Showing papers presented at "AUTOTESTCON in 2011"

Research on features for diagnostics of filtered analog circuits based on LS-SVM

Abstract: Feature selection techniques have become an apparent need for diagnostic methods such as a least squares support vector machine (LS-SVM). Most researchers use wavelet transform coefficients of the time-domain transient response data obtained from filtered analog circuits as features to train a LS-SVM classifier to diagnose faults. But wavelet coefficient features have certain disadvantages such as no physical meanings. Thus, in this paper, two new feature vectors with clearly defined meanings based on a time-domain response curve and a frequency response curve of a filter are proposed, respectively. In addition, a statistical property feature vector which represents global properties of the time-domain response curve or the frequency response curve is proposed. The results from the simulation data and real data for a biquad filter showed the following: (1) these proposed conventional time-domain and frequency features, which are already familiar to designers of filtered analog circuits, have good diagnostic accuracy—all above 91% for the example circuit; (2) the best accuracies using the proposed statistical property feature vector are 100% for time-domain simulation data, and for both real experiment data ; (3) the diagnostic accuracy using the proposed combined feature vector is more accurate than conventional feature vectors; (4) an LS-SVM can be used to diagnose faults in a real analog circuit that only has a few fault samples.

Integrated model-based and data-driven fault detection and diagnosis approach for an automotive electric power steering system

Abstract: Integrity of electric power steering system is vital to vehicle handling and driving performance. Advances in electric power steering (EPS) system have increased complexity in detecting and isolating faults. In this paper, we propose a hybrid model-based and data-driven approach to fault detection and diagnosis (FDD) in an EPS system. We develop a physics-based model of an EPS system, conduct fault injection experiments to derive fault-sensor measurement dependencies, and investigate various FDD schemes to detect and isolate the faults. Finally, we use an SVM regression technique to estimate the severity of faults.

Diagnostic alarm sequence maturation in timed failure propagation graphs

Abstract: Diagnostic model development presents a significant engineering challenge to ensure subsequent diagnostic processes using such models will yield accurate results. One approach to developing system-level diagnostic models that has been receiving attention is the Timed Failure Propagation Graph (TFPG), developed at Vanderbilt University. Unfortunately, developing TFPG models is also difficult and error-prone. In this paper, we extend previous work in using historical maintenance and diagnostic information to identify potential errors in the TFPG-based diagnostic models and recommend ways of maturing these models. This is done by extending the maturation process to incorporate historical alarm sequences and to model these sequences using a probabilistic transition matrix (similar to a Markov chain). The resulting sequence model is compared to the causal relationships identified in the original TFPG to discover discrepancies between the two. Potential sequence modeling errors with recommendations are given back to an engineer or analyst. We report on the maturation process and algorithms and also provide preliminary experimental results.

On-line adaptive data-driven fault prognostics of complex systems

Abstract: Data-driven prognostics based on sensor or historical test data have become appropriate prediction means in prognostics and health management (PHM) application. However, most traditional data-driven forecasting methods are off-line which would be seriously limited in many PHM systems that need on-line predicting and real-time processing. Furthermore, even in some on-line prediction methods such as Online SVR, there are conflicts and trade-offs between prognostics efficiency and accuracy. Therefore, in different PHM applications, prognostics algorithms should be on-line, flexible and adaptive to balance the prediction efficiency and accuracy. An on-line adaptive data-driven prognostics strategy is proposed with five different improved on-line prediction algorithms based on Online SVR. These five algorithms are improved with kernel combination and sample reduction to realize higher precision and efficiency. These algorithms can achieve more accurate results by data pre-processing, moreover, faster operation speed and different computational complexity can be achieved by improving training process with on-line data reduction. With these different improved Online SVR approaches, varies of demands with different precision and efficiency could be fulfilled by an adaptive prediction strategy. To evaluate the proposed prognostics strategy, we have executed simulation experiments with Tennessee Eastman (TE) process. In addition, the prediction strategies are also tested and evaluated by traffic mobile communication data from China Mobile Communications Corporation Heilongjiang Co., Ltd. Experiments and test results prove its effectiveness and confirm that the algorithms can be effectively applied to the on-line status prediction with excellent performance in both precision and efficiency.

A non-destructive high-voltage low-energy intermittent fault location system

Abstract: The practical implementation of a high voltage/low energy portable tool is discussed to address the need for intermittent fault diagnostic solutions. Recent results from aircraft testing are reported, safety validation is discussed and future system upgrades are addressed to support ease of use as a field diagnostic tool.

Modeling of jitter and its effects on time interleaved ADC conversion

Abstract: Post analog-to-digital conversion correction is an active area of research in both academia and industry due to the high potential of positive impact in areas like Synthetic Instrumentation (SI), Software Defined Radio (SDR), RADAR, etc. This paper introduces a high fidelity Simulink™ based behavioral error model for time-interleaved analog-to-digital converters (TI-ADCs) to facilitate development of efficient post conversion correction algorithms for TI-ADCs. Theoretically TI-ADCs offer a technologically feasible and cost effective solution to the digitization of wide bandwidth analog signals. The contribution of the error model described in this paper solves a key obstacle in economical research and development in this area. In addition to the error sources associated with integrated high performance analog to digital converters ADCs, mismatched error sources affect the performance of time interleaved configurations.

Ontology-guided knowledge discovery of event sequences in maintenance data

Abstract: We created an application that facilitates improved knowledge discovery from aircraft maintenance data by transforming transactional database records into ontology-based event graphs, and then providing a filterable visualization of event sequences through time. We developed OWL ontologies based on formally defined IEEE standards, and use these ontologies to guide the data mining and data transformation processes. Our application removes much of the users burden for data look-up and greatly increases the potential for knowledge discovery from data (KDD) in this field. We provide an easy-to-use interface that generates relevant sequences of data in a meaningful context in a fraction of the time it would take domain experts to retrieve and display similar information.

Multiple model moving horizon estimation approach to prognostics in coupled systems

Abstract: The key objectives of this paper are to analyze and implement a novel moving horizon model predictive estimation scheme based on constrained nonlinear optimization techniques for inferring the survival functions and residual useful life (RUL) of components in coupled systems. The approach employs a data-driven prognostics framework that combines failure time data, static and dynamic (time-series) parametric data, and the Multiple Model Moving Horizon Estimation (MM-MHE) algorithm for predicting the survival functions of components based on their usage profiles. Validation of the approach has been provided based on data from an electronic throttle control (ETC) system. The proposed prognostic approach is modular and has the potential to be applicable to a wide variety of systems, ranging from automobiles to aerospace.

Comparing software design for testability to hardware DFT and BIST

Abstract: Software is replacing hardware whenever possible, and this trend is increasing. Software faults are every bit as pervasive and difficult to deal with as hardware faults. Debugging software faults is manual, time consuming, often elusive and since they affect all systems deployed, most often they are critical. Design for Debugging would ensure that a software package can be readily debugged for any software fault. A comprehensive software test, however, is intended to eliminate the need for ad hoc debugging and ideally all “bugs” (we call software faults) would be caught and identified by the software test. Thus, it is imperative that the software community adopt means to ensure that software components are designed in a way that will detect and isolate software faults. This requirement is familiar to designers of hardware systems. Could the discipline of hardware design for testability (DFT) and Built-In [Self] Test (BIST) apply to software design for testability? The purpose of this paper is to discuss how many of the testability requirements and techniques for hardware DFT can be applied to software.

An integrated Automatic Test Generation and executing system

Abstract: This paper presents an integrated Automatic Test Generation (ATG) and Automatic Test Executing/Equipment (ATE) system for complex boards. We developed an ATG technique called Behavior-Based Automatic Test Generation technique (namely BBATG). BBATG uses the device behavior fault model and represents a circuit board as interconnection of devices. A behavior of a device is a set of functions with timing relations on its in/out pins. When used for a digital circuit board test generation, BBATG utilizes device behavior libraries to drive behavior error signals and sensitize paths along one or multiple vectors so that a heavy and complicated iterating process can be avoided for sequential circuit test deductions. We have developed a complete set of test executing software and test supporting hardware for the ATE which can use the BBATG generated test data directly to detect behavior faults and diagnose faults at the device level for complex circuit boards. In addition, we have proposed and implemented useful technique, especially Design For Testability (DFT) [1][2] application technique on the integrated system, so the test generating/executing for complex boards with VLSI can be further simplified and optimized.

Cost impact of automated acceptance testing of Electrical Ground Support Equipment for spacecraft testing

Abstract: In today's environment, building a reliable and cost-effective spacecraft is perhaps emphasized more than ever before. Sponsors are looking for the same high-quality products but at lower costs and with shorter schedules. Whether it is a spacecraft for the Department of Defense (DoD), a research observatory for the National Aeronautics and Space Administration (NASA), or a commercial communications satellite, total cost is a significant factor.

Why did we add LabVIEW applications to our ATLAS TPSs

Abstract: It is important to keep an open mind and be practical with testing software and hardware. Test Program Set (TPS) transportability is a primary consideration for long term customer support goals. Our ATLAS TPSs are robust and user friendly, however, LabVIEW offers several features and state-of-the-art routines and graphical representations that are valuable in many testing techniques or applications. Also, an interoperable open system software test package is an excellent approach to state-of-the-art technology. Vital testing techniques require expansive open systems.

When should intermittent failure detection routines be part of the legacy re-host TPS?

Abstract: Intermittent failures are failures that do not manifest themselves all the time. The fact that they are sometimes there and sometimes aren't can make them very difficult to analyze.1 Some of the most difficult to diagnose faults are intermittent. It is very difficult to isolate intermittent faults which occur with low frequency.2 Intermittent electrical faults, as a rule, are notoriously difficult to detect. Sometimes an intermittent short or open circuit may leave visible signs of overheating or micro-arcing on a printed circuit board or a connector, but at other times damage may be on such a microscopic scale that it is likely to go undetected.3 The inability to find anything wrong by trying to reproduce the incident is no guarantee of the detection of an intermittent fault. This paper will discuss various ways to detect intermittent failures. The paper will discuss the root causes of intermittent failures. Also, a discussion will take place that addresses why we must pursue new techniques, methods and technologies to detect elusive failures.

BIT/BITE/ED/EP/IVHM and ATE in DA

Abstract: Automatic test equipment (ATE) in the Department of the Army (DA) finds itself in an ever challenging and changing role in an effort to support the Future Force of the 21st century. Challenging in that the ATE today must combat obsolescence while supporting both the legacy and future systems; and changing in that Army Transformation is transitioning from four (4) to two (2) levels of maintenance support. Advances in technology in the areas of built-in-test (BIT), built-in-test equipment (BITE), embedded diagnostics (ED), embedded prognostics (EP) and integrated vehicle health management (IHVM) have been the primary enablers allowing the DA to make major changes in maintenance, test philosophy and logistics in order to reduce cost, schedule and time. BIT/BITE/ED/EP/IVHM and ATE complement one another and each play a valuable and vital role in the maintenance and logistics support of the Future Force.

Using general purpose digital hardware to perform boundary scan tests

Abstract: Boundary scan tests are typically developed to make use of the proprietary hardware provided by one of the companies that specialize in boundary scan testing. This can lead to fixturing and logistical problems on large scale test systems used for Defense and Aerospace test, because testing many different assemblies whose tests rely on different boundary scan vendors can require the use of test hardware from each of those vendors. This paper presents a better approach, in which a common runtime software library can be used by each boundary scan supplier to apply his tests using the system's existing general purpose digital hardware.

The Vector Network Analyzer - an essential tool in modern ate measurements

Abstract: The Vector Network Analyzer (VNA) is a modern piece of test gear that was once relegated to specialized measurements in the RF lab. The instrument was large, expensive, and primarily used by the designers of the lower level RF modules. It really didn't offer a reasonable performance advantage that would justify the increased cost to have it added to the standard ATE system. Older VNAs were often delicate and larger than the balance of the RF test gear.

Signal Based Domain Specific Language (SBDSL) a proposal for a next generation test

Abstract: Signal Based Domain Specific Language (SBDSL) is a domain specific language which combines the use of ATLAS Signal statements with high-level programming language constructs. The goals of this new language are: facilitate the writing of concurrent test programs, provide a language that is easy to extend with new constructs, maintain backwards compatibility with ATLAS Family of languages, enable interoperability between test stations, and enable engineers' fresh out of college to quickly become productive with a test programming language. This paper will cover how the design of the SBDSL language, SBDSL Integrated Development Environment (IDE) and runtime executable will accomplish these goals and present results from the technology demonstration developed.

Improving Electrical Ground Support Equipment development for satellite testing

Abstract: This paper examines the basic test method employed with Electrical Ground Support Equipment; evaluates the technical merits associated with enhanced capabilities and compares the relative cost of these enhancements. In addition, the paper explores the pros and cons of replacing current manual operations with integrating automated test methods. This study is not intended to be a precise cost analysis but is intended to provide a comparison of technical enhancements along with a basic measure of cost. This paper will provide some practical examples to support the premise that automated test methods give rise to a more thoroughly tested spacecraft, reduced test times and potential cost savings.

A methodology for enhancing legacy TPS/ATS sustainability via employing Synthetic Instrumentation technology

Abstract: This paper presents a methodology for mitigating Test Program Set (TPS) & Automatic Test System (ATS) obsolescence and enhancing TPS/ATS sustainability via employing Synthetic Instrumentation (SI) technology. The methodology and the associated sub- processes described within this paper represent a major paradigm shift in current support equipment hardware & software sustainability approaches and will have a profound impact on the process of supporting and maintaining legacy automated test systems (ATS) and TPSs now and into the future. The subject methodology was validated employing the Tobyhanna Army Depot (TYAD) RF Test Platform as the demonstration vehicle test bed. The proof-of-concept demonstration validated the concept of emulating and replacing several legacy Commercial Off-the-Shelf (COTS) instruments with synthetic instrument technology. The primary goals of validating this technology paradigm were to provide an environment that would reduce TPS rework costs, decrease ATS maintenance and repair costs, and enhance the sustainability of legacy ATSs/TPSs going forward. During the course of this project the synthetic instrument technology insertion paradigm was demonstrated to the at-large DOD maintenance community.

Analyzing artifacts in the time domain waveform to locate wire faults

Abstract: Wire integrity is a growing concern with aging vehicles, especially high vibration variants like helicopters, tiltrotor aircraft, and many mobile ground weapons systems. Wiring failures on these systems present a growing safety concern and can lead to loss of equipment and life. This paper presents a novel adaptive Time Domain Reflectometry (TDR) algorithm to analyze artifacts found on the reflected time domain waveform of a high-voltage, low-energy pulse transmitted down wires with uncontrolled or controlled impedances. This method allows for detection of intermittent and hard faults. Most Time Domain Reflectometers (TDRs) are used to measure cable lengths and distances to hard opens or shorts. An existing technology, for which this algorithm was developed, extended the measurement capability to intermittent faults. Current detection methods for intermittent faults require an experienced engineer to interpret the returned measurement and waveform to confirm its accuracy. In order to make this technology more accessible the repeatability and accuracy of the automated measurements need to be improved. The following method improves the unadjusted accuracy by 3 times. This paper reviews the theory of TDR and presents implementation and results of the proposed algorithm on real-world data.

The impact of test instrumentation with distributed processing capabilities on test program set (TPS) architecture and development

Abstract: Modern digital interconnection methods have placed significant computational demands on computers controlling test systems, and adding dedicated computing resources for high performance digital test instrumentation to the test system can help meet these demands. This paper examines the impact of these additional computing resources on the design of a TPS, and proposes a software framework to assist developers in creating TPSs for multi-computer environments.

ATE and TPS management

Abstract: The purpose of this paper to discuss Automatic Test Equipment (ATE) and Test Program Set (TPS) management strategy efforts to improve support and reduce logistics costs within the Air Force. The emphasis of this paper will be on two subtopics; efforts to reduce proliferation of unique Automatic Test Systems (ATS) and the impact of technology and software advances as they relate to how the Air Force (AF) works to standardize the TPS process. Both subtopics have a focus on standardization and reduction in life cycle costs for the Air Force.

Capacitive transducer for condition based maintenance after harsh landing events

Abstract: The objective of this work is to identify design parameters for a capacitive sensor designed to recognize and record helicopter harsh landing events. Harsh landing events are typically associated with landing speeds exceeding 2.5 m/s [1] and require mandatory structural inspection resulting in down-times that could last a week or longer. In cases where no visible damage occurs, harsh-landing events might be difficult to identify and record. This paper presents a finite element analysis of the acceleration profile at different locations of the skid of a Bell 206 L4 helicopter which is then used to design and test a low-cost capacitive sensor for monitoring harsh landing events. Time history and histograms of the acceleration signal during normal and harsh landings are presented. The capacitive accelerometer is designed to operate in the 10g to 360g range. The sensor is integrated directly on a wiring board and is readout by a micro-controller with a capacitive ASIC. Details of the sensor design, fabrication, and testing are presented. The presented material also provides hard-to-find design data on the structural accelerations which can occur during harsh landing.

Automated fiber optic cable endface field inspection technology

Abstract: The rapid deployment of fiber optic technology in military, avionic, and consumer platforms is driving the need for improvement in fiber optic cable field maintenance, specifically a reduction in operator inspection complexity and ambiguity. Current inspection technology depends on operator experience with various inspection standards and is further complicated in military field deployments where bench top capable inspection equipment does not lend itself to field installations. Military fiber endface inspection is currently very expertise driven and time consuming for avionic environments. Thus there is a need for automated, portable fiber optic inspection technology that is suitable for all skill levels, and is capable of field deployment and maintenance. This paper explores the issue of current fiber optic field inspection technology and present an automated test inspection set to address these problems.

Common RF test platform

Abstract: A wide range of Radio Frequency (RF) assemblies require testing during their development and production These include amplifiers, mixers, filters, up converters, down converters, antennas, phase shifters, power dividers, power combiners, Integrated Master Assemblies (IMAs), Weapons Replaceable Assemblies (WRAs), Line Replaceable Units (LRUs) and radio subassemblies Though there are many differences between the RF assemblies, they all require a test system that is accurate, reliable and traceable while simultaneously minimizing test times Other important attributes of a test platform for RF assemblies are that it must be calibrated, fully-characterized and incorporate self-test functionality The test platform must also include a digital control solution for triggering, communicating with Units Under Test (UUT) and interfacing with handlers, fixtures, etc Finally, the software for the test equipment must also be considered Typical software functionality would include sequencing, reporting, testing, calibration, and self-test While it is certainly possible to develop a test system specific to each type of RF assembly; there are many benefits to developing a common RF test platform that includes the functionality listed above

Development of a command and telemetry processing interface to be independent of ground control systems

Abstract: The Johns Hopkins University Applied Physics Laboratory (APL) has developed numerous spacecraft for national security and civilian space applications that have used varied flight computers and ground control systems. On missions that have utilized different ground control systems, the command and telemetry (C&T) database development has been unique to the specific mission. On missions that have utilized a common ground control system, APL has leveraged a limited extent of commonality in the development of the C&T databases, which has shown promise in development, schedule, and cost efficiency and has improved the quality of the early C&T database deliveries. On its recent Radiation Belt Storm Probes mission (RBSP), APL developed a set of C&T tools to tackle the challenge of developing a common C&T database across multiple satellites, over full mission life cycles, that minimizes coupling with the core ground control system such that the use across different ground systems is maximized. This paper discusses the specific approach taken in evaluating the C&T database development for APL's past missions and the shortfalls that were encountered. Lessons learned were evaluated and decisions were made in implementing the RBSP C&T databases. The tool development is briefly discussed with an emphasis on the engineering use during satellite subsystem development. Recent successes during the testing are also presented. Finally, plans are described for continued improvement to the approach and tools for subsequent APL spacecraft so that the C&T database can be ported to other missions of interest.

TPS development using the Microsoft .NET Framework

Abstract: Managed or .NET languages are widely used in system software development but are often overlooked for TPS development. This paper looks at using managed languages and the .NET Framework for TPS development. In addition to describing the extensive library support for math, file I/O and string manipulation built into the framework and the powerful application development and debugging support in Visual Studio, the paper also explores how one would define and combine test specific constructs.

Testable and diagnosable commercial off the shelf (COTS) electronics

Abstract: Commercial off the shelf (COTS) are inexpensive electronics modules, partly because the designs are expected to conform to commercial needs and driven by market popularity, rather than military and avionics logistics. Design for testability (DFT) and for diagnosability (DFD) can serve both manufacturing and end user concerns. COTS testability, however, are generally focused only on improving manufacturing test - or the vendors' domain. End users' testability and diagnosability concerns are different. For COTS to serve system level support, designers must plan for maintenance and repair paradigms. We present a set of general and simple to implement guidelines for COTS designers so that system designers can create testable and diagnosable systems using COTS modules. The guidelines will initially serve as selection criteria between competing COTS, but we hope it will eventually become a universal design guideline for all COTS designers.

Anecdotal experiences on the value of limited environmental testing for the analysis of “No Fault Found” assemblies

Abstract: Electronic assemblies that fail on an aircraft often will not fail on a laboratory tester or will exhibit random and hard to pinpoint failures. This is a discussion of environmental testing types, why environmental testing is needed, and a brief review of several such assemblies and test systems and what extra environmental testing was performed to identify issues that were not identifiable under normal testing.

Where did my signal go? A discussion of signal loss between the ATE and UUT

Abstract: Automatic Test Equipment (ATE) is now testing Units Under Test (UUTs) with signals that operate with data rates of several gigabits per second. Therefore, the test engineer must understand and account for the signal degradation through the transmission path. These high-speed digital signals typically pass through a variety of transmission media between the input/output (I/O) buffers on the ATE to the I/O buffers on the UUT. This paper highlights several considerations for the test engineer who is creating the test and system setup for a multi-gigabit per second bus. The paper discusses the contributors to DC and AC signal loss as well as methods to help minimize these losses. The paper focuses on multi-gigabit applications with matched double terminated transmission lines, but also touches on slightly slower busses with other termination schemes.