| As the important system indicators of new equipment which should be assessed inequipment acquisition, testability indices are attracting more and more attention frompurchaser, development unit and user. With the development of testability design andtestability engineering, many newly designed types of equipment have adopted thetestability technology and transferred to the verification stage. To accelerate thedemonstration of the equipments, both the producer and the consumer are seeking atestability verification technology which has the advantages such as short test period,better accuracy and lower cost. So the testability verification plays an important role intestability engineering. It is a theoretical and practical problem that to implement thetestability verification and evaluation considering the risk, cost, time and other testfactors.This research is supported by a ministerial pre-research project and national naturalscience foundation. This thesis is aiming to solve the problems involved in the practicaltestability tests, including difficult fault injection, high risk and cost, and long period.An overall testability verification scheme is proposed based on small sample theory andvirtual test. The key technologies of testability virtual verification are studiedsystematically.The major contents and conclusions of the dissertation are as follows.1. Design for overall testability verification schemeSome faults injections are difficult both in small sample tests and entire equipmentmodeling. An overall testability verification scheme, which combines the advantages ofsmall sample test and virtual test, is proposed to settle the difficulties. The technologyroute of virtual testability verification is emphatically illustrated. There are two keytechnologies in the virtual testability verification test which include the integratedfunction-fault-behavior-test-environment modeling technology and the fault samplesimulation technology.2. Integrated function-fault-behavior-test-environment modeling technology(1) According to the requirements of the virtual testability verification tests, anintegrated function-fault-behavior-test-environment model (FFBTEM) is proposed. Theconstituents of the FFBTEM including function, fault, behavior, test and environmentare analyzed and discussed. The mathematical definition and description of theFFBTEM and its submodels are provided. The relationships among the submodels areestablished and analyzed.(2) The modeling process and strategy of FFBTEM are discussed. The qualitativeFFBTEM modeling method and process based on extended multi-signal flow model arepresented. The object-oriented and hierarchical modeling strategy and multi-domain modeling theory are used to construct the quantitative FFBTEM. This method isfeasible in quantitative FFBTEM modeling.(3) The verification, validation and accreditation (VV&A) for FFBTEM is studiedin order to evaluate its accuracy and credibility. The concept and application procedureof FFBTEM VV&A are given. Credibility evaluation method based on analytichierarchy process and fuzzy synthetic evaluation is proposed.3. Environment-fault-test relation analysis and modeling(1) Aiming to measure the impact of the environment on the fault occurrence, anenvironment-fault coupling modeling method is studied. A qualitativeenvironment-fault relationship analysis method based on failure mode, mechanism,environment stress analysis and quantitative environment-fault relationship analysismethod based on grey relationship analysis are provided. The environment-fault factorcalculation method is given. This factor reflects the relationship between environmentstress and fault occurrence rate, which can be introduced to the fault statistical model tosimulate the generation of the fault sample.(2) In order to ensure similarity between virtual testability verification tests and thepractical tests, the uncertainty test modeling method is studied considering uncertainfactors. It is analyzed and pointed out that the main factors of uncertainty areenvironment effect, and uncertainty of parameters of the under test unit and testinstrument. An environment-parameter relation modeling method is provided based onleast square method considering the effect of the environment. The proposed methodcan be used to calculate the effect of the environment on the parameters. A randomparameter modeling method is proposed based on heuristic statistical modeling methodconsidering the uncertainty of the parameters. The parameters random deviation can besimulated based on this model. It is shown that the uncertain behavior of the test in thevirtual testability test can be simulated after introducing the quantitative effect of theenvironment and the parameters random deviation into the FFBTEM.4. Fault sample simulation technology based on fault statistical modelIn order to make the fault simulation sample more similar to the actual fault sample,more actual factors are considered in fault sample simulation, such as various repaireffects, maintenance modes, lifetime distributions and the effects of the environment.(1) In case of perfect repair, breakdown maintenance, exponential lifetimedistribution, and considering environmental effect, fault sample simulation approachbased on homogeneous Poisson process is proposed. The fault sample is carried out bystochastic simulation.(2) In case of perfect repair, breakdown maintenance or scheduled maintenance,various lifetime distributions, and considering environmental effect, fault samplesimulation approach based on renewal process is proposed. The fault sample is carriedout based on inverse transform method. (3) In case of minimal or imperfect repair, breakdown maintenance or scheduledmaintenance, and considering environmental effect, fault sample simulation approachbased on nonhomogeneous Poisson process is proposed. The fault sample is carried outbased on inverse transform method and thinning algorithm.The study indicates that the sample size and structure of fault sample simulationresults are similar to the actual results and reasonable.5. Case studyA missile control system is taken as the subject of application. FFBTEM and asemi-physical simulation test-bed are developed, on which the proposed virtualtestability verification test technologies are demonstrated. The application exampleindicates that the proposed theory and technologies in virtual testability verification testare scientific and feasible. They have good prospects for engineering applications owingto low risk and cost, high efficiency, and few restrictions on fault injection. |
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