Showing papers presented at "AUTOTESTCON in 1996"

Automatic analog fault simulation

Abstract: This paper presents an approach for using analog simulation together with artificial neural networks as a tool in the development of a test strategy. Relationships between circuit components and node states provided by simulation are used to create relationship matrices for a neural network. This approach provides a guide to diagnosing circuits by developing inferences about circuit component problems. The approach presented in this paper is a component of an automated test program generation (ATPG) concept. Problems associated with this approach are identified and defined. An industry accepted simulation engine generates data for operational circuit behavior. The simulation engine uses a netlist consisting of a to-from list, model definitions and an input description. Failures are simulated by one of two methods: (1) modifying circuit netlist, (2) modifying components. The circuit netlist is modified by adding opens and shorts to circuit nodes. The component models are modified by changing the component parameters within the component library. Simulation faults are chosen by the test program developer. Measures of component and node deviations from normal are used in the development of neural network matrices. An example analog circuit demonstrates the approach and typical results. This work may lead to development of a test strategy engine for automated analog test program development.

Simulation-based testability analysis and fault diagnosis

Abstract: In the past, system-level testability analysis and fault diagnosis have been largely based an either structure or manual cause-effect analysis (e.g. qualitative models, dependency models, multi-signal models, signed directed graphs). This process is time-consuming. This paper proposes a general methodology for automatically extracting multi-signal diagnostic inference models of systems via fault-simulation of design descriptions. Specifically it addresses the problem of generating inference models of digital/analog circuits and complex functional blocks (e.g. servo mechanisms, process control systems, flight control systems) for system-level testability analysis and fault diagnosis. The proposed method: (1) ensures a detailed failure-modes and effects analysis of systems, (2) automatically defines tests with well-defined stimuli, observations and test limits, (3) creates an efficient and intuitive test strategy by using test precedences and test levels, and (4) eases the process of inference model verification.

Thermal imaging is the sole basis for repairing circuit cards in the F-16 flight control panel

Abstract: When the card-level tester for the F-16 flight control panel (FLCP) had been dysfunctional for over 18 months, infrared (IR) thermography was investigated as a viable alternative for diagnosing and repairing the 7 cards in the FLCP box. Using thermal imaging alone, over 20 FLCP boxes were made serviceable, thus bringing the FLCP out of Awaiting Parts (AWP) status. In the current environment of downsizing, the problem of returning the card level tester to functionality is remote. Success of the imager points to corresponding inadequacies of the Automatic Test Equipment to detect certain kinds of failure. In particular, we were informed that one particular relay had never been ordered in the life of the F-16 system, whereas some cards became functional when the relay was the sole component replaced. The incorporation of a novel on-the-fly neural network paradigm, the Neural Radiant Energy Detection System (NREDS) now has the capability to make correct assessments from a large history of repair data. By surveying the historical data, the network makes assessments about relevant repair actions and probable component malfunctions. On FLCP A-2 cards, a repair accuracy of 11 out of 12 was achieved during the first repair attempt.

Optimal and near-optimal algorithms for multiple fault diagnosis with unreliable tests

Abstract: In this paper, we consider the problem of constructing optimal and near-optimal multiple fault diagnosis (MFD) in bipartite systems with unreliable (imperfect) tests. It is known that exact computation of conditional probabilities for multiple fault diagnosis is NP-hard. The novel feature of our diagnostic algorithms is the use of Lagrangian relaxation and sub-gradient optimization methods to provide: (1) near optimal solutions for the MFD problem, and (2) upper bounds for an optimal branch-and-bound algorithm. The proposed method is illustrated using several examples. Computational results indicate that: (1) our algorithm has superior computational performance to the existing algorithms, (2) the near optimal algorithm generates the most likely candidates with a very high accuracy, and (3) our algorithm can find the most likely candidates in systems with as many as 1000 faults.

Maintaining diagnostic truth with information flow models

Abstract: Most diagnostic systems today, whether applying a static test strategy or generating the strategy incrementally, assume a fixed configuration for the system being tested. Complex systems, including communications networks and adaptive control systems, may undergo many configuration changes during normal operation and test. In this paper, we present an approach to modeling system dynamics and coupling the dynamics to a diagnostic model for on-line test and diagnosis. We focus on the problem of maintaining current truth values as the diagnostic context changes and provide efficient algorithms that can be readily incorporated into information flow model-based diagnostic systems.

Selecting built-in self-test configurations for field programmable gate arrays

Abstract: In our previous work, we have described a built-in self-test (BIST) approach for RAM-based field programmable gate arrays (FPGAs), which exploits the reprogrammability of the FPGA to create BIST logic only during off-line testing. The cost is additional external memory required to store the BIST reconfiguration data, leaving all FPGA logic resources available for system functions. In this paper, the memory requirements as well as the testing time are minimized by selecting a few BIST configurations which provide high fault coverage for inspection tests at board and system manufacturing as well as for efficient system diagnostics and field testing.

Using boundary scan with a fault dictionary to test and diagnose clusters of non-scan logic

Abstract: The VICTORY boundary-scan toolset offers fault-dictionary diagnosis of virtual logic clusters, using the diagnostic data provided by a simulator. Using simulation software such as LASAR V6, a test developer can fault simulate the cluster-under-test and produce a fault dictionary in standard LSRTAP format. At run time on a tester, VlCTORY's Boundary-Scan Intelligent Diagnostics (BSID) module uses the LSRTAP files as part of its diagnostic database to isolate a reported failure and diagnose the fault. This paper discusses the implementation and requirements of this new capability, which is available for L-Series and ZI800-Series ATE as well as third-party testers.

C-17 O-level fault detection and isolation bit improvement concepts

Abstract: C-17 avionics built-in test (BIT) improvement is critical to mission readiness and capability. While many dramatic successes in 1995 led to the Department of Defense decision to build 120 C-17 airlifters, one area that still warrants improvement is a reduction in cannot-duplicate (CND) failure conditions. The primary goal of the MDA internal research and development (IRD a corresponding benefit is the transformation of raw recorded aircraft data into more useful maintenance information.

Guidelines for successful implementation of infrared thermography for repairing electronic circuit cards

Abstract: While the Air Force has not accepted infrared (IR) thermography as a universal diagnostic tool for repairing circuit cards, the personnel at Hill AFB have found IR thermography to be an effective diagnostic tool to an increasing variety of applications, particularly in the current environment of downsizing, where even the maintenance of the traditional automatic Testing Equipment (ATE) has become prohibitive. Using only the thermal imager and a functional tester, successful production has been achieved at the F-16 Avionics Intermediate Shop (AIS) and the Air Combat Maneuvering Instrumentation (ACMI) repair depot. Much of the success is keyed on the good design and software of the box-level testers, and a spirit of cooperation from shop personnel. Unfortunately a substantial percentage of Air Force ATE is unsuitable for use of IR thermography without reengineering of ATE software, hardware, and shop procedures, which should not be viewed as a deficiency of thermography because often a "hot mockup" or box-level tester is all that is required. This paper makes qualitative comparisons of these applications to other applications where success of IR thermography was not achieved. On the FLCP A2 card, for example, a repair accuracy of 11 out of 12 was achieved during the first repair attempt. In applications, such as the FLCP, where the card-level tester has been dysfunctional for more than 18 months. IR thermography at intermediate-level testers offers a viable alternative to traditional testing.

Using advanced tools to automate the design, generation and execution of formal qualification testing

Abstract: The paper describes the use of automated testing tools to improve the quality of operational flight program testing. Specifically this paper examines the use of Model Reference Technology, or MRT, to model the desired behavior of Operational Flight Programs, automate test generation and systematize software testing. Examples are given of the usage of TestMaster, a commercial MRT-based quality solution, in combination with automated test execution tools, such as AutoVal, to significantly improve the formal qualification testing process of an avionics mission computer subsystem.

A systems view of test standardization

Abstract: In test engineering, "system test" is frequently considered to be testing at a particular level in a product hierarchy. With increasing complexity in systems, testing at lower levels is now faced with problems previously encountered at the system level. For this reason, it is becoming increasingly important to apply a system perspective to testing. In this paper, we present a model of a "system" to be applied to test engineering which abstracts test information above the physical level of the product. We then describe how this model supports two standardization efforts within the IEEE-P1226 and P1232.

Application scenarios for AI-ESTATE services

Abstract: One of the principal objectives of the P1232 AI-ESTATE standardization project is the development of a standard set of services to be provided by a diagnostic reasoner within a test environment. Recently, considerable progress has been made defining an initial set of services for P1232.2 AI-ESTATE Service specification. In this paper, we provide several possible scenarios under which such services may be used within a test environment. We describe these scenarios using state diagrams and then demonstrate how one might use the defined set of services to provide the functionality required by these scenarios.

Hierarchical test generation: Taking boundary scan to the next level

Abstract: Development of the original IEEE 1149.1 boundary-scan standard in 1990 was motivated primarily by concerns about the complexity of testing increasingly dense printed-circuit board assemblies in manufacturing. As a result, most test generation efforts have been targeted at unit test, which is most applicable to testing MCMs and boards. As boundary-scan technology has matured, there is a new focus on extending the technique to testing all levels of an assembly's hierarchy, at all phases in its life cycle.

An open architecture COTS tester with intelligent diagnostics

Abstract: This paper describes a new Business Model for ATE companies-combining commercial off-the-shed open architecture standards with advanced technology to capture business for both military and commercial customers.

An experiment in encapsulation in system diagnosis

Abstract: The maintenance of fighter aircraft has become increasingly problematic as evidenced by the numerous studies and research and development projects (both contracted and independent) that have addressed the problem in recent years. As a result of these efforts, the "easy" problems have, at least to some extent, been attacked and remedied. The more intractable problems remain. Because of this, the sponsors of the Aircraft Maintenance Integrated Diagnostics Demonstration (AMIDD) project perceived that the application of traditional methods used to perform maintenance and diagnostics have begun to produce diminishing returns. Thus, non-traditional methods using advanced diagnostics appear to hold the most promise for alleviating the difficult diagnostic problems currently faced. In this paper, we describe the initial results of an AMIDD experiment with advanced diagnostics that demonstrate some potential improvements for aircraft maintenance associated with using these methods.

An overview of IEEE P1232 AI-ESTATE. The standard for intelligent reasoning based systems test and diagnosis arrives

Abstract: Artificial Intelligence (AI) technology promises to ease cost and improve the supportability of new and existing systems. Many products are available which use AI techniques to assist in test and diagnosis of system malfunctions. The US military is currently deploying support equipment and primary systems which make use of AI in meeting their mission requirements. However, the lack of standard interface between these reasoning systems, their users and the support equipment which they control is preventing the achievement of many potential long-term benefits, and could cause loss of configuration control, as well as long-term support problems. Current test standards, such as IEEE 716-1995 (C/ATLAS), IEEE 993-1993 (TEDL), IEEE 981-1993 (RDL) and the IEEE 1029.X series of automatic test program generation (ATPG) standards provide no guidance regarding the use of AI techniques and test applications. Proposed AI standards, including Knowledge Query Management Language (KQML), Knowledge Interchange Format (KIF) and IEEE P1252 (IMKA), do not specifically address test and diagnosis applications. In February 1990, the IEEE approved Project Authorization Request (PAR) 1232 authorizing the IEEE Standards Coordinating Committee 20 (SCC-20) to begin development of a new test standard to fill this void, entitled AI-ESTATE. AI-ESTATE, as proposed in the recently submitted full use PAR 1232, stands for Artificial Intelligence Exchange and Service Tie to All Test Environments. AI-ESTATE encompasses all of Artificial Intelligence as it relates to test and diagnosis. AI-ESTATE will define the interfaces between a test related reasoning system, its users, target test equipment, test information knowledge bases and more conventional databases. AI-ESTATE will also define several test related knowledge and databases, including Fault Trees, Enhanced Diagnostic Inference Models and Constraint Models. This paper will define AI-ESTATE, discuss its background history, long term goals and architecture, its current status and the committee's plan of action for continuing development of the standard.

Maintenance and Repair Support System (MARSS)

Abstract: The MARSS is the first integration of soldier and machine optimized for maintenance. It is a lightweight, open architecture, wearable personal computer with object oriented software that controls and integrates plug-in measurement instrumentation, diagnostics processes, interactive electronic technical manuals, and logistic databases for the soldier. Input and output to the system is by means of a head-mounted microphone and a flat-panel active matrix display. MARSS has wireless Local Area Network (LAN) interaction with the weapon system data bus and members of the maintenance team, allowing transmission of fault or diagnostic data. It contains multimedia repair and replace instructions on small, high-density, removable PCMCIA disks. Flexible board technology provides soldier comfort. The open architecture allows easy upgrading of the hardware and software, including new tools as they become available. New battery technology consists of very small, flat, flexible batteries producing six hours operation.

Encapsulation and diagnosis with fault dictionaries

Abstract: To date, test and diagnosis has been domain knowledge driven. However, as system complexity grows and we strive to develop reusable components, the concept of encapsulation becomes increasingly important. Encapsulation embodies the concepts of separation and partitioning. In this paper we deal with encapsulation by illustration of the fault dictionary approach to digital electronics. We then extend the concept of encapsulation to the system test approach as well as the development of maintenance systems. Finally we develop the concept that encapsulation is a key element in achieving general standardization open system architectures.

A Commercial Off The Shelf (COTS) solution to Air Force aircraft engine test requirements

Abstract: The Air Force currently uses three test systems to test aircraft engines-the Automated Ground Engine Test System (AGETS), the Engine Test/Trim Automated System (ETTAS), and the Pacer Comet III. All three are based on 1970's and early 1980's technology, and are therefore aging and becoming more difficult to maintain. This is due to obsolescent hardware, some proprietary hardware, and, in some cases, an out-of-date software environment. SA-ALC/LDAD, the engine tester program management office, has placed Sunset Resources, Inc. (SRI) on contract to produce a COTS component replacement study and prototype for the ETTAS. This paper details the COTS solution being developed, using the VXIbus technology. Included are discussions on the decisions and methods used to increase data throughput, both in hardware and software. The paper also discusses the implementation of LabVIEW 4.0 as the test system software environment, and Windows 95 as the operating system. The paper details how we were able to greatly increase the performance of the system over the current ETTAS.

Implementing reusable, instrument independent test programs in the factory

Abstract: Development of computer programs that control test sequences on automatic test equipment (ATE) is costly and time consuming. Test programs are usually written by specifying the instruments to be used in the ATE and the sequence of the setup and measurement parameters for these instruments. Reuse of test program software on other ATE is usually not possible without rewriting, revalidating and re-releasing the programs. This paper describes an implementation of a test program software development system and a standard software runtime architecture used in factories. The object oriented development environment and its associated class libraries allow test programs to be written without knowledge of the ATE on which they will be run, Two main principles guided the design: the software architecture was based on recognized formal and industry standards, and our implementation used commercial on-the-shelf software products when possible. Emerging standards such as the IEEE-1226 (ABBET) as well as de facto industry standards including VXI Plug and Play have made our implementation possible. The current draft of the ABBET and P&P standards do not promote this instrument independence, but it is hoped that this will be added as the standards mature. Three immediate benefits are: cost savings that result from reusing validated test programs, cycle time reductions that result from concurrently developing test program software and ATE, and software defect reductions that result from using proven software.

Automatic dependency model generation using SPICE event driven simulation

Abstract: Intelligent Automation, Incorporated, (IAI) with the U.S. Army Communications and Electronics Command, is developing a system called MIDIS (Microelectronic Display). MIDIS is comprised of two tools: one for designing built-in testing and diagnosis of printed circuit boards and one for automatically generating dependency models and performing testability and diagnosability analysis. This paper focuses on our method of generating dependency models using a SPICE simulator. We use two separate modules to perform this function. The first module is based on fault propagation analysis using an event-driven simulator. Each component in the SPICE netlist is replaced with a fault propagation model, which models both the component's fault propagation properties and its failure modes. In turn, every component enters faults into the simulation and we record how the failure modes of all components propagate to each test point. The totality of these runs yields a dependency model for the system. The event-driven simulation is fast but gives only an approximate view of the true system dependencies. Once the analysis yields good results, we turn to the second module. Here, a full analog SPICE simulation is run for every failure of each component. The readings at each test point are compared to the nominal (no-fault) readings to determine whether a fault is detectable. This process is repeated for the individual failure modes of all components, yielding the full dependency model. Unfortunately, for complex circuits this can be very slow. Our two-tier structure greatly reduces the number of times the full SPICE analysis is required.

Approaching a universal E-O test collimator

Abstract: The downsizing of the U.S. military budget has led efforts towards development of multi-purpose electro-optic (E-O) test collimators for testing multiple E-O systems. This has led to the DOD policy of equipment standardization and the use of non-developmental Items (NDI) and commercial-off-the-shelf (COTS) items to the maximum extent possible. These efforts have lead to thought about the possibility of making a "universal collimator", which could test everything from the oldest, to the newest and most sophisticated ground, tank, and aircraft fire control systems. Is a universal collimator possible? Can we expect to see a universal collimator in the near future? The authors conclude a truly universal collimator may not be possible, but that a more modest, scaled down, "practically" universal collimator is realizable today.

New standards-based software enhances real-time I/O performance

Abstract: Today's data acquisition and control system designers are being challenged by ever-increasing channel counts, higher scan rates end the demand for faster real-time performance in the systems that they must configure. To meet these needs, KineticSystems Corporation has derived the Reality software package through technology transfer from the Department of Energy. This paper describes the open client/server architecture of the Reality software package. The host software runs on UNIX-based workstations end communicates with the I/O chassis using TCP/IP protocol. The key to the high I/O performance is the use of VxWorks/sup (TM/), a rest-time kernel, in the controller for each I/O chassis. Also described is how this software includes intelligent data acquisition as well as real-time display, analysis and control. In order to provide the high transfer rates needed for the acquired data from a number of VXI I/O chassis to a hard disk, this software can be combined with a high-speed fiber-optic interconnect. This paper also describes two large applications where this software is being employed. They include the monitoring of static end dynamic data from large wind tunnels and the testing of rocket motors. Additionally, this software fulfils the Department of Defense directive to use COTS (commercial-off-the-shelf) products, based on recognized standards, whenever possible. Also discussed is the quite positive experience with technology transfer and the benefits derived by the US Government as well as by the commercial marketplace.

Making the bridge between two worlds-post-processing LASAR data into a test language

Abstract: If is accepted by everybody that the TPS development challenge can only be won with the intensive use of TPS software tools. One of the most proved and used tools in digital TPS Development are the digital simulators (like LASAR and HITS). However, their use and integration with ATEs and other tools is difficult and requires lot of workaround. This paper places a focus on possible solutions and describe the solution adopted at OGMA, SA. Special attention was placed on practical issues and results are displayed.

System synthesis models as a standard DoD tool for automatic test system analysis, selection, and development

Abstract: System synthesis models (SSM+), a critical part of the consolidated automated support system (CASS) introduction planning process, is also used as a valuable decision support tool in the automatic test system (ATS) selection process. SSM+ is used to identify the limitations of various candidate ATS for supporting a weapons system platform or set of Units-Under-Test (UUTs). SSM+ can be used to identify potential ATS product improvement efforts and to assist in the development of reconfigured or downsized ATS stations. A potential application of SSM+ addressed herein is the assignment of UUTs to operational test program set (OTPS) groups based on common mechanical interface requirements and exceptions as well as the development of a family of common interface devices. Although only military examples are discussed herein, SSM+ would have similar potential applications in the commercial world.

Data collection and recording guidelines for achieving intelligent diagnostics

Abstract: Whether using human or machine intelligence, the best decisions are made when using all available information from all relevant sources. In contrast to traditional automatic test equipment (ATE) programming techniques, which stop on failures to perform a diagnosis, we would collect from the entire sequence of electronic tests, and integrate these data with circuit topology and external data (including thermal imaging) to obtain a best informed diagnosis. Novel on-the-fly neural network paradigms provide the capability to make correct assessments from a large history of repair data. Applications with these paradigms require a computer with sufficient horsepower (such as a PC) and high-level programming languages. The circuit topology assessment program can identify "dead" nodes through an entropy calculation, making it possible to perform circuit diagnosis in the absence of good/bad historical information. In theory, this technique could be applied to any automatic test equipment platform, provided that the data collection activities were in place.

Using neural networks to solve testing problems

Abstract: This paper discusses using neural networks for diagnosing circuit faults. As a circuit is tested, the output signals from a Unit Under Test can vary as different functions are invoked by the test. When plotted against time, these signals create a characteristic trace for the test performed. Sensors in the ATS can be used to monitor the output signals during test execution. Using such an approach, defective components can be classified using a neural network according to the pattern of variation from that exhibited by a known good card. This provides a means to develop testing strategies for circuits based upon observed performance rather than domain expertise. Such capability is particularly important with systems whose performance, especially under faulty conditions, is not well documented or where suitable domain knowledge and experience does not exist. Thus, neural network solutions may in some application areas exhibit better performance than either conventional algorithms or knowledge-based systems. They may also be retrained periodically as a background function, resulting with the network gaining accuracy over time.

Development of a TPS reuse library using COTS tools

Abstract: In the past, functional test requirements (FTR) or test requirement documents (TRD) and test program sets (TPS) were standalone items developed by individual engineers. In some cases one engineer would write the FTR/TRD and another would develop the TPS. Commercial ATLAS FTRs are prepared in ARINC 616 and 626 ATLAS. Military TRDs are written in IEEE ATLAS 716 versions. Previous test reuse attempts have not been successful because additional software, like browsers, is required to support these efforts. It was difficult to justify writing new software (for example browsers) to manage the application software. Today, commercial off the shelf (COTS) tools are in place to browse and view information from circuit diagrams to documents to source code. These tools can develop hierarchies to organize the information. These COTS tools are available throughout Boeing on many types of workstations and personal computers on every engineer's desk. This paper discusses how a reusable test library (RTL) is being developed using commercial off-the-shelf (COTS) tools such as Mosaic to address commercial and military test applications. It describes each of the tools and the process to develop TPSs using the reuse library. It defines the metrics and the benefits achieved.

Automatic generation of dependency models using autonomous intelligent agents

Abstract: Dependency models are the basis of several important products for testability analysis, diagnosability analysis, and generation of optimal fault trees including generation of dynamic test strategies based on current parameters and available resources. The AI-ESTATE Committee of the IEEE SCC20 is working on a standard representation of dependency models (IEEE 1232.1) and once that is formalized, the resulting increased portability and re-usability of models will make dependency models even more important. The problem with dependency models is that they are difficult to generate. Dependency models generated from netlist information alone are close to useless. Dependency models can also be generated via a circuit simulator, but these run very slowly and for complex circuits, this is not feasible. Intelligent Automation, Inc. (IAI), together with the U.S. Army Communications and Electronics Command, is developing a new approach to automatic generation of dependency models. The approach is based on use of "intelligent agents". Intelligent agents may also be useful for other aspects of the problem of testing and diagnosing complex electronic circuits, and our success in the automatic generation of dependency models has led us to begin studying other applications of agents in this domain. There are two key benefits of implementing software using the paradigm of autonomous agents. First, agents are independent and asynchronous, which means they can run on any number of computers which might be available as long as the computers are networked together. The second benefit is ease of implementation. The work reported here was done as an experiment in the use of autonomous agents and not with the goal of implementing a usable system.

Integrated diagnostics: confusion and solutions

Abstract: This paper discusses the definition of integrated Diagnostics (ID), and some of the common misconceptions of what constitutes ID. As ID represents a powerful method for ensuring that weapon systems are developed with diagnostics capabilities that are both comprehensive end cost effective several proposals for enhancing and extending its application are proposed.