Abstract:
A diagnostic system for a hybrid vehicle comprises a motor control module and a fault diagnostic module. The motor control module controls torque output of an electric motor having a predetermined number of phases. The fault diagnostic module determines a position of a rotor of the electric motor, aligns the rotor with a phase angle of one of the phases, selectively diagnoses a fault based on a current of at least one of the phases, and selectively disables the electric motor based on the diagnosis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/986,414, filed on Nov. 8, 2007. The disclosure of the above application is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates to hybrid vehicles, and more particularly to shutdown path diagnostics for a motor of a hybrid vehicle. 
     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. 
     Referring now to  FIG. 1 , an exemplary electric hybrid vehicle  10  is shown. The electric hybrid vehicle  10  includes an engine assembly  12 , a hybrid power assembly  14 , a transmission  16 , a drive axle  18 , and a control module  20 . The engine assembly  12  includes an internal combustion engine  22  that is in communication with an intake system  24 , a fuel system  26 , and an ignition system  28 . 
     The intake system  24  includes an intake manifold  30 , a throttle  32 , and an electronic throttle control (ETC)  34 . The ETC  34  controls the throttle  32  to control airflow into the engine  22 . The fuel system  26  includes fuel injectors (not shown) to control a fuel flow into the engine  22 . The ignition system  28  ignites an air/fuel mixture provided to the engine  22  by the intake system  24  and the fuel system  26 . 
     The engine  22  is coupled to the transmission  16  via a coupling device  44 . The coupling device  44  may include one or more clutches and/or a torque converter. The engine  22  generates torque to drive the transmission  16  and propel the electric hybrid vehicle  10 . The transmission  16  transfers power from the engine  22  to an output shaft  46 , which rotatably drives the drive axle  18 . 
     The hybrid power assembly  14  includes one or more motor generator units. For example only, as shown in  FIG. 1 , the hybrid power assembly  14  includes two motor generator units: a first motor generator unit (MGU)  38  and a second MGU  40 . The hybrid power assembly  14  also includes a power control device  41  and a rechargeable battery  42 . 
     The first and second MGUs  38  and  40  operate independently and at any given time may each operate as either a motor or a generator. An MGU operating as a motor supplies power (e.g., torque), all or a portion of which may be used to drive the output shaft  46 . An MGU operating as a generator converts mechanical power into electrical power. 
     For example only, the first MGU  38  may generate electrical power based on the output of the engine  22 , and the second MGU  40  may generate electrical power based on the output shaft  46 . Electrical power generated by one of the MGUs  38  and  40  may be used, for example, to power the other of the MGUs  38  and  40 , to recharge the battery  42 , and/or to power electrical components. While the MGUs  38  and  40  are shown as being located within the transmission  16 , the MGUs  38  and  40  may be located in any suitable location. 
     The control module  20  is in communication with the fuel system  26 , the ignition system  28 , the ETC  34 , the MGUs  38  and  40 , the power control device  41 , and the battery  42 . The control module  20  is also in communication with an engine speed sensor  48  that measures an engine speed. For example, the engine speed may be based on the rotation of the crankshaft. The engine speed sensor  48  may be located within the engine  22  or at any suitable location, such as near the crankshaft. 
     The control module  20  controls operation of the engine  22  and the MGUs  38  and  40 . The control module  20  also selectively controls recharging of the battery  42 . The control module  20  controls recharging of the battery  42  and the operation of the MGUs  38  and  40  via the power control device  41 . The power control device  41  controls power flow between the battery  42  and the MGUs  38  and  40 . For example only, the power control device  41  may be an inverter and/or an IGBT (insulated gate bipolar transistor). 
     The control module  20  may include multiple processors for controlling respective operations of the electric hybrid vehicle  10 . For example, the control module  20  may include a first processor for determining desired torque for the engine  22  and the MGUs  38  and  40  and a second processor for controlling torque of each of the MGUs  38  and  40 . 
     SUMMARY 
     A diagnostic system for a hybrid vehicle comprises a motor control module and a fault diagnostic module. The motor control module controls torque output of an electric motor having a predetermined number of phases. The fault diagnostic module determines a position of a rotor of the electric motor, aligns the rotor with a phase angle of one of the phases, selectively diagnoses a fault based on a current of at least one of the phases, and selectively disables the electric motor based on the diagnosis. 
     In further features, the fault diagnostic module determines a positive phase angle and a negative phase angle for each of the phases and aligns the rotor with one of the positive and negative phase angles of one of the phases. 
     In still further features, the fault diagnostic module determines a nearest phase angle based on the position of the rotor and the positive and negative phase angles and aligns the rotor with the nearest phase angle. 
     In other features, the fault diagnostic module aligns the rotor with the phase angle by commanding application of an aligning current to the electric motor based on the position of the rotor and the phase angle. 
     In further features, the fault diagnostic module determines when the rotor is aligned with the phase angle based on a comparison of a measured current through one of the phases and a respective current threshold for the one of the phases. 
     In other features, the current is a normalized current determined for one of the phases. 
     In further features, the fault diagnostic module determines the normalized current based on a first current of the one of the phases measured when the rotor is aligned with the phase angle and a second current of the one of the phases measured over a period after the rotor is aligned with the phase angle. 
     In still further features, the fault diagnostic module diagnoses the fault when the normalized current is greater than a first current threshold. 
     In other features, the fault diagnostic module diagnoses the fault when the normalized current is at least one of less than a second current threshold and greater than a third current threshold, wherein the third current threshold is greater than the second current threshold. 
     In further features, the fault diagnostic module disables operation of the electric motor when the fault is diagnosed. 
     A method for a hybrid vehicle comprises: controlling torque output of an electric motor having a predetermined number of phases; determining a position of a rotor of the electric motor; aligning the rotor with a phase angle of one of the phases; selectively diagnosing a fault based on a current of at least one of the phases; and selectively disabling the electric motor based on the diagnosis. 
     In further features, the method further comprises determining a positive phase angle and a negative phase angle for each of the phases of the electric motor, wherein the aligning the rotor comprises aligning the rotor with one of the positive and negative phase angles of one of the phases. 
     In still further features, the method further comprises determining a nearest phase angle based on the position of the rotor and the positive and negative phase angles, wherein the aligning the rotor comprises aligning the rotor with the nearest phase angle. 
     In other features, the aligning the rotor with the phase angle comprises commanding application of an aligning current to the electric motor based on the position of the rotor and the phase angle. 
     In further features, the method further comprises determining when the rotor is aligned with the phase angle based on a comparison of a measured current through one of the phases and a respective current threshold for the one of the phases. 
     In other features, the current is a normalized current determined for one of the phases. 
     In further features, the method further comprises determining the normalized current based on a first current of the one of the phases measured when the rotor is aligned with the phase angle and a second current of the one of the phases measured over a period after the rotor is aligned with the phase angle. 
     In still further features, the selectively diagnosing the fault comprises diagnosing the fault when the normalized current is greater than a first current threshold. 
     In other features, the selectively diagnosing the fault comprises diagnosing the fault when the normalized current is at least one of less than a second current threshold and greater than a third current threshold, wherein the third current threshold is greater than the second current threshold. 
     In still other features, the selectively disabling comprises disabling operation of the electric motor when the fault is diagnosed. 
     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 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 an exemplary electric hybrid vehicle control system; 
         FIG. 2  is a functional block diagram of an exemplary control module that includes a hybrid control processor and a motor control processor according to the present disclosure; 
         FIG. 3  is an exemplary flow diagram illustrating steps of a method for verifying a first shutdown test according to the present disclosure; and 
         FIG. 4  is an exemplary flow diagram illustrating steps of a method for verifying a second shutdown test according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     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. 
     Referring now to  FIG. 2 , a functional block diagram of an exemplary control module  100  of an electric hybrid vehicle according to the present disclosure is presented. The control module  100  includes a drive diagnostic module  102 , a hybrid control processor (HCP)  104 , and a motor control processor (MCP)  106 . The drive diagnostic module  102  receives various inputs including, but not limited to, engine speed, motor speed, and motor torque. 
     For example, the drive diagnostic module  102  receives the engine speed from the engine speed sensor  48 . The drive diagnostic module  102  also receives a motor speed measured by a motor speed sensor  107  and a motor torque (T mot ) measured by a motor torque sensor  108 . The motor speed sensor  107  and the motor torque sensor  108  measure the speed and torque of the MGU  38 , respectively. As the electric hybrid vehicle  10  includes more than one MGU, the drive diagnostic module  102  may receive the motor speed and torque of more than one MGU. For example, the drive diagnostic module  102  may also receive the motor speed and torque of the second MGU  40 . 
     The drive diagnostic module  102  generates various signals  110  based on the engine speed, the motor speed, and the motor torque. The HCP  104  receives the signals  110  from the drive diagnostic module  102 . The HCP  104  determines a requested motor torque  112  for an MGU based on the received signals  110 . While the HCP  104  is shown as determining the requested motor torque  112  for the MGU  38 , the HCP  104  may determine a requested motor torque for each of the MGUs  38  and  40 . 
     The MCP  106  receives the requested motor torque  112  from the HCP  104  and controls the torque of the first MGU  38  based on the requested motor torque  112 . For example, the MCP  106  may cause power to be supplied to the MGU  38  in an amount that allows the MGU  38  to produce the requested motor torque  112 . In other words, the MCP  106  controls the torque of the MGU  38  based on the requested motor torque  112 . As such, it is desirable to ensure that the torque commanded by the MCP  106  accurately corresponds to the requested motor torque  112 . 
     The control module  100  may include multiple layers of security/diagnostics to ensure accuracy and consistency between the HCP  104  and the MCP  106 . For example, one layer of diagnostics may relate to diagnostics of basic components and subsystems such as voltage and current sensors, temperature sensors, and resolver performance diagnostics. Another layer of diagnostics may relate to an independent calculation of achieved motor torque. This independent calculation of the achieved motor torque may be implemented using separate memory locations for software, calibration variables, and static variables. Values used in the calculation may be verified (e.g., using checksum verification) between different execution loops. 
     Yet another layer of diagnostics may be implemented to prevent software execution and/or processor faults of the MCP  106 . For example only, the control module  100  may include a processor such as a Programming Logic Device (PLD) processor  120 . While the PLD processor  120  is shown as being located external to the MCP  106 , the PLD processor  120  may be located in any suitable location. 
     The PLD processor  120  may send a seed value to the MCP  106 . The MCP  106  determines a return key value based on the seed value and transmits the return key to the PLD processor  120 . The PLD processor  120  determines the functionality of the MCP  106  based on the return key (e.g. by comparing the return key to an expected key). When the return key does not match the expected key, the PLD processor  120  may implement remedial actions. For example, the PLD processor  120  may reset the MCP  106  and put the first MGU  38  into a secure shutdown mode. 
     When a fault is detected, the PLD processor  120  and/or the MCP  106  may initiate a secure shutdown mode for the MGU  38 . A procedure for putting the MGU  38  into the secure shutdown mode may follow one or more shutdown paths. A shutdown path may include a particular sequence of measurements and calculations involving the MGU  38 . While the principles of the present application will be discussed as they relate to the MGU  38 , the principles of the present application are also applicable to the second MGU  40  and/or any other MGU. 
     The control module  100  may perform one or more shutdown path tests to determine whether the secure shutdown mode is functioning properly. For example, the control module  100  may initiate the shutdown path tests at vehicle startup (e.g., at ignition). The shutdown path tests may ensure that the MCP  106  and/or the PLD processor  120  can properly shut down the first MGU  38  when one or more components (e.g., sensors) malfunction and/or when the control module  100  requests a vehicle shutdown. In various implementations, the control module  100  includes a fault diagnostic module  122  that performs the shutdown path tests. 
     Shutdown path tests according to the present disclosure may include, but are not limited to, a Three Phase Short test and a Three Phase Open test. At vehicle startup, the capability of the MCP  106  to conduct one or more of these shutdown tests is verified. Inability to verify the shutdown tests may indicate defects in, for example, the first MGU  38 , power stage, and/or the MCP  106 . 
     The fault diagnostic module  122  may initiate remedial action if it is unable to verify the proper performance of the shutdown tests. For example only, the fault diagnostic module  122  may set a fault code, illuminate an accessory light within the hybrid vehicle, and/or disable operation of the MGU  38 . The fault diagnostic module  122  may disable operation of one of the MGU  38  via the power control device  41 , by disabling the MGU  38  directly, and/or in any other suitable manner. 
     Referring now to  FIG. 3 , a method  200  of verifying the Three Phase Short test begins in step  202 . The method  200  determines a rotor position of a rotor within the first MGU  38  in step  204 . For example only, the rotor position may be determined using a resolver or a rotary encoder. In step  206 , the method  200  determines a nearest phase angle to the rotor position. 
     The first MGU  38  may be operated in a predetermined number of phases, such as three phases (e.g., phases A, B, and C). Each of the phases includes a positive portion (+) and a negative portion (−). For example, for the three phases, the phase angles may be A+, A−, B+, B−, C+, and C−. The nearest phase angle determined in step  206  may be determined based on one of these phase angles. The method  200  commands a d-axis current (i.e., an aligning current) based on the determined phase angle in step  208 . In other words, in step  208  the method  200  commands a current sufficient to align the rotor with the nearest phase angle. 
     The method  200  determines whether the rotor is properly aligned with the nearest phase angle in step  210 . If true, the method  200  continues to step  211 . If false, the method  200  returns to step  208  and continues to control the current until the rotor is properly aligned with one of the phase angles. 
     The method  200  may determine whether the rotor is properly aligned with the nearest phase angle, for example, based on a comparison of currents through each of the phases with a respective threshold. For example only, a first threshold corresponding to the phase with which the rotor is aligned may be set based on the aligning current. A second threshold corresponding to the other two phases (i.e., the phases with which the rotor is not aligned) may be set based on half of the first threshold. In other words, the second threshold may be set based on half of the aligning current. In various implementations, the first and second thresholds may be set based on a predetermined amount or percentage less than the aligning current and half of the aligning current, respectively. The method  200  may determine that the rotor is properly aligned when the phase currents are greater than their respective thresholds. 
     In step  211 , the method  200  measures of the phase currents for each of the phases. The method  200  may also record the phase currents. These phase currents will be referred to as the base phase currents. The method  200  initializes a counter with a value set for the Three Phase Short test in step  212 . For example only, the counter value may be set based on a period of time calibrated based on characteristics of the MGU  38 . The counter value is used to determine the number of iterations of the test. The method  200  determines a PWM duty cycle for the test in step  214 . For example, the PWM duty cycle may be determined to create a short circuit condition of all three phases. 
     In step  215 , the method  200  controls the duty cycle to create the shorted condition in all of the phases. For example only, the method  200  may control the power control device  41  according to the PWM duty cycle. The method  200  sums the respective phase currents in step  216 . The method  200  decrements the counter value in step  218 . In step  220 , the method  200  determines whether the counter value is zero. If true, the method  200  continues to step  221 . If false, the method  200  repeats steps  215  through  220  and repeats summing the respective phase currents. 
     In step  221 , the method  200  calculates respective normalized phase currents for each of the phases. For example only, the method  200  may calculate the normalized phase currents using the equation: 
                 NC   N     =       SC   N       BC   N         ,         
where NC N  is the normalized current of the Nth phase, SC N  is the summed phase current of the Nth phase as determined after the final iteration of step  216 , and BC N  is the base current of the Nth phase as determined in step  211  multiplied by the initial counter value. The method  200  determines whether the respective normalized currents are within a calibrated range in step  222 . If true, the method  200  indicates that the test passed in step  224 . If false, the method indicates that the test failed in step  226 . In other implementations, the method  200  may determine that the test has failed when one or more of the respective normalized currents is greater than or less than a respective calibrated value.
 
     The method  200  may also enable or disable operation of the MGU  38  after steps  224  or  226  are performed, respectively. The method  200  then ends. Alternatively, the method  200  may return to step  202  if the test has failed. For example, the method  200  may allow a predetermined period of time after the test has failed in order to pass the test. 
     Referring now to  FIG. 4 , a method  300  of verifying the Three Phase Open test begins in step  302 . The method  300  determines a rotor position of a rotor within the MGU  38  in step  304 . For example only, the method  300  may determine the rotor position using a resolver or a rotary encoder. In step  306 , the method  300  determines a nearest phase angle to the rotor position. 
     The MGU  38  may be operated in a predetermined number of phases, such as three phases (e.g., phases A, B, and C). Each of the phases includes a positive portion (+) and an negative portion (−). For example, for the three phases, the phase angles may be A+, A−, B+, B−, C+, and C−. The nearest phase angle determined in step  306  may be determined based on one of these phase angles. In step  308 , the method  300  commands a d-axis current (i.e., an aligning current) based on the nearest phase angle. In other words, in step  308  the method  300  commands a current sufficient to align the rotor of the MGU  38  the nearest phase angle. 
     The method  300  determines whether the rotor is properly aligned with the nearest phase angle in step  310 . If true, the method  300  continues to step  311 . If false, the method  300  returns to step  308  and continues to control the current until the rotor is properly aligned with one of the phase angles. 
     The method  300  may determine whether the rotor is properly aligned based on, for example, a comparison of currents through each of the phases with a respective threshold. For example only, a first threshold corresponding to the phase with which the rotor is aligned may be set based on the aligning current. A second threshold corresponding to the other two phases (i.e., the phases with which the rotor is not aligned) may be set based on half of the first threshold. In other words, the second threshold may be set based on half of the aligning current. In various implementations, the first and second thresholds may be set based on a predetermined amount or percentage less than the aligning current and half of the aligning current, respectively. The method  300  may determine that the rotor is properly aligned when the phase currents are greater than their respective thresholds. 
     In step  311 , the method  300  measures of the phase currents of each of the phases. The method  300  may also record the phase currents. These phase currents will be referred to as the base phase currents. The method  300  initializes a counter with a value for the Three Phase Open test in step  312 . For example only, the counter value may be based on a period of time calibrated based on characteristics of the MGU  38 . The counter value is used to determine the number of iterations of the test. 
     In step  315 , the method  300  controls the duty cycle to create an open circuited condition in all of the phases. For example only, the method  300  may control the power control device  41  according to the PWM duty cycle. The method  300  sums the respective phase currents in step  316 . The method  300  decrements the counter value in step  318 . In step  320 , the method  300  determines whether the counter value is zero. If true, the method  300  continues to step  321 . If false, the method  300  repeats steps  315  through  320  and repeats summing the respective phase currents. 
     In step  321 , the method  300  calculates respective normalized phase currents for each of the phases. For example only, the method  300  may calculate the normalized phase currents using the equation: 
                 NC   N     =       SC   N       BC   N         ,         
where NC N  is the normalized current of the Nth phase, SC N  is the summed phase current of the Nth phase as determined after the final iteration of step  316 , and BC N  is the base current of the Nth phase as determined in step  311  multiplied by the initial counter value. The method  300  determines whether the respective normalized currents are each less than a threshold in step  322 . If true, the method  300  indicates that the test passed in step  324 . If false, the method indicates that the test failed in step  326 .
 
     The method  300  may also enable or disable operation of the MGU  38  after steps  324  or  326  are performed, respectively. The method  300  then ends. Alternatively, the method  300  may return to step  302  if the test has failed. For example, the method  300  may allow a predetermined period of time after the test has failed in order to pass the test. 
     Those skilled in the art can now appreciate from the foregoing description that 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.