Abstract:
A method and control module for determining a sensor error includes a time-based diagnostic module generating a time-based diagnostic for a sensor and an event-based diagnostic module generating an event-based diagnostic for the sensor. A synchronizing module synchronizes the time-based diagnostic and the event-based diagnostic to obtain a diagnostic result. A fault indicator module generates a fault signal in response to the diagnostic result.

Description:
FIELD 
     The present disclosure relates to diagnostic systems for electronic control systems, and more particularly, to control systems and methods for detecting an out of range condition for sensors of the electronic control systems. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Direct injection gasoline engines are currently used by many engine manufacturers. In a direct injection engine, highly pressurized gasoline is injected via a common fuel rail directly into a combustion chamber of each cylinder. This is different than conventional multi-point fuel injection that is injected into an intake tract or cylinder port. 
     Gasoline-direct injection enables stratified fuel-charged combustion for improved fuel efficiency and reduced emissions at a low load. The stratified fuel charge allows ultra-lean burn and results in high fuel efficiency and high power output. The cooling effect of the injected fuel and the even dispersion of the air-fuel mixture allows for more aggressive ignition timing curves. Ultra lean burn mode is used for light-load running conditions when little or no acceleration is required. Stoichiometric mode is used during moderate load conditions. The fuel is injected during the intake stroke and creates a homogenous fuel-air mixture in the cylinder. A fuel power mode is used for rapid acceleration and heavy loads. The air-fuel mixture in this case is a slightly richer than stoichiometric mode which helps reduce knock. 
     Direct-injected engines are configured with a high-pressure fuel pump used for pressurizing the injector fuel rail. A pressure sensor is attached to the fuel rail for control feedback. The pressure sensor provides an input to allow the computation of the pressure differential information used to calculate the injector pulse width for delivering fuel to the cylinder. Errors in the measured fuel pressure at the fuel rail result in an error in the mass of the fuel delivered to the individual cylinder. 
     SUMMARY 
     The present disclosure provides a method and system by which an error from the pressure sensor in the fuel rail may be quantified and used for closed-loop control. This will result in the proper mass of fuel being delivered to the individual cylinder. This may also allow for diagnostics of the fuel rail pressure sensor. 
     In one aspect of the invention, a method includes generating a time-based diagnostic, generating an event-based diagnostic, synchronizing the time-based diagnostic and the event-based diagnostic to obtain a diagnostic result and generating a fault signal in response to the diagnostic result. 
     In a further aspect of the invention, a control module for determining a sensor error includes a time-based diagnostic module generating a time-based diagnostic for a sensor and an event-based diagnostic module generating an event-based diagnostic for the sensor. A synchronizing module synchronizes the time-based diagnostic and the event-based diagnostic to obtain a diagnostic result. A fault indicator module generates a fault signal in response to the diagnostic result. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of a control system that adjusts engine timing based on vehicle speed according to some implementations of the present disclosure; 
         FIG. 2  is a functional block diagram of the fuel injection system according to the present disclosure; 
         FIG. 3  is a block diagram of the control system of  FIG. 1  for performing the method of the present disclosure; 
         FIG. 4  is a flowchart of a method for determining a pressure sensor error; and 
         FIG. 5  is a plot of a time-based error versus an event-based error over time. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As used herein, the term boost refers to an amount of compressed air introduced into an engine by a supplemental forced induction system such as a turbocharger. The term timing refers generally to the point at which fuel is introduced into a cylinder of an engine (fuel injection) is initiated. 
     Referring now to  FIG. 1 , an exemplary engine control system  10  is schematically illustrated in accordance with the present disclosure. The engine control system  10  includes an engine  12  and a control module  14 . The engine  12  can further include an intake manifold  15 , a fuel injection system  16  having fuel injectors (illustrated in  FIG. 2 .), an exhaust system  17  and a turbocharger  18 . The exemplary engine  12  includes six cylinders  20  configured in adjacent cylinder banks  22 ,  24  in a V-type layout. Although  FIG. 1  depicts six cylinders (N=6), it can be appreciated that the engine  12  may include additional or fewer cylinders  20 . For example, engines having 2, 4, 5, 8, 10, 12 and 16 cylinders are contemplated. It is also anticipated that the engine  12  can have an inline-type cylinder configuration. While a gasoline powered internal combustion engine utilizing direct injection is contemplated, the disclosure may also apply to diesel or alternative fuel sources. 
     During engine operation, air is drawn into the intake manifold  15  by the inlet vacuum created by the engine intake stroke. Air is drawn into the individual cylinders  20  from the intake manifold  15  and is compressed therein. Fuel is injected by the injection system  16 , which is described further in  FIG. 2 . The air/fuel mixture is compressed and the heat of compression and/or electrical energy ignites the air/fuel mixture. Exhaust gas is exhausted from the cylinders  20  through exhaust conduits  26 . The exhaust gas drives the turbine blades  25  of the turbocharger  18  which in turn drives compressor blades  27 . The compressor blades  27  can deliver additional air (boost) to the intake manifold  15  and into the cylinders  20  for combustion. 
     The turbocharger  18  can be any suitable turbocharger such as, but not limited to, a variable nozzle turbocharger (VNT). The turbocharger  18  can include a plurality of variable position vanes  27  that regulate the amount of air delivered into the engine  12  based on a signal from the control module  14 . More specifically, the vanes  27  are movable between a fully-open position and a fully-closed position. When the vanes  27  are in the fully-closed position, the turbocharger  18  delivers a maximum amount of air into the intake manifold  15  and consequently into the engine  12 . When the vanes  27  are in the fully-open position, the turbocharger  18  delivers a minimum amount of air into the intake manifold of engine  12 . The amount of delivered air is regulated by selectively positioning the vanes  27  between the fully-open and fully-closed positions. 
     The turbocharger  18  includes an electronic control vane solenoid  28  that manipulates a flow of hydraulic fluid to a vane actuator (not shown). The vane actuator controls the position of the vanes  27 . A vane position sensor  30  generates a vane position signal based on the physical position of the vanes  27 . A boost sensor  31  generates a boost signal based on the additional air delivered to the intake manifold  15  by the turbocharger  18 . While the turbocharger implemented herein is described as a VNT, it is contemplated that other turbochargers employing different electronic control methods may be employed. 
     A manifold absolute pressure (MAP) sensor  34  is located on the intake manifold  15  and provides a (MAP) signal based on the pressure in the intake manifold  15 . A mass air flow (MAF) sensor  36  is located within an air inlet and provides a mass air flow (MAF) signal based on the mass of air flowing into the intake manifold  15 . The control module  14  uses the MAF signal to determine the mass of air flowing into the intake manifold. The mass of the intake air can be used to determine the fuel supplied to the engine  12  based on the A/F ratio in response to engine start, catalyst light-off, and engine metal overheat protection. An RPM sensor  44  such as a crankshaft position sensor provides an engine speed signal. An intake manifold temperature sensor  46  generates an intake air temperature signal. The control module  14  communicates an injector timing signal to the injection system  16 . A vehicle speed sensor  49  generates a vehicle speed signal. 
     The exhaust conduits  26  can include an exhaust recirculation (EGR) valve  50 . The EGR valve  50  can recirculate a portion of the exhaust. The controller  14  can control the EGR valve  50  to achieve a desired EGR rate. 
     The control module  14  controls overall operation of the engine system  10 . More specifically, the control module  14  controls engine system operation based on various parameters including, but not limited to, driver input, stability control and the like. The control module  14  can be provided as an Engine Control Module (ECM). 
     The control module  14  can also regulate operation of the turbocharger  18  by regulating current to the vane solenoid  28 . The control module  14  according to an embodiment of the present disclosure can communicate with the vane solenoid  28  to provide an increased flow of air (boost) into the intake manifold  15 . 
     An exhaust gas oxygen sensor  60  may be placed within the exhaust manifold or exhaust conduit to provide a signal corresponding to the amount of oxygen in the exhaust gasses. 
     Referring now to  FIG. 2 , the fuel injection system  16  is shown in further detail. A fuel rail  110  is illustrated having fuel injectors  112  that deliver fuel to cylinders of the engine. It should be noted that the fuel rail  110  is illustrated having three fuel injectors  112  corresponding to the three cylinders of one bank of cylinders of the engine  12  of  FIG. 1 . More than one fuel rail  110  may be provided on a vehicle. Also, more or fewer fuel injectors may also be provided depending on the configuration of the engine. The fuel rail  110  delivers fuel from a fuel tank  114  through a high-pressure fuel pump  116 . The control module  14  controls the fuel pump  116  in response to various sensor inputs including an input signal  118  from a pressure sensor  120 . The control module  14  also controls the injectors  112 . The operation of the system will be further described below. 
     Referring now to  FIG. 3 , the control module of  FIG. 1  is illustrated in further detail. The control module  14  may include a time-based diagnostic module  210  and an event-based diagnostic module  212 . The time-based diagnostic module  210  and the event-based diagnostic module  212  may provide two different methods for diagnosing a sensor such as a pressure sensor. The time-based diagnostic module  210  generates a time-based diagnostic signal and communicates the time-based diagnostic signal to a synchronizing module  214 . The event-based diagnostic module  212  communicates an event-based diagnostic signal to the synchronizing module  214 . The synchronizing module  214  communicates a synchronized diagnostic result to a fault indicator module  216 . 
     The time-based diagnostic module  210  may include a timer module  250  that generates a timing signal capable of timing various time periods, including a sample time and an end time and therefore an overall time period. The timer module  250  also may time regular time intervals over which samples are to be taken. The timing signal from the timer module  250  is communicated to a sample module  252 . The sample module  252  samples the sensor signal such as the pressure sensor signal used in this example. The sample module  252  samples at the intervals provided by the timer module  252 . The sample module  252  may sample at a first rate which is different than a second rate used in the event-based diagnostic module. A sample comparison module  254  compares the samples to a comparison threshold. A counter-module  256  counts the number of comparisons that are above or below or both for a predetermined sample. Thus, the sample comparison module  254  may compare a pressure high threshold and a pressure low threshold with the sample and thus the number of counts above a high-pressure threshold or below a low-pressure threshold may be counted in the counter module  256 . In block  258 , the counts from the counter module  256  are compared to a counter-threshold which in turn may be communicated to the synchronizing module  214 . 
     When the time-based diagnostic module is used alone, a faulty sensor may be detected too late at high RPMs while using many faulty signals. At low RPMs the diagnostic test may pass too soon for a good sensor. 
     The event-based diagnostic module  212  generates an event-based diagnostic signal. An event may, for example, be an engine-synchronized event. The event signal for triggering the sample may be received at the event trigger module  270 . The event trigger module  270  may receive various types of signals including an engine synchronization event such as a camshaft or crankshaft timing signal. The sample module may sample the sensor signal such as the pressure sensor signal at a different rate than the time-based diagnostic module  210 . Of course, the same rate may also be used. The sample module  272  generates sample signals and communicates the sample signals to a sample comparison module  274 . The sample module at the second rate  272  receives an input from the first rate sample module  252 . The sample comparison module  274  compares each sample to a threshold. The thresholds may be pressure-high thresholds and pressure-low thresholds as described above. Therefore, the counter module  276  may generate a count of the number of pressure-high signals and pressure-low signals. The number of counts counted by the counter  276  is compared to a count threshold in a count threshold module  278 . The count threshold module  278  generates an event-based diagnostic and communicates the event-based diagnostic to the synchronizing module  214 . 
     The synchronizing module  214  may include a table that contains the current state of the time-based and event-based results. The time-based and the event-based results may start and stop at different times relative to each other. When one of the tests fails, the other test may be discontinued until desired again, or both tests may be allowed to run to completion. This depends on the desired goals for the particular product. For the event-based or engine-synchronized system, the test may pass too soon for a good sensor at high RPMs or may fail too late for a bad sensor at low RPMs. Thus, both the time-based diagnostic and the event-based diagnostic have drawbacks. Because of the different sample rates in the time-based diagnostic module  210  and the event-based diagnostic module  212 , improved results may be obtained. The synchronization module  214  may send a failure signal or a fault indicator to the fault indicator module  216  when either sensor fails a test. When both sensors pass a test, a passing sensor may be indicated with no fault. The synchronization module may also perform a balancing of the conditions in the synchronization module for a high RPM state or a low RPM state of the engine may be provided. Thus, balancing may occur based on the speed of the engine. Engine-synchronized diagnostics may be used at high RPMs while time-based may be used at low RPMs. 
     Referring now to  FIG. 4 , a method  300  for operating this system is set forth. In step  310 , the system starts. In step  312 , it is determined whether time-based sampling is enabled. If time-based sampling is not enabled step  314  determines whether event-based sampling is enabled. If event-based sampling is enabled, step  316  generates and stores event-based diagnostic results. Referring back to step  312 , if time-based sampling is enabled, step  320  determines whether event-based sampling has been enabled. If event-based sampling has not been enabled, step  324  generates and stores time-based diagnostic results. The system is capable of one or both types of diagnostics. 
     Referring back to step  320 , if both time-based sampling has been enabled and event-based sampling has been enabled, step  330  generates and stores time-based diagnostic results while step  332  generates and stores event-based diagnostic results. As mentioned above, both the time-based diagnostic result and the event-based diagnostic results may take place over different time periods and may have different sampling rates. In step  334 , the time-based and event-based diagnostic results are synchronized as described above. The outputs of steps  316  and  324  are also provided to step  334  for synchronization. Synchronization may be performed when required if both event-based and time-based diagnostic results are provided. In step  336 , the synchronized diagnostic result is generated and stored. The diagnostic result may be used to generate a fault indicator or provide an indicator through an on-board diagnostic system that a particular sensor has failed. While the above example uses a pressure sensor such as a fuel rail pressure sensor, various types of pressure sensors and other types of sensors through the system may be used. 
     Referring now to  FIG. 5 , a time-based pressure signal  412  is illustrated compared to an event-based pressure signal  410 . As can be seen, the results are different particularly early on in the timing of a transient pressure change. Later on in the timing, the two results converge. Therefore, synchronization between the time-based signal and the event-based signal is desirable to provide more accurate determination of errors. 
     The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.