Abstract:
A vehicle includes a power inverter module (PIM), a motor/generator unit (MGU), vehicle components, temperature sensors, and a controller. The sensors measure temperatures of a motor winding of the MGU, and temperatures of the multiple phase outputs of the PIM. The second plurality of temperature sensors measures temperatures of the vehicle components. The controller calculates an average temperature of the components, and individually diagnoses each temperature sensor using the average temperature. A control circuit for the vehicle includes the first and second plurality of sensors and the controller. A temperature performance diagnostic method includes using the first plurality to measure a temperature of the motor winding and the phase outputs of the PIM, using the second plurality to measure a temperature of the components, calculating an average temperature of the components, and individually diagnosing the performance of each of the first plurality of sensors using the average temperature.

Description:
TECHNICAL FIELD 
     The present invention relates to automated approaches for determining temperature-related characteristics or performance of a vehicle electrical component. 
     BACKGROUND 
     Vehicles are comprised of a host of independent and interdependent systems. Primary and secondary controllers process various signals transmitted by physical sensors to determine the proper functioning of the sensors and related onboard systems. A common cost reduction technique is the replacement of some of the physical sensors with virtual sensors, i.e., software-based estimators or inferred logic values. Virtual sensors may reduce the cost and packaging associated with each physical sensor that is replaced, along with its associated harness, as well as the required sensor diagnostics for the replaced sensor. However, software-based estimators may be less than optimal under certain conditions, e.g., during a sensor redesign or for certain types of high-voltage electrical motor sensors. 
     In a typical hybrid vehicle, diagnostic logic is hardcoded such that every high-voltage power inverter and electric motor combination requires three different phase inverter temperature sensors, which are typically configured as thermistors, and a motor winding thermistor. The diagnostic logic ordinarily must be reprogrammed whenever one of the thermistors is eliminated. As a result, conventional temperature diagnostic logic cannot adequately diagnose more than one severely drifted thermistor. 
     SUMMARY 
     Accordingly, a flexible and modular temperature diagnostic performance algorithm is provided herein for use aboard a vehicle. The algorithm automatically diagnoses the temperature performance of thermistors or other temperature sensors used in conjunction with certain high-voltage electrical components aboard the vehicle. As used herein, the term “diagnose” means to analyze the temperature readings from the sensors to thereby evaluate whether the sensor is properly functioning or operating. The algorithm is modular. That is, the algorithm can properly function under any combination of inverter phase and motor phase winding temperature sensors, with the particular sensor arrangement predefined, e.g., using “sensor present” variables. Moreover, by simply ignoring any temperature sensors that are not present, the algorithm eliminates the need to reprogram the temperature performance diagnostic logic for every sensor change. 
     The algorithm is executable by a motor control processor (MCP) or other designated onboard controller to automatically compare temperature readings from each present inverter phase and motor winding temperature sensor to a calculated average temperature of designated vehicle components, e.g., an average temperature of a high-voltage power electronics cooling loop thermistor and a transmission thermistor in one particular embodiment. Using an average of temperatures taken from two different parts of the vehicle powertrain may help to minimize the skewing effects of any local temperature differences in the calculated average. 
     In particular, a vehicle is provided herein that includes a power inverter module (PIM), an electric motor/generator unit (MGU) that is electrically connected to the PIM and that has a motor winding, and a pair of vehicle components, e.g., a transmission sump or another suitable portion of a transmission and a power electronics cooling loop adapted for cooling the PIM and/or other high-voltage electronics aboard the vehicle. A first plurality of temperature sensors measures a temperature of the motor winding and of different corresponding phase outputs of the PIM. A second plurality of temperature sensors measures a temperature of the vehicle components. An MCP or other designated controller has an algorithm providing a temperature performance diagnostic, with the algorithm calculating an average temperature of the vehicle components, and individually diagnosing the performance of each of the first plurality of temperature sensors using the calculated average temperature. The first and second temperature sensors may be configured as thermistors in one embodiment as set forth herein. 
     A control circuit is also provided for use aboard the vehicle noted above. The circuit includes the first and second plurality of temperature sensors. One of the first plurality of temperature sensors measures a temperature of the motor winding, and each of the remaining sensors of the first plurality measures a temperature of a different corresponding phase output of the PIM. The second plurality of temperature sensors measures a temperature of a corresponding one of the pair of additional vehicle components. An MCP or other designated vehicle controller has an algorithm providing a temperature performance diagnostic, with the algorithm calculating an average temperature of the additional vehicle components, and diagnosing the performance of the first plurality of temperature sensors using the average temperature. 
     A temperature diagnostic method is also provided for use aboard the vehicle. The method may be embodied as an algorithm and executed by the MCP or other controller as noted above. The method includes using the first plurality of temperature sensors to measure a temperature of the motor winding and of the different corresponding phase outputs of the PIM, and using a second plurality of temperature sensors to measure a temperature of the vehicle components. The method further includes calculating an average temperature of the vehicle components, and individually diagnosing the performance of each of the first plurality of temperature sensors using the average temperature. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a vehicle having a temperature performance diagnostic algorithm in accordance with the present invention; and 
         FIG. 2  is a flow chart describing the temperature performance diagnostic algorithm usable with the vehicle shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numbers correspond to like or similar components throughout the several figures, a vehicle  10  is shown in  FIG. 1  having a temperature performance diagnostic algorithm  100 . The vehicle  10  may be configured as any vehicle having one or more electric motor/generator units (MGU) and a three-phase power inverter as explained below, e.g., a hybrid electric vehicle (HEV), a plug-in HEV (PHEV), a battery electric vehicle (BEV), an extended-range HEV (EREV), etc. 
     In one embodiment, the vehicle  10  may include an internal combustion engine  12  and respective first and second MGUs, i.e., MGU  14 A and  14 B. Depending on the vehicle configuration, one of the MGUs, for example MGU  14 A, may be used to selectively crank and start engine  12  as part of a belt alternator-starter or BAS system, while the second MGU  14 B can be used to assist the engine in propelling the vehicle  10 , or to propel the vehicle when the engine is off to thereby provide an electric-only (EV) operating mode. Other single or multi-MGU configurations of the vehicle  10  are possible without departing from the intended scope, including EV configurations that do not require an engine. 
     Controllers  16 A,  16 B are electrically connected to the MGUs  14 A and  14 B, respectively, and are programmed to control the functionality of the corresponding MGU. Each controller  16 A may also be programmed with or provided access to algorithm  100 , the execution of which provides a temperature performance diagnostic tool as described below. In one embodiment, controllers  16 A,  16 B are dependent secondary controllers (C 2 ), e.g., motor control processors (MCP) rather than high-level or primary controller (C 1 )  18 , e.g., a hybrid control processor (HCP) as understood in the art, although the algorithm  100  may be executed or values stored by other controllers aboard the vehicle  10  if so desired. Controllers  16 A,  16 B are in communication with the controller  18 , and may be adapted to transmit diagnostic information or test results to the controller  18  for generation of a diagnostic code as set forth below. 
     Vehicle  10  further includes a transmission  20  having an input member  22  and an output member  24 . A driveshaft  26  of engine  12  may be selectively connected to input member  22  via a clutch  28 . Transmission  20  may be configured as an electrically-variable transmission (EVT) or any other suitable transmission capable of transmitting torque to drive wheels  30  via the output member  24 . 
     Still referring to  FIG. 1 , each MGU  14 A,  14 B may be configured as multi-phase electric machines rated for approximately 60 VAC to approximately 300 VAC or more depending on the required design. Each MGU  14 A,  14 B may be electrically connected to a high-voltage energy storage system (ESS)  25  via a high-voltage direct current (DC) power bus  29 , a power inverter module (PIM)  32  having multiple phase outputs connecting to the MGUs  14 A,  14 B as shown, and a high-voltage alternating current (AC) power bus  29 A. The ESS  25  may be selectively recharged, for example by capturing energy via the MGU  14 B during a regenerative braking event. 
     The vehicle  10  may further include an auxiliary power module (APM)  34 , e.g., a DC-DC power converter, which is electrically connected to the ESS  25  via the DC power bus  29 . The APM  34  may also be electrically connected to an auxiliary battery (AUX)  35 , e.g., a 12-volt DC battery, via a low-voltage power bus  19 , and adapted for energizing one or more auxiliary systems aboard the vehicle  10 , as is well understood in the art. 
     Controllers  16 A,  16 B may be integrated into a single vehicle control device or configured as a distributed vehicle control device in electrical communication with each of the MGUs  14 A,  14 B. Control connections may include any required transfer conductors, e.g., a hard-wired or wireless control link(s) or path(s) suitable for transmitting and receiving the necessary electrical control signals for proper power flow control and coordination aboard the vehicle  10 . The controllers  16 A,  16 B may include such control modules and capabilities as might be necessary to execute all required diagnostic functionality aboard the vehicle  10 . 
     Controllers  16 A,  16 B, and  18  may be configured as a digital computer having a microprocessor or central processing unit, read only memory (ROM), random access memory (RAM), electrically-erasable programmable read only memory (EEPROM), high speed clock, analog-to-digital (A/D) and digital-to-analog (D/A) circuitry, and input/output circuitry and devices (I/O), as well as appropriate signal conditioning and buffer circuitry. Any algorithms resident in the designated controllers  16 A,  16 B, including the algorithm  100  as described below with reference to  FIG. 2 , can be stored in ROM and automatically executed by the controller to provide the respective functionality. 
     Still referring to  FIG. 1 , the vehicle  10  includes a control circuit  50 , which in addition to the MGUs  14 A,  14 B and PIM  32 , is comprised of the controllers  16 A and/or  16 B, a first set of temperature sensors, referred to hereinafter as internal temperature sensors  36 , and a second set of temperature sensors, referred to hereinafter as external temperature sensors  38 . As used herein, the term “internal” refers to the internal position of a given sensor with respect to certain designated electrical components aboard vehicle  10 , with the sensors  36  each adapted for measuring or determining, either directly or indirectly, a temperature of the associated electrical component. 
     In one embodiment, the internal temperature sensors  36  are thermistors, i.e., temperature-variable resistors usually constructed of ceramic or polymer materials. As will be well understood by those of ordinary skill in the art, thermistors are non-linear semi-conductive devices configured to determine a temperature of an associated device based on a changing resistance value. The thermistors used as sensors  36  may be, in one possible embodiment, positive-temperature coefficient (PTC)-type thermistors, although the sensors can also be configured as thermostats, resistance temperature detectors (RTDs), thermocouple devices, or other temperature sensing devices. 
     Internal temperature sensors  36  may be electrically connected with the end turns or windings of each MGU, e.g., the MGU  14 A and/or MGU  14 B in the embodiment shown in  FIG. 1 , as well as within each power inverter used aboard the vehicle  10 . For example, the PIM  32  may include three internal temperature sensors  36 , i.e., one per phase transmitted via the AC power bus  29 A. The sensors  36  are shown in simplified schematic form as single boxes, although the actual number and placement of the sensors may vary. 
     The external temperature sensors  38  may be likewise configured as PTC-type thermistors or any other suitable temperature-sensing device. The term “external” as used herein refers to the relative placement of the sensors  38  with respect to the particular electrical components being diagnosed. The external temperature sensors  38  should be placed at sufficiently different locations within the powertrain of vehicle  10 , such that an average reading taken from the various external locations will minimize the effect of local temperature differences on any calculated values. 
     In one embodiment, the sensors  38  may be placed within a power electronics cooling loop  40 , within the transmission  20 , e.g., within a fluid sump, or at other suitable locations. While shown schematically in  FIG. 1  for simplicity, those of ordinary skill in the art will recognize that the cooling loop  40 , like any cooling loop adapted for cooling high-voltage electronics, may be configured as a pump-driven coolant loop adapted for alternately absorbing and radiating heat generated by the various high-voltage electronics aboard vehicle  10 . 
     Referring to  FIG. 2 , algorithm  100  begins at step  102 , wherein a set of enable conditions are initially checked via the designated controller(s), e.g., controllers  16 A and/or  16 B, to determine whether execution of the algorithm is required. If execution is not required, then the algorithm  100  repeats step  102  in a loop until the enable requirements are properly satisfied, at which point the algorithm proceeds to step  104 . 
     For compliance purposes, step  102  may optionally increment a denominator value to track a total count of the number of times the algorithm  100  could have been executed. The denominator value may then be used with a numerator value to calculate an in-use ratio as explained below with reference to step  104 . Possible enablement conditions may include, but are not limited to, a threshold minimum temperature for running the algorithm  100  to completion, a minimum off-time of the propulsion components of vehicle  10 , an absence of thermistor range faults, etc. 
     At step  104 , having determined at step  102  that the enablement conditions are satisfied, a calibrated startup delay may be executed, for example by initiating a digital timer. The delay may allow sufficient time to elapse for the completion of range checks of the internal temperature sensors  36 , e.g., resistance range checks when the sensors  36  are configured as thermistors. When the calibrated elapsed time has passed, the algorithm  100  proceeds to step  106 . 
     Step  104  may optionally include incrementing a numerator value for the compliance determination noted above. For example, the numerator value can record how often the algorithm  100  actually ran versus how often it could have run, i.e., the denominator value noted above in step  102 , to establish the in-use ratio, such as a ratio of 0.336 as required for compliance in certain jurisdictions. 
     At step  106 , temperature measurements are collected from the remote temperature sensors  38 , and an average temperature value (  T 38   ) is calculated using these values. The algorithm  100  then temporarily records the average in memory and proceeds to step  108 . 
     At step  108 , temperature measurements are collected from each of the internal temperature sensors  36 , with these readings represented generally as T 36  in  FIG. 2 . Any sensors that are not present, either by reason of malfunction, redesign, maintenance, or otherwise, are simply ignored. Step  108  may include setting a corresponding “sensor present” flag to 1 when a sensor reading is present, and to 0 otherwise. The algorithm  100  proceeds to step  110  when collection of readings T 36  is complete. 
     At step  110 , each of the readings T 36  is compared to the average temperature value (  T 38   ) determined at step  106 . A localized pass/fail determination is made at step  110 , and the result temporarily stored in memory. The algorithm  100  then proceeds to step  112 . 
     Even if the diagnostic fails on the present loop, a diagnostic code may not be set immediately. Instead, a separate routine may be executed to make the diagnostic pass/fail decision. A calibrated X-count (i.e., a fail count) and Y-count (i.e., a sample count) threshold are referenced. The diagnostic may be set such that it must fail X times before Y samples have accrued in order to generate a “diagnostic fail” result. That is, as soon as X fail samples have accumulated, the test will fail, provisionally, but the logic will not formally declare the result until Y sample counts have accumulated. 
     On each loop, it is determined whether a corresponding sample count (Y), a fail count (X), both, or neither should increment for each internal temperature sensor  36 . Then, the logic increments the necessary counters and makes a formal diagnostic pass, fail, or undetermined decision. The algorithm  100  then proceeds to step  112 . 
     At step  112 , an action may be taken based on the result of step  110 . For example, if a fail decision is formally made, the designated controller, e.g., controller  16 A or  16 B, may tell the controller  18  to set a diagnostic code via a serial peripheral interface or SPI message or other suitable means before any subsequent default action is executed. Suitable sensor maintenance steps may then be performed as needed to correct the failing result. 
     Execution of algorithm  100  as set forth above may provide certain performance-related benefits relative to conventional temperature diagnostic methods. For example, typical hybrid vehicle diagnostics are closed systems that rely on the presence of all three inverter phase thermistors, as well as the presence of the motor winding thermistor. In such conventional systems, all thermistors provide temperature values that are compared to a calibrated reference temperature, with the absolute difference between the individual thermistor and the reference temperature calculated and compared to a calibrated delta value. Pass/fail is determined based on this delta comparison alone. Values from each of the temperature sensors in the circuit, whether properly functioning or not, are each considered as part of the temperature average, and therefore complex comparison logic is required to determine if the average is skewed. Resultant limits are placed on the number of failed or drifted sensors. 
     Also, as noted above, all three inverter sensors and the motor winding thermistor must be present in conventional diagnostic systems. By comparison, algorithm  100  of  FIG. 2  will not become invalid if more than one inverter sensor is stuck in range, and the need for complex comparison logic noted above is avoided entirely. Moreover, algorithm  100  can be used for any configuration of inverter and motor winding sensors. As noted above, a secondary controller such as controllers  16 A or  16 B may host the calculation and storage functions, unlike conventional methods which transmit calculated values to the primary controller, e.g., an HCP, via SPI for storage in the HCP. Therefore, HCP utilization and SPI bandwidth may be optimized using the present approach. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.