Multi Objective Hierarchical Optimization And Control Of Hydraulic Quadruped Robot

The hydraulic quadruped robot is a typical mechatronics product.In order to achieve the desired action goal,the robot body is usually expected to have small momentum,low energy consumption and other goals.At the same time,the kinematic constraints,dynamic constraints and structural parameters constraints of the robot need to be considered in the operation process.That is to say,the operation of quadruped robot belongs to multi constraint problem under multiobjective task.It is not only of great theoretical significance,but also of great practical significance to study the motion control problem of the hydraulic quadruped robot under the condition of multiple constraints,to explore the moving target to improve the overall performance of the hydraulic quadruped robot,and to study the mathematical description and solution method of the multi-target problem under the condition of multiple constraints.In view of the importance of kinematic and dynamic equations in robot trajectory planning and motion control,the kinematic equations of the whole hydraulic quadruped robot are established,and the mathematical mapping relationships between the joint speed and the foot end speed of the robot are established.On this basis,the acceleration,angular velocity and angular acceleration of each link of the robot are obtained.The dynamic equations of each leg of the robot were established by Newton Euler method.The torque of each joint,the force between the fuselage and the leg and the acting torque were obtained,and the fuselage dynamic equations of the hydraulic quadruped robot are established by Newton Euler method.Then the dynamic equations of quadruped robot were obtained.Considering the importance of high-precision joint torque control in the operation of robot and the problems of force controllability of electro-hydraulic servo actuator,the problems of joint position control of robot are analyzed,and the compound control strategy of position inner ring and force outer ring is proposed,and the effectiveness of the control strategy is verified by experiments.According to the importance of the speed information of the hydraulic quadruped robot in the robot control process,considering the limitations of the robot state estimation based on the kinematic equation,a state estimation based on the dynamic equation of the hydraulic quadruped robot is proposed.The state estimation problem was transformed into a quadratic programming problem with constraints.The modeling and measurement errors are taken as the objective functions of the quadratic programming,the dynamic equations as the equality constraints,and the joint velocity and joint torque as the inequality constraints.The dual method was used to solve the quadratic programming problem and the desired joint velocity and fuselage velocity information are obtained.Aiming at the multi-objective and multi constraint problems existing in the running process of quadruped robot,the principle of multi-objective hierarchical optimization is described,and then it is transformed into a standard quadratic programming problem for solution.Considering the problem of high dimension,many variables and difficult to solve,QR decomposition method is used to decompose the dynamic equation,the dimension of the dynamic equation is reduced,the reduced expression of robot joint torque and foot force are obtained,and joint acceleration and joint torque are selected as constraint variables.A multi-objective function is proposed,which takes the trajectory of the robot's center of mass,the momentum of the robot's fuselage and the energy consumption of the robot as the objectives.The kinematic and dynamic constraints of the robot were considered,and the multi-objective quadratic programming problem was solved.The state estimation experiment and multi-objective hierarchical optimal control experiment of the hydraulic quadruped robot were carried out,respectively.The experimental results verify the effectiveness of the control strategy.