Subsystem Failure Research Articles

How combined performance and propagation of failure dependencies affect the reliability of a MSS

Reliability assessment of systems with multiple components is often analyzed on the assumption of component independency. This assumption can be overcome by considering component interactions and is useful for assessing the reliability of technical systems. This paper presents a reliability assessment analysis of multi-state systems (MSS) considering the combination of two types of dependencies: performance and propagation of failure. Performance dependency occurs in sub-systems sharing performance distribution, whereas propagation of failures dependence consists of failures originating in one sub-system causing failures in other sub-systems. The proposed method is based on the extended universal generating approach used for the analysis of MSS with dependencies. This method was applied to wind turbine multi-state system. The results show how sub-system interactions influence the reliability.

Extending Emergency Repair Response Times for Railway Track Switches through Multi-Channel Redundancy of Functional Subsystems

A novel track switch concept has been developed at Loughborough University, which allows parallel-channel, fault-tolerant functions for the first time. This paper demonstrates, through mathematical modelling, real-world data and conservative assumptions, that using a multi-channel, fault-tolerant switching concept can allow an increase in switch availability over baseline scenarios. Performance of four existing switch types is analysed for baseline performance using field data. Multi-channel architectures are then analysed across a range of reactionary maintenance regimes. Availability measures are obtained which show the range of possible switch availability against maintenance response times. The most significant improvements occur when maintenance practice is also revised, the novel system offering the option to run to subsystem failure and remain functional. Results indicate that for multi-channel installations, gains in system availability are possible even when emergency response times are set orders of magnitude longer than currently achieved, indicating a signifi cant reduction in ongoing maintenance commitment. The work also demonstrates that the particular choice of subsystem architecture is of low significance.

Investigation on the multifactor reliability allocation method for CNC lathes based on modified criticality and objective information

A multifactor reliability allocation method for CNC lathes is proposed in this paper based on the failure mode effects and criticality analysis (FMECA) modified criticality factor and objective information. Firstly, taking into consideration the cost of reducing subsystems’ failure rates, criticality in FMECA analysis is introduced into reliability allocation. By making severity value nonlinear and based on subsystems’ failure rate, mathematical model of the cost of reducing subsystems’ failure rates is established, and then computational formula for modified criticality is obtained. Secondly, according to the objective information in existence, failure frequency ratio, failure stopping time ratio, reliability influence degree and structure complexity are calculated respectively. The four sets of values above and modified criticality are combined together as allocation factors. Ratio matrix of each allocation factor is computed to get comprehensive allocation matrix and allocation vector. Finally, the method is applied to a case of reliability allocation of a certain type of CNC lathes, and practicability of the method is analyzed. According to the allocation results, reliability design can be improved to increase the mean time between failure (MTBF) of subsystems and the overall lathe. The proposed method together with the example serves appropriately to show the feedback effect of failure information on reliability design and role of cost reduction in the allocation process.

A prognostic function for complex systems to support production and maintenance co-operative planning based on an extension of object oriented Bayesian networks

The high costs of complex systems lead companies to improve their efficiency. This improvement can particularly be achieved by reducing their downtimes because of failures or for maintenance purposes. This reduction is the main goal of Condition-Based Maintenance and of Prognostics and Health Management. Both those maintenance policies need to install appropriate sensors and data processes not only to assess the current health of their critical components but also their future health. These future health assessments, also called prognostics, produce the Remaining Useful Life of the components associated to imprecision quantifications. In the case of complex systems where components are numerous, the matter is to assess the health of whole systems from the prognostics of their components (the local prognostics). In this paper, we propose a generic function that assesses the future availability of complex systems from their local prognostics (the prognostics of their components) by using inferences rules. The results of this function can then be used as decision support indicators for planning productive and maintenance tasks. This function exploits a proposed extension for Object Oriented Bayesian Networks (OOBN) used to model the complex system in order to assess the probabilities of failure of components, functions and subsystems. The modeling of the complex system is required and it is presented as well as modeling transformations to tackle some OOBN limitations. Then, the computing inference rules used to define the future availability of complex systems are presented. The extension added to OOBN consists in indicating the components that should first be maintained to improve the availabilities of the functions and subsystems in order to provide a second kind of decision support indicators for maintenance. A fictitious multi-component system bringing together most of the structures encountered in complex systems is modeled and the results obtained from the application of the proposed generic function are presented as well as ways that production and maintenance planning can used the computed indicators. Then we show how the proposed generic prognostic function can be used to predict propagations of failures and their effects on the functioning of functions and subsystems.

Immunity-based accommodation of aircraft subsystem failures

PurposeThis paper aims to describe the design, development and flight-simulation testing of an artificial immune-system-based approach for accommodation of different aircraft sub-system failures/damages.Design/methodology/approachThe approach is based on building an artificial memory, which represents self- (nominal conditions) and non-self (abnormal conditions) within the artificial immune system paradigm. Self- and non-self are structured as a set of memory cells consisting of measurement strings, over pre-defined time windows. Each string is a set of features values at each sample time of the flight. The accommodation algorithm is based on the cell in the memory that is the most similar to the in-coming measurement. Once the best match is found, control commands corresponding to this match are extracted from the memory and used for control purposes.FindingsThe results demonstrate the possibility of extracting pilot compensatory commands from the self/non-self structure and capability of the artificial-immune-system-based scheme to accommodate an actuator malfunction, maintain control and complete the task.Research limitations/implicationsThis paper concentrates on investigation of the possibility of extracting compensatory pilot commands. This is a preliminary step toward a more comprehensive solution to the aircraft abnormal condition accommodation problem.Practical implicationsThe results demonstrate the effectiveness of the proposed approach using a motion-based flight simulator for actuator and sensor failures.Originality/valueThis research effort is focused on investigating the use of the artificial immune system paradigm for control purposes based on a novel methodology.

Аналитическая реконфигурация системы управления полетом воздушного судна с сохранением заданных характеристик устойчивости

The paper sets out the conceptual issues of methods of analytical solution of the problem of defined aircraft stability characteristics conservation during flight control system reconfiguration under actuating subsystem failure. It is shown that the use of the reconfiguration technique with analytic set of stabilizing control laws synthesized by the decomposition method taking into account the cross-linking between the control channels allows to fully compensate the effects of failures of the actuating subsystem in each of the control channels under the conditions of complete controllability of aircraft as a dynamic system. It thus makes it possible to reconfigure the flight control system that always ensures the stability of the motion of the aircraft with a precisely prescribed poles. During study of failures in the form of a gradual reduction of the effectiveness of control surfaces it found that the synthesized analytical control law is a corresponding automatic increase feedback gain serviceable channel actuating subsystem, as well as the reallocation of control signals between the drives within the existing cross-connections between the control channels. Some of the solutions obtained by reconfiguring the control laws are not satisfactory, because of significantly limited possibility of maneuvering. The explanation for this is the relatively small quantities of system controllability measures, which are a functions of controllability gramian, and directly related to the severity of failures actuating subsystem. The results can be used at perspective control systems design stage to optimize the characteristics of the control actuators to meet the increasing requirements for fail-safe flight.

The Analytic Solutions to the Task of Maintaining the Specified Characteristics Stability in Aircraft Flight Control System Reconfiguration

The paper sets out the conceptual issues of methods of analytical solution of the problem of defined aircraft stability characteristics conservation during flight control system reconfiguration under actuating subsystem failure. It is shown that the use of the reconfiguration technique with analytic set of stabilizing control laws synthesized by the decomposition method taking into account the cross-linking between the control channels allows to fully compensate the effects of failures of the actuating subsystem in each of the control channels under the conditions of complete controllability of aircraft as a dynamic system. It thus makes it possible to reconfigure the flight control system that always ensures the stability of the motion of the aircraft with a precisely prescribed poles. During study of failures in the form of a gradual reduction of the effectiveness of control surfaces it found that the synthesized analytical control law is a corresponding automatic increase feedback gain serviceable channel actuating subsystem, as well as the reallocation of control signals between the drives within the existing cross-connections between the control channels. Some of the solutions obtained by reconfiguring the control laws are not satisfactory, because of significantly limited possibility of maneuvering.

Analysis and assessment of water distribution subsystem failure

Abstract The aim of the study is to analyse and assess the water supply network failure frequency in last ten years, with particular emphasis on the last year of the analysis. The analysis is based on actual data obtained from the water company. The study contains the analysis of the network failure with division into used material, the type of network and place of failure occurrence. Also the failure rate was calculated. Continuous changes in the age and material structure of the water network cause the need for conducting failure frequency research because data on failure rate are the key indicators for operational policy of water supply systems.

Fault detection and classification in automated assembly machines using machine vision

Automated assembly machines operate continuously to achieve high production rates. Continuous operation increases the potential for faults such as jams, missing parts, and electromechanical failures of subsystems. The goal of this research project was to develop and validate a machine vision inspection (MVI) system to detect and classify multiple faults using a single camera as a sensor. An industrial automated O-ring assembly machine that places O-rings on to continuously moving plastic carriers at a rate of over 100 assemblies per minute was modified to serve as the test apparatus. An industrial camera with LED panel lights for illumination was used to acquire videos of the machine’s operation. A programmable logic controller (PLC) with a human-machine interface (HMI) allowed for the generation of faults in a controlled fashion. Three MVI methods, based on computer vision techniques available in the literature, were developed for this application. The methods used features extracted from the videos to classify the machine’s condition. The first method was based on Gaussian mixture models (GMMs); the second method used an optical flow approach; and the third method was based on running average and morphological image processing operations. In order to provide a single metric to quantify relative performance, a machine vision performance index (MVPI) was developed with five measures of performance: accuracy, processing time, speed of response, robustness against noise, and ease of tuning. The MVPI for the three MVI methods is reported along with the significance of the results.

Effect of critical sub-system failures on the post-earthquake functionality of buildings: A case study for Montréal hospitals

When an earthquake occurs, hospitals are expected to remain functional as they play a crucial role in emergency care operations. This ability to ensure the continuity of quality operations while ensuring the safety of occupants during and after an earthquake defines the concept of post-earthquake functionality. Hospital functionality relies on the good performance of a large number of critical sub-systems, components and equipment. Although the global seismic performance of building structures and their nonstructural components was extensively observed in several post-disaster reconnaissance surveys, there is limited and incomplete information on the effect of building and nonstructural damage on post-earthquake functionality. The objective of this paper is to present a methodology for the assessment of post-earthquake functionality of existing Montréal hospitals using fault-tree analysis. The study shows that using specific and accurate information on the vulnerability and fragility of structural and critical nonstructural components, a probabilistic index of post-earthquake functionality of the entire facility is computed which informs mitigation action for the critical failure processes through the system.

Simulation of failure of separate groups and subsystems of aerodrome lighting equipment

Presented is the technique of calculation of the possibility of distinguishing aerodrome lighting signals by the airplane crew in landing under difficult meteorological conditions. Designated are the ways of minimization of the number of signals of aerodrome lighting rings

Model assessment of risk of failure subsystem "man"

There are proposed the method of diagnostics of psychophysiological state of human-operator. There are presented the rationale the choose of informative parameters for evaluation of the psychophysiological state of man. On the basis of the using the mathematical apparatus of fuzzy logic model there are developed by the risk of failure of the subsystem "man" of man-machine system. In the form of a flowchart presents the analysis process incoming to the monitoring/control system, signals (biometric data) about the psychophysical state of the human-operator. One of the parameter groups characterizing the psychophysiological state of human-operator, who, to date, relatively often used in monitoring systems are the parameters of functioning of the human’s body. To assess the risk of failure of the system quantitatively and qualitatively, it is necessary to produce aggregated data collected as part of the tree hierarchy, while aggregation is done in the direction of the arcs of the graph hierarchy. The choice of this group of parameters is due, primarily to the fact that their control is easy to provide the contactless research methods. The latter fact is important, because the current production, as well as in everyday life or in training or competition modes athletes are almost always not possible to attach the sensors directly to the human body. The mathematical description of the calculation of risk, given the uncertainty and inaccuracy of the identification of the factors, the large number of assumptions and estimates, based on the theory of fuzzy sets, and suggests one solution algorithm problems, different in their original parametric data. On the basis of use the mathematical apparatus of fuzzy logic has been developed model for calculating the risk of failure of the subsystem "human" human-machine system. A mathematical model of risk assessment of failure of man-machine system and, consequently, in the future, a computer simulation model for evaluating the risk of failure of the subsystem "Man" can be developed on based of this model

Mathematical modeling and fuzzy availability analysis for serial processes in the crystallization system of a sugar plant

The binary states, i.e., success or failed state assumptions used in conventional reliability are inappropriate for reliability analysis of complex industrial systems due to lack of sufficient probabilistic information. For large complex systems, the uncertainty of each individual parameter enhances the uncertainty of the system reliability. In this paper, the concept of fuzzy reliability has been used for reliability analysis of the system, and the effect of coverage factor, failure and repair rates of subsystems on fuzzy availability for fault-tolerant crystallization system of sugar plant is analyzed. Mathematical modeling of the system is carried out using the mnemonic rule to derive Chapman–Kolmogorov differential equations. These governing differential equations are solved with Runge–Kutta fourth-order method.

Simplified spacecraft vulnerability assessments at component level in early design phase at the European Space Agency's Concurrent Design Facility

During recent years, the state-of-the-art risk assessment of the threat posed to spacecraft by micrometeoroids and space debris has been expanded to the analysis of failure modes of internal spacecraft components. This method can now be used to perform risk analyses for satellites to assess various failure levels – from failure of specific sub-systems to catastrophic break-up. This new assessment methodology is based on triple-wall ballistic limit equations (BLEs), specifically the Schäfer-Ryan-Lambert (SRL) BLE, which is applicable for describing failure threshold levels for satellite components following a hypervelocity impact. The methodology is implemented in the form of the software tool Particle Impact Risk and vulnerability Analysis Tool (PIRAT).During a recent European Space Agency (ESA) funded study, the PIRAT functionality was expanded in order to provide an interface to ESA's Concurrent Design Facility (CDF). The additions include a geometry importer and an OCDT (Open Concurrent Design Tool) interface. The new interface provides both the expanded geometrical flexibility, which is provided by external computer aided design (CAD) modelling, and an ease of import of existing data without the need for extensive preparation of the model.The reduced effort required to perform vulnerability analyses makes it feasible for application during early design phase, at which point modifications to satellite design can be undertaken with relatively little extra effort. The integration of PIRAT in the CDF represents the first time that vulnerability analyses can be performed in-session in ESA's CDF and the first time that comprehensive vulnerability studies can be applied cost-effectively in early design phase in general.

Analysis of the X-15 Flight 3-65-97 Divergent Limit-Cycle Oscillation

A brief history of the X-15-3 adaptive control system and an analysis of the destructive limit-cycle oscillation that occurred during its final November 1967 flight are presented. The X-15 was a piloted single-seat rocket-propelled hypersonic research aircraft operated by the NASA Flight Research Center from 1959 until 1968. Due to the limited information previously available in the public domain and the 1968 decision by the accident investigation board to forego detailed analysis of the adaptive control system’s role in the accident, it was widely assumed in the adaptive controls community that an anomalous behavior of the adaptive component caused the loss of control. Notwithstanding the complex human factors and subsystem failures that contributed to the accident, it is shown that the adaptation dynamics were not a causal factor. The limit cycle observed in the flight data is reproduced in a nonlinear time-domain simulation. Describing function analysis reveals that the instability was caused by a latent design error in the inner-loop structural filters that did not account for the nonlinear behavior of the X-15 servoactuator under rate saturation when coupled with the lightly damped aircraft longitudinal mode at high Mach numbers.

Fault tree analysis method for deterioration of timber bridges using an Australian case study

Purpose – Deterioration of timber bridges can often be related to a number of deficiencies in the bridge elements, connectors and/or as a result of been in aggressive environments which they are exposed to. The maintenance cost of timber bridges is affected significantly by a number of deterioration mechanisms which require a systematic approach for diagnosis and treatment. Evaluating the risk of failure of these bridges is of importance in bridge performance assessment and decision making to optimize rehabilitation options. The paper aims to discuss these issues. Design/methodology/approach – This paper identifies common causes for timber bridge deterioration and demonstrates an integrated approach based on fault tree analysis to obtain qualitative or quantitative estimation of the risk of failure of timber bridge sub-systems. Level 2 inspection report for a timber bridge in Queensland, Australia has been utilized as a case study in this research to identify the failure modes of the bridge. Findings – A diagnostic tool for timber bridge deterioration will benefit asset inspectors, managers, and engineers to identify the type, size and the distress mechanisms in order to recognize the proper corrective measures either to prevent or to reduce further deterioration. Timber bridge maintenance is a major issue in Queensland, Australia. If a decision support tool can be developed, it will benefit road authorities and local councils. Originality/value – Timber bridge maintenance is a major issue in Queensland, Australia. If a decision support tool can be developed as initiated in this research paper it will benefit road authorities and local councils.

An integrated hazard identification method based on the hierarchical Colored Petri Net

The traditional hazard analysis approaches applied to the socio-technical system cannot cover the complex organization structures, the interactions between systems and human behaviors, the interrelated factors among sub-systems and the safety culture of specific societies. This paper presents an integrated hazard identification approach named System-Theoretic Process Analysis Based on Formalization Model (BFM-STPA), which can solve the above issues. Firstly, the hierarchical control structure models of the socio-technical system are established through Colored Petri Nets (CPN) due to its strong description ability and executable ability, which may also be regarded as the graphical system specification. Secondly, the hazards can be identified according to the CPN models following a series of guide conditions. Thirdly, the comprehensive contributing factors to the hazards will be found out by tracing the former states within the reachability graph generated from CPN model. Finally, an integrated hazard log can be derived for further hazard analysis and safety-guided design. In this paper, the above method was applied in the Chinese Train Control System level 3 (CTCS-3). And the process of hazard identification for the scenario of Temporary Speed Restriction issued was elaborated in detail. Compared with the hazard log generated by Hazard and Operability (HAZOP), the hazard log generated by BFM-STPA covered not only the subsystem failures, but also the deviation of interactions among subsystems from design intent, human errors and socio-technical drawbacks related to the TSR Issued scenario of CTCS-3.

Failure probability estimation under additional subsystem information with application to semiconductor burn-in

ABSTRACTIn the classical approach to qualitative reliability demonstration, system failure probabilities are estimated based on a binomial sample drawn from the running production. In this paper, we show how to take account of additional available sampling information for some or even all subsystems of a current system under test with serial reliability structure. In that connection, we present two approaches, a frequentist and a Bayesian one, for assessing an upper bound for the failure probability of serial systems under binomial subsystem data. In the frequentist approach, we introduce (i) a new way of deriving the probability distribution for the number of system failures, which might be randomly assembled from the failed subsystems and (ii) a more accurate estimator for the Clopper–Pearson upper bound using a beta mixture distribution. In the Bayesian approach, however, we infer the posterior distribution for the system failure probability on the basis of the system/subsystem testing results and a prior distribution for the subsystem failure probabilities. We propose three different prior distributions and compare their performances in the context of high reliability testing. Finally, we apply the proposed methods to reduce the efforts of semiconductor burn-in studies by considering synergies such as comparable chip layers, among different chip technologies.

Comparison of immunity-based schemes for aircraft failure detection and identification

In this paper, two approaches are proposed and compared for the detection and identification of aircraft subsystem failures based on the artificial immune system paradigm combined with the hierarchical multiself strategy. The first approach relies on the heuristic ranking of lower order self/non-self projections and the generation of selective immunity identifiers through structuring of the non-self. The second approach is based on an information processing algorithm inspired by the functionality of the dendritic cells. The artificial dendritic cell is defined as a computational unit that centralizes, fuses, and interprets information from the multiple selves to produce a unique detection and identification outcome. A hierarchical multi-self strategy is used with both approaches considering 2-dimensional self/non-self projections or subselves. A mathematical formulation of the concepts and detailed implementation algorithms are presented. The proposed methodologies are demonstrated and compared using simulation data for a supersonic fighter from a motion-based flight simulator at nominal conditions, under failures of actuators, malfunction of sensors, and wing damage. In all cases considered, both detection and identification schemes achieve excellent detection and identification rates with practically no false alarms.

Shock Propagation in Cascade Systems: Analysis and Applications

In this paper, we study shock propagation in cascade systems that can be a model of outage of power systems and that of spreading a fad. While existing research works have dealt with a certain relationship between global cascade and system properties, such as degree and distribution of threshold values, and interconnection topology, this paper addresses new engineering problems of the cascade systems. Mainly, we would like to 1) identify subsystems contributing to a large cascade, 2) develop a strategy that prevents all initial failures within a designated region from cascading out of the region, and 3) develop a strategy that prevents all initial failures outside of the region from cascading into the region. In order to solve these challenging problems, we develop an invariant set analysis method for cascade models and derive some features inherent to the cascade systems. As the first feature, supposing that we know the resulting cascade region from the given initial failures in specific subsystems, we will show that the cascading of initial failures of any combination of the subsystems cannot exceed the region. The second feature is a graph theoretic distance condition, which guarantees that two cascading regions are never combined together. Based on the analytical results, we develop algorithms solving the aforementioned engineering problems, in which the complexity of the computation is reduced.