Researching On The Control Strategy Of Force Servo System Of Hydraulic Robot Based On Disturbance

The hydraulic quadruped robot is driven by the hydraulic pressure as the power source.With the characteristics of flexible movement and strong adaptability,it is widely used in aerospace,military industry and se rvice fields.With the wide application of hydraulic quadruped robot,the requirement of joint driving is higher and higher.As the main driving system of the hydraulic quadruped robot,the electro-hydraulic servo system is required to have the characteristics of high control accuracy,fast response speed and stable output.However,the tracking output characteristics of electro-hydraulic servo system are seriously affected by friction,leakage,external load interference and modeling uncertainty.In this paper,the disturbance compensation of the external load disturbance and modeling uncertainty of the electro-hydraulic servo system is carried out to improve the control performance.Firstly,the mathematical model of the system is established for the valve controlled cylinder force servo drive system of quadruped robot.When the system has modeling error and load disturbance,the state equation of the force servo system is derived,and the force output equation of the system is derived,and the stability is determined,which lays the foundation for the research of interference suppression strategy.Secondly,according to the mathematical model of the force servo system,the IMC(internal control)model is introduced to change the force feedback of the system into disturbance feedback.The IMC filter is used to compensate the disturbance.The process model of the transfer function of the force servo system with different stiffness is analyzed.The reduced model is transformed into the standard form of IMC-PID by using the theory of suboptimal reduced order model,which is applied to the system with variable stiffness The output characteristic of force servo system is analyzed.Thirdly,the control function is constructed according to the state space equation of the force servo system,the feedback linearization is carried out by using the calculation method of Lie derivative theory,the transformation relationship between the state variables is constructed,the new state space equation is derived,the control quantity of the nonlinear system is derived through the coordinate inversion of the control quantity of the linear system,the feedback linearization is completed,and the design has the characteristics of finite time convergence The output characteristics of the force servo system under the condition of load disturbance and system modeling disturbance are analyzed.Finally,the experimental platform of valve controlled cylinder electro-hydraulic servo system is built to simulate the joint force servo drive s ystem of quadruped robot,and the semi physical simulation experiment is carried out.According to the different load equivalent stiffness of the hydraulic quadruped robot in different environments,IMC-PID controller and DOB sliding film controller are used to compensate the disturbance in the force servo drive system under different stiffness conditions.