Research And Application Of Dynamic Measuring Method Oriented To Aviation Automatic Test Equipment

With the rapid development of aviation science and technology, aviationautomatic test equipment is used widely. It is integrated equipment which is able toachieve intelligent diagnosis for aircraft airborne equipment, and its accuracy,reliability will directly affect the quality of aircraft security. Therefore how to insureits accuracy and quantity transfer unified has become Research focus recently.Around the measuring methods of aviation automatic test equipment, experts andscholars at home and abroad have done a lot of research work, and formed a relativelycomplete set of measuring methods. Nowadays the high-speed evolution of modernscience and technology and the emergence of new measuring method lead to theincreasingly urgent need for improving the traditional measuring methods. Thosetraditional methods dominated by static metrology are based on black box model todevelop measuring system without analyzing the dynamic characteristic inside, so theresulting model always loses dynamic information within the system. Furthermore,the level of accuracy of the measuring system is reduced. In addition, the research ofmeasuring method against characteristics of aviation automatic test equipment is notdeep enough. In the system identification method and the metrological modelimprovements and some other aspects, there is some space to improve.This paper presents a dynamic measuring method oriented to aviation automatictest equipment. Being different from the traditional static measuring methods, it dealswith static black box model using quasi-whitening to establish quasi-whiteningmeasuring model based on whole-system theory. Based on characteristics of aviationautomatic test equipment the author has developed dynamic measuring system and itsaccuracy grading methods. Moreover the author has studied metering periodcalculation method depended on parameter drift forecast, and the best calibrationperiod is recommended. Combined with engineering application, the measuringsystem is processed with typical experimental and applied research. The mainresearch contents are as follows:(1) The measuring model based on special noise structure and whole-systemtheory.Because of the limitations of identification accuracy and convergence speed for traditional black box model, connecting characteristics of aviation automatic testequipment this paper makes that model transparent to build Quasi-whitening modelthat can characterize the dynamic characteristics of the various links in the systeminternal. This model has improved the identification accuracy of dynamiccharacteristic for the measurement system. According to the high purity of inputcalibration source for aviation automatic test equipment and good environment forelectromagnetic shielding during metering procedure, the maximum likelihoodestimated input noise model with additional noise is defined as a constant. The outputcan be approximated that it only has observation noise. This special noise modelsimplifies the identification algorithm and improves the convergence speed.Experiments show that this measuring model based on special noise structure andwhole-system theoretical Quasi-whitening model can improve traditional model fromidentification accuracy and convergence speed. This model also can apply to systemidentification under the above experimental conditions.(2) The study on embedded self-measuring method.In engineering, almost all metrology for aviation automatic test equipment useexternal standard. It brings many problems, such as high expense, poor mobilityaccompanied by measurement of security and so on. This paper presents an embeddedself-measuring method. Though studying embedded measuring technology andconcerning the rich resources inside calibrated system, internal traceability chain isdesigned to trace autonomously until the highest level for internal traceability chain isformed. Some instruments which are not available to operate internal traceability tracefor external standard. This method improves measurable efficiency, meanwhile itreduces costs. For example, to a certain type of aviation test equipment in this paper, itwill need28sets of equipment, ten days in measuring and cost three million whencompletely adopt external measurement standards. However if we use embeddedself-metering method, it just need19sets of equipment, five days in measuring andabout one million in cost (equivalent to the cost of the embedded measurementtransformation) because it build two more hundreds of internal traceability andachieve the parameters of independent traceability. This method always suit to theother calibration of military automatic test equipment which in higher metering costs.(3) Dynamic measuring system oriented to aviation automatic test equipment.The master software and service software of automatic measurement have beendeveloped already which based on the programming technique with LabWindows/CVI,ATLAS and many other languages. The master software running onthe computer platforms of measurement system, responsible for initiating themeasurement request, receiving and processing the result of the test, service softwarerunning on the calibrated equipment of the computer platform, responsible forListening and implementation the measurement request, explaining measurement cooperation and controlling measurement process. Hardware interface adapter andsome of the metering module been designed, it combined various types of commonequipment and existing bus standards, developed dynamic measurement system ofaviation automatic test equipment. The system meets the design requirements, havingthe reconfigurable mechanical structure while can be used in other measuringequipment dynamic measurement which comply with the parameter range.(4) The evaluation method for uncertainty of dynamic measurement oriented toimproved MCM.The measurement uncertainty of the measuring system is the important part inmeasuring system while it is the main method to level the accuracy to the evaluationof measurement system. Analyzing error structure of common metering system,summarize the traditional GUM (Guide to the Expression of Uncertainty inMeasurement) and the method of MCM in assessment of dynamic measurementsystem has the shortage of high-dimensional wave and low accuracy. So this paperpurpose that change the MCM to quasi-random sequence so that improve the highdimensional uniformity of the high sample. The MCM method has equipped the fasterconvergence and higher accuracy of the assessment by test. At the same time, themethod can be used in other dynamic system or static measurement system to assessthe accuracy.(5) The study on parameter drift forecast and metering period calculationmethod oriented to aviation automatic test equipment.The parameter-drift-condition of automatic test equipment affects the equipmentreliability directly. It is always the basis to formulate the measurement cycle. Thispaper study the parameter drift forecast of the aviation automatic test equipment,proposing to improve the traditional forecasting methods base on the parameters ofthe least squares vector machines (LS_SVM) by increasing sparseness of training andthe robustness of training. Experiments show that the improved LS_SVM method hasthe higher prediction accuracy than traditional LS_SVM, and providing reliable datasource for calculate of best measurement cycle and it has the versatility especially tothe small sample space will has the better predict.(6) Application of dynamic measurement systemExperimental and applied research on the dynamic measurement systemformulated three different experimental platforms respectively test AWACS servohydraulic test system, the aircraft engine vibration measurement system and themachine radio meter. The achievement has been successfully promoted in aviationmaintenance measurement system and acquire second prize of scientific andtechnological progress in the military at present.This paper developed aviation automatic test equipment dynamic measurement system, achieving the dynamic measurement of a certain type of the aviation testequipment by dynamic measurement technology of aviation consolidated automatictest equipment. At the same time, the method and the technology can be applied to theother dynamic measurement of the automatic test system which has the samestructural characteristics.