Patrick W. Kalgren

Turn-Off Time as an Early Indicator of Insulated Gate Bipolar Transistor Latch-up

In this paper, effects preceding a latch-up fault in insulated gate bipolar transistors (IGBTs) are studied. Primary failure modes associated with IGBT latch-up faults are reviewed. Precursors to latch-up, primarily an increase in turn-off time as a consequence of elevated junction temperature, are examined for an IGBT. The relationship between junction temperature and turn-off time is explained by modeling the parasitic properties of an IGBT. A metric is derived from the model to standardize the relative estimates in junction temperature from measurements of turn-off time. To evaluate the effects preceding latch-up in-situ, seeded fault testing is conducted on a three-phase power inverter using aged transistors induced with a fault located in the die-attach solder layer. Experimental results demonstrated the feasibility of using the proposed metric as a precursor to transistor latch-up.

Application of Prognostic Health Management in Digital Electronic Systems

Development of robust prognostics for digital electronic system health management will improve device reliability and maintainability for many industries with products ranging from enterprise network servers to military aircraft. Techniques from a variety of disciplines is required to develop an effective, robust, and technically sound health management system for digital electronics. The presented technical approach integrates collaborative diagnostic and prognostic techniques from engineering disciplines including statistical reliability, damage accumulation modeling, physics of failure modeling, signal processing and feature extraction, and automated reasoning algorithms. These advanced prognostic/diagnostic algorithms utilize intelligent data fusion architectures to optimally combine sensor data with probabilistic component models to achieve the best decisions on the overall health of digital components and systems. A comprehensive component prognostic capability can be achieved by utilizing a combination of health monitoring data and model-based estimates used when no diagnostic indicators are present. Both board and component level minimally-invasive and purely internal data acquisition methods will be paired with model-based assessments to demonstrate this approach to digital component health state awareness.

Electronic prognostics ¿ A case study using global positioning system (GPS).

Prognostic health management (PHM) of electronic systems presents challenges traditionally viewed as either insurmountable or otherwise not worth the cost of pursuit. Recent changes in weapons platform acquisition and support requirements has spurred renewed interest in electronics PHM, revealing possible applications, accessible data sources, and previously unexplored predictive techniques. The approach, development, and validation of electronic prognostics for a radiofrequency (RF) system are discussed in this paper. Conventional PHM concepts are refined to develop a three-tier failure mode and effects analysis (FMEA). The proposed method identifies prognostic features by performing device, circuit, and system-level modeling. Accelerated failure testing validates the identified diagnostic features. The results of the accelerated failure tests accurately predict the remaining useful life of a COTS GPS receiver to within plusmn5 thermal cycles. The solution has applicability to a broad class of mixed digital/analog circuitry, including radar and software defined radio

Modeling aging effects of IGBTs in power drives by ringing characterization

This paper presents two types of aging modeling for IGBTs. The physical modeling allows a better understanding of the physical mechanics of failures while the functional model represents a more general approach that can be easily extended to model more complex systems. The latter also allows a better characterization of the ringing signal phenomenon, which was found to be characteristic of aged IGBTs. Based on the effects of aging on the ringing, a feature is proposed to capture these changes in real-time and use them as a diagnostic tool for components health state. A real power drive platform is implemented to experimentally verify the ringing characterization modeled and to demonstrate the repeatability of the ringing effects observed at high frequencies in the voltage and current of electrical components.

Online Ringing Characterization as a Diagnostic Technique for IGBTs in Power Drives

Embeddable features that are easily incorporated in traditional power drive systems are identified for prognostics and health management (PHM) systems. The proposed novel feature takes advantage of the original pulsewidth modulation (PWM) waveform produced by the inverter that is already available in the system as a succession of step functions to study the systems response at high frequencies. The high-order oscillatory responses (ringing) present in the voltages and currents of the system are a reflection of the interaction among the internal parametric components of the power devices, allowing device characterization. Evaluating the change over time of these parameters characterized from ringing becomes a key novel feature to assess the aging status of the power electronic circuit and electric machine with respect to transistor degradation. We propose the use of a low-cost bandpass analog filter centered at a high frequency, which is relevant as a feature input capable of aging tracking. The simplified model supporting ringing as a feature to evaluate component aging and its experimental evaluation are presented with experimental data, corroborating its viability as a practical real-time power device health-state indicator.

Embedded diagnostic/prognostic reasoning and information continuity for improved avionics maintenance

The authors are developing enhanced onboard and at-wing diagnostic technologies applicable to both legacy and new avionics. The paper identifies onboard information sources and automated reasoning techniques that build upon existing built-in-test (BIT) results to improve fault isolation accuracy. Modular software and data elements that combine BIT with contextual information, component usage models, and novel reasoning techniques are described. In addition, the authors identify candidate avionics component applications to implement prognostics (prediction of impending problem) using forecasting techniques. A demonstration of diagnostic/prognostic prototype reasoners and information continuity using an open architecture framework within the streamlined maintenance concept is offered.

Advanced diagnostic/prognostic reasoning and evidence transformation techniques for improved avionics maintenance

Techniques used in the design and implementation of modern avionics suggest an opportunity to re-examine the maintenance and repair process for current and future systems. The authors have developed a framework with automated evidence collection, data representation and storage, and, advanced automated reasoning techniques to implement within an avionics health management system. This paradigm shift approach utilizes advanced capture and representation of environmental, operational, and component inter-relationship evidence at a systems level to reduce diagnostic ambiguity, guide at-wing testing, and provide prognostics. Modular and reusable software and data elements that combine built-in-test (BIT) with contextual information, component usage models, and evidentiary reasoning techniques are described. A use case scenario is presented that illustrates evidence collection and XML transformation, automated database storage and retrieval, and automated advanced reasoning for diagnostics and prognostics, and finally, an example of at wing ambiguity reduction using an advanced evidence-based reasoner is presented.

Electronic prognostics - a case study using Global Positioning System (GPS)

Prognostic health management (PHM) of electronic systems presents challenges traditionally viewed as either insurmountable or otherwise not worth the cost of pursuit. Recent changes in weapons platform acquisition and support requirements has spurred renewed interest in electronics PHM, revealing possible applications, accessible data sources, and previously unexplored predictive techniques. The approach, development, and validation of electronic prognostics for a radiofrequency (RF) system are discussed in this paper. Conventional PHM concepts are refined to develop a three-tier failure mode and effects analysis (FMEA). The proposed method identifies prognostic features by performing device, circuit, and system-level modeling. Accelerated failure testing validates the identified diagnostic features. The results of the accelerated failure tests accurately predict the remaining useful life of a COTS GPS receiver to within plusmn5 thermal cycles. The solution has applicability to a broad class of mixed digital/analog circuitry, including radar and software defined radio

Prognostic health management for avionic systems

Maintenance of aircraft electronic systems has traditionally been performed in reaction to reported failures or through periodic system replacements. Recent changes in weapons platform acquisition and support requirements have spurred interest in application of prognostic health management (PHM) concepts developed for mechanical systems to electronic systems. The approach, development, and validation of prognostics for two types of electronic equipment are discussed in this paper. The two applications, a switch-mode power supply and a GPS receiver were selected based on their relatively high failure rates and relevance to many commonly used avionics systems. The method identifies prognostic features by performing device, circuit, and system-level modeling. Device modeling with equivalent circuit and mathematical physics of failure models describe parameter degradation resulting from damage accumulation for each device. Prognostic features extracted from a small array of sensors on the power supply, and from the GPS operational communication data stream are used to update life usage and failure progression models to provide an indication of the health state. The results of accelerated failure tests on both systems are used to illustrate the approach and demonstrate its effectiveness in predicting the useful life remaining. The solutions have applicability to power supplies in many avionic systems, and to a broad class of mixed digital/analog circuitry including radar and software defined radio

On-line ringing characterization as a PHM technique for power drives and electrical machinery

Embeddable features easily incorporated in traditional power drive systems are identified for prognostic health management (PHM) systems. This novel technique utilizes the original PWM waveform produced by the inverter to evaluate the power electronic circuit and electric machine against transistor degradation. Evaluation of the primary feature, ringing characterization, with experimental data demonstrates its viability as a practical real-time power device health-state indicator.