Patent Publication Number: US-9890717-B2

Title: System and method for estimating turbocharger operating speed

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/537,100 filed on Nov. 10, 2014, entitled “System and Method for Estimating Turbocharger Operating Speed”, which is a continuation of U.S. patent application Ser. No. 13/244,540 filed on Sep. 25, 2011, now U.S. Pat. No. 8,892,332, entitled “System and Method for Estimating Turbocharger Operating Speed,” owned by the instant assignee and hereby expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to turbochargers for internal combustion engines, and more specifically to systems and methods for estimating the operating speed of such turbochargers. 
     BACKGROUND 
     A turbocharger is conventionally used with an internal combustion engine to increase flow of air entering the engine under certain operating conditions. It is desirable to estimate the operating speed of such turbochargers using information provided by actual and/or virtual on-board sensors other than a turbocharger operating speed sensor. 
     SUMMARY 
     The present invention may comprise one or more of the features recited in the claims appended hereto, and/or one or more of the following features and combinations thereof. A system for estimating an operating speed of a turbocharger including a compressor having an air inlet and an air outlet may comprise a first pressure sensor configured to produce a first pressure signal indicative of pressure at or near the air inlet of the compressor, a second pressure sensor configured to produce a second pressure signal indicative of pressure at or near the air outlet of the compressor, a temperature sensor configured to produce a temperature signal indicative of temperature at or near the air inlet of the compressor, a flow sensor configured to produce a flow signal indicative of a flow rate of air into the air inlet of the compressor, and a control circuit. The control circuit may include a memory having instructions stored therein that are executable by the control circuit to estimate the operating speed of the turbocharger as a function of the first and second pressure signals, the temperature signal and the flow signal. 
     The memory may have stored therein a map of compressor pressure ratio values as a function of air inlet flow rate values at a plurality of different turbocharger operating speeds. The instructions stored in the memory may further include instructions that are executable by the control circuit to process the flow signal using the map to generate a number of pairs of turbocharger operating speed and compressor pressure ratio values. The instructions stored in the memory may further include instructions that are executable by the control circuit to determine a compressor-corrected flow rate value as a function of the flow signal, the temperature signal and the first pressure signal. The map may be stored in the memory as a map of compressor pressure ratio values as a function of compressor-corrected flow rate values at the plurality of different turbocharger operating speeds. The instructions stored in the memory may further include instructions that are executable by the control circuit to determine a current compressor pressure ratio value as a function of the first and second pressure values, and to process the current compressor pressure ratio value along with a function of at least two of the number of pairs of turbocharger operating speed and compressor pressure ratio values to estimate the operating speed of the turbocharger. The estimated operating speed of the turbocharger may represent a compressor-corrected turbocharger operating speed, and the instructions stored in the memory may further include instructions that are executable by the control circuit to estimate the operating speed of the turbocharger as a function of the compressor-corrected operating speed of the turbocharger and the temperature signal. 
     The instructions stored in the memory may further include instructions that are executable by the control circuit to determine a current compressor pressure ratio as a function of the first and second pressure signals, to process the flow signal using a compressor pressure ratio map to generate a number of pairs of turbocharger operating speed and compressor pressure ratio values, and to estimate the operating speed of the turbocharger using the current compressor pressure ratio value and a function of at least two of the number of pairs of turbocharger operating speed and compressor pressure ratio values. The estimated operating speed of the turbocharger may represent a compressor-corrected turbocharger operating speed, and the instructions stored in the memory may further include instructions that are executable by the control circuit to estimate the operating speed of the turbocharger as a function of the compressor-corrected turbocharger operating speed and the temperature signal. 
     The control circuit may be configured to control operation of an internal combustion engine operatively coupled to the turbocharger. 
     A system for estimating an operating speed of a turbocharger including a compressor having an air inlet and an air outlet may comprise a first pressure sensor configured to produce a first pressure signal indicative of pressure at or near the air inlet of the compressor, a second pressure sensor configured to produce a second pressure signal indicative of pressure at or near the air outlet of the compressor, a flow sensor configured to produce a flow signal indicative of a flow rate of air into the air inlet of the compressor, and a control circuit. The control circuit may include a memory having instructions stored therein that are executable by the control circuit to process the flow signal using a compressor pressure ratio map to generate a number of pairs of turbocharger operating speed and compressor pressure ratio values, to determine a current compressor pressure ratio value as a function of the first and second pressure signals, and to estimate the operating speed of the turbocharger using the current compressor pressure ratio value and a function of at least two of the number of pairs of the turbocharger operating speed and compressor pressure ratio values. 
     The system may further comprise a temperature sensor configured to produce a temperature signal indicative of temperature at or near the air inlet of the compressor, and the instructions stored in the memory may further include instructions that are executable by the control circuit to determine a compressor-corrected flow value as a function of the flow signal, the first pressure signal and the temperature signal. The instructions stored in the memory may further include instructions that are executable by the control circuit to process the compressor-corrected flow value using the compressor pressure ratio map to generate the number of pairs of turbocharger operating speed and compressor pressure ratio values. The compressor pressure ratio map may be stored in the memory and may be configured to map air inlet flow rate values to compressor pressure ratio values at a plurality of different turbocharger operating speeds. The instructions stored in the memory may further include instructions that are executable by the control circuit to generate the number of pairs of turbocharger operating speed and compressor pressure ratio values by processing the compressor-corrected flow value using the compressor pressure ratio map. 
     The system may further comprise a temperature sensor configured to produce a temperature signal indicative of temperature at or near the air inlet of the compressor. The estimated operating speed of the turbocharger may represent a compressor-corrected turbocharger operating speed, and the instructions stored in the memory may further include instructions that are executable by the control circuit to estimate the turbocharger operating speed value as a function of the compressor-corrected turbocharger operating speed and the temperature signal. 
     The compressor pressure ratio map may be stored in the memory and may be configured to map air inlet flow rate values to compressor pressure ratio values at a plurality of different turbocharger operating speeds. The instructions stored in the memory may further include instructions that are executable by the control circuit to generate the number of pairs of turbocharger operating speed and compressor pressure ratio values by processing the flow signal using the compressor pressure ratio map. 
     The control circuit may be configured to control operation of an internal combustion engine operatively coupled to the turbocharger. 
     A method of estimating an operating speed of a turbocharger including a compressor having an air inlet and an air outlet may comprise determining a first pressure value corresponding to pressure at or near the air inlet of the compressor, determining a second pressure value corresponding to pressure at or near the air outlet of the compressor, determining a temperature value corresponding to a temperature at or near the air inlet of the compressor, determining a flow rate value corresponding to a flow rate of air entering the air inlet of the compressor, and estimating the operating speed of the turbocharger as a function of the first pressure value, the second pressure value, the temperature value and the flow rate value. 
     Estimating the operating speed of the turbocharger may comprise determining a current compressor pressure ratio as a function of the first and second pressure values, processing the flow rate value using a compressor pressure ratio map to generate a number of pairs of turbocharger operating speed and compressor pressure ratio values, the compressor pressure ratio map configured to map compressor air inlet flow rate values to compressor pressure ratio values at a plurality of different turbocharger operating speeds, and processing the current compressor pressure ratio value along with a function of at least two of the number of pairs of turbocharger operating speed and compressor pressure ratio values to estimate the operating speed of the turbocharger. Processing the flow rate value using a compressor pressure ratio map to generate the number of pairs of turbocharger operating speed and compressor pressure ratio values may comprises determining a compressor-corrected flow rate value as a function of the flow rate value, the first pressure value and the temperature value, and processing the compressor-corrected flow rate value using the compressor pressure ratio map to generate the number of pairs of turbocharger operating speed and compressor pressure ratio values. The estimated operating speed of the turbocharger may represent a compressor-corrected turbocharger operating speed, and the method may further comprise determining the operating speed of the turbocharger as a function of the compressor-corrected operating speed of the turbocharger and the temperature value. 
     The method may further comprise using a control circuit configured to control operation of an internal combustion engine to which the turbocharger is operatively coupled to execute all of the determining steps and the estimating step. 
     The method may further comprise determining the first pressure by processing a first pressure signal produced by a first pressure sensor positioned at or near the air inlet of the compressor, determining the second pressure by processing a second pressure signal produced by a second pressure sensor positioned at or near the air outlet of the compressor, determining the flow rate value by processing a flow rate signal produced by a flow rate sensor positioned at or near the air inlet of the compressor, and determining the temperature value by processing a temperature signal produced by a temperature sensor positioned at or near the air inlet of the compressor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one illustrative embodiment of a system for estimating turbocharger operating speed. 
         FIG. 2  is a block diagram of one illustrative embodiment of the control circuit of  FIG. 1  configured to estimate turbocharger operating speed. 
         FIG. 3  is a turbocharger compressor pressure ratio map including a plot of turbocharger compressor ratio vs. compressor-corrected inlet air flow for a plurality of different turbocharger operating speed values. 
     
    
    
     DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a number of illustrative embodiments shown in the attached drawings and specific language will be used to describe the same. 
     Referring now to  FIG. 1 , a diagrammatic illustration is shown of one illustrative embodiment of a system  10  for estimating turbocharger operating speed. In the illustrated embodiment, the system  10  includes an internal combustion engine  12  having an intake manifold  14  that is fluidly coupled to an air  16  outlet of a compressor  18  of a conventional turbocharger  20  via an air intake conduit  22 . The compressor  18  further includes an air inlet  24  coupled to an air intake conduit  26  for receiving fresh air. The turbocharger compressor  18  includes a rotatable wheel (not shown) that is mechanically coupled to one end of a rotatable drive shaft  28  having an opposite end that is mechanically coupled to a rotatable wheel (not shown) of a turbocharger turbine  30 . The turbine  30  includes an exhaust inlet  32  that is fluidly coupled to an exhaust manifold  34  of engine  12  via an exhaust conduit  36 . The turbine  30  further includes an exhaust outlet  38  that is fluidly coupled to ambient via an exhaust conduit  40 . 
     The turbocharger  20  operates in a conventional manner in which exhaust gas produced by the engine  12  and exiting the exhaust manifold  34  is directed through the turbine  30  causing the turbine wheel to rotate. This rotary motion is translated by the drive shaft  28  to the compressor wheel. The compressor wheel is configured in a conventional manner such that rotation of the compressor wheel by the drive shaft  28  draws additional air through the air intake conduit  22  than would otherwise occur in the absence of the turbocharger  20 . In the illustrated embodiment, the operating speed of the turbocharger  20  is thus the rotational speed of the combination of the turbine wheel, the drive shaft  28  and the compressor wheel, which is determined primarily by the flow rate of exhaust gas through the turbine  30 . 
     The system  10  further includes a control circuit  42  that is generally operable to control and manage the overall operation of the engine  12 . The control circuit  42  includes a memory unit  44  as well as a number of inputs and outputs for interfacing with various sensors and systems coupled to the engine  12 . The control circuit  42  is illustratively microprocessor-based, although this disclosure contemplates other embodiments in which the control circuit  42  may alternatively be or include a general purpose or application specific control circuit capable of operation as will be described hereinafter. In any case, the control circuit  42  may be a known control unit sometimes referred to as an electronic or engine control module (ECM), electronic or engine control unit (ECU) or the like. Illustratively, the memory  44  of the control circuit  42  has stored therein one or more sets of instructions that are executable by the control circuit  42 , as will be described in greater detail hereinafter, to estimate the operating speed of the turbocharger  20 , e.g., the rotational speed of the compressor. 
     The control circuit  42  includes a number of inputs for receiving signals from various sensors or sensing systems associated with system  10 . The control circuit  42  is generally operable in a conventional manner to sample the signals produced by the various sensors and/or sensing systems and to process the sampled signals to determine the associated operating conditions. For example, the system  10  includes a pressure sensor  50  that is disposed in fluid communication with the air intake conduit  26 , e.g., at or near the air inlet of the compressor  18 , and that is electrically connected to a compressor inlet pressure input, CIP, of the control circuit  42  via a signal path  52 . The pressure sensor  50  may be of conventional, and is operable to produce a pressure signal on the signal path  52  that is indicative of air pressure at or near the air inlet  24  of the compressor  18 . 
     The system  10  further includes another pressure sensor  54  that is disposed in fluid communication with air intake conduit  22 , e.g., at or near the air outlet of the compressor  18 , and that is electrically connected to a compressor outlet pressure input, COP, of the control circuit  42  via a signal path  56 . The pressure sensor  54  may be of conventional, and is operable to produce a pressure signal on the signal path  56  that is indicative of air pressure at or near the air outlet  16  of the compressor  18 . 
     The system  10  further includes a flow sensor  58  that is disposed in fluid communication with the air intake conduit  26 , e.g., at or near the air inlet of the compressor  18 , and that is electrically connected to a compressor inlet air flow input, CIAF, of the control circuit  42  via a signal path  60 . The air flow sensor  58  may be of known construction, e.g., in the form of a conventional mass air flow sensor, and is operable to produce a flow signal on the signal path  60  that is indicative of a flow rate of air into the air inlet  24  of the compressor  18 . 
     The system  10  further includes a temperature sensor  62  that is disposed in fluid communication with the air intake conduit  26 , e.g., at or near the air inlet of the compressor  18 , and that is electrically connected to a compressor inlet temperature input, CIT, of the control circuit  42  via a signal path  64 . The temperature sensor  62  may be conventional, and is operable to produce a temperature signal on the signal path  60  that is indicative of the temperature at or near the air inlet  24  of the compressor  18 . 
     The system  10  is illustrated in  FIG. 1  and described as including physical sensors producing electrical signals that are indicative of compressor inlet pressure, compressor outlet pressure, compressor air inlet flow rate and compressor inlet temperature. It will be understood, however, that one or more of these parameters may be alternatively or additionally estimated by the control circuit  42  as a function of electrical signals produced by one or more other physical sensors, i.e., sensors other than those positioned and configured to produce signals that correspond to a direct measure of the subject parameter(s). 
     Referring now to  FIG. 2 , a block diagram is shown of one illustrative embodiment of the control circuit  42  of  FIG. 1  configured to estimate the operating speed of the turbocharger  20 . It will be understood that the various functional blocks illustrated in  FIG. 2  represent individual instructions or instruction sets stored in the memory  44  and executable by the control circuit  42  to carry out the corresponding functions as will be described in greater detail hereinafter. Together, the functional blocks illustrated in  FIG. 2  represent one illustrative embodiment of instructions that are stored in the memory unit  44  and executable by the control circuit  42  to estimate the operating speed of the turbocharger  20 . 
     In the illustrated embodiment, the control circuit  42  includes a functional block  100  that receives as inputs the compressor inlet pressure and compressor outlet pressure signals, CIP and COP, produced on the signal paths  52  and  56  respectively. The functional block  100  processes CIP and COP according to a function F 1  to produce a current compressor pressure ratio value, CCPR. In one illustrative embodiment, the function F 1  is given by the equation CCPR=COP/CIP, although this disclosure contemplates other embodiments in which F 1  includes more, fewer and/or different input parameters. 
     The control circuit  42  illustrated in  FIG. 2  further includes another functional block  102  that receives as inputs the compressor inlet pressure signal, CIP, produced on the signal path  52 , the compressor inlet air flow signal, CIAF, produced on the signal path  60  and the compressor inlet temperature signal, CIT, produced on the signal path  64 . The functional block  102  processes CIP, CIAF and CIT according to a function F 2  to produce a compressor-corrected inlet air flow signal, CCIAF, which represents the compressor inlet air flow value, CIAF, corrected for certain operating conditions, i.e., pressure and temperature, at the inlet  24  of the compressor  18 . In one illustrative embodiment, for example, the function F 2  is given by the equation CCIAF=CIAF*SQRT(CIT/T STD )/(CIP/P STD ), where T STD  is a standard reference temperature, e.g., 25° C. or other reference temperature, and P STD  is a standard reference pressure, e.g., 101.3 kPa or other reference pressure. Alternatively, this disclosure contemplates other embodiments in which F 2  includes more, fewer and/or different input parameters. 
     The compressor-corrected inlet air flow value, CCIAF, is provided as an input to another functional block  104  that has stored therein a conventional compressor pressure ratio map corresponding to the specific configuration of the turbocharger  20 . Generally, the compressor pressure ratio map is configured to map CCIAF values to compressor pressure ratio values at a plurality of different turbocharger operating speeds. The functional block  104  is illustratively operable to process CCIAF using the compressor pressure ratio map to generate a number of pairs of compressor pressure ratio and turbocharger operating speed values. 
     Referring now to  FIG. 3 , an example of one such compressor pressure ratio map  120  is shown. In the illustrated embodiment, the compressor pressure ratio map  120  maps compressor-corrected inlet air flow values, CCIAF, to compressor pressure ratio values, CPR, at a plurality of different turbocharger operating speeds, where the contours S 1 -S 9  represent lines of different, constant turbocharger operating speeds. With the map  120 , any one value of CCIAF thus produces a number, M, of different compressor pressure ratio, CPR, and turbocharger operating speed, TS, pairs (CPR, TS) 1 , . . . , (CPR, TS) M , where M may be any positive integer. As one specific example, if CCIAF=0.4 kg/s, the following three compressor pressure ratio and turbocharger operating speed value pairs, P 1 , P 2  and P 3 , are generated: (1.95, S 6 ), (3.0, S 7 ) and (4.1, S 9 ). The functional block  104  illustrated in  FIG. 2  thus processes the CCIAF values using the compressor pressure ratio map stored in the memory  44  to generate a number, M, of pairs of compressor pressure ratio and turbocharger operating speed values, (CPR, TS) 1-M . 
     The current compressor pressure ratio, CCPR, produced by the functional block  100  and the number of pairs of compressor pressure ratio and turbocharger operating speed values, (CPR, TS) 1-M , produced by the functional block  104  are provided as inputs to another functional block  106 . The functional block  106  processes a function of at least two of the (CPR, TS) 1-M  pair values and the CCPR value to produce a compressor-corrected turbocharger operating speed estimate, CCTOS. In one embodiment, for example, two of the (CPR, TS) 1-M  pair values are selected with one pair having a CPR value that is less than CCPR and the other pair having a CPR value that is greater than CCPR, and a conventional interpolation technique is used to determine a CCTOS value that corresponds to CCPR. In embodiments in which the function of the two (CPR, TS) 1-M  pair values is linear, or can be acceptably approximated by a linear function, a conventional linear interpolation technique may be used to determine CCTOS. Alternatively, in embodiments in which the function of the two (CPR, TS) 1-M  pair values is non-linear, a conventional non-linear interpolation technique may be used to determine CCTOS. 
     In another example embodiment, the functional block  106  may be configured to process the number of (CPR, TS) 1-M  pair values to generate a continuous or piece-wise continuous profile of compressor-corrected turbocharger operating speeds as a function of compressor pressure ratios. The profile may illustratively be linear or non-linear. In this embodiment, the functional block  106  is then operable to map CCPR to CCTOS using the generated profile. It will be appreciated that one or more other conventional processing techniques may alternatively be used to process the number of (CPR, TS) 1-M  pair values and CCPR to determine CCTOS, and any such alternate processing techniques are contemplated by this disclosure. 
     The control circuit  42  illustrated in  FIG. 2  further includes another functional block  108  that receives as inputs the compressor inlet temperature signal, CIT, produced on the signal path  64  and the compressor-corrected turbocharger operating speed estimate produced by the functional block  106 . The functional block  108  processes CIT and CCTOS according to a function F 3  to produce an estimate of the actual turbocharger operating speed, TOS. In one illustrative embodiment, for example, the function F 3  is given by the equation TOS=CCTOS*SQRT(CIT/T STD ), where T STD  is as described herein above. The turbocharger operating speed estimate, TOS, is stored in a memory block  110  for use by one or more control algorithms executed by the control circuit  42  and/or external control circuit or system. 
     The algorithm illustrated in  FIG. 2  is continually executed by the control circuit  42  to thereby continually estimate the operating speed of the turbocharger  20  under steady state and transient operating conditions. 
     While the invention has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.