Diagnostician Theory of Operations

One of the most significant innovations in test programming is Giordano Automation's Concurrent Engineering Tool Set (CETS). CETS consists of a development tool and a run-time tool. The run-time tool, Diagnostician, provides automated diagnostics in the test environment, and is seamlessly integrated into any test system configuration. The development tool, the Diagnostic Profiler, assists the engineer in preparing the run-time diagnostic knowledge base.

The Diagnostician is an implementation of a new paradigm for diagnostics: model-based reasoning. Model-based reasoning means that a diagnostic model of a system or item, derived from design data, serves as the basis for diagnostic reasoning. The diagnostic model is independent of the source of test result data and independent of the sequence of tests that are run. The Diagnostician contains a UUT diagnostic model in the form of a connectivity matrix which represents the propagation of faults (rows in the matrix) to observable measurement locations and the coverage of tests that Pass or Fail (columns in the matrix). When used in run-time, the software algorithms and knowledge base (matrix) operate to isolate faults without troubleshooting sequences and without hard-coded diagnostic test programs.

In the new paradigm, a model-based diagnostic software object called a Diagnostician is used in lieu of programmed No-Go flow paths. In run-time the Diagnostician provides dynamic fault isolation without complex diagnostic test programs. In run-time, the object or Diagnostician , is utilized to interact in real time with the test results to perform fault isolation. The concept of object oriented programs is taken full advantage of by dealing with the diagnostic logic as an independent entity in the test program. By thus separating diagnostic logic from test, the test program becomes significantly simpler. Further, the diagnostic logic contained in the software object can be rehosted to any platform without any problem.

Using the Diagnostician, the fundamental culture of diagnostics has been changed. Tests are discrete software programs and routines which may be independently executed. The interpretation of the tests is done by the Diagnostician which dynamically, on-the-fly, interprets test information based upon all information it receives in any order. The Diagnostician makes use of Artificial Intelligence in the form of Set Covering Algorithms that interpret the Cones of Evidence produced by both pass and fail data from the test results. In this type of test program structure, no code is duplicated. The list of faults is clearly identified and diagnostic data for each fault is kept in one spot. Model-based reasoning makes diagnostics affordable for limited production testing and effective for complex system and board test.

The Diagnostician is structured as a library of functions. This library of functions is compiled to different operating systems. For example, for Windows 3.x, the Diagnostician is compiled as a Dynamic Link Library. This allows for tremendous flexibility for integration onto actual run-time platforms and software systems.

1. The test results can be entered into the Diagnostician from any source, in any order, and as many or few at a time as the application warrants. This tremendous flexibility is provided by the internal structure of the model that is used for diagnostic reasoning - the model is in a matrix format, as opposed to a "fault tree" structure.
2. The Diagnostician uses both pass and fail cones of evidence, mapped across the matrix format to obtain fault isolation call-out. It also includes a minimum set covering algorithm to speed processing and improve diagnostic resolution.
3. The flexibility of the internal structure enables operating modes that fit into a broader set of operating environments than typical expert diagnostic systems, especially automatic test equipment and embedded applications, which typically involve reading of large sets of test result data provided in an instance, as opposed to one test result at a time which is used to flow through a static test tree or fault flow diagram.
4. The model structure and the algorithms allow for multiple independent and multiple dependent, or common mode failures to be isolated.

Use of the Concurrent Engineering Tool Set for Automated Diagnostics - A Comparison with the Traditional Approaches

Show me Tool Set for Generation of Knowledge Bases

CETS Advantages / Users / Questions and Answers

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Last modified: June 30, 2000