DE102014204803B4 - Control strategy for an electric machine in a vehicle - Google Patents

Abstract

A method for controlling a hybrid electric vehicle (10), comprising: deactivating an electric machine (16) and a variable voltage converter (WC, 60) when the voltage of the electric machine (16) exceeds an overvoltage threshold (714); and once it is determined that the voltage of the electric machine (16) has decreased to at least a second threshold lower than the overvoltage threshold (714), reactivating the electric machine (16); and setting the VVC (60) to a normal mode of operation.

Description

The present disclosure relates to a system for controlling an electric machine in an electric vehicle.

Battery electric vehicles (BEVs) include a traction battery that is rechargeable from an external electrical power source and powers the electric machine. Hybrid electric vehicles (HEVs) include an onboard internal combustion engine, one or more electric machines, and a traction battery that at least partially powers the electric machine. Plug-in hybrid electric vehicles (PHEVs) are similar to HEVs, but the traction battery in a PHEV can be charged from an external electrical power source. These vehicles are examples of vehicles that can be at least partially propelled by an electric machine.

If a failure of a component that is necessary for the electric drive is determined, then several actions may be necessary in these vehicles to ensure the safety of the vehicle occupants. Because shutting down the entire vehicle may be undesirable, restricted operating strategy (LOS) modes may be implemented to allow the vehicle operator to continue driving while individual components are disabled. DE 10 2011 079 082 A1 shows a power converter circuit comprising a variable voltage converter (VVC) with a means for stabilizing the output voltage thereof. The means for stabilizing may take the form of a diode which clamps the WC output voltage to the WC input voltage such that the output voltage does not drop below the input voltage when a load causes a sudden power demand. The means for stabilizing also enables a bypass mode in which pass-through power can be provided from a power source to an inverter without current flowing through the inductor or switches of the VVC. When embodied as a diode, the stabilizing means can increase the maximum power that can be transferred by the power converter circuit, improve the transient performance of the circuit, minimize control instability, and reduce power losses. U.S. 6,405,818 B1 discloses a hybrid electric vehicle having a propulsion system that includes an internal combustion engine, a generator/motor, and an electric motor or “traction inverter module” that together provide power to the vehicle's powertrain. The vehicle includes a controller capable of detecting when any of the torque-producing subsystems (eg, engine, generator/motor, and/or motor) are at fault and when one or more faults are present to provide a constrained operational strategy that allows the vehicle to be drivable using the remaining operational subsystem(s). DE 10 2013 216 756 A1 FIG. 1 shows a hybrid electric vehicle method for controlling a hybrid electric vehicle. The vehicle contains a traction battery, at least two electric machines and a controller. The controller is configured to, in response to a fault condition of one of the electric machines during a drive time, command the other electric machine to operate in a mode in which torque output is limited to a battery voltage dependent threshold to maintain vehicle propulsion during the drive time remains.

According to one or more embodiments of the present disclosure, a method for controlling a hybrid electric vehicle is provided. The method includes disabling an electric machine and a variable voltage converter (VVC) when the voltage of an electric machine exceeds an over-voltage threshold. If it is determined that the electric machine voltage has decreased to at least a second threshold that is lower than the overvoltage threshold, the electric machine is reactivated and the VVC is set to a normal operating mode.

In a further specific embodiment, the method also includes switching the electrical machine back on during the driving cycle.

In another embodiment, in the method, disabling the VVC switches the toilet to a restricted mode of operation, wherein the restricted mode of operation allows the vehicle to maintain vehicle propulsion during the drive cycle.

In another embodiment, the method further includes commanding the WC to run in a high voltage mode from a high voltage electrical terminal to the battery to quickly drain high voltage in response to the overvoltage fault.

In another embodiment, in response to the overvoltage fault, the WC is set to a mode that prevents a boost voltage from being provided to the at least one electric machine.

According to one or more other embodiments of the present disclosure provided an electric vehicle having a traction battery, at least one electric machine, and a variable voltage converter (VVC). The electric vehicle includes at least one controller configured to determine an overvoltage fault when voltage of an electric machine exceeds an overvoltage threshold. In response to the overvoltage fault, the electric machine and VVC are disabled. If it is determined that the voltage of the electric machine has dropped to at least one safety threshold that is lower than the overvoltage threshold, the controller is configured to switch the VVC to a restricted operating mode. Upon determining that the electric machine voltage has decreased to at least a third threshold lower than the safety threshold and the overvoltage threshold, the controller is configured to reactivate the electric machine and set the VVC to a normal operating mode. The limited operating mode allows the vehicle to maintain vehicle propulsion throughout the drive cycle while the electric machine recovers from a transient condition that triggered the overvoltage fault.

In a further embodiment, the electrical machine includes at least one inverter, the overvoltage fault occurring at the at least one inverter.

In another embodiment, the overvoltage fault occurs across at least one insulated gate bipolar transistor (IGBT).

In another embodiment, the electric vehicle includes an inverter and the controller is also configured to command the toilet to run in a shunt mode where voltage is passed from the inverter to the battery while the electric machine is disabled.

In a further specific embodiment, the at least one control device is also configured to reactivate the failed electric machine during the driving cycle.

According to one or more embodiments of the present disclosure, a method for controlling a hybrid electric vehicle is provided. The method includes determining an overvoltage fault when the voltage of an electric machine exceeds an overvoltage threshold. The electric machine is disabled in response to the overvoltage fault. If it is determined that the voltage of the electric machine has dropped to at least a safety threshold that is lower than the overvoltage threshold, a variable voltage converter (WC) is switched to a limited operating mode. If it is determined that the electric machine voltage has dropped to at least a third threshold lower than the safety threshold and the overvoltage threshold, the electric machine is reactivated and the VVC is set to a normal operating mode. The limited operating mode allows the vehicle to maintain vehicle propulsion throughout the drive cycle.

• 1 ist ein Schaltbild eines Hybridelektrofahrzeugs gemäß einer Ausführungsform der Offenbarung;
• 2 ist ein Blockdiagramm, das ein Beispiel für ein Steuersystem des Fahrzeugs aus 1 veranschaulicht;
• 3 ist ein Schaltbild eines Teils des Fahrzeugs aus 1;
• 4 ist ein Schaltbild eines variablen Spannungswandlers (VVC) aus 3;
• 5 ist ein Flussdiagramm eines Algorithmus, der in einem Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 6 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 7 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 8 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 9 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 10 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;
• 11 ist ein Diagramm, das eine Systemantwort- und -behebungsstrategie des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung zeigt;
• 12 ist ein Flussdiagramm eines weiteren Algorithmus, der im Steuersystem des Fahrzeugs aus 1 gemäß einer Ausführungsform der Offenbarung umgesetzt wird;

In another embodiment, in response to the overvoltage fault, the VVC is set to a mode that prevents a boost voltage from being supplied to the at least one electric machine.

• 1 12 is a schematic diagram of a hybrid electric vehicle according to an embodiment of the disclosure;
• 2 12 is a block diagram showing an example of a control system of the vehicle 1 illustrated;
• 3 Figure 1 is a schematic of a portion of the vehicle 1 ;
• 4 Figure 12 is a circuit diagram of a variable voltage converter (VVC). 3 ;
• 5 FIG. 12 is a flowchart of an algorithm implemented in a vehicle control system 1 implemented according to an embodiment of the disclosure;
• 6 Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;
• 7 Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;
• 8th Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;
• 9 Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;
• 10 Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;
• 11 Figure 12 is a diagram showing a vehicle's system response and recovery strategy 1 according to an embodiment of the disclosure;
• 12 Figure 12 is a flow chart of another algorithm implemented in the vehicle's control system 1 implemented according to an embodiment of the disclosure;

Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be enlarged or minimized to show details of specific components. Therefore, specific structural and functional details disclosed herein are not to be taken as limiting, but merely as an illustrative basis for teaching those skilled in the art to variously employ the present invention. As those skilled in the art will appreciate, various features illustrated and described with respect to any of the figures may be combined with features illustrated in one or more other figures to yield embodiments not explicitly illustrated or described. The combinations of features illustrated represent representative embodiments of typical applications. However, various combinations and modifications of the features in accordance with the teachings of this disclosure may be desirable for particular applications or implementations.

In 1 A hybrid electric vehicle 10 with a power-split drive train is shown. A vehicle control system 12 is provided and may generally be referred to as a controller. The vehicle control system 12 controls the power distribution in the powertrain or power unit of the vehicle 10.

The vehicle 10 includes a traction battery 14. The battery 14 has a two-way electrical connection such that the battery 14 receives and stores electrical energy through regenerative braking, for example. The battery 14 also provides power to an electric machine, such as an electric traction motor 16 .

Although the control system 12 of the vehicle 10 in 1 Illustrated as a single controller, such a control system may include more than one controller if desired. For example, a separate battery control module can control the battery 14 directly. In addition, a separate engine control module may be connected directly to the engine 16 and to the other control devices in the vehicle 10 . It should be understood that any controller provided in the vehicle 10 may be referred to as a “controller” and that the vehicle control system 12 is not necessarily limited to just one controller. Separate further control devices and their hierarchy are in 2 described in more detail.

An inverter 15 is provided to convert direct current from the battery to alternating current for driving the electric machine. The inverter 15 can also selectively enable/disable electrical power from the battery 14 to the motor 16 . Alternatively, the inverter 15 may convert AC power from the electric machine to DC power during regenerative braking such that the electrical power is stored in the battery 14 .

An internal combustion engine 18 also provides a source of power for the vehicle 10. The vehicle control system 12 controls the operation of the engine 18. Both the engine 16 and the engine 18 are capable of driving a transmission 20, which ultimately provides torque to the wheels of the Vehicle 10 supplies.

The engine 18 provides power to a torque input shaft 22 that is connected to a planetary gear set 24 via a one-way clutch. The input shaft 22 drives the planetary gear set 24 . The planetary gear set 24 includes a ring gear 26, a sun gear 28, and a planetary carrier assembly 30. The input shaft 22 may be drivably connected to the carrier assembly 30 which, when driven, may rotate the ring gear 26 and/or the sun gear 28. The sun gear 28 can be drivably connected to a generator 32 . The generator 32 may be engaged with the sun gear 28 such that the generator 32 rotates with the sun gear 28 or may be disengaged such that the generator 32 does not rotate with the sun gear 28 . Like the engine 16, the generator 32 may be referred to as an electric machine capable of both generating electrical energy and providing motive power when used with other vehicle powertrain configurations.

When the engine 18 is drivably connected to the planetary gear set 24, the generator 32 generates power in response to the operation of the planetary gear set 24. Electrical power generated by the generator 32 is transmitted to the battery 14 via electrical connections 36. FIG. The battery 14 also receives and stores electrical energy from regenerative braking solution in a known manner. The battery 14 provides the stored electrical energy to the motor 16 for operation. The part of the energy that is provided by the engine 18 for the generator 32 can also be transferred directly to the engine 16 . The battery 14, engine 16 and generator 32 are interconnected by electrical connections 36 in a branch path electrical current path. The vehicle control system 12 controls the components in the powertrain to provide the appropriate torque distribution to the wheels.

It is understood that the engine 16 and the generator 32 can both be referred to as an electric machine. Any electric machine can operate as a generator by receiving torque from engine 18 and providing AC voltage to inverter 15 , where inverter 15 converts the voltage to DC voltage to charge battery 14 . Each electric machine can also operate as a generator, using regenerative braking to convert vehicle braking energy into electrical energy to be stored in the battery 14 . Alternatively, each electric machine can operate as a motor, with the electric machine receiving power from the inverter 15 and battery 14 and providing torque through the transmission 20 and ultimately to the wheels 58 .

Inverter 15 drives motor 16 and generator 32 selectively. Inverter 15 may include a motor inverter for selectively disabling motor 16 and a generator inverter for selectively disabling generator 32 .

The vehicle 10 may also include a variable voltage converter (WC) 60, also referred to as a boost converter, to vary the voltage between the battery 14 and the motor 16 and generator 32. The WC 60 is used to boost the voltage of the battery 14 to a higher voltage. The higher voltage in a hybrid electric powertrain system can be used for multiple purposes, such as optimizing torque capacity for electric machines, system loss optimization, and other hybrid electric system optimizations. The VVC 60 allows a smaller, lower voltage battery pack to be used in the vehicle 10 while retaining the functionality associated with the higher voltage. A smaller battery pack can have advantages such as lower cost, smaller size, and fewer packaging constraints. The WC 60 will be in 3 and 4 described in more detail.

Vehicle 10 may be powered by engine 18 alone, engine 18 and generator 32 alone, battery 14 and engine 16 alone, or a combination of engine 18, battery 14, engine 16, and generator 32 . In a mechanical drive mode, or a first mode of operation, the motor 18 is activated to provide torque through the planetary gear set 24 . Ring gear 26 distributes torque to transmission gears 38 which include meshing gear members 40, 42, 44 and 46. Gears 42, 44 and 46 are mounted on a countershaft, and gear 46 transfers torque to gear 48. Gear 48 then transfers torque to a torque output shaft 50. In mechanical drive mode, motor 16 can also be activated to assist the engine 18 in driving the transmission 20. When the engine 16 is actively assisting, the wheel 52 transmits torque to the wheel 44 and countershaft.

In an electric drive (EV) mode, or a second mode of operation, the motor 18 is disabled or otherwise prevented from transmitting torque to the torque output shaft 50 . In EV mode, the battery 14 powers the motor 16 to transmit torque through the transmission gears 38 and to the torque output shaft 50 . The torque output shaft 50 is connected to a differential and axle mechanism 56 that transmits torque to the drive wheels 58 . The vehicle control system 12 controls the battery 14, motor 16, motor 18, and generator 32 to transmit torque to the wheels 58 in either mechanical drive mode or EV mode according to driver torque requests.

As described above, there are two power sources for the drive unit. The first source of energy is the engine 18 which provides torque to the planetary gear set 24 . The other source of energy relates only to the electric propulsion system, which includes the engine 16, the generator 32 and the battery 14, with the battery 14 serving as an energy storage medium for the generator 32 and the engine 16. The generator 32 may be operated by the planetary gear set 24 and alternatively serve as a motor and provide power to the planetary gear set 24 .

It should be understood that while the vehicle 10 is illustrated as having a split powertrain, the vehicle 10 may include numerous other configurations. In this regard, it is envisaged that individual components of the powertrain will vary to suit different specific applications. For example, in another configuration that does not include planetary gear set 24, an electric machine (motor/generator) may be provided that serves as a generator by receiving torque from the engine or regenerative braking, while the same electric machine may also serve as a motor by receiving energy from the traction battery and providing torque through the gearbox. Other vehicle configurations of vehicle powertrains and electric machine designs are also contemplated and thus considered within the scope of the present disclosure.

In 2 1 is a block diagram illustrating a vehicle control system 12 in the vehicle 10 . A driver inputs a request 62, for example by pressing the accelerator pedal to input an acceleration request or by pressing the brake pedal to input a braking request. The driver inputs 62 are received by a vehicle systems controller (FSS) 64 . The FSS 64 processes these driver inputs 62 and transmits commands through the vehicle 10.

The vehicle control system 12 may be electrically connected to various subsystems within the vehicle 10 and serve as the overall controller of the vehicle 10. The VSS may be electrically connected to and communicate with various subsystems via a vehicle network 65. The vehicle network 65 continuously transmits data and information to the vehicle-based systems. The vehicle network 65 may be a controlled area network (CAN) bus used to transfer data to and from FSS 64 and other various control devices or subsystems or components thereof. As in 2 For example, as shown, the FSS 64 may be connected to a hybrid control device (HSV) 66 , a battery control module (BSM) 72 , and an engine control unit (MCU) 68 via the vehicle network 65 .

The HSV 66 controls the hybrid-specific components of the vehicle 10, such as the engine 16, alternator 32, battery 14, and/or inverter 15. The HSV 66 is in communication with the MSE 68 so that the HSV 66 can command the MSE 68 to control the engine 18 in a variety of ways. A battery control module (BSM) 72 can also communicate with the HSV 66 . The BSM 72 can receive commands from the HSV 66 and controls the power distribution of the battery 14.

The HSV 66 is also in communication with a motor/generator control unit (MGSE) 70. The MGSE 70 communicates with the HSV 66 through a single peripheral interface (SPI) 71. The SPI 71 is a four wire serial bus. The SPI 71 is an extremely simple hardware interface and is not limited to any particular maximum clock speed, allowing for potentially high throughput. The MGSE 70 receives commands from the HSV 66 and controls the engine 16, generator 32 and WC 60. As in FIG 2 Also shown, MGCE 70 is in communication with inverter controllers 74. Motor/generator inverter controllers 74 receive commands from MGCE 70 and open and close switches in inverter 15 to enable and disable the flow of power to and from the electric machines.

Previous hybrid electric vehicles used only one control module to control the engine, alternator, and VVC. Within the control module, one microcontroller was used to control the motor and another microcontroller to control the alternator, while a third microcontroller controls the VVC. However, the VVC proved difficult to control when it was disconnected from the motor/generator and it proved too slow in transferring information from the motor or generator to the VVC controllers in the HSV. It is therefore advantageous to control the VVC, the motor, the generator and the corresponding inverters from a control device, e.g 2 shown MGSE.

Therefore, in the representation in 2 a hierarchy of controllers is provided. Other hierarchies of controllers are contemplated without departing from the scope of the present disclosure. For example, the FSS 64 can communicate directly with the MGSE 70 without an HSV 66 being present. Other configurations are also envisaged that may benefit various specific vehicle architectures.

The vehicle control system 12 controls the individual control devices according to the requested torque and power demand. Again, it is understood that more or fewer controllers than described herein are also provided, and that one or more of those controllers may communicatively cooperate to perform particular tasks. Any and all of these controllers, or combinations thereof, may be referred to simply as a "controller."

With reference to 3 and 4 A circuit diagram of a portion of a hybrid electric vehicle 10 and vehicle control system 12 will now be described in greater detail. As explained above, the VVC 60 is in communication with and controlled by the MGSE. In addition, the VVC 60 is connected to the motor/generator inverter controllers 74 . More specifically, the WC 60 is used to boost the voltage of the battery 14 in an HEV powertrain system to a higher voltage value for a number of purposes, including but not limited to electric machine torque capacity optimizations and system loss optimizations.

The battery 14 is connected to the VVC 60 along an input side 76 . The battery 14 provides a low voltage to the WC 60 . The VVC 17 then boosts the low voltage from the battery 14 to a higher voltage and outputs the higher voltage on an output side 78 . The output side 78 of the WC 60 provides the high voltage to the high voltage bus 36 for use by the inverter 15 and then by the motor 16 and generator 32 . As in 3 shown, the motor 16 and the generator 32 can each have a separate inverter 15 . While the WC 60 is described as having an input side and an output side, it should be noted that in a locomotion mode the path is from the battery through the VVC to the high voltage bus. In a regeneration mode, on the other hand, the path is reversed.

A sensor 80 is located between the battery 14 and the VVC to measure the voltage signal across the input side 76 of the VVC 60 . More specifically, the sensor 80 provides a voltage signal indicative of the voltage from the battery 14 . A second sensor 82 is located along the output side 78 between the WC 60 and the inverters 15. The sensor 82 provides a signal indicative of the voltage on the high voltage bus 36. FIG. The sensors 80, 82 provide a signal indicative of the measured tension along the input side 76 and output side 78, respectively. Under normal operating conditions, the measured voltage signal from the sensors 80, 82 is within a suitable specified range. However, if the measured voltage signal from the sensors deviates from the appropriate specified range, this may indicate that a fault has occurred or that one of the sensors 80, 82 has failed.

In 4 A schematic of the VVC 60 circuitry is shown. The VVC 60 generally consists of an inductor 84, two power switches 86 and 88, and associated gate drive circuitry 90, as in FIG 4 you can see. The two power switches 86, 88 consist of an insulated gate electrode (IGBT) 92 and an anti-parallel diode 96. As in FIG 4 the switches are shown arranged as top switch 86 and bottom switch 88 . There are also several IGBTs 92 associated with the inverter 15, for the motor 16 and for the generator 32, respectively, as in FIG 4 you can see.

The circuitry of the WC 60 allows current to flow in two directions depending on the needs of the vehicle, such as propulsion or regeneration. For example, when upper switch 86 is closed and lower switch 88 is open, power flows in one direction through anti-parallel diode 96. Similarly, when upper switch 86 is open and lower switch 88 is closed, power flows in one direction direction through the anti-parallel diode 96. However, when both the upper switch 86 and the lower switch 88 are closed, current flows in both directions and produces a voltage boost. The generated boosted voltage is output to the inverter 15 which controls the motor 16 and the generator 32 . As discussed previously, by allowing a voltage rise through the VVC 60, a smaller battery pack can be used in the vehicle, saving cost and battery packaging space.

Certain fault conditions may be detected by one or more of the controllers indicating a fault in one of the powertrain components, such as the engine 16, alternator 32, VVC 60, or inverter 15. If a failure is detected in one of the components, a restricted operating strategy (LOS) can be implemented to allow the vehicle operator to continue driving while certain individual components are disabled. This prevented the vehicle 10 from shutting down completely, which may be undesirable for drivers. The fault conditions that may cause the vehicle 10 and/or vehicle control system 12 to enter a LOS mode may include powertrain component temperature, current, and/or voltage levels outside of an acceptable threshold. A fault condition may be caused by a transient event and may be short-lived; however, reading a value outside of a threshold may result in the vehicle control system 12 commanding individual shutdown of the affected component while simultaneously commanding a LOS mode to allow the vehicle 10 operator to continue driving.

In 5 an embodiment of the LOS mode is shown as 100 . Diagnostics are performed on the engine 16, generator 32, WC 60 and inverter 15 associated with each of the electric machines. the diag nose determines whether LOS mode is necessary and should command a temporary disablement of this device. The MGSE 70 begins performing the diagnostics as shown in block 102 . Next, as represented in block 104, it is determined whether or not a fault condition exists in the motor and/or motor-inverter. If such an error condition exists, a LOS counter is incremented, as shown in block 106. The LOS counter can be a one-digit counter or an identifier. Once the LOS counter has been incremented by one, as represented by block 108, a temporary engine disable is flagged as TRUE. The engine is commanded to deactivate as shown in block 110 . The motor can be disabled by opening switches in the motor inverter or by opening another switch associated with the motor.

If no fault condition exists in the motor and/or motor-inverter, then it is determined whether the LOS counter is greater than zero, as represented in block 112 . If the LOS counter is not greater than zero, the temporary engine disable is flagged as FALSE and the engine is commanded to enable or remain enabled, as shown in block 116 . However, if the LOS error counter is greater than zero, then the LOS counter is decremented or decremented, as represented by block 118. After the LOS counter has been decremented, it is determined whether the error counter has reached zero, as represented by block 120 . If the LOS counter is zero, then the method proceeds to mark the motor deactivation as FALSE, as represented by block 114, and command the motor to activate or remain activated, as represented by block 116. If the error counter remains greater than zero, then the method proceeds again to disable the engine as represented by blocks 108,110. Finally, the TRUE and FALSE flags are sent to the vehicle control system as represented by block 122 . Based on the information sent to the vehicle control system, the vehicle can act according to the description given in relation to 6 given is.

By requiring the fault counter to be equal to zero, as represented by block 120, the control system ensures that even if it is determined that there is no fault condition in the motor and/or motor-inverter, the motor is temporarily powered for a short time is disabled when the LOS error count is still above zero. This allows the diagnostics to be run multiple times, with the LOS error counter being reduced on each diagnostic run until the counter reaches zero. Several checks of the motor and/or motor-inverter are therefore performed while the motor is disabled before the motor is re-enabled if no fault condition is detected.

The diagnostics performed by the MGSE are designed to temporarily shut down the engine if a fault is detected. While the engine is temporarily disabled, the vehicle will run in a temporarily reduced power mode. However, if the fault condition is present for only a brief moment (e.g. less than 1 second), the LOS mode can be set and the motor will be quickly reactivated, reducing the disturbance experienced by the vehicle operator. It will be appreciated that all diagnostics can be performed in less than one second, for example twenty microseconds, whereby the time that the engine is momentarily shut down may be unnoticeable to the vehicle operator.

As in 5 As shown, the LOS mode 100 and the performance of the diagnostic process as shown in block 102 are performed for the generator and WC as well as the engine. Diagnostics are generally performed simultaneously for the motor, generator, associated inverter and VVC, so checking for fault conditions in each component is continuous. The MGSE can thus temporarily disable any or all of the engine, generator or VVC. It is envisaged that the diagnostics can also be carried out for other components, for example the other motor.

6 FIG. 200 is a flowchart of another embodiment of the LOS mode implemented by a controller or the vehicle control system. As described above, the MGSE sets a flag of either TRUE or FALSE to temporarily disable or enable the engine, as represented by blocks 108 and 114, respectively. The TRUE and/or FALSE flags are obtained from the MGSE by the vehicle control system, as represented by block 202 .

If the flag is FALSE then the vehicle control system commands the MGSE to return to the diagnostic test 102 as represented by block 204 .

However, if the flag is TRUE, then a determination is made as to whether the engine has been temporarily disabled for at least a threshold duration, as represented by block 206 . If the engine has been disabled for at least the threshold duration, then the engine can perma nent may be disabled for the respective key cycle, as represented by block 208. In one embodiment, the threshold duration may be approximately one second such that if the engine has been temporarily disabled for at least one second, it will be permanently disabled during the respective key cycle. Any suitable threshold duration is contemplated, however, and the threshold duration may vary depending on other factors. A key cycle may also be referred to as a drive cycle or power cycle and corresponds to the period from the time the vehicle is started, ie turning the ignition key, until the vehicle is turned off by turning the ignition key. During a new key cycle, the motor, or any other failed device such as the VVC or inverter, can be reactivated as referred to in FIG 7 is described.

The referring to 5 and 6 The algorithms described provide a diagnostic check of the engine, alternator, VVC, or any other powertrain component. Briefly, if the particular powertrain component is determined to be running under a fault condition, that component is temporarily disabled. Diagnostics are continuously run on this component while it is temporarily disabled. If the device recovers from the fault condition or the fault was transient, allowing the device to run under normal conditions within the time threshold, the device can be powered up again. However, if the device does not recover from the fault condition within the time threshold, the device will be permanently disabled during that key cycle and can only be re-enabled in a new key cycle (e.g., turning the vehicle off and on again).

7 3 shows a flowchart 300 of another embodiment of the LOS mode implemented by a controller or the vehicle control system. As represented by block 302, the vehicle is commanded to start and a new key cycle is commanded. Initially, the electric machines including the engine, generator and VVC are disabled. A series of pre-launch safety checks are performed before the vehicle is initialized.

For example, the vehicle control system verifies that current sensor zeroing is complete, as represented by block 304 . Current sensor zeroing must be complete in all electrical machines. The current sensors must have a zeroed reading when the amperage is zero in order to get accurate readings when the amperage surges during cranking. Next, a self-test of the VVC is performed, as represented by block 306 . The toilet self-test ensures that any errors in the VVC are detected and cleared. A determination is also made as to whether any torque errors are present, as represented by block 308 . In other words, the available power and/or torque of the electric machines must be assessed to determine if a required torque can be achieved by the electric machines.

The duty cycle commands provided to the electric machine are disabled or reset by the controller, as represented by block 310 . Resetting the duty cycle puts the electric machines into a safe mode, protecting the hardware. Only after the fault conditions have been removed can the duty cycle commands be turned back on, allowing safe control of the electric machine. This is referred to as a "soft restart" which does not require a new key cycle, as opposed to a "hard restart" which requires the vehicle to be turned off. Finally, as represented by block 312, faults in the hardware are determined before the vehicle can start.

Once the pre-start safety checks are successfully completed, the vehicle starts and the electric machines are allowed to start, as represented by block 314 . The electric machines are also fully switched on and the vehicle can be driven.

During operation of the vehicle, the referenced to 5 and 6 described diagnostic algorithms, as represented by block 316. The electric machines are continuously checked for errors, so each of them can be temporarily disabled according to the procedures previously described.

If a request to deactivate any of the electric machines is detected at block 316 , then the electric machine is deactivated as represented by block 318 . In order to turn the electric machine back on, the controls in the vehicle must go through a series of safety checks and safety processes before turning the electric machine back on in block 314 . The safety checks and processes allow the vehicle to continue to drive, the electric machines to continue to provide propulsion without a key cycle being present.

In one of the safety checks, as represented by block 320, the controller determines whether a temporary deactivation of the electric machine is still required, as previously related to block 110 in FIG 5 was described. If deactivation of the electric machines is not required, the controller may determine whether there is a requirement that the electric machines should be in an off or permanently deactivated mode, as represented by block 322 . If the electric machines are not disabled, a torque compliance check is performed as represented by block 324 . The torque compliance check is similar to the check performed with reference to block 308 .

Next, as represented by block 326, a power constraint and balance check is performed. With this check, the controller can determine whether a process is ongoing where electrical power to one of the electric machines is limited or that one of the electric machines does not have a power or torque limitation that is much higher than that of the other electric machine. The power limitation mode will be in 8th described in more detail. Finally, as represented by block 328, an overcurrent check is performed. Overcurrent testing determines whether any electrical machine is supplying or outputting a current level above a given threshold. If all safety checks are satisfactory, the pre-start/reactivation checks are complete and the system begins again at block 302 until the deactivated electric machine is reactivated at block 314.

8th FIG. 4 is a flowchart 400 of another embodiment of the LOS mode implemented by a controller or the vehicle control system. 8th describes a LOS mode in which a power limitation mode is implemented when a fault condition is detected in one of the electric machines. In previous hybrid-electric vehicles, failures or fault conditions in a hybrid-electric vehicle powertrain were difficult to recover from without reducing the vehicle's performance while driving or stopping the vehicle entirely, and then required a key cycle to resume partial operation. A key cycle was necessary to properly maintain power balance in the failed device. In a hybrid electric powertrain, if a failure is detected in one of the devices, eg, an electric machine, acting only on the failed device would result in a power imbalance, leading to unstable performance and further control-related errors.

To avoid power imbalances and unstable performance, flowchart 400 describes in 8th the process whereby the vehicle enters LOS mode if one of the electric machines fails while driving and continues the hybrid electric powertrain with the second electric machine without the need for a key cycle. The process described in flowchart 400 allows the control system to rapidly balance power if one of the electric machines fails and allows the other electric machine to continue to provide propulsion to the vehicle.

Initially, as represented by block 402, the control system detects a failure in a first hybrid electric powertrain device and disables the device in response to the fault condition. The failure can occur in one of the electrical machines or in the associated inverters. In response to the error condition and the disabled device, the control system initiates a power limitation mode, as represented by block 404 . Initially, the performance limitation mode is performed with high execution speed. For example, the high speed may be an execution speed of 100 microseconds.

While still running at a high execution speed, the control system temporarily disables the second device, as represented by block 406. The VVC is also temporarily placed in a shunt mode as represented by block 408 . The shunt mode of the VVC allows high voltage to be quickly dissipated from the electric machines to the low voltage input side of the VVC. An error may also be indicated to the driver in response to the failure, as represented by block 410.

After a threshold period, as represented by block 412, the control system may initiate a power throttling mode with a slower execution speed. For example, the threshold duration may be as little as 20 milliseconds, or any other threshold duration sufficient for the high voltage to dissipate so that the devices are not at risk of an overvoltage that could lead to further failures. The control system initiates the lower execution speed so that further diagnostics can be performed.

Once the lower speed power limitation mode is initiated, the control system reactivates the second device that has not failed. However, the second device is reactivated in a torque limit mode, as represented by block 414 . In the torque limit mode, torque for the functional device is limited to the functional device based on vehicle operation. The maximum torque “T _max ” in LOS mode is limited based on the following formula: T _max = (I _max × V _battery )/ω;

In other words, the maximum torque in LOS mode is limited based on the maximum allowable current of the high voltage bus in LOS mode times the voltage from the battery divided by the speed of the second device. In one embodiment, the maximum current allowed in LOS mode is a fixed value, for example 150 A. The battery voltage can be variable.

Once the functional device in a functional module is reactivated, the control system checks whether the first device is still failed or deactivated, as represented by block 416 . If the MGSE or HSV requests that the first device be disabled or still failed, a power cap counter is incremented, as represented by block 420 . However, if no fault is present and there are no deactivation requests from the controllers, the control system may exit power limit mode, as represented by block 424 . By exiting the power limitation mode, the control system also exits from the low execution speed.

The control system then resets the power cap timer to zero as represented by block 426 . Once the power cap timer is set to zero and LOS mode is ended, the control system may also reactivate the first and second devices, as represented by block 428 . Device reactivation includes exiting torque limit mode and returning to normal function.

On the other hand, if the first device is still in a failure state, the MGSE or HSV will request that the device be disabled or placed in a LOS mode and the control system will determine if the power cap timer is greater than a threshold, as represented by block 432.

If the power cap timer has exceeded a threshold, the low speed diagnostic mode is exited, as represented by block 434 . Then, as represented by block 436, the torque limit mode for the functional device is permanently maintained.

Maintaining torque limit mode permanently disables the device. In some embodiments, the device can only be permanently disabled until a new key cycle of the vehicle. The device may be permanently disabled for a variety of reasons, including those set out in 5 - 7 described procedure.

9 FIG. 5 is a flowchart 500 of another embodiment of the LOS mode implemented by a controller or the vehicle control system. A high voltage battery signal, also referred to as an HSBATT signal, is received from the controller, eg, the MGSE, as represented by block 502 . The high voltage battery signal is measured by the sensor along the input side of the VVC. Based on the high voltage battery signal provided by the sensor, the controller determines whether the high voltage battery signal is valid, as represented by block 504 . The high voltage battery signal is valid when the signal is within an acceptable range.

If the HSBATT signal is valid, the controller continues to use the high voltage battery signal, as represented by block 506, and the VVC can function normally, for example, the VVC provides a voltage boost output for the inverters and electric machines, as in 3 and 4 is described.

However, if the high voltage battery signal is outside of the acceptable range, the signal is determined to be invalid. If the high voltage battery signal is invalid, then the signal is set to an error state, as represented by block 508 . If the high voltage battery signal is set to the fault condition, then the MGSE communicates with the HSV to determine if an alternate signal is available to provide the high voltage battery signal and prevent a shutdown or short circuit of the electric machines and vehicle.

As previously described, the HSV is able to communicate via the vehicle network, eg CAN. For example, the HSV can communicate with the BSM on the vehicle network to receive an alternative battery voltage signal from the BSM gen. The alternate battery voltage signal from the BSM may be a sensed voltage measured in the BSM. Alternatively, the alternate battery voltage signal may be derived from other battery readings in the BSM or other vehicle system controllers that communicate with the vehicle network.

The MGSE determines whether the alternative voltage signal provided by the vehicle network is valid, as represented by block 510 . The alternate battery voltage signal is considered a valid signal if the battery voltage is within an acceptable range. If the alternate battery voltage signal is recognized as valid by the BSM, then the alternate battery voltage signal replaces the HSBATT, as represented by block 512 . Using the alternate battery voltage signal in place of the HSBATT allows the VVC to continue running normally, as represented by block 514 . During normal operation, the VVC can provide a voltage boost from the battery voltage on the input side to the inverter and electric machines on the output side. Thus, by introducing alternative signals during operation, the electric machines can continue to run normally, despite the lost high-voltage battery signal.

The vehicle may also indicate an error to the driver, as represented by block 516 . The fault may be displayed as a wrench shaped light to inform the driver of the fault condition. The high voltage battery signal fault condition can be triggered by a sensor failure. The display may indicate that the sensor needs to be replaced.

If the MGSE determines that the alternate signal is not valid, the control system ignores the alternate signal, as represented by block 518 . For example, the alternate signal may be invalid if it is outside of an acceptable range or threshold. If the alternate signal is invalid, this may indicate a secondary fault.

10 FIG. 6 is a flowchart 600 of another embodiment of the LOS mode implemented by a controller or the vehicle control system. A high voltage battery bus signal, also referred to as an HVDC signal, is received from the controller, eg, the MGSE, as represented by block 602 . The high voltage bus signal is measured by the sensor along the output side of the VVC. Based on the high voltage bus signal provided by the sensor, the controller determines whether the high voltage bus signal is valid, as represented by block 604 . The high voltage battery signal is valid when the signal is within an acceptable range.

If the HVDC signal is valid, the controller continues to use the high voltage bus signal, as represented by block 606, and the VVC can function normally, with the VVC providing a voltage boost output to the inverters and electric machines, as in 3 and 4 is described.

However, if the high voltage bus signal is outside the acceptable range, the signal is determined to be invalid. If the high voltage bus signal is determined to be invalid, then the signal is set to an error state, as represented by block 608 . If the signal is determined to be invalid, then the HVDC signal is set to fault and a LOS mode is implemented to keep the electric machines functioning and allow the vehicle operator to continue driving.

If the high voltage bus signal is set to the fault state, then the MGSE attempts to use the high voltage battery signal, HSBATT, from the input side of the VVC instead of the high voltage bus signal. The MGSE determines whether the high voltage bus signal is valid as represented by block 610 . It is envisaged that the controller can use any HSBATT signal, e.g. the high voltage bus signal measured by the sensor or the alternative battery voltage signal provided by CAN via the HSV to the MGSE, as described above in 9 is explained.

As previously discussed, the high voltage battery signal is determined to be a valid signal when the battery voltage is within a valid range. If the high voltage battery signal is determined to be valid, then the HSBATT is used in place of the high voltage bus signal, as represented by block 612 .

If a high voltage battery signal is used in place of the high voltage bus signal, the VVC may continue to run, but the VVC is placed in a LOS mode, as represented by block 614 . In LOS mode, the VVC is switched to a shunt mode. In shunt mode, the VVC is not allowed to provide a voltage boost, as represented by block 616 . The vehicle may also indicate an error to the driver, as represented by block 618 . Again, the error may appear as a wrench-shaped light, to inform the driver of the error condition. The fault condition in the high voltage bus signal can be triggered by a sensor failure. The display may indicate that the sensor needs to be replaced.

If the MGSE determines that the HSBATT signal is not valid, the control system ignores the alternate HSBATT signal, as represented by block 620. For example, the alternate signal may be invalid if it is outside of an acceptable range or threshold. If the alternate signal is invalid, this may indicate a secondary fault.

It should be understood that while reference has been made to deactivation and activation of the engine, similar algorithms are provided for the engine 16, generator 32, inverter 15 and WC 60. In other words, if a fault condition exists in one of the motor 16, generator 32, inverter 15, and WC 60, the methods described above can be applied to any of these components and to other powertrain components.

the 11 - 12 show a troubleshooting strategy for hardware errors. Hardware failures in one subsystem can affect other subsystems and trigger further errors. One of the more common occurrences that occur as a result of outages is an inverter 15 overvoltage fault. The overvoltage fault is caused by the inverter hardware. Upon triggering, the hardware may disable the motor inverter 15 and/or the generator inverter 15 and the VVC 60 resulting in a vehicle QOR. Other hardware conditions that are less severe than hardware overvoltage faults are IGBT faults. A failure of any IGBT 92 may affect only the affected device(s). However, IGBT failures can occur due to transient events and not actual physical damage to the failed IGBTs. The failure can occur in any IGBT 92 associated with the inverter 15 for the motor 16 or generator 32, or on one or both IGBT 92 on the WC 60. According to one embodiment, the vehicle control system 12 is configured to detect hardware failures, such as IGBT -Error to fix. 11 FIG. 7 is a voltage diagram 700 of an inverter showing a strategy for overvoltage curve recovery. As in 11 As shown, hardware diagnostics detect an inverter voltage at point 710 when the voltage exceeds an overvoltage fault threshold 714 .

If the voltage exceeds the overvoltage fault threshold 714, the control system may disable the engine 16, generator 32, and WC 60. The MGSE 70 can also be set to an error indicator to indicate the hardware problem.

From point 710 , if the inverter voltage exceeds the threshold 714 , the control system strategy waits for the voltage to drop below a safety threshold 720 . The control system can wait for a predetermined period of time or set an error counter, such as in 12 is shown in more detail. At point 724, where the inverter voltage falls below the safety threshold 720, the control system resets the hardware fault to remove the action that disabled the various devices, eg, motor 16, generator 32, and VVC 60. Once the error is cleared, the VVC 60 can be forced into a temporary extension LOS mode. As discussed previously, the shunt mode may allow the high voltages from the electric machines to be quickly shunted to the low voltage input sides of the VVC. The WC shunt mode may prevent the likelihood of subsequent motor 16, generator 32, and/or WC 60 transients that may result in secondary faults. Thus, by resolving a hardware inverter overvoltage fault as quickly as possible within the same drive cycle, the number of vehicle QORs due to secondary faults is reduced and allows for longer vehicle usability.

The control system strategy waits for the voltage to fall below a recovery threshold 730 . At point 734, when the inverter voltage falls below the recovery threshold 730, the control system reverts to the MGSE default settings. In the absence of other faults, the engine 16, generator 32, and VVC 60 recover from their respective LOS modes. If other errors are present, each individual device can remain in its appropriate mode.

12 12 is a flow chart showing an example of the motor 16, generator 32, or WC 60 fault recovery strategy based on a fault in one of the IGBTs 92. FIG. 12 FIG. 8 is a flowchart 800 of another embodiment of the LOS mode implemented by a controller or the vehicle control system. The control device, eg, a MGSE, receives an IGBT fault signal for a particular device, as represented by block 802 . The IGBT error signal can be used with any device device, e.g. the engine 16, the generator 32 or the toilet 60.

An IGBT fault is detected by the motor-inverter 15, generator-inverter 15, or VVC 60 hardware. The IGBT fault signal is then sent to the controller 12. Based on the IGBT error signal, the controller determines whether the IGBT error signal reading of the last loop corresponds to the current IGBT error signal reading, as represented by block 804 . If the current IGBT error signal reading corresponds to the last loop, the control system can initiate a slower execution speed so that further diagnostics can be performed to determine whether one of the IGBT 92 has still failed, as represented by block 806 . If the current IGBT error signal reading does not correspond to the last loop, the control system determines the state of the IGBT 92 as represented by block 810.

If the IGBT 92 continues to fail or has a fault, an IGBT fault counter is incremented, as represented by block 820 . The control system sets a LOS mode for the failed device to temporarily disable the device, as represented by block 822, and then checks whether the motor inverter 15 or generator inverter 15 or VVC 60 is still failed or disabled. as represented by block 416.

However, if there is no IGBT fault, the control system decrements the IGBT fault counter as represented by block 826 . When the IGBT fault counter is zero, LOS mode can be exited, as represented by block 830 . Once the IGBT error counter is set to zero and LOS mode is terminated, the control system can also reactivate other devices and return to normal function. The processes, methods, or algorithms disclosed herein may be deliverable to or implementable by a processing device, controller, or computer, including any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in various forms, including but not limited to information stored permanently on non-writable storage media such as ROM Devices that store and change information stored on writable storage media such as floppy disks, magnetic tape, CDs, RAM devices, and other magnetic or optical media. The processes, methods, or algorithms can also be implemented in an executable software object. Alternatively, the processes, methods, or algorithms may be implemented in whole or in part using suitable hardware components, such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), state machines, controllers, other hardware components or devices, or a combination of Hardware, software and firmware components.

Reference List

8th

402

Controller detects failure and disables 1st device

404

High speed power limitation LOS mode initiation

408

Temporary switching of VVC to shunt mode

406

Temporary deactivation of the 2nd device

410

display of the error

412

Low speed power limitation LOS mode initiation

414

Reactivation of VVC and 2nd device in torque limit mode (Heading to formula) "2nd Device" = 2nd device (index too small omega in denominator of formula)

416

Is the 1st device still failed or disabled?

420

Incrementing the power cap counter

432

Is the power cap time counter > threshold time?

434

Exit from low speed

436

Permanent maintenance of torque limit mode in the 2nd device

424

Exit from power limitation LOS mode and low speed

426

Resetting the power cap counter to zero

428

Reactivation of the 1st and 2nd devices

N

no

Claims (5)

A method of controlling a hybrid electric vehicle (10) comprising: disabling an electric machine (16) and a variable voltage converter (WC, 60) when the voltage of the electric machine (16) exceeds an overvoltage threshold (714); and once it is determined that the voltage of the electric machine (16) has decreased to at least a second threshold lower than the overvoltage threshold (714), reactivating the electric machine (16); and setting the VVC (60) to a normal mode of operation. procedure after claim 1 , further comprising reactivating the electric machine (16) during a drive cycle. procedure after claim 2 wherein disabling the VVC (60) places the electric machine (16) in a restricted mode of operation, the restricted mode of operation allowing the vehicle (10) to maintain vehicle propulsion during the drive cycle. procedure after claim 1 , further comprising: commanding the VVC (60) to run in a mode in which a voltage is passed from a high voltage electrical terminal to the battery (14) to, in response to the electric machine (16) exceeding the overvoltage threshold ( 14) exceeds the ability to quickly discharge high voltage. procedure after claim 1 wherein in response to the electric machine (16) exceeding the overvoltage threshold (14), the VVC (60) is set to a mode that prevents the provision of a boost voltage to the at least one electric machine (16).

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