Abstract
An electro-hydraulic servo valve is objectively asymmetrical in the process of fabrication and assembly, and the zero position is the result of comprehensive adjustment. During the use of the electro-hydraulic servo valve, the rapid rise of temperature will lead to the zero drift phenomenon and the change in the flow state of the servo valve. With the change in temperature, the thicknesses of air gaps, the size of the orifice, the flow coefficient, the armature’s arm of force, the permanent magnets’ reluctances, and the polarization magnetomotive force, the stiffness of the spring tube and feedback rod will act on the property of the torque motor and the pilot stage. Considering the factors of temperature and processing assembly on the zero drift of the electro-hydraulic servo valve, a mathematical theory model describing the temperature zero drift characteristics is constructed. When the temperature range is 20–270 °C, the analysis demonstrated that the control error of the servo valve will exceed the expected 15%. The temperature has the most significant effect on the servo valve through the flow coefficient. The initial installation angle deflection is the domain route on the temperature zero drift, and other factors have less effect. Compared with the experimental results, the temperature-induced zero drift model correctly calculates the control error trend of the servo valve caused by an increase in temperature, and it will contribute to improving the control precision of the servo valve.
Highlights
An electro-hydraulic servo valve is a precise control element combining mechanical, electronic, and hydraulic technologies, which is a key basic component in aerospace equipment
The hydraulic oil temperature of the electrohydraulic servo system can rise from normal temperature to over 200 ○C in a few seconds
By analyzing the composition of Eq (24), it is shown that the temperatureinduced zero drift model (TZD) model is a nonlinearity system, and the combined influence of temperature on the electro-hydraulic servo valve is not a superimposition of different routes
Summary
An electro-hydraulic servo valve is a precise control element combining mechanical, electronic, and hydraulic technologies, which is a key basic component in aerospace equipment. Aiming at the outstanding problem of temperature zero drift of the electro-hydraulic servo valve at extremely low temperature, Yin and Li26 used linear regression to analyze null bias experimental data at the different temperatures of the jet pipe servo valve. By analyzing the internal factors and assembly factors on the control accuracy of the servo valve after the temperature change, it is found that the flow coefficient is the main factor affecting the control precision of the electro-hydraulic servo valve. (3) The experiment for measuring the air gap length of the servo valve at different temperatures is proposed, which proves that the zero drift of the servo valve occurs after temperature changes. The servo valve zero position test bench is further designed to measure the current when the servo valve is maintained at zero position after temperature changes to validate the TZD model
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