Method of extended testability modeling for on-off multi-state system

The existing methods for testability-modeling have some constraints, including the consistency of failure criterion, failure transmitting and logical-value criterion of test. Aiming at states differences of on-off multi-state system, the method of extended testability modeling was proposed. Failure, test, D matrix and diagnostic tree were defined extended with the introduction of states, and an extended testability model was defined also. The algorithms for extended testability modeling and analysis were described, which include modeling, generations of extended D matrix and extended diagnostic tree. A hydraulic control system was taken as an example for the engineering application, which shows that this method is feasible and effective.