An efficient reliability evaluation method for industrial wireless sensor networks

Aimed at the difficulties in accurately, comprehensively and systematically evaluating the reliability of industrial wireless sensor networks （WSNs）, a time-evolving state transition-Monte Carlo （TEST-MC） evaluation method and a novel network function value representation method are proposed to evaluate the reliability of the IWSNs. First, the adjacency matrix method is used to characterize three typical topologies of WSNs including the mesh network, tree network and ribbon network. Secondly, the network function value method is used to evaluate the network connectivity, and the TEST-MC evaluation method is used to evaluate network reliability and availability. Finally, the variations in the reliability, connectivity and availability of these three topologies are presented. Simulation results show that the proposed method can quickly analyze the reliability of the networks containing typical WSN topologies, which provides an effective method for the comprehensive and accurate evaluation of the reliability of WSNs.

RELIABILITY EVALUATION MODEL BASED ON DATA FUSION FOR AIRCRAFT ENGINES

Reliability evaluation for aircraft engines is difficult because of the scarcity of failure data. But aircraft engine data are available from a variety of sources. Data fusion has the function of maximizing the amount of valu- able information extracted from disparate data sources to obtain the comprehensive reliability knowledge. Consid- ering the degradation failure and the catastrophic failure simultaneously, which are competing risks and can affect the reliability, a reliability evaluation model based on data fusion for aircraft engines is developed, Above the characteristics of the proposed model, reliability evaluation is more feasible than that by only utilizing failure data alone, and is also more accurate than that by only considering single failure mode. Example shows the effective- ness of the proposed model.

Reliability Evaluation of Machine Center Components Based on Cascading Failure Analysis

In order to rectify the problems that the com- ponent reliability model exhibits deviation, and the evalu- ation result is low due to the overlook of failure propagation in traditional reliability evaluation of machine center components, a new reliability evaluation method based on cascading failure analysis and the failure influ- enced degree assessment is proposed. A direct graph model of cascading failure among components is established according to cascading failure mechanism analysis and graph theory. The failure influenced degrees of the system components are assessed by the adjacency matrix and its transposition, combined with the Pagerank algorithm. Based on the comprehensive failure probability function and total probability formula, the inherent failure proba- bility function is determined to realize the reliability evaluation of the system components. Finally, the method is applied to a machine center, it shows the following： 1） The reliability evaluation values of the proposed method are at least 2.5% higher than those of the traditional method; 2） The difference between the comprehensive and inherent reliability of the system component presents a positive correlation with the failure influenced degree ofthe system component, which provides a theoretical basis for reliability allocation of machine center system.

Reliability Evaluation of All-User Terminals in LEO Satellite Communication Network Based on Modular Reduction

LEO satellite communication network has a large number of satellites distributed in low orbits,which leads to multiple coverage of many areas on the ground.It is hard work to describe and evaluate the reliability of LEO satellite communication network.To solve this problem,the reliability of all-user terminals in LEO satellite communication network is defined,and the corresponding reliability evaluation method is proposed in the paper.Due to the large scale of the interstellar network,a modular reduction algorithm using the modular network instead of the original network for state decomposition is proposed in this paper.Case study shows that the calculation time of the proposed method is equivalent to 6.28%of the original state space decomposition algorithm.On this basis,the reliability of LEO satellite communication network is further analyzed.It is found that the reliability of LEO satellite network was more sensitive to the reliability of Inter-Satellite link and the satisfaction of global coverage in the early stage,and it is more sensitive to the reliability of the satellite in the later stage.The satellite-ground link has a relatively constant impact on of LEO satellite network.

Reliability evaluation method and algorithm for electromechanical product

The reliability of electromechanical product is usually determined by the fault number and working time traditionally. The shortcoming of this method is that the product must be in service. To design and enhance the reliability of the electromechanical product, the reliability evaluation method must be feasible and correct. Reliability evaluation method and algorithm were proposed. The reliability of product can be calculated by the reliability of subsystems which can be gained by experiment or historical data. The reliability of the machining center was evaluated by the method and algorithm as one example. The calculation result shows that the solution accuracy of mean time between failures is 97.4% calculated by the method proposed in this article compared by the traditional method. The method and algorithm can be used to evaluate the reliability of electromechanical product before it is in service.

Reliability Evaluation Metrics for Open Source Software Selection

Recently, Open Source Software （OSS） is so widely used not only by companies for development but also by common users instead of commercial software. However, the number of OSS is vast, and its quality varies from low to high. So how people can evaluate OSS and ensta-e that it is reliable for use becomes necessary. This paper proposes a set of reliability evaluation metrics considering the states of OSS selected in the early stage. Understandability, Fault tolerance ＆ Recoverability and Community Matmrity as sub-attributes of reliability are defined, and then several evaluation criteria for each of them are identified. A process of reliability evaluation in our study is proposed. For application, we select four OSS projects and evaluate them with our metrics. As a result of compadrison with other evaluation model for OSS, our research presents an easy, effective and trustworthy way for selecting a reliable OSS.

The System Analysis and Reliability Evaluation of Rock Slopes

The principal of preferred plane analysis is a new research view and model of rock slope engineering geology. It advocates that the rock slope stability, boundary conditions and failure model are controlled by preferred planes. Therefore, the problem of slope stability evaluation can be converted into the search for preferred planes and determination of preferred separating bodies. The organic combination of the deterministic model and the indeterministic model can be realized by applying the systems engineering principle and the research model and method of reliability analysis in the quantitative evaluation and prediction of rock slope stability. Finally, the paper presents the case studies of slopes of the Yangtze Gorge Project and the Ma'anshan openpit mine.

Reliability evaluation on CNC lathes based on the modified L-M method

Equivalent ways commonly used in engineering works are not effective to estimate the reliability of tandem system based on L-M method. One modified L-M method is an important means to estimate the reliability of CNC lathes. A method of using two named confidence limits for the estimation is put forward. Fitting resuits of the sub-systems of CNC machine tools are estimated. And the scattered level of confidence limits facing the reliability matrix of sub-systems can be clearly seen.

Reliability Evaluation and Sensitivity Analysis for Multi-state System Based on Time Degradation Measures

The performance and state of multi-state system depend on its structure and different state combinations of the components. In order to evaluate the reliability of multi-state system effectively,a reliability evaluation and sensitivity analysis method based on the time degradation measures was proposed. The equivalence sets of the multi-state system under different output performances were established. The state combinations were classified according to the performance level. The degradation probability models under different states were established,and the new reliability measures,such as dynamic probability of multi-state system,holding time in each state,dynamic expectation function and integrated expectation function of the performance,were proposed and used to implement the dynamic reliability evaluation and sensitivity analysis. A certain diesel engine fuel feeding system was taken as an application example to illustrate the proposed method. The results show that not only the holding time in the desired state of the components and the system can be predicted,but also the best state component in a certain time period can be obtained.

Reliability Evaluation of Wind Power Converter Under Fault-tolerant Control Scheme with Quantification of Temperature and Humidity Effects

Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurately evaluate the reliability of WPC,which is crucial for the design and maintenance of wind turbines.Firstly,the index of effective temperature(ET)is presented to quantify the effects of temperature and humidity on the semiconductor operation.A novel method is proposed to evaluate the lifetime and calculate the aging failure rates of the semiconductors considering the fluctuations of ET.Secondly,the failure mode and effect analysis(FMEA)of WPC is investigated based on the topology and control scheme.The conventional two-state reliability model of the WPC is extended to the multi-state reliability model where the partial working state under the fault-tolerant control scheme is allowed.Finally,a reliability evaluation framework is established to calculate the parameters of the WPC reliability model considering the variable failure rates and repair activities of semiconductors.Case studies are designed to verfify the proposed method using a practical wind turbine.

Reliability Evaluation of Electricity-heat Integrated Energy System with Heat Pump

Integrated energy system(IES)has the advantages of improving the efficiency of energy utilization and promoting the consumption of renewable energy.It is of great importance to evaluate the reliability of an IES.This paper proposes a novel reliability evaluation method for the electricity-heat IES with heat pump.First,the load-point reliability indices and systemlevel reliability indices are defined according to the characteristics of electricity-heat IES.Second,the model of maximum output heat power of heat pump at the user-side considering the safety criterion of distribution network is established,and the stepvaried repeated power flow method is applied to solve the model.Third,the reliability evaluation procedure of electricityheat IES with heat pump based on the Monte Carlo simulation is presented.Case studies are carried out on the electricityheat IES of an industrial park,and the results show that the configuration site,capacity and coefficient of performance of heat pump as well as the security constraints of distribution network can significantly affect the reliability indices.

Reliability evaluation of avionics system with imperfect fault coverage and propagated failure mechanisms

Fault tolerance designs are essential techniques for systems that require high levels of reliability,such as aircraft or spacecraft control system.Imperfect Fault Coverage(IFC)may lead to the failure of a system or subsystem even with adequate redundancy.Previous studies of IFC mostly concentrated on evaluating Coverage Factor(CF),whereas the system failure behaviors with IFC have rarely been involved.Failures that occur in low-layer may be covered by highlayer.However,if the coverage is imperfect,uncovered failure will have functional and physical impact on the system behavior.In this thesis,the failure behavior and reliability of IFC of multi-layer systems are studied and a Binary Decision Diagram(BDD)-based modeling and simulation method are proposed to evaluate system reliability.As a case,the failure behavior of an aero engine electronic controller with IFC is studied.The results show that the IFC may impact system behavior without taking the IFC into account,the system maintenance intervals may reduce,and thus the maintenance costs will increase.

Reliability evaluation of the roll motion under the wind and irregular beam waves

This paper intends to study the stochastic response and reliability of the roll motion under the action of wind and wave excitation.The roll motion in random beam seas is described by a four-dimensional(4D)Markov dynamic system whose probabilistic properties are governed by the Fokker-Planck(FP)equation.The 4D path integration(PI)method,an efficient numerical technique based on the Markov property of the 4D system,is applied in order to solve the high dimensional FP equation and then the stochastic statistics of the roll motion are derived.Based on the obtained response statistics,the reliability evaluation of the ship stability is performed and the effect of wind action is studied.The accuracy of the 4D PI method and the reliability evaluation is assessed by the versatile Monte Carlo simulation(MCS)method.

Reliability evaluation of tidal and wind power generation system with battery energy storage

This paper presents a method for reliability evaluation of a hybrid generation system of wind and tidal powers with battery energy storage.Such a system may widely exist in coastal areas and islands in the future.A chronological multiple state probability model of tidal power generation system(TPGS)considering both forced outage rate(FOR)of the TPGS and random nature of tidal current speed is developed.In the evaluation of FORs of TPGS and WPGS(wind power generation system),the delivered power related failure rates of power electronic converters for TPGS and WPGS are considered.A chronological power output model of battery energy storage system(BESS)is derived.A hybrid system of tidal and wind generation powers with a BESS is used to demonstrate the effectiveness of the presented method.In case studies,the effects of various parameters on the system reliability are investigated.

Reliability evaluation of PMS considering coupling effect of functional and physical dependency

Aviation and aerospace system are typical Phased-Mission Systems(PMSs)featured with varying configuration,phased load condition and cross phase failure correlation.The coupling effect of Functional Dependency(FDEP)and Physical Dependency(PDEP)has a unique influence on the failure behavior of PMS.In this article,the coupling effect is analyzed,and the degradation of components is modeled with the positive drift wiener process,in which the drift coefficient is related to environmental conditions and operation stress.Finally,failure behavior and system reliability are simulated.An avionics controller is studied as a case,with the degradation time distribution model and simulation algorithm,the coupling effect and dynamical system reliability can be achieved.Results show that this modeling method can describe the coupling effects of FDEP and PDEP and their influence on the failure behavior and reliability of the PMS system.

Distribution System Reliability Evaluation Taking Circuit Capacity into Consideration

Distribution system reliability evaluation using the method of connectivity ignores the effect of operation constraints. This paper presents an approach that includes the effect of circuit capacity. Reliability evaluation of distribution systems with parallel circuits generally requires load flow solutions. The proposed approach combines the Z-matrix contingency method with DC load flow for a much faster direct solution. Three different methods for distribution system reliability evaluation have been incorporated into a computer program. The program was validated using two distribution systems connected to the IEEE-RTS and another sample distribution system.

Reliability Evaluation of Two-Phase Degradation Process with a Fuzzy Change-Point

For some products,degradation mechanisms change during testing,and therefore,their degradation patterns vary at different points in time;these points are called change-points.Owing to the limitation of measurement costs,time intervals for degradation measurements are usually very long,and thus,the value of change-points cannot be determined.Conventionally,a certain degradation measurement is selected as the change-point in a two-phase degradation process.According to the tendency of the two-phase degradation process,the change-point is probably located in the interval between two neighboring degradation measurements,and it is a fuzzy variable.The imprecision of the change-point may lead to the incorrect product’s reliability evaluation results.In this paper,based on the fuzzy theory,a two-phase degradation model with a fuzzy change-point and a statistical analysis method are proposed.First,a two-phase Wiener degradation model is developed according to the membership function of the change-point.Second,the reliability evaluation is carried out using maximum likelihood estimation and a fuzzy simulation approach.Finally,the proposed methodology is verified via a case study.The results of the study show that the proposed methodology can achieve more believable reliability evaluation results compared with those of the conventional approach.

Reliability Evaluation Method Based on Double Beta Prior Distribution for the Pyrotechnic Device

On the basis of the Bayesian principle, a method of selecting the double beta distribution as a priori distribution is proposed for the system reliability evaluation when the available field test samples are small for pyrotechnic device. Under the condition of different field and historical data, the mean square error(MSE) and coverage ratio(CR) of the reliability evaluation are compared by numerical simulation when the conjugate distribution and uniform distribution are selected as the priori distribution. Finally, the rationality and engineering applicability of the proposed method are verified through an example of the reliability evaluation of a typical pyrotechnic device.

EVALUATION OF THE GEOLOGICAL RELIABILITY OF SURFACE MINING DEPOSIT

The optimal deeision theory and exploitation reliability of large scale mining area have been studied China since the late 1980’s. Researches have been earried out under the thought of mannature - machine system , and eneouraging results have been obtained. The reliability evaluation of mining engineering ineludes the rellability exaluation of natural resources, mining technology and mine economics ete. And the geological reliability of deposit, as a natural condition, is the basis of all other evaiuation works. The paper summarizes the method for evaluating the geological reliaoility of deposit, diseusces the reliability of estimating methods for coal reserves and coai quality, evaiuates the natural resourees rellability of the Pit 1 of Antaibao Surface Coai Mine, Pingsuo, Shanxi Province.which was taken as a case study.

Assessment of Dependent Performance Shaping Factors in SPAR-H Based on Pearson Correlation Coefficient

With the improvement of equipment reliability,human factors have become the most uncertain part in the system.The standardized Plant Analysis of Risk-Human Reliability Analysis(SPAR-H)method is a reliable method in the field of human reliability analysis(HRA)to evaluate human reliability and assess risk in large complex systems.However,the classical SPAR-H method does not consider the dependencies among performance shaping factors(PSFs),whichmay cause overestimation or underestimation of the risk of the actual situation.To address this issue,this paper proposes a new method to deal with the dependencies among PSFs in SPAR-H based on the Pearson correlation coefficient.First,the dependence between every two PSFs is measured by the Pearson correlation coefficient.Second,the weights of the PSFs are obtained by considering the total dependence degree.Finally,PSFs’multipliers are modified based on the weights of corresponding PSFs,and then used in the calculating of human error probability(HEP).A case study is used to illustrate the procedure and effectiveness of the proposed method.