Research On Automatic Pairing Measurement Of Servo Valve Small Orifice Parts

In a electro-hydraulic servo control system, electro-hydraulic servo valve which is the key part of the system connects the electrical part and hydraulic part and implements to hydraulic actuator's control. Nozzle and orifice are very important parts in servo valve, whose flow characteristic under various pressure differences directly affects the function of servo valve, and it is difficult to guarantee its service performance by measuring the dimension, so a high precise measuring instrument is urgently required. The twin flapper-nozzle electro-hydraulic servo valve has strict symmetric structure, so the pairs of nozzle and orifice are required which has consistent flow characteristics, and the process to select the pairs of nozzle or orifices is called as"pairing". At present, the domestic factories for servo valve mostly adopted manual measuring method to select the pairs of nozzle and orifices. This traditional method has heavy labor intensity as well as high error rate, so the pairing efficiency is very low, furthermore, it is difficult to obtain optimum pairing results.Based on the deep research of flow characteristics for the small orifice of nozzle, this dissertation firstly gives a description of pressure-flow measurement and pressure measurement of servo valve small orifice part taking a development of the whole measurement system and its several parts, including its hydraulic power, reusing oil system, pressure-control and temperature-control parts.Secondly, combining with virtual instrument technology this dissertation gives a deep research on the structure and mode of the measurement software based on state machine and case machine construction complete the software program.Thirdly, this dissertation gives a research on the pairing algorithms of pressure-flow measurement. According to the basic principle of greedy algorithm and different production occasions this dissertation proposes two kinds of algorithms which are optimal paring algorithm and most paring algorithm.Finally, by means of taking experiments on the measurement system the measurement accuracy and the correctness of the pairing algorithms are verified, then based on the automatic measuring software and database of the measurement system, the pairing program is accomplished.