Research On The Correction Of An Electro-hydraulic Servo System Under The Spring Load With A Negative Value

When the load elastic stiffness value is positive and far less than the hydraulicspring stiffness value, the system can meet these requirements simultaneously, such asquickness, stability and accuracy, by adding certain compensator to theelectro-hydraulic servo system. However, the problems that open-loop systeminstability and poor positioning stiffness are found, on conditions that the load elasticstiffness value is negative. Therefore the primary task of improving the system is howto keep the system stability. On the basis of analyzing the domestic and foreignresearch about the electro-hydraulic position servo system behavior, some study onnegative spring stiffness electro-hydraulic servo system were carried on. Mainlyworks were as follows:Firstly, by taking the existing electro-hydraulic servo system mathematical modelas a reference, a mathematical model of the system of variable hydraulic stiffnessunder the load with a negative elastic stiffness was built.Secondly, mathematical model had been analyzed. The results showed: whenload elastic stiffness value is negative, the system is instability in majority of the workregion, the steady-state accuracy is poor, while positioning stiffness is not ideal.Thirdly, compensation strategies about negative load elastic stiffness systemwere studied, and discussions on how to realize the compensation were studied. Theparameters affecting the system were analyzed on the basis of transfer function of thesystem. And the system stability and positioning stiffness have been effectivelyimproved by adding the appropriate mechanical compensation device.Finally, according to determination of the parameters of system, the systemdynamic characteristics were simulated. Related components and parameters of thesystem were determined, and a system simulation program was created by usingsimulink. Simulation of positive and negative load elastic stiffness system wereacquired. The results show that with the corresponding mechanical compensationdevice, the stability of the system has been effectively improved, and the accuracy of system will keep in5%, after adding certain correction element and bandwidth of thesystems can reach5Hz.