Driving force control method and device for four-wheel drive vehicle, electronic equipment and storage medium

Abstract

The application provides a driving force control method of a four-wheel drive vehicle, which comprises the following steps: obtaining a target driving force of the vehicle, a steering angle of front wheels and actual wheel speeds of each wheel; wherein the target driving force comprises a target driving force of a front axle and a target driving force of a rear axle; calculating an estimated wheel speed of each wheel based on the target driving force, the steering angle and the actual wheel speeds; calculating a difference between the estimated wheel speed and the actual wheel speed; calculating a driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed when the difference between the estimated wheel speed and the actual wheel speed meets a preset condition; wherein the driving force correction amount comprises a driving force correction amount of the front axle and a driving force correction amount of the rear axle; and correcting the target driving force based on the driving force correction amount to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset condition is met. Therefore, the vehicle can quickly respond to working conditions such as sudden change of road friction coefficient, so that the straight driving performance and the steering stability of the vehicle are improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle control, and more particularly to a method, device, electronic device, and storage medium for controlling the driving force of a four-wheel drive vehicle. Background Technology

[0002] During vehicle operation, if a sudden change in the road friction coefficient occurs, the vehicle's wheels may slip. This is especially true in four-wheel drive vehicles with independent power sources for the front and rear axles. Even with the driving force of the front and rear axles remaining constant, slipping of one wheel will affect the movement of the opposite wheel (in four-wheel drive vehicles where the front and rear axles are connected by a differential gear, this will also affect the other three wheels besides the slipping wheel). This causes sudden changes in the acceleration, wheel speed, and yaw rate of the slipping wheel and the affected wheels, affecting the vehicle's handling stability and potentially preventing the vehicle from turning.

[0003] To address the aforementioned problems, those skilled in the art have proposed various devices or methods to counteract wheel slippage in vehicles. For example:

[0004] The four-wheel drive vehicle drive force distribution device (patent publication: 1994-55949) controls the distribution of drive force between the front and rear wheels by calculating the target yaw rate of the wheels and detecting the actual yaw rate of the wheels, so that the actual yaw rate matches the target yaw rate. However, since there is a response delay between wheel slippage and its impact on the vehicle's motion state (such as yaw rate, lateral acceleration, and stability coefficient), adjusting wheel speed by changing the yaw rate results in a slow response and poor control effect, making it difficult to adequately cope with conditions such as sudden changes in road friction coefficient.

[0005] The vehicle's front and rear drive force distribution control device (publication number: JP4781726B2) adjusts the magnitude of the tightening torque based on the vehicle's target lateral acceleration and actual lateral acceleration. However, since there is a response delay between wheel slippage and its impact on the vehicle's motion state (such as yaw rate, lateral acceleration, and stability coefficient), adjusting wheel speed through changes in lateral acceleration results in a slow response and poor control effect, making it difficult to cope with conditions such as sudden changes in road friction coefficient.

[0006] The front-to-rear drive force distribution ratio control device for four-wheel drive vehicles (Publication No.: JP2011235763A) aims to ensure that the stability coefficient of a four-wheel drive vehicle follows a target value. First, a correction amount for the stability coefficient is calculated based on the target and actual values. Then, the drive force distribution ratio between the front and rear axles is adjusted according to the calculated correction amount to reduce the difference between the target and actual stability coefficient values. The stability coefficient represents the stable cornering state of the vehicle and is not applicable to rapid response.

[0007] Therefore, how vehicles can respond quickly to working conditions such as sudden changes in road friction coefficient has become an urgent technical problem to be solved. Summary of the Invention

[0008] This addresses the technical problem that existing methods cannot respond quickly to working conditions such as sudden changes in road surface friction coefficient.

[0009] According to a first aspect of the present invention, a method for controlling the driving force of a four-wheel drive vehicle is provided, the method comprising:

[0010] The system acquires the vehicle's target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel; the target driving force includes the target driving force of the front axle and the target driving force of the rear axle.

[0011] Based on the target driving force, steering angle, and actual wheel speed, calculate the estimated wheel speed for each wheel;

[0012] Calculate the difference between the estimated wheel speed and the actual wheel speed;

[0013] If the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions, the driving force correction amount is calculated based on the difference between the estimated wheel speed and the actual wheel speed; wherein, the driving force correction amount includes the driving force correction amount of the front axle and the driving force correction amount of the rear axle.

[0014] Based on the driving force correction amount, the target driving force is corrected to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset conditions are met.

[0015] Optionally, based on the target driving force, steering angle, and actual wheel speed, the estimated wheel speed for each wheel is calculated, including:

[0016] Calculate the slip ratio of each wheel based on the target driving force;

[0017] Calculate the vehicle's center of gravity speed based on slip ratio and actual wheel speed;

[0018] When the steering angle is not equal to 0 degrees, calculate the turning radius of the center of gravity and the lateral slip angle of the vehicle based on the steering angle and the center of gravity velocity;

[0019] Based on the center of gravity turning radius and the vehicle's lateral slip angle, calculate the wheel turning radius and the wheel lateral slip angle for each wheel;

[0020] Based on the center of gravity velocity, center of gravity turning radius, wheel turning radius, and wheel lateral slip angle, calculate the estimated velocity of each wheel in its rotational plane direction;

[0021] Based on the estimated speed and slip ratio, the estimated wheel speed of each wheel is calculated.

[0022] Optionally, after calculating the vehicle's center of gravity speed based on the slip ratio and actual wheel speed, the method further includes;

[0023] With a steering angle of 0 degrees, the estimated wheel speed of each wheel is calculated based on the estimated speed of each wheel in the direction of its rotation and its slip ratio; where the estimated speed is equal to the center of gravity speed.

[0024] Optionally, if the difference between the estimated wheel speed and the actual wheel speed meets preset conditions, the driving force correction amount is calculated based on the difference between the estimated wheel speed and the actual wheel speed, including:

[0025] If the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions, the excess slip ratio of each wheel is calculated based on the difference between the estimated wheel speed and the actual wheel speed.

[0026] Based on the excess slip ratio, calculate the difference between the front wheel slip ratio and the difference between the rear wheel slip ratio;

[0027] The driving force correction is calculated based on the difference in front wheel slip ratio and the difference in rear wheel slip ratio.

[0028] Optionally, based on the target driving force, steering angle, and actual wheel speed, the estimated wheel speed for each wheel is calculated, including:

[0029] Based on the goal-driven force, using the formula Calculate the slip ratio for each wheel; where s rf Let s be the slip ratio of the front wheel. rr F represents the slip ratio of the rear wheel. xf For the target driving force of the front axle, F xr K is the target driving force for the rear axle. sf K represents the longitudinal slip stiffness of the front tire. sr The longitudinal slip stiffness of the rear tire;

[0030] Based on slip ratio and actual wheel speed, using the formula, Calculate the vehicle's center of gravity velocity V; where, The average slip ratio. These are the average values ​​of the actual wheel speeds, where ω1 is the actual wheel speed of the right front wheel, ω2 is the actual wheel speed of the left front wheel, ω3 is the actual wheel speed of the right rear wheel, and ω4 is the actual wheel speed of the left rear wheel. t The effective radius of the tire;

[0031] When the steering angle is not equal to 0 degrees, based on the steering angle and the center of gravity speed, using the formula, Calculate the turning radius ρ0 of the center of gravity and the vehicle's lateral slip angle β; where the stability coefficient is... δ is the steering angle of the front wheels, l is the wheelbase, and m is the vehicle weight. Let be the distance between the vehicle's center of gravity and the front axle, and b be the distance between the vehicle's center of gravity and the rear axle. K βf For front wheel cornering ability, K βr For rear wheel cornering ability;

[0032] Based on the center of gravity turning radius and the vehicle's lateral slip angle, using the formula,

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041] Calculate the turning radius and lateral slip angle of each wheel; where ρ1 is the turning radius of the right front wheel, ρ2 is the turning radius of the left front wheel, ρ3 is the turning radius of the right rear wheel, ρ4 is the turning radius of the left rear wheel, β1 is the lateral slip angle of the right front wheel, β2 is the lateral slip angle of the left front wheel, β3 is the lateral slip angle of the right rear wheel, β4 is the lateral slip angle of the left rear wheel, and d f d is the front track width. r This refers to the rear track width;

[0042] Based on the center of gravity velocity, center of gravity turning radius, wheel turning radius, and wheel lateral slip angle, using the formula, Calculate the estimated velocity of each wheel in the direction of its rotation plane; where V1 is the estimated velocity of the right front wheel, V2 is the estimated velocity of the left front wheel, V3 is the estimated velocity of the right rear wheel, and V4 is the estimated velocity of the left rear wheel.

[0043] Based on the estimated velocity and slip ratio, using the formula, Calculate the estimated wheel speed for each wheel; where, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0044] Optionally, based on the slip ratio and actual wheel speed, using the formula, After calculating the vehicle's center of gravity velocity V, the method also includes;

[0045] With a steering angle of 0 degrees, based on the estimated velocity and slip ratio of each wheel in its rotational plane, using the formula, Calculate the estimated wheel speed for each wheel; where, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. V1 is the estimated wheel speed of the left rear wheel, V2 is the estimated speed of the right front wheel, V3 is the estimated speed of the right rear wheel, and V4 is the estimated speed of the left rear wheel, and V1 = V2 = V3 = V4 = V.

[0046] Optionally, if the difference between the estimated wheel speed and the actual wheel speed meets preset conditions, the driving force correction amount is calculated based on the difference between the estimated wheel speed and the actual wheel speed, including:

[0047] If the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions, then based on the difference between the estimated wheel speed and the actual wheel speed, the formula is used. Calculate the excess slip ratio for each wheel; where S e1 S represents the excess slip ratio of the right front wheel. e2 S represents the excess slip ratio of the left front wheel. e3 S represents the excess slip ratio of the right rear wheel. e4 The excess slip ratio of the left rear wheel;

[0048] Based on the excess slip ratio, calculate the difference between the front wheel slip ratio and the difference between the rear wheel slip ratio;

[0049] Based on the difference in front wheel slip ratio and the difference in rear wheel slip ratio, using the formula, ΔFxr =Kc sf |S e1 -S e2 |-Kc sr |S e3 -S e4 |,ΔF xf =-ΔF xr Calculate the driving force correction ΔF of the rear axle. xr and the driving force correction ΔF of the front axle xf Among them, Kc sf =K sf Kc sr =K sr .

[0050] According to a second aspect of the present invention, a drive force control device for a four-wheel drive vehicle is provided, the device comprising:

[0051] The acquisition module is used to acquire the vehicle's target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel;

[0052] The first calculation module is used to calculate the estimated wheel speed of each wheel based on the target driving force, steering angle, and actual wheel speed; wherein, the target driving force includes the target driving force of the front axle and the target driving force of the rear axle;

[0053] The second calculation module is used to calculate the difference between the estimated wheel speed and the actual wheel speed;

[0054] The third calculation module is used to calculate the driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed, provided that the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions; wherein, the driving force correction amount includes the driving force correction amount of the front axle and the driving force correction amount of the rear axle.

[0055] The correction module is used to correct the target driving force based on the driving force correction amount, so as to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset conditions are met.

[0056] Optionally, the first computing module includes:

[0057] The first calculation submodule is used to calculate the slip ratio of each wheel based on the target driving force;

[0058] The second calculation submodule is used to calculate the vehicle's center of gravity speed based on the slip ratio and actual wheel speed;

[0059] The third calculation submodule is used to calculate the turning radius of the center of gravity and the lateral slip angle of the vehicle based on the steering angle and the center of gravity speed when the steering angle is not equal to 0 degrees.

[0060] The fourth calculation submodule is used to calculate the turning radius of each wheel and the lateral slip angle of each wheel based on the turning radius of the center of gravity and the lateral slip angle of the vehicle.

[0061] The fifth calculation submodule is used to calculate the estimated speed of each wheel in its rotational plane direction based on the center of gravity speed, center of gravity turning radius, wheel turning radius, and wheel lateral slip angle.

[0062] The sixth calculation submodule is used to calculate the estimated wheel speed for each wheel based on the estimated speed and slip ratio.

[0063] Optionally, the first computing module may also include;

[0064] The seventh calculation submodule is used to calculate the estimated wheel speed of each wheel based on the estimated speed of each wheel in its rotational plane direction and its slip ratio when the steering angle is equal to 0 degrees; where the estimated speed is equal to the center of gravity speed.

[0065] Optionally, the third computing module includes:

[0066] The eighth calculation submodule is used to calculate the excess slip ratio of each wheel based on the difference between the estimated wheel speed and the actual wheel speed, provided that the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions.

[0067] The ninth calculation submodule is used to calculate the difference between the front wheel slip ratio and the rear wheel slip ratio based on the excess slip ratio;

[0068] The tenth calculation submodule is used to calculate the driving force correction based on the difference between the front wheel slip ratio and the rear wheel slip ratio.

[0069] Optionally, the first computing module includes:

[0070] The first calculation submodule is used to calculate the target driving force using formulas. Calculate the slip ratio for each wheel; where s rf Let s be the slip ratio of the front wheel. rr F represents the slip ratio of the rear wheel. xf For the target driving force of the front axle, F xr For the target driving force of the rear axle, K sf K represents the longitudinal slip stiffness of the front tire. sr The longitudinal slip stiffness of the rear tire;

[0071] The second calculation submodule is used to calculate the value of the slip ratio and the actual wheel speed using a formula. Calculate the vehicle's center of gravity velocity V; where, The average slip ratio. These are the average values ​​of the actual wheel speeds, where ω1 is the actual wheel speed of the right front wheel, ω2 is the actual wheel speed of the left front wheel, ω3 is the actual wheel speed of the right rear wheel, and ω4 is the actual wheel speed of the left rear wheel. t The effective radius of the tire;

[0072] The third calculation submodule is used to calculate the speed based on the steering angle and center of gravity velocity when the steering angle is not equal to 0 degrees, using the formula... Calculate the turning radius ρ0 of the center of gravity and the vehicle's lateral slip angle β; where the stability coefficient is... δ is the steering angle of the front wheels, l is the wheelbase, m is the vehicle weight, a is the distance between the vehicle's center of gravity and the front axle, b is the distance between the vehicle's center of gravity and the rear axle, and K... βf For front wheel cornering ability, K βr For rear wheel cornering ability;

[0073] The fourth calculation submodule is used to calculate the turning radius and lateral slip angle of the vehicle based on the center of gravity, using the formula...

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] Calculate the turning radius and lateral slip angle of each wheel; where ρ1 is the turning radius of the right front wheel, ρ2 is the turning radius of the left front wheel, ρ3 is the turning radius of the right rear wheel, ρ4 is the turning radius of the left rear wheel, β1 is the lateral slip angle of the right front wheel, β2 is the lateral slip angle of the left front wheel, β3 is the lateral slip angle of the right rear wheel, β4 is the lateral slip angle of the left rear wheel, and d f d is the front track width. r This refers to the rear track width;

[0083] The fifth calculation submodule is used to calculate the turning radius of the center of gravity, the turning radius of the wheel, and the lateral slip angle of the wheel using formulas. Calculate the estimated velocity of each wheel in the direction of its rotation plane; where V1 is the estimated velocity of the right front wheel, V2 is the estimated velocity of the left front wheel, V3 is the estimated velocity of the right rear wheel, and V4 is the estimated velocity of the left rear wheel.

[0084] The sixth calculation submodule is used to calculate the estimated velocity and slip ratio using the formula. Calculate the estimated wheel speed for each wheel; where, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0085] Optionally, the first computing module may also include;

[0086] The seventh calculation submodule is used to calculate the estimated speed and slip ratio of each wheel in its rotational plane direction, using the formula, when the steering angle is 0 degrees. Calculate the estimated wheel speed for each wheel; where, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. V1 is the estimated wheel speed of the left rear wheel, V2 is the estimated speed of the right front wheel, V3 is the estimated speed of the right rear wheel, and V4 is the estimated speed of the left rear wheel, and V1 = V2 = V3 = V4 = V.

[0087] Optionally, the third computing module includes:

[0088] The eighth calculation submodule is used to calculate the wheel speed based on the difference between the estimated wheel speed and the actual wheel speed, using a formula, provided that the difference between the estimated wheel speed and the actual wheel speed meets preset conditions. Calculate the excess slip ratio for each wheel; where S e1 S represents the excess slip ratio of the right front wheel. e2 S represents the excess slip ratio of the left front wheel. e3 S represents the excess slip ratio of the right rear wheel. e4 The excess slip ratio of the left rear wheel;

[0089] The ninth calculation submodule is used to calculate the difference between the front wheel slip ratio and the rear wheel slip ratio based on the excess slip ratio;

[0090] The tenth calculation submodule is used to calculate ΔF based on the difference between the front wheel slip ratio and the rear wheel slip ratio using the formula. xr =Kcsf |S e1 -S e2 |-Kc sr |S e3 -S e4 |,ΔF xf =-ΔF xr Calculate the driving force correction ΔF of the rear axle. xr and the driving force correction ΔF of the front axle xf Among them, Kc sf =K sf Kc sr =K sr .

[0091] According to a third aspect of the present invention, an electronic device is provided, comprising: a processor and a memory storing computer program instructions;

[0092] The driving force control method for a four-wheel drive vehicle of the present invention is implemented when the processor executes computer program instructions.

[0093] According to a fourth aspect of the present invention, a computer-readable storage medium is provided, wherein computer program instructions are stored thereon, and when executed by a processor, the computer program instructions implement the driving force control method for a four-wheel drive vehicle of the present invention.

[0094] In summary, due to the response delay between the sudden change in wheel speed caused by wheel slippage and its impact on vehicle motion (such as yaw rate, lateral acceleration, and stability coefficient), existing methods cannot respond quickly to vehicle slippage conditions. This invention provides a driving force control method for four-wheel drive vehicles. The vehicle can pre-calculate the estimated wheel speed by acquiring the target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel. When the difference between the estimated and actual wheel speeds exceeds a preset value, the target driving force can be corrected based on this difference to ensure the difference is below the preset value, thus improving vehicle handling stability. Because this invention corrects the target driving force controlling wheel speed by pre-calculating the estimated wheel speeds, it can respond quickly to conditions such as sudden changes in road friction coefficients, improving the vehicle's straight-line performance and handling stability. Attached Figure Description

[0095] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0096] Figure 1 A flowchart illustrating a driving force control method for a four-wheel drive vehicle provided in an embodiment of the present invention;

[0097] Figure 2 A schematic diagram of the relationship between target driving force and slip ratio;

[0098] Figure 3 This is a schematic diagram showing the overall tire speed relative to the tire's rotational surface.

[0099] Figure 4 This is a schematic diagram showing the turning radius and lateral slip angle at each tire position;

[0100] Figure 5 This is a schematic diagram showing the change of the road surface friction coefficient μ over time.

[0101] Figure 6(a) is a schematic diagram of the change of target driving force of the front and rear axles over time when the vehicle is traveling straight and there is no invention;

[0102] Figure 6(b) is a schematic diagram showing the change of front-to-back acceleration over time when the vehicle is traveling straight and there is no invention.

[0103] Figure 7(a) is a schematic diagram showing the change of yaw rate over time when the vehicle is traveling straight and there is no invention.

[0104] Figure 7(b) is a schematic diagram showing the change of wheel speed over time when the vehicle is traveling straight and there is no invention.

[0105] Figure 8(a) is a schematic diagram showing the change of target driving force of the front and rear axles over time when the vehicle is traveling straight and there is an invention.

[0106] Figure 8(b) is a schematic diagram showing the change of front-to-back acceleration over time when the vehicle is traveling straight and there is an invention.

[0107] Figure 9(a) is a schematic diagram showing the change of yaw rate over time when the vehicle is traveling straight and there is an invention.

[0108] Figure 9(b) is a schematic diagram showing the change of wheel speed over time when the vehicle is traveling straight and there is an invention.

[0109] Figure 10(a) is a schematic diagram showing the change of front-to-back acceleration over time when the vehicle is turning and there is no invention.

[0110] Figure 10(b) is a schematic diagram showing the change of yaw rate over time when the vehicle is turning and there is no invention.

[0111] Figure 10(c) is a schematic diagram showing the change of wheel speed over time when the vehicle is turning and there is no invention.

[0112] Figure 11(a) is a schematic diagram showing the change of front-to-back acceleration over time when the vehicle is turning and there is an invention.

[0113] Figure 11(b) is a schematic diagram showing the change of yaw rate over time when the vehicle is turning and there is an invention.

[0114] Figure 11(c) is a schematic diagram showing the change of wheel speed over time when the vehicle is turning and there is an invention.

[0115] Figure 12 A structural diagram of a drive force control device for a four-wheel drive vehicle provided in an embodiment of the present invention;

[0116] Figure 13 This is a structural diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0117] To make the above and other features and advantages of the present invention clearer, the invention will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art and are exemplary only, not restrictive.

[0118] In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the specific details are not required to practice the invention. In other instances, well-known steps or operations have not been described in detail to avoid obscuring the invention.

[0119] To address the issue of slow response times in existing solutions when vehicles experience sudden changes in road surface friction coefficient during operation, this invention provides a driving force control method for four-wheel drive vehicles to respond quickly to such conditions. For example... Figure 1 As shown, the method includes:

[0120] S110, acquire the target driving force of the vehicle, the steering angle of the front wheels, and the actual wheel speed of each wheel; wherein, the target driving force includes the target driving force of the front axle and the target driving force of the rear axle.

[0121] The executing entity of this invention can be a vehicle controller or a power domain controller, etc. First, it obtains the target driving force of the vehicle, including the target driving force F of the front axle. xf and the target driving force F of the rear axle xr Obtain the steering angle δ of the front wheel and the actual wheel speed ω1, ω2, ω3, ω4 of each wheel; where the steering angle of the front wheel can be equal to 0 degrees or not equal to 0 degrees, and the numbers represent 1 for right front, 2 for left front, 3 for right rear, and 4 for left rear respectively.

[0122] S120 calculates the estimated wheel speed for each wheel based on the target driving force, steering angle, and actual wheel speed.

[0123] like Figure 2The figure shows the relationship between slip ratio, target driving force, and longitudinal slip stiffness. As can be seen from the figure, after obtaining the vehicle's target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel, the target driving force can be used to calculate the slip ratio using the following formula: Calculate the slip ratio of each wheel; where s rf Let s be the slip ratio of the front wheel. rr K represents the slip ratio of the rear wheel. sf K represents the longitudinal slip stiffness of the front tire. sr The longitudinal slip stiffness of the rear tire is given. The longitudinal slip stiffness of the front tire and the longitudinal slip stiffness of the rear tire can be calculated from the vehicle parameters.

[0124] It should be noted that, for ease of explanation, it is assumed here that the target driving force of the left and right wheels is the same, denoted as (F). xf / 2) represents the target driving force of the previous round, with (F xr / 2) represents the target driving force of the rear wheel. Specifically, since this invention only requires the four wheels to have a relative slip relationship to achieve its effect, it is not necessary to calculate the slip ratio with high precision. Therefore, the method of this invention is also applicable to situations where the target driving forces of the left and right wheels are different.

[0125] Furthermore, such as Figure 3 As shown, according to the definition of slip ratio, i.e. slip ratio Where u is the overall speed of the tire about the surface of rotation, ω is the wheel speed, and l is the speed of the tire. t Let be the effective radius of the tire, and thus, we can use the formula... Calculate the vehicle's center of gravity speed. Since this invention does not require high-precision calculation of the slip ratio, the u in the definition of slip ratio can be equivalent to the center of gravity velocity V, and the effective radius of the tire, i.e. the dynamic load radius, can be equivalent to the radius of the tire used. Specifically, it can be calculated based on the number of wheel rotations and the wheel rolling distance. The average slip ratio. ω1 represents the average actual wheel speed, ω2 represents the actual wheel speed of the right front wheel, ω3 represents the actual wheel speed of the right rear wheel, and ω4 represents the actual wheel speed of the left rear wheel.

[0126] When the steering angle δ of the front wheels is not equal to 0 degrees, based on the steering angle δ and the center of gravity velocity V, using the formula, The turning radius ρ0 of the center of gravity and the lateral slip angle β of the vehicle can be calculated; where, the stability coefficient l is the wheelbase, m is the vehicle weight, a is the distance between the vehicle's center of gravity and the front axle, b is the distance between the vehicle's center of gravity and the rear axle, and K is the weight of the vehicle. βf For front wheel cornering ability, Kβr This refers to the rear wheel's cornering ability.

[0127] It should be noted that the front wheel cornering ability K βf and rear wheel cornering ability K βr All of these parameters can be obtained in advance using existing methods. Below is a method for calculating the front wheel cornering capability K. βf and rear wheel cornering ability K βr The method described below should be understood as merely an example and should not be construed as a limitation of the invention. Specifically, firstly, the steering angle and lateral acceleration of an actual vehicle during a stable circular turn at a certain speed are measured (Measurement 1); then, the lateral acceleration during a stable circular turn after changing the steering angle is measured (Measurement 2); substituting the vehicle speed, steering angle, and lateral acceleration from Measurement 1 and Measurement 2 into the relationship between the steering angle and lateral acceleration during a fixed-circle turn obtained from a two-wheel model of the vehicle, two simultaneous equations are obtained, from which the two unknowns, the forward and backward turning capabilities (K), can be calculated. βf K βr (Other vehicle parameters are known). The steering angle delta (δ) obtained from the two-wheel model of the vehicle during a fixed-circle turn. k ) and lateral acceleration a y The relationship is shown in the calculation formula below.

[0128]

[0129] Among them, the stability coefficient v: vehicle speed (m / s), l: wheelbase (m), m: vehicle weight (kg), a: distance between the front axle and the center of gravity (m), b: distance between the rear axle and the center of gravity (m).

[0130] like Figure 4 As shown, after calculating the center of gravity turning radius ρ0 and the vehicle lateral slip angle β, the following formula can be used:

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] The turning radius and lateral slip angle of each wheel are calculated; where ρ1 is the turning radius of the right front wheel, ρ2 is the turning radius of the left front wheel, ρ3 is the turning radius of the right rear wheel, ρ4 is the turning radius of the left rear wheel, β1 is the lateral slip angle of the right front wheel, β2 is the lateral slip angle of the left front wheel, β3 is the lateral slip angle of the right rear wheel, β4 is the lateral slip angle of the left rear wheel, and d f d is the front track width. r This refers to the rear track width.

[0140] Furthermore, based on the calculated center of gravity velocity, center of gravity turning radius, wheel turning radius, and wheel lateral slip angle, the formula can be used... The estimated velocity of each wheel in its rotational plane direction is calculated; where V1 is the estimated velocity of the right front wheel, V2 is the estimated velocity of the left front wheel, V3 is the estimated velocity of the right rear wheel, and V4 is the estimated velocity of the left rear wheel.

[0141] Therefore, based on the estimated speed and slip ratio of each wheel, and according to the definition of slip ratio, The estimated wheel speed of each wheel can be calculated. in, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0142] Furthermore, when the steering angle of the front wheels is 0 degrees, since V1 = V2 = V3 = V4 = V, where V1 is the estimated speed of the right front wheel, V2 is the estimated speed of the left front wheel, V3 is the estimated speed of the right rear wheel, and V4 is the estimated speed of the left rear wheel, based on the steering angle δ and the center of gravity velocity V, and according to the definition of slip ratio, The estimated wheel speed of each wheel can be calculated. in, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0143] S130, calculate the difference between the estimated wheel speed and the actual wheel speed.

[0144] After obtaining the estimated wheel speed for each wheel, the difference between the estimated wheel speed and the actual wheel speed is calculated. The wheel's motion state is predicted by using the difference between the estimated and actual wheel speeds. It should be noted that since the estimated wheel speed is obtained from the wheel slippage caused by the target driving force and the overall motion state of the vehicle, and the vehicle can acquire and adjust the target driving force in real time, it can quickly respond to working conditions such as sudden changes in the road friction coefficient by correcting the target driving force.

[0145] S140, if the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions, calculate the driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed; the driving force correction amount includes the driving force correction amount of the front axle and the driving force correction amount of the rear axle.

[0146] Specifically, assuming the difference between the estimated wheel speed and the actual wheel speed meets preset conditions, the excess slip ratio of each wheel is calculated based on this difference. Among them, S e1 S represents the excess slip ratio of the right front wheel. e2 S represents the excess slip ratio of the left front wheel. e3 S represents the excess slip ratio of the right rear wheel. e4 The excess slip ratio of the left rear wheel is given; then the difference in slip ratios between the two front wheels and the two rear wheels is calculated. Based on the difference in slip ratios between the two front wheels and the two rear wheels, the driving force correction ΔF of the rear axle is calculated. xr =Kc sf |S e1 -S e2 |-Kc sr |S e3 -S e4 | and the driving force correction ΔF of the front axle. xr =-ΔF xr Among them, Kc sf =K sf Kc sr =K sr .

[0147] K sf and K sr To control the gain, it can be understood that the target driving force lost due to excessive slip ratio is calculated using the longitudinal slip stiffness of the tire, and the lost portion is corrected. Since the longitudinal slip stiffness also changes with the road friction coefficient and vertical load, the control gain can also be selected from front-to-back acceleration, lateral acceleration, and yaw rate, etc.

[0148] In addition, since the absolute estimation accuracy of the excess slip ratio is not high (the estimation accuracy of the wheel speed itself is not high), differential calculation is used to improve the accuracy of calculating the driving force correction through the excess slip ratio.

[0149] It should be noted that the method of the present invention is applicable when the sum of the target driving force of the front axle and the target driving force of the rear axle remains unchanged. Therefore, the driving force correction amount ΔF of the front axle is... xr =-ΔF xr .

[0150] S150, based on the driving force correction amount, corrects the target driving force to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset conditions are met.

[0151] After calculating the driving force correction for the front and rear axles, the corrected target driving force Fc for the front axle is obtained. xf =F xf +ΔF xf The corrected target driving force Fc of the rear axle xr =F xr +ΔF xr .

[0152] Because of Kc sf The difference in excess slip ratio between the left and right sides of the front wheels has an impact. When the difference in excess slip ratio between the left and right sides of the front wheels is large, the target driving force correction amount ΔF of the rear axle will be larger. xr The value increases to a positive value, which is the correction amount ΔF for the driving force of the front axle. xf =(-ΔF) xr The target driving force of the front axle decreases, while the target driving force of the rear axle increases, in order to reduce the impact of slippage on the vehicle's motion state and improve the vehicle's handling stability.

[0153] Conversely, when the difference in slip ratio between the left and right sides of the rear wheel is large (larger slip on the rear wheel side), the target driving force of the front axle increases and the target driving force of the rear axle decreases, in order to reduce the impact of slip on the vehicle's motion state and improve the vehicle's handling stability.

[0154] In summary, in the method of this invention, the vehicle can pre-calculate the estimated wheel speed by acquiring the target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel. When the difference between the estimated wheel speed and the actual wheel speed exceeds a preset value, the target driving force can be corrected based on the difference between the estimated and actual wheel speeds, so that the difference between the actual and estimated wheel speeds is lower than the preset value, thereby improving vehicle handling stability. Since the method of this invention corrects the target driving force controlling the wheel speed by pre-calculating the estimated wheel speed, it can respond quickly to conditions such as sudden changes in road friction coefficient, thereby improving the vehicle's straight-line performance and handling stability. Furthermore, since the estimated wheel speed in the method of this invention is estimated from the wheel slippage and overall vehicle motion state caused by the target driving force, and the vehicle can acquire and adjust the target driving force in real time, the feasibility of the method of this invention is further improved.

[0155] The target driving force includes the target driving force of the front axle and the target driving force of the rear axle; the difference between the estimated wheel speed and the actual wheel speed is calculated; the driving force correction includes the driving force correction for the front axle and the driving force correction for the rear axle; based on the driving force correction,

[0156] To further illustrate the beneficial effects of the present invention, specific examples are provided below.

[0157] Example 1: Only the right rear wheel's road friction coefficient μ decreases (straight driving)

[0158] The road surface friction coefficient μ = 0.3.

[0159] The total target driving force Fx = 4000N, and the driving force distribution ratio is front:rear = 50:50;

[0160] The steering angle of the front wheels δ = 0 degrees;

[0161] Travel in a straight line with an initial speed of 60 km / h.

[0162] like Figure 5 As shown in Figure 6(a), only the road friction coefficient μ of the right rear wheel changes (from 0.3 to 0.2, and then back to 0.3); Figure 6(b) , 7(a) As shown in Figure 7(b), when the driving force control method of the present invention is not present (hereinafter referred to as "without invention"), the front and rear acceleration, yaw rate and wheel speed of each wheel change significantly; as shown in Figure 8(a). Figure 8(b) , 9(a) As shown in 9(b), when the driving force control method of the present invention is available (hereinafter referred to as having the invention), after the road surface μ decreases, the target driving force of the rear axle decreases, and the target driving force of the front axle increases accordingly, thereby suppressing the changes in front and rear acceleration, yaw rate and wheel speed of each wheel.

[0163] Example 2: Road surface μ drops only on the right rear wheel (turning)

[0164] Road surface μ = 0.3;

[0165] The total target driving force Fx = 4000N, and the driving force distribution ratio is front:rear = 50:50;

[0166] Front wheel steering angle δ = 1 degree;

[0167] Travel in a straight line with an initial speed of 60 km / h.

[0168] like Figure 5 As shown, when only the road surface μ of the right rear wheel changes (from 0.3 to 0.2, and then back to 0.3); as shown in Figures 10(a), 10(b), and 10(c), without the invention, the yaw rate and the wheel speed of each wheel change significantly, resulting in a slipping state, while in Figures 11(a), 11(b), and 11(c), with the invention, the changes are suppressed.

[0169] The present invention also provides a drive force control device for a four-wheel drive vehicle, such as... Figure 12 As shown, the device includes:

[0170] The acquisition module 1201 is used to acquire the target driving force of the vehicle, the steering angle of the front wheels, and the actual wheel speed of each wheel; wherein, the target driving force includes the target driving force of the front axle and the target driving force of the rear axle.

[0171] The executing entity of this invention can be a vehicle controller or a power domain controller, etc. First, it obtains the target driving force of the vehicle, including the target driving force F of the front axle. xf and the target driving force F of the rear axle xr Obtain the steering angle δ of the front wheel and the actual wheel speed ω1, ω2, ω3, ω4 of each wheel; where the steering angle of the front wheel can be equal to 0 degrees or not equal to 0 degrees, and the numbers represent 1 for right front, 2 for left front, 3 for right rear, and 4 for left rear respectively.

[0172] The first calculation module 1202 is used to calculate the estimated wheel speed of each wheel based on the target driving force, steering angle and actual wheel speed.

[0173] like Figure 2 The figure shows the relationship between slip ratio, target driving force, and longitudinal slip stiffness. As can be seen from the figure, after obtaining the vehicle's target driving force, the steering angle of the front wheels, and the actual wheel speed of each wheel, the target driving force can be used to calculate the slip ratio using the following formula: Calculate the slip ratio of each wheel; where s rf Let s be the slip ratio of the front wheel. rrK represents the slip ratio of the rear wheel. sf K represents the longitudinal slip stiffness of the front tire. sr The longitudinal slip stiffness of the rear tire is given. The longitudinal slip stiffness of the front tire and the longitudinal slip stiffness of the rear tire can be calculated from the vehicle parameters.

[0174] It should be noted that, for ease of explanation, it is assumed here that the target driving force of the left and right wheels is the same, denoted as (F). xf / 2) represents the target driving force of the previous round, with (F xr / 2) represents the target driving force of the rear wheel. Specifically, since this invention only requires the four wheels to have a relative slip relationship to achieve its effect, it is not necessary to calculate the slip ratio with high precision. Therefore, the method of this invention is also applicable to situations where the target driving forces of the left and right wheels are different.

[0175] Furthermore, such as Figure 3 As shown, according to the definition of slip ratio, i.e. slip ratio Where u is the overall speed of the tire about the surface of rotation, ω is the wheel speed, and l is the speed of the tire. t Let be the effective radius of the tire, and thus, we can use the formula... Calculate the vehicle's center of gravity speed. Since this invention does not require a high-precision calculation of the slip ratio, the u in the definition of the slip ratio can be equivalent to the center of gravity velocity V. The average slip ratio. ω1 represents the average actual wheel speed, ω2 represents the actual wheel speed of the right front wheel, ω3 represents the actual wheel speed of the right rear wheel, and ω4 represents the actual wheel speed of the left rear wheel.

[0176] When the steering angle δ of the front wheels is not equal to 0 degrees, based on the steering angle δ and the center of gravity velocity V, using the formula, The turning radius ρ0 of the center of gravity and the lateral slip angle β of the vehicle can be calculated; where, the stability coefficient l is the wheelbase, m is the vehicle weight, a is the distance between the vehicle's center of gravity and the front axle, b is the distance between the vehicle's center of gravity and the rear axle, and K is the weight of the vehicle. βf For front wheel cornering ability, K βr This refers to the rear wheel's cornering ability.

[0177] like Figure 4 As shown, after calculating the center of gravity turning radius ρ0 and the vehicle lateral slip angle β, the following formula can be used:

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186] The turning radius and lateral slip angle of each wheel are calculated; where ρ1 is the turning radius of the right front wheel, ρ2 is the turning radius of the left front wheel, ρ3 is the turning radius of the right rear wheel, ρ4 is the turning radius of the left rear wheel, β1 is the lateral slip angle of the right front wheel, β2 is the lateral slip angle of the left front wheel, β3 is the lateral slip angle of the right rear wheel, β4 is the lateral slip angle of the left rear wheel, and d f d is the front track width. r This refers to the rear track width.

[0187] Furthermore, based on the calculated center of gravity velocity, center of gravity turning radius, wheel turning radius, and wheel lateral slip angle, the formula can be used... The estimated velocity of each wheel in its rotational plane direction is calculated; where V1 is the estimated velocity of the right front wheel, V2 is the estimated velocity of the left front wheel, V3 is the estimated velocity of the right rear wheel, and V4 is the estimated velocity of the left rear wheel.

[0188] Therefore, based on the estimated speed and slip ratio of each wheel, and according to the definition of slip ratio, The estimated wheel speed of each wheel can be calculated. in, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0189] Furthermore, when the steering angle of the front wheels is 0 degrees, since V1 = V2 = V3 = V4 = V, where V1 is the estimated speed of the right front wheel, V2 is the estimated speed of the left front wheel, V3 is the estimated speed of the right rear wheel, and V4 is the estimated speed of the left rear wheel, based on the steering angle δ and the center of gravity velocity V, and according to the definition of slip ratio, The estimated wheel speed of each wheel can be calculated. in, The estimated wheel speed of the right front wheel. For the estimated wheel speed of the left front wheel, The estimated wheel speed for the right rear wheel. This is the estimated wheel speed of the left rear wheel.

[0190] The second calculation module 1203 is used to calculate the difference between the estimated wheel speed and the actual wheel speed.

[0191] After obtaining the estimated wheel speed for each wheel, the difference between the estimated wheel speed and the actual wheel speed is calculated. The wheel's motion state is predicted by using the difference between the estimated and actual wheel speeds. It should be noted that since the estimated wheel speed is obtained from the wheel slippage caused by the target driving force and the overall motion state of the vehicle, and the vehicle can acquire and adjust the target driving force in real time, it can quickly respond to working conditions such as sudden changes in the road friction coefficient by correcting the target driving force.

[0192] The third calculation module 1204 is used to calculate the driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed, provided that the difference between the estimated wheel speed and the actual wheel speed meets the preset conditions. The driving force correction amount includes the driving force correction amount of the front axle and the driving force correction amount of the rear axle.

[0193] Specifically, assuming the difference between the estimated wheel speed and the actual wheel speed meets preset conditions, the excess slip ratio of each wheel is calculated based on this difference. Among them, S e1 S represents the excess slip ratio of the right front wheel. e2 S represents the excess slip ratio of the left front wheel. e3 S represents the excess slip ratio of the right rear wheel. e4 The excess slip ratio of the left rear wheel is given; then the difference in slip ratios between the two front wheels and the two rear wheels is calculated. Based on the difference in slip ratios between the two front wheels and the two rear wheels, the driving force correction ΔF of the rear axle is calculated. xr =Kc sf |S e1 -S e2 |-Kc sr |S e3 -S e4 | and the driving force correction ΔF of the front axle. xr =-ΔF xr Among them, Kc sf =K sf Kc sr =K sr .

[0194] K sf and Ksr To control the gain, it can be understood that the target driving force lost due to excessive slip ratio is calculated using the longitudinal slip stiffness of the tire, and the lost portion is corrected. Since the longitudinal slip stiffness also changes with the road friction coefficient and vertical load, the control gain can also be selected from front-to-back acceleration, lateral acceleration, and yaw rate, etc.

[0195] In addition, since the absolute estimation accuracy of the excess slip ratio is not high (the estimation accuracy of the wheel speed itself is not high), differential calculation is used to improve the accuracy of calculating the driving force correction through the excess slip ratio.

[0196] It should be noted that the method of the present invention is applicable when the sum of the target driving force of the front axle and the target driving force of the rear axle remains unchanged. Therefore, the driving force correction amount ΔF of the front axle is... xr =-ΔF xr .

[0197] The correction module 1205 is used to correct the target driving force based on the driving force correction amount, so as to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset conditions are met.

[0198] After calculating the driving force correction for the front and rear axles, the corrected target driving force Fc for the front axle is obtained. xf =F xf +ΔF xf The corrected target driving force Fc of the rear axle xr =F xr +ΔF xr .

[0199] Because of Kc sf The difference in excess slip ratio between the left and right sides of the front wheels has an impact. When the difference in excess slip ratio between the left and right sides of the front wheels is large, the target driving force correction amount ΔF of the rear axle will be larger. xr The value increases to a positive value, which is the correction amount ΔF for the driving force of the front axle. xf =(-ΔF) xr The target driving force of the front axle decreases, while the target driving force of the rear axle increases, in order to reduce the impact of slippage on the vehicle's motion state and improve the vehicle's handling stability.

[0200] Conversely, when the difference in slip ratio between the left and right sides of the rear wheel is large (larger slip on the rear wheel side), the target driving force of the front axle increases and the target driving force of the rear axle decreases, in order to reduce the impact of slip on the vehicle's motion state and improve the vehicle's handling stability.

[0201] The present invention also provides an electronic device, such as... Figure 13 As shown, the electronic device includes: a processor 1302 and a memory 1301 storing computer program instructions;

[0202] The processor 1302 implements the driving force control method for a four-wheel drive vehicle of the present invention when executing computer program instructions.

[0203] The present invention also provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer program instructions, which, when executed by a processor, implement the driving force control method for a four-wheel drive vehicle of the present invention.

[0204] It should be understood that the specific features, operations, and details described above regarding the method of the present invention can also be similarly applied to the apparatus and system of the present invention, or vice versa. Furthermore, each step of the method of the present invention described above can be performed by a corresponding component or unit of the apparatus or system of the present invention.

[0205] It should be understood that the various modules / units of the apparatus of the present invention can be implemented wholly or partially through software, hardware, firmware, or a combination thereof. Each module / unit can be embedded in the processor of a computer device in hardware or firmware form, or independent of the processor, or stored in the memory of the computer device in software form for the processor to call to execute the operation of each module / unit. Each module / unit can be implemented as an independent component or module, or two or more modules / units can be implemented as a single component or module. In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores computer instructions executable by the processor, which, when executed by the processor, instruct the processor to perform the steps of the methods of embodiments of the present invention. The computer device can be broadly defined as a server, a terminal, or any other electronic device with the necessary computing and / or processing capabilities. In one embodiment, the computer device may include a processor, memory, network interface, communication interface, etc., connected via a system bus. The processor of the computer device can be used to provide the necessary computing, processing, and / or control capabilities. The memory of the computer device may include a non-volatile storage medium and internal memory. The non-volatile storage medium may store an operating system, computer programs, etc. The internal memory provides an environment for the operation of an operating system and computer programs stored in a non-volatile storage medium. The network interface and communication interface of the computer device can be used to connect and communicate with external devices via a network. When the computer program is executed by the processor, it performs the steps of the method of the present invention.

[0206] This invention can be implemented as a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, causes the steps of the methods of embodiments of the invention to be performed. In one embodiment, the computer program is distributed across multiple network-coupled computer devices or processors, such that the computer program is stored, accessed, and executed in a distributed manner by one or more computer devices or processors. A single method step / operation, or two or more method steps / operations, may be executed by a single computer device or processor or by two or more computer devices or processors. One or more method steps / operations may be executed by one or more computer devices or processors, and one or more other method steps / operations may be executed by one or more other computer devices or processors. One or more computer devices or processors may execute a single method step / operation, or execute two or more method steps / operations.

[0207] Those skilled in the art will understand that the method steps of this invention can be performed by a computer program instructing related hardware, such as a computer device or processor. The computer program can be stored in a non-transitory computer-readable storage medium, and its execution causes the steps of this invention to be performed. Depending on the context, any references herein to memory, storage, databases, or other media may include non-volatile and / or volatile memory. Examples of non-volatile memory include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, magnetic tape, floppy disk, magneto-optical data storage device, optical data storage device, hard disk, solid-state drive, etc. Examples of volatile memory include random access memory (RAM), external cache memory, etc.

[0208] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drive force control method for a four-wheel drive vehicle, characterized by, The method comprises: acquiring a target driving force of a vehicle, a steering angle of a front wheel, and an actual wheel speed of each wheel; wherein the target driving force comprises a target driving force of a front axle and a target driving force of a rear axle; calculating an estimated wheel speed of each wheel based on the target driving force, the steering angle, and the actual wheel speed; calculating a difference between the estimated wheel speed and the actual wheel speed; in a case where the difference between the estimated wheel speed and the actual wheel speed meets a preset condition, calculating a driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed; wherein the driving force correction amount comprises a driving force correction amount of the front axle and a driving force correction amount of the rear axle; correcting the target driving force based on the driving force correction amount to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset condition is met; wherein the calculating an estimated wheel speed of each wheel based on the target driving force, the steering angle, and the actual wheel speed comprises: calculating a slip ratio of each wheel based on the target driving force; calculating a center of gravity speed of the vehicle based on the slip ratio and the actual wheel speed; in a case where the steering angle is not equal to 0 degree, calculating a center of gravity turning radius and a vehicle lateral slip angle based on the steering angle and the center of gravity speed; calculating a wheel turning radius of each wheel and a wheel lateral slip angle of each wheel based on the center of gravity turning radius and the vehicle lateral slip angle; calculating an estimated speed of each wheel in a direction of a rotation plane of each wheel based on the center of gravity speed, the center of gravity turning radius, the wheel turning radius, and the wheel lateral slip angle; calculating an estimated wheel speed of each wheel based on the estimated speed and the slip ratio; wherein the calculating a driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed in a case where the difference between the estimated wheel speed and the actual wheel speed meets a preset condition comprises: calculating an excess slip ratio of each wheel based on the difference between the estimated wheel speed and the actual wheel speed in a case where the difference between the estimated wheel speed and the actual wheel speed meets a preset condition; calculating a difference between front wheel slip ratios and a difference between rear wheel slip ratios based on the excess slip ratio; calculating a driving force correction amount based on the difference between front wheel slip ratios and the difference between rear wheel slip ratios.

2. The drive force control method of a four-wheel drive vehicle according to claim 1, characterized by, After the calculating a center of gravity speed of the vehicle based on the slip ratio and the actual wheel speed, the method further comprises: in a case where the steering angle is equal to 0 degree, calculating an estimated wheel speed of each wheel based on an estimated speed of each wheel in a direction of a rotation plane of each wheel and a slip ratio of each wheel; wherein the estimated speed is equal to the center of gravity speed.

3. The drive force control method of a four-wheel drive vehicle according to claim 1, characterized by, The calculating an estimated wheel speed of each wheel based on the target driving force, the steering angle, and the actual wheel speed comprises: Based on the target driving force, the slip ratio of each wheel is calculated using the formula, , wherein, is the slip ratio of the front wheels, is the slip ratio of the rear wheels, is the target driving force of the front axle, is the target driving force of the rear axle, is the longitudinal slip stiffness of the front wheels, is the longitudinal slip stiffness of the rear wheels; Based on the slip ratio and the actual wheel speed, the center of gravity speed of the vehicle is calculated using the formula , , ; wherein is the average value of the slip ratio, is the average value of the actual wheel speed, is the actual wheel speed of the right front wheel, is the actual wheel speed of the left front wheel, is the actual wheel speed of the right rear wheel, is the actual wheel speed of the left rear wheel, is the effective radius of the tire;​ In the case that the steering angle is not equal to 0 degree, based on the steering angle and the gravity center speed, the formula is used to calculate the gravity center turning radius , the vehicle lateral slip angle and the stability coefficient ; wherein the stability coefficient , is the steering angle, is the wheelbase, is the vehicle weight, is the distance between the gravity center of the vehicle and the front axle, is the distance between the gravity center of the vehicle and the rear axle, is the front wheel turning ability, is the rear wheel turning ability. based on the center of gravity turning radius and the vehicle sideslip angle, utilizing a formula, calculating a wheel turning radius for each wheel and a wheel sideslip angle for each wheel; wherein, is the wheel turning radius for the right front wheel, is the wheel turning radius for the left front wheel, is the wheel turning radius for the right rear wheel, is the wheel turning radius for the left rear wheel, is the wheel sideslip angle for the right front wheel, is the wheel sideslip angle for the left front wheel, is the wheel sideslip angle for the right rear wheel, is the wheel sideslip angle for the left rear wheel, is the front track, is the rear track; Based on the center of gravity velocity, the center of gravity turning radius, the wheel turning radius, and the wheel sideslip angle, an estimated velocity of each wheel in a direction of a plane of rotation of the wheel is calculated using the formula, , , , wherein, Vx is the estimated velocity of the right front wheel, Vx is the estimated velocity of the left front wheel, Vx is the estimated velocity of the right rear wheel, Vx is the estimated velocity of the left rear wheel. Based on the estimated speed and the slip ratio, the estimated wheel speed of each wheel is calculated using the formula, , , , wherein is the estimated wheel speed of the right front wheel, is the estimated wheel speed of the left front wheel, is the estimated wheel speed of the right rear wheel, is the estimated wheel speed of the left rear wheel.

4. The drive force control method of a four-wheel drive vehicle according to claim 3, characterized by calculating a center of gravity speed of the vehicle using a formula based on the slip ratio and the actual wheel speed , , after which the method further comprises;​ In the case where the steering angle is equal to 0 degree, the estimated wheel speed of each wheel is calculated based on the estimated speed of each wheel in the direction of the rotation plane thereof and the slip ratio thereof, using the formula, , , , wherein is the estimated wheel speed of the right front wheel, is the estimated wheel speed of the left front wheel, is the estimated wheel speed of the right rear wheel, is the estimated wheel speed of the left rear wheel, is the estimated speed of the right front wheel, is the estimated speed of the left front wheel, is the estimated speed of the right rear wheel, is the estimated speed of the left rear wheel, and .

5. The drive force control method of a four-wheel drive vehicle according to claim 3 or 4, characterized by, The calculating a driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed in a case where the difference between the estimated wheel speed and the actual wheel speed meets a preset condition comprises: In the case where the difference between the estimated wheel speed and the actual wheel speed satisfies a preset condition, the excess slip rate of each wheel is calculated based on the difference between the estimated wheel speed and the actual wheel speed by using a formula, , , , , wherein, is the excess slip rate of the right front wheel, is the excess slip rate of the left front wheel, is the excess slip rate of the right rear wheel, is the excess slip rate of the left rear wheel. calculating a difference between front wheel slip ratios and a difference between rear wheel slip ratios based on the excess slip ratio; Based on the difference between the front wheel slip ratio and the difference between the rear wheel slip ratio, using the formula, , = , the drive force correction amount of the rear axle and the drive force correction amount of the front axle ; wherein, , .

6. A driving force control device of a four-wheel drive vehicle, characterized by comprising: The apparatus comprises: The acquisition module is configured to acquire a target driving force of the vehicle, a steering angle of a front wheel, and actual wheel speeds of each wheel, wherein the target driving force includes a target driving force of a front axle and a target driving force of a rear axle. The first calculation module is configured to calculate an estimated wheel speed of each wheel based on the target driving force, the steering angle, and the actual wheel speeds. The second calculation module is configured to calculate a difference between the estimated wheel speed and the actual wheel speed. The third calculation module is configured to calculate a driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed, when the difference between the estimated wheel speed and the actual wheel speed meets a preset condition, wherein the driving force correction amount includes a driving force correction amount of the front axle and a driving force correction amount of the rear axle. The correction module is configured to correct the target driving force based on the driving force correction amount, so as to reduce the difference between the actual wheel speed and the estimated wheel speed until the preset condition is met. The calculation of the estimated wheel speed of each wheel based on the target driving force, the steering angle, and the actual wheel speeds includes: calculating a slip ratio of each wheel based on the target driving force; calculating a center of gravity speed of the vehicle based on the slip ratio and the actual wheel speeds; calculating a center of gravity turning radius and a vehicle lateral slip angle based on the steering angle and the center of gravity speed, when the steering angle is not equal to 0 degree; calculating a wheel turning radius of each wheel and a wheel lateral slip angle of each wheel based on the center of gravity turning radius and the vehicle lateral slip angle; calculating an estimated speed of each wheel in a direction of a rotation plane of each wheel based on the center of gravity speed, the center of gravity turning radius, the wheel turning radius, and the wheel lateral slip angle; calculating the estimated wheel speed of each wheel based on the estimated speed and the slip ratio. The calculation of the driving force correction amount based on the difference between the estimated wheel speed and the actual wheel speed, when the difference between the estimated wheel speed and the actual wheel speed meets the preset condition, includes: calculating an excess slip ratio of each wheel based on the difference between the estimated wheel speed and the actual wheel speed, when the difference between the estimated wheel speed and the actual wheel speed meets the preset condition; calculating a difference between front wheel slip ratios and a difference between rear wheel slip ratios based on the excess slip ratio; calculating the driving force correction amount based on the difference between the front wheel slip ratios and the difference between the rear wheel slip ratios.

7. An electronic device, comprising: The electronic device includes a processor and a memory storing computer program instructions; The processor executes the computer program instructions to implement the driving force control method of the four-wheel drive vehicle according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer program instructions, and the computer program instructions are executed by a processor to implement the driving force control method of the four-wheel drive vehicle according to any one of claims 1-5.

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