Research On Hydraulic Position Servo System With Variable Stiffness Load

Electro-hydraulic servo system is an important part of modern industrial control system.It has the characteristics of good rapidity,high precision and small volume,and is especially suitable for aerospace and metallurgical industries.With the increasing degree of industrial automation,the requirements for the performance of electro-hydraulic servo system are also improved.Then the performance of the system is different under different loads and different environments.How to maintain a good performance is an important issue of electro-hydraulic servo system.The electro-hydraulic servo system with variable stiffness and elastic load widely exists in various industrialprocessing situations,such as finishing machine,AGC plate thickness automatic control system,electro-hydraulic load simulator,etc.Aiming at how the performance of electro-hydraulic position servo system changes under different stiffness of elastic load or even load stiffness,the following research work has been done in this paper.Firstly,the transfer function method is used to model the system.According to the open-loop transfer function,the stability of the system is analyzed,and the maximum load stiffness that the system can sustain while the basic parameters remain unchanged is calculated.Under different load stiffness,the possible influence of stiffness change on system performance is analyzed.Using MATLAB/Sumilink software,interactive graphical modeling of the electro-hydraulic position servo system is carried out.The step response of the electro-hydraulic position servo system is simulated under the conditions of small stiffness load,large stiffness load and variable stiffness load.According to the comparison of the curves,the accurate conclusion of the influence of the change of load stiffness on the performance of the system is summarized.Compared with the transfer function method,the state space method has great advantages.It can not only get the external information of the system,but also let us know the internal state of the system,so as to understand the performance of the system more accurately and realize the optimal control of the system.According to the state space method,the electro-hydraulic position servo system is modeled,and according to theoptimal control law of the system solved by the optimal control theory,the better performance curve is obtained by simulation.Experiments are carried out on the integrated innovation platform of hydraulic components and systems.The results validate our previous simulation and analysis,and show that the optimal control has great advantages in the electro-hydraulic servo system with variable parameters.