HIERARCHICAL FAULT DIAGNOSIS AND PROGNOSIS OF A SYSTEM

Abstract

A method for diagnosing a fault mode in a system includes recording a hierarchical precedence rule assigning a priority level to fault modes of the system, and recording, in a fault report matrix, fault reports indicative of a corresponding one or more of the fault modes. The method also includes using the hierarchical precedence rule to determine the assigned relative priority level for the fault reports in response to a predetermined condition, e.g., a requested engine starting event, and identifying a root cause subsystem as a subsystem having the highest assigned priority level. A control action executed via the controller identifies the root cause subsystem by recording a diagnostic code and/or transmitting a message. The system is also disclosed, as is a computer-readable medium programmed with instructions embodying the method.

Claims

1. A method for diagnosing a fault mode in a system, the method comprising: recording, in memory of a controller, a hierarchical precedence rule that assigns a relative priority level to a plurality of fault modes of the system; recording, in a fault report matrix in the memory of the controller, one or more fault reports indicative of a corresponding one of the fault modes; using the hierarchical precedence rule to determine the assigned relative priority level for the one or more fault reports via the controller in response to a predetermined condition; identifying a root cause subsystem of the system as a subsystem having the highest of the assigned priority levels; and executing a control action with respect to the system via the controller responsive to the identified root cause subsystem, including at least one of recording a diagnostic code and transmitting a message, each being indicative of the identified root cause subsystem.

2. The method of claim 1, wherein recording one or more fault reports includes recording an embedded fault report from an electronic control unit of a corresponding one or more of the subsystems.

3. The method of claim 1, wherein recording one or more fault reports includes recording a component fault report identifying a detected fault of the one or more subsystems.

4. The method of claim 1, wherein the predetermined event is an ignition cycle or a key cycle initiating operation of the system.

5. The method of claim 4, wherein the system is an engine starting system in a vehicle having an internal combustion engine.

6. The method of claim 5, wherein the subsystems include an auxiliary battery, a starter motor, a starter solenoid, an alternator, and a fuel delivery system.

7. A system comprising: a plurality of subsystems, at least one of which includes an electronic control unit operable for outputting an embedded fault report indicative of a fault mode of a corresponding one or more of the plurality of subsystems; and a controller in communication with the plurality of subsystems, wherein the controller is programmed with a hierarchical precedence rule that assigns a relative priority level to a plurality of fault modes of the system, and is configured to diagnose a fault mode of the system by: recording, in a fault report matrix, one or more fault reports indicative of a corresponding one of the fault modes; using the hierarchical precedence rule to determine the assigned relative priority level for the one or more fault reports via the controller in response to a predetermined condition; identifying a root cause subsystem of the system as a subsystem having the highest of the assigned priority levels; and executing a control action with respect to the system via the controller responsive to the identified root cause subsystem, including at least one of recording a diagnostic code and transmitting a message, each being indicative of the identified root cause subsystem.

8. The system of claim 7, wherein the one or more fault reports includes an embedded fault report from the electronic control unit.

9. The system of claim 7, wherein the fault reports include a component fault report identifying a detected fault mode of one of the subsystems.

10. The system of claim 7, wherein the predetermined event is an ignition cycle or a key cycle initiating operation of the system.

11. The system of claim 10, wherein the system is an engine starting system in a vehicle having an internal combustion engine.

12. The system of claim 11, wherein the subsystems include an auxiliary battery, a starter motor, a starter solenoid, an alternator, and a fuel delivery system.

13. A computer-readable medium on which is recorded a hierarchical precedence rule that assigns a relative priority level to a plurality of fault modes of a system and diagnostic instructions, the execution of which by a controller causes the controller to: record, in a fault report matrix, one or more fault reports indicative of a corresponding one or more of the fault modes; use the hierarchical precedence rule to determine the assigned relative priority level for the one or more fault reports via the controller in response to a predetermined condition; identify a root cause subsystem of the system as a subsystem having the highest of the assigned priority levels; and execute a control action with respect to the system via the controller responsive to the identified root cause subsystem, including at least one of recording a diagnostic code and transmitting a message, each being indicative of the identified root cause subsystem.

14. The computer-readable medium of claim 13, wherein the fault reports include an embedded fault report from an electronic control unit of a corresponding subsystem.

15. The computer-readable medium of claim 13, wherein the fault reports include a component fault report identifying a detected fault of one or more of the subsystems.

16. The computer-readable medium of claim 13, wherein the predetermined event is an ignition cycle or a key cycle initiating operation of the system.

17. The computer-readable medium of claim 16, wherein the system is an engine starting system in a vehicle having an internal combustion engine.

18. The computer-readable medium of claim 17, wherein the subsystems include an auxiliary battery, a starter motor, a starter solenoid, an alternator, and a fuel delivery system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a simplified schematic illustration of a vehicle and a controller programmed to execute a method for diagnosing and evaluating an example engine starting system.

[0014] FIG. 2 is a representative fault report matrix that may be populated and used as part of the present method.

[0015] FIG. 3 is a sample graphical illustration of an application of hierarchical precedence within the fault report matrix of FIG. 2.

[0016] FIG. 4 is a flow chart describing an embodiment of a method for diagnosing and evaluating the engine starting system shown in FIG. 1.

DETAILED DESCRIPTION

[0017] Referring to the drawings, wherein like reference numbers refer to like components, a vehicle 10 is depicted in FIG. 1 as a non-limiting example embodiment of a top-level system having multiple interrelated subsystems. The vehicle 10 is used hereinafter to illustrate a non-limiting type of system that lends itself to the beneficial use of a hierarchical and holistic diagnostic method 100, an example of which is depicted in FIG. 4 and explained below. The method 100 may also be readily applied to non-vehicular systems and subsystems other than those described herein. For illustrative clarity and consistency, the vehicle 10 of FIG. 1 will be described hereinafter in the context of an engine starting system 28 without limiting applications of the method 100 to systems in the form of the vehicle 10 or the engine starting system 28.

[0018] The vehicle 10 includes an internal combustion engine (E) 12 that is coupled to a transmission (T) 14, with the latter having internal gear sets, rotating and/or braking clutches, and interconnecting members (not shown). The engine 12 may include an input member 13 and an output member 15. The output member 15 may be coupled to an input member 17 of the transmission 14 via a clutch device C1, e.g., a hydrodynamic torque converter assembly or a friction clutch. Engine torque (arrow T.sub.E) is transferred via operation of the clutch device C1 from the output member 15 of the engine 12 to the input member 17 of the transmission 14. In turn, input torque (arrow T.sub.I) is transferred from the input member 17, through the transmission 14, and to an output member 19 of the transmission 14, with output torque (arrow T.sub.O) from the transmission 14 ultimately powering drive wheels 22 of the vehicle 10 via one or more drive axles 21.

[0019] The engine 12 is selectively cranked and started via the engine starting system 28, which is used herein for illustrative purposes as an example system to which the method 100 is applied. Specifically, the engine starting system 28 may include an auxiliary battery (B) 18 that, in a simplified illustrative embodiment, is electrically connected to a starter solenoid (S) 24 via a starter switch (SS), e.g., a key-operated or button-activated switch. The starter solenoid 24, when energized by the auxiliary battery 18 when the starter switch (SS) is closed, engages a starter motor (M.sub.S) 25. The energized starter motor 25 in turn translates a pinion gear 23 into direct meshed engagement with an engine flywheel 16, the resultant rotation of which delivers a cranking torque (arrow T.sub.C) to the input member 13 of the engine 12.

[0020] A fuel delivery system 30, which may be considered as a part of the engine starting system 28 in certain embodiments, may include a fuel pump (P.sub.F) 32 and a fuel injector rail 34. When the input member 13 is cranked to a threshold rotational speed, combustible fuel (arrow F) is fed via the fuel pump 32 to the fuel injector rail 34. The engine starting function is discontinued when the threshold speed is attained, with the internal combustion process of the engine 12 thereafter sustaining rotation. Additionally, the rotating engine 12 may power an alternator (A) 11 to generate and deliver electricity to the battery 18. As is known in the art, such an alternator 11 includes a belt (not shown) or other drive element that rotates in conjunction with rotation of the engine 12 to generate electricity.

[0021] As part of the vehicle 10, a controller (C) 50 may be equipped with requisite memory (M) and a processor (P), as well as associated hardware and software such as an oscillator, input/output circuitry, etc. The memory (M) may include a computer-readable medium or media, including sufficient amount of read only memory, for instance magnetic or optical memory, on which is recorded computer-readable diagnostic instructions embodying executable portions of the method 100 described below. In some embodiments, a hierarchical precedence rule 60 assigning a relative priority level to fault modes of a given system, e.g., the engine starting system 28, is recorded in memory (M), with execution by the processor (P) of the diagnostic instructions embodying the method 100 causing the controller 50 to perform the various aspects of the method 100 as set forth below in FIG. 4.

[0022] Additionally as part of the method 100, the controller 50 receives input signals (arrow CC.sub.I) from multiple components, subsystems, and/or electronic control units of the vehicle 10. After executing the method 100 using a fault report matrix 40 and a hierarchical precedence rule 60, the controller 50 transmits output signals (arrow CC.sub.O) to an output device 33, e.g., a display screen, a cell phone, or an external/web-based server, such as a vehicle telematics system.

[0023] Examples of the fault report matrix 40 and the hierarchical precedence rule 60 are depicted in FIGS. 2 and 3, respectively. As part of the method 100, a particular system is first divided into constituent subsystems within the fault report matrix 40 of FIG. 2. Using the engine starting system 28 of FIG. 1 as an example, embedded systems (column ES) provide various embedded fault reports. As used herein, embedded fault report refers to a fault report that is automatically generated by a corresponding electronic control unit (ECU) for and/or logic of a given subsystem. Subsystem fault report refers to a report generated by a health management module, a body control module, engine control module, etc., which may include the controller 50 or other control devices in different embodiments, and which may involve sensor-based fault detection or ongoing subsystem-level state of health determination. For instance, in the vehicle 10 shown in FIG. 1, embedded fault reports and/or subsystem fault reports may pertain to functional diagnosis and prognosis of the starting system, including the battery 18, the starter solenoid 24, the starter motor 25, the alternator 11, and/or a critical component of the fuel delivery system 30 such as the fuel pump 32.

[0024] Embedded fault reports provide information on the status of the engine starting process. In the example of FIG. 2, the embedded system (ES) reports may include a first set of embedded faults (F.sub.1), such as no crank request, no fault report, or ECU short to ground. A second set of embedded faults (F.sub.2) may describe a starter disabled condition, which may be further divided into no engine rotation (F.sub.2A), long injection delay (F.sub.2B), and maximum cranking time expired (Fac). A third set of embedded faults (F.sub.3) may include start and stall/engine shutdown during starting.

[0025] In addition to the embedded system fault reports, the fault report matrix 40 delineates possible root cause subsystems. In the example engine starting system 28, this may include the starter system 28 with the battery (B) 18, a charging system (CS) such as the alternator 11 and associated electrical sensors and connections, driver behavior (DB), multiple crank events (MCE) by numeric count, the fuel delivery system 30, and the engine (E) 12.

[0026] For each of the possible root cause systems, the fault report matrix 40 may identify specific fault modes. The battery 18 may exhibit a low state of charge (SOC.sub.L), a low state of health (SOH.sub.L), or parasitic loads and/or battery sensor faults (F.sub.PL,B). The engine starting system 28 may have a low state of health (SOH.sub.L) for the starter motor 25 or the starter solenoid 24. The charging system (CS) may exhibit a charging system fault (F.sub.CS) in the form of a low state of health for the alternator 11, belt slip of the alternator 11, a broken electrical connection between the battery 18 and the alternator 11, or another charging system fault (F.sub.CS). Regarding driver behavior (DB), this column may refer to a calibrated number of short trips or extended parking times, as compared to a calibrated time (t.sub.c), or multiple crank events (MCE) by numeric count. The fuel delivery system 30 may have a low state of health, or the fuel pump 32 may be blocked, leak, or exhibit a sensor fault or other fault (F.sub.30). One these faults may be a root cause of a reported fault condition.

[0027] While the particular manner in which such states of health or other status conditions are determined may vary within the intended scope of the disclosure, an example of such an approach may be found in U.S. Ser. No. 15/399,947, which is hereby incorporated by reference in its entirety. For the auxiliary battery 18 or other DC power source, for instance, such existing methods may include determining when the state of charge is low and then evaluating potential root causes associated with the low state of charge. A fault probability may be determined for each of candidate root cause, with a root cause having the highest fault probability being selected as the root cause for that particular subsystem.

[0028] Similarly, such subsystem-level approaches may define a state of health as an available electric power capacity of a fully-charged battery 18, e.g., as a ratio of the original electric power capacity of the battery 18. Such a state of health may be determined by periodically monitoring voltage, current, and temperature states of the battery 18 during operation and subjecting such measurements to a predefined empirical or physical model that may include differential equations and/or equivalent circuits that are reduced to executable algorithms and calibrations that reside in the battery controller (not shown). In one embodiment, the voltage, current and temperature states and the predefined empirical or physical model may be employed to determine an open-circuit voltage and/or an internal charging resistance of the battery 18, which may be analyzed to determine the state of health. Similar approaches may be used for other subsystems within the vehicle 10.

[0029] The fault report matrix 40 is then populated with a code or other information indicative of whether or not a fault report was generated, e.g., with X denoting the existence of such a fault report and * denoting the absence thereof. Additionally, within the fault report matrix 40, each of the embedded system faults F.sub.1, F.sub.2A, F.sub.2B, F.sub.2C, and F.sub.3 and each root cause subsystem is assigned a corresponding hierarchical priority, shown nominally as one of three relative priorities (1), (2), or (3) in FIG. 2. More priority levels may be used in other embodiments. In a row R1 having just one recorded fault, i.e., a low state of health of the auxiliary battery 18 with no other faults, the method 100 need not resort to the assigned hierarchy for fault reporting. However, in a row R2 having multiple possible fault modes, e.g., a no-crank request fault in which a low state of health of the auxiliary battery 18 is detected, along with battery sensor faults, a charging system fault, and a threshold number of short trips, the controller 50 of FIG. 1 may resort to a hierarchical precedence strategy to determine an appropriate control action, including outputting one or more fundamental root causes.

[0030] Hierarchical treatment of multiple possible fault modes may be described with particular reference to FIG. 3. In a simplified version, the hierarchical precedence rule 60 has three priority levels L1, L2, and L3, which correspond in the fault report matrix 40 of FIG. 2 to the priorities (1), (2), and (3). At the lowest level (L3) lies the fundamental effect of a detected failure, e.g., an ECU short-to-ground condition (F.sub.STG). Level L2 is likewise a fundamental effect of a detected failure, albeit at a higher priority level in the hierarchy than level L3. For instance, a low state of charge of the battery 18 (SOC.sub.B=L) and multiple cranking events (MCE) may represent the second level L2 of the hierarchy. At the highest level, L1, are the fundamental root causes for a given fault, e.g., a no-start fault of the vehicle 10 of FIG. 1. Such root causes may include driver behavior (DB), charging system (CS), and parasitic loads (PL), as well as low battery state of health (SOH.sub.B=L), low starter state of health (SOH.sub.M=L), low fuel delivery system state of health (SOH.sub.30=L), and low engine state of health (SOH.sub.E=L). Thus, the hierarchical precedence rule 60 is used to set forth the root causes and the effects in a descending order of priority.

[0031] FIG. 4 describes an example embodiment of the method 100 noted above, in the illustrative context of diagnosis of an engine starting process that is diagnosed using the approach set forth above, i.e., using the fault report matrix 40 and the assigned hierarchical precedence rule 60. While an onboard embodiment is described with reference to FIG. 4, as will be appreciated by one having ordinary skill in the art in view of this disclosure, the method 100 may reside as instructions on a service tool and/or remotely/accessed via the cloud rather than residing aboard the vehicle 10. For instance, the vehicle 10 may remotely communicate with a service station via a telematics unit as a possible embodiment of output device 33 of FIG. 1, with the method 100 executed offboard. Thus, while the controller 50 is described below for illustrative simplicity, the scope of the disclosure is intended to apply to onboard or offboard implementations in different embodiments.

[0032] Beginning with step S102, the controller 50 of FIG. 1 receives, as an example of a predetermined condition as used herein, a crank request indicative of a requested starting of the engine 12. Such a request may be generated by a body control module (BCM) in certain vehicular embodiments, with the BCM being part of the controller 50 or a separate device in different configurations. The controller 50 reads available fault reports of the particular subsystems that are being evaluated. For instance, step S102 may include reading one or more fault reports describing a state of the battery 18 and/or the starter motor 25, as well as any associated diagnostic codes indicative of a failure mode. The method then proceeds to step S104.

[0033] Step S104 includes determining if an embedded fault report is available for the present ignition cycle, i.e., the ignition cycle that is active and ongoing. The method 100 proceeds to step S106 if an embedded fault report is available for the present ignition cycle. The method 100 otherwise proceeds to step S108.

[0034] At step S106, the controller 50 determines if a subsystem fault report is available for the present ignition cycle. If so, the method 100 proceeds to step S112. The method 100 otherwise proceeds to step S109.

[0035] Step S108 may entail determining whether a subsystem fault report is available for a calibrated number of prior ignition cycles. The method 100 proceeds to step S110 if such reports are available, and to step S109 in the alternative if no prior subsystem fault reports are available.

[0036] Step S109 includes evaluating and examining the fault probabilities of the individual subsystems under evaluation. As part of step S109, the controller 50 determines that the least healthy subsystem is the likely root cause of the present fault mode, and in response to such a determination, the controller 50 executes a corresponding control action. For instance, the controller 50 may record a diagnostic code identifying the root cause/identified subsystem, or may transmit a text message to an operator of the vehicle 10 or a repair facility. The method 100 is then complete, a status that is indicated by ** in FIG. 4.

[0037] Step S110 may include computing probabilistic weighted subsystem fault reports from the prior ignition cycles, e.g., by applying predetermined weights to the various faults so as to apply a greater weight to faults that are more critical and a lesser weight to faults that are deemed less critical. The method 100 then proceeds to step S112.

[0038] At step S112, the controller 50 next references the fault report matrix 40 and identifies the root cause of the present fault mode before proceeding to step S114.

[0039] At step S114, the controller 50 determines whether there are multiple root cause outputs from the fault report matrix 40, and then proceeds to step S116 when this is not the case.

[0040] Step S116 is executed for single root cause events. In this instance, the root cause for the engine no-start condition is identified and communicated in a suitable manner, such as via text message, registration of a corresponding diagnostic code, or the like. The method 100 is then complete, as indicated by * in FIG. 4.

[0041] Step S118 include referring to the hierarchical precedence rule 60 to select and identify the root cause. The method 100 then proceeds to step S120.

[0042] At step S120, the controller 50 outputs the root cause for the vehicle no-start event. The method 100 is then complete, as indicated by ** in FIG. 4.

[0043] Thus, the method 100 may be recorded as instructions on the computer-readable medium of memory (M), as noted above. Such instructions, when executed by the processor (P), cause the controller 50 to record, in the fault report matrix 40, one or more fault reports indicative of one or more of the fault modes, and to use the hierarchical precedence rule 60 to determine the assigned relative priority level for such fault reports. This is done in response to a predetermined condition, such as a detected requested engine starting or ignition event. Execution of the instructions also causes the controller to identify a root cause subsystem as a particular subsystem having the highest of the assigned priority levels, and to execute a control action with respect to the system responsive to the identified root cause subsystem. Such a control action may include recording a diagnostic code and/or transmitting a message indicative of the identified root cause subsystem, or other suitable control actions within the scope of the disclosure.

[0044] The detailed description and the drawings or figures are supportive and descriptive of the disclosure, but the inventive scope is defined solely by the claims. While some of the best modes and other embodiments for carrying out the disclosure have been described in detail herein, various alternative designs and embodiments exist within the intended scope of this disclosure. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.