| With the development of the automation level of large mechanical equipments, the new demands of rapidness and high precision of the large flow rate elec-hyraulic proportional valves have been raised in the filed of engineering. The paper is supported by NCET program, "the study of large flow-rate proportional servo valve". A kind of new large flow-rate proportional valves which is of reliability, low price, high control precision and rapidness are studied in this paper. Base on the study of the regular prior stage structure, a new structure type is proposed in the paper. In the structure, the high speed on-off valve is adopted in the prior stage; the amplify function is carried out in the second stage. In the second stage the valve with displacement feedback controlling is adopted. The valve structure in the third stage is the same as that in the second stage, which is controlled by the displacement feedback signal. The design and the control method of this kind of large flow rate proportional valves are deeply elaborated in this paper.The contents of the chapters are as follows:In chapter 1, the related study background and significance of the subject are expounded. The technical feasibility of the structure, in which the high speed on-off valves are used in the prior stage of the proportional valve, is studied. Base on the studies, the main study content and technical plan are proposed.In chapter 2, combined with the special use of the high speed on-off prior stage valve, the technical features of some kind of several large flow rate, high response main stage valves are studied. The displacement feedback structure and the flow rate feedback structure are adopted in this chapter. The design criterions of the critical parameters are proposed. With the help of the CFD technology, the distribution of the hydrokinetic force in the main valve port is studied, and the equations of the hydrokinetic force which is suitable for the large flow rate situation is worked out.In chapter 3, based on the structure and motion of the HSV series high speed on-off valves, two methods for accelerating the speed of the open and close action of the high speed on-off valve are proposed. In the first method, a small current is exerted in advance. In the second method, a special circuit structure is carried out to accelerate the current's lower process. Through the two methods, the controllable flow rate pulse resolution is improved.In chapter 4, the topology of the high speed on-off valves is studied. The topology structures improve the flow rate pulse resolution, and decrease the control non-linearity. When the deviation is large, Bang-Bang control method is carried out. When the deviation is small, differential flow rate method is carried out. Through the two control methods, proportion characteristic of the second stage is realized. The dynamic characteristics and the control precision satisfy the demands of the third stage.In chapter 5, base on the platform of the AMESim and the MatLab, the three stage valves are simulated. The simulation results show that difference flow rate method satisfies the control precision demands proposed by the main stage, if the response speed of the high speed on-off valve satisfies the main valve response index.In chapter 6, with the self-designed hydraulic test stand, the dynamic characteristics of the high speed on-off solenoid valves and the proportional valve which has the high speed on-off prior stage are tested. At the same time, some phenomena are analyzed by the CFD technology. The technical feasibility of the large flow rate proportional valve with the high speed on-off prior stage is approved further by the results of the tests.In chapter 7, the major work of the study is summarized, and the conclusions and innovations of the study are elaborated. At the same time, future development is predicted in order to provide references for the further researches on this project.
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