Automating the failure modes and effects analysis of safety critical systems

Abstract

Failure Modes and Effects Analysis (FMEA) is a classical system safety analysis technique which is currently widely used in the automotive, aerospace and other safety critical industries. In the process of an FMEA, analysts compile lists of component failure modes and try to infer the effects of those failure modes on the system. System models, typically simple engineering diagrams, assist analysts in understanding how the local effects of component failures propagate through complex architectures and ultimately cause hazardous effects at system level.Although there is software available that assists engineers in performing clerical tasks, such as forming tables and filling in data, the intelligent part of an FMEA process remains a manual and laborious process. Thus, one of the main criticisms of FMEA is that the time taken to perform the analysis can often exceed the period of the design and development phases and therefore the analysis de facto becomes a mere deliverable to the customer and not a useful tool capable of improving the design. Difficulties naturally become more acute as systems grow in scale and complexity.To address those difficulties, a body of work is looking into the automation and simplification of FMEA [1-3]. To mechanically infer the effects of component failures in a system, several approaches have been proposed which use domain specific qualitative or quantitative fault simulation. These approaches are restricted to particular application domains such as the design of electrical or electronic circuits. Limitations in scope but also difficulties with the efficiency and scalability of algorithms seem to have so far limited the industrial take-up of this automated FMEA technology which is still under development.In this paper we propose a new approach to the automatic synthesis of FMEAs which builds upon recent work towards automating fault tree analysis [4]. In this approach, FMEAs are built from engineering diagrams that have been augmented with information about component failures. The proposed approach is generic, i.e. not restricted to an application domain, and potentially applicable to a range of widely used engineering models. The models that provide the basis for the analysis identify the topology of the system, i.e. the system components and the material energy and data transactions among those components. Models can also be hierarchically structured and record in different layers the decomposition of subsystems into more basic components. We should note that this type of structural models include piping and instrumentation diagrams, data flow diagrams and other models commonly used in many areas of engineering design.The first step in the analysis of such models is the establishment of the local failure behaviour of components in the model as a set of failure expressions which show how output failures of each component can be caused by internal malfunctions and deviations of the component inputs. Once this local analysis has been completed for all components, the structure of the ...

A Comparative Study into Architecture-Based Safety Evaluation Methodologies Using AADL's Error Annex and Failure Propagation Models

“…Specifically, the methods based on the modular failure propagation models [16] are investigated, since these models form the conceptual foundation for AADL's Error Annex. [20,30], Fault Propagation&Transformation Calculus (FPTC) [48] as well as the HiP HOPS methodology [39,40,41]. Since this section can only describe each approach briefly, the interested reader should consult the original literature for a detailed description of each approach.…”

“…One weakness however of most architecture-based safety evaluation models is the inability to generate FMEA tables. Only HiP-HOPS provides the means to extract the necessary information of FMEA tables by analyzing minimal cutsets of the generated fault trees [41]. An adaption of this technique would be a good extension to the tool support of AADL's Error Annex and the existing failure propagation models.…”

“…As an example fault trees in Fault Tree+ format [27] can be generated and can be analyzed for minimal cut sets to identify critical points of failures. Furthermore, as presented in [41], Failure Modes and Effect Analysis tables can be generated based on an analysis of the minimal cut-sets. In practice, HiP-HOPS has been successfully applied to many complex realworld systems in companies such as Volvo [38] or Daimler Chrysler [40].…”

“…Such model-driven approaches (applied in the architecture design phase) are used to automatically produce Fault Trees and FMEA tables based on an architecture design specification annotated with information about the failure behavior of the architectural components. Example languages for these annotations are: Failure Propagation and Transformation Notation (FPTN) [12,13], Component Fault Trees (CFTs) [31], State Event Fault Trees (SEFTs) [20,30], Fault Propagation and Transformation Calculus (FPTC) [48] and the Tabular Failure Annotation of the HiP HOPS methodology [39,40,41]. Some of these architecture-based modeldriven safety evaluation techniques have been applied in industrial case studies (e.g.…”

Enhanced diagnosis of faults using the digraph approach applied to a dynamic aircraft fuel system

“…Attempts have been made to automate the FMEA process and increase its effectiveness through decreasing the time required for analysis. A different method proposes translating the information contained in a network of interconnected fault trees into FMEA-style tables [8]. Variability in the performance of these methods is noted with increased system complexity.…”