Research On Compliance Of Hydraulic Driving Unit Based On Impedance Control

Legged robots have broad application prospects because they can adapt to complex terrain and harsh environments,and can complete more complex tasks.Due to its high power density,fast dynamic response and strong electromagnetic interference resistance,the hydraulic drive unit can meet the requirements of the robot for load and motion performance.However,because of the high hydraulic stiffness,the robot will have a large impact when it comes into contact with the environment,which affects the overall structure.Therefore,this paper studies the improvement of the flexibility of the hydraulic drive unit,and improves the control precision of the impedance control,so that the hydraulic drive unit has better flexibility.The main research contents are as follows:In order to establish a mathematical model of the force servo system that is more Compatible with with the test bench,the initial position and initial volume of the servo cylinder are first determined by the spring stiffness theory,and then three mathematical models of the valve-controlled cylinders under the defined load pressure and load flow are built.The simulation analysis selects which is most consistent with the definition of load and flow of the test bench.After linearizing the nonlinear section,the mathematical model of the force servo system is finally established,and the outer loop impedance control model is given.In the aspect of improving the force tracking effect of the impedance control inner ring force servo system,the force servo control algorithm is studied.The algorithm combination of nonlinear PID and auto disturbance rejection controller is given,and the simulation model of force servo system and controller simulink is built.The controller parameters are set,and the nonlinear PID and auto disturbance rejection controller are applied to verify the force servo system.Control effect.The top experimental platform was built.The control algorithm of the auto disturbance rejection controller and PID was reprogrammed in LabVIEW.The effectiveness of the auto disturbance rejection controller on the force servo system was verified by experiments,and the impedance control experiment was carried out.The experimental results show that The auto disturbance rejection controller can improve the precision of the force servo impedance control,thereby enhancing the flexibility of the hydraulic drive unit.