Patent Grant
12017642
This application pertains to the field of automobile control technologies, and in particular, relates to a method and an apparatus for front and rear driving torque distribution of a vehicle, and a vehicle.
At present, in addition to being distributed based on a fixed ratio, driving torque distribution between front and rear axles of a vehicle driven in a front-to-rear centralized manner is usually based on efficiency of a motor and/or an engine or axle loads of the front and rear axles (load weights of the front and rear axles), so that the vehicle can obtain better economy and power performance. However, such distribution policy of torque between the front and rear axles does not fully consider vehicle stability. As a result, the vehicle may lose stability in a steering condition when oversteer or understeer tends to occur.
This application provides a method and an apparatus for front and rear driving torque distribution of a vehicle, and a vehicle, so that a real-time torque distribution coefficient of a vehicle can be determined based on a real-time correction yawing moment of the vehicle and a mapping relationship between a correction yawing moment and a torque distribution coefficient. This improves operation stability of the vehicle during steering, and provides high applicability.
According to a first aspect, this application provides a method for front and rear driving torque distribution of a vehicle. The method includes: determining an expected status parameter existing during steering of a vehicle based on a wheel angle of the vehicle; determining a current correction yawing moment based on an actual status parameter existing during the steering of the vehicle and the expected status parameter; determining a mapping relationship between a correction yawing moment and a torque distribution coefficient based on the wheel angle and acceleration information of the vehicle; determining the torque distribution coefficient of the vehicle based on the current correction yawing moment and the mapping relationship; and determining front and rear axle driving torques of the vehicle based on the torque distribution coefficient of the vehicle.
In this embodiment of this application, a real-time torque distribution coefficient of the vehicle can be determined based on a real-time correction yawing moment of the vehicle and the mapping relationship between a correction yawing moment and a torque distribution coefficient, and further the real-time front and rear axle driving torques of the vehicle is determined. This improves stability of the vehicle, and provides high applicability.
With reference to the first aspect, in a first possible implementation, the method includes: determining maximum correctable yawing moment and minimum correctable yawing moment based on the wheel angle and the acceleration information; and determining the mapping relationship based on the wheel angle, the maximum correctable yawing moment, and the minimum correctable yawing moment.
In this embodiment of this application, the mapping relationship between a correction yawing moment and a torque distribution coefficient may be dynamically determined based on a real-time wheel angle and the acceleration information of the vehicle. This improves operation stability during steering of a vehicle.
With reference to the first aspect, in a second possible implementation, the method includes: if it is determined, based on the wheel angle, that the steering of the vehicle is to turn left, determining that the mapping relationship is i=(ΔMcor,max−ΔMreq)/(ΔMcor,max−ΔMcor,min), where i is the torque distribution coefficient, ΔMcor,max is the maximum correctable yawing moment, ΔMcor,min is the minimum correctable yawing moment, ΔMreq is the correction yawing moment, and ΔMcor,min≤ΔMreq≤ΔMcor,max.
In this embodiment of this application, when it is determined that the steering of the vehicle is to turn left, and ΔMcor,min≤ΔMreq≤ΔMcor,max, the mapping relationship between a correction yawing moment and a torque distribution coefficient is determined as i=(ΔMcor,max−ΔMreq)/(ΔMcor,max−ΔMcor,min).
With reference to the first aspect, in a third possible implementation, the method includes: if it is determined, based on the wheel angle, that the steering of the vehicle is to turn right, determining that the mapping relationship is i=(ΔMreq−ΔMcor,min)/(ΔMcor,max−ΔMcor,min), where i is the torque distribution coefficient, ΔMcor,max is the maximum correctable yawing moment, ΔMcor,min is the minimum correctable yawing moment, ΔMreq is the correction yawing moment, and ΔMcor,min≤ΔMreq≤ΔMcor,max.
In this embodiment of this application, when it is determined that the steering of the vehicle is to turn right, and ΔMcor,min≤ΔMreq≤ΔMcor,max, the mapping relationship between a correction yawing moment and a torque distribution coefficient is determined as i=(ΔMreq−ΔMcor,min)/(ΔMcor,max−ΔMcor,min).
With reference to the first aspect, in a fourth possible implementation, the method includes: obtaining a current road surface adhesion coefficient of the vehicle, and determining the maximum correctable yawing moment and the minimum correctable yawing moment based on the road surface adhesion coefficient, the wheel angle, and the acceleration information.
In this embodiment of this application, when the maximum correctable yawing moment and the minimum correctable yawing moment are determined, not only the real-time wheel angle and the acceleration information of the vehicle are considered, but also impact of the road surface adhesion coefficient on the operation stability of the vehicle during steering is considered. This improves the operation stability of the vehicle during steering.
With reference to the first aspect, in a fifth possible implementation, the method includes: determining a maximum front axle cornering force and a maximum rear axle cornering force of the vehicle based on the road surface adhesion coefficient and the acceleration information; determining the maximum correctable yawing moment based on the maximum front axle cornering force and the wheel angle; and determining the minimum correctable yawing moment based on the maximum rear axle cornering force.
In this embodiment of this application, when the maximum front axle cornering force and the maximum rear axle cornering force of the vehicle are determined, the maximum correctable yawing moment is determined based on the maximum front axle cornering force and the wheel angle and the minimum correctable yawing moment is determined based on the maximum rear axle cornering force.
With reference to the first aspect, in a sixth possible implementation, the method includes: determining a vertical load of each wheel based on a longitudinal acceleration and a lateral acceleration; and determining the maximum front axle cornering force and the maximum rear axle cornering force based on the vertical load of each wheel and the road surface adhesion coefficient.
In this embodiment of this application, when the vertical load of each wheel is obtained through calculation based on the longitudinal acceleration and the lateral acceleration, the maximum front axle cornering force and the maximum rear axle cornering force of the vehicle may be determined based on the tire ellipse theory, the vertical load of each wheel, and the road surface adhesion coefficient.
With reference to the first aspect, in a seventh possible implementation, the method includes: determining a minimum value of vertical loads of all front wheels as a corrected front axle-wheel vertical load, and determining a minimum value of vertical loads of all rear wheels as a corrected rear axle-wheel vertical load; determining the maximum front axle cornering force based on the corrected front axle-wheel vertical load and the road surface adhesion coefficient; and determining the maximum rear axle cornering force based on the corrected rear axle-wheel vertical load and the road surface adhesion coefficient.
In this embodiment of this application, a minimum value of vertical load of two wheels on a same axle is determined as corrected vertical load of the two wheels on the axle, to correct the vertical load of each wheel, so that a single wheel on the same axle can be prevented from slipping. In this way, the maximum front axle cornering force and the maximum rear axle cornering force can be determined based on the tire ellipse theory, the corrected front axle-wheel vertical load, the corrected rear axle-wheel vertical load, and the road surface adhesion coefficient.
With reference to the first aspect, in an eighth possible implementation, the method includes: if it is determined, based on the wheel angle, that the steering of the vehicle is to turn left, and the correction yawing moment is less than the minimum correctable yawing moment, determining the torque distribution coefficient of the vehicle as a first preset coefficient; if it is determined, based on the wheel angle, that the steering of the vehicle is to turn left, and the correction yawing moment is greater than the maximum correctable yawing moment, the torque distribution coefficient of the vehicle is a second preset coefficient; if it is determined, based on the wheel angle, that the steering of the vehicle is to turn right, and the correction yawing moment is less than the minimum correctable yawing moment, the torque distribution coefficient of the vehicle is a third preset coefficient; or if it is determined, based on the wheel angle, that the steering of the vehicle is to turn right, and the correction yawing moment is greater than the maximum correctable yawing moment, the torque distribution coefficient of the vehicle is a fourth preset coefficient.
In this embodiment of this application, when the correction yawing moment is less than the minimum correctable yawing moment, or the correction yawing moment is greater than the maximum correctable yawing moment, the torque distribution coefficient of the vehicle is the preset coefficient.
With reference to the first aspect, in a ninth possible implementation, the method includes: if the current correction yawing moment is less than the minimum correctable yawing moment, or the current correction yawing moment is greater than the maximum correctable yawing moment, sending a correction trigger instruction to an electronic stability control system ESC, to trigger the ESC to output a braking torque of each wheel.
In this embodiment of this application, when it is determined that the current correction yawing moment is less than the minimum correctable yawing moment, or the current correction yawing moment is greater than the maximum correctable yawing moment, ESC may be triggered to intervene, to correct a steering status of the vehicle.
With reference to the first aspect, in a tenth possible implementation, the method includes: determining the current correction yawing moment of the vehicle based on a deviation between an actual yaw velocity and an expected yaw velocity and a deviation between an actual centroid side-slip angle and an expected centroid side-slip angle.
In this embodiment of this application, when the current correction yawing moment of the vehicle is determined, impact of the yaw velocity and the centroid side-slip angle on the operation stability of the vehicle during steering are corrected. This improves the operation stability of the vehicle during steering.
With reference to the first aspect, in an eleventh possible implementation, the method includes: obtaining a total required driving torque of the vehicle; and determining the front and rear axle driving torques of the vehicle based on the total required driving torque and the torque distribution coefficient, and sending the front and rear axle driving torques to corresponding motor controllers.
In this embodiment of this application, after a front axle torque distribution coefficient and a rear axle torque distribution coefficient are determined, the front axle driving torque and the rear axle driving torque of the vehicle may be obtained based on a product of the total required driving torque of the vehicle and the front axle driving torque distribution coefficient and a product of the total required driving torque of the vehicle and the rear axle driving torque distribution coefficient respectively.
According to a second aspect, this application provides an apparatus for front and rear driving torque distribution of a vehicle. The apparatus includes a unit and/or a module configured to perform the method for front and rear driving torque distribution of a vehicle provided in any one of the first aspect and/or the possible implementations of the first aspect. Therefore, beneficial effects of the method for front and rear driving torque distribution of a vehicle according to the first aspect can also be achieved.
According to a third aspect, this application provides a vehicle. The vehicle includes the apparatus for front and rear driving torque distribution of a vehicle provided in the second aspect. Therefore, beneficial effects of the method for front and rear driving torque distribution of a vehicle according to the first aspect can also be implemented.
According to a fourth aspect, this application provides an apparatus for front and rear driving torque distribution of a vehicle. The apparatus includes a processor, a memory, and a transceiver. The processor, the memory, and the transceiver are connected to each other. The transceiver is configured to receive or send data. The memory is configured to store instructions. The processor is configured to invoke the instructions stored in the memory, to perform the method for front and rear driving torque distribution of a vehicle according to the first aspect and/or any possible implementation of the first aspect. Therefore, beneficial effects of the method for front and rear driving torque distribution of a vehicle according to the first aspect can also be implemented.
According to a fifth aspect, this application provides a computer storage medium, including computer-readable instructions. When the computer-readable instructions are run by one or more processors, the method for front and rear driving torque distribution of a vehicle according to any one of the first aspect and/or the possible implementations of the first aspect is performed. Therefore, beneficial effects of the method for front and rear driving torque distribution of a vehicle according to the first aspect can also be implemented.
In this application, the real-time torque distribution coefficient of the vehicle may be determined based on the real-time correction yawing moment of the vehicle and the real-time mapping relationship between a correction yawing moment and a torque distribution coefficient. This improves the operation stability of the vehicle during steering, and provides high applicability.
The method for front and rear driving torque distribution of a vehicle provided in this application is specifically a method for torque distribution between front and rear axles of an electric vehicle based on front-to-rear centralized driving manner in a steering working condition, and is referred to as a method for torque distribution between front and rear axles for short. The method is applicable to the vehicle control field.
Torque distribution between front and rear axles is a key technology of four-wheel drive automobiles. Power and stability performance of vehicles can be effectively improved by controlling the torque distribution between front and rear axles. At present, in addition to being distributed based on a fixed ratio, driving torque distribution between front and rear axles of a vehicle driven in a front-to-rear centralized manner is usually based on efficiency of a motor and/or an engine or axle loads of the front and rear axles (load weights of the front and rear axles), so that the vehicle can obtain better economy and power. However, such distribution policy of torque between the front and rear axles does not fully consider vehicle stability. As a result, the vehicle may lose stability in a steering condition when oversteer or understeer tends to occur.
With an advantage of fast response of a motor, vehicle control systems (such as an anti-lock brake system (ABS), a traction control system (TCS), and an electronic stability control system (ESC) can be effectively coordinated and controlled through the torque distribution between front and rear axles. An ESC dynamics control algorithm uses braking force vectoring control to provide a braking force to perform vehicle braking and an additional yawing moment to improve vehicle operation performance and stability. A torque vectoring (TV) control algorithm uses driving force vectoring control to provide a driving force to drive a vehicle and an additional yawing moment to improve vehicle operation performance and stability. A front to rear torque vectoring (FRTV) control algorithm provided in this application belongs to one of TV control algorithms.
An input end of the apparatus 26 for front and rear driving torque distribution of a vehicle is separately connected to the accelerator pedal 21, the inertial measurement unit 22, the steering wheel angle sensor 23, the braking system 24, and the battery management system 25 through a CAN bus. An output end of the apparatus 26 for front and rear driving torque distribution of a vehicle is separately connected to the front axle motor controller 27 and the rear axle motor controller 28 through the CAN bus. The front axle motor controller 27 is connected to the front drive motor 29, and the rear axle motor controller 28 is connected to the rear drive motor 210.
In some feasible implementations, with reference to
The signal processing module receives an actual yaw velocity {dot over (φ)}act, a longitudinal acceleration ax, and a lateral acceleration ay that are sent by the inertial measurement unit 22, and a steering wheel angle δ sent by the steering wheel angle sensor 23, obtains a vehicle speed ν, a road surface adhesion coefficient μ, and an actual centroid side-slip angle βact through calculation based on the foregoing parameters, sends ν, and δ to the expected value calculation module, sends μ, ax, and ay to the mapping relationship determining module, and sends δ to the vehicle steering determining module.
The expected value calculation module calculates an expected yaw velocity {dot over (φ)}ref and an expected centroid side-slip angle βref based on ν and δ, and sends {dot over (φ)}ref and βref to the correction yawing moment calculation module.
The correction yawing moment calculation module obtains a current correction yaw torque ΔM of the vehicle through calculation based on an error Δ{dot over (φ)}={dot over (φ)}act−{dot over (φ)}ref act ref between the actual yaw velocity and the expected yaw velocity, and an error Δβ=βact−βref between the actual centroid side-slip angle and the expected centroid side-slip angle. It may be understood that ΔM is a yawing moment used to correct a steering status of the vehicle. Then, the correction yawing moment calculation module sends ΔM to the front and rear axle torque distribution module and the ESC intervention determining module separately.
The vehicle steering determining module may obtain a front wheel angle δf through calculation based on δ=δf*i, where i is a transfer ratio between a steering wheel to a front axle steering wheel, and then determine steering of the vehicle based on δf, and separately send the steering of the vehicle to the mapping relationship determining module and the front and rear axle torque distribution module.
The mapping relationship determining module obtains, through calculation based on μ, ax, and ay, a maximum correctable yawing moment ΔMcor,max and a minimum correctable yawing moment ΔMcor,min that can be implemented through torque distribution between front and rear axles, determines a mapping relationship between a correction yawing moment and a torque distribution coefficient based on the steering of the vehicle, ΔMcor,max, and ΔMcor,min, sends the mapping relationship between a correction yawing moment and a torque distribution coefficient to the front and rear axle torque distribution module, and sends ΔMcor,max and ΔMcor,min to the ESC intervention determining module. The foregoing mapping relationship is applicable to a case in which the correction yawing moment is greater than or equal to ΔMcor,min, and the correction yawing moment is less than or equal to ΔMcor,max.
The ESC intervention determining module may determine whether an ESC function is required to intervene based on a value relationship between ΔM, ΔMcor,min, and ΔMcor,max. When ΔMcor,min≤ΔM≤ΔMcor,max, the ESC function does not intervene; or when ΔM<ΔMcor,min or ΔM>ΔMcor,max, the ESC function intervenes, and an ESC intervention determining result is sent to the front and rear axle torque distribution module.
Then, when determining that an ESC intervention determining result is being not to intervene, the front and rear axle torque distribution module determines a front axle torque distribution coefficient and a rear axle torque distribution coefficient based on the mapping relationship and ΔM, and obtains the front axle driving torque TF and the rear axle driving torque TR of the vehicle through calculation based on the front axle torque distribution coefficient and the rear axle torque distribution coefficient and Treq, and then outputs TF and TR respectively to the front axle motor controller 27 and the rear axle motor controller 28. The front axle motor controller 27 controls, based on TF, the front drive motor 29 to run, and the rear axle motor controller 28 controls, based on TR, the rear drive motor 210 to run.
Further, when determining that an ESC intervention determining result is being to intervene, the front and rear axle torque distribution module determines the front axle torque distribution coefficient and the rear axle torque distribution coefficient as preset coefficients based on the steering of the vehicle, obtains TF, and TR, through calculation based on the preset coefficients and Treq, and outputs TF and TR to the front axle motor controller 27 and the rear axle motor controller 28 respectively. The front axle motor controller 27 controls, based on TF, the front drive motor 29 to run, and the rear axle motor controller 28 controls, based on TR, the rear drive motor 210 to run, to help the driver reduce a trend of understeer and a trend of oversteer in a steering working condition, so as to improve steering stability of the vehicle.
In addition, after the ESC intervention determining module determines that the ESC intervention determining result is being to intervene, that is, after it is determined that the ESC intervention determining result is being to intervene, the apparatus 26 for front and rear driving torque distribution of a vehicle sends a correction trigger instruction to the ESC controller 241 in the braking system 24. The ESC controller 241 obtains a braking torque of each wheel through calculation based on the instruction, and outputs the braking torque of each wheel to the wheel braking apparatus 242 corresponding to each wheel.
In this embodiment of this application, the apparatus 26 for front and rear driving torque distribution of a vehicle may dynamically perform torque distribution between front and rear axles based on real-time steering of the vehicle, the current correction yawing moment, and the mapping relationship between a correction yawing moment and a torque distribution coefficient, to improve operation stability and a track tracking capability of the vehicle in a steering working condition.
The following describes, with reference to the apparatus for front and rear driving torque distribution of a vehicle shown in
S101: Determine, based on a wheel angle of a vehicle, an expected status parameter existing during steering of the vehicle.
The expected status parameter includes an expected yaw velocity and an expected centroid side-slip angle.
In some feasible implementations, the apparatus 26 for front and rear driving torque distribution of a vehicle may establish a two-degree-of-freedom vehicle model of the vehicle, and obtain an actual yaw velocity {dot over (φ)}act, a longitudinal acceleration ax, and a lateral acceleration ay of the vehicle by using the inertial measurement unit 22, obtain a steering wheel angle δ by using the steering wheel angle sensor 23, and calculate a longitudinal vehicle speed estimation value νx′ and a lateral vehicle speed estimation value νy′ of the vehicle based on {dot over (φ)}act, ax and ay as well as the two-degree-of-freedom vehicle model of the vehicle. A longitudinal speed νx and a lateral speed νy of the vehicle are calculated by using the extended Kalman filter and based on νx′, νy′, ax, and ay. Then, the apparatus 26 for front and rear driving torque distribution of a vehicle may obtain the expected yaw velocity {dot over (φ)}ref and the expected centroid side-slip angle βref through calculation based on δ, νx, and νy as well as the two-degree-of-freedom vehicle model of the vehicle.
S102: Determine a current correction yawing moment based on an actual status parameter existing during the steering of the vehicle and the expected status parameter.
The actual status parameter includes an actual yaw velocity and an actual centroid side-slip angle.
Before performing step S102, the apparatus 26 for front and rear driving torque distribution of a vehicle may obtain, through calculation based on νx and νy, a speed ν of the vehicle, and obtain the actual centroid side-slip angle βact through calculation based on ν.
Then, the apparatus 26 for front and rear driving torque distribution of a vehicle determines the current correction yawing torque of the vehicle based on βact, {dot over (φ)}act, {dot over (φ)}ref, and βref.
In some feasible implementations, the apparatus 26 for front and rear driving torque distribution of a vehicle determines the current correction yawing torque ΔM of the vehicle based on a deviation Δ{dot over (φ)}={dot over (φ)}act−{dot over (φ)}ref between {dot over (φ)}act and {dot over (φ)}ref, and a deviation Δβ=βact−βref between βact and βref.
In an embodiment, Δ{dot over (φ)} and Δβ may be used as input parameters of a proportional-integral-differential (PID) control algorithm to determine the current correction yawing moment ΔM of the vehicle.
In another embodiment, a fuzzy control algorithm may be used, Δ{dot over (φ)} and Δβ are used as input, and ΔM is used as output, a triangular membership function is used for Δ{dot over (φ)}, Δβ, and ΔM. Δ{dot over (φ)} and Δβ are divided into seven fuzzy subsets: NB (negative big), NM (negative medium), NS (negative small), ZE (zero), PS (positive small), PM (positive medium), and PB (positive big). To improve control precision, the output additional yawing moment is divided into nine fuzzy subsets: NVB (negative very big), NB (negative big), NM (negative medium), NS (negative small), ZE (zero), PS (positive small), PM (positive medium), PB (positive big), and PVB (positive very big). Then, a fuzzy quantity is output based on a fuzzy control rule. The fuzzy control rule may be as follows: when understeer occurs (Δ{dot over (φ)}<0), a positive correction yawing moment needs to be applied to reduce a trend of understeer of the vehicle, and ΔM is determined based on Δ{dot over (φ)} and Δβ. When an absolute value |Δ{dot over (φ)}| of a yaw velocity error is large, a large ΔM is output, and when |Δ{dot over (φ)}| is small, a positive correction yawing moment ΔM increases with an increase of an absolute value |Δβ| of a centroid side-slip angle error. When oversteer occurs (Δ{dot over (φ)}>0), a negative correction yawing moment needs to be applied to reduce a trend of oversteer of the vehicle, and ΔM is determined based on Δ{dot over (φ)} and Δβ. When |Δ{dot over (φ)}| is large, a negative correction yawing moment ΔM with a large absolute value is output. When |Δ{dot over (φ)}| is small, an absolute value of the negative correction yawing moment ΔM decreases with a decrease of |Δβ|. Afterward, the center of gravity method is used to convert the output fuzzy quantity into an accurate control quantity, and the current correction yawing moment ΔM of the vehicle is obtained.
S103: Determine a mapping relationship between a correction yawing moment and a torque distribution coefficient based on the wheel angle and acceleration information of the vehicle.
The wheel angle may be a front wheel angle, and the acceleration information includes a longitudinal acceleration and a lateral acceleration.
In a feasible implementation, the apparatus for front and rear driving torque distribution of a vehicle obtains a current road surface adhesion coefficient of the vehicle, determines a vertical load of each wheel of the vehicle based on the longitudinal acceleration and the lateral acceleration, determines a minimum value of vertical loads of all front wheels as a corrected front axle-wheel vertical load, determines a minimum value of vertical loads of all rear wheels as a corrected rear axle-wheel vertical load, determines a maximum front axle cornering force based on the corrected front axle-wheel vertical load and the road surface adhesion coefficient, and determines a maximum rear axle cornering force based on the corrected rear axle-wheel vertical load and the road surface adhesion coefficient. The maximum correctable yawing moment is determined based on the maximum front axle cornering force and the wheel angle, and the minimum correctable yawing moment is determined based on the maximum rear axle cornering force.
Specifically, the apparatus 26 for front and rear driving torque distribution of a vehicle may obtain a left front wheel side-slip angle δf1 and a right front wheel side-slip angle δf2, through calculation based on the longitudinal speed νx and a lateral speed νy of the vehicle, the actual yaw velocity {dot over (φ)}act, a yaw velocity gain Δ{dot over (φ)}, and the two-degree-of-freedom vehicle model, and input {dot over (φ)}act, Δ{dot over (φ)}, δf1, and δf2 into a BP neural network structure. The current road surface adhesion coefficient μ of the vehicle is estimated by using a BP neural network algorithm.
Then, the vertical load of each wheel of the vehicle is determined based on the longitudinal acceleration and the lateral acceleration.
Fz,FL=0.5mglr/(lf+lr)−0.5maxh/(lf+lr)−maylrh/((lf+lr)*df)
Fz,FR=0.5mglr/(lf+lr)−0.5maxh/(lf+lr)+maylrh/((lf+lr)*df)
Fz,RL=0.5mglr/(lf+lr)+0.5maxh/(lf+lr)−maylrh/((lf+lr)*dr)
Fz,RR=0.5mglr/(lf+lr)+0.5maxh/(lf+lr)+maylrh/((lf+lr)*dr)
Fz,FL, Fz,FR, Fz,RL, and Fz,RR are respectively a vertical load of a left front wheel, a vertical load of a right front wheel, a vertical load of a left rear wheel, and a vertical load of a right rear wheel in the vehicle dual-track model shown in
It may be understood that the vertical load of each wheel is a sum of a static load 0.5 mglr/(lf+lr) of the vehicle, a variation that is of a wheel load and that is caused by a longitudinal inertia force, and a variation that is of the wheel load and that is caused by a lateral inertia force.
To avoid slipping of a single wheel on a same axle, vertical loads of the left and right wheels on the same axle are corrected. A minimum value of the vertical loads of the left and right wheels on the front axle is determined as the corrected front-axle wheel vertical load, and a minimum value of the vertical loads of the left and right wheels on the rear axle is determined as the corrected rear axle-wheel vertical load, that is,
Fz,FL,cor=Fz,FR,cor=min(Fz,FL,Fz,FR)=0.5mglr/(lf+lr)−0.5maxh/(lf+lr)−maylrh/((lf+lr)*df)
Fz,RL,cor=Fz,RR,cor=min(Fz,RL,Fz,RR)=0.5mglr/(lf+lr)+0.5maxh/(lf+lr)−maylrh/((lf+lr)*dr)
Fz,FL,cor, Fz,FR,cor, Fz,RL,cor, and Fz,RR,cor are respectively a corrected vertical load of the left front wheel, a corrected vertical load of the right front wheel, a corrected vertical load of the left rear wheel, and a corrected vertical load of the right rear wheel.
Then, the apparatus 26 for front and rear driving torque distribution of a vehicle may determine the maximum front axle cornering force based on the corrected front axle-wheel vertical load and the road surface adhesion coefficient, and determine the maximum rear axle cornering force based on the corrected rear axle-wheel vertical load and the road surface adhesion coefficient.
Specifically,
In actual working conditions, the tire is affected by longitudinal, lateral and vertical forces, but when a vertical load and a road surface adhesion coefficient are not changed, a resultant force generated in a tire tread imprint is fixed, and a relationship between the three may be expressed as μFz=√{square root over (Fx2+Fy2)}, where is a road surface adhesion coefficient μ, and Fx, Fy, and Fz are longitudinal, lateral and vertical forces subjected to the tire respectively.
It can be learned based on
Then, the apparatus 26 for front and rear driving torque distribution of a vehicle may determine the maximum correctable yawing moment ΔMcor,max based on the maximum front axle cornering force Fy,F,max and the front wheel angle δf, and determine the minimum correctable yawing moment ΔMcor,min based on the maximum rear axle cornering force Fy,R,max.
The steering of the vehicle is determined based on the front wheel angle δf (for example, when δf>0, the steering of the vehicle is to turn right). The mapping relationship between a correction yawing moment and a torque distribution coefficient is further determined by the steering of the vehicle, the minimum correctable yawing moment and the maximum correctable yawing moment.
When it is determined that the steering of the vehicle is to turn left, the mapping relationship between a correction yawing moment and a torque distribution coefficient is determined based on the minimum correctable yawing moment and the maximum correctable yawing moment:
In an implementation,
When the vehicle turns left, if ΔMcor,min≤ΔMreq<0, because ΔMreq<0, it indicates that the yawing moment used to correct the steering status of the vehicle, that is ΔMreq, enables the vehicle to generate an effect of rotating clockwise around the vehicle centroid. That the vehicle turns left means that the vehicle actually moves in a counter-clockwise direction. Therefore, it may be determined that the vehicle has a trend of relative oversteer. It can be learned from
Further, with reference to
In another implementation,
If ΔMcor,min≤ΔMreq<0, it may be determined that the vehicle has a trend of relative oversteer. With reference to
In still another implementation,
When it is determined that the steering of the vehicle is to turn right, the mapping relationship between a correction yawing moment and a torque distribution coefficient is determined based on the minimum correctable yawing moment and the maximum correctable yawing moment:
When the vehicle turns right, if ΔMcor,min≤ΔMreq<0, because ΔMreq<0, indicates that the yawing moment used to correct the steering status of the vehicle, that is ΔMreq, enables the vehicle to generate an effect of rotating clockwise around the vehicle centroid. That the vehicle turns right means that the vehicle actually moves in a clockwise direction. Therefore, it may be determined that the vehicle has a trend of relative understeer. It can be learned with reference to
Further, with reference to
In another implementation.
In still another implementation.
It may be understood that, regardless of whether a diagram for the mapping relationship between a correction yawing moment and a torque distribution coefficient is in a form of a straight line (as shown in
S104: Determine a torque distribution coefficient of the vehicle based on the current correction yawing moment and the mapping relationship, and determine front and rear axle driving torques of the vehicle based on the torque distribution coefficient of the vehicle.
The torque distribution coefficient of the vehicle may be a front axle torque distribution coefficient, or may be a rear axle torque distribution coefficient, or may be a front axle torque distribution coefficient and a rear axle torque distribution coefficient. The front and rear axle driving torques of the vehicle include a front axle driving torque and a rear axle driving torque of the vehicle.
In an implementation, when the torque distribution coefficient of the vehicle is the front axle torque distribution coefficient, the apparatus 26 for front and rear driving torque distribution of a vehicle determines the front axle torque distribution coefficient based on the current correction yawing moment and the mapping relationship, obtains a total required driving torque of the vehicle, determines a product of the front axle torque distribution coefficient and the total required driving torque of the vehicle as the front axle driving torque of the vehicle, and determines a difference between the total required driving torque of the vehicle and the front axle driving torque of the vehicle as the rear axle driving torque of the vehicle.
For example, it is assumed that the torque distribution coefficient of the vehicle is the front axle torque distribution coefficient iF=0.6, and the total required driving torque of the vehicle is Treq=300N·m. The apparatus 26 for front and rear driving torque distribution of a vehicle may obtain the front axle driving torque TF=Treq*iF=180N·m of the vehicle through calculation, and then obtain the rear axle driving torque TR=Treq−TF=120N·m of the vehicle through calculation.
In another implementation, when the torque distribution coefficient of the vehicle is the rear axle torque distribution coefficient, the apparatus 26 for front and rear driving torque distribution of a vehicle determines a front axle torque distribution coefficient based on the current correction yawing moment and the mapping relationship, determines a difference between 1 and the front axle torque distribution coefficient as the rear axle torque distribution coefficient, obtains a total required driving torque of the vehicle, determines a product of the rear axle torque distribution coefficient and the total required driving torque of the vehicle as the rear axle driving torque of the vehicle, and determines a difference between the total required driving torque of the vehicle and the rear axle driving torque of the vehicle as the front axle driving torque of the vehicle.
For example, it is assumed that the apparatus 26 for front and rear driving torque distribution of a vehicle determines the front axle torque distribution coefficient iF=0.6 based on the current correction yawing moment and the mapping relationship, and obtains the total required driving torque Treq=300N·m of the vehicle. In this case, the apparatus 26 for front and rear driving torque distribution of a vehicle obtains the torque distribution coefficient of the vehicle through calculation, that is, the rear axle torque distribution coefficient iR=1−iF=0.4, and then obtains the rear axle driving torque TR=Treq*iR=120N·m of the vehicle through calculation, and further obtains the front axle driving torque TF=Treq−TR=170N·m of the vehicle through calculation.
In still another implementation, when the torque distribution coefficient of the vehicle is the front axle torque distribution coefficient and the rear axle torque distribution coefficient, the apparatus 26 for front and rear driving torque distribution of a vehicle determines the front axle torque distribution coefficient based on the current correction yawing moment and the mapping relationship, determines a difference between 1 and the front axle torque distribution coefficient as the rear axle torque distribution coefficient, obtains a total required driving torque of the vehicle, determines a product of the front axle torque distribution coefficient and the total required driving torque of the vehicle as the front axle driving torque of the vehicle, and determines a product of the rear axle torque distribution coefficient and the total required driving torque of the vehicle as the rear axle driving torque of the vehicle.
For example, it is assumed that the apparatus 26 for front and rear driving torque distribution of a vehicle determines the front axle torque distribution coefficient iF=0.6 based on the current correction yawing moment and the mapping relationship, and obtains the total required driving torque Treq=300N·m of the vehicle. In this case, the apparatus 26 for front and rear driving torque distribution of a vehicle obtains the rear axle torque distribution coefficient iR=1−iF=0.4 through calculation, and then obtains the front axle driving torque TF=Treq*iF=180N·m of the vehicle, and further obtains the rear axle driving torque TR=Treq*iR=120N·m of the vehicle through calculation.
The following describes this step by using an example in which the torque distribution coefficient of the vehicle is the front axle torque distribution coefficient and the rear axle torque distribution coefficient.
When it is determined, based on step S103, that the steering of the vehicle is to turn left:
In an embodiment, if the current correction yawing moment ΔM is greater than or equal to ΔMcor,min, and is less than or equal to ΔMcor,max, the front axle torque distribution coefficient iF=(ΔMcor,max−ΔM)/(ΔMcor,max−ΔMcor,min) may be obtained based on the mapping relationship between a correction yawing moment and a torque distribution coefficient shown in
In another embodiment, if ΔM<ΔMcor,min, the torque distribution coefficient of the vehicle may be a first preset coefficient, for example, iF=1, or iR=0; or if ΔM>ΔMcor,max, the torque distribution coefficient of the vehicle may be a second preset coefficient, for example, iF=0, or iR=1.
When it is determined, based on step S103, that the steering of the vehicle is to turn right:
In an embodiment, if ΔMcor,min≤ΔM≤ΔMcor,max, the front axle torque distribution coefficient iF=(ΔM−ΔMcor,min)/(ΔMcor,max−ΔMcor,min) may be obtained based on the mapping relationship between a correction yawing moment and a torque distribution coefficient shown in
In another embodiment, if ΔM<ΔMcor,min, the torque distribution coefficient of the vehicle may be a third preset coefficient, for example, iF=0, or iR=1; or if ΔM>ΔMcor,max, the torque distribution coefficient of the vehicle may be a fourth preset coefficient, for example, iF=1, or iR=0.
Then, the total required driving torque of the vehicle is determined, the front and rear axle driving torques of the vehicle are determined based on the total required driving torque and the torque distribution coefficient, and the front and rear axle driving torques are sent to corresponding motor controllers.
Specifically, the apparatus 26 for front and rear driving torque distribution of a vehicle may obtain an accelerator pedal location of the accelerator pedal 21, obtain a first output driving torque through calculation based on the accelerator pedal location, obtain a current effective power of the power battery in the battery management system 25, determine, based on the current effective power of the power battery, a second output driving torque supported by the power battery, and determine a minimum value of the first output driving torque and the second output driving torque as the total required driving torque Treq of the vehicle. The front axle driving torque TF=Treq*iF and the rear axle driving torque TR=Treq*iR of the vehicle are obtained through calculation based on the total required driving torque Treq, the front axle torque distribution coefficient iF, and the rear axle torque distribution coefficient iR.
Then, a principle of a proportional relationship between vertical loads of wheels on a same axle may be used, that is, the front axle driving torque TF and the rear axle driving torque TR are separately distributed based on proportions of vertical loads of wheels on a same axle to a vertical load corresponding to the axle, to obtain TFL, TFR, TRL, and TRR. For example, TFL=TF*Fz,FL/(Fz,FL+Fz,FR) and TFR=TF*Fz,FR/(Fz,FL+Fz,FR) are obtained based on a vertical load Fz,FL of the left front wheel and a vertical load Fz,FR of the right front wheel. After TFL, TFR, TRL, and TRR are obtained, TFL, TFR, TRL, and TRR are sent to motor controllers of the wheels, and the motor controller of each wheel controls a drive motor of each wheel to run. In the foregoing manner, the front and rear axle driving torques of the vehicle may be dynamically distributed to each wheel in real time based on a change of the vertical load of each wheel, to implement dynamic distribution of the driving torque of the wheel.
Further, the front axle driving torque TF and the rear axle driving torque TR may be equally divided, based on a principle of equal division, to obtain a driving torque TFL=TF/2 of the left front wheel, a driving torque TFR=TF/2 of the right front wheel, a driving torque TRL=TR/2 of the left rear wheel, and a driving torque TRR=TR/2 of the right rear wheel. In actual implementation, after TF and TR are obtained, TF are TR respectively sent to the front axle motor controller 27 and the rear axle motor controller 28. The front axle motor controller 27 controls the front drive motor 29 to run, the front drive motor 29 equally divides TF by using the differential, and outputs equally divided parts to the left front wheel and the right front wheel, respectively. The rear axle motor controller 28 controls and drives the rear drive motor 210 to run, and the rear drive motor 210 equally divides TR by using the differential, and outputs equally divided parts to the left rear wheel and the right rear wheel, respectively.
It should be noted that, for an electric vehicle driven in a front-to-rear centralized manner (front and rear axle double motor drive-type electric vehicle), in a process of distributing a driving torque on each axle to a left wheel and a right wheel corresponding to each axle, driving torques on the front and the rear axles may be directly equally distributed to the left wheel and the right wheel corresponding to each axle by using the foregoing equal division principle. In this manner, no additional hardware is required for the electric vehicle driven in a front-to-rear centralized manner, and hardware costs are low. However, when the foregoing principle of a proportional relationship between vertical loads of wheels on a same axle is used, a torque conversion apparatus is required to be added on the basis of original hardware, resulting in higher hardware costs.
Further, when ΔM<ΔMcor,min or ΔM>ΔMcor,max, the apparatus 26 for front and rear driving torque distribution of a vehicle sends a correction trigger instruction to the ESC controller 241, to trigger the ESC controller 241 to output the braking torque of each wheel.
Specifically, after the ESC controller 241 receives the correction trigger instruction sent by the apparatus 26 for front and rear driving torque distribution of a vehicle, the single wheel braking torque distribution strategy can be adopted, and the calculation is based on the current correction yawing moment ΔM and the front wheel angle δf of the vehicle. The braking torque of each wheel is obtained. A calculation process is as follows:
When the steering of the vehicle is to turn left, if ΔM<ΔMcor,min, because ΔMcor,min<0, it may be determined that the vehicle has a trend of oversteer. The ESC controller 241 obtains Tbfl=Tbrl=Tbrr=0 and Tbfr=TFR+R*|ΔM|/d1 through calculation, where d1=|lr*cos δf/2+lf*sin δf|, Tbfl is a braking torque of the left front wheel, and Tbfr is a braking torque of the right front wheel, Tbrl is the braking torque of the left rear wheel, Tbrr is the braking torque of the right rear wheel, and R is a wheel rolling radius; or if ΔM>ΔMcor,max, because ΔMcor,max>0, it may be determined that the vehicle has a trend of relative understeer, and the ESC controller 241 obtains Tbfl=Tbfr=Tbrr=0, Tbrl=TRL+R*|ΔM|/d2, and d2=2/lr through calculation.
When the steering of the vehicle is to turn right, if ΔM<ΔMcor,min, because ΔMcor,min<0, it may be determined that the vehicle has a trend of relative understeer, and the ESC controller 241 obtains Tbfl=Tbrl=Tbfr=0, Tbrr=TRR+R*|ΔM|/d2 through calculation; or if ΔM>ΔMcor,max, because ΔMcor,max>0, it may be determined that the vehicle has a trend of relative oversteer, and the ESC controller 241 obtains Tbfr=Tbfl=Tbrr=0, Tbfl=TFL+R*|ΔM|/d3, and d3=|lr*cos δf/2−lf*sin δf| through calculation.
Then, the ESC controller 241 outputs the braking torque of each wheel to the wheel braking apparatus 242 (for example, a caliper) corresponding to each wheel, to correct the steering status of the vehicle.
Further,
According to the method for torque distribution between front and rear axles provided in this application, in a case of working in the tire linear area, the torque distribution between front and rear axles can be dynamically performed based on the real-time steering in the steering condition of the vehicle, the real-time current correction yawing moment of the vehicle, and the real-time mapping relationship between a correction yawing moment and a torque distribution coefficient, to improve operation stability and a track tracking capability of the vehicle in the steering working condition, and reduce a probability of intervening of ESC.
The first determining module 141 is configured to determine, based on a wheel angle of a vehicle, an expected status parameter existing during steering of the vehicle.
The second determining module 142 is configured to determine a correction yawing moment based on an actual status parameter existing during the steering of the vehicle and the expected status parameter.
The third determining module 143 is configured to determine a mapping relationship between a correction yawing moment and a torque distribution coefficient based on the wheel angle and acceleration information of the vehicle.
The fourth determining module 144 is configured to: determine a torque distribution coefficient of the vehicle based on the current correction yawing moment and the mapping relationship, and determine front and rear axle driving torques of the vehicle based on the torque distribution coefficient of the vehicle.
In some feasible implementations, the third determining module 143 includes:
In some feasible implementations, the mapping relationship determining unit 1432 includes:
In some feasible implementations, the mapping relationship determining unit 1432 further includes:
In some feasible implementations, the yawing moment threshold determining unit 1431 is configured to: obtain a current road surface adhesion coefficient of the vehicle, and determine the maximum correctable yawing moment and the minimum correctable yawing moment based on the road surface adhesion coefficient, the wheel angle, and the acceleration information.
In some feasible implementations, the yawing moment threshold determining unit 1431 includes:
In some feasible implementations, the acceleration information includes a longitudinal acceleration and a lateral acceleration; and
In some feasible implementations, the maximum cornering force determining subunit 14311 is configured to:
In some feasible implementations, the apparatus further includes:
In some feasible implementations, the apparatus further includes:
In some feasible implementations, the actual status parameter includes an actual yaw velocity and an actual centroid side-slip angle, and the expected status parameter includes an expected yaw velocity and an expected centroid side-slip angle.
The second determining module 142 is configured to:
In some feasible implementations, the fourth determining module 144 includes:
It may be understood that the apparatus 14 for front and rear driving torque distribution of a vehicle is configured to implement the steps performed by the apparatus for front and rear driving torque distribution of a vehicle in the embodiment shown in
In some feasible implementations, the processor 1501 determines a mapping relationship between a correction yawing moment and a torque distribution coefficient based on the wheel angle and the acceleration information of the vehicle, and specifically performs the following steps:
In some feasible implementations, the processor 1501 determines the mapping relationship based on the wheel angle, the maximum correctable yawing moment, and the minimum correctable yawing moment, and specifically performs the following step:
In some feasible implementations, the processor 1501 determines the mapping relationship based on the wheel angle, the maximum correctable yawing moment, and the minimum correctable yawing moment, and specifically performs the following step:
In some feasible implementations, the processor 1501 determines the maximum correctable yawing moment and the minimum correctable yawing moment based on the wheel angle and the acceleration information, and specifically performs the following step:
In some feasible implementations, the processor 1501 determines the maximum correctable yawing moment and the minimum correctable yawing moment based on the road surface adhesion coefficient, the wheel angle, and the acceleration information, and specifically performs the following steps:
In some feasible implementations, the acceleration information includes a longitudinal acceleration and a lateral acceleration.
The processor 1501 determines the maximum front axle cornering force and the maximum rear axle cornering force of the vehicle based on the road surface adhesion coefficient and the acceleration information, and specifically performs the following steps:
In some feasible implementations, the processor 1501 determines the maximum front axle cornering force and the maximum rear axle cornering force based on the vertical load of each wheel and the road surface adhesion coefficient, and specifically performs the following steps:
In some feasible implementations, the processor 1501 further specifically performs the following step:
In some feasible implementations, the processor 1501 further specifically performs the following step:
In some feasible implementations, the actual status parameter includes an actual yaw velocity and an actual centroid side-slip angle, and the expected status parameter includes an expected yaw velocity and an expected centroid side-slip angle.
The processor 1501 determines the current correction yawing moment based on the actual status parameter existing during the steering of the vehicle and the expected status parameter, and specifically performs the following step:
In some feasible implementations, the processor 1501 determines the front and rear axle driving torques of the vehicle based on the torque distribution coefficient of the vehicle, and specifically performs the following steps:
It may be understood that the apparatus 15 for front and rear driving torque distribution of a vehicle is configured to implement the steps performed by the apparatus for front and rear driving torque distribution of a vehicle in the embodiment shown in
In this application, the apparatus 15 for front and rear driving torque distribution of a vehicle may dynamically perform torque distribution between front and rear axles based on real-time steering of the vehicle in a steering condition, the current correction yawing moment of the vehicle, and the mapping relationship between a correction yawing moment and a torque distribution coefficient, to improve operation stability and a track tracking capability of the vehicle in a steering working condition, and reduce a probability of intervening of ESC.
In the several embodiments provided in this application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiment is merely an example. For example, division into the units is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces, indirect couplings or communication connections between the devices or units, or electrical connections, mechanical connections, or connections in other forms.
A person of ordinary skill in the art may understand that all or a part of the steps of the method embodiments may be implemented by a program instructing relevant hardware. The program may be stored in a computer-readable storage medium. When the program runs, the steps of the method embodiments are performed. The foregoing storage medium includes: any medium that can store program code, such as a removable storage device, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc.
When the foregoing integrated unit of the present invention is implemented in the form of a software functional module and sold or used as an independent product, the integrated unit may be stored in a computer-readable storage medium. Based on such understanding, the technical solutions in embodiments of the present invention can be essential or the part that contributes to the conventional technology can be embodied in the form of a software product. This computer software product is stored in a storage medium, and includes several instructions for instructing a computer device (which can be a personal computer, a server, or a network device) to perform all or some of the steps of the method described in the embodiments of the present invention. The foregoing storage medium includes various media that can store program code, such as a removable storage device, a ROM, a RAM, a magnetic disk, or a compact disc.
The foregoing descriptions are merely specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
This application is a continuation of International Application PCT/CN2020/141853, filed on Dec. 30, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
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| Number | Date | Country |
|---|---|---|
| 108248454 | Jul 2018 | CN |
| 108569168 | Sep 2018 | CN |
| 108595745 | Sep 2018 | CN |
| 109204303 | Jan 2019 | CN |
| 109204303 | Jan 2019 | CN |
| 106379198 | Jun 2019 | CN |
| 110147628 | Aug 2019 | CN |
| 110606075 | Dec 2019 | CN |
| 111806248 | Oct 2020 | CN |
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| 2571328 | Aug 2019 | GB |
| Entry |
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| English Translation of CN111806248A; http://translatinportal.epo.org; Jan. 31, 2024 (Year: 2024). |
| English Translation of CN109204303A; http://translatinportal.epo.org; Jan. 31, 2024 (Year: 2024). |
| Number | Date | Country | |
|---|---|---|---|
| 20230339456 A1 | Oct 2023 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2020/141853 | Dec 2020 | WO |
| Child | 18342677 | US |
