Abstract:
An engine toque estimator according to the invention includes a vehicle data bus that provides a plurality of engine operating inputs including at least one of engine RPM, spark and a dilution estimate. A steady state torque estimator communicates with the vehicle data bus and generates a steady state engine torque signal. A measurement model communicates with the vehicle data bus and compensates for errors associated with engine-to-engine variation. A dynamic torque estimator communicates with at least one of the vehicle data bus, the measurement model, and the steady state torque estimator and generates an actual torque signal.

Description:
TECHNICAL FIELD 
     The present invention relates to control systems for internal combustion engines, and more particularly to control systems that estimate torque for engine RPM and torque control. 
     BACKGROUND OF THE INVENTION 
     Conventional control systems that estimate torque are predominantly designed to control shift quality. The torque-estimating accuracy of these systems is defined by the desired quality for transmission shifts. Torque estimation calculations are based on the following relationships: 
     
       
         
           IndTorque=k*GPO*N 
           cyl 
           *EFF*N 
           cyl 
           
             — 
           
           shut 
           −SparkLoss 
         
       
     
     
       
         
           FrictionTorque=BaseTable*OTcorrector+ACCdriveFriction 
         
       
     
     
       
         
           Torque=IndTorque−FrictionTorque−InertiaTorque 
         
       
     
     where GPO is mass air flow (gram of air per cylinder), N cyl  is a total number of cylinders in the internal combustion engine, EFF is a function of the air/fuel ratio, sparkloss is a function of RPM and GPO, and OTcorrector is an oil temperature correction. 
     The conventional torque estimation systems do not have direct inputs such as RPM, exhaust gas recirculation (EGR), spark, and other inputs that are needed for engine RPM and torque control (ERTC). The conventional torque estimation systems are also unable to recalculate inputs based upon requested torque or to optimize brake torque. 
     SUMMARY OF THE INVENTION 
     An engine toque estimator according to the invention includes a vehicle data bus that provides a plurality of engine operating parameters including at least one of engine RPM, spark and dilution estimate signals. A steady state torque estimator communicates with the vehicle data bus and generates a steady state engine torque signal. A measurement model communicates with the vehicle data bus and compensates for errors that are associated with engine manufacturing variations. A dynamic torque estimator communicates with at least one of the vehicle data bus, the measurement model, and the steady state torque estimator and generates an actual engine torque signal. 
     In other features of the invention, the engine-operating inputs further include air per cylinder, unmanaged spark, oil temperature, air/fuel ratio, barometer, enabled cylinders, and intake air estimate signals. The steady state torque estimator generates at least one of a GPO sensitivity signal, an RPM sensitivity signal, a spark sensitivity signal, and a spark squared sensitivity signal. The steady state torque estimator further generates an unmanaged engine torque signal. The steady state torque estimator outputs a steady state engine torque signal to the dynamic torque estimator. The measurement model outputs a torque estimate correction signal to the dynamic torque estimator. The dynamic torque estimator outputs the actual engine torque signal. 
     In yet other features, the steady state torque estimator includes a base steady state torque calculator, a steady state torque temperature corrector, and a steady state torque air/fuel corrector. The base steady state torque calculator receives the RPM, spark, unmanaged spark, dilution estimate and GPO signals from the vehicle data bus and generates the GPO, RPM, spark, and spark squared sensitivity signals. The base steady state torque calculator generates a base unmanaged engine torque signal that is output to the steady state torque temperature corrector. The steady state torque temperature corrector receives oil temperature and GPO signals from the vehicle data bus and generates a steady state unmanaged torque base signal that is output to the steady state torque air/fuel corrector. The steady state torque air/fuel corrector generates unmanaged engine torque and steady state engine torque signals. 
     In still other features, the base steady state torque calculator includes a torque sensitivity calculator and a final base steady state torque calculator. The torque sensitivity calculator receives the dilution estimate and RPM signals from the vehicle data bus and generates the GPO, RPM, spark, and spark squared sensitivity signals. The sensitivity signals are input to the final base steady state torque calculator. The final base steady state torque calculator receives the GPO, RPM, spark and unmanaged spark signals from the vehicle data bus. The final base steady state torque calculator calculates base steady state unmanaged torque and base steady state torque signals. 
     Further areas of applicability of the present invention 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 invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a functional block diagram of the ERTC torque estimation system that includes a steady state torque estimator, a measurement model and a dynamic torque estimator according to the present invention; 
     FIG. 2 is a functional block diagram of the steady state torque estimator of FIG. 1 that includes a base steady state torque calculator, a steady state torque temperature corrector, and a steady state torque air/fuel corrector; 
     FIG. 3 is a functional block diagram of the base steady state torque calculator of FIG. 2 that includes a torque sensitivity calculator and a final base steady state torque calculator; 
     FIG. 4 is a functional block diagram of the final base steady state torque calculator of FIG. 3; and 
     FIG. 5 is a functional block diagram of the torque sensitivity calculator of FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     The present invention employs direct inputs such as RPM, a dilution estimate, spark, etc., that are required for engine RPM and torque control (ERTC). The present invention will be described with ERG position as the dilution estimate. Skilled artisans will appreciated that the dilution estimate can also be based on cam phaser position, a combination of the EGR position and cam phaser position, or any other dilution estimate can be used. The present invention can recalculate inputs based upon requested torque and can optimize brake torque. The present invention estimates torque based on torque sensitivities based on the following relationships: 
     
       
           T=f ( G, r, S, E, AF, OT, BARO )=( a   s   *S+a   r   *r+a   G   *G+a   E   *E )*η AF *η cool   
       
     
     
       
           Torque=T   warm *η AF *η cool   
       
     
     
       
         
           T 
           warm 
           =a 
           s 
           *S+a 
           s2 
           *S 
           2 
           +a 
           r 
           *r+a 
           G 
           *G 
         
       
     
     
       
           T   warm =( a   s   +δa   s   *E )* S +( a   s2   +δa   s2   *E )* S   2 +( a   r   +δa   r|E   *E )* R +( a   g   +δa   g|E )* G   
       
     
     where: 
     a s =a s (R, B, #cyl); 
     a s2 =a s2 (R, B, #cyl); 
     a r =a r (R, B, #cyl); 
     a g =a g (R, B, #cyl); 
     η AF =η AF (AF); and 
     η cool =η cool  (COOL, OT, GPO). 
     Each open loop system has an error that is associated with engine manufacturing variations. In other words, there are manufacturing differences between the same types of engines. The present invention provides a feedback mechanism to compensate for these engine manufacturing variations. The compensation is based on a model of the torque converter: 
     
       
         
           T 
           tc 
           =K 
           2 
           *R 
           2 
         
       
     
     where K is a k-factor. During steady state conditions, the engine torque is equal to the torque of the torque converter. 
     Referring now to FIG. 1, a vehicle data bus  50  outputs a plurality of engine operating signals to a steady state torque estimator  54 . The engine operating signals preferably include GPO (air per cylinder), spark, unmanaged spark, EGR position, oil temperature, air/fuel ratio, barometer, enabled cylinders, and RPM signals. The vehicle data bus  50  also outputs an intake air estimate signal to a measurement model  58 . In addition, the vehicle data bus  50  provides gear and RPM signals to a dynamic torque estimator  60 . 
     The steady state torque estimator  54  generates sensitivity signals such as GPO, RPM, spark and spark squared sensitivity signals. The steady state torque estimator  54  also generates an unmanaged engine torque signal. The steady state torque estimator  54  outputs a steady state engine torque signal to the dynamic torque estimator  60 . The measurement model  58  also outputs a torque estimate correction signal to the dynamic torque estimator  60 . The dynamic torque estimator  60  outputs an actual engine torque signal. 
     Referring now to FIG. 2, the steady state torque estimator  54  is shown in further detail and includes a base steady state torque calculator  70 , a steady state torque temperature corrector  74 , and a steady state torque air/fuel corrector  78 . The base steady state torque calculator  70  receives the RPM, spark, unmanaged spark, EGR position and GPO signals from the vehicle data bus  50 . The base steady state torque calculator  70  generates the sensitivity signals including the GPO, RPM, spark, and spark squared sensitivity signals. 
     The base steady state torque calculator  70  also generates a base unmanaged engine torque signal that is output to the steady state torque temperature corrector  74 . The steady state torque temperature corrector  74  receives the oil temperature and air per cylinder signals from the vehicle data bus  50 . The steady state torque temperature corrector  74  generates a steady state unmanaged torque base signal that is output to the steady state torque air/fuel corrector  78 . The steady state torque air/fuel corrector  78  generates unmanaged engine torque and steady state engine torque signals. 
     Referring now to FIG. 3, the base steady state torque calculator  70  of FIG. 2 is shown in further detail and includes a torque sensitivity calculator  84  and a final base steady state torque calculator  86 . The torque sensitivity calculator  84  receives the EGR position and RPM signals and generates the sensitivity signals including the GPO, RPM, spark, and spark squared sensitivity signals. The sensitivity signals are input to the final base steady state torque calculator  86  that also receives the GPO, RPM, spark and unmanaged spark signals from the vehicle data bus  50 . The final base steady state torque calculator  86  calculates base steady state unmanaged torque and base steady state torque signals. 
     Referring now to FIG. 4, the final base steady state torque calculator  86  is shown in further detail and includes multiplier and adder circuits. A first multiplier  90  multiplies GPO (air per cylinder) and GPO sensitivity signals. An output of the multiplier  90  is input to a first adder  92  and a second adder  94 . A second multiplier  96  multiplies RPM and RPM sensitivity signals. An output of the second multiplier  96  is input to the first adder  92  and the second adder  94 . 
     A third multiplier  100  multiplies spark and spark sensitivity signals and outputs the product to the first adder  92 . A fourth multiplier  102  multiplies spark squared and spark squared sensitivity signals and outputs the product to the first adder  92 . A fifth multiplier  104  multiplies unmanaged spark and spark sensitivity and outputs the product to the second adder  94 . A sixth multiplier  106  multiplies unmanaged spark squared and spark squared sensitivity signals and outputs the product to the second adder  94 . The first adder  92  outputs the steady state torque base signal. The second adder  94  outputs the base steady state unmanaged torque signal. 
     Referring now to FIG. 5, the torque sensitivity calculator  84  is shown in further detail. A first multiplier  120  multiplies EGR position and an output of a spark_EGR sensitivity lookup table (LUT)  122 . The LUT  122  is preferably accessed by the RPM signal. The multiplier  120  outputs a spark/EGR sensitivity signal that is input to a first adder  124 . A second multiplier  130  multiplies EGR position and an output of a spark squared/EGR sensitivity LUT  132 . The LUT  132  is preferably accessed by the RPM signal. The multiplier  130  outputs a spark squad/EGR sensitivity signal that is input to a second adder  134 . A third multiplier  140  multiplies EGR position and an output of a GPO_EGR sensitivity LUT  142 . The LUT  142  is preferably accessed by the RPM signal. The multiplier  140  outputs a GPO/EGR sensitivity signal that is input to a third adder  144 . A fourth multiplier  150  multiplies EGR position and an output of a RPM/EGR sensitivity LUT  152 . The LUT  152  is preferably accessed by the RPM signal. The multiplier  150  outputs a GPO/EGR sensitivity signal that is input to a third adder  154 . 
     A spark sensitivity signal is generated by a LUT  158  that is accessed using the RPM signal. The spark sensitivity signal is input to the first adder  124 . An output of the first adder  124  is the spark sensitivity signal. A spark squared sensitivity signal is generated by a LUT  160  that is accessed using the RPM signal. The spark squared sensitivity signal is input to the second adder  124 . An output of the second adder  134  is the spark squared sensitivity signal. A GPO sensitivity signal is generated by a LUT  162  that is accessed using the RPM signal. The GPO sensitivity signal is input to the third adder  144 . An output of the third adder  144  is the GPO sensitivity signal. An RPM sensitivity signal is generated by a LUT  164  that is accessed using the RPM signal. The RPM sensitivity signal is input to the fourth adder  144 . An output of the fourth adder  144  is the RPM sensitivity signal. 
     The present invention enables additional functions that were not provided in prior torque estimation systems. The torque estimation system of the present invention has inputs such as the RPM, exhaust gas recirculation (EGR), spark, and other signals that are needed for engine RPM and torque control (ERTC). The torque estimation system is also able to recalculate inputs based upon requested torque. The torque estimation system also optimizes brake torque. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention 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.