T-S模糊故障树分析方法

提出一种新的T-S模糊故障树分析方法,该方法将模糊逻辑和T-S模糊模型引入到故障树分析中,使故障树具有处理模糊信息的能力.T-S模糊故障树分析中不需要精确了解部件的故障概率,也不需要精确了解故障的机理,从而解决了系统的事件和故障机理的不确定性问题.最后给出了INS/GPS组合导航系统可靠性分析实例.     

基于FFAT的装载机液压系统故障诊断

在分析装载机液压系统故障特征的基础上,建立了液压系统的故障树层次模型,针对故障树底事件和中间事件发生概率情况获取不足的现状,将模糊集合理论引入到故障树分析中,采用模糊数来刻画事件发生概率,利用模糊重要度来描述底事件对顶事件的影响,并以装载机液压系统中"工作泵"故障树为例进行了分析.结果说明,该方法具有较强的灵活性和适用性.     

基于T-S模糊故障树的混凝土泵车泵送液压系统故障诊断

针对混凝土泵车泵送液压系统结构复杂,故障发生概率、故障机理和故障程度具有模糊性的特点,提出了基于T-S模糊故障树的泵送液压系统故障诊断方法。该方法用模糊数描述液压元件和系统的故障概率,解决了故障概率的不确定性;用T-S模糊门描述事件间的联系,解决了故障机理和事件联系的模糊性;用模糊数描述故障的严重程度,考虑了故障程度对系统的影响。将该方法运用到了混凝土泵车泵送液压系统的故障诊断中,取得了较好的效果。     

基于模糊理论动车制动系统故障树可靠性分析

动车组制动系统在可靠性分析过程中存在故障数据的不确定性问题,主要表现为数据的来源不同和事件语义表述不同等,导致很难获取系统事件发生概率的精确数值。因此传统的故障树分析方法对于这类问题的处理不能得到符合现实条件的准确数据结果,故提出运用模糊数学理论将事件的发生概率进行模糊化处理,并结合专家信心指数法通过故障树分析模型计算得出制动系统底事件的模糊概率重要度,并根据各底事件在不同故障状态情况下的模糊概率重要度的大小,找出影响系统可靠性的薄弱环节。通过对兰新客专上运行的动车组制动系统进行分析,结果与动车组制动系统实际运行情况相符合,验证了算法的可行性和有效性。为根据该线路故障的特点制定相应的检修和维护策略给出了理论依据。     

基于故障树的柔索驱动拣矸机器人系统分拣可靠性研究

拣矸机器人的分拣可靠性与煤的品质及分拣效率息息相关,对拣矸机器人系统分拣可靠性进行研究十分必要。现有机器人系统可靠性研究主要是针对其结构可靠性进行研究,而没有对其工作任务可靠性即分拣可靠性进行研究。针对该问题,以柔索驱动拣矸机器人系统为研究对象,采用故障树分析法对其分拣可靠性进行研究。首先,从拣矸机器人系统的结构出发,分析了拣矸机器人系统分拣故障的原因,采用演绎法构建拣矸机器人系统的分拣故障树;然后,将故障树底事件发生概率考虑为区间变量,根据区间性质、运算法则和顶事件的概率表达式得到分拣故障树顶事件概率区间参数,结合设计要求计算出反映拣矸机器人系统分拣可靠性的非概率可靠性指标;最后,基于非概率可靠性指标公式及模糊重要度定义,提出了一种区间重要度指标,对分拣故障树底事件的区间重要度进行求解并排序,结果表明分拣可靠性满足拣矸机器人可靠分拣要求,煤矸石流瞬时含矸率增大和工业相机故障是影响其分拣可靠性的重要因素。根据非概率可靠性指标计算结果和区间重要度排序找出了拣矸机器人系统的薄弱环节,并针对薄弱环节提出了3个改进措施：在分拣前对煤矸石流振荡混合;根据识别的矸石信息,智能控制带式输送机带速;在...     

基于故障树-贝叶斯网络的受电弓系统可靠性评估

受电弓是城市轨道交通车辆重要电气设备,其稳定性直接影响车辆受流稳定性,受电弓的良好性能是车辆安全运营的保证之一.针对受电弓系统可靠性评估故障树分析法的局限性,将故障树分析法与贝叶斯网络相结合进行受电弓系统可靠性的分析研究.该方法不但能计算出受电弓系统可靠性指标,还可以对系统失效时各部件失效的条件概率进行求解,进而得到各个部件对系统的可靠性影响程度,进行正反推理诊断,找出受电弓系统可靠性的薄弱环节,提高了其可靠性分析的效率.为地铁车辆受电弓系统的可靠性评估及其故障检修提供理论依据.     

数控机床液压系统故障溯源及分析*

以提高机床液压系统可靠性为目的,分析了液压传动的特点,并对常见的故障现象进行了整理,归纳出了振动异响、压力不足及波动大、流量不稳定、液压元器件损坏四种典型的故障模式。以某磨齿机为例,采用FTA(故障树分析)方法,对四种故障模式进行了故障原因溯源,找出了造成系统故障的根本原因。以压力故障为例进行了定量分析,对每个底事件的概率重要度和相对概率重要度进行了计算,并阐述了重要度分析在可靠性改进和控制过程中的重要作用。     

基于模糊故障树的地铁综合监控系统可靠性分析

近年城市交通问题凸显,地铁作为解决城市交通问题的重要方式,其安全稳定运行显得尤为重要。地铁综合监控系统是整个地铁系统安全可靠运行的重要保障,对其可靠性进行有效的评估有着重要的价值。介绍了地铁综合监控系统和模糊故障树理论,运用模糊故障树对地铁综合监控系统可靠性进行分析,并对车站级监控系统的故障进行了定性和定量的可靠性分析,拓展了模糊故障树的使用领域。     

基于故障树最小割集的故障诊断方法研究

利用故障树分析原理，对基于故障树最小割集的诊断方法进行了研究。在给出故障树顶事件和底事件概率描述的基础上，计算了故障树最小割集的重要度，并在量级上进行了分析比较，为系统的故障源搜寻提供了具体有效的测试步骤。并给出了应用实例。     

基于DFTA的电牵引采煤机调高液压系统可靠性分析

MG950/1915型电牵引采煤机调高液压系统具有动态失效行为,用传统静态故障树法无法分析其可靠性.该文提出基于动态故障树的采煤机调高液压系统分析法,建立了油缸运动阻力大的动态故障树模型.首先求解动态故障树中不同子树的顶事件在不同时刻的发生概率,能得到整体动态故障树顶事件在不同时刻的发生概率.其次通过寻找顶事件发生概率最大的子树及子树中概率重要度最大的底事件,得到精过滤器和粗过滤器是采煤机调高液压系统的薄弱环节,为采煤机的优化设计提供了理论依据.     

基于蛛状网拓扑智能变电站“三层一网”通信系统研究

在110kV及以下电压等级变电站中,“三层一网”架构虽然简化了二次系统接线,但实时性和可靠性难以保证。针对传统拓扑结构下的实时性和可靠性无法同时达到最优效果的问题,本文采用“三层一网”架构下蛛状网拓扑结构,仿真结果表明该结构下的通信系统实时性最佳,解决了传统拓扑结构实时性差的问题,并结合算例验证了其可行性;运用故障树分析法定量分析不同结构的可靠性,结果表明蛛状网结构的可靠性更好。为解决研究复杂的通信系统可靠性时传统故障树方法有一定的局限性的问题,本文引入T-S模糊故障理论,建立T-S故障树模型,计算结果表明蛛状网结构下通信系统可靠性最好。根据本文研究可以得到蛛状网拓扑结构能同时提高通信系统实时性和可靠性的结论。     

Fuzzy dynamic fault tree analysis for electro-mechanical actuator based on algebraic model with common-cause failures

This paper deals with fuzzy dynamic fault tree analysis for the electro-mechanical actuator with common-cause failures to provide fast fault location strategy. To fully describe the level of uncertainty of basic events, triangle fuzzy set is used. Temporal operators are defined, algebraic model is used to model and analyze dynamic fault tree of the electro-mechanical actuator and is general to all kind of life distribution. An innovative common-cause gate with incomplete common-cause under consideration is raised and it can also match the algebraic model analysis method. Fuzzy probability importance is computed by level-progressive strategy, and complexity of solving entirely is avoided and calculation time is reduced. The analysis result shows that the method is flexible and effectively done with the reliability analysis of electro-mechanical actuator and can provide suggestions for faults location.     

A theory of independent fuzzy probability for system reliability

Fuzzy fault trees provide a powerful and computationally efficient technique for developing fuzzy probabilities based on independent inputs. The probability of any event that can be described in terms of a sequence of independent unions, intersections, and complements may be calculated by a fuzzy fault tree. Unfortunately, fuzzy fault trees do not provide a complete theory: many events of substantial practical interest cannot be described only by independent operations. Thus, the standard fuzzy extension (based on fuzzy fault trees) is not complete since not all events are assigned a fuzzy probability. Other complete extensions have been proposed, but these extensions are not consistent with the calculations from fuzzy fault trees. We propose a new extension of crisp probability theory. Our model is based on n independent inputs, each with a fuzzy probability. The elements of our sample space describe exactly which of the n input events did and did not occur. Our extension is complete since a fuzzy probability is assigned to every subset of the sample space. Our extension is also consistent with all calculations that can be arranged as a fault tree. Our approach allows the reliability analyst to develop complete and consistent fuzzy reliability models from existing crisp reliability models. This allows a comprehensive analysis of the system. Computational algorithms are provided both to extend existing models and develop new models. The technique is demonstrated on a reliability model of a three-stage industrial process     

Fault tree analysis with fuzzy gates

Fault tree analysis is an important tool analyzing system reliability. Fault trees consist of gates and events. Gates mean relationships between events. In fault tree analysis, AND, OR gates have been used as typical gates but it is often difficult to model the system structure with the two gates because in many cases we have not exact knowledge on system failure mechanism in early design stage. In this paper, we apply the fuzzy sets theory to modeling the fuzzy system structure, propose the new procedure to calculate the system reliability and a new importance index of basic events.     

Fuzzy fault tree analysis based on T–S model with application to INS/GPS navigation system

A novel fault tree analysis (FTA) technique based on the Takagi and Sugeno (T–S) model is proposed in this paper. In the proposed technique, referred to as the TS-FTA, the events in the conventional FTA can be expressed in terms of fuzzy possibilities, and the gates that represent the relations among the top event and the primary events are replaced by T–S fuzzy gates derived from the T–S model. The magnitudes of the faults in the system are expressed in term of fuzzy variables. Since the proposed TS-FTA is derived from fuzzy logic and the T–S model, it can readily handle fuzzy information and uncertainties in the relationships among events. Therefore, the TS-FTA is suitable for systems where exact information on the fault probabilities of the components and the failure mechanisms are not available. The proposed TS-FTA is applied to analyze the reliability of an Inertial Navigation System and Global Position System (INS/GPS) integrated navigation system.     

Application of non-normal p-norm trapezoidal fuzzy number in reliability evaluation of electrical substations

This paper presented a non-normal p-norm trapezoidal fuzzy number–based fault tree technique to obtain the reliability analysis for substations system. Due to uncertainty in the collected data, all the failure probabilities are represented by non-normal p-norm trapezoidal fuzzy number. In this paper, the fault tree incorporated with the non-normal p-norm trapezoidal fuzzy number and minimal cut sets approach are used for reliability assessment of substations. An example of 66/11 kV substation is given to demonstrate the method. Further, fuzzy risk analysis problems are described to find out the probability of failure of each components of the system using linguistic variables, which could be used for managerial decision making and future system maintenance strategy.     

基于模糊故障树的ILS接收机的故障诊断

仪表着陆系统是飞机导航系统的重要子系统,其可靠性直接关系到飞机能否安全运行。为了准确描述故障对仪表着陆系统功能的影响程度,文中基于对仪表着陆系统接收机故障概率的分析,将模糊数学和故障树方法相结合,以AIR-BUS 320仪表着陆系统接收机为例,详述了模糊故障树的建模过程,并通过对其进行失效分析,给出了仪表着陆系统接收机的故障诊断算法。仿真结果表明,所建立的模型满足仪表着陆系统对接收机的故障诊断要求,且建模方法具有广泛的适用性。