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EP-4737238-A1 - METHOD FOR IMPROVING STABILITY OF A VEHICLE COMPRISING DUAL CLUTCHES

EP4737238A1EP 4737238 A1EP4737238 A1EP 4737238A1EP-4737238-A1

Abstract

Method comprising detecting that the vehicle is performing a transitional maneuver or detecting a braking request or a propulsion torque reduction while the vehicle is driving in a curve at grip limit based on first data indicative of driver intentions and/or vehicle motion state, detecting instability of the vehicle based on the first data, adjusting a torque request to the two clutches in response to the detected instability, wherein the two clutches are arranged to transmit the propulsion torque generated by the propulsion actuator to the wheels based on the torque request and based on the propulsion torque generated by the propulsion actuator, and wherein the torque request is adjusted based on the vehicle motion state and/or driver intentions such that a yaw motion of the vehicle is reduced.

Inventors

  • SHEKHAR, Rudrendu
  • IDEGREN, MARTIN
  • Sondhi, Eshwar

Assignees

  • Volvo Car Corporation

Dates

Publication Date
20260506
Application Date
20241031

Claims (15)

  1. A method for a vehicle (300) comprising two clutches (304) connected to wheels (302) of the vehicle and arranged to transmit torque to the wheels of the vehicle, the two clutches being connected to a propulsion actuator (306), the method comprising: detecting (202) that the vehicle is performing a transitional maneuver or detecting a braking request or a propulsion torque reduction while the vehicle is driving in a curve at grip limit based on first data indicative of driver intentions and/or vehicle motion state; detecting (204) instability of the vehicle based on the first data; adjusting (206) a torque request to the two clutches (304) in response to the detected instability, wherein the two clutches (304) are arranged to transmit the propulsion torque generated by the propulsion actuator to the wheels (302) based on the torque request and based on the propulsion torque generated by the propulsion actuator (306), and wherein the torque request is adjusted based on the vehicle motion state and/or driver intentions such that a yaw motion of the vehicle is reduced.
  2. The method of claim 1, wherein the two clutches are located on a front and/or on a rear axle of the vehicle.
  3. The method according to claim 1, wherein adjusting (206) the torque request comprises increasing the torque request to the two clutches (304).
  4. The method according to claim 3, wherein increasing the torque request comprises increasing an individual capacity of each of the two clutches (304) to transmit torque to the wheels such that the sum of the individual capacities of the two clutches exceeds the propulsion torque generated by the propulsion actuator (306).
  5. The method of claim 4, wherein the torque increase is limited to a value such that the wheels connected to the two clutches rotate at substantially same speed.
  6. The method of claim 1, wherein the driver intentions is based on at least one of a propulsion torque request, steering wheel angle, and brake torque request and/or the driver intentions is obtained by applying mathematical models, and/or wherein the vehicle motion state is based on at least one of a lateral acceleration of the vehicle, a yaw rate of the vehicle and a rotational speed of wheels of the vehicle and/or the vehicle motion state is obtained by applying mathematical models.
  7. The method of claim 1, wherein the instability of the vehicle is detected by comparing driver intentions and/or vehicle motion to threshold values.
  8. The method of claim 7, wherein the threshold values depend on intended vehicle attributes.
  9. The method of claim 1, wherein the torque request is adjusted based on intended vehicle attributes.
  10. The method of claim 1, wherein detecting that the vehicle is driving in the curve at grip limit comprises at least one of detecting that a difference between actual steering angle and a predetermined steering angle is above a steering angle difference threshold, detecting that a difference between actual yaw rate and a predetermined yaw rate is above a yaw rate difference threshold, wherein the predetermined steering angle is calculated based on at least one of lateral acceleration, yaw rate, wheel speeds and/or mathematical models, and wherein the predetermined yaw rate is calculated based on at least one of steering wheel angle, lateral acceleration, wheel speeds, and/or mathematical model, and wherein detecting the braking request reduction comprises detecting if a brake torque request associated with the brake request is above a brake torque threshold, and wherein detecting the propulsion torque reduction comprises detecting that a gradient of the propulsion torque request is below (more negative than) a propulsion torque gradient threshold value.
  11. The method of claim 1, further comprising detecting the transitional maneuver by evaluating a yaw acceleration, a rate of change of steering wheel angle, or a rate of change of lateral acceleration.
  12. The method of claim 1, wherein adjusting (206) the torque request comprises decreasing the torque request to the two clutches (304) proportionally to an amount of understeering.
  13. The method according to claim 3, further comprising adjusting the torque request to decrease the individual capacity of the two clutches such that the sum of the individual capacities of the two clutches does not exceed the propulsion torque generated by the propulsion actuator (306) if a brake torque request exceeds a brake torque threshold and/or if friction brake torque is applied to one of the wheels connected to the two clutches and/or a propulsion torque request exceeds a propulsion torque threshold.
  14. A control unit for a vehicle (300) configured to perform the method of previous claims.
  15. A vehicle (300) comprising the control unit according to claim 14, a propulsion actuator and two clutches connected to the propulsion actuator.

Description

Technical Field The current disclosure relates to a method and/or an apparatus for improving stability of a vehicle comprising two clutches connected to the rear and/or front wheels of the vehicle and arranged to transmit torque to the rear and/or front wheels of the vehicle. Background Art A maneuver in which there is a quick change in the motion of the vehicle, is often called a transitional maneuver. One example of such a transitional maneuver is an evasive maneuver to avoid a sudden obstacle in the path of the vehicle by rapid steering as shown in Error! Reference source not found.A, wherein vehicle A is performing such evasive maneuver. This induces a quick change in the direction of the vehicle, and under certain circumstances, can lead to a loss of directional stability of the vehicle. As said, transitional maneuvers like a sudden lane change can lead to a loss of directional stability of a vehicle. When this happens, the driver is no longer able to control the heading of the vehicle by steering, and this can lead to severe accidents. Also, when driving in a curve at the grip limit, there might be a risk for a vehicle to lose directional stability when the accelerator pedal is suddenly released, or slight brake is applied. One example of such a situation is driving on twisty country roads. In such a case, there might be a situation where, in a tight bend the vehicle is going too fast, and the driver releases the accelerator pedal or presses the brake to slow down the vehicle. This leads to transfer of load from the rear axle to the front axle which in-turn can lead to loss of directional stability. Both situations can lead to severe accidents as the driver cannot control the vehicle's direction by steering. The problem gets exaggerated at higher vehicle speeds as this gives less time for the driver to react. Thus, there is a need to stabilize the vehicle during transitional maneuvers or while driving in a curve at the grip limit and suddenly releasing the accelerator pedal or pressing the brake pedal, which can be achieved by applying a corrective yaw torque, which dampens the yaw motion of the vehicle. Traditionally this is done by the Electronic Stability Control (ESC) system which applies brake torque on one or more wheels, which generates forces between the tire and the road, and helps stabilize the vehicle. Although very effective, the application of brake torque by the ESC system is always accompanied by a noise from the brake actuation unit, and a sudden deceleration proportional to the applied brake torque. Due to these reasons, the ESC system is not designed to be sensitive, otherwise it could unnecessarily intervene during sporty driving (like on a racetrack), which can be perceived as intrusive by the driver. As the ESC system is not very sensitive, in some situations, it leads to delayed interventions, which makes the vehicle difficult to control for the driver. Summary To complement the ESC system, this disclosure provides a method to use a torque vectoring dual clutch (TVDC) actuator to stabilize the vehicle, by overlocking the clutches during instability situations. Torque vectoring dual clutch (TVDC) is a type of transmission system that consists of two individual clutches driven by a propulsion actuator like an electric motor or a combustion engine. Each clutch is connected to a wheel, and the torque generated by the propulsion actuator can be unequally distributed between the left and the right wheel. TVDC also enables overlock, when the sum of the individual clutch capacities exceeds the torque from the propulsion actuator. When a vehicle is turning, the curve-inside wheel rotates slower than the curve-outside wheel. When the clutches are overlocked, the speed difference between the curve-inside and curve-outside wheels connected to the clutches is reduced, and thus forces between the tire and the road that resists the turn and dampens the yaw motion are generated. The present disclosure proposes a method to improve the directional stability of a vehicle by overlock interventions from the TVDC. These overlock interventions from the TVDC can be very sensitive as these are nearly not perceivable by the driver, because it neither creates noise nor deceleration unlike the ESC interventions. Thus, the yaw motion of the vehicle is dampened early, before the ESC system can intervene, which stabilizes the vehicle in a smooth manner. In a first aspect of the disclosure, a method for a vehicle is provided, wherein the vehicle comprises two clutches connected to wheels of the vehicle and arranged to transmit torque to the wheels of the vehicle, the two clutches also being connected to a propulsion actuator, and the method comprising detecting that the vehicle is performing a transitional maneuver or detecting a braking request or a propulsion torque reduction while the vehicle is driving in a curve at grip limit based on first data indicative of driver intentions and/or vehicle motion state,