Electric drive stall torque enhancement based on vehicle level input

Abstract

The present invention relates to electric drive stall torque enhancement based on vehicle level inputs. A method for increasing a default electric stall torque limit in a motor vehicle having an electrified powertrain including a traction power inverter module (TPIM) connected to an electric traction motor includes receiving, by a controller, a vehicle level input. The controller is programmed with a default electric stall torque limit. The method includes selecting, by the controller, an inverter control strategy as a selected inverter control strategy responsive to the vehicle level input, the strategy including temporarily increasing the default electric stall torque limit while applying a pulse width modulation (PWM) type at a corresponding PWM switching frequency. The method further includes controlling, by the controller, an output state of the TPIM and the electric traction motor using the selected inverter control strategy for a calibrated duration of time. A motor vehicle includes the controller, a wheel, the TPIM, and the traction motor.

Description

Technical Field

[0001] The present disclosure generally relates to methods and systems for optimizing low-speed electric drive performance of a battery electric vehicle, hybrid electric vehicle, or another mobile platform having an electrified powertrain. In particular, the present disclosure relates to real-time controller-based adjustments to a baseline / default electric stall torque limit and associated power inverter control strategy, with the goal of enhancing stall performance on a case-by-case basis for a given set of operating conditions. Background Art

[0002] As understood in the art, an electrified powertrain is "electrified" in the sense of operating from a high-voltage bus with one or more rotating electric machines. For example, a motor vehicle with an electrified powertrain uses one or more electric traction motors (or traction motors) to generate propulsion torque, with the electric traction motors acting as prime movers. That is, during different driving modes, output torque from the electric traction motors is directed to one or more driven axles and connected wheels. The relative torque contributions from the electric traction motors and possible other prime movers, such as an internal combustion engine, are selected in real time by an onboard controller based on the driver's requested torque and a number of other vehicle inputs.

[0003] When used as part of an electrified powertrain, electric traction motors are often configured as multi-phase / alternating current (AC) devices. Consequently, a power inverter is positioned between the traction motor's wound stator and an on-board direct current (DC) voltage source, with the latter typically implemented as a high-voltage propulsion battery pack, such as a multi-cell lithium-ion battery pack. Pulse-width modulation (PWM)-based switch state control of individual semiconductor switches arranged within the power inverter's switch die is used to convert the DC input voltage from the battery pack into a multi-phase / AC output voltage. The AC output voltage from the power inverter is directed to the stator and sequentially energizes the stator's field windings to ultimately rotate the rotor. To protect the electrified powertrain's sensitive power electronics hardware, the operation of the electric traction motor and its associated power inverter is carefully controlled according to a set of calibrated thermal, torque, speed, and other performance capability limits. Summary of the Invention

[0004] The present disclosure relates to real-time operational control of an electrified powertrain on a motor vehicle or other mobile platform having at least one electric traction motor connected to and driven by a corresponding power inverter, hereinafter referred to as a traction power inverter module (TPIM). The method described herein increases the TPIM's default electric stall torque limit as appropriate and selects a corresponding inverter control strategy based on a set of vehicle-level inputs. In other words, these vehicle-level inputs are used by a controller to determine current vehicle conditions and / or driver intent indicative of impending operation in or near a stall condition.

[0005] As used herein and in the art, electric stall torque refers to the amount of motor output torque available from an electric traction motor when operating at zero output frequency. For example, for a synchronous motor, electric stall torque is the torque load on the electric motor required to stop the rotor of the electric traction motor from rotating. Therefore, the various controller-based control actions disclosed herein apply to any speed between the electric traction motor's zero output speed and a calibrated stall torque threshold speed, which is implemented for a specific output frequency.

[0006] Based on vehicle-level inputs such as, but not necessarily limited to, ascending or descending grade, braking level, acceleration request, selected drive mode, and other possible inputs, the controller intelligently selects the pulse-width modulation (PWM) type and inverter switching frequency. This selection is made during low-speed, high-current operation of the TPIM and traction motor as a tradeoff between duration under temporarily increased electric stall torque limit, on the one hand, and noise, vibration, and harshness (NVH) performance, on the other.

[0007] This solution is intended to enable temporary operation at increased stall torque limits relative to default levels, without modifying or damaging sensitive underlying powertrain hardware, primarily the TPIM and its delicate inverter switches, and without adversely impacting the aforementioned NVH performance. Increasing stall torque capability herein occurs by lowering the motor output torque limit toward a calibrated or predetermined "stall torque notch," i.e., a default limit that can be operated and maintained indefinitely in steady state without violating inverter thermal limits. This occurs over time during the aforementioned low-speed, high-current operation.

[0008] According to one exemplary embodiment, a method for increasing an electric stall torque limit in a motor vehicle having an electrified powertrain, the electrified powertrain including a TPIM and an electric traction motor, wherein the electric traction motor is electrically connected to the TPIM. The method includes receiving, via a controller, a set of vehicle-level inputs, wherein the controller is programmed with a default electric stall torque limit. Then, selecting, via the controller, an inverter control strategy as a selected inverter control strategy in response to the vehicle-level inputs. The selected inverter control strategy, including a selected PWM type and a corresponding PWM switching frequency, may also include temporarily increasing the default electric stall torque limit. The method in this embodiment also includes controlling, via the controller, output states of the TPIM and the electric traction motor for a calibrated duration using the inverter control strategy.

[0009] In certain embodiments, receiving the set of vehicle level inputs may include receiving a braking request and an acceleration request from a brake pedal sensor and an accelerator pedal sensor, respectively, and / or receiving a grade signal from a grade sensor, wherein the grade signal indicates an incline of the motor vehicle ascending or descending a slope representing a grade. The vehicle level inputs may include a mode selection signal from a mode selection device, wherein such signal indicates a selected operating mode of the motor vehicle.

[0010] In various illustrative and non-limiting embodiments, for example, when the set of vehicle level inputs indicates flat terrain, a threshold traction event, a hill hold maneuver, or a wide-open throttle maneuver, the selected PWM type may include space vector PWM (SVPWM) at a PWM switching frequency of 10 kHz.

[0011] The PWM type may include a discontinuous PWM (DPWM) type, and the PWM switching frequency may be less than 10 kHz, such as 2 kHz, when the set of vehicle level inputs indicates a terrain mode or a rock crawling maneuver.

[0012] Selecting the inverter control strategy may include modifying a preselected inverter control strategy in response to the set of vehicle level inputs.

[0013] A motor vehicle is also disclosed herein. In a representative embodiment, the motor vehicle includes a set of wheels, an electrified powertrain having a TPIM and an electric traction motor, and a controller. The electric traction motor is electrically connected to the TPIM and mechanically coupled to the wheels. The controller is programmed with default electric drive torque limits for the TPIM and the electric traction motor and is configured to perform the above-described method.

[0014] Also disclosed herein is a controller having a processor and a memory on which is recorded a default electric stall torque limit and instructions. Execution of the instructions by the processor causes the controller to receive a set of vehicle level inputs and select an inverter control strategy as a selected inverter control strategy in response to the set of vehicle level inputs. The selected inverter control strategy includes temporarily increasing the default electric stall torque limit and applying a type of pulse width modulation (PWM) at a corresponding PWM switching frequency. Execution of the instructions also causes the controller / processor to control an output state of a TPIM and an electric traction motor using the selected inverter control strategy for a duration of a calibration.

[0015] The present invention also includes the following technical solutions.

[0016] Scheme 1. A method for increasing an electric stall torque limit in a motor vehicle having an electrified powertrain, the electrified powertrain including a traction power inverter module (TPIM) connected to an electric traction motor, the method comprising:

[0017] receiving, by a controller, a set of vehicle level inputs, wherein the controller is programmed with a default electric stall torque limit;

[0018] selecting, by the controller, an inverter control strategy as a selected inverter control strategy in response to the set of vehicle level inputs, the selected inverter control strategy including temporarily increasing the default electric stall torque limit and selecting and applying a type of pulse width modulation (PWM) at a corresponding PWM switching frequency; and

[0019] controlling, by the controller, an output state of the TPIM and the electric traction motor using the selected inverter control strategy for a duration of a calibration.

[0020] Scheme 2. The method of Scheme 1, wherein receiving the set of vehicle level inputs includes respectively receiving a brake request and an acceleration request from a brake pedal sensor and an accelerator pedal sensor.

[0021] Scheme 3. The method of Scheme 1, wherein receiving the set of vehicle level inputs includes receiving a grade signal from a grade sensor, the grade signal indicating an angle of inclination of the motor vehicle.

[0022] Scheme 4. The method of Scheme 1, wherein receiving the set of vehicle level inputs includes receiving a mode selection signal from a mode selection device, the mode selection signal indicating a selected mode of operation of the motor vehicle.

[0023] Option 5. The method of option 1, wherein when the set of vehicle level inputs indicates a threshold road load, the PWM type comprises space vector PWM (SVPWM), and the PWM switching frequency is 10 kHz.

[0024] Option 6. The method of option 1, wherein when the set of vehicle level inputs indicates a terrain mode or a rock crawling maneuver, the PWM type is zero vector modulation (ZFM), and the PWM switching frequency is less than 10 kHz.

[0025] Option 7. The method of Option 1, wherein a preselected inverter control strategy is received by the controller receiving the set of vehicle-level inputs, and wherein selecting the inverter control strategy includes modifying the preselected inverter control strategy in response to the set of vehicle-level inputs.

[0026] Solution 8. A motor vehicle comprising:

[0027] a set of wheels;

[0028] an electrified powertrain having a traction power inverter module (TPIM) and an electric traction motor, wherein the electric traction motor is electrically connected to the TPIM and mechanically coupled to the set of wheels; and

[0029] a controller programmed with a default electric stall torque limit for the TPIM and the electric traction motor, wherein the controller is configured to:

[0030] Receive a set of vehicle level inputs;

[0031] selecting an inverter control strategy as a selected inverter control strategy responsive to the set of vehicle level inputs, the selected inverter control strategy comprising temporarily increasing the default electric stall torque limit, a pulse width modulation (PWM) type, and a corresponding PWM switching frequency; and

[0032] Output states of the TPIM and the electric traction motor are controlled for a calibrated duration using the selected inverter control strategy.

[0033] Option 9. The motor vehicle of Option 8 further comprising a brake pedal having a brake pedal sensor, wherein the set of vehicle-level inputs includes a brake request signal from the brake pedal sensor.

[0034] Option 10. The motor vehicle of Option 8 further comprising an accelerator pedal having an accelerator pedal sensor, wherein the set of vehicle-level inputs further comprises an acceleration request signal from the accelerator pedal sensor.

[0035] Option 11. The motor vehicle of Option 8, further comprising a grade sensor, wherein the set of vehicle level inputs further comprises a grade signal from the grade sensor indicating an angle of inclination of the motor vehicle.

[0036] Embodiment 12. The motor vehicle of embodiment 8, further comprising a mode selection device, wherein the set of vehicle level inputs includes a mode selection signal from the mode selection device indicating a selected operating mode of the motor vehicle.

[0037] Embodiment 13. The motor vehicle of embodiment 8, wherein when the set of vehicle level inputs indicates flat terrain, a threshold traction event, a hill hold maneuver, or a wide-open throttle maneuver, the PWM type is space vector PWM (SVPWM) and the PWM switching frequency is 10 kHz.

[0038] Embodiment 14. The motor vehicle of embodiment 8, wherein the PWM type is zero vector modulation (ZVM) when the set of vehicle level inputs indicates terrain mode, rock crawling maneuver, descending or ascending grade, a threshold high braking level, or sport mode.

[0039] Option 15. A motor vehicle according to Option 14, wherein the PWM switching frequency is approximately 2 kHz when the set of vehicle level inputs indicates the terrain mode or the rock crawling maneuver, and the PWM switching frequency is approximately 10 kHz when the set of vehicle level inputs indicates an ascending or descending grade, the threshold high braking level, or the sport mode.

[0040] Embodiment 16. The motor vehicle of embodiment 8, wherein the controller includes a stall torque timer, and wherein the controller is configured to limit the temporary increase in the default electric stall torque limit based on the stall torque timer.

[0041] Embodiment 17. A controller having a processor and a memory, wherein a default electric stall torque limit and instructions are recorded on the memory, wherein the instructions, when executed by the processor, are configured to cause the controller to:

[0042] Receive a set of vehicle level inputs;

[0043] selecting an inverter control strategy as a selected inverter control strategy responsive to the set of vehicle level inputs, wherein the selected inverter control strategy includes temporarily increasing the default electric stall torque limit and temporarily applying a pulse width modulation (PWM) type at a corresponding PWM switching frequency; and

[0044] Output states of the TPIM and the electric traction motor are controlled for a calibrated duration using the selected inverter control strategy.

[0045] Option 18. A controller according to Option 17, wherein the set of vehicle horizontal inputs includes: a braking request and an acceleration request from a brake pedal sensor and an accelerator pedal sensor, respectively; a grade signal from a grade sensor, the grade signal indicating the tilt angle of the motor vehicle; and a mode selection signal from a mode selection device, the mode selection signal indicating the selected operating mode of the motor vehicle.

[0046] Embodiment 19. The controller of embodiment 17, wherein execution of the instructions by the processor causes the controller to select the PWM type of the inverter control strategy from the group consisting of space vector PWM (SVPWM) and zero vector modulation (ZVM).

[0047] Embodiment 20. The controller of embodiment 17, wherein the set of vehicle-level inputs includes a preselected inverter control strategy, and wherein execution of the instructions causes the processor to modify the preselected inverter control strategy in response to the set of vehicle-level inputs.

[0048] The above features and advantages of the present disclosure and other features and attendant advantages will be apparent from the following detailed description of illustrative examples and modes for implementing the present disclosure when taken in conjunction with the accompanying drawings and the appended claims. Moreover, the present disclosure expressly includes any combination and sub-combination of the elements and features presented above and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a schematic diagram of a representative motor vehicle having an electrified powertrain and a controller programmed to select and execute an appropriate inverter control strategy according to the present disclosure.

[0050] Figures 2A-2C is a representative frequency diagram of different inverter control strategies within the scope of the present disclosure, wherein AC current frequency in Hertz (Hz) is plotted on the horizontal axis and torque in Newton-meters (Nm) is plotted on the vertical axis.

[0051] Figure 3 is a schematic diagram of a representative timer trace used as part of the present method, wherein time in seconds (s) is plotted on the horizontal axis and the percentage (%) of maximum stall torque increase is plotted on the vertical axis.

[0052] Figure 4 yes Figures 2A-2CAnother representative frequency plot of three different inverter control strategies of the'100 patent, wherein the horizontal axis depicts AC current frequency in Hertz (Hz) and the vertical axis depicts torque in Newton-meters (Nm).

[0053] Figure 5 and Figure 6 is a flowchart depicting an embodiment of the present method. DETAILED DESCRIPTION

[0054] The present disclosure allows for embodiments in many different forms. Representative examples of the present disclosure are described in the drawings and detailed description below, which sets forth, among other things, non-limiting examples of the disclosed principles. As such, the foregoing description and the following detailed description are not exhaustive of the many conceivable forms in which the claimed disclosure can be

[0055] For the purposes of the presently described subject matter, unless specifically stated otherwise, use of the singular includes the plural and vice versa, the terms "and" and "or" are both conjunctive and disjunctive, both "any" and "all" are intended to mean "any and all", and the terms "comprising", "containing", "including", "having" and the like are meant to be inclusive, not exhaustive. Furthermore, terms like "about", "almost", "essentially", "approximately", and the like can be used herein in the sense of "at, near, or almost at" or "within 0-5% of" or "within acceptable manufacturing tolerances" or logical combinations thereof.

[0056] Referring to the drawings, wherein like reference numbers indicate identical features throughout the several views, Figure 1 is schematically depicted with electrified powertrain 11 having controller (C) 50 programmed with a default electric motoring torque limit 200. Controller 50 is configured to selectively increase this default motoring torque limit 200 in response to a set of vehicle level inputs (arrows CC I ). Within the scope of the present disclosure, controller 50 automatically receives and evaluates these vehicle level inputs (arrows CC I ) to determine current vehicle conditions and driver intent, which together or individually can be indicative of imminent transient or extended operation in or near a motoring condition.

[0057] Controller 50 is configured to perform method 100 by executing computer readable instructions that implement method 100, wherein reference is made below to Figure 5 and Figure 61 and 10. The method 100 is used to enable the controller 50 to intelligently select a specific pulse width modulation (PWM) type and PWM switching frequency in response to this determination. As described above, this selection is made as a compromise between the expected duration of operation, wherein the controller 50 temporarily forces an increase in the default electric stall torque limit 200 in a manner that optimizes the tradeoff with the resulting noise, vibration, and harshness (NVH) performance.

[0058] For simplicity of illustration, selected components of the electrified powertrain 11 are shown and described in detail below, while other components are omitted. The electrified powertrain 11 may be used in a motor vehicle 10, such as a Figure 1 or used with another mobile platform such as a watercraft, aircraft, or rail vehicle. Figure 1 In the depicted representative embodiment, motor vehicle 10 is configured as a typical road vehicle having wheels 15 in rolling contact with a road surface. The actual number of wheels 15 may vary depending on the application and configuration of motor vehicle 10, including, for example, as few as one wheel 15 in the context of a motorcycle, scooter, or electric bicycle, and more than the number shown in other configurations.

[0059] The electrified powertrain 11 includes at least one electric traction motor (M E ) 14, which in the illustrated embodiment is coupled to one or more of the wheels 15 via an output member 17 and one or more drive axles 19. The electric traction motor 14 is coupled to and powered by a traction power inverter module (TPIM) 20, wherein operation of the electric traction motor 14 and the TPIM 20 is closely governed by a controller 50 according to a default electric stall torque limit 200, which is referred to below. Figure 2A-4 The application of the electric stall torque limit 200 and its incremental variations will be described in detail.

[0060] Continue to refer Figure 1 The representative electric traction motor 14 is connected to and powered by a direct current (DC) voltage source, which in this case is a rechargeable high voltage battery pack (B HV ) 16. This occurs through the coordinated operation of the controller 50 and the TPIM 20, wherein the TPIM 20 is electrically connected to the respective phase windings (VAC) of the electric traction motor 14, for example, using an AC cable. Through the switching control of the TPIM 20 by the controller 50, or more precisely, through the operation of a gate driver (not shown) communicating therewith, the TPIM 20 converts the DC voltage from the battery pack 16 into a variable frequency / variable amplitude multiphase / AC voltage to power the electric traction motor 14 and thereby generate the desired torque (arrow T O ).exist Figure 1In a non-limiting embodiment, rotation of the cylindrical rotor 14R of the electric traction motor 14 provides power to the wheels 15. Hybrid embodiments are contemplated within the scope of the present disclosure in which an internal combustion engine (not shown) or another torque source or prime mover operates alone or in combination with the electric traction motor 14 to generate propulsion torque in a mode-specific manner.

[0061] The electric traction motor 14 in the illustrated embodiment is a multi-phase / AC rotary electric machine having a cylindrical rotor 14R and a cylindrical stator 14S. In a typical radial flux configuration, the rotor 14R may be coaxially arranged relative to the stator 14S, such that the stator 14S surrounds the rotor 14R, although axial flux type electric machines may also be used within the scope of the present disclosure. The rotor 14R is coupled to a mechanical load, such as one or more of the wheels 15, via an output member 17. The output member 17, which may be implemented as a rotatable gear set, shaft, or other mechanical mechanism, may be connected to the wheels 15 via a drive axle 19 and / or an intervening gearbox / transmission (not shown), where the output member 17 ultimately converts the output torque (arrow T) from the electric traction motor 14 to a desired load. O ) is transmitted to wheels 15 to propel the motor vehicle 10.

[0062] Still refer to Figure 1 Other components of the electrified powertrain 11 may also include a DC-DC voltage converter 18 and a low voltage / auxiliary battery (B AUX ) 160. The high voltage propulsion battery pack 16 is connected to the TPIM 20 via a high voltage bus (VDC), where a typical voltage level of such a high voltage bus is 300V or higher, or other voltage levels exceeding the auxiliary / 12-15V level of the auxiliary battery 160. However, because the vehicle 10 may also include a large number of low voltage systems, the low voltage bus (V AUX ) can be powered by a DC-DC converter 18, which in turn can be used to maintain a low voltage charge level of the auxiliary battery 160.

[0063] In addition to Figure 5 and Figure 6 Outside of those functions directly related to the present method 100, Figure 1 The controller 50 may be configured to perform other diagnostic and / or control functions. For example, for the purposes of this disclosure, the controller 50 may be a hybrid control unit, a transmission control unit, or another suitable stand-alone or networked vehicle controller. As such, the controller 50 may be implemented as one or more electronic control units or computing nodes that respond to vehicle level input signals (arrow CC) during the execution of the method 100 and when performing other possible control actions. I ) and other possible control signals.

[0064] Specifically for the purpose of executing method 100, the controller 50 is equipped with an application-specific amount of volatile and non-volatile memory (M) and one or more processors (P), such as microprocessors or central processing units, and other related hardware and software, such as digital clocks or timers, input / output circuits, buffer circuits, application-specific integrated circuits (ASICs), systems on a chip (SoCs), electronic circuits, and other necessary hardware required to provide the programmed functionality. In the context of the present disclosure, the controller 50 executes instructions through the processors (P) to cause the controller 50 to perform method 100. In doing so, the controller 50 ultimately transmits electronic control signals (arrows CC) to the controller 50. O ) is transmitted to the gate control pin (not shown) of the TPIM 20 for controlling the electric traction motor 14 connected thereto. As is understood in the art, the electronic control signal (arrow CC O ) includes commanding a PWM switching frequency and PWM type to the TPIM 20, or more specifically, to a gate driver (not shown) connected to the aforementioned gate pins of the switches that constitute the TPIM 20. Thus, execution of method 100 ultimately includes controlling the switching output state of the TPIM 20 and the dynamic output state of the electric traction motor 14 for a calibrated duration according to the selected inverter control strategy.

[0065] To optimize the electric drive performance of the motor vehicle 10 during certain operating maneuvers, Figure 1 The controller 50 and TPIM 20 utilize intelligent control strategies and hardware calibration to selectively increase electric stall torque relative to a level of the default electric stall torque limit 200. To this end, the controller 50 is programmed in software and equipped in hardware to execute instructions implementing the method 100 when increased stall torque capability is desired.

[0066] In a broad sense, the memory (M) of the controller 50 can be programmed with a variety of different inverter control strategies, which are respectively referred to as Figure 2A 、 2B and Strategies 1, 2, and 3 of 2C, and with possible n additional inverter control strategies, for example, n = 4 or more. The controller 50 then processes various vehicle level inputs (arrows CC I ), and in doing so, selects an inverter control strategy that is appropriate to the mode. Each inverter control strategy corresponds to the implementation of a specific tuning variant of the electric stall torque limit 200.

[0067] To this end, the vehicle level inputs (arrow CC) are jointly evaluated as part of the present method 100. I ) may include various measured, estimated, or calculated values ​​indicative of vehicle conditions and driver intent. By way of illustration and not limitation, exemplary vehicle level inputs (arrow CC I) including the slope signal (arrow G X ), which indicates the slope of the surface on which the motor vehicle 10 moves or stays, that is, the tilt angle of the motor vehicle 10. For example, a slope sensor S connected to the motor vehicle 10 g Can be used to measure slope / inclination angle and report the measured slope as a slope signal (arrow G X ).

[0068] Similarly, a brake request signal (arrow B) indicating the amount of brake pressure applied to the brake pedal 13B by the driver of the motor vehicle 10 or the resulting stroke thereof. X ) can be connected to the brake pedal sensor S 13B To measure. Through the accelerator pedal sensor S 13A The measured acceleration request signal (arrow A) indicates the amount of pressure and / or travel applied to the accelerator pedal 13A by the driver. X ) can also be used as vehicle level input (arrow CC I ). Other possible vehicle level inputs (arrows CC I ), such as a driver-selected or autonomously selected vehicle mode, e.g., tour, sport, rock crawl, hill hold, terrain, etc., or other input indicative of a requested mode of the motor vehicle 10, may be selected via a mode select signal (arrow M X ) is transmitted to the controller 50, the mode selection signal may be transmitted through the mode selection device S m Likewise, the vehicle level input (arrow CC I ) may include brake pedal sensor S 13B Braking torques other than those measured, such as propulsion system braking torques or brake pressure requests for the motor vehicle 10 as a whole or at individual wheels 15, may be determined autonomously in some embodiments and, therefore, vehicle level inputs (arrow CC I ) may vary depending on the intended application.

[0069] Now refer to Figures 2A-2C , three possible inverter control strategies, designated Strategy 1, Strategy 2, and Strategy 3, are shown with corresponding electric stall torque limits 200A, 200B, and 200C, respectively. The torque limit in Newton meters (Nm) is plotted on the vertical axis, while the AC current frequency of the electric traction motor 14 (i.e., the motor speed of the synchronous machine) in Hertz (Hz) is plotted on the horizontal axis. The inverter control strategy is determined by the controller 50 in response to the vehicle level input ( Figure 1 Arrow CC I ) to select different values ​​or combinations of values. For example, Figure 2AIn strategy 1, the vehicle enters horizontally (arrow CC I ) may indicate high brake pressure, a specific ascending or descending gradient, selection of "Sport Mode", etc., and may therefore indicate a threshold low road load.

[0070] Relative to Figure 1 The default electric stall torque limit is 200, which can be determined by Figure 2B Approximating the electric stall torque limit 200B, strategy 1 and operation in a low road load mode may result in the implementation of a relatively high stall torque limit (trace 53), wherein the stall torque limit gradually increases from a minimum value at zero frequency, i.e., zero speed of the electric traction motor 14, to a maximum level at the calibrated stall torque AC current frequency threshold f1, where arrow A indicates the possible difference in the stall torque limit (trace 53) relative to the calibrated maximum or 100% value (trace 52). In addition to adjusting the stall torque limit 200A as shown, the controller 50 also selects an appropriate PWM technique, which in this exemplary example may be a discontinuous PWM (DPWM) type, such as, but not limited to, zero vector modulation (ZVM) at a typical PWM switching frequency of 10 kHz. As understood in the art, ZVM, for example, has fewer switching events than SVPWM, which provides more thermal margin and, therefore, allows for relatively higher steady-state torque in a stall situation.

[0071] exist Figure 2B In the exemplary inverter control strategy 200B, the vehicle level input (arrow CC I ) may indicate operation in another vehicle mode or under different driving conditions, such as a threshold traction event, flat terrain, a wide-open throttle maneuver using both the brake and accelerator pedals simultaneously, or launch control to aggressively launch the vehicle, or a "hill hold" maneuver where the motor vehicle 10 remains stationary on an inclined surface, all of which indicate a higher road load. Figure 2A The electric stall torque level in (trace 52) is determined according to Figure 2B Operation of inverter control strategy 2 may result in a different stall torque limit being implemented at lower speeds of the electric traction motor 14 (trace 54), which stall torque limit also increases from a minimum value at zero speed / zero frequency to a maximum level of trace 52 at the calibrated stall torque AC current frequency threshold f1. Figure 2A Same, in Figure 2B The controller 50 in the scenario also selects an appropriate PWM type or technique, which Figure 2B This includes the use of Figure 2Athe same 10 kHz PWM switching frequency used in the examples above, but with SVPWM instead of ZVM as the selected PWM type for better NVH performance. As noted above, other techniques and / or frequencies can be used in other embodiments depending on the NVH tradeoffs.

[0072] Figure 2C illustrates yet another scenario, nominally inverter control strategy 3, in which the maximum stall torque (trajectory 52), i.e., 100% stall torque, is executed at low speeds of the electric traction motor 14. Relative to Figure 2A and Figure 2B both of which have a time-limited duration of the stall torque band above which operation, Figure 2C there is no stall torque band, i.e., strategy 3 can operate at 100% stall torque indefinitely. As understood in the art, certain motor vehicles 10, particularly those rated or configured for off-road use, are equipped with a selectable "rock crawl" mode or "terrain" mode to enable maximum torque at very low speeds. In accordance with the disclosed strategies, the controller 50 can select a different PWM strategy for operation of the TPIM 20 in such conditions, e.g., ZVM at a lower switching frequency relative to strategies 1 and 2, i.e., less than 10 kHz, in which a representative PWM switching frequency is approximately 2 kHz in possible embodiments. While Figure 2A , 2B and the particular vehicle level inputs (arrow CC I ) and selected PWM type and switching frequency are non-limiting and illustrative of the present teachings, the referenced figures collectively show Figure 1 the ability of the controller 50 to intelligently select an appropriate mode of inverter control strategy in close notification by the dynamically changing vehicle level inputs (arrow CC I ).

[0073] with respect to the applied electric stall torque limit 200A, 200B and 200C and the selection of different PWM types and PWM switching frequencies, Figure 2A the exemplary strategy of -C can produce significantly different NVH effects. For example, relative to strategy 2, the NVH performance and its slower torque reduction rate under strategy 1 of Figure 2A is expected to be reduced. For example, relative to Figure 2A , the inverter control strategy 2 of Figure 2B with its faster torque reduction rate should have the best NVH performance. In relative terms, the NVH performance is best in Figure 2CThe scenario of , ie operating under inverter strategy 3 , is in its worst case, where the 100% torque limit of trajectory 52 is always applied, ie from zero speed up to the speed associated with the calibrated stall torque AC current frequency threshold f1 .

[0074] Brief reference Figure 3 and Figure 4 , Figure 1 The controller 50 may use an extended stall torque timer, Figure 3 A representative timer trace 60 thereof is depicted in FIG. 5 , wherein time in seconds (s) is on the horizontal axis and electric stall torque reduction (motor torque increase) is plotted on the vertical axis. That is, the controller 50 may utilize increased stall torque capability over time by moving toward the default / baseline stall torque limit 200 (e.g., Figure 2B The stall torque limit 200B) reduces the electric stall torque limit. That is, when operating below the stall torque AC current frequency, the controller 50 can limit the time when the expansion capability is obtained.

[0075] For example, at a given operating point, the controller 50 may initiate a digital timer as part of the controller's 50 programming logic to limit the amount of time the controller 50 spends at the 100% extended stall torque range below the stall torque AC current frequency f1, thereby protecting the TPIM 20 and other sensitive components from overheating. Figure 3 The exemplary timer trace 60 will allow the electric stall torque to be temporarily maintained at a maximum value for the particular mode, for example, for 4 seconds as shown, and then ramped down to a calibrated minimum value (trace 52) for a predetermined duration, for example, from 4 seconds to 8 seconds in the illustrated embodiment. After the indicated time has elapsed, in this case 8 seconds, the controller 50 can control the TPIM 20 using its existing steady-state torque limit, which corresponds to the minimum stall torque capability, i.e., 0% extended capability.

[0076] therefore, Figure 4 The diagram illustrates a possible control scenario where the controller 50 may enable 100% extended capability from 0-4 seconds, then drop to 50% extended capability between 4 and 6 seconds, and thereafter drop to a steady-state stall torque range from 6-8 seconds. Figure 4 An extended stall torque capability is shown, controlled via the controller 50 based on a timer, to protect the TPIM 20 and other sensitive hardware from heating to thermal limits. Such a timer can be calibrated differently for different inverter control modes, with those modes with the best relative NVH performance and highest thermal stresses being allowed to continue for shorter durations relative to steady-state operation. In this regard, the indicated durations of 4 seconds, 6 seconds, and 8 seconds are merely illustrative of the present teachings and not limiting thereof.

[0077] Referring Figure 5 , the method 100 is configured or programmed to increase Figure 1 a baseline electric motoring torque limit 200 in a motor vehicle 10 as shown in FIG. 1, where the motor vehicle 10 represents a mobile platform having an electrified powertrain 11 including a TPIM 20, where the TPIM 20 is electrically connected to an electric traction motor 14. In general terms, the method 100 includes receiving, via a controller 50, the set of vehicle level inputs (arrow CC I ), where the controller 50 is programmed to have a default electric motoring torque limit 200. The method 100 in this embodiment includes selecting, by the controller 50, an inverter control strategy as a selected inverter control strategy, where the controller 50 does so in response to the set of vehicle level inputs (arrow CC I ).

[0078] The selected inverter control strategy includes temporarily increasing the default electric motoring torque limit 200, and selecting and applying a PWM type at a corresponding PWM switching frequency. Thereafter, the method 100 includes controlling, by the controller 50, an output state of the TPIM 20 and the electric traction motor 14 using the selected inverter control strategy for a calibrated duration of time. As understood in the art, controlling the output state can include controlling ON / OFF conduction states of resident switches of the TPIM 20 to thereby adjust output voltage and current of the TPIM 20, which in turn changes or maintains torque or speed of the electric traction motor 14.

[0079] An exemplary embodiment of the method 100 begins at block B102, where a current motor control calibration is received or determined by the controller 50. Based on an inverter mode request, which can be autonomously requested or selected by the drive, such motor control calibration includes a PWM type, a switching frequency, a motoring torque profile, a timer limit, an enable / disable calibration, etc. The controller 50 uses the motor control calibration to determine whether enhanced motoring torque capability should be temporarily enabled, i.e., whether the motor output torque limit should be temporarily increased relative to those limits of the default electric motoring torque limit 200 in low speed, high current conditions. When the controller 50 determines that enhanced motoring torque capability should be performed, the method 100 proceeds to block B104, and in another case proceeds to block B103.

[0080] At block B103, the controller 50 can set the above-mentioned extended motoring torque capability timer to 0, and the extended torque capability to 0% before proceeding to block B114.

[0081] Block B104 includes using the motor control calibration from block B102 to determine if the lower motor input frequency (below the stall torque AC current frequency threshold f1) and higher current conditions have been met. That is, Figure 1 The controller 50 determines, based on the motor control calibration, whether a reduction in switching frequency and a high current through the switches of the TPIM 20 may be necessary at low speeds of the electric traction motor 14 to achieve optimal drive and NVH performance. If this is the case, the method 100 proceeds to block B105, and in the other case proceeds to block B106.

[0082] Block B105 includes incrementing the enhanced stall torque capability timer before proceeding to block B107 .

[0083] Block B106 , reached upon determining at block B104 that low AC current frequency and / or high current conditions are not met, includes decrementing the enhanced stall torque capability timer. The method 100 then proceeds to block B108 .

[0084] At block B107 , the controller 50 compares the timer value to a calibrated maximum value and then proceeds to block B109 when the timer value exceeds the calibrated maximum value. In either case, the method 100 proceeds to block B112 .

[0085] At block B108, the controller 50 determines whether the timer value is now less than zero when the timer is decremented at block B106. If so, the method 100 proceeds to block B110. In another case, when the timer value is equal to or exceeds zero, the method 100 proceeds to block B112 instead.

[0086] Block B109 includes setting the current timer value to the maximum timer value before proceeding to block B112 .

[0087] Block B110 includes setting the timer value to zero before proceeding to block B112 .

[0088] At block B112, the controller 50 next accesses Figure 1 The controller 50 then uses a lookup table in the memory (M) to select the appropriate timer value for use with the enhanced stall torque capability. As described above, the lookup table determines the percentage of extended torque capability based on time. In other words, the timer value is input, and the corresponding enhanced stall torque capability is selected. The controller 50 then proceeds to block B114.

[0089] At block B114, the controller 50 next determines whether the baseline stall torque limit 200 and the resulting stall torque level are currently enabled. Figure 2BSuch a stall torque level corresponds to a torque limit that can be operated in steady state without excessively heating the TPIM 20. If enabled, the method 100 proceeds to block B116. Otherwise, the method 100 proceeds to block B120.

[0090] Block B116 entails determining by the controller 50 whether a low AC current frequency condition exists, again using motor control calibration to do so. When such a condition exists, the method 100 then proceeds to block B118, and when such a condition is not met, the method 100 proceeds to block B120.

[0091] When it is determined at Block B116 that a low AC current frequency condition exists, Block B118 is reached which includes setting the Figure 1 The motor and regenerative torque limits of the electric traction motor 14 and TPIM 20 are based on the Figure 5 The stall torque percentage calculated by B112 in the stall torque limit ( Figure 4 54) and the 100% extended stall torque capability line ( Figure 4 Once the inverter limits are set, the method 100 is then complete, restarting from block B 102 .

[0092] Block B120 includes using the torque limit table to set Figure 1 The motor and regeneration torque limits of the electric traction motor 14 and the TPIM 20 are set. Once the inverter limits are set, the method 100 is then complete, restarting from block B102.

[0093] Now refer to Figure 6 , method 100 may be practiced using a modified method utilizing method 100A, wherein method 100A is fed into Figure 5 In the method 100. Those skilled in the art will appreciate that Figure 1 A driver or operator of the motor vehicle 10 shown in FIG can override the default inverter control settings and / or select a specific inverter strategy or mode using, for example, a knob, dial, or touch input. Figure 6 Modes 1, 2, 3, and n are depicted, where n is one or more additional modes. Thus, modes 1-3 may correspond to Figure 2A -C inverter control strategies 1-3.

[0094] Beginning at block B130 , the controller 50 determines whether the selected mode corresponds to Mode 1 , e.g. Figure 2A If not, blocks B160, B170, and B180 are similarly evaluated to select modes / strategies 2, 3, ..., n, where modes 2 and 3 correspond to Figure 2B and 2C , and mode n is another one or more modes or strategies. That is, Figure 2A The three choices shown in -C are non-limiting and simplified, and therefore, different inverter strategies can be used for different applications. With respect to the operator selection of mode 2, 3 or n, the controller 50 controls the inverter by controlling the inverter according to the corresponding strategy. Figure 1 The TPIM 20 executes blocks B162, B172, and B182 accordingly.

[0095] When block B130 confirms that mode 1 has been selected, the mode 1 Figure 2A Mode 1 is a low road load / "normal" driving mode, the controller 50 proceeds to block B132 and sets the above-described Mode 1 inverter control strategy. The method 100 then proceeds to block B134.

[0096] At block B134, the controller 50 may use the vehicle level input ( Figure 1 Arrow CC I ) to determine whether Mode 1 should be maintained, or whether the controller 50 should instead execute another available mode, such as Mode 2 or 3. For example, the controller 50 may determine whether high brake and accelerator pedal pressures are present, in which case the method 100A proceeds to block B135. If the controller 50 detects low brake and accelerator pressures, the method 100A may alternatively proceed to block B136.

[0097] At block B135, in response to determining at block B134 that high brake and accelerator pedal pressures are present, the controller 50 may transition to the above reference Figure 2B Mode 2 described. Then, method 100A is as described above with respect to Figure 5 The method 100 continues.

[0098] Block B136 may need to use the vehicle level input ( Figure 1 Arrow CC I ), which can be extended beyond those vehicle level inputs described herein to determine if high road loads are present. Figure 2C As mentioned above, such loads may be present during rock crawling maneuvers or during operation in terrain mode. As mentioned above, the latter may be a mode enabled in some motor vehicles 10 for use in low-speed off-road driving in a manner that replicates the feel of four-wheel drive control when operating in the low speed range. When the motor vehicle 10 is equipped with such a mode, the controller 50 may proceed to block B138, where the controller 50 sets the Mode 3 inverter control strategy. As with block B135, the controller 50 then proceeds to Figure 5 Method 100.

[0099] As will be appreciated by those skilled in the art in view of the foregoing disclosure, the present teachings enable the controller 50 to autonomously and / or utilize information from Figure 1 The stall torque capability is increased by reducing the torque limit toward the stall torque gear of FIG. 2 in response to input from the driver of the motor vehicle 10 shown in FIG. This occurs over time within a defined low speed / high current situation while avoiding reaching thermal limits. Different control scenarios are possible, for example, if the stall condition is passed quickly, or if the PWM type and switching frequency can be operated in steady state at maximum torque without reaching thermal limits, as shown in FIG. Figure 2C completely eliminate the stall torque in the same way as in the gear, or if the vehicle is level (arrow CC I ) indicates that the motor vehicle 10 may be operating in a stalled condition for an extended period of time, the torque limit is simply lowered to match the stall torque gear ( Figure 2B ).

[0100] Such as Figure 2A The scenario is to increase the stall torque limit relative to the stall torque gear. As explained above, the duration of maintaining the increased stall torque and corresponding NVH performance is a compromise based on the PWM type and switching frequency selection. For example, a low switching frequency of approximately 2kHz can be used with ZVM to enjoy increased stall torque for an extended duration, but at the expense of NVH effect. The same 2kHz switching frequency as SVPWM, or ZVM at a higher switching frequency of 10kHz, can be used to strike a balance between duration and NVH performance. For SVPWM, on its own, a higher switching frequency of 10kHz can be used to reduce the period of increased stall torque while having the best NVH performance.

[0101] The detailed description and drawings or figures support and describe the present teachings, but the scope of the present teachings is limited only by the claims. Although some best modes and other embodiments for carrying out the present teachings have been described in detail, various alternative designs and embodiments exist for practicing the present teachings as defined in the appended claims. Moreover, the present disclosure expressly includes combinations and subcombinations of the elements and features presented above and below.

Claims

1. A method for increasing electric stall torque limit in a motor vehicle having an electrified powertrain, the electrified powertrain including a traction power inverter module (TPIM) connected to an electric traction motor, the method comprising: receiving, by a controller, a set of vehicle level inputs, wherein the controller is programmed with a default electric stall torque limit; selecting, by the controller, an inverter control strategy as a selected inverter control strategy responsive to the set of vehicle level inputs, the selected inverter control strategy comprising temporarily increasing the default electric stall torque limit and selecting and applying a pulse width modulation (PWM) type at a corresponding pulse width modulation (PWM) switching frequency; and The output states of the traction power inverter module and the electric traction motor are controlled by the controller for a calibrated duration using the selected inverter control strategy.

2. The method according to claim 1, wherein Receiving the set of vehicle level inputs includes receiving a braking request and an acceleration request from a brake pedal sensor and an accelerator pedal sensor, respectively.

3. The method according to claim 1, wherein Receiving the set of vehicle level inputs includes receiving a grade signal from a grade sensor, the grade signal indicating an angle of inclination of the motor vehicle.

4. The method according to claim 1, wherein Receiving the set of vehicle level inputs includes receiving a mode selection signal from a mode selection device, the mode selection signal indicating a selected operating mode of the motor vehicle.

5. The method according to claim 1, wherein When the set of vehicle level inputs indicates a threshold road load, the pulse width modulation type includes space vector pulse width modulation (SVPWM), and the pulse width modulation switching frequency is 10 kHz.

6. The method according to claim 1, wherein When the set of vehicle level inputs indicates a terrain mode or a rock crawling maneuver, the pulse width modulation type is zero vector modulation (ZFM), and the pulse width modulation switching frequency is less than 10 kHz.

7. The method according to claim 1, wherein A preselected inverter control strategy is received by the controller receiving the set of vehicle-level inputs, and wherein selecting the inverter control strategy includes modifying the preselected inverter control strategy in response to the set of vehicle-level inputs.

8. A motor vehicle comprising: a set of wheels; an electrified powertrain having a traction power inverter module (TPIM) and an electric traction motor, wherein the electric traction motor is electrically connected to the traction power inverter module and mechanically coupled to the set of wheels; and a controller programmed with a default electric stall torque limit for the traction power inverter module and the electric traction motor, wherein the controller is configured to: Receive a set of vehicle level inputs; selecting an inverter control strategy as a selected inverter control strategy responsive to the set of vehicle level inputs, the selected inverter control strategy comprising temporarily increasing the default electric stall torque limit, a pulse width modulation (PWM) type, and a corresponding PWM switching frequency; and Output states of the traction power inverter module and the electric traction motor are controlled for a calibrated duration using the selected inverter control strategy.

9. The motor vehicle of claim 8 further comprising a brake pedal having a brake pedal sensor, the set of vehicle level inputs including a brake request signal from the brake pedal sensor.

10. The motor vehicle of claim 8 further comprising an accelerator pedal having an accelerator pedal sensor, said set of vehicle level inputs further comprising an acceleration request signal from said accelerator pedal sensor.

11. The motor vehicle of claim 8, further comprising a slope sensor, wherein The set of vehicle level inputs also includes a grade signal from the grade sensor indicative of an angle of inclination of the motor vehicle.

12. The motor vehicle of claim 8, further comprising a mode selection device, wherein: The set of vehicle level inputs includes a mode selection signal from the mode selection device indicating a selected operating mode of the motor vehicle.

13. The motor vehicle of claim 8, wherein: When the set of vehicle level inputs indicates flat terrain, a threshold traction event, a hill hold maneuver, or a wide-open throttle maneuver, the pulse width modulation type is space vector pulse width modulation (SVPWM), and the pulse width modulation switching frequency is 10 kHz.

14. The motor vehicle of claim 8, wherein: When the set of vehicle level inputs indicates terrain mode, rock crawling maneuvering, descending or ascending grade, a threshold high braking level, or sport mode, the pulse width modulation type is zero vector modulation (ZVM).

15. A motor vehicle according to claim 14, wherein: When the set of vehicle level inputs indicates the terrain mode or the rock crawling maneuver, the pulse width modulation switching frequency is approximately 2 kHz, and when the set of vehicle level inputs indicates an ascending or descending grade, the threshold high braking level, or the sport mode, the pulse width modulation switching frequency is approximately 10 kHz.

16. The motor vehicle of claim 8, wherein: The controller includes a stall torque timer, and wherein the controller is configured to limit the temporary increase of the default electric stall torque limit based on the stall torque timer.

17. A controller having a processor and a memory, having recorded thereon default electric stall torque limits and instructions, wherein: The instructions, when executed by the processor, are configured to cause the controller to: Receive a set of vehicle level inputs; selecting an inverter control strategy as a selected inverter control strategy responsive to the set of vehicle level inputs, wherein the selected inverter control strategy includes temporarily increasing the default electric stall torque limit and temporarily applying a pulse width modulation (PWM) type at a corresponding pulse width modulation (PWM) switching frequency; and Output states of a traction power inverter module and an electric traction motor are controlled for a calibrated duration using the selected inverter control strategy.

18. The controller according to claim 17, wherein: The set of vehicle level inputs includes: a braking request and an acceleration request from a brake pedal sensor and an accelerator pedal sensor, respectively; a grade signal from a grade sensor, the grade signal indicating the tilt angle of the motor vehicle; and a mode selection signal from a mode selection device, the mode selection signal indicating the selected operating mode of the motor vehicle.

19. The controller according to claim 17, wherein: The execution of the instructions by the processor is configured to cause the controller to select the pulse width modulation type of the inverter control strategy from the group consisting of space vector pulse width modulation (SVPWM) and zero vector modulation (ZVM).

20. The controller according to claim 17, wherein: The set of vehicle-level inputs includes a preselected inverter control strategy, and wherein execution of the instructions causes the processor to modify the preselected inverter control strategy in response to the set of vehicle-level inputs.

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