EP-4737239-A1 - METHOD FOR DETERMINING AMOUNT OF OVERLOCKING IN A VEHICLE COMPRISING DUAL CLUTCHES

EP4737239A1EP 4737239 A1EP4737239 A1EP 4737239A1EP-4737239-A1

Abstract

A method for a vehicle is provided, wherein the vehicle comprising two clutches on an axle and arranged to transmit propulsion torque generated by a propulsion actuator to two wheels of the vehicle on the axle, the two clutches being connected to the propulsion actuator, the method comprising: determining first data indicative of a difference between a first speed at which one of the two wheels rotate and a second speed at which the other one of the two wheels rotate, wherein the first data is determined based on a track width and a yaw rate of the vehicle, determining second data indicative of a slip force based on the first data and a tire longitudinal stiffness of any of the two wheels, and determining third data indicative of a coupling torque based on the second data and a radius of any of the two wheels.

Inventors

SHEKHAR, Rudrendu
IDEGREN, MARTIN
Sondhi, Eshwar

Assignees

Volvo Car Corporation

Dates

Publication Date: 20260506
Application Date: 20241031

Claims (14)

A method for a vehicle (300) comprising two clutches (304) on an axle and arranged to transmit propulsion torque generated by a propulsion actuator (306) to two wheels of the vehicle on the axle, the two clutches being connected to the propulsion actuator (306), the method comprising: determining (202) first data indicative of a difference between a first speed at which one of the two wheels rotate and a second speed at which the other one of the two wheels rotate, wherein the first data is determined based on a track width and a yaw rate of the vehicle; determining (204) second data indicative of a slip force based on the first data and a tire longitudinal stiffness of any of the two wheels; and determining (206) third data indicative of a coupling torque based on the second data and a radius of any of the two wheels.
The method according to claim 1, further comprising adjusting a torque request to the two clutches based on the third data, wherein the two clutches are arranged to transmit the propulsion torque generated by the propulsion actuator to the two wheels based on the torque request and based on the propulsion torque generated by the propulsion actuator.
The method according to any of the previous claims, wherein the first data is determined as follows: V l − V r = ψ ˙ × T wherein V l is the first speed, V r is the second speed, ψ̇ is the yaw rate and T is the track width.
The method according to any of the previous claims, wherein determining the second data indicative of the slip force further comprises determining a slip ratio corresponding to the difference between the first and the second speeds.
The method of claim 4, wherein the slip ratio is determined as follows: SR = V l − V r × 2 / V l + V r wherein SR is the slip ratio, V l is the first speed and V r is the second speed.
The method according to any of claims 4 and 5, wherein the second data is determined as follows: F x SR = f SR wherein F x SR is the slip force, SR is the slip ratio and f is a function of the slip ratio.
The method according to any of the previous claims further comprising: determining a first coupling torque T c SR as follows: T c SR = F x SR × R F x SR is the slip force and R is the radius of any of the two wheels; determining a vertical force ( F z i ) acting on one of the two wheels located on the inner side of a curve on which the vehicle is turning based on a longitudinal and a lateral acceleration of the vehicle; determining a total force capacity ( F totcap i ) of the one of the two wheels on the inner side of a curve on which the vehicle is turning based on the vertical force ( F z i ) and a surface friction coefficient ( µ ) of a road being travelled by the vehicle; determining a lateral force ( F y i ) acting on the one of the two wheels on the inner side of a curve on which the vehicle is turning based on the lateral acceleration ( a y ) of the vehicle; determining a longitudinal force capacity ( F xcap i ) of the one of the two wheels on the inner side of a curve on which the vehicle is turning based on the lateral force ( F y i ) and the total force capacity ( F totcap i ); and determining a second coupling torque ( T c lim ) based on the longitudinal force capacity ( F xcap i ) , the radius of the one of the two wheels on the inner side of a curve on which the vehicle is turning and at least one of a propulsion torque and a brake torque being applied to the one of the two wheels on the inner side of a curve on which the vehicle is turning; wherein the coupling torque is equal to the first coupling torque if the second coupling torque is higher than the first coupling torque and wherein the coupling torque is equal to the second coupling torque if the first coupling torque is higher than the second coupling torque.
The method according to claim 7, wherein total force capacity ( F totcap i ) of the one of the two wheels on the inner side of a curve on which the vehicle is turning is determined as follows: F totcap i = μ × F z i wherein F totcap i is the total force capacity of the one of the two wheels on the inner side of a curve on which the vehicle is turning, µ is the surface friction coefficient of the road being travelled by the vehicle and F z i is the vertical force acting on the one of the two wheels on the inner side of a curve on which the vehicle is turning.
The method according to any of claims 7 and 8, wherein the longitudinal force capacity is determined as follows: F xcap i = F totcap i 2 − F y i 2 wherein F xcap i is the longitudinal force capacity of the one of the two wheels on the inner side of a curve on which the vehicle is turning F totcap i is the total force capacity of the one of the two wheels on the inner side of a curve on which the vehicle is turning and F y i is the lateral force acting on the one of the two wheels on the inner side of a curve on which the vehicle is turning.
The method according to any of claims 7-9, wherein the second coupling torque is determined as follows: T c lim = F xcap i − T prop i − T brk i × R i wherein T c lim is the second coupling torque, F xcap i is the longitudinal force capacity of the one of the two wheels on the inner side of a curve on which the vehicle is turning, T prop i a propulsion torque being applied to the one of the two wheels on the inner side of a curve on which the vehicle is turning, T brk i is the brake torque being applied to the one of the two wheels on the inner side of a curve on which the vehicle is turning and R i is the radius of the one of the two wheels on the inner side of a curve on which the vehicle is turning.
The method of any of the previous claims, wherein the two clutches are located on a front and/or on a rear axle of the vehicle.
The method according any of claims 2-11, wherein adjusting the torque request comprises increasing the torque request to the two clutches by increasing an individual capacity of each of the two clutches 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 and the transmitted torque is equal or less than the coupling torque.
A control unit for a vehicle (300) configured to perform the method of previous claims.
A vehicle (300) comprising the control unit according to claim 13, 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 determining amount of overlocking needed to equalize the speed of both the wheels of an axle in a vehicle comprising dual clutches. Background Art Torque vectoring dual clutch (TVDC) is a kind of transmission systems consisting 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. Summary TVDC 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. This allows to improve the directional stability of a vehicle by overlock interventions. These overlock interventions 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. As said, the present disclosure relates to vehicles having two wheels on an axle which can rotate independently from one another and an actuator that can connect these two wheels together such that they rotate at the same speed. Some examples of such an arrangement can be an axle with a TVDC actuator. Each clutch is connected to a wheel and can rotate independently by allowing some slippage on the clutches. When the clutch capacity is increased such that there is no slippage on the clutches, the wheels rotate together at the same speed. Another example of such an arrangement can be a vehicle having an axle with an electronic limited slip differential (ELSD). Such a device has an open differential with a clutch arrangement which allows both wheels on the axle to rotate independently when the clutch is disconnected. When the clutch capacity is increased significantly, the wheels are mechanically connected and rotate at the same speed. By connecting both wheels of an axle when needed, the directional stability of a vehicle in various situations can be improved. When a vehicle is going in a curve, the curve-inside wheels rotate slower than the curve-outside wheels. If the curve-inside and the curve-outside wheels are connected by the device, they are forced to rotate at the same speed. This generates forces in the tires that creates a yaw torque which opposes the turning of the vehicle and dampens the yaw motion. For instance, when a vehicle is pushed to the grip limit, it may lead to a loss of directional stability of the 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. 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 when it approaches the grip limit. This 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 creates that corrective yaw torque. 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. On the other hand, a corrective yaw torque can be applied by an actuator like TVDC, by mechanically connecting two wheels on the same axle, to force the curve-inside and the curve-outside wheel to rotate at the same speed. Such an intervention 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 very early, before the ESC system can intervene, which stabilizes the vehicle in a smooth manner. To achieve an effective intervention by mechanically connecting the curve-inside and the curve-outside wheels, it is important to know how much coupling torque needs to be applied by the appropriate actuator (TVDC actuator