Research On The Characteristic And Control Technology Of Three-Stage Electro-Hydraulic Servo Valve

Three-stage electro-hydraulic servo valve with large flow and high response has been widely used in many heavy machinery and testing equipments in the fields of aviation, aerospace, ship, metallurgy and transportation. To break technology and price monopoly of abroad corporation, improve performance and reduce the cost of correlative important equipments, we must hold all the key technologies of three-stage electro-hydraulic servo valve. Upon the background of the project"research on key technologies of three-stage electro-hydraulic servo valve with large flow, high response and fail safe"which is developed by IEST (Institute of Electro-hydraulic Servo Simulation & TestSystem) of Harbin Institute of Technology, this thesis studies the mathematics modeling, slide valve null flow field characteristic, control strategy and servo controller of three-stage electro-hydraulic servo valve.Three-stage electro-hydraulic servo valve is a key component, which involves the technologies of mechanism, liquid, electricity and control. This thesis first describes its operating principle. According to its principle, three-stage electro-hydraulic servo valve is divided into four parts, namely pilot valve, servo controller, position transducer, and main power slide valve. Then the structure and principle of every part is detailedly analysed and its corresponding mathematical model is built. In the end, whole mathematical model is obtained by assembling four models and whole mathematical model is analysed and simplified. This research provides every important foundation for studying characteristic and control strategy of three-stage electro-hydraulic servo valve.In the null position flow field characteristic analysis of main power slide valve, the fluid simulation software is FLUENT which is widely used internationally. First, two-dimensional FLUENT models of the oil-in cavity, oil-out cavity and the whole of main power slide valve are established. It is proved to be feasible that oil-in cavity model was used to replace whole model in analysis. Null position characteristic of ideal valve is acquired by simulation. Then it is the first time to deduce the expression of valve flow-area taking into account the edge rounding, radial clearance and pre-opening size at the same time. How flow-area is influenced by the single factor and multiple factors is analysed by using the flow-area expression. Lastly, by detailed simulation and analysis of main power slide valve taking into account valve spool edge rounding, radial clearance, pre-opening size, valve spool edge rounding and radial clearance, valve spool edge rounding and pre-opening size, radial clearance and pre-opening size, valve spool edge rounding and radial clearance and pre-opening size, discharge characteristic curve, discharge coefficient and null position leakage flow curve and so on are acquired. All the characteristic curves are compared with the ideal characteristic curves. At the same time, the relationship between jet fluid angle of valve and valve spool edge rounding and radial clearance is gained. The analysis and results have very good theoretical value and application value.The role of proportional control and proportional plus derivative control is introduced in the control strategy study, and their influence to valve dynamic characteristic is analysed. Then using speed-feedback compensation to improve valve dynamic performance is put forward and studied, and simulation results show that this method is feasible. In the end, a method, feedforward compensation control based on transfer function identification, is used to improve valve dynamic performance, this method utilizes inverse of transfer function as the link of feedforward compensation.In the study of servo controller, first, analog controller is divided into seven parts based on its principle, the seven parts are signal input circuit, circuit of proportional plus derivative control, circuit of modulation demodulation, circuit of displacement signal conditioning, circuit of speed-feedback, circuit of flutter signal and driver circuit. The modeling and analysis of very part is done, then whole analog controller is obtained. Lastly, digital servo controller based DSPs is studied. Its hardware architecture design and model-based control program development is done, which speed up the development of control program and facilitate the software and hardware debugging.In the experiment study of three-stage electro-hydraulic servo valve, experiment principle is introduced, and then control strategies and servo controllers are studied by experiment. Experimental results show that the three control strategies can improve valve dynamic characteristic significantly. Experimental results also show that the analog controller and digital controller meet the need of valve control. Servo controllers play a key role for ensuring and improving the performance of valve. Testing results imply that the main performance of development valve has reached the performance of similar foreign valve.