Genuine Faults Research Articles

Combined software and hardware fault injection vulnerability detection

Fault injection is a well-known method to test the robustness and security vulnerabilities of software. Software-based and hardware-based approaches have been used to detect fault injection vulnerabilities. Software-based approaches typically rely upon simulations that can provide broad and rapid coverage, but may not correlate with genuine hardware vulnerabilities. Hardware-based experiments are indisputable in their results, but rely upon expensive expert knowledge and manual testing yielding ad hoc and extremely limited results. Further, there is very limited connection between software-based simulation results and hardware-based experiments. This work bridges software-based and hardware-based fault injection vulnerability detection by contrasting results of both approaches. This demonstrates that: not all software-based vulnerabilities can be reproduced in hardware; prior conjectures on the fault model for electromagnetic pulse attacks may not be accurate; and that there is a co-relation between software-based and hardware-based approaches. Further, combining both approaches can yield a vastly more accurate and efficient approach to detecting genuine fault injection vulnerabilities.

Structured Protection Measures for Better Use of Nanocrystalline Cores in Air-Cooled Medium-Frequency Transformer for Induction Heating

Medium-frequency segment constitutes the bulk of energy consumed by induction-heating loads where transformer is an integral part for power delivery. Traditional water-cooled transformer is less efficient, bulky, and involves complex manufacturing processes. Its large leakage hinders efficient power transfer to load. Availability of litz wire conductors and low-loss high-flux-density magnetic cores helped popularize energy-efficient air-cooled transformers in several high-power induction heating applications. For optimal design, the energy efficiency of transformer should be high; moreover, costly conductors and cores need to be optimally used. For constant-current variable-power loads, the copper loss is minimized first, which inherently, core loss permitting, minimizes the core area. The cores are forced to operate at large flux density where this article elaborates that nanocrystalline cores are more suitable. Such a configuration needs to be safe and functionally reliable, particularly, when the operating point of transformer has two dynamic variables—voltage and frequency. For reliable operation, this article proposes structured protection measures where, under genuine fault conditions, the controller is switched off , but for magnetic saturation under healthy conditions (e.g., overload), the frequency is momentarily increased to take cores out of saturation. The proposed concept has been validated in a 60-kW controller designed for forging applications.

Automatic Check Digits Recognition for Arabic Using Multi-Scale Features, HMM and SVM Classifiers

We propose in this work two Automatic Arabic (Indian) digits recognition systems using a real-life dataset of 3000 bank checks. The systems extracts features from training-set images of 7390 isolated digits (0-9). These features are multi-scale in which they capture narrow, intermediate, and large-scale qualities of the image. The gradient features correspond to the narrow scale, the structural features correspond to the intermediate scale, and the concavity features correspond to the large-scale. These features are employed by two different statistical classifiers; Hidden Markov Models (HMM) and Support Vector Machines (SVM). The two independent recognition systems utilize the proficient CENPARMI Arabic bank check database for training and testing. In order to select the optimal parameters for feature extraction and for the HMM classifier, the CENPARMI training dataset is divided into training and verification subsets. After adapting the two systems’ parameters, they are tested on unobserved 3035 digit images. The average recognition rates for the HMM and SVM systems are 97.86% and 99.04%, respectively. The presented systems provides state-of-the-art recognition results on the CENPARMI database, as they reported a higher recognition rates when compared to twelve previously published systems, especially for the SVM system. After analyzing the classification errors, the authors conclude that some of these errors are inevitable as they are most probably attributed to errors in labeling the original database, distinct writing styles of certain digits, and genuine faults.

Model-Based Test Oracle Generation for Automated Unit Testing of Agent Systems

Software testing remains the most widely used approach to verification in industry today, consuming between 30-50 percent of the entire development cost. Test input selection for intelligent agents presents a problem due to the very fact that the agents are intended to operate robustly under conditions which developers did not consider and would therefore be unlikely to test. Using methods to automatically generate and execute tests is one way to provide coverage of many conditions without significantly increasing cost. However, one problem using automatic generation and execution of tests is the oracle problem: How can we automatically decide if observed program behavior is correct with respect to its specification? In this paper, we present a model-based oracle generation method for unit testing belief-desire-intention agents. We develop a fault model based on the features of the core units to capture the types of faults that may be encountered and define how to automatically generate a partial, passive oracle from the agent design models. We evaluate both the fault model and the oracle generation by testing 14 agent systems. Over 400 issues were raised, and these were analyzed to ascertain whether they represented genuine faults or were false positives. We found that over 70 percent of issues raised were indicative of problems in either the design or the code. Of the 19 checks performed by our oracle, faults were found by all but 5 of these checks. We also found that 8 out the 11 fault types identified in our fault model exhibited at least one fault. The evaluation indicates that the fault model is a productive conceptualization of the problems to be expected in agent unit testing and that the oracle is able to find a substantial number of such faults with relatively small overhead in terms of false positives.

A Petri Net Approach to Fault Verification in Phased Mission Systems using the Standard Deviation Technique

Health management systems are now standard aspects of complex systems. They monitor the behaviour of components and sub‐systems and in the event of unexpected system behaviour diagnose faults that have occurred. Although this process should reduce system downtime, it is known that health management systems can generate false faults that do not represent the actual state of the system and cause resources to be wasted. The authors propose a process to address this issue in which Petri nets (PNs) are used to model complex systems. Faults reported on the system are simulated in the PN model to predict the resultant system behaviour. This behaviour is then compared to that from the actual system. Using the standard deviation technique, the similarity of the system variables is assessed and the validity of the fault determined. The process has been automated and is tested through application to an experimental rig representing an aircraft fuel system. The success of the process to verify genuine faults and identify false faults in a multi‐phase mission is demonstrated. A technique is also presented that is specific to tank leaks where depending on the location and size of the leak, the resulting symptoms will vary. Copyright © 2012 John Wiley & Sons, Ltd.

Excluding inclusions

The authors look at the causes of a persistent annoyance for manufacturers of printed circuit boards, and suggest some steps that would help to speed inspection and reduce both genuine faults and false rejects from the visual inspection system. This article goes into one detail of the problem: the inclusions in laminates that can cause false rejection in PCB manufacture. Laminate inclusions are now becoming prevalent because of the higher resolution needed to inspect reduced track and gap widths. Tests on rejected PCBs show that contamination inside laminates accounts for a large percentage of rejects. There are four main types of inclusions: tadpoles, burnt resin, metal and others. The most efficient way of spotting them is using visual methods.

Regulations and safety in medical equipment design

Regulations and safety in medical equipment design

Automatic surface crack detection on textured materials

A novel image transformation is proposed for the automatic detection of crack-like faults on inspected surfaces with “busy” or patterned backgrounds (textured surfaces). The textured background is modeled by the proposed transformation, which consists of the Walsh transformation of a nonlinear function of the image intensity. The algorithm includes three stages: training the system to learn the underlying background textural pattern by using faultless images, obtaining the local difference from the underlying texture for the images to be tested, and postprocessing the difference map to isolate the fault pixels. By this method, crack-like faults in random and regularly textured backgrounds can be detected reliably and efficiently. The performance of the algorithm is demonstrated on artificially created faults on some Brodatz texture images as well as on some real images of materials with genuine faults on them.

New method of power swing blocking for digital distance protection

A new method for preventing digital distance relay operation during power swings is presented based on detection of transients in the measured reactance. The transients are detected by the difference between two reactances calculated using two parallel FIR filters based on coefficients used in the discrete Hartley transform. The transients are present under genuine fault conditions but not during power swings. Fault transient detection therefore enables the relay for faults but leaves it inherently blocked for power swings. Simulation results are presented showing that the fault transient detection method does not lead to increased relay operating time, but allows the relay to differentiate between faults and power swings. The significant advantage of this new method of blocking is that the relay can correctly operate if a genuine fault occurs during the power swing period.

New one cycle, microprocessor based differential relay for transformer protection

This paper presents a fully selective new one cycle microprocessor based differential relay for transformer protection. The relay was tested and was found to take care of maloperation due to inrush, current transformer (CT) saturation with internal fault, unsaturated CT with external fault, saturation of one CT with external (heavy through fault) or internal fault etc., without sacrificing the performance of the differential relay under genuine fault conditions. The relay behaviour has been extensively tested by arranged circuits for differential protection of tranformers in the laboratory for all above conditions.