Research Of Electro-Hydraulic Position Servo System With Negative Spring Stiffness Load

Now with the application of electro-hydraulic position servo system is more and more widely,and the increasing demand.The research on electro-hydraulic position servo system by domestic and foreign scholar has been more and more diversified,but the research on electro-hydraulic position servo system with negative elastic stiffness in load has not been going on.When the system has the negative elastic stiffness load,the open loop of system is inherently unstable,and conventional correction can not eliminate the negative effects of negative elasticity stiffness.The first task of improving the system is to find the appropriate solution to solve the stability of the system,and then improve the response speed and accuracy.Aiming at the problem of instability of electro-hydraulic position servo system under the condition of negative elastic stiffness load,by consulting a large number of documents,the research for the electro-hydraulic position servo system were summarized,a large amount of scientific literatures and the research results of domestic and foreign scholars in this field are analyzed,and the research work of this paper as follow:(1)Firstly,mathematical model of electro-hydraulic position control system is established,system characteristics are analyzed according to the ratio between the absolute value of the negative elastic stiffness and the hydraulic stiffness of actuator.(2)Then,the compensation and correction of the system are discussed.The compensation commonly used was chosen when absolute value of negative stiffness is small.Differential positive feedback compensation was employed when system has a large absolute value of negative stiffness,and a dynamic pressure feedback is also required when the absolute value of negative stiffness approximates to the hydraulic stiffness,the adverse effect of negative stiffness on the system is eliminated after these compensations.(3)These compensations are verified by digital simulations of electro-hydraulic position servo system with negative spring stiffnessFinally,the research contents are summarized.The system under the loads with negative spring stiffness will be unstable,and the greater the absolute value of the negative stiffness is,the worse the performance of the system is.The digital simulation results show that the system is stable after structural compensation,and the rise time is less than 0.2 second,the steady state error is less than 1%.