This disclosure is related to vehicle systems, including monitoring, diagnostics and fault detection.
The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art
On-board monitoring systems execute algorithms that monitor states of parameters to detect presence of a fault and identify a location of any detected fault. On-board monitoring systems are constrained by available memory space, communications, and execution resources in on-board controllers. Known on-board systems permit communications between vehicle systems and remote facilities.
Known diagnostic techniques for a vehicle subsystem, e.g., a fuel system rely on knowledge of prior fault conditions to diagnose and repair a fault. For example, when servicing the vehicle, a maintenance technician may determine by direct testing or review of a recorded diagnostic code that there is a fault in a fuel pump requiring repair or replacement. This reactive diagnosis may not occur until vehicle performance has already been compromised.
A vehicle includes a plurality of subsystems that are monitored during on-going operation. A method for monitoring a subsystem includes monitoring states of commanded and observed parameters for the subsystem. Deviations in the observed parameters are determined off-board the vehicle. The deviations are employed to determine magnitudes of subsystem operating signatures off-board the vehicle. The subsystem operating signatures are employed to identify presence of a subsystem fault and isolate the subsystem fault off-board the vehicle. The presence of the isolated fault is communicated to the vehicle.
One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same,
The vehicle 8 includes a controller 10 that signally and operatively connects to a plurality of subsystems 20, 20′, . . . 20″, an extra-vehicle communications system 16, and a human/machine interface (HMI) device 12. The subsystems 20, 20′, . . . 20″ preferably include devices and associated control elements that provide various vehicle functions including, e.g., functions related to vehicle propulsion, ride/handling, and HVAC, among others. One of the subsystems 20 is a returnless fuel management system described herein with reference to
The vehicle 8 includes a wireless communications system 16 configured to effect extra-vehicle communications, including communication via the wireless communication transmission system 25 to the remote subsystem monitoring system 30. In one embodiment, the wireless communications system 16 includes a wireless telematics communications system capable of short-range wireless communications to a handheld device, e.g., a cellular phone. In one embodiment the handheld device is loaded with a software application that includes a wireless protocol to communicate with the controller 10, and the handheld device executes the extra-vehicle communications, including communication to the remote subsystem monitoring system 30 via the wireless communication transmission system 25.
The controller 10 regularly communicates with the remote subsystem monitoring system 30. Information communicated from the controller 10 includes parametric data representing operation of one or a plurality of the subsystems 20, 20′, . . . 20″ and vehicle identification information including vehicle identification information in the form of vehicle make, model, model year, VIN, and/or other pertinent data.
The remote subsystem monitoring system 30 preferably includes an off-board control scheme 40 and an off-line control scheme 50 configured to provide data management and analytical functions associated with detecting and isolating a fault in one or a plurality of the subsystems 20, 20′, . . . 20″. Table 1 is provided as a key to remote subsystem monitoring system 30 of
The off-line control scheme 50 includes operations that can be executed at any time, including operations that are executed prior to deploying a specific vehicle line, operations that are executed prior to deploying a specific vehicle, and operations that are executed coincident with deployment of a specific vehicle line and a specific vehicle. The off-line control scheme 50 can operate when a specific vehicle is in an off state, or when a specific vehicle is operating. The off-line control scheme 50 supplies information to the off-board control scheme 40 to enable the off-board control scheme 40 to provide functionality to a subject vehicle, e.g., vehicle 8. The information supplied to the subject vehicle by the off-line control scheme 50 may be refreshed and updated to reflect changes associated with learned information.
The off-line control scheme 50 includes a scheme for characterizing a selected one of the subsystems 20 (52). Characterizing a subsystem includes developing relationships between commanded and observed parameters of the subject subsystem by testing the subject subsystem under known operating and ambient conditions, and gathering and analyzing data associated therewith. By way of example, an electric motor can be characterized in terms of electrical voltage, electrical current, rotational position and/or speed, torque or load, and ambient temperature. When the electric motor is employed to power a fluidic pump as part of the subsystem 20, hydraulic pressure may be substituted in place of the torque or load. The relationships between the commanded parameter of electrical voltage and observed parameters of electrical current, rotational position and/or speed, torque or load, and ambient temperature are used as the basis for one or more system models 53. A person having ordinary skill in the art is able to characterize other subsystems to develop relationships between commanded parameters and observed parameters of interest.
A plurality of subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N are developed, and represent analytical parameters associated with changes in one of the observed parameters. The subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N can be employed to detect a subsystem fault based upon changes from a nominal operating state in the observed parameter while the subsystem is operating in response to a known command. When the subsystem includes a fluidic pump, the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N can be associated with changes in observed parameters including pump speed, fluidic pressure, and electrical current from the corresponding nominal operating states when the fluidic pump is operating at a commanded voltage (e.g., a pulsewidth-modulated voltage).
The off-line control scheme 50 includes a scheme for executing a training algorithm that determines weighting vector(s) 55 for one or more of the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N that are associated with subsystem faults for the selected subsystem 20 (54). This includes initially identifying and isolating the subsystem faults that affect operation or performance of the subsystem 20. The subsystem faults of interest are those that affect performance of the subsystem, or affect operation of a related system. A fault isolation database is developed that includes the commanded and observed parameters, e.g., electrical voltage, electrical current, rotational position and/or speed, and torque or load, in relation to one or more of the subsystem faults. The specific subsystem faults can be identified using experiential knowledge, failure-mode effects analyses, and other methods. Developing the fault isolation database can include inducing magnitudes of one of the faults in a known system and monitoring and collecting data for the parameters of interest. The training algorithm determines the weighting vectors 55 for each induced subsystem fault for the selected subsystem 20 using the fault isolation database. In one embodiment, the training algorithm employs statistical analysis tools such as linear discriminant analysis to find linear combinations of the parameters of the fault isolation database that characterize or separate two or more classes of events. The linear discriminant analysis tool analyzes the data to develop dependent variables that are categorical in nature, such as the subsystem faults. The linear discriminant analysis tool seeks combinations of independent variables, i.e., the parameters of interest, that best explain the data. The independent data represented by the parameters of interest are variable in nature, whereas the dependent terms, i.e., the subsystem faults, are categorical in nature. One or more weighting vectors 55 for the selected subsystem 20 can be determined by employing the linear discriminant analysis tool to analyze the data of the fault isolation database. An illustration of results of use of the linear discriminant analysis tool is described herein with reference to EQ. 6.
The off-line control scheme 50 includes a scheme for determining a fault threshold scheme that employs the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N to isolate subsystem faults (56). The magnitudes of the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N can indicate an absence of any fault, or presence of a specific one of the subsystem faults. The fault threshold scheme (56) develops a fault isolation matrix 57 that is deployed for use in identifying and isolating subsystem faults.
The off-board control scheme 40 includes operations that are executed in response to operation of the subject vehicle to provide real-time analytical support to the subject vehicle. Preferably the operations that are executed in response to operation of the subject vehicle are coincident with operation of the subject vehicle.
The off-board control scheme 40 monitors the parametric data communicated from the controller 10 of the vehicle 8 representing operation of the subsystems 20, 20′, . . . 20″ (41). The following describes operation of the off-board control scheme 40 for one of the subsystems 20. It is appreciated that the off-board control scheme 40 is configured to operate in a similar manner for each of the subsystems 20, 20′, . . . 20″. The parametric data for the subsystem includes a first dataset and a second dataset, wherein the first dataset includes a commanded parameter, e.g., a pulsewidth-modulated (PWM) voltage command, and the second dataset includes observed parameters, including e.g., rotational speed, current, and pressure.
The off-board control scheme 40 employs the system models 53 to determine expected states for the observed parameters based upon the commanded parameter (42). The expected states for the observed parameters are each compared to corresponding observed states for the observed parameters to calculate deviations from the expected states (43). The deviations from the expected states are employed to calculate the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N (44), which are normalized to T1, T2, . . . TN (46). Normalizing the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N is conducted to remove relative magnitudes of the various parameters from the analysis, and includes calculating for each of the subsystem operating signatures as follows:
Ti={circumflex over (T)}
i/max({circumflex over (T)}i) [1]
wherein Ti represents a normalized subsystem operating signature for operating signatures ranging from i=1 . . . n.
The normalized operating signatures T1, T2, . . . TN are compared to corresponding thresholds in the fault isolation matrix 57 to detect absence of a subsystem fault or to detect presence of a subsystem fault and isolate a location and/or a source of the subsystem fault (48). The off-board control scheme 40 communicates presence (or absence) of the subsystem fault to the controller 10 of the vehicle 8 (49), and the controller 10 is able to notify the vehicle operate of the presence (or absence) of the subsystem fault using the HMI device 12.
The RFS 220 includes a fuel pump 228, an electrically-powered pump motor 225 and a RFS controller 250, and employs other components, elements and systems as described herein. The fuel pump 228 and pump motor 225 are disposed within the fuel tank 224 and preferably submerged in fuel 223 contained therein. The pump motor 225 electrically connects to the RFS controller 250 via control line 242, with a ground path 244 returning thereto. The pump motor 225 generates and transfers mechanical power via a rotating pump shaft 226 to the fuel pump 228 in response to a pump motor control signal 256 from the RFS controller 250. The fuel pump 228 fluidly connects to the fuel rail 230 via a fuel line 229 to provide pressurized fuel to injectors of the engine 10. The fuel pump 228 is operable to pump fuel 223 to the fuel rail 230 for distribution into the internal combustion engine 10 in response to the pump motor control signal 256. The fuel pump 228 is preferably a roller vane pump or gerotor pump, and may be any suitable pump element. A fuel pressure sensor 251 is employed to monitor fuel pressure 254 in the fuel line 229. A current sensor 222 is configured to monitor electrical current 255 supplied to the pump motor 225 via control line 242. The fuel tank 224 further includes a check valve 246 and a pressure vent valve 248 disposed therein along the fuel line 229. The fuel pump 228 is electrically grounded via a ground path 244 from the pump motor 225 that includes a grounding shield 240 having a ground shield input 241 to RFS controller 250.
The RFS controller 250 signally couples to an engine control module (ECM) 205. The RFS controller 250 operatively connects to the pump motor 225 via control line 242 and signally connects to the fuel pressure sensor 251 and the current sensor 222. The RFS controller 250 generates the pump motor control signal 256 to control the pump motor 225 to operate the fuel pump 228 to achieve and/or maintain a desired fuel system pressure in response to commands from the ECM 205. The RFS controller 250 provides a reference voltage 252 to the pressure sensor 251 and monitors signal outputs from the pressure sensor 251 to determine the fuel pressure 254. The RFS controller 250 monitors the electrical current 255 and the fuel pressure 254 for feedback control and diagnostics.
The pump motor control signal 256 is a pulsewidth-modulated (PWM) voltage signal in one embodiment that is communicated via control line 242 to operate the fuel pump 228. The pump motor control signal 256 provides pulsed electrical energy to the pump motor 225 in the form of a rectangular pulse wave. The pump motor control signal 256 is modulated by the RFS controller 250 resulting in a particular variation of an average value of the pulse waveform. Energy for the pump motor control signal 256 can be provided by a battery, e.g., a DC chemical-electrical energy storage system that supplies a battery input 208 to the RFS controller 250. By modulating the pump motor control signal 256 using the RFS controller 250, energy flow to the pump motor 225 is regulated to control the fuel pump 228 to achieve a desired fuel system pressure for the fuel supplied to the fuel rail 230. The RFS 220 described herein is meant to be illustrative of one subsystem 20.
As previously mentioned, the fuel pump 228 and pump motor 225 are disposed within the fuel tank 224. The pump motor 225 is preferably a brush-type electric motor or another suitable electric motor that provides mechanical power via a rotating pump shaft 226 to the fuel pump 228. The fuel pump 228 propels fuel into the fuel line 229 to the fuel rail 230, thereby generating pressurized fuel in the fuel line 229 and the fuel rail 230, with the fuel pressure 254 monitored by the RFS controller 250 using the pressure sensor 251.
The RFS controller 250 controls the fuel pump 228 to achieve and/or maintain the desired fuel system pressure by applying closed-loop correction derived from the monitored fuel pressure 254 measured by the pressure sensor 251 and the monitored pump current 255 measured by the current sensor 222 as feedback. Further, the pump motor control signal 256 is monitored by the RFS controller 250. Thus, the pump parameters preferably include observed parameters including the fuel pressure 254 and the pump current 255, and commanded pump parameters including the pump motor control signal 256 when the RFS 220 is deployed on-vehicle.
Control module, module, control, controller, control unit, processor and similar terms mean any one or various combinations of one or more of Application Specific Integrated Circuit(s) (ASIC), electronic circuit(s), central processing unit(s) (preferably microprocessor(s)) and associated memory and storage (read only, programmable read only, random access, hard drive, etc.) executing one or more software or firmware programs or routines, combinational logic circuit(s), input/output circuit(s) and devices, appropriate signal conditioning and buffer circuitry, and other components to provide the described functionality. Software, firmware, programs, instructions, routines, code, algorithms and similar terms mean any controller executable instruction sets including calibrations and look-up tables. The control module has a set of control routines executed to provide the desired functions. Routines are executed, such as by a central processing unit, and are operable to monitor inputs from sensing devices and other networked control modules, and execute control and diagnostic routines to control operation of actuators. Routines may be executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing engine and vehicle operation. Alternatively, routines may be executed in response to occurrence of an event.
As described with reference to
Characterizing a subsystem includes developing relationships between commanded and observed parameters of interest by experimentally testing the subsystem under known operating and ambient conditions, and gathering and analyzing data associated therewith. Thus, characterizing the RFS 220 includes experimentally determining observable operating parameters of the RFS 220, including current, pump speed, and system pressure in response to the commanded voltage. System models are generated off-line that can be employed to determine expected states for the observed parameters based upon the commanded parameter. These are the system models 53 described with reference to
I
m
=a
i(V)Ps+bi(V) [2]
wherein Im is expected pump current;
ωm=aω(V)Ps+bω(V) [3]
wherein ωm is expected pump rotational speed;
wherein Pm is expected system pressure;
The off-board control scheme 40 employs the system models 53 to determine expected states for the observed parameters based upon the commanded parameter, as previously described with reference to
The off-board control scheme 40 compares the expected states for the observed parameters of pump current (Im), pump rotational speed (ωm), and system pressure (Pm) to corresponding observed states of pump current (Is), pump rotational speed (ωm_obs), and system pressure (Ps) to calculate deviations from the expected states (43). The RFS 220 may directly monitor the pump rotational speed of the fuel pump 228, or alternatively, the RFS 220 may be configured to estimate the pump speed of the fuel pump 228 based upon a predetermined speed relationship based upon the pump voltage, pump current and fuel pressure. The current deviation (ΔI), speed deviation (Δω) and pressure deviation (ΔP) are calculated as follows.
ΔI=Is−Im
Δω=ωm_obs−ωm
ΔP=Ps−Pm [5]
The aforementioned deviations are employed to calculate magnitudes of subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N using the weighting vector(s) 55 (44). The magnitudes of the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N can be associated with specific faults for the selected subsystem 20 (54). In one embodiment of the RFS 244, the subsystem operating signatures include {circumflex over (T)}1, {circumflex over (T)}2, and {circumflex over (T)}3. The {circumflex over (T)}1 signature is associated with the current deviation (ΔI), and accounts for those factors that influence electrical current. The {circumflex over (T)}2 signature is associated with the speed deviation (Δω). The {circumflex over (T)}3 signature is associated with the pressure deviation (ΔP).
Magnitudes of the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, and {circumflex over (T)}3 are calculated as follows:
{circumflex over (T)}
1=(w1Is+w2Q+w3Ps+w4V+w5ωm_obs)(ΔI)
{circumflex over (T)}
2=Δω
{circumflex over (T)}
3
=ΔP [6]
wherein Is is electrical current;
The off-line control scheme 50 provides a fault threshold scheme that employs the subsystem operating signatures {circumflex over (T)}1, {circumflex over (T)}2, . . . {circumflex over (T)}N normalized to T1, T2, T3 to isolate subsystem faults of the RFS 220 (56). This includes developing a fault threshold set, which takes the following form in one embodiment.
S
o
={s
ε
o
<s<−ε
o}
S
+
={s
ε
+
<s<ε
++}
S
++
={s
ε
++
<s<ε
+++}
S
+++
={s
ε
+++
≦s}
S
−
={s
ε
−−
<s<ε
−}
S
−−
={s
ε
−−−
<s<ε
−−}
S
−−−
={s
ε
−−−
>s}
εo=0.08
ε+=0.09
ε++=0.6
ε+++=0.65
ε−=−0.08
ε−−=−0.6
ε−−−=−0.65 [7]
The fault threshold set shown with reference to EQ. 7 is employed to develop a fault isolation scheme for the RFS subsystem 220.
Each of the normalized subsystem operating signatures T1, T2, T3 can be represented as “s” in the fault threshold set of EQ. 7 to identify a signature attribute, which is one of So, S+, S++, S+++, S−, S−−, and S−−−, based upon the magnitude of the selected “s” normalized signature in relation to error thresholds identified as εo, ε+, ε++, ε+++, ε−, ε−−, and ε−−−. The magnitudes of the error thresholds εo, ε+, ε++, ε+++, ε−, ε−−, and ε−−− set forth in EQ. 7 are meant to be illustrative, and not intended to be restrictive. The fault isolation scheme employs the normalized subsystem operating signatures T1, T2, T3 in relation to the error thresholds identified in the fault threshold set of EQ. 7 to isolate specific subsystem faults, and can take the following form in Table 2.
Thus, in order to identify and isolate one of the subsystem faults, the fault thresholds for all the normalized subsystem operating signatures T1, T2, T3 must be satisfied. The off-board control scheme 40 communicates presence (or absence) of a subsystem fault to the controller 10 of the vehicle 8 (49), and the controller 10 is able to notify the vehicle operate of the presence (or absence) of the subsystem fault using the HMI device 12.
A vehicle can employ a fault detection and isolation system for monitoring an on-board subsystem. This includes a remote subsystem monitoring system 30 having an off-board control scheme 40 and an off-line control scheme 50 that provide data management and analytical functions associated with detecting and isolating a subsystem fault.
A model-based detector based on residuals, parity equations, regression, and parameter estimation techniques can be implemented to detect faults and estimate a state of health of a subsystem during real-time operation of the vehicle. An off-board algorithm and its corresponding parameters can be exported a back-office of a remote service center. An on-vehicle telematics system is employed for periodic/event trigger communication with the service center to establish a data collection session from the subsystem that feeds it to the off-board service center for analysis. When an on-board algorithm detects unexpected behaviors, it can communicate with the remote service center, which collects data that is analyzed by the off-board control scheme for diagnosis, detection and isolation. Vehicle service can be initiated in response to the analysis by the off-board control scheme.
The disclosure has described certain preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US12/52771 | 8/29/2012 | WO | 00 | 2/25/2016 |