Vehicle and method for controlling a multimode powertrain for a vehicle

Abstract

Vehicle (100), exhibiting: first and second drive units (20, 30) which are electrically connected to a high-voltage direct current source (10) via a high-voltage bus (12); wherein the first drive unit (20) comprises a first inverter (24) and a first electric machine (22) coupled to a first drive train (25), the first drive train (25) being arranged to transmit a torque to a front wheel (16, 17) of the vehicle (100); wherein the second drive unit (30) comprises a second inverter (34) and a second electric machine (32) coupled to a second drive train (35), the second drive train (35) being arranged to transmit torque to a rear wheel (18, 19) of the vehicle (100); and wherein the high-voltage bus (12) is electrically connected to the first and second inverters (24, 34); and a control unit (14) arranged to monitor the high-voltage bus (12) and which communicates with and is operationally connected to the first and second inverters (24, 34), wherein the control unit (14) contains a set of commands that is executable to: to detect the operation of one of the first inverters (24) or the second inverter (34) in an uncontrolled generation (UCG) operating mode, to determine a drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode, a balancing torque required to counteract the drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode, and to control the other of the first inverter (24) or the second inverter (34) based on the balancing torque.

Description

[0001] This description refers to electrified powertrain systems and their associated control systems.

[0002] Electric machines, such as multiphase electric motors / generators, have stator windings that are fed with alternating current from inverter modules, which are electrically connected to high-voltage direct current buses. Electric machines can be used as torque motors to provide drive torque for a vehicle's powertrain. Design and operational considerations associated with the use of electric machines as torque motors in vehicle systems include energy consumption, responsiveness, and drivability.

[0003] Certain electric machines, including inverter-controlled permanent magnet motors, can operate in an uncontrolled generating mode (UCG), in which an induced electromotive force (EMF) exceeds the DC link voltage present on a high-voltage bus. Such operating conditions can cause the electric machine to generate uncontrolled electrical power under certain operating conditions, which is transferred to a high-voltage battery via the high-voltage bus. This operating condition can increase the likelihood of lithium plating on the high-voltage battery. It can also increase the likelihood of unintended vehicle deceleration if the electric machine is configured to provide drive torque as part of a vehicle powertrain.Furthermore, in certain vehicles that use multiple electric machines as torque motors for vehicle propulsion, a fault in at least one of the electric machines can lead to unintended lateral movement (ULM) of the vehicle.

[0004] DE 10 2013 216 756 A1 describes a hybrid-electric vehicle method for controlling a hybrid-electric vehicle. The vehicle contains a traction battery, at least two electric machines, and a control unit. The control unit is configured to, in response to a fault condition in one of the electric machines during driving time, instruct the other electric machine to operate in a mode in which the torque output is limited to a threshold value dependent on a battery voltage, so that the vehicle drive is maintained during driving time.

[0005] The task can be considered to be to specify an improved vehicle and an improved method for controlling a multimode powertrain system for a vehicle.

[0006] A vehicle according to the invention, comprising a multimode drivetrain system, is described and includes a high-voltage direct current source connected to a high-voltage bus. The multimode drivetrain system comprises a first drive unit with a first inverter coupled to a first electric machine arranged to drive a first wheel connected to a first axle, and a second drive unit with a second inverter coupled to a second electric machine arranged to drive a second wheel connected to a second axle. A high-voltage bus is connected to the first and second inverters. A control unit is arranged to monitor the high-voltage bus and to communicate and be operationally connected to the first and second inverters.The control unit contains a set of commands that can be executed to detect the operation of the first or second inverter in an uncontrolled generation (UCG) mode, to determine a drive torque associated with the operation of the first or second inverter in UCG mode, and to determine a balancing torque required to counteract the drive torque associated with the operation of the first or second inverter in UCG mode. The other inverter of the first or second inverter is controlled based on the balancing torque.

[0007] In one embodiment, executing the instruction set to monitor a first electrical power output from the first inverter and to monitor a second electrical power output from the second inverter involves detecting the operation of the first inverter in UCG mode when a first electrical power output from the first inverter is greater than a first threshold, and detecting the operation of the second inverter in UCG mode when a second electrical power output from the second inverter is greater than a second threshold.

[0008] In one embodiment, executing the instruction set to monitor the first output voltage of the first inverter and to detect the operation of the first inverter in UCG mode when the first output voltage of the first inverter is greater than a first threshold voltage includes determining a first threshold voltage based on the DC power source.

[0009] In one embodiment, executing the instruction set to monitor a first output current of the first inverter and to detect the operation of the first inverter in UCG mode when the first output current of the first inverter is greater than a first threshold voltage involves determining the first threshold current based on the DC source.

[0010] In one embodiment, executing the command set to control the other of the first inverter or the second inverter involves canceling the drive train torque generated by the operation of the first inverter or the second inverter in UCG mode.

[0011] In one embodiment, executing the instruction set to control the other of the first inverter or the second inverter involves controlling a net DC current on the high-voltage DC bus within a permissible limit, and preventing an overvoltage or overcurrent condition at the high-voltage DC source.

[0012] In one embodiment, executing the command set involves disabling the operation of the first and second inverters in a regenerative braking mode.

[0013] A method according to the invention for controlling a multi-mode drivetrain system for a vehicle is described. The method comprises arranging the multi-mode drivetrain system to include a first drive unit with a first inverter coupled to a first electric machine coupled to a first drivetrain, wherein the first drivetrain is arranged to transmit torque to a first wheel associated with a first axle of the vehicle, and a second drive unit with a second inverter coupled to a second electric machine coupled to a second drivetrain, wherein the second drivetrain is arranged to transmit torque to a second wheel associated with a second axle of the vehicle.The operation of the first or second inverter in an uncontrolled generation (UCG) mode is detected, and the drive torque associated with the operation of the first or second inverter in UCG mode is determined. A balancing torque required to counteract the drive torque associated with the operation of the first or second inverter in UCG mode is determined, and the other drive torque of the first or second inverter is controlled based on this balancing torque.

[0014] One embodiment includes a controller configured to monitor the first drive unit and the second drive unit to detect a fault in the first drive unit that could cause unintended lateral movement (ULM) in the vehicle. Upon detecting a ULM-related fault, the controller is able to monitor a first rotational speed associated with the first vehicle wheel and a second rotational speed associated with the second vehicle wheel and control the torque output from the second drive unit based on the first and second rotational speeds.

[0015] One embodiment includes the instruction set being executable to determine that the first rotational speed is greater than a first threshold and to control the torque output from the second drive unit to a torque of zero or near zero in response to the detection of the ULM-related fault in the vehicle.

[0016] One embodiment includes the instruction set being executable to control the torque output from the second drive unit so that it is equal to the torque output from the first drive unit when there is a difference between the first speed and the second speed greater than a threshold speed, in response to the detection of the ULM-associated fault in the first drive unit.

[0017] One embodiment includes the instruction set being executable to detect a fault in the second drive unit when the difference between the first speed and the second speed is less than a threshold speed, in response to the detection of the fault associated with ULM in the first drive unit.

[0018] One or more embodiments are now described by way of example with reference to the attached drawings, in which: Fig. Figure 1 schematically shows an embodiment of a vehicle with a multimode drivetrain system comprising a first drive unit arranged to transmit torque to the front wheels, a second drive unit arranged to transmit torque to a first rear wheel, and a third drive unit arranged to transmit torque to a second rear wheel of the vehicle. Fig.Figure 2 schematically shows an embodiment of a vehicle with a multimode drivetrain comprising a first drive unit arranged to transmit torque to a first front wheel, a second drive unit arranged to transmit torque to a second front wheel, a third drive unit arranged to transmit torque to a first rear wheel, and a fourth drive unit arranged to transmit torque to a second rear wheel of the vehicle. Fig. Figure 3 schematically shows an embodiment of a vehicle with a multi-mode drivetrain system comprising a first drive unit arranged to transmit torque to the front wheels of the vehicle and a second drive unit arranged to transmit torque to the rear wheels of the vehicle. Fig.Figure 4 schematically shows a method for controlling the operation of an embodiment of a vehicle with a multi-mode powertrain system, including the management of operation in an uncontrolled generating mode (UCG) and an unintentional lateral vehicle movement (ULM). Fig. Figure 5 graphically shows the permissible operating ranges of a single battery cell with respect to cell current (amperes) and cell voltage (V), including a threshold cell current and threshold cell voltage.

[0019] As used herein, the term “system” may refer to one or a combination of mechanical and electrical hardware, sensors, controllers, application-specific integrated circuits (ASICs), combinational logic circuits, software, firmware and / or other components arranged to provide the described functionality.

[0020] Referring to the drawings, in which identical reference numerals correspond to identical or similar components in the various figures, the Fig. 1, Fig. 2 and Fig.3. Schematic embodiments of an all-wheel drive (AWD) vehicle comprising an electrified multi-mode powertrain system arranged to simultaneously transmit drive torque to a plurality of drive wheels, which employ electrified drive units (hereinafter referred to as "drive units") using electric machines as drive motors. The vehicle may, but is not limited to, a mobile platform in the form of a commercial vehicle, industrial vehicle, agricultural vehicle, passenger car, aircraft, watercraft, train, off-road vehicle, personal mobility device, robot, and the like, to fulfill the purposes of this description.The drive wheels shown are non-limiting examples and include a first, front axle 11 connected to a first, left-front (LF) wheel 16 and a second, right-front (RF) wheel 17; and a second, rear axle 13 connected to a third, left-rear (LR) wheel 18 and a fourth, right-rear (RR) wheel 19. Furthermore, a high-voltage DC power source 10 is coupled to the first, second, and third drive units 20, 30, 40 via a high-voltage bus 12. In one embodiment, the high-voltage DC power source 10 is configured as a multi-cell lithium-ion device that can be charged and discharged under various conditions. The illustrated embodiments of multi-mode drive systems are shown for illustrative purposes.The concepts described here can be applied to various configurations of multimode powertrain systems, including multiple drive units capable of AWD operation to transfer drive torque simultaneously to one or more front wheels and one or more rear wheels.

[0021] In Fig.Figure 1 is a schematic representation of an all-wheel-drive vehicle 100, comprising an embodiment of a multimode drivetrain system 15. The multimode drivetrain system 15 comprises a first drive unit 20, a second drive unit 30, and a third drive unit 40. A control unit 14 is arranged to control the operation of the multimode drivetrain system 15. The operation of this embodiment of the AWD vehicle 100 with the multimode drivetrain system 15 is controlled by a routine 400 for attenuating uncontrolled generation (UCG), which is executed in the control unit 14 and is referenced to Fig.4 is described in order to mitigate the effects of UCG and unintentional lateral movement (ULM) on the multimode propulsion system 15 and the high-voltage DC power source 10, which may be caused by the operation of the multimode propulsion system 15 as a result of a fault in the multimode propulsion system 15.

[0022] The first drive unit 20 comprises a first electric machine 22, which is coupled to the LF wheel 16 and the RF wheel 17 via a first drive train 25, which in one embodiment includes a transaxle 26 and half-shafts 27. A first inverter 24 is coupled to the first electric machine 22 and electrically connected to the high-voltage DC source 10 via the high-voltage bus 12. The control unit 14 controls the operation of the first drive unit 20 by controlling the first inverter 24. The friction brakes 28 and 29 are arranged such that they controllably decelerate the LF wheel 16 and the RF wheel 17, respectively, in response to a braking command.

[0023] The second drive unit 30 comprises a second electric machine 32, which is coupled to the LR wheel 18 via a second drive train 35, which in one embodiment includes a differential 36 and a half-shaft 37. A second inverter 34 is coupled to the second electric machine 32 and electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12. The control unit 14 controls the operation of the second drive unit 30 by controlling the second inverter 34. The friction brake 38 is arranged such that it decelerates the LR wheel 18 in a controllable manner in response to a braking command.

[0024] The third drive unit 40 comprises a third electric machine 42, which is coupled to the RR wheel 19 via a third drive train 45, which in one embodiment includes a differential 46 and a half-shaft 47. A third inverter 44 is coupled to the third electric machine 42 and electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12. The control unit 14 controls the operation of the third drive unit 40 by controlling the third inverter 44. The friction brake 39 is arranged such that it decelerates the RR wheel 19 in a controllable manner in response to a braking command.

[0025] Fig.Figure 2 schematically shows an embodiment of an AWD vehicle 200, which includes a further embodiment of a multimode drivetrain system 215 arranged to transmit the drive torque simultaneously to a plurality of drive wheels. A control unit 214 is arranged to control the operation of the multimode drivetrain system 215. The multimode drivetrain system 215 comprises a first drive unit 220, a second drive unit 230, a third drive unit 240, and a fourth drive unit 250. The high-voltage DC power source 10 is coupled to the first, second, third, and fourth drive units 220, 230, 240, and 250 via the high-voltage bus 12. The control unit 214 is arranged to control the operation of the multimode drivetrain system 215.The operation of this embodiment of the AWD vehicle 200 including the multimode powertrain system 215 is controlled via the UCG mode reduction routine 400, which is executed in the control unit 214 and with reference to . Fig.As described in Section 4, the first drive unit 220 is designed to mitigate the effects of unintended lateral movement (ULM) and unintended sideways movement (UCG) on the multimode drive system 215 and the high-voltage DC power source 10, which can be caused by the operation of the multimode drive system 215 as a result of a fault in the multimode drive system 215. The first drive unit 220 comprises a first electric machine 222, which is coupled to the LF wheel 16 via a first drive train 225, which in one embodiment comprises a transaxle 226 and a half-shaft 227. A first inverter 224 is coupled to the first electric machine 222 and electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12. The control unit 214 controls the operation of the first drive unit 220 by controlling the first inverter 224. The friction brake 28 is arranged so that it brakes the LF wheel 16 in a controllable manner in response to a braking command.

[0026] The second drive unit 230 comprises a second electric machine 232, which is coupled to the RF wheel 17 via a second drive train 235, which in one embodiment includes a transaxle 236 and a half-shaft 237. A second inverter 234 is coupled to the second electric machine 232 and electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12. The control unit 214 controls the operation of the second drive unit 230 by controlling the second inverter 234. The friction brake 29 is arranged such that it decelerates the RF wheel 17 in a controllable manner in response to a braking command.

[0027] The third drive unit 240 comprises a third electric machine 242, which is coupled to the LR wheel 18 via a third drive train 245, which in one embodiment includes a transaxle 246 and a half-shaft 247. A third inverter 244 is coupled to the third electric machine 242 and electrically connected to the high-voltage DC source 10 via the high-voltage bus 12. The control unit 214 controls the operation of the third drive unit 240 by controlling the third inverter 244. The friction brake 38 is arranged such that it decelerates the LR wheel 18 in a controllable manner in response to a braking command.

[0028] The fourth drive unit 250 comprises a fourth electric machine 252, which is coupled to the RR wheel 19 via a fourth drive train 255, which in one embodiment includes a transaxle 256 and a half-shaft 257. A fourth inverter 254 is coupled to the fourth electric machine 252 and electrically connected to the high-voltage DC source 10 via the high-voltage bus 12. The control unit 214 controls the operation of the fourth drive unit 250 by controlling the fourth inverter 254. The friction brake 39 is arranged such that it decelerates the RR wheel 19 in a controllable manner in response to a braking command.

[0029] Fig.Figure 1 schematically shows an embodiment of an AWD vehicle 300, which includes a further embodiment of a multimode drivetrain system 315 arranged to transmit the drive torque simultaneously to a plurality of drive wheels. A control unit 314 is arranged to control the operation of the multimode drivetrain system 315. The multimode drivetrain system 315 comprises a first drive unit 320 and a second drive unit 330. The high-voltage DC power source 10 is coupled to the first and second drive units 320 and 330 via the high-voltage bus 12. The control unit 314 is arranged to control the operation of the multimode drivetrain system 315. The operation of one aspect of this embodiment of the AWD vehicle 300, including the multimode powertrain system 315, is controlled via the UCG mode reduction routine 400, which is executed in the control unit 314 and with reference to Fig.4 is described to mitigate the effects of UCG and unintentional lateral movement (ULM) on the multimode propulsion system 315 and the high-voltage DC power source 10 that may be caused by the operation of the multimode propulsion system 315 as a result of a fault in the multimode propulsion system 315.

[0030] The first drive unit 320 comprises a first electric machine 322, which is coupled to the LF wheel 16 and the RF wheel 17 via a first drive train 325, which in one embodiment includes a transaxle 326 and half-shafts 327. A first inverter 324 is coupled to the first electric machine 322 and electrically connected to the high-voltage DC source 10 via the high-voltage bus 12. The control unit 314 controls the operation of the first drive unit 320 by controlling the first inverter 324. The friction brake 28 is arranged to controllably decelerate the LF wheel 16, and the friction brake 29 is arranged to controllably decelerate the RF wheel 17 in response to a braking command.

[0031] The second drive unit 330 comprises a second electric machine 332, which is coupled to the LR wheel 18 and the RR wheel 19 via a second drive train 335, which in one embodiment includes a differential 336 and half-shafts 337. A second inverter 334 is coupled to the second electric machine 332 and electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12. The control unit 314 controls the operation of the second drive unit 330 by controlling the second inverter 334. The friction brakes 38 and 39 are arranged such that they controllably decelerate the LR wheel 18 and the RR wheel 19 in response to a braking command.

[0032] Each of the aforementioned electrical machines, which with regard to the Fig. 1, Fig. 2 and Fig.The electric motor / generator described in section 3 is designed as a multi-phase electric motor / generator, e.g., a multi-phase permanent magnet electric motor / generator, or alternatively as another type of electric motor / generator. Each electric machine comprises a stator and a rotor, the rotor being mechanically rotatably coupled to the associated drive train. Each electric machine is equipped with a speed sensor for monitoring the rotational speed, which may be a resolver or another speed monitoring device. Each of the aforementioned inverters is designed as a power inverter module, which is arranged to control the electrical power flow to the respective electric machine. The inverter module contains a multi-phase inverter circuit and an inverter control unit.The multiphase inverter circuit is electrically connected to the high-voltage DC power source 10 via the high-voltage bus 12, which comprises a positive bus element and a negative bus element. In one embodiment, the high-voltage DC power source 10 supplies a DC voltage close to 300 V. The high-voltage DC power source 10 may include a high-voltage energy storage device, such as a high-voltage battery or capacitor, a high-voltage current generator, or other related equipment or system. The multiphase inverter circuit of the inverter module comprises a plurality of switch pairs electrically connected in series across the elements of the high-voltage bus 12. Each switch in the switch pairs may be a power transistor, such as an insulated-gate bipolar transistor (IGBT), or another type of power transistor.Each pair of switches corresponds to one phase of the respective electric machine. The multiphase inverter circuit preferably includes further electrical components, including capacitors, resistors, and other electrical circuit components, to perform functions related to electrical noise suppression, load balancing, and the like. High voltage, as used here, refers to nominal voltage levels primarily used in vehicle drive applications, e.g., for high-voltage electric machines.

[0033] Fig.Figure 4 schematically shows details of the UCG mode reduction routine 400 for controlling the operation of an embodiment of an AWD vehicle, e.g., one of the AWD vehicles 100, 200, or 300 described herein. The UCG mode reduction routine 400 is represented as a collection of blocks in a logical flowchart, which depicts a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the blocks represent computer instructions which, when executed by one or more processors, perform the aforementioned operations. For the sake of simplicity and clarity of presentation, the procedure is described with reference to the one in Fig. 1 depicted vehicle 100 described. Table 1 BLOCK BLOCK CONTENT 402 Monitoring electrical power on high-voltage buses 404 Fault detected? 406 How to detect a UCG event? 408 Did the UCG event occur in an electric machine mounted on a 2-motor axis? 410 Execute 3-phase opening state on non-faulty electrical machine 412 Determine the UCG torque 414 Determine the balancing torque for an electric machine that drives a different axis. 416 Can an electric machine driving a different axis generate a compensating torque? 417 Control of the electric machine to deliver a compensating torque; use of a friction brake 418 Disable regenerative braking; use friction braking to stop the vehicle. 420 Did the UCG fault occur on the dual-motor axle? 422 Monitor the rotational speeds of the two electric machines. 424 Monitor the temperatures of both electric machines. 426 Is the rotational speed of the electrical machine associated with the fault greater than a certain threshold value? 427 3-phase opening fault in electrical machine in conjunction with fault detection 428 The target torque output from the undisturbed electric machine is equal to the torque output from the electric machine connected to the fault (+ / -ΔT2) 430 Detection of a 3-phase short circuit in an electrical machine in conjunction with a fault 432 Is the speed of the delta motor greater than the second threshold? AND is the delta temperature greater than the third threshold? 433 Detecting a 3-phase short circuit in an otherwise undisturbed electrical machine 434 Set target torque output from the undisturbed electrical machine to zero (+ / - ΔT1) 435 End

[0034] The execution of the UCG mode mitigation routine 400 can proceed as follows. The steps of the UCG mode mitigation routine 400 can be executed in any suitable order and are not limited to those relating to Fig. The described sequence is limited. As used here, the term "1" indicates a positive answer or "YES", and the term "0" indicates a negative answer or "NO".

[0035] The UCG mode mitigation routine (hereinafter referred to as “routine”) 400 operates by monitoring the electrical power in the form of a voltage level and a current level on the high-voltage bus 12 and at each of the inverter modules, with the intention of detecting a fault associated with any of the electrical machines, including a fault that may result in a UCG event (402), (404).

[0036] If no fault is detected in connection with any of the electrical machines (404)(0), this iteration of routine 400 ends (435).

[0037] When a fault associated with one of the electrical machines is detected (404)(1), it is determined whether a UCG event has occurred (406). A UCG event can be detected if the electrical power to the battery cells of the high-voltage DC source 10 is greater than a threshold power. The electrical power to the cells includes a battery cell voltage and a battery cell current. The UCG event can be detected if the battery cell voltage is greater than a battery cell voltage threshold, and / or if the battery cell current is greater than a battery cell current threshold. Exemplary thresholds are given with reference to Fig.As illustrated, permanent magnet synchronous motors in indoor environments often operate in a flux-reduced state to achieve higher speeds. However, during this process, faults such as overcurrent and overvoltage can occur, causing the power transistors to immediately shut down. The battery packs are charged via a three-phase uncontrolled rectifier consisting of six flywheel diodes, resulting in operation in UCG mode.

[0038] Furthermore, a UCG event can occur during certain operating conditions, including high-speed, low-load, or no-load conditions, when the electric machine operates in such a way that the motor's back EMF increases, resulting in a motor output voltage that is higher than the voltage on the high-voltage bus. This excess output voltage can cause a charging current to flow through one or more of the diodes arranged in parallel with the inverter's switches. The charging current flow occurring during the UCG event can lead to an overcurrent through components of the respective inverter or to an overcharging of the high-voltage DC power source 10, which can negatively affect the service life of the respective inverter or the high-voltage DC power source 10.As a non-restrictive example, lithium ions can accumulate on the surface of an anode and be deposited as metallic lithium if the electric current exceeds a design limit, so that lithium ions cannot be accommodated quickly enough between the intercalation layers of the carbon anode, a process known as lithium plating.

[0039] If a UCG event is detected after a fault has been detected (406)(1), the routine determines whether the UCG event is associated with one of the drive units arranged in a configuration that includes two drive units, each separately providing drive torque to two opposite wheels of an axle (408). By way of example, this configuration includes the rear axle of vehicle 100 (shown with reference to Fig. 1) and the front and rear axles of vehicle 200 (shown with reference to Fig. 2).

[0040] If the configuration includes two drive units that provide drive torque to two wheels of an axle (408)(1), the routine commands the inverter connected to the other, non-faulty drive unit to enter an open, free-running state (410).

[0041] The routine estimates or otherwise determines a magnitude of the UCG drive torque, wherein the UCG drive torque is related to the magnitude of the torque generated by the respective drive unit as a result of operation in the UCG event (412). The routine determines a balancing torque (414), which is a magnitude of the torque that must be supplied by the non-faulty drive unit to counteract the UCG drive torque, and determines whether the non-faulty drive unit is capable of generating the balancing torque (416).If the fault-free drive unit is unable to generate the balancing torque (416)(0), the routine commands the fault-free drive unit to generate the maximum torque and commands the operation of the friction brakes to such a magnitude of braking torque that the UCG drivetrain torque is counteracted by the combination of the motor torque of the fault-free drive unit and the friction brakes (417). The balancing torque is commanded to operate one or both drive units assigned to the other axis, i.e., the axis not associated with the UCG event. The balancing torque commanded to operate one or both drive units assigned to the other axis, i.e.,The axis not associated with the UCG event serves to counteract the drive torque generated by the UCG event and controls the net DC current to maintain the DC voltage on the high-voltage bus within permissible limits, thereby preventing an overvoltage or overcurrent condition at the high-voltage DC source. The overvoltage and overcurrent conditions are those conditions that exceed the voltage and current design limits selected to minimize or prevent the risk of lithium plating in the high-voltage battery 10 in one embodiment. If the fault-free drive unit is able to generate the counter-torque (416)(1), the routine disables regenerative braking (418), and vehicle braking is generated exclusively by the friction brakes. Fig.This illustrates the operating conditions under which regenerative braking can be activated or deactivated, based on the electrical power delivered to the battery cells as a result of the UCG event. Under certain circumstances, this operation can continue until the vehicle speed reaches zero, i.e., forward motion stops, and vehicle operation ends.

[0042] Fig. The figure graphically illustrates the permissible operating ranges associated with a single battery cell in terms of cell current (amperes) 510 and cell voltage (volts) 520, including a threshold cell current 515 and a threshold cell voltage 525 associated with a UCG event. It is clear that the values ​​of the threshold cell current 515 and the threshold cell voltage 525 are temperature-dependent.

[0043] If the cell current and cell voltage values ​​associated with the UCG event are less than the respective threshold cell current value 515 and threshold cell voltage value 525, the balancing torque commanded to operate one or both drive units associated with the other axle, i.e., the axle not associated with the UCG event, can be applied, including operation in regenerative braking mode.

[0044] However, if the magnitude of the cell current and / or the magnitude of the cell voltage associated with the UCG event is greater than the respective value of the threshold cell current 515 and the value of the threshold cell voltage 525, the balancing torque commanded to operate one or both drive units associated with the other axle, i.e., the axle not associated with the UCG event, may be applied, including disabling operation in regenerative braking mode.

[0045] The UCG mode mitigation routine 400 serves to maintain the voltage and current on the high-voltage bus within their respective design limits during operation in UCG mode, and also to regulate any unintended delay rate to the level perceived as a run-off rate. This serves to eliminate or mitigate a UCG event, thus protecting the affected inverter(s) and DC power source without requiring hardware modifications or redesigns. Furthermore, and directly, the risk of lithium plating in the high-voltage DC power source 10 can be eliminated or reduced, which has a positive effect on the service life of the high-voltage DC power source 10.

[0046] If a UCG event is not detected (406)(0) after a fault associated with one of the electric machines of one of the drive units has been detected, routine 400 proceeds to evaluate whether the detected fault could lead to unintended lateral vehicle movement caused by the operation of the multimode powertrain system. If a three-phase short circuit or three-phase open fault occurs in one of the drive units of the multimode powertrain system, uncontrolled lateral torque generation may occur, which could lead to unintended lateral movement. Steps 420-434 relate to monitoring the multimode powertrain for fault occurrences and controlling the operation of the drive units of the multimode powertrain in response to mitigate and prevent unintended lateral vehicle movement.This involves monitoring various parameters associated with the multimode powertrain system for the presence or occurrence of a fault in one of the drive units (420), where such a fault has the potential to cause unintended lateral movement (ULM) in the vehicle as a result of the operation of the multimode powertrain system. Such faults are referred to below as ULM-inducing faults. ULM-inducing faults may include, as non-limiting examples, a short circuit or open circuit in one of the aforementioned inverters of one of the drive units, or a fault in the high-voltage bus.

[0047] When the occurrence of a ULM-inducing fault is detected (420)(1), the system identifies which of the electrical machines has experienced the ULM-inducing fault. The rotational speeds of the electrical machines are monitored and evaluated (422), as is the monitoring of the temperatures of the electrical machines (424). Monitoring of the rotational speeds of the electrical machines may include monitoring the rotational speeds of the electrical machines or monitoring the vehicle wheel speeds for the respective drive unit, or a combination thereof. Monitoring of the temperatures of the electrical machines may include monitoring the temperatures at relevant points of the electrical machines using thermocouples, thermistors, etc.

[0048] The rotational speed of one of the electrical machines that experienced the ULM-triggering fault is compared with a first threshold value (426).

[0049] If the rotational speed of one of the electrical machines in which the ULM-inducing fault has occurred is less than the first threshold (426)(0), this is an indication that the fault is a three-phase open fault in the electrical machine in which the ULM-inducing fault has occurred (427), and the control commands the torque output of the other drive unit, which includes the non-faulty electrical machine, to zero, with an allowable torque fault band error (+ / -ΔT2) (428), and this iteration ends (435).

[0050] If the rotational speed of one of the electrical machines that has experienced the ULM-inducing fault is equal to or greater than the first threshold (426)(1), this is an indication that there is a three-phase short circuit in the electrical machine that has experienced the ULM-inducing fault (430), and the control continues monitoring as follows.

[0051] The control system determines an absolute value of a speed difference between the speed of the electric machine at which the ULM-inducing fault occurred and the speed of the other, non-faulty electric machine. The control system also determines an absolute value of a temperature difference between the temperature of the electric machine at which the ULM-inducing fault occurred and the temperature of the other, non-faulty electric machine (432).

[0052] If the absolute value of the speed difference is greater than a second threshold speed and the absolute value of the temperature difference is greater than a threshold temperature (432)(1), the controller commands that the torque output of the other drive unit containing the non-faulty electric machine be equal to the torque output of the drive unit containing the electric machine in which the ULM-inducing fault occurred, with an allowable torque error band (+ / -ΔT1) (434). The allowable torque error band permits a certain degree of torque imbalance between the drive units but avoids the ULM state. This iteration is then terminated (435).

[0053] If the absolute value of the speed difference is less than the second threshold speed or the absolute value of the temperature difference is less than the threshold temperature (432)(0), the controller determines that there is a three-phase fault in the other, non-faulty electrical machine (433), and this iteration ends (435).

[0054] In this way, the control system is able to control the torque outputs of the electric machines of the drive units of the multimode powertrain system in such a way that an unintended lateral vehicle movement, which is caused by the operation of the multimode powertrain system as a result of a fault in one of the drive units of the multimode powertrain systems, as with reference to the Fig. 1, Fig. 2 and Fig.3. This is effective when the drive units of the respective multimode powertrain system are configured to transmit torque to vehicle wheels located on opposite sides of the vehicle, which are capable of inducing torque steer and / or unintended lateral vehicle movement.

[0055] The terms controller, control module, module, control, control unit, processor, and similar terms refer to one or more combinations of application-specific integrated circuits (ASICs), electronic circuits, central processing units (e.g., microprocessor(s)), and associated memory and storage devices (read-only, programmable read-only, random access, disk devices, etc.) that execute one or more software or firmware programs or routines, combinational logic circuits, input / output circuits and devices, signal conditioning and buffering circuits, and other components to provide a described functionality. Software, firmware, programs, instructions, control routines, code, algorithms, and similar terms refer to instruction sets executable by controllers, including calibrations and lookup tables.Each controller executes control routine(s) to provide the desired functions, including monitoring inputs from sensor devices and other networked controllers, and executing control and diagnostic routines to manage the operation of actuators. These routines can be executed at regular intervals, such as every 100 microseconds during operation. Communication between controllers, and between controllers, actuators, and / or sensors, can occur via a direct wired connection, a networked communication bus connection, a wireless connection, or another suitable communication link.

Claims

Vehicle (100) comprising: first and second drive units (20, 30) electrically connected to a high-voltage DC source (10) via a high-voltage bus (12); wherein the first drive unit (20) comprises a first inverter (24) and a first electric machine (22) coupled to a first drive train (25), the first drive train (25) being arranged to transmit torque to a front wheel (16, 17) of the vehicle (100); wherein the second drive unit (30) comprises a second inverter (34) and a second electric machine (32) coupled to a second drive train (35), the second drive train (35) being arranged to transmit torque to a rear wheel (18, 19) of the vehicle (100); and wherein the high-voltage bus (12) is electrically connected to the first and second inverters (24, 34);and a control unit (14) arranged to monitor the high-voltage bus (12), and which communicates with and is operationally connected to the first and second inverters (24, 34), the control unit (14) containing a set of commands executable to: detect the operation of one of the first inverters (24) or the second inverter (34) in an uncontrolled generation (UCG) mode, determine a drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode, determine a balancing torque required to counteract the drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode, and control the other of the first inverter (24) or the second inverter (34) based on the balancing torque. Vehicle (100) according to claim 1, wherein executing the instruction set to detect the operation of the first inverter (24) or the second inverter (34) in uncontrolled generation (UCG) mode comprises the instruction set being executable to: monitor a first electrical power output of the first inverter (24) and monitor a second electrical power output of the second inverter (34), detect operation of the first inverter (24) in UCG mode when a first electrical output power of the first inverter (24) is greater than a first threshold, and detect operation of the second inverter (34) in UCG mode when a second electrical output power of the second inverter (34) is greater than a second threshold. Vehicle (100) according to claim 2, wherein executing the instruction set to monitor a first electrical power output from the first inverter (24) and to detect the operation of the first inverter (24) in UCG mode when the first electrical power output from the first inverter (24) is greater than the first threshold, comprises that the instruction set is executable to monitor a first voltage output from the first inverter (24) and to detect the operation of the first inverter (24) in UCG mode when the first voltage output from the first inverter (24) is greater than a first threshold voltage, wherein the first threshold voltage is determined on the basis of a limit value associated with the high-voltage DC source (10). Vehicle (100) according to claim 2, wherein executing the instruction set to monitor the first electrical power output from the first inverter (24) and to detect the operation of the first inverter (24) in UCG mode when the first electrical power output from the first inverter (24) is greater than a first threshold, comprises that the instruction set is executable to monitor a first current output from the first inverter (24) and to detect the operation of the first inverter (24) in UCG mode when the first current output from the first inverter (24) is greater than a first threshold voltage, wherein a first threshold current is determined on the basis of a limit value associated with the high-voltage DC source (10). Vehicle (100) according to claim 1, wherein executing the command set to control the other of the first inverter (24) or the second inverter (34) based on the balancing torque comprises that the command set is executable to control the other of the first inverter (24) or the second inverter (34) to cancel the drive train torque generated by the operation of the first inverter (24) or the second inverter (34) in UCG mode. Vehicle (100) according to claim 5, wherein executing the command set to control the other of the first inverter (24) or the second inverter (34) to cancel the drive train torque generated by the operation of the first inverter (24) or the second inverter (34) in UCG mode comprises the command set being executable to control the other of the first inverter (24) or the second inverter (34) to control a net DC current on the high-voltage bus (12) within a permissible limit to prevent an overvoltage or overcurrent condition at the high-voltage DC source (10). Vehicle (100) according to claim 1, further comprising that the instruction set is executable to deactivate the operation of the first and second inverters (24, 34) in a regenerative braking mode. Method for controlling a multimode powertrain system (15) for a vehicle (100), comprising: arranging the multimode powertrain system (15) to include a first inverter (24) coupled to a first electric machine (22) coupled to a first powertrain (25), wherein the first powertrain (25) is arranged to transmit torque to a first wheel (16, 17) connected to a first axle (11) of the vehicle (100), and a second inverter (34) coupled to a second electric machine (32) coupled to a second powertrain (35), wherein the second powertrain (35) is arranged to transmit torque to a second wheel (18, 19) connected to a second axle (13) of the vehicle (100), and wherein the first and second electric machines (22, 32) are electrically connected to a high-voltage bus (12) are connected;Detecting the operation of the first inverter (24) or the second inverter (34) in an uncontrolled generation mode (UCG); determining a drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode; determining a balancing torque required to counteract the drive train torque associated with the operation of the first inverter (24) or the second inverter (34) in UCG mode; and controlling the respective other inverter (24, 34) based on the balancing torque. The method of claim 8, wherein detecting the operation of the first inverter (24) or the second inverter (34) in uncontrolled generation (UCG) mode comprises: monitoring a first electrical power output from the first inverter (24) and monitoring a second electrical power output from the second inverter (34); detecting the operation of the first inverter (24) in UCG mode when the first electrical output power of the first inverter (24) is greater than a first threshold; and detecting the operation of the second inverter (34) in UCG mode when the second electrical output power of the second inverter (34) is greater than a second threshold. The method of claim 9, wherein monitoring a first electrical output power of the first inverter (24) and detecting the operation of the first inverter (24) in UCG mode when the first electrical output power of the first inverter (24) is greater than a first threshold value, comprises monitoring a first output voltage of the first inverter (24) and detecting the operation of the first inverter (24) in UCG mode when the first output voltage of the first inverter (24) is greater than a first threshold voltage, wherein the first threshold voltage is determined on the basis of a limit value associated with the high-voltage bus (12).

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