Qualitative analysis for state/event fault trees using formal model checking

A state/event fault tree(SEFT)is a modeling technique for describing the causal chains of events leading to failure in software-controlled complex systems.Such systems are ubiquitous in all areas of everyday life,and safety and reliability analyses are increasingly required for these systems.SEFTs combine elements from the traditional fault tree with elements from state-based techniques.In the context of the real-time safety-critical systems,SEFTs do not describe the time properties and important timedependent system behaviors that can lead to system failures.Further,SEFTs lack the precise semantics required for formally modeling time behaviors.In this paper,we present a qualitative analysis method for SEFTs based on transformation from SEFT to timed automata(TA),and use the model checker UPPAAL to verify system requirements’properties.The combination of SEFT and TA is an important step towards an integrated design and verification process for real-time safety-critical systems.Finally,we present a case study of a powerboat autopilot system to confirm our method is viable and valid after achieving the verification goal step by step.

Automatic Derivation of Fault Tree Models from SysML Models for Safety Analysis

Safety Critical Systems (SCS) are those systems that may cause harm to the user(s) and/or the environment if operating outside of their prescribed specifications. Such systems are used in a wide variety of domains, such as aerospace, automotive, railway transportation and healthcare. In this paper, we propose an approach to integrate safety analysis of SCSs within the Model Driven Engineering (MDE) system development process. The approach is based on model transformation and uses standard well-known techniques and open source tools for the modeling and analysis of SCSs. More specifically, the system modeled with the OMG’s standard systems modeling language, SysML, is automatically transformed in Fault Tree (FT) models, that can be analyzed with existing FT tools. The proposed model transformation takes place in two steps: a) generate FTs at the component level, in order to tackle complexity and enable reuse;and b) generate system level FTs by composing the components and their FTs. The approach is illustrated by applying it to a simplified industry-inspired case study.

Interval Fault Tree Analysis of Excavator VariableFrequency Speed Control System

In consideration of the uncertainty of basic events failure rate and lack of probability statistical information in fault tree analysis( FTA) of excavator variable-frequency speed control system, the interval theory was employed and combined with conventional FTA method. The basic events failure probabilities were described by interval numbers,and the interval operators of logical gates in FTA were deduced based on interval theory. Finally,the reliability assessment of excavator variable-frequency speed control system was done by interval FTA method. The result shows that the interval FTA method is suitable for the complex system with insufficient failure data.

Fault Tree Analysis of CNC Machine Tool Based on BDD Technology

CNC machine tool is a large complex system which contains both mechanical and electrical components.As one of these components,the spindle is crucial for the performance of CNC machine tool.To improve the quality of CNC machine,the reliability of spindle was evaluated in this paper using a fault tree analysis(FTA)method.The FTA method is a set of calculation methods based on Boolean algebra.However,it is difficult to analyze a large and complex fault tree with inaccurate results and low efficiency as well as the complexity of time and space.Both of them will result in the so-called "combinatorial explosion".To overcome this problem,the analysis method based on binary decision diagram(BDD)was introduced in our works,and a sorting method about bottom events was also recommended which can reduce the size of the BDD effectively.

FTA在应急通信车网络故障诊断系统的应用

针对应急通信车通信网络综合组网复杂性和故障关联关系复杂性越来越高的问题,提出了基于故障树分析(Fault Tree Analysis,FTA)法的应急通信车通信网络故障集中诊断方法。该方法可以实现通信网络故障的快速诊断,并能够将诊断结果反馈到应急通信车智能通信网络管控系统,通过故障专家知识库支撑和资源调控智能化辅助,实现人工干预或通信网络自适应快速调整和恢复,从而提升应急通信车可靠性、维修性水平。该设计方法可推广应用到大型复杂通信系统和通信、指挥车辆平台通信网络的运维管理系统中,具有较广阔的设计分析和工程应用前景。

Revised Fault Free Analysis Method for Reliability Evaluation of Smart Grids

Smart grid was proposed as a practical form of future power distribution system. Evaluating the reliability of smart grids was of great importance and significance. A revised fault tree model was proposed to distinguish and separate grid-connected operation mode and islanded operation mode of smart grids,focusing on the perspective of the consumers. A hierarchical Monte Carlo simulation method for reliability evaluation was also proposed based on the proposed fault tree model. A case of reliability evaluation for the future renewable electric energy delivery and management( FREEDM) system was carried out and analyzed. The proposed methods can be applicable to other forms of smart grids.

基于FTA法的甬温线特别重大铁路事故分析

为保障铁路运输安全,提升运输效率。以“7·23”甬温线特别重大铁路交通事故为研究对象,采用事故树分析法(FTA)对事故原因进行定性与定量分析,并对影响因素进行重要度排序,找出对事故发生影响敏感度最高的关键因素。针对分析结果,从人员、设备、环境、管理四个方面提出切实可行的改进措施,为杜绝此类事故的发生,保障旅客出行安全,增强铁路运输系统的安全性提供参考。

基于FTA和ISM的有限空间中毒窒息事故致因分析

为减少有限空间作业中毒窒息事故的发生率,提高有限空间作业的安全管理水平,应用事故树分析方法(FTA)和解释结构模型(ISM)分析有限空间作业中毒窒息事故的致因因素及因素间的相互关系。首先,建立有限空间作业中毒窒息事故树并求出基本事件的结构重要度;其次,将基本事件进行归类和修正后得到ISM的致因因素;再次,利用ISM理论构建7个层级的表明致因因素间关系的解释结构模型(ISM)。结果表明:ISM层级间存在根本影响因素向间接影响因素递阶,进而向直接影响因素递阶的关系。因此,可以通过加强根本影响因素的管理提高间接影响因素的安全状态,从而降低直接影响因素的发生率。

FTA-BN在机场跑道入侵事故影响因素分析中的应用

为了分析机场跑道侵入的影响因素,更有针对性地对预防机场跑道侵入提出合理建议,结合相关信息通告中统计的数据,首先从人员因素、环境因素、设备因素和管理因素4个方面分析跑道侵入的事故成因,并建立了故障树(Fault Tree Analysis,FTA)模型和贝叶斯网络(Bayesian Network,BN)模型,然后利用软件Netica对贝叶斯网络模型进行了后验概率推理与敏感性分析,最后根据分析结果提出了相应的建议。结果表明,人员因素影响程度最大,其次是管理因素,而环境因素和设备因素的影响程度相对偏小。

基于FTA-BN模型的有限空间作业事故案例分析

为了减小有限空间的作业风险,降低事故发生率,本研究构建了有限空间作业的事故树—贝叶斯网络事故致因模型(FTA-BN模型),用事故树分析法全面梳理出“人—机—环—管”4个维度的风险因素,结合作业事故数据采用专家打分和模糊数处理定量得出基本事件的发生概率,再通过贝叶斯网络计算出所有事件的后验概率。结果表明:盲目施救、中毒窒息、燃烧爆炸等是有限空间作业事故发生的主要风险因素,针对分析结果提出了更有针对性的对策措施,验证了该模型的可行性和适用性。

基于FTA在装配式建筑施工过程中的风险分析

随着装配式建筑的迅速发展,施工风险也随之出现,但由于现有的风险识别方法的识别效率较低,基于故障树分析方法(FTA)在复杂系统面前对风险识别的优势,确定其作为判明潜在故障原因的方法。本文介绍了故障树分析法的原理,通过理论与实践相给合,利用定性分析和定量分析方法,确定故障原因各种可能组合方式的风险概率与重要度,发现安全性的薄弱环节,并采取相应改进措施,以提高产品可靠性和安全性,从而系统地为装配式建筑施工过程提供指导与参考。

基于FTA-BN的云ERP不安全事件的人因失误分析

为明确云企业资源计划(ERP)不安全事件的人因失误因素,构建基于故障树分析-贝叶斯网络(FTA-BN)的人因失误分析模型,以避免单一方法的局限性。首先,对云ERP安全审计记录披露的不安全事件进行分类和追因分析,构建云ERP不安全事件故障树,并定量分析最小割集、结构重要度;然后,将故障树映射为BN结构,利用案例数据进行结构学习和参数学习得到最终的贝叶斯网络;最后,依托贝叶斯网络的敏感性分析辨识关键人因失误因素,凭借预测推理计算发生不安全事件的概率。研究结果表明:云ERP安全人因失误因素中工作不到位、培训不足、资源分配不足、管理流程存在问题、职责不清等因素在对应的事件域中应得到重点关注,以保障持续安全。

基于FTA的生鲜农产品冷链物流失温风险识别研究

伴随着生鲜农产品的需求量与日俱增,因失温而导致的冷链物流断链的风险日益突出。运用FTA方法构建生鲜农产品冷链失温风险的故障树模型,并利用收集整理得到的近年来生鲜农产品发生失温风险的数据进行定量分析,求出最小割集以及失效概率,对基本事件和最小割集进行重要度排序,最后制定有针对性的风险防控策略。

FTA与BP神经网络结合的地平仪故障诊断方法研究

为了提高某型地平仪常见故障的诊断效率与准确率,研究了故障树分析(FTA)与反向传播(BP)神经网络相结合的地平仪故障诊断方法。根据地平仪的结构原理,首先采用FTA法得到了该型地平仪的所有故障模式及最小割集,建立了故障树的结构函数。然后按照最小割集重要度,筛选出BP神经网络训练样本的主要故障模式。最后以某单位该型地平仪的故障统计数据为基础,运用BP神经网络的方法建立了地平仪的故障诊断模型,并对模型进行了验证。验证结果表明,采用FTA法与BP神经网络相结合的故障诊断方法,弥补了2种方法单独诊断时的固有缺陷,提高了故障诊断的准确性和效率。

Reliability Analysis of Unmanned Aerial Vehicles Flight Control System Based on Reliability Analysis Technologies

The unmanned aerial vehicles( UAV) has been becoming more and more important in the aviation industry.Despite the superior performance and advanced technology,major accident of UAV happens frequently due to the impact of their systems,long distance of remote control and skill of manipulator technology.According to the application of engineering application,failure mode effects and criticality analysis( FMECA),failure reporting analysis and corrective action comprehensive analysis systems( FRACAS)and fault tree analysis( FTA)( 3 F) were combined.And also a set of user-friendly,more time,more efficient and accurate reliability analysis system were explored.

Prediction of the Behavior of a Power System Using Root Cause Failure Analysis

The thermo-economic performance of a gas turbine is simulated using a fish bone technique to characterize the major equipment failure causes.Moreover a fault tree analysis and a Pareto technique are implemented to identify the related failure modes,and the percentage and frequency of failures,respectively.A pump 101 and drier 301 belonging to the Tabriz Petrochemical Company are considered for such analysis,which is complemented with a regression method to determine a behavioral model of this equipment over a twenty-year period.Research findings indicate that 81%of major failure factors in production equipment are related to the executive procedures(24%),human error(22%),poor quality of materials and parts(20%),and lack of personnel training(15%).

基于FTA优化CPSO算法的锻压机典型故障诊断研究

为适应多种类型的产品加工需求,锻压机具高度自动化控制能力的提高尤为重要。采用单一智能故障诊断算法无法达到高的故障诊断率以及需要设置复杂的诊断措施等,综合故障树分析(FTA)与混沌粒子群(CPSO)算法相结合方式实现故障诊断。分析实际传感器测点,并与GA与PSO算法结果进行对比。结果表明:FTA-CPSO算法的故障诊断准确率比GA高6.25%,比PSO高4.20%;FTA-CPSO算法可以获得较小的误差,相对GA与PSO达到了更优的诊断性能;经过多次迭代后,所有算法的适应值都减小;FTA-CPSO可以在最短时间内完成迭代计算,有效降低迭代次数,同时搜索时间也明显缩短。

基于FTA的电厂电力调度数据网通信系统可靠性分析

国网电力调度数据网是用于电厂电力生产调度的专用数据网络,其安全稳定运行直接关系到电网与电厂间的功率负荷等数据的实时传输可靠性。电厂电力调度数据系统在关键重要设备中采取了冗余配置的结构,提升系统的可靠度。通过分析电力调度数据系统的结构与逻辑关系,构建其故障树模型。通过对其层级划分,结合底层设备的可靠性参数,逐层计算系统可靠度,通过仿真实验,定量计算了具体的可靠性指标。根据仿真实验计算结果,构建更加合适的维护策略。

基于FTA和FAHP耦合的可燃性粉尘爆炸风险分析

为了给粉尘涉爆企业制定有效的防爆措施提供依据,以木纤维粉尘爆炸为例分析粉尘爆炸风险,提出一种基于事故树分析法和模糊层次分析法于一体的粉尘爆炸风险分析方法。首先,利用事故树分析法进行演绎推理得到发生粉尘爆炸事故的基本致因事件,同时采用结构重要度进行定性分析;其次,将事故树的基本事件按人、设备、环境、管理及物料5个方面整合后构建粉尘爆炸评价指标体系;最后,再利用模糊层次分析法构建判断矩阵进行定量分析。结果表明:结构重要度系数最大的是设施内部和作业场所含有充足的氧气、正压吹扫扬尘及室内作业扬尘;发生粉尘爆炸事故风险最大的因素是未及时清理粉尘。