A Study On The Driving Mechanisms Of A Magnetorheological Servo-valve

Magnetorheological (MR) servo-valves consist of magnetorheological fluid (MRF) control systems and control valves. In the MRF control systems, the yield stress of the magnetorheological fluid is changed and forms two hydraulic half-bridges when the magnet filed is applied on the magnetorheological fluids by two pairs of magnet coil. By controlling the magnetizing field strength, the hydraulic half-bridges will output different pressure to drive the spool valve. The spool valve will moves and the regulator orifices are opened while the forces applied on it are different. The flow output of the MR servo-valve can be controlled by controlling the current inputs of the magnet coils.The main work of the paper is about the study on the driving mechanisms of the magentorheological servo-valve, which is the basis of the research and development of MR servo-valve. Based on the research on hysterstic dynamics of magnetorheological fluids, the theoretical analysis of laminar magnetorheological fluid flows in the ducts is carried out. This is the theoretical basis of the design of MR throttle valves and the MR fluid pressure control system. Meanwhile according to the driving mechanisms of MR servo-valve, the experimental study is carried out after the MRF pressure control system is built. The ralations of pressure outputs between current inputs, system flow between current inputs are investigated by experiments. Also the pressure outputs with dynamic inputs are studied. This is the experiment research on the driving mechanisms of the MR servo-valve.The paper consisits of six chapters, the primary contents of research for each chapter are as follows:In the chapter one, the current researchs of the high response and large flow servo-valve are briefly presented. The background and the significant of this study are discussed. At last the main contents of this study and unique characteristics and ceative points in the paper are proposed.In the chapter two, the theoretical analysis of laminar magnetorheological fluid flows in the ducts is carried out. At first, the constitutive models and dynamics models of MR fluids are summarized and comparied. The analysis of laminar flow of MR fluids in circular pipes and between two parallel plates based on the non-convex constitutive model is presented. The results based on the non-convex constitutive model are comparied with the results based on the Bingham conctitutive model and the Herschel-Bulkley constitutive model. It is shown the non-convex constitutive model outperformance the other two models in ananlysis of the laminar flow of MR fluids. Also the analysis is the theoretical basis of the design of MR throttle valves and the MR fluid pressure control system.In the chapter three, the main work is about the design of magnetorhrological throttle valves. At first the main points related to the design of MR throttle valves are discussed at first. On the basis of the analysis of the properties of MR fluids used in the experiment, the basic size of MR throttle part is designed. At last the structure, size and size tolerance of MR throttle valve1and MR throttle valve2is designed and the complete technical drawing is got. The MR throttle valve is different from the traditional hydraulic control valves. The throttle resistance and the flow rate of the valve can be adjusted by controlling the current inputs.In the chapter four, the test device of the magnetorheological fluid pressure control system is designed and built. At first the working principles of the MR servo-valves and MR fluid pressure control system are briefly presented. Then the schematic diagram of the new type system is designed, and the components are selected and purchased. At last the structure of the test device is designed and the whole device is manufactured. The biggest difference between the MR fluid pressure control system and the traditional hydraulic system is service fluid of the system is MR fluid. In the system, the pressure outputs can be adjusted by controlling the current inputs.In the chapter five, the experimental study of the MR fluid pressure control system is done. The data collection system is built based on the Lab VIEW. The relations of pressure outputs between current inputs, system flow between current inputs are investigated by experiments. Also the pressure outputs with dynamic input are studied. At last the improved solutions are suggested based on the results of the experiments. The results of the experiments will be the reference of the design of MR servo-valve. The MR fluid pressure control system has the characteristics of outputting a high pressure and fast response. After the improved research of the devices, the system can be used for the driving of spool valve of the MR servo-valve.In the chapter six, a conclusion of this study is presented and the the improved solutions are pointed out.In the current paper, the driving mechanisms of a magnetorheological servo-valve are studied deeply by the theoretical analysis and the experimental study, which will be the import work of the research and development of MR servo-valve.