Theoretical Analysis And Test Study On New Electro-mechanical Transformers Used In Electro-hydraulic Proportional Servo Valves

Servo proportional components (including servo proportional valves and servo proportional pumps) are important hydraulic control components and widely used in every aspect of industrial and engineering automation. The ability to master the associated technology has a significant impact on national defense construction and equipment manufacturing. Currently, the technology is a holding back factor for our country to transform from a big manufacturing country to a manufacturing power. National long-term development plan, major projects are planning to adjust this technology as a key breakthrough. As the servo proportional component performance is largely determined by the electrical-mechanical transformer performance, it has great significance for us to be in-depth study of electrical-mechanical transformer for national defense and equipment manufacturing industry. Being one aspect of the study of National Natural Science Foundation " Theories and Methods of New Concept Continuous Control on Electro-hydraulic Flow Rate and Direction " (50575156), this thesis focus on in-depth study of low-cost, high response, new structure of electrical- mechanical transformer and research methods for electrical-mechanical transformer. Proportional solenoids were researched theoretically. In order to take the advantage of high accuracy of finite element method (FEM) and advantage of rapid calculation ability of most simulation software, the FEM model of the key reluctance in proportional solenoid was established. Characteristic parameters of the FEM model were determined with FEM. By fitting the FEM calculation results, the formulas for calculating the key reluctance in proportional solenoid were obtained. The formulas were also validated with Simulation in MATLAB/SIMULINK and FEM software Ansoft. This work laid the foundation for building the accurately proportional solenoid model in simulation software.A new scheme for electro-hydraulic proportional servo valves with on-off solenoids was proposed. A method of adaptive Feed Forward Compensator (AFFC) to correct static nonlinear characteristic of on-off solenoids is proposed based on close loop control. The settle time is shorten obviously by using Anti-Satuation Integral Control (ASIC) techniques, while the static error is held to zero. The principles of AFFC and ASIC are explained theoretically and tested in experiments. Moreover, we found that the transient time was even shorten when the gain of the close feedback loop was increased in our scheme, The research results show that our scheme has the advantages of simply design and low price.In order to develop the fast response electro-mechanical transformer used to drive the pilot stage of large flow rate servo proportional valve, a novel structure of electro-mechanical transformer with shaped permanent magnet was proposed and its design principles were indicated. Magnetic circuit characteristics of the dedicated moving coil linear motor (MCLA) were studied with finite element method. The analysis indicated that MCLA's driving force can be increased more than 7% by using shaped permanent magnet. A MCLA used to drive the pilot stage of large flow rate servo proportional valve was designed and the prototype was developed. The test system for small linear motor was built and the prototype was tested. The test results show that the performance of the prototype can meet the pilot driving requirement of fast response large flow rate servo proportional valve.A novel 2-degree-of-freedom electro-mechanical transformer (2-DOF EM) with two moving parts was proposed to meet the high speed response of electro-mechanical trans- former required by servo proportional valves. The principle on which it decreased the response time of a servo proportional valve was explained. Several possible structures were introduced. The magnetic circuit of single-input dual-output EM (SIDO EM) was analyzed. Analysis indicated that SIDO EM can simultaneously drive the proportional valve spool and valve cover, and the valve opening is controlled. But the spool or valve cover cannot be controlled independently with SISO EM. The magnetic circuit of a hybrid two-input 2-DOF EM was analyzed, and its output characteristics in every case were derived with finite element method (FEM). Research results indicate that the 2-DOF EM can control the two linear moving parts simultaneously, drive them to move in the same or opposite direction independently. It can be used in the control of servo proportional valves and other equipments which have two linear moving parts.The application of proportional servo valve was studied. The starting of electro-hydraulic position servo system might cause the drop of the system pressure, actuator velocity fluctuation and hydraulic impact. The sudden drop of the pressure, if with more than one actuator in the system, would probably misact other actuators or even lead to grave accidents. Facing the problems, two solutions are proposed. One is to divide the position control procedure into a position control procedure and a velocity control procedure in which the maximum velocity of the actuator is restricted within the supply flow rate and the liquid compressibility. The other is to adjust the flow rate at the servo valve by means of pressure difference of the chambers. These two methods are demonstrated theoretically and verified by digital simulation and experiments of an electro-hydraulic position servo system. It is finally proven that the sudden drop of the supply pressure and hydraulic impact during the starting of electro-hydraulic position servo system can be removed with the two new methods without influence upon the system response properties.