Fault diagnosis system design method fusing fault equation and IPMI sensor

Abstract

The invention belongs to the field of airborne computer software, relates to an aircraft fault diagnosis and health management technology, and discloses a fault diagnosis system design method fusing a fault equation and an IPMI sensor, and the design method comprises the steps: distributing an original IPMI sensor for each piece of monitoring data, and designing a fault variable and an original fault equation for each original IPMI sensor; fusing a plurality of original fault equations with the incidence relation according to a known fault type to obtain fused fault equations, and distributing a fused IPMI sensor for each fused fault equation; compiling an sdr-format sensor description file and a bin-format fault equation model file; and writing a fault diagnosis system operation program, and loading the fault diagnosis system operation program to the recording computer for fault diagnosis. According to the design method, the fault diagnosis process has a logical operation function and an event processing function, and a diagnosis result can be obtained by completing complex logical operation.

Description

Technical Field

[0001] The present invention belongs to the field of airborne computer software, relates to aircraft fault diagnosis and health management technology, and specifically relates to a fault diagnosis system design method integrating fault equations and IPMI sensors. Background Art

[0002] Aircraft fault diagnosis and health management (PHM) technology is a major component of airborne computer maintenance. With the continuous development of PHM technology, the importance of normalization and standardization has become increasingly prominent. The Intelligent Platform Management Interface (IPMI) standard has been increasingly used in PHM.

[0003] The IPMI system defines a set of intelligent platform management system architecture, which regards all data sources in the system as sensors, and implements data collection, fault detection, fault reporting, fault recording, fault response and other functions based on sensors. However, because IPMI does not have complex logical operation functions, it can only perform simple judgments such as "whether the value of a certain sensor exceeds the threshold", and cannot integrate the judgment results of multiple sensors to generate higher-level logical judgments, and thus it is difficult to meet the increasingly complex PHM system's demand for fault handling functions.

[0004] The fault equation is an important part of PHM. It can calculate simple fault judgment results according to predetermined logic to obtain higher-level and more complex logical judgment results, which can support the PHM system to execute more complex response logic. However, since the fault equation system only has logical operation functions, it cannot process the results obtained by logical operation.

[0005] In view of this, it is necessary to design a fault diagnosis method suitable for IPMI sensors. Summary of the invention

[0006] In order to solve the technical problems in the prior art that the IPMI sensor does not have a logic operation function and the fault equation does not have the ability to further process the result of the logic operation, the present invention discloses a fault diagnosis system design method integrating the fault equation and the IPMI sensor, the method comprising the following steps:

[0007] S1. Assign an original IPMI sensor to each monitoring data, and design a fault variable and an original fault equation for each original IPMI sensor;

[0008] S2. According to a known fault type, the original fault equations of the plurality of monitoring data having an associated relationship are fused to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation;

[0009] S3, compile an sdr format sensor description file and a bin format fault equation model file through the information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor and the fused fault equation;

[0010] S4. Compile a fault diagnosis system operating program according to the sdr format sensor description file and the bin format fault equation model file, and load the fault diagnosis system operating program onto an onboard computer for fault diagnosis.

[0011] Furthermore, in step S1, an original IPMI sensor is assigned to each monitoring data, and a fault variable and an original fault equation are designed for each original IPMI sensor, including:

[0012] S11, assigning an original IPMI sensor to each of the monitoring data, and setting basic attributes and fault judgment attributes for each of the original IPMI sensors according to the type of the monitoring data;

[0013] S12, setting a fault variable for each of the original IPMI sensors according to the monitoring data and the fault judgment attribute;

[0014] S13. Designing a logic operation to obtain an original fault equation according to the fault variable of each original IPMI sensor.

[0015] Furthermore, in step S11, the basic attributes include sensor number, name, sensor type, type of data to be monitored and event trigger switch, and the fault judgment attributes include threshold values, hysteresis values, conversion factors, units corresponding to analog type monitoring data and reference values ​​corresponding to discrete type monitoring data.

[0016] Further, in step S2, the original fault equations of the plurality of monitoring data having an associated relationship are fused according to the known fault type to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation, including:

[0017] S21, analyzing the known fault types to obtain a plurality of monitoring data having associated relationships;

[0018] S22, performing logical operations on the plurality of original fault equations according to the association relationship of the plurality of monitoring data in the known fault type to design a fused fault equation expression, and obtaining a fused fault equation;

[0019] S23: Allocate a fused IPMI sensor to each of the fused fault equations.

[0020] Further, in step S3, the sdr format sensor description file and the bin format fault equation model file are written by using the information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor and the fused fault equation, including:

[0021] S31, compiling a sensor description file in XML format through the information of each original IPMI sensor and the corresponding fault variable information, and the information of each fused IPMI sensor;

[0022] S32, compiling a fault equation model file in XML format through the information of each original fault equation and the information of each fused fault equation;

[0023] S33, converting the XML format sensor description file into an sdr format sensor description file, and converting the XML format fault equation model file into a bin format fault equation model file.

[0024] Furthermore, the fault diagnosis includes:

[0025] Performing fault diagnosis on the corresponding monitoring data collected by each of the original IPMI sensors, and outputting a fault diagnosis result;

[0026] By performing a logical operation on the corresponding plurality of monitoring data with associated relationships through each fused fault equation, a fault diagnosis result of the corresponding known fault type is obtained.

[0027] An embodiment of the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the computer device implements any of the above-mentioned methods for designing a fault diagnosis system integrating a fault equation and an IPMI sensor, so as to solve the technical problems in the prior art that the IPMI sensor does not have a logic operation function, and the fault equation does not have the ability to further process the results of the logic operation.

[0028] An embodiment of the present invention also provides a computer-readable storage medium, which stores a computer program for executing any of the above-mentioned methods for designing a fault diagnosis system that integrates fault equations and IPMI sensors, so as to solve the technical problems in the prior art that IPMI sensors do not have a logic operation function, and that fault equations do not have the ability to further process logic operation results.

[0029] Compared with the prior art, the beneficial effects achieved by at least one of the above technical solutions adopted in the embodiments of this specification include at least: the fault diagnosis system design method designed by the present invention obtains multiple associated monitoring data according to the known fault type, uses the results of the fault equations generated by the sensors in the corresponding multiple original IPMIs as the input of the fused fault equation, and performs logical operations in the fused fault equation to obtain the fault results of each known fault type. The fault diagnosis system designed by the method of the present invention can make up for the disadvantage that the traditional IPMI system does not have the logical operation function. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A flowchart of a method for designing a fault diagnosis system integrating fault equations and IPMI sensors disclosed in an embodiment of the present invention;

[0032] Figure 2 This is an architecture diagram of a fault diagnosis system disclosed in an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of a description file disclosed in an embodiment of the present invention;

[0034] Figure 4 The description file generation process disclosed in the embodiment of the present invention;

[0035] Figure 5 A flowchart of the IPMI sensor data acquisition program disclosed in an embodiment of the present invention;

[0036] Figure 6 The present invention discloses a fault diagnosis program processing flow through a fault diagnosis system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0038] The following describes the implementation methods of the present application through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and the features of the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0039] The embodiment of the present invention discloses a fault diagnosis system design method integrating fault equations and IPMI sensors, see Figure 1 and Figure 2 As shown, the method comprises the following steps:

[0040] S1. Assign an original IPMI sensor to each monitoring data, and design a fault variable and an original fault equation for each original IPMI sensor;

[0041] S2. According to a known fault type, the original fault equations of the plurality of monitoring data having an associated relationship are fused to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation;

[0042] S3, compile an sdr format sensor description file and a bin format fault equation model file through the information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor and the fused fault equation;

[0043] S4. Compile a fault diagnosis system operating program according to the sdr format sensor description file and the bin format fault equation model file, and load the fault diagnosis system operating program onto an onboard computer for fault diagnosis.

[0044] Furthermore, in step S1, an original IPMI sensor is assigned to each monitoring data, and a fault variable and an original fault equation are designed for each original IPMI sensor, including:

[0045] S11, assigning an original IPMI sensor to each of the monitoring data, and setting basic attributes and fault judgment attributes for each of the original IPMI sensors according to the type of the monitoring data;

[0046] S12, setting a fault variable for each of the original IPMI sensors according to the monitoring data and the fault judgment attribute;

[0047] S13. Designing a logic operation to obtain an original fault equation according to the fault variable of each original IPMI sensor.

[0048] Furthermore, in step S11, the basic attributes include sensor number, name, sensor type, type of data to be monitored and event trigger switch, and the fault judgment attributes include threshold values, hysteresis values, conversion factors, units corresponding to analog type monitoring data and reference values ​​corresponding to discrete type monitoring data.

[0049] Further, in step S2, the original fault equations of the plurality of monitoring data having an associated relationship are fused according to the known fault type to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation, including:

[0050] S21, analyzing the known fault types to obtain a plurality of monitoring data having associated relationships;

[0051] S22, performing logical operations on the plurality of original fault equations according to the association relationship of the plurality of monitoring data in the known fault type to design a fused fault equation expression, and obtaining a fused fault equation;

[0052] S23: Allocate a fused IPMI sensor to each of the fused fault equations.

[0053] In specific implementation, in steps S1 and S2, the design process of the original IPMI sensor, the original fault equation, the fused fault equation, and the fused IPMI sensor is as follows:

[0054] Step 1.1, design the original IPMI sensor (such as Figure 2 IPMI sensor 1, IPMI sensor 2, IPMI sensor 3 shown in ). For the monitoring data in the intelligent platform management system, including discrete data or analog data, an original IPMI sensor is set for each monitoring data, and the basic attributes such as number, name, sensor type, data type, event trigger switch, etc. are set according to the IPMI standard. If it is an analog sensor, it is also necessary to set the threshold, hysteresis value, conversion factor, unit and other proprietary attributes. If it is a discrete sensor, it is also necessary to set the reference value and other proprietary attributes. The proprietary attributes are also the fault judgment attributes. The user can set a specific value for each attribute, and compare the collected monitoring data with the value of the set proprietary attribute to obtain the fault result of the device corresponding to the monitoring data.

[0055] Step 1.2: Set one or more fault variables for each original IPMI sensor according to user requirements. Each fault variable may correspond to a different original IPMI sensor and a different sensor event.

[0056] The original IPMI sensor with different fault variables and sensor events can trigger one or more events. One or more fault variables are set to correspond to the events that can be triggered by the original IPMI sensor. Each fault variable can correspond to one or more original IPMI sensor events, and the events that can be triggered by a certain sensor are known.

[0057] For a fault variable, when the original IPMI sensor does not trigger the corresponding event, the value of the fault variable is 0, indicating no fault; when the original IPMI sensor triggers the corresponding event, the value of the fault variable is 1, indicating a fault. The information that needs to be set for each fault variable includes the fault variable name, the corresponding original IPMI sensor name, and the corresponding sensor event.

[0058] Step 1.3, designing an original fault equation for each original IPMI sensor according to the fault variables; based on all the fault variables, designing an original fault equation for each original IPMI sensor.

[0059] The information that needs to be set for the original fault equation includes the fault equation name (such as Figure 2 The fault equation name A, fault equation name B, fault equation name C), fault equation length, and fault equation expression are shown in FIG. Among them, the fault equation expression is an expression that describes which fault variables are used to obtain the value of the fault equation through what kind of AND or NOT logic operation. The specific logic of the fault equation depends on the specific needs of the actual project, that is, the user needs.

[0060] Step 1.4: Obtain all original fault equations with associated relationships for known fault types, and design fused fault equations (e.g. Figure 2 Fault equation D, fault equation E) shown in , given each fused fault equation a fused IPMI sensor (e.g. Figure 2 IPMI sensor X, IPMI sensor Y) as shown in .

[0061] According to user needs, a fusion IPMI sensor is set for each fusion fault equation, and the fusion IPMI sensor outputs the result (ie, whether there is a fault) after the fusion fault equation is logically operated.

[0062] In the embodiment of the present invention, for each fault equation (including the original fault equation and the fused fault equation) whose result needs to be reported, recorded, and responded, an IPMI sensor (including the original IPMI sensor and the fused IPMI sensor) is set for it, so that it can realize the reporting, recording, and response of the fault equation result through the IPMI system. It should be noted that the data type of the IPMI sensor corresponding to the fault equation is a discrete quantity, the value is equal to the result of the fault equation, the name of the sensor is the same as the name of the fault equation, and the sensor type is a custom type.

[0063] Further, see Figure 3 As shown, in step S3, the sdr format sensor description file and the bin format fault equation model file are written through the information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor and the fused fault equation, including:

[0064] S31, compiling a sensor description file in XML format through the information of each original IPMI sensor and the corresponding fault variable information, and the information of each fused IPMI sensor;

[0065] S32, compiling a fault equation model file in XML format through the information of each original fault equation and the information of each fused fault equation;

[0066] S33, converting the XML format sensor description file into an sdr format sensor description file, and converting the XML format fault equation model file into a bin format fault equation model file.

[0067] In the specific implementation, see Figure 4 As shown, in step S3, the writing process of the sdr format sensor description file and the bin format fault equation model file is as follows:

[0068] Step 2.1, write the designed original IPMI sensor, fault variable and original fault equation, fused IPMI sensor and fused fault equation into a description file and model file in XML format. The file consists of three parts: information of the original IPMI sensor, information of the fault variable, information of the original fault equation, information of the fused IPMI sensor, and information of the fused fault equation. Since the information of the IPMI sensor corresponding to the fault equation is completely determined by the fault equation, it can be omitted in the description file. The information of the IPMI sensor (including the original IPMI sensor and the fused IPMI sensor) is all the information of each IPMI sensor except the sensor number. The fault variable information, that is, all the information of each fault variable, includes the variable name, the sensor name corresponding to the original IPMI sensor, and the corresponding event. The corresponding event is when the corresponding original IPMI sensor triggers which events, the value of the fault variable becomes 1. The information of the fault equation (including the original fault equation and the fused fault equation) includes the fault name, the length of the fault equation, whether the fault equation needs to set the corresponding IPMI sensor, and the fault equation expression.

[0069] Step 2.2, write a generation program to generate model files in sdr format and bin format respectively from the sensor description file in XML format and the fault equation model file. The generation process is as follows: Figure 3 As shown. The program reads the sensor description file and fault equation model file in XML format, and generates the sensor description file in SDR format and the fault equation model file in bin format respectively. First, the program reads the XML file and parses it; then, the program traverses all fault equations, sets an IPMI sensor for each fault equation that needs to set an IPMI sensor, and appends it to the existing IPMI sensor; then, the program assigns numbers to each IPMI sensor, fault variable, and fault equation respectively; then, the program replaces the sensor name of the IPMI sensor corresponding to the fault variable with the sensor number, and replaces the fault variable name in the expression of the fault equation with the fault variable number; then, the program generates the sensor description file in SDR format according to the IPMI standard; finally, the program generates the fault equation model file in the format required by the fault equation system, including the information of all fault variables and fault equations. The written XML format description file is input into the generation program described in step X to generate the sensor description file in SDR format and the fault equation model file in bin format.

[0070] In specific implementation, the fault diagnosis system is an IPMI sensor system that complies with the IPMI standard, and has functions such as sensor fault detection, event generation, event reporting, event recording, and event response. The fault equation system has functions such as fault expression calculation and fault equation update. The process of writing and loading the fault diagnosis system running program to the recording computer in step S4 includes:

[0071] Step 3.1: Figure 5 As shown, write an IPMI sensor data acquisition function. The IPMI sensor data acquisition function is a function used by the IPMI sensor to update its own value. According to the number and type of the IPMI sensor, the latest data is obtained from the data source corresponding to the IPMI sensor to update the sensor value. The input of this function is the sensor number, and the return value is the latest value of the sensor. First, the program finds the description information of the sensor from the sdr format file according to the sensor number and obtains the type of the sensor; then, it determines whether the type of the sensor is a custom type. If it is a custom type, it means that the sensor is a sensor corresponding to the fault equation. The program finds the corresponding fault equation number from the sensor description information, and finds the latest value of the corresponding fault equation according to the fault equation number and returns it; if the sensor type is not a custom type, it means that the sensor is an original IPMI sensor, and the data can be obtained according to the method of the original IPMI sensor system.

[0072] Step 3.2, write a fault variable data acquisition function. The fault variable data acquisition function is a function used by the fault variable to update its own value. The latest value of the fault variable is obtained according to the sensor number corresponding to the fault variable and the corresponding sensor event. The input of this function is the fault variable number, and the return value is the latest value of the fault variable corresponding to the number.

[0073] Step 3.3: Build a complete fault diagnosis system running program integrating fault equations.

[0074] Step 3.4: Deploy the fault diagnosis system running program to the onboard computer. First, integrate the IPMI sensor system program integrating the fault equation into the onboard computer software; then, burn the sensor description file in sdr format and the fault equation model file in bin format to the onboard computer to complete the deployment of the IPMI sensor system integrating the fault equation.

[0075] See also Figure 6 As shown, the fault diagnosis is performed by running a program on the fault diagnosis system on the onboard computer, including:

[0076] Performing fault diagnosis on the corresponding monitoring data collected by each of the original IPMI sensors, and outputting a fault diagnosis result;

[0077] By performing a logical operation on the corresponding plurality of monitoring data with associated relationships through each fused fault equation, a fault diagnosis result of the corresponding known fault type is obtained.

[0078] The fault diagnosis system design method designed by the present invention obtains multiple related monitoring data according to known fault types, uses the results of the fault equations generated by the sensors in the corresponding multiple original IPMIs as the input of the fused fault equation, and performs logical operations in the fused fault equation to obtain the fault results of each known fault type. The fault diagnosis system designed by the method of the present invention can make up for the disadvantage that the traditional IPMI system does not have a logical operation function.

[0079] In this embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, any of the above-mentioned methods for designing a fault diagnosis system integrating fault equations and IPMI sensors is implemented.

[0080] Specifically, the computer device may be a computer terminal, a server or a similar computing device.

[0081] In this embodiment, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program for executing any of the above-mentioned methods for designing a fault diagnosis system integrating fault equations and IPMI sensors.

[0082] Specifically, computer-readable storage media include permanent and non-permanent, removable and non-removable media that can be used to store information by any method or technology. Information can be computer-readable instructions, data structures, program modules or other data. Examples of computer-readable storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable storage media does not include temporary computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0083] Obviously, those skilled in the art should understand that the modules or steps of the above-mentioned embodiments of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order from that here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. In this way, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fault diagnosis system design method integrating fault equations and IPMI sensors, characterized in that: include: Allocating an original IPMI sensor to each monitoring data, and designing a fault variable and an original fault equation for each original IPMI sensor; According to the known fault type, the original fault equations of the plurality of monitoring data having an associated relationship are fused to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation; Compile an sdr format sensor description file and a bin format fault equation model file through the information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor, and the fused fault equation; A fault diagnosis system operating program is written according to the sdr format sensor description file and the bin format fault equation model file, and the fault diagnosis system operating program is loaded onto an onboard computer for fault diagnosis.

2. The method for designing a fault diagnosis system integrating fault equations and IPMI sensors according to claim 1, characterized in that: Assign an original IPMI sensor to each monitoring data, and design a fault variable and an original fault equation for each original IPMI sensor, including: Allocating an original IPMI sensor to each of the monitoring data, and setting basic attributes and fault judgment attributes for each of the original IPMI sensors according to the type of the monitoring data; According to the monitoring data and the fault judgment attribute, setting a fault variable for each of the original IPMI sensors; According to the fault variable of each of the original IPMI sensors, a logical operation is designed to obtain an original fault equation.

3. The method for designing a fault diagnosis system integrating fault equations and IPMI sensors according to claim 2, characterized in that: The basic attributes include sensor number, name, sensor type, type of data to be monitored and event trigger switch, and the fault judgment attributes include threshold value, hysteresis value, conversion factor, unit corresponding to analog type monitoring data and reference value corresponding to discrete type monitoring data.

4. The method for designing a fault diagnosis system integrating fault equations and IPMI sensors according to claim 1, characterized in that: According to the known fault type, the original fault equations of the plurality of monitoring data having an associated relationship are fused to obtain a fused fault equation, and a fused IPMI sensor is allocated to each fused fault equation, including: Analyze the known fault types to obtain a plurality of monitoring data with associated relationships; According to the association relationship between the plurality of monitoring data in the known fault type, a logical operation is performed on the plurality of original fault equations to design a fused fault equation expression, thereby obtaining a fused fault equation; A fused IPMI sensor is assigned to each of the fused fault equations.

5. The method for designing a fault diagnosis system integrating fault equations and IPMI sensors according to claim 1, characterized in that: Writing an sdr format sensor description file and a bin format fault equation model file through information of the original IPMI sensor, the fault variable, the original fault equation of the fused IPMI sensor, and the fused fault equation includes: Compile a sensor description file in XML format using the information of each original IPMI sensor and the information of the corresponding fault variable, and the information of each fused IPMI sensor; Compile a fault equation model file in XML format using the information of each original fault equation and the information of each fused fault equation; The XML format sensor description file is converted into an sdr format sensor description file, and the XML format fault equation model file is converted into a bin format fault equation model file.

6. The method for designing a fault diagnosis system integrating fault equations and IPMI sensors according to claim 1, characterized in that: The fault diagnosis includes: Performing fault diagnosis on the corresponding monitoring data collected by each of the original IPMI sensors, and outputting a fault diagnosis result; By performing a logical operation on the corresponding plurality of monitoring data with associated relationships through each fused fault equation, a fault diagnosis result of the corresponding known fault type is obtained.

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