Intelligent vehicle and control logic for managing failures in a dual independent drive unit axle powertrain

Abstract

The present invention relates to an intelligent vehicle and control logic for managing faults in a dual independent drive unit axle powertrain. A control system for operating a dual independent drive unit (DIDU) powertrain, a method for manufacturing / operating such a system, and an electrically driven vehicle with fault management and mitigation of a DIDU axle are proposed. The method for operating a motor vehicle with a DIDU axle includes monitoring first and second drive units (DUs) that are independently operable to drive respective wheels through respective axle shafts of the DIDU axle. A vehicle controller receives an indication of a fault condition in a first DU from a fault sensing module and determines a fault type of the fault condition in response. The controller determines the current speed of the vehicle and determines a corresponding torque limit for each DIDU drive unit based on the fault type and the current vehicle speed. When the torque output of the second DU is constrained to the second torque limit, the torque output of the first DU is concomitantly constrained to the first torque limit.

Description

Technical Field

[0001] The present disclosure generally relates to powertrain systems for electric drive vehicles. More specifically, aspects of the present disclosure relate to fault management and mitigation of electric drive powertrains having dual independent drive unit axles. Background Art

[0002] The motor vehicles currently produced, such as modern automobiles, are initially equipped with a powertrain that operates to propel the vehicle and power the vehicle's onboard electronics. For example, in automotive applications, the vehicle powertrain is typically represented by a prime mover that transmits drive torque to the vehicle's final drive system (e.g., differential, axle shaft (or half shaft, axle shaft), wheels, etc.) through an automatic or manually shifted power transmission. Due to its immediate availability and relatively low cost, light weight, and overall efficiency, automobiles have historically been powered by reciprocating piston internal combustion engine (ICE) assemblies. As some non-limiting examples, such engines include compression ignition (CI) diesel engines, spark ignition (SI) gasoline engines, two-stroke, four-stroke, and six-stroke architectures, and rotary engines. On the other hand, hybrid electric vehicles and all-electric vehicles (collectively referred to as "electrically driven vehicles") utilize alternative power sources to propel the vehicle, and thus minimize or eliminate reliance on fossil fuel-based engines for traction power.

[0003] A full electric vehicle (FEV), colloquially referred to as an "electric vehicle," is an electrically driven vehicle configuration that completely omits an internal combustion engine and accompanying peripheral components from the powertrain system, relying instead on a rechargeable energy storage system (RESS) and traction motors for vehicle propulsion. In a battery-based FEV, the engine components, fuel supply system, and exhaust system of an ICE-based vehicle are replaced by a single or multiple traction motors, a traction battery pack, and battery cooling and charging hardware. In contrast, the powertrain of a hybrid electric vehicle (HEV) employs a variety of traction power sources to propel the vehicle, most commonly combining an internal combustion engine component with a battery-powered or fuel cell-powered traction motor. Because a hybrid electric drive vehicle is able to derive its power from sources other than the engine, the HEV engine can be fully or partially shut down while the vehicle is propelled by the electric motor.

[0004] There are four main standard architectures for vehicle powertrains: front-wheel drive (FWD), rear-wheel drive (RWD), four-wheel drive (4WD), and all-wheel drive (AWD) layouts. As the names imply, a prime mover in a FWD powertrain layout drives only the front two wheels of a two-axle vehicle, while a prime mover in a RWD layout drives only the rear wheels. In contrast, a 4WD layout, including full-time and on-demand variants, is equipped with a transfer case that is controlled by the vehicle operator or a powertrain control module (PCM) to selectively transfer torque from the prime mover to both the front and rear axles. In general, a 4WD powertrain system transfers equal amounts of traction power to both the front and rear axles. Similar to a 4WD architecture, an AWD powertrain layout transmits drive torque to all four wheels of the vehicle. However, unlike on-demand 4WD, conventional AWD vehicles always power all four wheels during in-gear vehicle motion, and unlike full-time 4WD, AWD vehicles often deliver torque to the vehicle axles in unequal proportions.

[0005] With the introduction of HEV drive systems, select AWD powertrains can now utilize a transversely mounted engine and transaxle assembly to deliver drive torque to the main (front) driveline, and when all-wheel drive is desired, a rear-mounted traction motor is used to deliver drive torque to the auxiliary (rear) driveline. In place of the longitudinally mounted engine arrangement with a low-range-gear transfer case of a conventional 4WD vehicle, the HEV AWD layout may implement a power take-off unit (PTU) for selectively connecting the engine and transmission to both the front and rear drivelines. In order to eliminate the inefficiencies associated with the propeller shaft, PTU, and transfer case, some AWD powertrains of electric drive vehicles may employ a front and rear independent drive (FRID) configuration to provide optimized traction, for example, for off-road driving conditions and during vehicle operation in inclement weather. FRID-type powertrains utilize a transversely mounted engine or front electric drive unit (EDU) to deliver drive torque to the front driveline, and utilize a discrete auxiliary EDU to independently deliver drive torque to the rear driveline. Recently, some battery electric vehicle (BEV) powertrains now implement an all-electric FRID powertrain layout with dual independent drive unit (DIDU) axles. Such a FRID DIDU layout employs at least three separate prime movers, each of which is independently operable for delivering drive torque to a corresponding axle or axle half-shafts. Summary of the invention

[0006] This article presents a closed-loop feedback control system with accompanying control logic for operating a DIDU powertrain, a method for manufacturing and a method for operating such a system, and an intelligent electric drive vehicle with fault management and mitigation for FRID DIDU axles. As an example, the DIDU powertrain control technology provides axle fault management in a vehicle with two discrete drive units (DUs) that independently drive corresponding half-axles of the same axle. By coordinating axle torque limits between the faulty DU and the non-faulty DU and optionally between the faulty axle and the non-faulty axle, the powertrain system control can react immediately to detected hardware (HW) or communication (comms) faults. In coordination with the axle torque, the control system can impose an overall vehicle speed limit, enable electronic stability control (ESC), and change the lateral control priority within the resident electronic vehicle motion controller (VMC). The fault management and mitigation control strategies can be adjusted in real time based on vehicle speed, selected driving mode, and / or other dynamic vehicle operating conditions. Five simultaneous actions can be taken to manage the fault condition: (1) the fault axle torque limit is clamped to zero or the expected achievable torque on the faulty DU to ensure accurate prediction of the vehicle dynamics caused by the fault; (2) the relative axle torque limit is clamped to zero or a fault-related value, for example based on the current driving mode, vehicle speed, and fault type; (3) an overall vehicle speed limit is obtained based on the driving mode and fault type to prevent the vehicle from entering an undesirable left-right torque vectoring distribution; (4) the calibration value of the VMC is changed to prioritize or de-prioritize lateral vehicle motion objectives based on the driver mode and fault type; and (5) ESC is enabled based on the fault and driver mode.

[0007] Ancillary benefits of at least some of the disclosed concepts include a DIDU electric drive vehicle that improves vehicle performance by mitigating unexpected vehicle lateral motion (e.g., unexpected yaw) caused by failed axle operation due to a failed half-axle DU. The disclosed control scheme may also help maximize vehicle usage by allowing limited drive torque transfer from a non-faulty DU under predetermined conditions to exclude scenarios where the vehicle becomes immobile. In addition to the above advantages, the disclosed features may also help enhance vehicle drivability, improve powertrain control and response time, and optimize low-mu and off-road driving operations.

[0008] Various aspects of the present disclosure relate to system control logic, closed-loop feedback control techniques, and computer readable media (CRMs) for fault management and mitigation in a DIDU powertrain layout. In one example, a method for operating a motor vehicle including a HEV and FEV powertrain configuration with one or more DIDU axles is presented. The representative method includes, in any order and in any combination with any of the options and features disclosed above and below: monitoring first and second drive units (DUs), such as by a distributed sensor array and a motor control processor (MCP), both independently operable to drive corresponding wheels of a motor vehicle through corresponding axle shafts of the DIDU axles; receiving, such as by a resident or remote vehicle controller, a fault signal indicating a fault condition in a first DU of the DIDU axle from a fault sensing module contained in the MCP; determining, by the vehicle controller, a fault type of the fault condition (e.g., a hardware or communication fault in the DU motor, MCP, or power inverter); determining, such as by a vehicle controller in communication with one or more wheel speed sensors, a real-time or near real-time current vehicle speed of the motor vehicle; determining, by the vehicle controller, a first torque limit for the first DU and a second torque limit for the second DU based in whole or in part on the fault type and the current vehicle speed; and commanding, by the vehicle controller (e.g., via one or more command signals transmitted to the MCP), that a first torque output of the first DU be constrained to the first torque limit and a second torque output of the second DU be constrained to the second torque limit.

[0009] Additional aspects of the present disclosure relate to a closed-loop feedback control system and an intelligent motor vehicle that provides fault management and mitigation for a DIDU axle. As used herein, the terms "vehicle" and "motor vehicle" are used interchangeably and synonymously to include any relevant vehicle platform, such as passenger vehicles (HEV, FEV, BEV, fully and partially autonomous driving, etc.), commercial vehicles, industrial vehicles, tracked vehicles, off-road and all-terrain vehicles (ATV), agricultural equipment, etc. In one example, the motor vehicle includes a body with a passenger compartment, a plurality of wheels mounted to the body, and other standard original equipment. For electric drive vehicle applications, multiple electric drive units operate alone (e.g., for a FEV powertrain) or in combination with an internal combustion engine assembly (e.g., for a HEV powertrain) to selectively drive a plurality of vehicle wheels to thereby propel the motor vehicle.

[0010] Continuing the discussion of the above example, the vehicle includes a DIDU axle operatively mounted to the vehicle body and includes first and second DUs that are independently operable to drive first and second wheels, respectively, and first and second axle shafts that drive and connect the first and second DUs to the first and second wheels, respectively. Another drive axle is operatively mounted to the vehicle body and includes one or more prime movers (ICE or MGU) that are independently operable to drive a second pair of wheels. A resident or remote vehicle controller (e.g., an electronic control unit, a control module, or a network of controllers / modules) receives a fault signal indicating a fault condition in a first DU of the DIDU axle from a fault sensing module. The controller responsively determines the fault type of the fault condition and the current speed of the motor vehicle. The controller then derives a corresponding torque limit for each DU based in whole or in part on the fault type and the current vehicle speed. While the torque output of the second DU is constrained to the second torque limit, the torque output of the first DU is concomitantly constrained to the first torque limit.

[0011] For any of the disclosed systems, methods, and vehicles, determining a torque limit for a faulty (first) DU may include: determining whether the fault type is any of a plurality of predetermined hardware or communication faults; in response to the fault type not being one of the predetermined hardware / communication faults, setting the torque limit for the faulty DU to zero or near zero; and in response to the fault type being one of the predetermined hardware / communication faults, setting the torque limit for the faulty DU to an estimated achievable torque value predicted for the fault type. While constraining the torque outputs of the faulty and non-faulty DUs to their respective torque limits, a maximum speed limit of the motor vehicle may be limited to a base motor speed of an electric traction motor in the faulty DU. While limiting the overall speed limit of the vehicle to the base motor speed and constraining the torque output of the DU, a vehicle controller may activate an electronic stability control system of the vehicle and employ the ESC system to adjust a set of predetermined vehicle dynamics parameters to mitigate or prevent a severe instability condition during driving of the motor vehicle (e.g., measured vehicle yaw rate >> driver-derived yaw rate). In this case, the ESC system may apply one or more friction brakes at different corners of the motor vehicle to counteract the severe instability condition (e.g., to compensate for excessive yaw rate).

[0012] For any of the disclosed systems, methods, and vehicles, upon detecting a fault condition on one of the vehicle's axles, the vehicle controller may proactively confirm that the fault condition is a hardware / communication fault on the DIDU axle, rather than a detected fault associated with another axle. As yet another option, the vehicle controller may determine whether the vehicle's current speed exceeds a predetermined yaw instability speed at which active lateral dynamics control is enabled. If so, the torque limit constraint on the non-faulty DU is removed so that the non-faulty DU can operate at full torque capacity. This may allow the opposing drive unit to help offset undesired lateral motion. However, if the vehicle's current speed does not exceed the predetermined yaw instability speed, the vehicle controller may responsively determine whether the motor vehicle's current driving mode is any of a plurality of predetermined driving modes (e.g., off-road mode, high traction mode, etc.) that enable multi-axle driving capability. If not, the second DU may be disabled because multi-axle driving is not desired. Conversely, if the current driving mode is one of the predetermined driving modes, the controller may determine whether the current vehicle speed is less than a maximum limp home speed associated with the vehicle limp home mode; if not, disable the second DU, and if so, remove the torque limit constraint on the non-faulty DU so that the DU can operate at full torque capacity.

[0013] For any of the disclosed systems, methods, and vehicles, in response to a current speed of the vehicle exceeding a predetermined yaw-instability speed, a propulsion actuator may be employed to control lateral dynamic behavior of the motor vehicle. For example, in response to a yaw error toward a faulty (first) DU exceeding a first maximum yaw error value, a non-faulty (second) DU may be commanded to apply a negative (braking) torque to a second wheel via a second axle shaft to cause yaw-error offset. As yet another option, in response to a yaw error toward a non-faulty (second) DU exceeding a second maximum yaw error value, a non-faulty (second) DU may be commanded to apply a positive (accelerating) torque to a second wheel via a second axle shaft to cause yaw-error offset.

[0014] For any of the disclosed systems, methods, and vehicles, the vehicle controller may include a discrete vehicle motion controller, and the fault sensing module may include a discrete motor process controller in communication with the VMC and one or more electronic sensing devices. In this case, the electronic sensing device may monitor the back electromotive force (EMF) induced by one or both DUs on a high voltage (HV) electrical bus connecting the DUs to the traction battery pack. The MCP detects a fault condition in response to the back EMF induced on the HV electrical bus exceeding a DC link voltage threshold. In response to detecting the fault condition, the MCP sends one or more fault signals to the VMC. The fault type may be a hardware or communication fault that causes the DU to operate in an uncontrolled generation (UCG) mode, during which the faulty DU uncontrollably generates electrical power that is delivered to the HV traction battery pack via the HV electrical bus.

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

[0016] Solution 1. A method of operating a motor vehicle having a dual independent drive unit (DIDU) axle, the DIDU axle comprising a first drive unit (DU) and a second DU, both of which are capable of being individually operated to independently drive a first wheel and a second wheel respectively, the method comprising:

[0017] receiving, by a vehicle controller, a fault signal from a fault sensing module indicating a fault condition in the first DU of the DIDU axle;

[0018] determining, by the vehicle controller, a fault type of the fault condition;

[0019] determining, by the vehicle controller, a current vehicle speed of the motor vehicle;

[0020] determining, by the vehicle controller, a first torque limit for the first DU and a second torque limit for the second DU based on the fault type and the current vehicle speed; and

[0021] A first torque output of the first DU is constrained to the first torque limit and a second torque output of the second DU is constrained to the second torque limit via a command from the vehicle controller.

[0022] Solution 2. The method according to solution 1, wherein determining the first torque limit of the first DU of the DIDU axle operating under the fault condition comprises:

[0023] determining whether the fault type is any one of a plurality of predetermined hardware or communication (HW / comms) faults;

[0024] In response to the fault type not being one of the predetermined hardware / communication faults, setting the first torque limit to zero or near zero; and

[0025] In response to the fault type being one of the predetermined hardware / communication faults, the first torque limit is set to an estimated achievable torque value corresponding to the fault type.

[0026] Option 3. The method of option 1 further includes limiting a maximum vehicle speed limit of the motor vehicle to a base motor speed of an electric traction motor in the first DU while constraining the first torque output and the second torque output of the first DU and the second DU.

[0027] Option 4. The method according to Option 3 further includes, while limiting the maximum vehicle speed limit to the base motor speed and constraining the first torque output and the second torque output of the first DU and the second DU:

[0028] activating an electronic stability control (ESC) system of the motor vehicle; and

[0029] A set of predetermined vehicle dynamics parameters are controlled by the ESC system to mitigate or prevent severe instability conditions during driving of the motor vehicle.

[0030] Option 5. A method according to Option 1, wherein the vehicle includes a drive axle different from the DIDU axle that is independently driven by a prime mover different from the first DU and the second DU, and the method also includes confirming that the fault condition is a hardware or communication failure in the first DU of the DIDU axle, rather than a detected fault associated with the drive axle.

[0031] Solution 6. The method according to Solution 1 further includes:

[0032] determining whether the current vehicle speed of the motor vehicle exceeds a predetermined yaw instability speed at which active lateral dynamics control is enabled; and

[0033] In response to the current vehicle speed exceeding the predetermined yaw instability speed, the second torque limit constraining the second DU is removed.

[0034] Solution 7. The method according to Solution 6 further includes: in response to the current vehicle speed not exceeding the predetermined yaw instability speed:

[0035] determining whether a current driving mode of the motor vehicle is any one of a plurality of predetermined driving modes that enable multi-axle driving capability of the motor vehicle; and

[0036] In response to the current driving mode of the motor vehicle not being one of the predetermined driving modes, the second DU is disabled.

[0037] Solution 8. The method according to Solution 7 further includes, in response to the current driving mode of the motor vehicle being one of the predetermined driving modes:

[0038] determining whether the current vehicle speed is less than a limp home mode maximum speed;

[0039] In response to the current vehicle speed being not less than the limp home mode maximum speed, disabling the second DU; and

[0040] In response to the current vehicle speed being less than the limp home mode maximum speed, the second torque limit constraining the second DU is removed.

[0041] Option 9. The method according to Option 6 further includes using a propulsion actuator to control the lateral dynamic behavior of the motor vehicle in response to the current vehicle speed exceeding the predetermined yaw instability speed.

[0042] Option 10. A method according to Option 9, wherein using the propulsion actuator to control the lateral dynamic behavior of the motor vehicle includes: in response to a yaw error toward the first DU exceeding a first maximum yaw error value, commanding the second DU to apply a negative torque to the second wheel via a corresponding axle shaft to cause yaw error compensation.

[0043] Option 11. A method according to Option 9, wherein using the propulsion actuator to control the lateral dynamic behavior of the motor vehicle includes: in response to a yaw error toward the second DU exceeding a second maximum yaw error value, commanding the second DU to apply a positive torque to the second wheel via a second axle shaft to cause yaw error compensation.

[0044] Embodiment 12. The method of embodiment 1, wherein the vehicle controller comprises a vehicle motion controller (VMC), wherein the fault sensing module comprises a motor control processor (MCP) in communication with an electronic sensing device, and wherein receiving the fault signal comprises:

[0045] monitoring, by the electronic sensing device, a back electromotive force (EMF) induced by the first DU on a high voltage (HV) electrical bus connected to the first DU;

[0046] detecting, by the MCP, a fault condition in response to the back EMF induced on the HV electrical bus exceeding a DC link voltage threshold; and

[0047] In response to detecting the fault condition, the fault signal is sent to the VMC via the MCP.

[0048] Option 13. The method according to Option 12, wherein the fault type is a hardware or communication (HW / comms) fault, and the fault causes the first DU to operate in an uncontrolled generation (UCG) mode, during which the first DU uncontrollably generates electric power, which is transmitted to the high-voltage traction battery pack through the HV electrical bus.

[0049] Solution 14. An electric drive vehicle, comprising:

[0050] a vehicle body having a first pair of wheels and a second pair of wheels;

[0051] a dual independent drive unit (DIDU) axle mounted to the vehicle body and comprising: a first drive unit and a second drive unit (DU) operable individually to independently drive a first wheel and a second wheel of the first pair of wheels, respectively; and a first axle half-shaft and a second axle half-shaft drivingly connecting the first DU and the second DU to the first wheel and the second wheel, respectively;

[0052] a drive axle mounted to the vehicle body at the front or rear of the DIDU axle and including a prime mover independently operable to drive the second pair of wheels; and

[0053] A vehicle controller programmed to:

[0054] receiving a fault signal from a fault sensing module indicating a fault condition in a first DU of a DIDU shaft;

[0055] determining a fault type of the fault condition;

[0056] determining a current vehicle speed of the electrically driven vehicle;

[0057] determining a first torque limit for the first DU and a second torque limit for the second DU based on the fault type and the current vehicle speed; and

[0058] A first torque output of the first DU is constrained to the first torque limit, and a second torque output of the second DU is constrained to the second torque limit.

[0059] Embodiment 15. The electrically driven vehicle of embodiment 14, wherein the vehicle controller determines the first torque limit of the first DU of the DIDU axle operating under the fault condition comprises:

[0060] determining whether the fault type is any one of a plurality of predetermined hardware or communication (HW / comms) faults;

[0061] In response to the fault type not being one of the predetermined hardware / communication faults, setting the first torque limit to zero or near zero; and

[0062] In response to the fault type being one of the predetermined hardware / communication faults, the first torque limit is set to an estimated achievable torque value corresponding to the fault type.

[0063] Option 16. An electrically driven vehicle according to Option 14, wherein the vehicle controller is further programmed to limit the maximum vehicle speed of the electrically driven vehicle to a base motor speed of an electric traction motor in the first DU while constraining the first torque output and the second torque output of the first DU and the second DU.

[0064] Embodiment 17. The electrically driven vehicle of embodiment 16, wherein the vehicle controller is further programmed to, while limiting the maximum vehicle speed limit to the base motor speed and constraining the first torque output and the second torque output of the first DU and the second DU:

[0065] activating an electronic stability control (ESC) system of the vehicle; and

[0066] A set of predetermined vehicle dynamics parameters are controlled by the ESC system to mitigate or prevent severe instability conditions during driving of the electrically driven vehicle.

[0067] Embodiment 18. The electrically driven vehicle according to embodiment 14, wherein the vehicle controller is further programmed to:

[0068] determining whether the current vehicle speed of the electrically driven vehicle exceeds a predetermined yaw instability speed for enabling active lateral dynamics control; and

[0069] In response to the current vehicle speed exceeding the predetermined yaw instability speed, the second torque limit constraining the second DU is removed.

[0070] Embodiment 19. The electrically driven vehicle of embodiment 18, wherein the vehicle controller is further programmed to: in response to the current vehicle speed not exceeding the predetermined yaw instability speed:

[0071] determining whether a current driving mode of the motor vehicle is any one of a plurality of predetermined driving modes that enable multi-axle driving capability of the vehicle; and

[0072] In response to the current driving mode of the electrically-driven vehicle not being one of the predetermined driving modes, the second DU is disabled.

[0073] Embodiment 20. The electrically driven vehicle according to embodiment 19, wherein the vehicle controller is further programmed to: in response to the current driving mode of the electrically driven vehicle being one of the predetermined driving modes:

[0074] determining whether the current vehicle speed is less than a limp home mode maximum speed;

[0075] In response to the current vehicle speed being not less than the limp home mode maximum speed, disabling the second DU; and

[0076] In response to the current vehicle speed being less than the limp home mode maximum speed, the second torque limit constraining the second DU is removed.

[0077] The above summary does not represent every embodiment or every aspect of the present disclosure. On the contrary, 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 combined with the accompanying drawings and the appended claims. In addition, the present disclosure expressly includes any and all combinations and sub-combinations of the elements and features presented above and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is a schematic diagram of a representative electric drive vehicle having a front and rear independent drive (FRID) powertrain with a dual independent drive unit (DIDU) rear axle configuration in accordance with aspects of the disclosed concept.

[0079] Figure 2 is a flow chart illustrating a representative fault management and mitigation control scheme for operating a DIDU axle of an electric drive vehicle in accordance with aspects of the disclosed concepts, which may correspond to memory stored instructions executable by a resident or remote controller, control logic circuit, programmable control unit, or other integrated circuit (IC) device or network of devices.

[0080] Representative embodiments of the present disclosure are shown in the accompanying drawings by way of non-limiting examples and are described in more detail below. However, it should be understood that the novel aspects of the present disclosure are not limited to the specific forms shown in the drawings listed above. Instead, the present disclosure will cover all modifications, equivalent forms, combinations, sub-combinations, permutations, groupings, and substitutions that fall within the scope of the present disclosure as, for example, covered by the appended claims. DETAILED DESCRIPTION

[0081] The present disclosure allows for embodiments in many different forms. Representative examples of the present disclosure are shown in the accompanying drawings and are described in detail herein with the understanding that these embodiments are provided as illustrations of the disclosed principles, rather than limitations on the broad aspects of the present disclosure. To this end, elements and limitations described in the "Abstract," "Technical Field," "Background Technology," "Summary of the Invention," "Description of the Drawings," and "Specific Implementation Methods" sections, but not explicitly set forth in the claims, should not be incorporated into the claims individually or collectively by implication, inference, or otherwise. In addition, the drawings discussed herein may not be drawn to scale and are provided purely for guidance purposes. Therefore, the specific and relative dimensions shown in the drawings should not be interpreted as limiting.

[0082] For purposes of this detailed description, unless otherwise stated: the singular includes the plural and vice versa; the terms "and" and "or" shall be both conjunctions and transitional conjunctions; the terms "any" and "all" shall both mean "any and all"; and the terms "including," "comprising," "containing," "having," and their permutations shall each mean "including but not limited to." In addition, approximate terms such as "approximately," "almost," "substantially," "roughly," "approximately," and the like may each be used herein in a sense such as "at, approximately, or nearly at," or "within 0-5% of," or "within an acceptable manufacturing tolerance," or any logical combination of the foregoing. Finally, directional adjectives and adverbs such as head, tail, inboard, outboard, starboard, port, vertical, horizontal, upward, downward, front, rear, left, right, and the like may be relative to a motor vehicle, such as relative to a forward direction of travel of a motor vehicle, when the vehicle is operatively oriented on a level running surface.

[0083] Referring now to the drawings, wherein like reference numerals represent like features throughout the several views, Figure 1 A schematic diagram of a representative automobile is shown in the drawings, which is generally indicated at 10 and is depicted herein for the purposes of discussion as a sedan-style electric drive passenger car. The illustrated automobile 10, also referred to herein as a "motor vehicle" or simply "vehicle," is merely an exemplary application with which the novel aspects of the present disclosure may be practiced. Likewise, incorporating the present concepts into an all-electric AWD powertrain should also be understood as a non-limiting implementation of the disclosed features. As such, it will be understood that the various aspects and features of the present disclosure may be applied to other FEV and HEV powertrain architectures, may be used for alternative drivetrain layouts, and may be implemented for any logically related type of vehicle. In addition, only selected components of the motor vehicle and vehicle control system are shown and described in greater detail herein. Nevertheless, the vehicles and vehicle systems discussed below may include many additional and alternative features, as well as other available peripheral components for performing the various methods and functions of the present disclosure.

[0084] Figure 1 The electric drive vehicle 10 is an example of a DIDU battery electric vehicle equipped with a multi-mode, FRID-type electrified powertrain that enables on-demand all-wheel drive capability by simultaneously transmitting propulsion torque to multiple wheels from three independently operable electrified drive units that employ electric motors as prime movers. The AWD BEV powertrain of the vehicle 10 is shown as having a split-branch architecture, namely: a front (first or primary) powertrain PTF branch at the front end of the vehicle body 15; and a rear (second or auxiliary) powertrain PTR branch at the rear of the front powertrain PTF at the rear end of the vehicle body 15. In this example, the front powertrain PTF can be represented by a front (first) axle 11 for driving a left front (front passenger side) drive wheel 16 and a right front (front driver side) drive wheel 17. Similarly, the rear powertrain PTR can be represented by a rear (second) axle 13 that drives a left rear (rear passenger side) wheel 18 and a right rear (rear driver side) wheel 19. Although Figure 1 The vehicle 10 is shown as having a single DIDU axle on the rear axle 13, but it should be appreciated that the electrically driven vehicle 10 may utilize multiple DIDU axles, a single DIDU axle on the front axle 11, three or more axles, etc. The disclosed features are similarly applicable to DIDU FWD vehicles and DIDU RWD vehicles having a single driven axle.

[0085] To propel the vehicle 10 during the FWD or AWD operating modes, a first prime mover, which may be in the nature of a front (main) drive unit 20, generates tractive torque for driving the two front drive wheels 16, 17. Packaged within the front drive unit 20 is an electric traction motor 22, which is mechanically coupled to the left and right front wheels 16, 17 through a front (first) drive train 25. According to the illustrated example, the front drive train 25 utilizes an integrated transmission, differential and axle (transaxle) unit 26 with independent half shafts 27 for coupling the motor 22 to the wheels 16, 17. A front (first) power inverter module (PIM) 24 electrically connects the drive unit motor 22 to the rechargeable energy storage system (RESS) 14. For a fully integrated drive unit assembly, the motor, inverter and transmission of the DU 20, 30, 40 are packaged as a single configuration with internal cooling and high specific power capabilities.

[0086] Operation of the front drive unit 20 and the associated PIM 24 is provided by a resident vehicle controller 50, which may include any one or more of a powertrain control module (PCM), an advanced driver assistance system (ADAS) module, an electronic battery control module (EBCM), a brake system control module (BSCM), etc. For example, in response to a braking command, such as from the BSCM of the vehicle controller 50, the left and right front (disc, drum or air) friction brakes 28 and 29 are selectively engaged to decelerate the left and right front drive wheels 16, 17, respectively. The high voltage electrical bus 12 couples the three drive units 20, 30, 40 of the vehicle to the RESS 14. In at least some embodiments, the RESS 14 is configured as a multi-battery lithium-ion device capable of charging and discharging under a range of conditions. Although depicted as a single prime mover having the properties of a traction motor, the front powertrain PTF may employ multiple traction motors, an internal combustion engine, or a hybrid combination of an engine and a motor.

[0087] To propel the vehicle 10 during the AWD or RWD (if available) operating modes, second and third prime movers, which may be in the nature of a left rear (first auxiliary) drive unit 30 and a right rear (second auxiliary) drive unit 40, generate tractive torque for independently driving the rear drive wheels 18, 19. Packaged within the left rear drive unit 30 is a first auxiliary electric traction motor 32, which is mechanically coupled to the left rear wheel 18 through a left rear (passenger side) driveline 35. Likewise, a second auxiliary electric traction motor 42 is packaged within the right rear drive unit 40 and mechanically coupled to the right rear wheel 19 through a right rear (driver side) driveline 45. The left rear driveline 35 couples the motor 32 to the left rear drive wheel 18 using an independent differential unit 36 ​​and a dedicated rear half shaft 37. Likewise, the right rear driveline 45 couples the motor 42 to the right rear drive wheel 19 using its own independent differential unit 46 and a dedicated rear half shaft 47. For at least some desired applications, each traction motor 22 , 32 , 42 is a multi-phase AC permanent magnet (PM) motor generator unit (MGU).

[0088] The left rear (second) power inverter module 34 electrically connects the left rear drive unit motor 32 to the RESS 14 via the bus 12, and the right rear (third) power inverter module 44 electrically connects the right rear drive unit motor 42 to the RESS 14 via the bus 12. Independent operation of the rear drive units 30, 40 and their respective PIMs 34, 44 may also be provided by the resident vehicle controller 50. Each PIM 24, 34, 44 is an element of the DU power electronic control (PEC) subsystem, which regulates the transmission of electrical energy to and from the traction motors 22, 32, 42, and when desired, converts high-voltage direct current (DC) power to three-phase alternating current (AC) power as needed, and vice versa. The traction PIM may include a set of power inverters, high-speed transistors and capacitor-based filters, and motor control hardware to receive motor control commands for providing motor drive and regeneration functions. In response to associated braking commands, such as from the vehicle controller 50 , the left and right rear friction brakes 38 and 39 are selectively engaged, respectively, to decelerate the left and right rear wheels 18 , 19 .

[0089] RESS 14 is suitable for storage and supply of propulsion Figure 1 The RESS may be a deep cycle, high ampere capacity battery system rated for approximately 350 to 800 VDC or higher, for example, depending on the desired vehicle range, gross vehicle weight, and the power ratings of various accessory loads that draw electrical power from the RESS. To this end, the RESS may employ one or more high voltage, high energy density battery packs that are electrically connected to the drive unit motor. Traction battery packs are typically composed of an array of lithium ion rechargeable (secondary) battery modules. These battery modules may be arranged in a pattern of rows and columns and may be supported on a battery support tray or encapsulated in a battery pack housing. Various aspects of the disclosed concepts may be similarly applicable to other electrical storage unit architectures, including those that employ nickel metal hydride (NiMH) batteries, lead acid batteries, lithium polymer batteries, or other applicable types of rechargeable electric vehicle batteries (EVBs). Each battery module may include a series of electrochemical battery cells, such as stacked pouch-type lithium ion (Li-ion) or lithium ion polymer battery cells.

[0090] As described above, the vehicle controller 50 is constructed and programmed to control selected operations of the motor vehicle 10, including Figure 1. Control modules, modules, controllers, control units, electronic control units, processors, microprocessors and any arrangement thereof are used interchangeably and synonymously to represent any one or various combinations of one or more of logic circuits, combinational logic circuits, application specific integrated circuits (ASICs), electronic circuits, central processing units (e.g., microprocessors, semiconductor IC devices), input / output circuits and devices, appropriate signal conditioning and buffering circuits, and other components such as high-speed clocks 53 that provide the described functions. Associated storage devices and memory 51 (e.g., read-only, programmable read-only, random access, hard drive, tangible, etc.), whether resident, remote, or a combination of both, store software and / or firmware programs or routines executable by the processor.

[0091] Software, firmware, programs, instructions, routines, codes, algorithms and similar terms are used interchangeably and synonymously to represent any processor executable instruction set, including calibration and lookup tables. The vehicle controller 50 can be designed to have a set of control routines that are executed to provide the desired functions. The control routines are executed, for example, by a central processing unit and are operable to monitor inputs from sensing devices and other networked control modules, and to perform control and diagnostic routines to control the operation of devices and actuators. Such inputs may include vehicle speed and acceleration data, speed limit data, traffic light status and position data, road slope data, stop sign position data, traffic flow data, geospatial data, road and lane level data, vehicle dynamics data, sensor data, etc. Routines may be executed in real time, continuously, systematically, sporadically and / or at regular intervals during vehicle use, for example, every 100 microseconds, every 3.125 milliseconds, 6.25 milliseconds, 12.5 milliseconds, 25 milliseconds, and 100 milliseconds, etc. Alternatively, the routine may be executed during operation of the vehicle 10 in response to the occurrence of an event.

[0092] During operation of the electric drive vehicle 10, the AWD BEV powertrain may experience a fault condition that renders one or more of the drive units 20, 30, 40 inoperable or ineffective. As an illustration, one of the drive units 30, 40 on the rear DIDU axle 13 may experience an uncontrolled generation (UCG) fault caused by magnetic induction of the traction motor 32, 42, thereby inducing a reverse (reverse) EMF on the HV electrical bus 12 that exceeds the DC link voltage. The UCG fault condition may cause the motor to uncontrollably generate electrical power, which may be transferred to the on-board battery module of the RESS 14 via the HV bus 12. Such an operating state may increase the likelihood of undesirable lithium plating on the battery cell electrodes, tabs, and busbars, and may cause an unexpected vehicle deceleration event when the faulty DU is operated to provide propulsion torque. On a vehicle with a DIDU axle that employs multiple independently operable drive units for vehicle propulsion, a UCG fault in one of the traction motors may cause unintended lateral motion (ULM) of the vehicle.

[0093] In BEV applications with two independent drive units on a single axle, if one of the drive units fails, such as motor winding / cage failure, half-axle failure failure, PIM door failure, etc., the vehicle may lose lateral stability due to unexpected left-right torque vectoring. Discussed below is a control strategy that provides system automated fault response to manage and minimize undesirable vehicle dynamics while maximizing system availability to prevent vehicle fixation. Five powertrain system control actions can be taken in a coordinated manner to manage and mitigate the detected fault condition, namely: set axle torque limit at the faulty DU; set axle torque limit at one or more non-faulty DUs; apply vehicle speed limit; adjust VMC control priority; enable electronic stability control. For example, the torque limit for the faulty DU can be clamped to an estimated "achievable" torque value or range to ensure that vehicle motion control can predict the vehicle dynamics caused by the fault. When a motor failure occurs, the torque may no longer be controllable; the faulty motor may produce torque based on the operating conditions and the fault action taken by the monitoring system. To allow motor control to understand the situation and take appropriate action, the MCP may calculate a best estimate of the torque that the faulty motor would produce ("achieved") under current operating conditions, and may clamp both maximum and minimum motor torque limits, which typically represent the controllable and achievable torque range, to the current estimated faulty motor torque.

[0094] For example, the torque limit for the opposing non-faulty DU may be clamped to zero or a predetermined limit depending on the current driving mode, vehicle speed, fault type, etc. For example, a maximum vehicle speed limit may be enforced based on the vehicle driving mode and fault type to prevent the vehicle from entering an unstable condition. For example, VMC control calibration values ​​may be modified to prioritize or deprioritize vehicle lateral motion objectives based on the driving mode and fault type. If disabled, electronic stability control or other ADAS automation systems may be reactivated, for example, depending on the fault type and vehicle driving mode.

[0095] Next reference Figure 2 , according to aspects of the present disclosure, generally depicts a process for controlling a motor vehicle, such as a Figure 1 The DIDU axle of the electric drive vehicle 10, for example Figure 1 The improved method or control strategy for implementing fault management and mitigation for the rear axle 13 is provided. Figure 2 Some or all of the operations illustrated in the drawings and described in further detail below may represent an algorithm corresponding to processor-executable instructions, which may be stored, for example, in main memory or in secondary or remote memory (e.g., Figure 1 51 ) and, for example, by an electronic controller, processing unit, logic circuit or other module or device or network of modules / devices (e.g., Figure 1 The controller 50 of the embodiment of the present invention is executed to perform any or all of the functions described above and below associated with the disclosed concept. It should be appreciated that the execution order of the illustrated operation blocks can be changed, additional operation blocks can be added, and some of the operations described can be modified, combined or eliminated.

[0096] Figure 2 The method 100 begins at terminal block 101, where a memory stores processor-executable instructions for a programmable controller or control module or similar suitable processor to call an initialization program for a fault management control scheme. The routine may be executed in real time, continuously, systematically, occasionally and / or at regular intervals, such as every 10 or 100 milliseconds during normal and ongoing operation of the motor vehicle 10. As a further option, terminal block 101 may be initialized in response to a user command prompt, a resident vehicle controller prompt, or a broadcast prompt signal received from an "off-board" centralized vehicle service system (e.g., a host cloud computing service). Upon completion Figure 2 After the control operations presented in , method 100 may proceed to terminal block 119 and terminate temporarily, or alternatively may loop back to terminal block 101 and run in a continuous loop.

[0097] Proceeding from terminal block 101, method 100 detects an axle / drive unit fault at process block 103, and upon detection of a fault, determines at decision block 105 what type of fault has occurred. As explained above, a UCG condition may occur when the back EMF of the three-phase PM motor is higher than the HV DC bus voltage. For example, a motor control processor (MCP) 31 resident to the left rear auxiliary drive unit 30 may prompt the bus-side electronic voltage sensor 33 to monitor the voltage output from the motor 32 to the HV bus 12, including the back EMF. When the auxiliary electric traction motor 32 is operated at a high rotational speed and works as a generator, an unlimited feed of electric power generated by the motor may be transmitted back to the RESS 14. Due to the generation of DC power in this UCG mode, the motor 32 of the now faulty drive unit 30 may begin to generate a braking torque on the drive wheels 18 that is dependent on the motor speed and characteristics. The UCG mode may be caused by a defect in the motor 32, a MCP 31 processor failure, or a PIM 34 inverter gate driver failure. Thus, a UCG fault may be flagged when the back EMF is above the DC bus voltage, and by monitoring for hardware and communication failures that would cause motor runaway. If the detected fault is not one of a set of predetermined axle hardware or communication (HW / comms) faults that each trigger DIDU fault management (block 105 = No), the method 100 may temporarily end at terminal block 119.

[0098] After confirming that the detected fault is an axle HW / comms fault that triggers DIDU fault management (block 105 = yes), the method 100 provides logic to set maximum and minimum torque limits for the faulty drive unit. Figure 2 , the method 100 continues to decision block 107 to determine whether the fault type is a fault type for UCG that affects back EMF. In response to a detected fault, such as a motor position sensor fault or a PIM inverter gate fault that results in a UCG condition (block 107=yes), a faulty (first) motor torque limit or torque limit range for the traction motor 32 of the faulty (first rear) drive unit 30 is set to an estimated achievable torque value or torque range predicted for the associated fault type, as shown at process block 109. As a non-limiting example, a desktop hardware-in-the-loop (HIL) simulator may predict the maximum and minimum achievable torques at which a faulty DU motor may operate in a faulty state without causing sufficient back EMF to sustain a UCG condition. With knowledge of the fault torque generated at the affected corner, the VMC may utilize a chassis model of the target vehicle within its control function to predict the dynamic response of the vehicle. However, if the detected fault is not a fault type that causes unlimited torque generation (eg, UCG of back EMF), such as an axle shaft or differential HW fault, the fault (first) motor torque limit is set to zero (0) or near zero, as shown at process block 111 .

[0099] While limiting the torque output of the drive units 30, 40 of the DIDU rear axle 13, the method 100 executes process block 113 and sets the maximum vehicle speed limit that the motor vehicle can travel under the fault condition to the motor calibrated base speed of the traction motor 32 in the faulty drive unit 30. The base speed of the motor can be the "nameplate rated" starting speed at which the terminal voltage of the motor becomes the rated voltage. The base motor speed can be the maximum rotor speed at which the motor can operate under constant torque characteristics or the minimum rotor speed at which it can operate at rated power. Another possibility for such a speed selection is a motor speed at which the motor can rotate freely without generating uncontrolled torque or causing component damage.

[0100] In addition to limiting the overall speed limit of the vehicle and constraining the torque output of the DIDU drive units, the method 100 proceeds to process block 115 to activate the vehicle's electronic stability control system and employ the ESC actuators to control a set of predetermined vehicle dynamics parameters to mitigate or prevent a severe instability condition during driving of the faulty vehicle. A "severe instability condition" may be defined as a dynamic driving condition in which the actual (measurable) yaw rate of the vehicle differs significantly from the desired (driver-commanded) yaw rate. A simplified example would be a driver holding the steering wheel steadily to steer the vehicle along a substantially straight path along a road, effectively inputting a desired vehicle yaw rate of zero. However, a fault occurring in one of the rear DUs 30, 40 may produce a condition that causes the vehicle body 15 to yaw in a clockwise direction ( Figure 1 To mitigate this severe instability condition, the ESC system may selectively apply and / or adjust one or more of the friction brakes 28, 29, 38, 39 to help counteract the associated yaw rate. The ESC system may be operable to output friction braking commands to individual wheels and all wheels of the vehicle.

[0101] Continue to refer Figure 2, method 100 executes decision block 117 to confirm that the fault condition is a HW / comms fault on a DIDU axle (e.g., rear axle 13) and not a detected fault associated with another available driven axle (e.g., front axle 11). Decision block 117 may be used as a preventative assessment to ensure that DIDU fault management and mitigation are only performed during a predetermined DIDU fault condition. To this end, decision block 117 may be executed before or concurrently with block 103 or block 105 to preemptively terminate method 100 before performing redundant operations. In response to determining that the fault is not on a DIDU axle (block 117=no), method 100 proceeds to terminal block 119 and either terminates, loops back to terminal block 101, or proceeds to an alternative fault management scheme for a non-DIDU related fault. For example, a vehicle may have two driven axles (e.g., FRID architecture) without dual independent drive units on either axle. If an axle fails, torque limiting can be applied to the failed motor, maximum / minimum speed limits can be enforced on the vehicle, and ESC can be enabled for active vehicle dynamics control. Additionally, the vehicle can implement a single-axle limp home mode.

[0102] After confirming that the fault occurs on an axle with dual independent drive units (block 117 = yes), the method 100 proceeds to decision block 121 and determines whether the current speed of the vehicle exceeds a predetermined yaw instability speed at which active lateral dynamics control is enabled or desired. Figure 1 During forward travel of the automobile 10, the real-time vehicle speed may be relatively slow (e.g., below 30-35 mph) such that any unintentional braking torque applied by the faulty DU 30 will not significantly amplify vehicle yaw. In contrast, when the real-time vehicle speed exceeds a predetermined yaw destabilization speed (e.g., 40+ mph), the UCG fault condition may produce a large braking torque at the faulty axle half, which will require active compensation dynamics to achieve yaw rate control. The real-time or near real-time vehicle speed may be determined by any available means, including variable reluctance (passive) and reluctance (active) wheel speed sensors (WSS). For some embodiments, after the vehicle speed decreases to a speed below the predetermined yaw destabilization speed, the method 100 may responsively disable the entire rear axle 13, causing the automobile 10 to operate as a single-axle FWD vehicle. One reason to disable the non-faulty "good" drive unit in this case is to ensure that the drive unit is not operating at full capacity, which may cause the vehicle to "feel more agile" on one side of the vehicle relative to the other. This potential imbalance of the vehicle may not be desirable except in specific circumstances required by the driver-selected driving mode.

[0103] In response to determining that the current speed of the vehicle is below a predetermined yaw instability speed (block 121=no), the method 100 executes decision block 123 to determine whether the current driving mode of the motor vehicle is any of a plurality of predetermined multi-axle driving modes that enable the AWD driving capability of the motor vehicle 10. In a representative example, the resident vehicle controller 50 may determine whether the vehicle is in an off-road "terrain" mode or in a high traction "low μ" mode. In direct response to determining that the vehicle is not operating in any multi-axle drive mode (block 123=no), the method 100 may execute process block 125 and set the non-faulty (second) motor torque limit or torque limit range of the traction motor 42 of the non-faulty (second rear) drive unit 40 to zero. In doing so, the "good" drive unit 40 is effectively disabled because no torque output via the rear axle 13 is deemed necessary at this time.

[0104] Upon determining that the target vehicle is currently operating in one of the available multi-axle drive modes (block 123=yes), the method 100 executes decision block 127 to determine whether the current speed of the vehicle is less than the limp mode maximum speed. "Limp mode" is the most common on-board diagnostic (OBD) system feature that is activated when a serious motor or axle failure is detected to prevent further damage to the vehicle powertrain. Once triggered, limp mode typically limits engine output, limits vehicle speed (e.g., up to 35 mph or 40 mph), and may even disable all non-critical accessories (e.g., HVAC and radio use) and prevent transmission shifting. If the current speed of the vehicle is above the limited maximum speed of the limp mode (block 127=no), the method 100 may execute process block 125 and disable the non-faulty (second rear) drive unit 40.

[0105] In response to determining that the current speed of the vehicle is less than the limp mode maximum speed (block 127=yes), the method 100 executes process block 129 and removes any torque limiting constraints on the non-faulty (second rear) drive unit 40, so that the "good" DU on the "good" axle half-axle can operate at full torque capacity. Similarly, if the vehicle is operating in a multi-axle drive mode (block 123=yes) and the current vehicle speed is less than the limp mode maximum speed (block 127=yes), the method 100 executes process block 129 and removes any torque limiting constraints on the non-faulty (second rear) drive unit 40. In both of the above scenarios, the vehicle controller 50 may conclude that torque output is required from the front axle 11 and the rear axle 13. Enabling the non-faulty DU of the DIDU axle to operate with the faulty DU disabled may involve an asymmetric manner of vehicle propulsion; this capability may be limited to a predetermined low speed and therefore disabled at higher vehicle speeds. As a further option, for a vehicle DIDU powertrain layout with a single driven axle, a special "asymmetric" limp home mode can be implemented which enables the non-faulty "good" drive unit to operate with limited torque output at a predetermined low vehicle speed. This special drive mode can be enabled regardless of the current vehicle speed and the current drive mode.

[0106] In addition to adjusting the torque output of each drive unit, limiting the maximum speed of the vehicle, and implementing ESC to improve severe instability conditions, the method 100 may also perform process block 131 to employ one or more available propulsion actuators to manage the lateral dynamic behavior of the subject vehicle. To perform lateral dynamic management, the method 100 may first receive a desired (driver input) yaw rate through data input block 133 and an actual (measured) yaw rate through data input block 135. A "propulsion actuator" may include any available controller-actuated powertrain device operable to manipulate vehicle dynamics control. For example, in response to a yaw error toward the first rear DU 30 exceeding a predetermined (first) maximum yaw error value, the auxiliary electric traction motor 42 of the right rear drive unit 40 may be commanded to apply a negative torque to the right rear wheel 19 via the rear half shaft 47 to cause a reactive (first) "error compensation" yaw. Alternatively, in response to the yaw error towards the second rear DU 40 exceeding a predetermined (second) maximum yaw error value, the auxiliary electric traction motor 42 may be controlled to apply positive torque to the right rear wheel 19 to induce a reactive (second) “error compensating” yaw.

[0107] To regain control of the vehicle and restore vehicle stability during a DIDU axle fault condition, method 100 implements closed-loop control of the vehicle's lateral dynamics using cooperative outputs from the vehicle ESC and powertrain actuators that are dynamically controlled to correct yaw rate deviations from a desired yaw rate. For smaller magnitude deviations, propulsion actuator control may have sufficient authority to counteract the undesired yaw deviation; therefore, ESC system assistance may be reduced or suspended. For severe mismatches between desired lateral motion and actual vehicle lateral motion, ESC system assistance is enabled to provide controller-automated friction brake activation at each corner of the vehicle. As yet another option, ADAS-enabled steering automation may be employed, which may include driver override to ensure reasonable steering input and control during yaw rate recovery. Two specific but non-limiting examples of DIDU axle fault management and mitigation in accordance with at least some of the disclosed concepts are provided in the following paragraphs.

[0108] In one example, an inverter open circuit fault may result in an uncontrolled charge generation fault condition. If the traction motor on a DIDU axle fails in this manner while the vehicle is traveling at high speed (e.g., >50mph), the failed motor may generate significant drag torque (e.g., -100Nm) at the affected corner, which may cause unrequested yaw of the vehicle toward the corner. In this case, the minimum and maximum motor torque limits of the failed motor are set to the estimated maximum / minimum UCG torque produced by the motor to allow the VMC to predict the vehicle motion that will be caused by the fault condition. The yaw rate control within the VMC may adjust the torque at the opposite axle to prevent undesired yaw. If the DU failure occurs at high speed, the torque limit on the motor of the non-faulty DU on the opposite half axle may not change, allowing the VMC to use the DU to help stabilize the vehicle. Once the vehicle's speed is forced to decrease due to the imposed vehicle speed limit, the non-faulty DU on the opposite half axle may be turned off to disable the entire DIDU axle. At the same time, the VMC calibration priority may change to emphasize lateral stability rather than satisfying the driver's longitudinal acceleration. A maximum vehicle speed limit may be imposed to reduce the vehicle speed to a speed where the UCG torque is considered negligible and prevent the vehicle from climbing back into the high UCG torque region. If the current driving mode allows the driver to deactivate ESC, a prompt is requested to re-enable the ESC system.

[0109] In another example, when the subject vehicle is operating in an off-road "terrain mode", one of the half-axles on the DIDU axle may be broken or otherwise disabled. In this case, the fault management and mitigation scheme may attempt to maximize the torque usage on the available axle / semi-axle to prevent the subject vehicle from being disabled. The faulty DU with the broken axle half-axle may be turned off, and its corresponding maximum / minimum torque capacity may be set to zero. If the current driving mode requires multi-axle torque output (e.g., off-road mode, high traction, etc.), the axle torque limit for the relative "good" axle / semi-axle may be increased (ramp out) according to the vehicle speed and driving mode. For example, at low vehicle speeds, the non-faulty DU on the relative half-axle may be given full torque capacity to ensure that the vehicle can move forward across rough or low μ surfaces as needed. At high vehicle speeds, the torque limit on the relative "good" half-axle may be set to zero to prevent imbalance in left-right movement. As another option, the VMC calibration priority may be changed to reduce the priority of lateral movement at low vehicle speeds (e.g., < 5 mph). In this case, additional vehicle speed limiting may not be required because there is no UCG issue (e.g., the selected driving mode may have a self-imposed speed limit constraint). In addition, ESC may be activated simultaneously to assist in lateral motion control.

[0110] In some embodiments, various aspects of the present disclosure may be implemented by a computer executable instruction program such as a program module, which is generally referred to as a software application or application program, which is executed by any controller or controller variant described herein. In a non-limiting example, the software may include routines, programs, objects, components, and data structures that perform specific tasks or implement specific data types. The software may form an interface to allow the computer to react based on an input source. The software may also collaborate with other code segments to initiate a variety of tasks in response to data received from a source in conjunction with the received data. The software may be stored on any of a variety of storage media, such as a CD-ROM, a disk, and a semiconductor memory (e.g., various types of RAM or ROM).

[0111] In addition, aspects of the present disclosure can be practiced with a variety of computer systems and computer network configurations, including multiprocessor systems, microprocessor-based or consumer programmable electronic devices, minicomputers, mainframe computers, etc. In addition, aspects of the present disclosure can be practiced in a distributed computing environment, where tasks are performed by means of resident and remote processing devices linked through a communication network. In a distributed computing environment, program modules can be located in both local and remote computer storage media including memory storage devices. Therefore, aspects of the present disclosure can be implemented in a computer system or other processing system in combination with various hardware, software, or a combination thereof.

[0112] Any method described herein may include machine-readable instructions for execution by: (a) a processor; (b) a controller; and / or (c) any other suitable processing device. Any algorithm, software, control logic, scheme, or method disclosed herein may be implemented as software stored on a tangible medium, such as flash memory, solid-state memory, hard drive, CD-ROM, digital versatile disk (DVD), or other storage device. The entire algorithm, control logic, scheme, or method and / or portions thereof may alternatively be executed by a device other than a controller and / or implemented in firmware or dedicated hardware in a usable manner (e.g., implemented by an application-specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable logic device (FPLD), discrete logic, etc.). In addition, although specific algorithms are described with reference to the flowcharts depicted herein, many other methods for implementing exemplary machine-readable instructions may be used alternatively.

[0113] Various aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; however, those skilled in the art will recognize that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise configurations and compositions disclosed herein; any and all modifications, changes and variations apparent from the foregoing description are within the scope of the present disclosure as defined by the appended claims. Moreover, the present concept expressly includes any and all combinations and sub-combinations of the foregoing elements and features.

Claims

1. A method of operating a motor vehicle having a dual independent drive unit (DIDU) axle, the DIDU axle comprising a first drive unit (DU) and a second drive unit, each of which is independently operable to independently drive a first wheel and a second wheel, respectively, the method comprising: receiving, by a vehicle controller, a fault signal from a fault sensing module indicating a fault condition in the first drive unit of the dual independent drive unit axle; determining, by the vehicle controller, a fault type of the fault condition; determining, by the vehicle controller, a current vehicle speed of the motor vehicle; determining, by the vehicle controller, a first torque limit for the first drive unit and a second torque limit for the second drive unit based on the fault type and the current vehicle speed; commanding, via the vehicle controller, a first torque output of the first drive unit to be constrained to the first torque limit, and a second torque output of the second drive unit to be constrained to the second torque limit; determining whether the current vehicle speed of the motor vehicle exceeds a predetermined yaw instability speed at which active lateral dynamics control is enabled; and In response to the current vehicle speed exceeding the predetermined yaw instability speed, the second torque limit constraining the second drive unit is removed.

2. The method according to claim 1, wherein: Determining the first torque limit of the first drive unit of the dual independent drive unit axle operating under the fault condition includes: determining whether the fault type is any one of a plurality of predetermined hardware or communication (HW / comms) faults; In response to the fault type not being one of the predetermined hardware / communication faults, setting the first torque limit to zero or near zero; and In response to the fault type being one of the predetermined hardware / communication faults, the first torque limit is set to an estimated achievable torque value corresponding to the fault type.

3. The method of claim 1 further comprising limiting a maximum vehicle speed limit of the motor vehicle to a base motor speed of an electric traction motor in the first drive unit while constraining the first and second torque outputs of the first and second drive units.

4. The method of claim 3, further comprising, while limiting the maximum vehicle speed limit to the base motor speed and constraining the first and second torque outputs of the first and second drive units: activating an electronic stability control (ESC) system of the motor vehicle; and A set of predetermined vehicle dynamics parameters are controlled by the electronic stability control system to mitigate or prevent severe instability conditions during driving of the motor vehicle.

5. The method according to claim 1, wherein: The vehicle includes a drive axle different from the dual independent drive unit axle that is independently driven by a prime mover different from the first drive unit and the second drive unit, and the method also includes confirming that the fault condition is a hardware or communication failure in the first drive unit of the dual independent drive unit axle, rather than a detected fault associated with the drive axle.

6. The method of claim 1 , further comprising, in response to the current vehicle speed not exceeding the predetermined yaw instability speed: determining whether a current driving mode of the motor vehicle is any one of a plurality of predetermined driving modes that enable multi-axle driving capability of the motor vehicle; and In response to the current driving mode of the motor vehicle not being one of the predetermined driving modes, the second drive unit is disabled.

7. The method of claim 6, further comprising, in response to the current driving mode of the motor vehicle being one of the predetermined driving modes: determining whether the current vehicle speed is less than a limp home mode maximum speed; disabling the second drive unit in response to the current vehicle speed being not less than the limp home mode maximum speed; as well as In response to the current vehicle speed being less than the limp home mode maximum speed, the second torque limit constraining the second drive unit is removed.

8. The method of claim 1 further comprising employing a propulsion actuator to manage lateral dynamic behavior of the motor vehicle in response to the current vehicle speed exceeding the predetermined yaw instability speed.

9. The method according to claim 8, wherein: Employing the propulsion actuator to manage the lateral dynamic behavior of the motor vehicle includes commanding the second drive unit to apply a negative torque to the second wheel via a corresponding axle shaft to cause yaw error compensation in response to a yaw error toward the first drive unit exceeding a first maximum yaw error value.

10. The method according to claim 8, wherein: Employing the propulsion actuator to manage the lateral dynamic behavior of the motor vehicle includes commanding the second drive unit to apply a positive torque to the second wheel via a second axle shaft to cause yaw error compensation in response to a yaw error toward the second drive unit exceeding a second maximum yaw error value.

11. The method according to claim 1, wherein: The vehicle controller comprises a vehicle motion controller (VMC), wherein the fault sensing module comprises a motor control processor (MCP) in communication with an electronic sensing device, and wherein receiving the fault signal comprises: monitoring, by the electronic sensing device, a back electromotive force (EMF) induced by the first drive unit on a high voltage (HV) electrical bus connected to the first drive unit; detecting, by the motor control processor, a fault condition in response to the back electromotive force induced on the high voltage electrical bus exceeding a DC link voltage threshold; and In response to detecting the fault condition, the fault signal is sent by the motor control processor to the vehicle motion controller.

12. The method according to claim 11, wherein: The fault type is a hardware or communication (HW / comms) fault, which causes the first drive unit to operate in an uncontrolled generation (UCG) mode, during which the first drive unit uncontrollably generates electrical power, which is transmitted to the high-voltage traction battery pack through the high-voltage electrical bus.

13. An electric drive vehicle, comprising: a vehicle body having a first pair of wheels and a second pair of wheels; a dual independent drive unit (DIDU) axle mounted to the vehicle body and comprising: a first drive unit and a second drive unit (DU) operable individually to independently drive a first wheel and a second wheel of the first pair of wheels, respectively; and a first axle half-shaft and a second axle half-shaft drivingly connecting the first drive unit and the second drive unit to the first wheel and the second wheel, respectively; a drive axle mounted to the vehicle body at the front or rear of the dual independent drive unit axle and including a prime mover independently operable to drive the second pair of wheels; and A vehicle controller programmed to: receiving a fault signal from a fault sensing module indicative of a fault condition in a first drive unit of a dual independent drive unit axle; determining a fault type of the fault condition; determining a current vehicle speed of the electrically driven vehicle; determining a first torque limit for the first drive unit and a second torque limit for the second drive unit based on the fault type and the current vehicle speed; constraining a first torque output of the first drive unit to the first torque limit, and constraining a second torque output of the second drive unit to the second torque limit; determining whether the current vehicle speed of the electrically driven vehicle exceeds a predetermined yaw instability speed for enabling active lateral dynamics control; and In response to the current vehicle speed exceeding the predetermined yaw instability speed, the second torque limit constraining the second drive unit is removed.

14. The electrically driven vehicle according to claim 13, wherein: The vehicle controller determining the first torque limit of the first drive unit of the dual independent drive unit axle operating under the fault condition includes: determining whether the fault type is any one of a plurality of predetermined hardware or communications (HW / comms) faults; In response to the fault type not being one of the predetermined hardware / communication faults, setting the first torque limit to zero or near zero; and In response to the fault type being one of the predetermined hardware / communication faults, the first torque limit is set to an estimated achievable torque value corresponding to the fault type.

15. The electrically driven vehicle according to claim 13, wherein: The vehicle controller is further programmed to limit a maximum vehicle speed of the electrically driven vehicle to a base motor speed of an electric traction motor in the first drive unit while constraining the first and second torque outputs of the first and second drive units.

16. The electrically driven vehicle according to claim 15, wherein: The vehicle controller is further programmed to, while limiting the maximum vehicle speed limit to the base motor speed and constraining the first and second torque outputs of the first and second drive units: activating an electronic stability control (ESC) system of the vehicle; as well as A set of predetermined vehicle dynamics parameters are controlled by the electronic stability control system to mitigate or prevent severe instability conditions during driving of the electrically driven vehicle.

17. The electrically driven vehicle according to claim 13, wherein: The vehicle controller is further programmed to, in response to the current vehicle speed not exceeding the predetermined yaw instability speed: determining whether a current driving mode of the vehicle is any one of a plurality of predetermined driving modes that enable multi-axle driving capability of the vehicle; as well as In response to the current driving mode of the electrically driven vehicle not being one of the predetermined driving modes, the second drive unit is disabled.

18. The electrically driven vehicle according to claim 17, wherein: The vehicle controller is further programmed to, in response to the current driving mode of the electrically driven vehicle being one of the predetermined driving modes: determining whether the current vehicle speed is less than a limp home mode maximum speed; disabling the second drive unit in response to the current vehicle speed being not less than the limp home mode maximum speed; as well as In response to the current vehicle speed being less than the limp home mode maximum speed, the second torque limit constraining the second drive unit is removed.

Images