality constraints in the process of quadruped robot movement,the trajectory tracking control problem of robot is transformed into a quadratic programming problem.The trajectory tracking problem of quadruped robot is divided into the control of each foot end and the torso based on its characteristics.The trajectory tracking target of quadruped robot based on the speed,acceleration and tracking error of the robot is established.The trajectory tracking controller of quadruped robot based on model predictive control is designed considering the constraints of the continuity of the trajectory and the stability of its velocity.Aiming at the trot and pace gait,the hydraulic quadruped robot experimental platform is used for experimental research.Experiments on trajectory planning,disturbance rejection and trajectory tracking are carried out to verify the effectiveness of the proposed trajectory planning,disturbance rejection and trajectory tracking algorithm.In this paper,the key technologies of the quadruped robot,such as kinematics,dynamics,trajectory planning,disturbance suppression and trajectory tracking,are studied to provide theoretical basis for the control of the quadruped robot,and lay a foundation for the industrial application.