Research And Development Of Testing Platform For Pneumatic Measuremet Of Valve Error Based On Electromagnetic Theory

The buoy air gauge is a kind of non-contact measuring instrument with highprecision. It is so convenient, accurate, economical and practical that it is widely used inall fields of industry. According to its measuring principle, once the buoy gets balancedin the tipper pipe, the pressure difference above and below the buoy is constant. This isan advantage outstanding than any other method in the field of overlap measurement,for its high linearity and large linear scope. However, under the epoch whenmanufacture is in the trend of automation and intelligentialization, traditional air gaugeis limited because of its difficulty in transferring pneumatic to electricity. On the otherhand, the differential inductors sensor in displacement can transfer pneumaticdisplacement into accurate electrical signal, which exactly compensates the defect of airgauge. Moreover, its performance is steady and is easy for the implement of automation.Thus, this dissertation will develop a novel set of pneumatic-electric convertorwhich is used to measure the overlap of a spool valve used in hydro-electric servo valve.It transfers the displacement of a buoy into electrical signal with the theory ofdifferential inductors sensor in displacement, to implement transformation frompneumatic to electricity. And by models like amplification and A/D, the signal will bedisplayed. This set of convertor was then applied to the overlap automation measuringsystem.In the second part of this dissertation, the principle of the whole measuring systemwas demonstrated, including the principle of buoy gauge, principle of differentialinductors sensor and measuring method of overlap. Then, the size and weight of thebuoy were designed by deducing the air circuit equations. Moreover, the parameters ofthe buoy were optimized.In the third part of this dissertation, the design process of the high-precisionlarge-scope differential inductor was introduced. Firstly, the relationship between outputvoltage of the inductors and the displacement of the buoy was deduced. Then, thesensitivity was calculated to optimize parameters. Factors for nonlinearity error wereanalyzed and compensation inductor was designed. Finally, parameters for the inductorwere decided, which can meet the project requirement.The fourth part of this dissertation is about the composition of the measuringsystem, including the air circuit, mechanical part, electronic circuit and softwareprogram. In the end, the result was testified in the last part of the dissertation byexperiments. Property of the air circuit and differential inductor were also tested andcalibrated. Results show that the measuring system works very well and can meet the project requirement.