Research On Key Technologies Of One Kind Of Electro-Hydraulic Flow Control Valve

Electro-hydraulic control system has been widely employed in aviation and marine industries because of its advantages of high control accuracy, high reliability and good load resistant ability. As the key part of electro-hydraulic control system, electro-hydraulic flow control valve plays an important role in transforming electrical input signal to flow output. The enhancement of both static and dynamic characteristics of electro-hydraulic flow control valve can improve the performance of electro-hydraulic control system and is an impetus for the development of flow transmission and control technologies.This dissertation has focused on the critical technologies of electro-hydraulic flow control valve. With abundant literature reviews, theory analysis, computer simulations and experiments, three major objectives are studied in depth. Firstly, a PVT experimental system to simulate the working conditions of pressure tank and an one dimensional unsteady diffusion equation based on the system have been established. The diffusion coefficients of air in both hydraulic oil and silicone oil have been measured and calculated to obtain the relationship between diffusion coefficient and temperature. Then, relationships of the diffusion and viscosity have been discussed based on Eyring’s theory, as well as the free energy of activation and temperature in these two transport phenomenon has been obtained. Secondly, a novel pressure-resistant oil-immersed proportional actuator has been presented with a magnetic grid magnetic-isolated ring (MGMR) on its single-piece sleeve to replace the conventional magnetic-isolated ring structures, which makes the manufacture process simpler by reducing the welding procedure and obtains the advantage that the single-piece sleeve with MGMR structure can be machined through non-welding high magnetic permeability materials; the experimental and simulation results are consistent with each other and show good static and dynamic performances of this proportional actuator. Thirdly, an electro-hydraulic flow control valve with the parallel structure of relief valve and throttle valve is presented, in which a double damping structure is applied in the relief valve to guarantee the valve stabilization without any overshoot, and a cone type nozzle flapper structure is utilized in throttle valve to enhance the valve reliability. Both simulations and experiments have shown satisfying static and dynamic characteristics on the flow control and have achieved expected performance.In chapter one, the current research state and development of electro-hydraulic flow control valve critical technologies are reviewed, including the characteristic of hydraulic oil, electro-mechanic transducer and structure of electro-hydraulic flow control valve. The research significances, research points and research contents are described generally.In chapter two, the experimental apparatus used to study diffusion process is introduced and the relative mathematical model is established. The accuracy of the method to measure and calculate diffusivity of air in dimethyl silicone oils and in hydraulic oils was verified by data matching with other literatures. The correlations among solubility, diffusivity and temperature were obtained and fitted by using Arrhenius equation for engineering applications. In terms of Eyring’s activation theory, the difference between activation in the air-silicone-oil diffusion process and that in the momentum transport of the silicone oil were discussed.In chapter three, analysis on the principles and basic laws of magnetic circuit are presented and studied to establish static and dynamic mathematical model of a proportional actuator. After reviewing the available magnetic-isolated rings, a novel magnetic grid magnetic-isolated ring is designed and optimized. Both simulations and experiments are applied in the magnetic grid magnetic-isolated ring proportional actuators to demonstrate its reliability. A comparative research between magnetic grid magnetic-isolated and traditional magnetic-isolated ring proportional actuators are carried out and the results show both of them have good static and dynamic characteristics.In chapter 4, a new scheme of electro-hydraulic flow control valve is presented, and its design principles and the mathematic model are introduced. The influence from the structure parameters of the valve are simulated and discussed by using ANSYS. The simulation model of the valve is established in AMESim to study the static and dynamic characteristics and the disturbance-resistant capacity. Both simulations and experiments show that the electro-hydraulic flow control valve has good static and dynamic characteristics and achieves required performances.In chapter 5, all achievements of the dissertation are summarized and the further research work is put forward.