Showing papers on "Fault detection and isolation published in 1993"

Detection of abrupt changes: theory and application

Abstract: This book is downloadable from http://www.irisa.fr/sisthem/kniga/. Many monitoring problems can be stated as the problem of detecting a change in the parameters of a static or dynamic stochastic system. The main goal of this book is to describe a unified framework for the design and the performance analysis of the algorithms for solving these change detection problems. Also the book contains the key mathematical background necessary for this purpose. Finally links with the analytical redundancy approach to fault detection in linear systems are established. We call abrupt change any change in the parameters of the system that occurs either instantaneously or at least very fast with respect to the sampling period of the measurements. Abrupt changes by no means refer to changes with large magnitude; on the contrary, in most applications the main problem is to detect small changes. Moreover, in some applications, the early warning of small - and not necessarily fast - changes is of crucial interest in order to avoid the economic or even catastrophic consequences that can result from an accumulation of such small changes. For example, small faults arising in the sensors of a navigation system can result, through the underlying integration, in serious errors in the estimated position of the plane. Another example is the early warning of small deviations from the normal operating conditions of an industrial process. The early detection of slight changes in the state of the process allows to plan in a more adequate manner the periods during which the process should be inspected and possibly repaired, and thus to reduce the exploitation costs.

Efficient software-based fault isolation

Abstract: One way to provide fault isolation among cooperating software modules is to place each in its own address space. However, for tightly-coupled modules, this solution incurs prohibitive context switch overhead. In this paper, we present a software approach to implementing fault isolation within a single address space.Our approach has two parts. First, we load the code and data for a distrusted module into its own fault do main, a logically separate portion of the application's address space. Second, we modify the object code of a distrusted module to prevent it from writing or jumping to an address outside its fault domain. Both these software operations are portable and programming language independent.Our approach poses a tradeoff relative to hardware fault isolation: substantially faster communication between fault domains, at a cost of slightly increased execution time for distrusted modules. We demonstrate that for frequently communicating modules, implementing fault isolation in software rather than hardware can substantially improve end-to-end application performance.

FINE: A fault injection and monitoring environment for tracing the UNIX system behavior under faults

Abstract: The authors present a fault injection and monitoring environment (FINE) as a tool to study fault propagation in the UNIX kernel. FINE injects hardware-induced software errors and software faults into the UNIX kernel and traces the execution flow and key variables of the kernel. FINE consists of a fault injector, a software monitor, a workload generator, a controller, and several analysis utilities. Experiments on SunOS 4.1.2 are conducted by applying FINE to investigate fault propagation and to evaluate the impact of various types of faults. Fault propagation models are built for both hardware and software faults. Transient Markov reward analysis is performed to evaluate the loss of performance due to an injected fault. Experimental results show that memory and software faults usually have a very long latency, while bus and CPU faults tend to crash the system immediately. About half of the detected errors are data faults, which are detected when the system is tries to access an unauthorized memory location. Only about 8% of faults propagate to other UNIX subsystems. Markov reward analysis shows that the performance loss incurred by bus faults and CPU faults is much higher than that incurred by software and memory faults. Among software faults, the impact of pointer faults is higher than that of nonpointer faults. >

Developing interpretable models with optimized set reduction for identifying high-risk software components

Abstract: Applying equal testing and verification effort to all parts of a software system is not very efficient, especially when resources are tight. Therefore, one needs to low/high fault frequency components so that testing/verification effort can be concentrated where needed. Such a strategy is expected to detect more faults and thus improve the resulting reliability of the overall system. The authors present the optimized set reduction approach for constructing such models, which is intended to fulfill specific software engineering needs. The approach to classification is to measure the software system and build multivariate stochastic models for predicting high-risk system components. Experimental results obtained by classifying Ada components into two classes (is, or is not likely to generate faults during system and acceptance rest) are presented. The accuracy of the model and the insights it provides into the error-making process are evaluated. >

Local area network with fault detection and recovery

Abstract: A local area network having fault detection and recovery and a method for detecting and recovering from faults in a local area network are disclosed. The network has modules interconnected by a token bus implemented by a pair of redundant cable systems. All of the modules are agent modules and one of the modules also serves as a master module. Each agent module periodically transmits an agent heartbeat signal on each of its cables. Each module monitors all of the agent heartbeat signals from all of the other modules. When a fault is detected by a module, such as missed agent heartbeat signals from another module, the module applies agent rules to determine if and how the fault should be reported. The agent module reports the fault to the master module. The master module collects fault reports from the agent modules, applies a set of master rules to the agent fault reports, and generates a master failure report. The master module also initiates an appropriate network recovery action based upon the failure report generated. The master module periodically transmits a master heartbeat signal on the token bus which is received by the agent modules. The agent modules decode the master heartbeat signal to ensure that a master module is always present on the token bus.

Implantable medication infusion pump including self-contained acoustic fault detection apparatus

Abstract: Apparatus located in an implantable medication infusion pump for quickly and easily detecting a condition adversely affecting medication delivery in the implantable medication infusion pump is disclosed which can reliably detect occurrences including an occluded catheter, the presence of air in the pumping mechanism, and the failure of the pumping mechanism. The system uses the amplitude of an acoustic signal generated by operation of the pumping mechanism as compared with a baseline signal to detect an encapsulated or occluded catheter or air in the fluid line. In addition, the system can detect a partially encapsulated or occluded catheter by detecting repeated downward slope patterns during repetitive, closely spaced pumping cycles.

On the application and design of artificial neural networks for motor fault detection. II

Abstract: The general design considerations for feedforward artificial neural networks (ANNs) to perform motor fault detection are presented. A few noninvasive fault detection techniques are discussed, including the parameter estimation approach, human expert approach, and ANN approach. A brief overview of feedforward nets and the backpropagation training algorithm, along with its pseudocodes, is given. Some of the neural network design considerations such as network performance, network implementation, size of training data set, assignment of training parameter values, and stopping criteria are discussed. A fuzzy logic approach to configuring the network structure is presented. >

Robust fault detection in nonlinear systems using sliding mode observers

Abstract: A model-based scheme for robust detection and isolation of faults in a twin continuously-stirred tank reactor is presented. The scheme uses sliding mode observers for robust fault detection in the presence of parameter uncertainties in the system model. The fault detection and isolation scheme is validated by simulated faults in the sensors, actuators and plant operating parameters. The fault detection and isolation technique based on sliding mode observers is shown to be robust to parameter uncertainty in the model. The technique also provides a method for estimating the parameter error in the system. >

Faults and unbalance forces in the switched reluctance machine

Abstract: The paper identifies and analyzes a number of severe fault conditions that can occur in the switched reluctance machine, from the electrical and mechanical points of view. It is shown how the currents, torques, and forces may be estimated, and examples are included showing the possibility of large lateral forces on the rotor. The methods used for analysis include finite-element analysis, magnetic circuit models, and experiments on a small machine specially modified for the measurement of forces and magnetization characteristics when the rotor is off-center. Also described is a computer program (PC-SRD dynamic) which is used for simulating operation under fault conditions as well as normal conditions. The paper discusses various electrical configurations of windings and controller circuits, along with methods of fault detection and protective relaying. The paper attempts to cover several analytical and experimental aspects as well as methods of detection and protection. >

Fault detection in an Ethernet network using anomaly signature matching

Abstract: In an Ethernet network, a common type of failure is the temporary of extended loss of bandwidth, or soft failure as it is referred to in the literature. Though the causes of soft failures vary, to the network user such failures are perceived as noticeably degraded or anomalous performance.This work uses anomaly detection as a means to signal performance degradations that are indicative of network soft failures. Detection is done via a signature matching mechanism, call a fault feature vector, which will detect the occurrence of a fault by looking for anomaly conditions particular to the fault. In a two-year study of the Carnegie Mellon University Computer Science Network the fault feature vector mechanism proved effective in detecting faults and discriminating between faults types. This mechanism was also effective at abstracting large amounts of network data to only those events which warranted operator attention; in this two-year study, over 32 million monitored data points were reduced to under a two hundred event matchings.

A practical approach to accurate fault location on extra high voltage teed feeders

Abstract: The basis of an alternative approach for accurately locating faults on teed feeders is described. The technique developed uses fault voltages and currents at all three ends. The method is virtually independent of fault resistance and largely insensitive to variations in source impedance, teed and line configurations, including line untransposition. The basic theory of the technique is presented. It is extensively tested using simulated primary system voltage and current waveforms, which include the transducer/hardware errors encountered in practice. The performance clearly shows a high degree of accuracy. >

Transition fault testing for sequential circuits

Abstract: Addresses the problem of simulating and generating tests for transition faults in nonscan and partial scan synchronous sequential circuits. A transition fault model for sequential circuits is first proposed. In this fault model, a transition fault is characterized by the fault site, the fault type, and the fault size. The fault type is either slow-to-rise or slow-to-fall. The fault size is specified in units of clock cycles. Fault simulation and test generation algorithms for this fault model are presented. The fault simulation algorithm is a modification of PROOFS, a parallel, differential fault simulation algorithm for stuck faults. Experimental results show that neither a comprehensive functional verification sequence nor a test sequence generated by a sequential circuit test generator for stuck faults produces a high fault coverage for transition faults. Deterministic test generation for transition faults is required to raise the coverage to a reasonable level. With the use of a novel fault injection technique, tests for transition faults can be generated by using a stuck fault test generation algorithm with some modifications. Experimental results for ISCAS-89 benchmark circuits and some AT&T designs are presented. Modifications to test generation and fault simulation algorithms required for partial scan circuits are presented. Experimental results on large benchmark circuits show that a high transition fault coverage can be achieved for the partial scan circuits designed using the cycle breaking technique. >

Solid-state current limiter for power distribution system

Abstract: To prevent voltage decrease of distribution systems, the principle and fundamental characteristics of a solid-state current limiter using GTO thyristors were investigated. Basic components of the apparatus were a fast solid-state switch and a current limiting impedance of low resistance in parallel with the switch. Experimental results of the test current limiter showed the fault current was limited successfully, regardless of DC component size. The time from detection of fault occurrence to interruption of the fault current by the solid-state switch was 40 mu s. This time was very short in comparison with that before the fault current reached a large value. Thermal rise of the solid-state switch for conduction was solved by a self-cooling apparatus using a noncombustible cooling liquid. The results indicated that the solid-state current limiter was a valuable protecting device for high fault current distribution systems. >

An efficient algorithm for sequential circuit test generation

Abstract: This paper presents an efficient sequential circuit automatic test generation algorithm. The algorithm is based on PODEM and uses a nine-valued logic model. Among the novel features of the algorithm are use of Initial Timeframe Algorithm and correct implementation of a solution to the Previous State Information Problem. The Initial Timeframe Algorithm, one of the most important aspects of the test generator, determines the number of timeframes required to excite the fault for which a test is to be derived and the number of timeframes required to observe the excited fault. Correct determination of the number of timeframes in which the fault should be excited (activated) and observed saves the test generator from performing unnecessary search in the input space. Test generation is unidirectional, i.e., it is done strictly in forward time, and flip-flops in the initial timeframe are never assigned a state that needs to be justified later. The algorithm saves both the good and the faulty machine states after finding a test to aid in subsequent test generation. The Previous State Information Problem, which has often been ignored by existing test generators, is presented and discussed in the paper. Experimental results are presented to demonstrate the effectiveness of the algorithm. >

More experience with data flow testing

Abstract: Experience is provided about the cost and effectiveness of the Rapps-Weyuker data flow testing criteria. This experience is based on studies using a suite of well-known numerical programs, and supplements an earlier study (Weyuker 1990) using different types of programs. The conclusions drawn in the earlier study involving cost are confirmed in this study. New observations about tester variability and cost assessment, as well as fault detection, are also provided. >

An expert system for transmission substation event analysis

Abstract: Digital fault recorders (DFRs) are used in substations to capture recordings of various disturbances and fault events. Protection engineers use these recordings to identify reasons for particular operation of protection relays and circuit breakers. In performing this task protection engineers use their expertise related to specific power system conditions, equipment and operations. This paper describes implementation of an expert system which performs fault detection and diagnosis automatically and can aid operators in their task of analyzing disturbances and fault events. >

Concurrent error detection and fault-tolerance in linear analog circuits using continuous checksums

Abstract: The problem of concurrent error detection and fault tolerance is studied. These checksums of time-varying functions are possible because the function of a linear analog circuit can be represented mathematically by a set of matrices to which checksum codes can be applied. For the purpose of error detection, it is assumed that a fault can cause the value of a passive circuit component to deviate from its normal value, result in a line short or open, or change the operating characteristics of the active components (operational amplifiers). If the specifying parameters of a linear analog circuit change due to a fault and the failed circuit behaves as a linear system, then error correction is performed by compensating for the changed parameter values. Otherwise, partical correction is possible. Error detection and correction are performed by a small amount of hardware added to the linear analog circuit. The hardware overhead is virtually constant irrespective of the circuit size, and the sensitivity of the error detection circuit to failures can be easily calibrated. >

An analysis of test data selection criteria using the RELAY model of fault detection

Abstract: RELAY is a model of faults and failures that defines failure conditions, which describe test data for which execution will guarantee that a fault originates erroneous behavior that also transfers through computations and information flow until a failure is revealed. This model of fault detection provides a framework within which other testing criteria's capabilities can be evaluated. Three test data selection criteria that detect faults in six fault classes are analyzed. This analysis shows that none of these criteria is capable of guaranteeing detection for these fault classes and points out two major weaknesses of these criteria. The first weakness is that the criteria do not consider the potential unsatisfiability of their rules. Each criterion includes rules that are sufficient to cause potential failures for some fault classes, yet when such rules are unsatisfiable, many faults may remain undetected. Their second weakness is failure to integrate their proposed rules. >

The application of satellite time references to HVDC fault location

Abstract: An HVDC fault location scheme is described. It relies on very precise detection of the time of arrival of fault-created surges at both ends of the line. Such detection is achieved by a very accurate data acquisition and processing system combined with the time reference signals provided by a Global Positioning System receiver. Extensive digital simulation is carried out to determine the voltage and current waveforms, to identify the main sources of error, and to suggest possible compensation techniques. >

Comparison and analysis of centralized, decentralized, and federated filters

Abstract: This paper investigates the implementation of three variations of the Kalman filter-centralized, decentralized, and federated. The underlying theory for these designs is first overviewed, and the designs are then compared on the basis of accuracy, computational efficiency, and fault-tolerance performance. Special attention is paid to the federated filter design and its potential use for fault detection and system recovery. Two numerical examples are included to illustrate the three different filters. The first is the simulated navigation of an object traveling in a straight-line trajectory that is being positioned by two sensors, while the second is a GPS positioning problem using pseudorange and carrier phase observations. Blunders are purposely planted in these two data sets. The numerical results presented support the hypothesis that better fault-tolerance performance can be achieved with a federated-decentralized filter than with a centralized filter approach.

Computational complexity issues in operative diagnosis of graph-based systems

Abstract: Systems that can be modeled as graphs, such that nodes represent the components and the edges represent the fault propagation between the components, are considered. Some components are equipped with alarms that ring in response to faulty conditions. In these systems, two types of problem are studies: fault diagnosis and alarm placement. The fault diagnosis problems deal with computing the set of all potential failure sources that correspond to a set of ringing alarms. Single faults, where exactly one component can become faulty at any time, are primarily considered. Systems are classified into zero-time and non-zero-time systems on the basis of fault propagation time. The latter are further classified on the basis of knowledge of propagation times. For each of these classes algorithms are presented for single fault diagnosis. The problem of detecting multiple faults is shown to be NP-complete. An alarm placement problem that requires a single fault to be uniquely diagnosed is examined. >

Analog circuit testing based on sensitivity computation and new circuit modeling

Abstract: Analog circuit testing is considered to be a very difficult task, due mainly to the lack of fault models and accessibility to internal nodes. An approach is presented for analog circuit modeling and testing to overcome this problem. This circuit modeling is based on a sensitivity computation and on circuit structure, which are crucial in analog circuit testing. The testability of the circuit is achieved for the simple fault model and by functional testing. Component deviations are deduced by measuring a number of output parameters, and through sensitivity analysis and tolerance computation. Using this approach, adequate tests are identified for testing both catastrophic and soft faults. Some experimental results are presented. >

Randomness fault detection system

Abstract: A method and apparatus are provided for detecting a fault on a power line carrying a line parameter such as a load current. The apparatus monitors and analyzes the load current to obtain an energy value. The energy value is compared to a threshold value stored in a buffer. If the energy value is greater than the threshold value a counter is incremented. If the energy value is greater than a high value threshold or less than a low value threshold then a second counter is incremented. If the difference between two subsequent energy values is greater than a constant then a third counter is incremented. A fault signal is issued if the counter is greater than a counter limit value and either the second counter is greater than a second limit value or the third counter is greater than a third limit value.