Research On Force Balance Control Of Hydraulic Quadruped Robot

During the operation of a hydraulic quadruped robot,it should always be in a state of balance in order to avoid the overturning of the robot.Because of the joints of the robot are driven by electro-hydraulic servo actuator,the joint angle and torque control of the robot are realized through the actuator.Therefor e,in order to ensure the stability of robot operation,actuator position control and driving force control should have certain servo precision,so as to achieve high precision reproduction of command signals.At the same time,how to generate the joint instructions required for robot balancing is the key and difficult point in the research of foot robot.The contents of this thesis are as follows:According to the constituent elements and structural characteristics of the hydraulic quadruped robot,and the bionics principle,the structure size and joint rotation angle of each main joint of the robot are determined.On this basis,using the dynamic simulation software for dynamic analysis of robot,to obtain the load locus of each joint of the robot.Based on the mathematical relationship between the locus of the robot's joint and the load locus of the actuator,the actuator load matching is carried out.Finally,the structure size of the electro-hydraulic servo actuator(piston,piston rod and stroke),the flow and pressure of the electrohydraulic servo valve are determined.Considering the characteristics of robot joint driving force control,this thesis analyzes the characteristics of the driving force model of electro-hydraulic servo actuator,puts forward the joint driving force control strategy based on the dynamic model.The load compensation is carried out through the velocity compensator and flow compensator.The driving force of the inner loop of the actuator is controlled by using the PID controller.The driving force instruction is generated through the dynamic model.The outer position loop and outer velocity loop are used to compensate the force deviation signal,and the optimal driving force control of electro-hydraulic servo actuator is obtained.The single leg kinematic and dynamic equations was established,the angle command was produced by single leg kinematic equation,the angle torque was produced by single leg dynamic equation.The whole machine kinematic and dynamic equations was also established,the relationship between the body attitude and the legs,the single leg dynamic equations with support phase was established.The binding force equation between the leg and body was obtained,and the whole dynamic equation was established,which provide theoretical basis for robot balance control.Finally,the experiment research is worked on hydraulic quadruped robot HD test platform,hydraulic robot single leg kinematic,single leg dynamic,force control with inner force and outer position,force control with inner force and outer velocity,force balance control with four legs,force balance control with three legs,and force balance control with two legs.Respectively,the efficiency of the proposed control strategy was verified.