Electrohydraulic servo valves were developed during World War II due to higher requirements for the rapid dynamic accuracy of control systems by military equipment such as aircraft and were gradually used in civilian and industrial equipment after the war. It is a hydraulic control valve that accepts analogue electrical control signals and outputs analogue flow and / or pressure in response to changes in the size and polarity of the electrical control signals. According to the different hydraulic amplifier, divided into nozzle baffle servo valve and jet tube servo valve. Electrohydraulic servo valve with small size, high power amplification, good linearity, fast response, stable and reliable movement, can adapt to analog and digital adjustment, etc., in a variety of electro-hydraulic servo system has received special attention. Electro-hydraulic proportional valve is for servo control there are such as power loss, high requirements for hydraulic filtration, manufacturing and maintenance costs, and it provides rapid response in the general industrial equipment often do not need to use the situation, in the traditional On-off valve developed on the basis of. Electro-hydraulic proportional valve can be based on the input electrical signals, the proportion of the working fluid pressure, flow and direction of control. Proportional valve development of the initial stage, only the proportion of electromagnet instead of ordinary hydraulic valve switch electromagnet or adjust the handle, the working frequency is small, steady-state hysteresis large, only for open-loop system. From the mid-1970s to the early 1980s, proportional valves began to adopt a variety of internal feedback principles, high voltage, proportional solenoid and proportional amplifier technology matures. The working bandwidth of the valve reaches 5 ~ 10 Hz, and the steady-state hysteresis is reduced to about 3%. After the 80s, the proportional valve was designed with pressure, flow, displacement feedback and electric correction and other means, so that the steady-state valve accuracy, dynamic response and stability have been further improved. In addition to the median there is still some dead zone, the control performance and servo valve closer. More Search Keywords: Valve
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