JP2018026052A - System failure analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system failure analysis method allowing an efficient system failure analysis.SOLUTION: In a system failure analysis method, an FMEA (Failure Mode and Effect Analysis) is applied to a whole system diagram expressing the whole system at an abstraction degree of a first level, and a failure mode for undergoing a detailed factor analysis is determined as an analysis object from failure modes obtained by the FMEA. Using the failure mode to be analyzed as a top event, a sub function included in the whole system diagram is detailed at an abstraction degree of a second level lower than the first level. The detailed factor analysis is executed by an FTA (Fault Tree Analysis).SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a system failure analysis method.

  For fault diagnosis of equipment and components, perform FTA (Fault Tree Analysis) by narrowing down the temporary generation of failure factors obtained by FMEA (Failure Mode and Effect Analysis) with reference to past cases A technique for reducing the target number of temporary verifications is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 07-271587

  However, in the conventional techniques as described above, when the scale of the system increases, the number of objects to be subjected to FTA becomes enormous and accordingly it is difficult to enable efficient system failure analysis.

  Therefore, according to one aspect, an object of the present invention is to enable efficient system failure analysis.

According to one aspect, FMEA is performed on the entire system diagram representing the entire system at a first level of abstraction,
Among failure modes obtained by performing the FMEA, a failure mode to be subjected to detailed factor analysis is determined,
Including the determined failure mode of the detailed factor analysis target as a top event, the sub-functions included in the overall system diagram are refined at a second level of abstraction lower than the first level, and FTA is performed. A system failure analysis method is provided.

  According to one aspect, efficient system failure analysis is possible.

It is explanatory drawing of step S1. It is explanatory drawing of step S1-2. It is explanatory drawing of step S1-3. It is explanatory drawing of step S2.

  Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

One embodiment of the system failure analysis method is performed as follows. The system failure analysis method described below may be realized, for example, by a user using software or tools on a computer, on paper, or a combination thereof.
Step S1: Perform FMEA on the overall system diagram with a high level of abstraction Step S1 includes the following sub-steps S1-1 to S1-3.
Step S1-1: Creation of a system overview with a high level of abstraction Step S1-2: Performing FMEA on a system overview with a high level of abstraction Step S1-3: Performing failure analysis using an exhaustive guide word S2: Perform detailed failure factor analysis Each step will be described below.

  FIG. 1 is an explanatory diagram of step S1 and illustrates an example of an overall system diagram with a high level of abstraction.

  In step S1, an overall system diagram with a high level of abstraction is generated. At this time, elements necessary for realizing the entire system are described without omission. However, abstract as simple as possible. FIG. 1 is an overall system diagram related to a safety system for preventing an accident caused by a driver's sudden start. The system 1 is a system that suppresses acceleration when a sudden start more than necessary is detected.

  FIG. 2 is an explanatory diagram of step S1-2, and illustrates an example of a control loop.

  In step S1-2, FMEA is performed on the entire system diagram. However, when FMEA is performed, the control loop L1 may be defined by extracting in advance only the sub-blocks that realize the specific function from the overall system diagram. That is, a control loop L1 in which functional elements necessary for realizing the specific control of the system 1 are selected in the overall system diagram may be defined. In this case, FMEA may be performed only for the range related to the control loop L1 in the overall system diagram. Further, when a plurality of control loops L1 are defined, FMEA may be sequentially performed only on each range related to the control loop L1 in the overall system diagram. FIG. 2 shows an example in which only the sub-functions necessary for realizing the function of “suppressing driving force” are extracted in the same system as the system shown in FIG. If the sub-function on the control loop L1 functions normally, the function of “suppressing driving force” is realized.

  FIG. 3 is an explanatory diagram of step S1-3, and is a table showing an example of an exhaustive guide word.

  In step S1-3, how to break (failure mode) is analyzed using an exhaustive guide word. For example, what happens in the control related to the control loop L1 defined in step S1-2 is analyzed. FIG. 3 shows an example of the result of analyzing what happens to the entire system 1 by applying a guide word to the output of one “control determination” subfunction on the control loop L1.

  FIG. 4 is an explanatory diagram of step S2 and is a diagram illustrating an example of sub-function blocks detailed for failure factor detailed analysis.

  In step S2, among the breaking methods identified in step S1, the failure factor is analyzed in detail for “the breaking method in question (for example, the critical or fatal breaking method for the system). Perform FTA from failure to component failure, narrow down the range required for detailed analysis, refine the function, and analyze the cause of the “breaking problem” as the top event. The refinement is preferably at a level at which fail-safe design can be incorporated, and the refinement may be realized by using a tool such as Simulink (registered trademark), for example, in FIG. An example in which a detailed failure factor analysis that leads to “cannot suppress driving force”, which is an example of “how to break” is shown is shown in step S1-1. When the “control judgment” sub-function block included in the overall system diagram with a high level of abstraction is detailed, the output becomes “cannot suppress driving force” (that is, the output 1 of the detailed diagram is “TRUE”). An example is shown in which the cause analysis of “Continuing” and Output 2 “Continuing“ FALSE ”is performed. In this case, the input 3 flag is always set as shown by the dotted line in FIG. It can be seen that a failure that turns off and a failure in which each of the inputs branched from input 2 to 4 always becomes “TRUE”, “TRUE”, “FALSE”, and “FALSE” in order from the top.

  By the way, an integrated system such as preventive safety has a feature realized by cooperation of many sub-functions and parts. Accordingly, the scale is increased, and the related functions and related parts are diversified. As a result, in the conventional failure analysis method, there is a problem that necessary man-hours are diverged.

  In this respect, according to the present invention, as described above, after ensuring completeness in a high level of abstraction, the critical breakage for the system is identified, and then the refinement is focused on the critical breakage. Perform detailed failure factor analysis. Therefore, according to the present invention, even if a large-scale system is a target, efficient analysis can be realized without increasing the number of failure analysis steps in proportion to the scale.

  Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes can be made within the scope described in the claims. It is also possible to combine all or a plurality of the components of the above-described embodiments.

  L1 control loop

Claims (1)

FMEA is performed on the entire system diagram that represents the entire system at the first level of abstraction,
Among failure modes obtained by performing the FMEA, a failure mode to be subjected to detailed factor analysis is determined,
Including the determined failure mode of the detailed factor analysis target as a top event, the sub-functions included in the overall system diagram are refined at a second level of abstraction lower than the first level, and FTA is performed. System failure analysis method.

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