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EP-3758991-B1 - BEV TORQUE SPLIT CONTROL

EP3758991B1EP 3758991 B1EP3758991 B1EP 3758991B1EP-3758991-B1

Inventors

  • HANCOCK, MATTHEW
  • COPP, David
  • ADCOCK, Lee
  • PLIANOS, Alex

Dates

Publication Date
20260506
Application Date
20190116

Claims (12)

  1. A controller (2) for a vehicle (1) with a front and rear axle (3, 4) each axle being provided with at least two wheels and at least first and second propulsion units (5, 6), the controller (2) for controlling the at least first and second propulsion units (5, 6) to generate a combined torque with reference to a total requested torque, the controller (2) comprising: means to receive one or more traction signals indicating available traction at at least one wheel; means to determine a traction torque range defined by a maximum and minimum torque for at least one of the at least first or second propulsion units (5, 6) in dependence on one or more of the traction signals; means to determine a proposed distribution of torque between each of the at least first and second propulsion units (5, 6) with reference to the total requested torque in dependence on an efficiency of operation of each of the at least first and second propulsion units (5, 6); means to determine a proposed torque to be generated by each of the at least first and second propulsion units (5, 6) in dependence on the proposed distribution of torque; means to compare the traction torque range determined for each propulsion unit for which a traction torque range has been determined and the proposed torque for that propulsion unit; means to generate at least one torque control signal for controlling at least one of the at least first and second propulsion units (5, 6); wherein the torque control signal is a signal to the propulsion unit to generate the proposed torque for that propulsion unit if the proposed torque for that propulsion unit is within the traction torque range for that propulsion unit; and the torque control signal is a signal to the propulsion unit to generate a torque with a value approximately equal to whichever of the maximum or minimum torques for that propulsion unit is closest to the proposed torque if the proposed torque for that propulsion unit is not within the traction torque range for that propulsion unit.
  2. A controller (2) according to claim 1, in which the controller (2) comprises: means to receive at least one vehicle dynamics signal relating to one or more of the handling of the vehicle (1), the steering feel of the vehicle (1) and or the environment around the vehicle (1); the traction torque range for at least one of the at least first or second propulsion units (5, 6) is determined in dependence on at least one of the traction signals and at least one of the vehicle dynamics signals, optionally wherein the at least one of the traction signals has greater influence in the determination of the traction torque range than the at least one of the vehicle dynamics signals.
  3. A controller (2) according to any of claims 1 to 2, in which the controller (2) comprises: means to receive at least one NVH signal relating to one or more of the noise vibration and or harshness characteristics of the vehicle (1); the traction torque range for at least one of the at least first or second propulsion units (5, 6) is determined in dependence on at least one of the traction signals and at least one of the NVH signals, optionally wherein the at least one of the traction signals has greater influence in the determination of the traction torque range than the at least one of the vehicle dynamics signals when present, the at least one of the traction signals has greater influence in the determination of the traction torque range than the at least one of the NVH signals, and the at least one of the vehicle dynamics signals when present has greater influence in the determination of the traction torque range than the at least one of the NVH signals.
  4. A controller (2) according to any of claims 1 to 3, in which the means to determine a proposed distribution of torque between each of the at least first and second propulsion units (5, 6) with reference to the total requested torque comprises: means to determine a proposed distribution of torque between each of the at least first and second propulsion units (5, 6) with reference to the total requested torque comprises means to determine a total power cost in dependence on an estimated power loss of the at least first and second propulsion units (5, 6) within said at least first and second torque ranges, means to identify a minimum value of the determined total power cost, and means to determine the torque to be generated by each of said at least first and second propulsion units (5, 6), in which the means to determine the torque to be generated by each of said at least first and second propulsion units (5, 6) determines the torques to correspond to the identified minimum value of the total power cost.
  5. A controller (2) according to claim 4, in which the controller (2) is configured to determine at least first and second power loss penalties in dependence on current operating parameters of the at least first and second propulsion units (5, 6).
  6. A controller (2) according to claim 5, in which the at least first and second propulsion units (5, 6) each comprise an electric machine (7, 10), the controller (2) being configured to determine the at least first and second power loss penalties in dependence on an operating temperature of the associated electric machine, optionally wherein the controller (2) is configured to determine when the operating temperature of each electric machine (7, 10) increases above one or more predetermined temperature thresholds.
  7. A controller (2) according to claim 5 or claim 6, in which the total power cost is determined in dependence on the estimated power loss and the power loss penalties of each of said at least first and second propulsion units (5, 6).
  8. A controller (2) according to any of claims 4 to 7, in which the power loss of each of the at least first and second propulsion units (5, 6) is estimated in dependence on one or more of the following set: an operating temperature; an operating speed; and a motor torque.
  9. A controller (2) according to any of claims 4 to 8, in which the controller (2) is configured to estimate the power loss of each of the at least first and second propulsion units (5, 6) at a plurality of intervals within the determined first and second torque ranges.
  10. A vehicle (1) comprising a controller (2) according to any of claims 1 to 9.
  11. A method for controlling at least first and second propulsion units (5, 6) of a vehicle (1) with a front and rear axle (3, 4) each axle being provided with at least two wheels, at least first and second control units being suitable to generate a combined torque with reference to a total requested torque, the method comprising: receiving at least one traction signal indicating available traction at at least one wheel; determining a traction torque range defined by a maximum and minimum torque for at least one of the at least first or second propulsion units (5, 6) in dependence on at least one of the traction signals; determining a proposed distribution of torque between each of the at least first and second propulsion units (5, 6) with reference to the total requested torque in dependence on an efficiency of operation of each of the at least first and second propulsion units (5, 6); determining a proposed torque to be generated by each of the at least first and second propulsion units (5, 6) in dependence on the proposed distribution of torque; comparing the traction torque range determined for each propulsion unit for which a traction torque range has been determined and the proposed torque for that propulsion unit; generating at least one torque control signal for controlling at least one of the at least first and second propulsion units (5, 6); wherein the torque control signal is a signal to the propulsion unit to generate the proposed torque for that propulsion unit if the proposed torque for that propulsion unit is within the traction torque range for that propulsion unit; and the torque control signal is a signal to the propulsion unit to generate a torque with a value approximately equal to whichever of the maximum or minimum torques for that propulsion unit is closest to the proposed torque if the proposed torque for that propulsion unit is not within the traction torque range for that propulsion unit.
  12. A computer program that, when run on at least one electronic processor, performs the method according to claim 11.

Description

TECHNICAL FIELD The present disclosure relates to a battery electric vehicle (BEV) torque split control. In particular, but not exclusively it relates to a BEV torque split control in a vehicle for controlling the torque split between propulsion units. Aspects of the invention relate to a controller for controlling at least first and second propulsion units, to a vehicle comprising a controller, to methods of controlling at least first and second propulsion units, and to a non-transitory computer-readable medium. BACKGROUND It is known to provide a battery electric vehicle (BEV) with at least one propulsion unit per axle for transmitting torque to at least one wheel per axle. By way of example, the vehicle may comprise a first propulsion unit for transmitting torque to a front axle; and a second propulsion unit for transmitting torque to a rear axle. This configuration offers various advantages in terms of performance, stability/traction, increased regenerative capacity during braking and overall efficiency. Determination of the torque distribution between the two axles is a non-trivial task that has to consider often conflicting attributes and constraints. It is an aim of the present invention to provide efficient control of a vehicle drivetrain whilst meeting required vehicle dynamics attributes. EP2223821A2 relates to a control system for an all-wheel drive electric vehicle. US6958587B1 relates to optimal torque distribution among multiple propulsion systems in accordance with various constraints. GB2544764A relates to a controller for a motor vehicle powertrain, the controller being configured to control the amount of torque generated by each of a plurality of drive torque sources. SUMMARY OF THE INVENTION Aspects of the invention are set out in the appended claims. According to an aspect of the invention there is provided a controller for a vehicle according to claim 1. Optionally, the one or more traction signals indicate at least one vehicle operating condition. The at least one vehicle operating condition may be one or more of vehicle speed, wheel speeds, longitudinal acceleration, lateral acceleration, estimated coefficient of friction (µ) of the surface over which the vehicle is traveling, or other conditions that have an effect on the traction available to a moving vehicle. This provides the advantage that the controller can: determine a maximum and minimum torque that can be applied to each axle or wheel without loss of traction with reference to the signals received by the controller that are indicative of at least one vehicle operating condition,determine, on the basis that there will be no loss of traction by any of the wheels, a proposed distribution of the torque requested by a driver or other controller of the vehicle to meet one or more predetermined vehicle level attributes,determine proposed torques to be applied by each propulsion unit,compare the proposed torque for at least one propulsion unit with the maximum and minimum torques determined for that propulsion unit,and generate at least one control signal for at least one propulsion unit, at least one control signal being such that the at least one propulsion unit applies the proposed torque for that control unit to the axle with which the control unit is associated if the comparison between the proposed torque for at least one propulsion unit and the maximum and minimum torques determined for that propulsion unit shows that the proposed torque is equal to or between the maximum and minimum torques. If the comparison between the proposed torque for at least one propulsion unit and the maximum and minimum torques determined for that propulsion unit shows that the proposed torque is greater than the maximum torque or less than the minimum torque, then the controller may generate at least one control signal for at least one propulsion unit, the at least one control signal being such that the at least one propulsion unit applies a torque with a predetermined relationship to the proposed torque for that propulsion unit to the axle with which the propulsion unit is associated. The predetermined relationship may be such that the total torque applied by the propulsion units is between the maximum and minimum torques determined for that propulsion unit. The predetermined relationship may be such that the total torque may be less than the torque requested by a driver or other controller of the vehicle. This is useful and improves safety of the vehicle if the requested torque may be predicted to result in loss of traction by one or more wheels. The maximum and minimum torques are determined according to one or more predetermined criteria. One of those criteria may be to ensure that none of the wheels lose traction on the surface over which the vehicle is or will be moving. As such, the maximum and minimum torques may be determined with reference to at least one vehicle operating condition. For example, such conditions include but are not limite