Four-wheel drive vehicle yaw stability control method and four-wheel drive vehicle

Abstract

The present invention discloses a yaw stability control method for a four-wheel drive vehicle and a four-wheel drive vehicle. The method comprises: calculating a unilaterally required additional yaw torque; calculating a left and right wheel torque change direction flag; calculating the remaining available torque of each motor and each brake caliper; calculating the maximum additional yaw torque generated by the remaining available torque of each left and right motor and brake caliper; calculating a selection coefficient; calculating the maximum remaining available torque that can be executed by each motor and each brake caliper; calculating the maximum additional yaw torque superimposed on the same side; calculating a scaling coefficient of the remaining available torque of each motor and each brake caliper; calculating the torque increase or decrease executed by each motor and each brake caliper; and calculating the target torque ultimately output by each motor and each brake caliper. During the yaw stability control process, the present invention ensures that the brake caliper and wheel hub motor both operate within their capabilities to avoid the risk of damage; the brake caliper and wheel hub motor coordinate with each other to effectively avoid vehicle instability.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile yaw stability control, and in particular relates to a yaw stability control method for a four-wheel drive automobile and the four-wheel drive automobile. Background Art

[0002] Compared to axle-axle vehicles, in-wheel motor vehicles significantly improve vehicle stability due to the independently controllable torque of each wheel motor. However, this also increases algorithm complexity. During vehicle stability control, the brake caliper torque and the in-wheel motor torque must not exceed their permitted operating ranges. Otherwise, the in-wheel motor or brake caliper torque will overload and damage them. Furthermore, the in-wheel motor torque and the brake caliper torque must be coordinated and coordinated, not independently. Otherwise, the in-wheel motor torque and the brake caliper torque will become chaotic, resulting in a failure to improve vehicle stability control and the overlapping and nesting of the brake caliper and in-wheel motor torques, causing vehicle instability. Summary of the Invention

[0003] The object of the present invention is to provide a yaw stability control method for a four-wheel drive vehicle and a four-wheel drive vehicle, so as to solve the yaw stability control problem of the vehicle.

[0004] The technical solutions of the present invention are as follows:

[0005] A yaw stability control method for a four-wheel drive vehicle, the method comprising the following steps:

[0006] Calculate the unilateral additional yaw torque required by the left and right wheels of the vehicle;

[0007] Calculate the left and right wheel torque change direction flags based on the total additional yaw torque required by the vehicle;

[0008] Calculate the remaining available torque of each motor, including two types: the remaining available torque with increasing torque and the remaining available torque with decreasing torque;

[0009] Calculate the remaining available torque of each brake caliper, including two types: the remaining available torque with increasing torque and the remaining available torque with decreasing torque;

[0010] Based on the remaining available torque of each motor and the remaining available torque of each brake caliper, the maximum additional yaw torque generated by the remaining available torque of the left and right motors and the left and right brake calipers is calculated, including two types: the maximum additional yaw torque generated by the remaining available torque with increased torque and the maximum additional yaw torque generated by the remaining available torque with decreased torque;

[0011] Based on the left and right wheel torque change direction flags, the selection coefficients of the remaining available torque of the motor and brake caliper are calculated, including two types: torque increase selection coefficient and torque reduction selection coefficient;

[0012] Calculating a maximum remaining available torque that can be executed by each motor and each brake caliper based on the remaining available torque of each motor, the remaining available torque of each brake caliper, and selection coefficients of the remaining available torque of the motor and the brake caliper;

[0013] Calculate the maximum additional yaw torque superimposed on the same side based on the selection coefficients of the remaining available torque of the motor and the brake caliper, including the maximum additional yaw torque superimposed on the motor on the same side, the maximum additional yaw torque superimposed on the brake caliper on the same side, and the maximum additional yaw torque superimposed on the motor and the brake caliper on the same side;

[0014] Calculate the scaling factor of the remaining available torque of each motor and each brake caliper based on the relative magnitude relationship between the maximum additional yaw torque superimposed on the same side and the required additional yaw torque on one side;

[0015] Calculating the torque increase or decrease performed by each motor and each brake caliper based on the scaling factor of the remaining available torque of each motor and each brake caliper;

[0016] The target torque ultimately output by each motor and each brake caliper is calculated, which is equal to the driver's intended torque plus the torque increase or decrease.

[0017] Furthermore, the calculation formula for the unilateral required additional yaw torque is as follows:

[0018]

[0019] Where: ΔM fr represents the unilateral required additional yaw torque, that is, the required additional yaw torque required by the left wheel of the vehicle, and also the required additional yaw torque required by the right wheel of the vehicle; ΔM represents the total required additional yaw torque of the vehicle;

[0020] Among them, ΔM=0 indicates that the vehicle is in a stable state and no additional yaw stabilization control is required; ΔM<0 indicates that the actual clockwise movement trend of the vehicle around the exact center of the vehicle is insufficient or the actual counterclockwise movement trend of the vehicle around the exact center of the vehicle is too large. In this case, the clockwise movement trend of the vehicle around the exact center of the vehicle should be enhanced or the counterclockwise movement trend of the vehicle around the exact center of the vehicle should be weakened; ΔM>0 indicates that the actual clockwise movement trend of the vehicle around the exact center of the vehicle is too large or the actual counterclockwise movement trend of the vehicle around the exact center of the vehicle is insufficient. In this case, the clockwise movement trend of the vehicle around the exact center of the vehicle should be weakened or the counterclockwise movement trend of the vehicle around the exact center of the vehicle should be enhanced.

[0021] Furthermore, the vehicle's left wheel torque change direction flag s l for:

[0022]

[0023] Vehicle right wheel torque change direction flag s r for:

[0024] s r =-s l

[0025] Where s l Indicates the direction of the torque change of the left wheel of the vehicle, s r Indicates the direction of the torque change of the right wheel of the vehicle, ΔM indicates the total required additional yaw torque of the vehicle;

[0026] s l =1 means the left wheel torque should be increased; s l =-1 means the left wheel torque should be reduced; s l =0 means the left wheel torque remains unchanged; s r =1 means the right wheel torque should be increased; s r =-1 means the right wheel torque should be reduced; s r =0 means the right wheel torque remains unchanged;

[0027] A quadratic function is used to calculate a selection coefficient for the residual available torque of the motor and the brake caliper; the coefficient is used to select only the residual available torque with the same effect on vehicle stability control among the residual available torque with increased motor torque, the residual available torque with decreased motor torque, the residual available torque with increased brake caliper torque, and the residual available torque with decreased brake caliper torque;

[0028] The remaining available torque when the motor torque increases and the remaining available torque when the brake caliper torque decreases are one type, i.e., the torque of the wheel increases; the remaining available torque when the motor torque decreases and the remaining available torque when the brake caliper torque increases are another type, i.e., the torque of the wheel decreases;

[0029] The selection coefficient quadratic function formulas for the remaining available torque when the left front and left rear motor torques are increased, the remaining available torque when the left front and left rear motor torques are reduced, the remaining available torque when the left front and left rear brake caliper torques are increased, and the remaining available torque when the left front and left rear brake caliper torques are reduced are as follows:

[0030]

[0031] Where: k l1 Indicates the selection coefficient of the left torque increase; kl2 represents the selection coefficient for the left torque reduction; a1, a2, a3 represent the quadratic function coefficients of the selection coefficient for the left torque increase; β1, β2, β3 represent the quadratic function coefficients of the selection coefficient for the right torque reduction; specifically:

[0032]

[0033] The selection coefficient quadratic function formulas for the remaining available torque when the right front and right rear motor torques are increased, the remaining available torque when the right front and right rear motor torques are reduced, the remaining available torque when the right front and right rear brake caliper torques are increased, and the remaining available torque when the right front and right rear brake caliper torques are reduced are as follows:

[0034]

[0035] Where: k r1 Indicates the selection coefficient of the right torque increase; k r2 represents the selection coefficient for the right torque reduction; γ1, γ2, γ3 represent the quadratic function coefficients of the selection coefficients for the right torque increase; τ1, τ2, τ3 represent the quadratic function coefficients of the selection coefficients for the right torque reduction; specifically:

[0036]

[0037] It can be seen that: ΔM>0 is equivalent to s l =-1,s r =1, then k r1 =1,k r2 =0,k l1 =0,k l2 =1; ΔM<0 is equivalent to s l =1,s r =-1, then k r1 =0,k r2 =1,k l1 =1,k l2 =0; ΔM = 0 is equivalent to s l =0,s r =0, then k r1 =0,k r2 =0,k l1 =0,k l2 =0.

[0038] Furthermore, the remaining available torque after the driver's intended torque is increased to the maximum torque of each motor is the remaining available torque after the torque of each motor is increased. This torque represents the maximum value of the increase in the motor torque. The calculation formula is as follows:

[0039]

[0040] Where: ΔTd1 flmax Indicates the remaining available torque of the left front motor torque increase; ΔTd1 frmax Indicates the remaining available torque of the right front motor torque increase; ΔTd1 rlmax Indicates the remaining available torque of the left rear motor torque increase; ΔTd1 rrmax Indicates the remaining available torque of the right rear motor torque increase; Td flmax (w fl ) indicates that the left front motor is at its actual speed w fl The maximum torque available in the state; Td frmax (w fr ) indicates that the right front motor is at its actual speed w fr The maximum torque available in the state; Td rlmax (w rl ) indicates that the left rear motor is at its actual speed w rl The maximum torque available in the state; Td rrmax (w rr ) indicates that the right rear motor is at its actual speed w rr The maximum torque that can be used in the state; Ta fl represents the driver's intended torque of the left front motor calculated based on the throttle opening and brake pedal opening; Ta fr represents the driver's intended torque of the right front motor calculated based on the throttle opening and brake pedal opening; Ta rl The driver's intended torque of the left rear motor is calculated based on the accelerator opening and brake pedal opening; Ta rr Indicates the driver's intended torque for the right rear motor calculated based on the accelerator opening and brake pedal opening;

[0041] The remaining available torque based on the driver's intended torque reduction to the minimum torque of each motor is the remaining available torque after the torque of each motor is reduced. This torque represents the maximum value of the motor torque reduction. The calculation formula is as follows:

[0042]

[0043] Among them: the minimum motor torque is the opposite of the maximum motor torque; ΔTd2 flmax Indicates the remaining available torque after the left front motor torque is reduced; ΔTd2 frmax Indicates the remaining available torque after the right front motor torque is reduced; ΔTd2 rlmax Indicates the remaining available torque after the left rear motor torque is reduced; ΔTd2 rrmax Indicates the remaining available torque after the right rear motor torque is reduced;

[0044] The remaining available torque after the driver's intended braking torque is increased to the maximum torque of each brake caliper is the remaining available torque after the torque of each brake caliper is increased. This torque represents the maximum increase in the brake caliper torque and is calculated as follows:

[0045]

[0046] Where: ΔTb1 flmax Indicates the remaining available torque after the left front brake caliper torque increases; ΔTb1 frmax Indicates the remaining available torque of the right front brake caliper torque increase; ΔTb1 rlmax Indicates the remaining available torque after the left rear brake caliper torque increases; ΔTb1 rrmax Indicates the remaining available torque of the right rear brake caliper torque increase; Tb flmax Indicates the maximum torque available for the left front brake caliper; Tb frmax Indicates the maximum torque available for the right front brake caliper; Tb rlmax Indicates the maximum torque available for the left rear brake caliper; Tb rrmax Indicates the maximum torque available for the right rear brake caliper; Tb fl Indicates the left front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb fr Indicates the right front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rl Indicates the left rear brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rr Indicates the right rear brake caliper torque obtained by calculating the driving intention based on the brake pedal opening;

[0047] The remaining available torque based on the driver's intended braking torque being reduced to the minimum value of each brake caliper torque is the remaining available torque after the torque of each brake caliper is reduced. This torque represents the maximum value of the reduction amplitude of the brake caliper torque. The calculation formula is as follows:

[0048]

[0049] Among them: the minimum value of the brake caliper torque is 0; ΔTb2 flmax Indicates the remaining available torque after the left front brake caliper torque is reduced; ΔTb2 frmax Indicates the remaining available torque after the right front brake caliper torque is reduced; ΔTb2 rlmax Indicates the remaining available torque after the left rear brake caliper torque is reduced; ΔTb2 rrmax Indicates the remaining available torque with reduced torque at the right rear brake caliper.

[0050] Furthermore, the maximum additional yaw torque generated by the remaining available torque of the left and right motors and the left and right brake calipers is calculated as follows:

[0051]

[0052] Where: ΔMd1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front motor and the left rear motor; ΔMd1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front motor and the right rear motor torque increase; ΔMd2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front motor and the left rear motor; ΔMd2 rmax The maximum additional yaw torque provided by the remaining available torque after the torque reduction of the right front motor and the right rear motor; ΔMb1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front brake caliper and the left rear brake caliper torque increase; ΔMb1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front brake caliper and the right rear brake caliper torque increase; ΔMb2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front brake caliper and the left rear brake caliper; ΔMb2 rmax —The maximum additional yaw torque provided by the remaining available torque after the torque reduction of the right front brake caliper and the right rear brake caliper; r is the tire radius of the wheel; θ is the navigation angle of the front axle vehicle; d1 is the front axle track; d2 is the rear axle track.

[0053] Furthermore, the maximum remaining available torque that can be executed by each motor and each brake caliper is calculated as follows:

[0054]

[0055] Where: ΔTd flmax Indicates the maximum remaining available torque that can be executed by the left front motor; ΔTd frmax Indicates the maximum remaining available torque that can be executed by the right front motor; ΔTd rlmax Indicates the maximum remaining available torque that the left rear motor can execute; ΔTd rrmax Indicates the maximum remaining available torque that the right rear motor can perform; ΔTb flmax Indicates the maximum remaining available torque that the left front brake caliper can perform; ΔTb frmax Indicates the maximum remaining available torque that the right front brake caliper can perform; ΔTb rlmax Indicates the maximum remaining available torque that the left rear brake caliper can perform; ΔTb rrmax Indicates the maximum remaining available torque that can be performed by the right rear brake caliper;

[0056] k l1 Indicates the selection coefficient of the left torque increase; kl2 Indicates the selection coefficient of the left torque reduction; k r1 Indicates the selection coefficient of the right torque increase; k r2 Indicates the selection coefficient of right torque reduction; Δrb1 flmax Indicates the remaining available torque after the left front brake caliper torque increases; ΔTb1 frmax Indicates the remaining available torque of the right front brake caliper torque increase; ΔTb1 rlmax Indicates the remaining available torque after the left rear brake caliper torque increases; ΔTb1 rrmax Indicates the remaining available torque of the right rear brake caliper torque increase; ΔTb2 flmax Indicates the remaining available torque after the left front brake caliper torque is reduced; ΔTb2 frmax Indicates the remaining available torque after the right front brake caliper torque is reduced; ΔTb2 rlmax Indicates the remaining available torque after the left rear brake caliper torque is reduced; ΔTb2 rrmax Indicates the remaining available torque with reduced torque at the right rear brake caliper.

[0057] Furthermore, the maximum additional yaw torque superimposed on the same side is calculated as follows:

[0058]

[0059] Where: ΔM lmax Indicates the maximum additional yaw torque superimposed by the left motor and brake caliper; ΔM rmax Indicates the maximum additional yaw torque superimposed by the right motor and brake caliper; ΔMd lmax Indicates the maximum additional yaw torque superimposed by the left motor; ΔMd rmax Indicates the maximum additional yaw torque superimposed by the right motor; ΔMb lmax Indicates the maximum additional yaw torque superimposed by the left brake caliper; ΔMb rmax represents the maximum additional yaw torque superimposed by the right brake caliper; k l1 Indicates the selection coefficient of the left torque increase; k l2 Indicates the selection coefficient of the left torque reduction; k r1 Indicates the selection coefficient of the right torque increase; k r2 Indicates the selection factor for right-side torque reduction.

[0060] Furthermore, the method for calculating the scaling coefficient of the remaining available torque of each motor and each brake caliper includes:

[0061] (1) If the maximum additional yaw torque superimposed by the left motor and the brake caliper is not less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax ≥ΔM rmax hour;

[0062] ① The additional yaw torque required on one side is less than the maximum additional yaw torque superimposed on the right side, that is, ΔM fr <ΔM rmax

[0063] If the additional yaw torque required on one side is less than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr <ΔMd rmax , then the torque scaling factor calculation formula is:

[0064]

[0065] Where: Kd l Indicates the torque scaling factor of the left motor; Kd r Indicates the torque scaling factor of the right motor; Kb l Indicates the torque scaling factor of the left brake caliper; Kb r Indicates the torque scaling factor of the right brake caliper;

[0066] If the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr ≥ΔMd rmax , then the torque scaling factor calculation formula is:

[0067]

[0068] If the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr <ΔMd rmax , then the torque scaling factor calculation formula is:

[0069]

[0070] If the additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr ≥ΔMd rmax , then the torque scaling factor calculation formula is:

[0071]

[0072] ② The additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed on the right side and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed on the left side, that is, ΔM rmax ≤ΔM fr ≤ΔM lmax

[0073] If the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax ≤ΔMd lmax , then the torque scaling factor calculation formula is:

[0074]

[0075] If the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax >ΔMd lmax , then the torque scaling factor calculation formula is:

[0076]

[0077] ③ The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed on the left side, that is, ΔM fr >ΔM lmax

[0078] If the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax ≤ΔMd lmax , then the torque scaling factor is calculated as:

[0079]

[0080] If the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor ΔM rmax >ΔMd lmax , then the torque scaling factor calculation formula is:

[0081]

[0082] (2) If the maximum additional yaw torque superimposed by the left motor and the brake caliper is less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax <ΔM rmax hour;

[0083] ① The additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, i.e. ΔMfr ≤ΔM lmax

[0084] If the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≤ΔMd lmax And ΔM fr ≤ΔMd rmax , then the torque scaling factor calculation formula is:

[0085]

[0086] If the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr >ΔMd lmax And ΔM fr ≤ΔMd rmax , then the torque scaling factor calculation formula is:

[0087]

[0088] If the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≤ΔMd lmax And ΔM fr >ΔMd rmax , then the torque scaling factor calculation formula is:

[0089]

[0090] If the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr >ΔMd lmax And ΔM fr >ΔMd rmax , then the torque scaling factor calculation formula is:

[0091]

[0092] ② The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the left motor and the brake caliper, and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax <ΔM fr ≤ΔM rmax

[0093] If the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax , then the torque scaling factor calculation formula is:

[0094]

[0095] If the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side, that is, ΔM lmax >ΔMd rmax , the torque scaling factor calculation formula is:

[0096]

[0097] ③ The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, that is, ΔM fr >ΔM rmax

[0098] If the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax , then the torque scaling factor calculation formula is:

[0099]

[0100] If the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side, that is, ΔM kmax >ΔMd rmax , then the torque scaling factor calculation formula is:

[0101]

[0102] The torque increase or decrease calculation formula for each motor is as follows:

[0103]

[0104] Where: ΔTd fl Indicates the torque increase or decrease performed by the left front motor; ΔTd fr Indicates the torque increase or decrease performed by the right front motor; ΔTd rl Indicates the torque increase or decrease performed by the left rear motor; ΔTd rr Indicates the torque increase or decrease performed by the right rear motor;

[0105] The torque increase or decrease performed by each brake caliper is calculated as follows:

[0106]

[0107] Where: ΔTb fl Indicates the torque increase or decrease performed by the left front brake caliper; ΔTb fr Indicates the torque increase or decrease performed by the right front brake caliper; ΔTb rl Indicates the torque increase or decrease performed by the left rear brake caliper; ΔTb rr Indicates the amount of torque increase or decrease performed by the right rear brake caliper.

[0108] Furthermore, the target torque ultimately output by each motor and each brake caliper is calculated as follows:

[0109]

[0110] Where: Td flout Indicates the target torque output by the left front motor; Td frout Indicates the target torque output by the right front motor; Td rlout Indicates the target torque output by the left rear motor; Td rrout Indicates the target torque output by the right rear motor; Tb flout Indicates the target torque output by the left front brake caliper; Tb frout Indicates the target torque output by the right front brake caliper; Tb rlout Indicates the target torque output by the left rear brake caliper; Tb rrout Indicates the target torque output by the right rear brake caliper.

[0111] A four-wheel drive vehicle adopts any one of the above-mentioned four-wheel drive vehicle yaw stability control methods.

[0112] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0113] For vehicles with in-wheel motors, the yaw stability control process ensures that the brake calipers and in-wheel motors operate within their capabilities, avoiding the risk of damage to the in-wheel motors and brake calipers.

[0114] For vehicles with hub motors, the brake calipers and hub motors work in coordination with each other during yaw stabilization. First, the hub motor provides yaw stabilization torque, and the brake calipers supplement the insufficient part provided by the hub motor. This maximizes the vehicle's lateral stability control capabilities while effectively avoiding confusion between the hub motor and brake torque, such as simultaneous increase or decrease causing stability overlap, which in turn leads to the failure of vehicle stability control and the problem of vehicle instability. BRIEF DESCRIPTION OF THE DRAWINGS

[0115] Figure 1 It is a flow chart of the yaw stability control method of a four-wheel drive vehicle of the present invention. DETAILED DESCRIPTION

[0116] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0117] The yaw stability control method of a four-wheel drive vehicle of the present invention is as follows: Figure 1 As shown, the following steps are included:

[0118] Step 1: Calculate the required additional yaw torque for the left and right wheels. Based on the vehicle's yaw stability control requirements and to maintain vehicle dynamics, the required additional yaw torque is evenly distributed to the left and right sides of the vehicle, representing the required additional yaw torque for the left and right wheels.

[0119]

[0120] Where: ΔM fr It represents the unilateral required additional yaw torque, that is, the required additional yaw torque required by the left wheel of the vehicle, and also the required additional yaw torque required by the right wheel of the vehicle; ΔM represents the total required additional yaw torque of the vehicle.

[0121] The required additional yaw torque required by the left wheel of the vehicle plus the required additional yaw torque required by the right wheel of the vehicle equals the total required additional yaw torque of the vehicle, that is, ΔM fr +ΔM fr =|ΔM|.

[0122] Furthermore, ΔM=0 indicates that the vehicle is in a stable state and no additional yaw stabilization control is required; ΔM<0 indicates that the vehicle's actual clockwise movement trend around the vehicle's exact center is insufficient or the vehicle's actual counterclockwise movement trend around the vehicle's exact center is too large, and the vehicle's clockwise movement trend around the vehicle's exact center should be enhanced or the vehicle's actual counterclockwise movement trend around the vehicle's exact center should be weakened; ΔM>0 indicates that the vehicle's actual clockwise movement trend around the vehicle's exact center is too large or the vehicle's actual counterclockwise movement trend around the vehicle's exact center is insufficient, and the vehicle's clockwise movement trend around the vehicle's exact center should be weakened or the vehicle's actual counterclockwise movement trend around the vehicle's exact center should be enhanced.

[0123] Step 2: Calculate the left and right wheel torque change direction flags based on the total required additional yaw torque of the vehicle. In order to keep the vehicle dynamics unchanged, the right wheel torque change direction s r The direction of the torque change of the left wheel of the vehicle s l The opposite should be true: if the left-right torque of the vehicle increases on one side, the other side must decrease. Therefore, when ΔM > 0, to reduce the clockwise rotation of the vehicle around its true center or increase the counterclockwise rotation of the vehicle around its true center, the left wheel torque should decrease, while the right wheel torque should increase. When ΔM < 0, to increase the clockwise rotation of the vehicle around its true center or reduce the counterclockwise rotation of the vehicle around its true center, the left wheel torque should increase, while the right wheel torque should decrease.

[0124] Then the vehicle's left wheel torque change direction flag is s l for:

[0125]

[0126] Vehicle right wheel torque change direction flag s r Calculated as:

[0127] s r =-s l

[0128] Where: s l Indicates the direction of the torque change of the left wheel of the vehicle; r Indicates the flag position of the torque change direction of the right wheel of the vehicle.

[0129] It can be seen that: l =1 means the left wheel torque should be increased; s l =-1 means the left wheel torque should be reduced; s l =0 means the left wheel torque remains unchanged; s r =1 means the right wheel torque should be increased; s r =-1 means the right wheel torque should be reduced; s r =0 means the right wheel torque remains unchanged.

[0130] Further information: r +s l =0, the goal of keeping the wheel torque on both sides constant or increasing one side while decreasing the other side can be achieved.

[0131] s r With s l There are only three types of relationships between them:l =1 means the left wheel torque should increase, and s r =-1 means the right wheel torque should be reduced; s l =-1 means the left wheel torque should be reduced, and s r =1 means the right wheel torque should be increased; s l =0 means the left wheel torque remains unchanged; s r =0 means the right wheel torque remains unchanged.

[0132] Step 3: Calculate the remaining available torque of each motor, which includes two types: one is the remaining available torque with increasing torque, and the other is the remaining available torque with decreasing torque.

[0133] ① Calculate the remaining available torque after the driver's intention to increase the torque to the maximum value of each motor torque. This torque represents the maximum value of the motor torque increase.

[0134]

[0135] Where: ΔTd1 flmax Indicates the remaining available torque of the left front motor torque increase; ΔTd1 frmax Indicates the remaining available torque of the right front motor torque increase; ΔTd1 rlmax Indicates the remaining available torque of the left rear motor torque increase; ΔTd1 rrmax Indicates the remaining available torque of the right rear motor torque increase; Td flmax (w fl ) indicates that the left front motor is at its actual speed w fl The maximum torque available in the state; Td frmax (w fr ) indicates that the right front motor is at its actual speed w fr The maximum torque available in the state; Td rlmax (w rl ) indicates that the left rear motor is at its actual speed w rl The maximum torque available in the state; Td rrmax (w rr ) indicates that the right rear motor is at its actual speed w rr The maximum torque that can be used in the state; Ta fl represents the driver's intended torque of the left front motor calculated based on the throttle opening and brake pedal opening; Ta fr represents the driver's intended torque of the right front motor calculated based on the throttle opening and brake pedal opening; Ta rl The driver's intended torque of the left rear motor is calculated based on the accelerator opening and brake pedal opening; Ta rrIndicates the driver's intended torque for the right rear motor calculated based on the accelerator opening and brake pedal opening.

[0136] ② Calculate the remaining available torque based on the driver's intended torque reduction to the minimum torque of each motor. This torque represents the maximum reduction in motor torque. The minimum motor torque is the inverse of the maximum motor torque.

[0137]

[0138] Where: ΔTd2 flmax Indicates the remaining available torque after the left front motor torque is reduced; ΔTd2 frmax Indicates the remaining available torque after the right front motor torque is reduced; ΔTd2 rlmax Indicates the remaining available torque after the left rear motor torque is reduced; ΔTd2 rrmax Indicates the remaining available torque after the right rear motor torque reduction.

[0139] Step 4: Calculate the remaining available torque of each brake caliper, which includes two types: one is the remaining available torque with increased torque, and the other is the remaining available torque with reduced torque.

[0140] ① Calculate the remaining available torque after the driver's intention to increase the braking torque to the maximum torque of each brake caliper. This torque represents the maximum increase in the brake caliper torque.

[0141]

[0142] Where: ΔTb1 flmax Indicates the remaining available torque after the left front brake caliper torque increases; ΔTb1 frmax Indicates the remaining available torque of the right front brake caliper torque increase; ΔTb1 rlmax Indicates the remaining available torque after the left rear brake caliper torque increases; ΔTb1 rrmax Indicates the remaining available torque of the right rear brake caliper torque increase; Tb flmax Indicates the maximum torque available for the left front brake caliper; Tb frmax Indicates the maximum torque available for the right front brake caliper; Tb rlmax Indicates the maximum torque available for the left rear brake caliper; Tb rrmax Indicates the maximum torque available for the right rear brake caliper; Tb fl Indicates the left front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb fr Indicates the right front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rl Indicates the left rear brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rrIndicates the right rear brake caliper torque obtained by calculating the driving intention based on the brake pedal opening.

[0143] ② Calculate the remaining available torque based on the driver's intention to reduce the braking torque to the minimum value of each brake caliper torque, which represents the maximum value of the brake caliper torque reduction, where the minimum brake caliper torque is 0.

[0144]

[0145] Where: ΔTb2 flmax Indicates the remaining available torque after the left front brake caliper torque is reduced; ΔTb2 frmax Indicates the remaining available torque after the right front brake caliper torque is reduced; ΔTb2 rlmax Indicates the remaining available torque after the left rear brake caliper torque is reduced; ΔTb2 rrmax Indicates the remaining available torque with reduced torque at the right rear brake caliper.

[0146] Step 5: Calculate the maximum additional yaw torque that can be generated by the remaining available torque of the left and right motors and brake calipers based on the vehicle's geometric dimensions.

[0147]

[0148] Where: ΔMd1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front motor and the left rear motor; ΔMd1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front motor and the right rear motor torque increase; ΔMd2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front motor and the left rear motor; ΔMd2 rmax The maximum additional yaw torque provided by the remaining available torque after the torque reduction of the right front motor and the right rear motor; ΔMb1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front brake caliper and the left rear brake caliper torque increase; ΔMb1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front brake caliper and the right rear brake caliper torque increase; ΔMb2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front brake caliper and the left rear brake caliper; ΔMb2 rmax The maximum additional yaw torque provided by the remaining available torque after the torque of the right front brake caliper and the right rear brake caliper is reduced; r represents the tire radius of the wheel; θ represents the navigation angle of the front axle vehicle; d1 represents the front axle track; d2 is the rear axle track, and d1≈d2.

[0149] Step 6: Use a quadratic function to calculate the selection coefficients for the remaining available torque of the motor and brake caliper. This coefficient ensures that only the remaining available torque with increased motor torque, decreased motor torque, increased brake caliper torque, and decreased brake caliper torque, whichever has the same effect on vehicle stability control, is selected.

[0150] For the motor and brake caliper inside the same wheel, the remaining available torque when the motor torque increases and the remaining available torque when the brake caliper torque decreases are one category, that is, the torque of the wheel increases; the remaining available torque when the motor torque decreases and the remaining available torque when the brake caliper torque increases are another category, that is, the torque of the wheel decreases.

[0151] ① The remaining available torque when the left front and left rear motor torque increases, the remaining available torque when the left front and left rear motor torque decreases, the remaining available torque when the left front and left rear brake caliper torque increases, and the remaining available torque when the left front and left rear brake caliper torque decreases are selected using the quadratic function selection formula:

[0152]

[0153] Where: k l1 Indicates the selection coefficient of the left torque increase; k l2 represents the selection coefficient for reducing the left torque; a1, a2, a3 represent the quadratic function coefficients of the selection coefficient for increasing the left torque; β1, β2, β3 represent the quadratic function coefficients of the selection coefficient for reducing the right torque.

[0154] It can be seen that: ΔM<0, that is, when the left torque increases, the remaining available torque of the left front and left rear motor torque increases, and the remaining available torque of the left front and left rear brake caliper torque decreases are selected; ΔM>0, that is, when the left torque decreases, the remaining available torque of the left front and left rear motor torque decreases, and the remaining available torque of the left front and left rear brake caliper torque increases are selected; ΔM=0, that is, when the left torque remains unchanged, the remaining available torque of the left front and left rear motor torque increases, the remaining available torque of the left front and left rear motor torque decreases, the remaining available torque of the left front and left rear brake caliper torque increases, and the remaining available torque of the left front and left rear brake caliper torque decreases are not selected. That is: ΔM>0 is equivalent to s l =-1, then k l1 =0,k l2 =1; ΔM<0 is equivalent to s l =1, then k l1 =1,k l2 =0; ΔM = 0 is equivalent to s l =0, then k l1 =0,k l2 =0.

[0155] Substituting the above values, we can see that:

[0156]

[0157] Furthermore, we can also know that:

[0158]

[0159] but: a3=0, β3=0;

[0160] Furthermore, k l1 、k l2 can be converted to:

[0161]

[0162] ② The remaining available torque when the right front and right rear motor torque increases, the remaining available torque when the right front and right rear motor torque decreases, the remaining available torque when the right front and right rear brake caliper torque increases, and the remaining available torque when the right front and right rear brake caliper torque decreases are selected using the quadratic function selection formula:

[0163]

[0164] Where: k r1 Indicates the selection coefficient of the right torque increase; k r2 It represents the selection coefficient for reducing the torque on the right side; γ1, γ2, and γ3 represent the quadratic function coefficients of the selection coefficient for increasing the torque on the right side; τ1, τ2, and τ3 represent the quadratic function coefficients of the selection coefficient for reducing the torque on the right side.

[0165] It can be seen that: ΔM<0, that is, when the right torque decreases, the remaining available torque of the right front and right rear motor torque decreases, and the remaining available torque of the right front and right rear brake caliper torque increases are selected; ΔM>0, that is, when the right torque increases, the remaining available torque of the right front and right rear motor torque increases, and the remaining available torque of the left front and left rear brake caliper torque decreases are selected; ΔM=0, that is, when the left torque remains unchanged, the remaining available torque of the right front and right rear motor torque increases, the remaining available torque of the right front and right rear motor torque decreases, the remaining available torque of the right front and right rear brake caliper torque increases, and the remaining available torque of the right front and right rear brake caliper torque decreases are not selected. That is: ΔM>0 is equivalent to s r =1, then k r1 =1,k r2 =0; ΔM<0 is equivalent to s r =-1, then k r1 =0,k r2 =1; ΔM = 0 is equivalent to s r =0, then kr1 =0,k r2 =0.

[0166] Substituting the above values, we can see that:

[0167]

[0168] Furthermore, we can also know that:

[0169]

[0170] but: γ3=0, τ3=0;

[0171] Furthermore, k r1 、k r2 can be converted to:

[0172]

[0173] Furthermore, we know that: ΔM>0 is equivalent to s l =-1,s r =1, then k r1 =1,k r2 =0,k l1 =0,k l2 =1; ΔM<0 is equivalent to s l =1,s r =-1, then k r1 =0,k r2 =1,k l1 =1,k l2 =0; ΔM = 0 is equivalent to s l =0,s r =0, then k r1 =0,k r2 =0,k l1 =0,k l2 =0. Its practical meaning is: if ΔM > 0, the right wheel uses the remaining available torque from the increased motor torque and the reduced brake caliper torque, while the left wheel uses the remaining available torque from the reduced motor torque and the increased brake caliper torque. If M < 0, the right wheel uses the remaining available torque from the reduced motor torque and the increased brake caliper torque, while the left wheel uses the remaining available torque from the increased motor torque and the reduced brake caliper torque. If ΔM = 0, neither left nor right wheel uses the remaining available torque.

[0174] Furthermore, we know that: k l1 、k l2 、k r1 、k r2∈{0, 1}, and k l1 、k l2 At most one is 1, that is, k l1 +k l2 ≤1;k r1 、k r2 At most one is 1, that is, k r1 +k r2 ≤1.

[0175] Step 7: Calculate the maximum remaining available torque that can be executed by each motor and brake caliper.

[0176]

[0177] Where: ΔTd flmax Indicates the maximum remaining available torque that can be executed by the left front motor; ΔTd frmax Indicates the maximum remaining available torque that can be executed by the right front motor; ΔTd rlmax Indicates the maximum remaining available torque that the left rear motor can execute; ΔTd rrmax Indicates the maximum remaining available torque that the right rear motor can perform; ΔTb flmax Indicates the maximum remaining available torque that the left front brake caliper can perform; ΔTb frmax Indicates the maximum remaining available torque that the right front brake caliper can perform; ΔTb rlmax Indicates the maximum remaining available torque that the left rear brake caliper can perform; ΔTb rrmax Indicates the maximum remaining available torque that can be performed by the right rear brake caliper.

[0178] Step 8: Calculate the superimposed additional yaw torque on the same side according to the selection coefficient of the remaining available torque, including the superimposed maximum additional yaw torque of the motor on the same side, the superimposed maximum additional yaw torque of the brake caliper on the same side, and the superimposed maximum additional yaw torque of the motor and the brake caliper.

[0179]

[0180] Where: ΔM lmax Indicates the maximum additional yaw torque superimposed by the left motor and brake caliper; ΔM rmax Indicates the maximum additional yaw torque superimposed by the right motor and brake caliper; ΔMd lmax Indicates the maximum additional yaw torque superimposed by the left motor; ΔMd rmax Indicates the maximum additional yaw torque superimposed by the right motor. ΔMb lmax Indicates the maximum additional yaw torque superimposed by the left brake caliper; ΔMb rmax Indicates the maximum additional yaw torque superimposed by the right brake caliper;

[0181] Furthermore, we know that: ΔMlmax ≥ΔMd lmax ,ΔM rmax ≥ΔMd rmax .

[0182] Where: k l1 and ΔMd1 lmax +ΔMb2 lmax The product of 0 indicates that the remaining available torque due to the increase in the left motor torque and the remaining available torque due to the decrease in the brake caliper torque are not selected; k l1 and ΔMd1 lmax +ΔMb2 lmax The product is ΔMd1 lmax +ΔMb2 lmax Select the remaining available torque when the left motor torque increases and the remaining available torque when the brake caliper torque decreases, and the same logic applies to the others.

[0183] Step 9: Calculate the scaling factor of the remaining available torque of the motor and brake caliper based on the relative magnitude relationship between the maximum superimposed additional yaw torque on the left and right sides and the additional yaw torque required on one side.

[0184] (1) If the maximum additional yaw torque superimposed by the left motor and the brake caliper is not less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax ≥ΔM rmax hour.

[0185] ① The additional yaw torque required on one side is less than the maximum additional yaw torque superimposed on the right side, i.e. ΔM fr <ΔM rmax .

[0186] Furthermore, if the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr <ΔMd rmax For the left and right sides of the vehicle, the motor only needs to use part of the maximum remaining available torque to achieve the additional yaw torque required on one side, and the brake caliper torque does not change. The torque scaling factor is calculated as:

[0187]

[0188] Where: Kd l Indicates the torque scaling factor of the left motor; Kd r Indicates the torque scaling factor of the right motor; Kb l Indicates the torque scaling factor of the left brake caliper; Kb r Indicates the torque scaling factor of the right brake caliper;

[0189] Furthermore, if the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr ≥ΔMd rmax For the left side of the vehicle, the left motor uses part of its maximum available torque to meet the additional yaw torque required on one side, and the left brake caliper torque remains unchanged. For the right side of the vehicle, the right motor uses its full maximum available torque, and the shortfall is compensated by the right brake caliper. The torque scaling factor is calculated as:

[0190]

[0191] Furthermore, if the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr <ΔMd rmax For the left side of the vehicle, the left motor uses all of its maximum available torque, and the remaining torque is compensated by the left brake caliper. For the right side of the vehicle, the right side can use part of its maximum available torque to meet the additional yaw torque required on one side, and the right brake caliper torque does not increase or change. The torque scaling factor is calculated as:

[0192]

[0193] Furthermore, if the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr ≥ΔMd rmax For the left side of the vehicle, the left motor uses its maximum available torque, and any shortfall is compensated by the left brake caliper. For the right side of the vehicle, the right motor uses its maximum available torque, and any shortfall is compensated by the right brake caliper. The torque scaling factor is calculated as:

[0194]

[0195] ② The additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed on the right side, and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed on the left side, that is, ΔM rmax ≤ΔM fr ≤ΔM lmax .

[0196] In order to keep the left torque change the same, the additional yaw torque on the left side must also be the same, and at the same time be as close to ΔM as possible. fr At this time, the required unilateral additional yaw torque on the left and right sides of the vehicle is no longer ΔM fr , but instead the maximum additional yaw torque ΔM superimposed on the right side rmax At this time, the right motor and brake caliper all use the maximum executable residual torque, and the torque used by the left motor and brake caliper should be based on the maximum additional yaw torque ΔM superimposed on the right side. rmax Maximum additional yaw torque ΔMd superimposed on the left motor lmax The relative size relationship is determined.

[0197] Furthermore, the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is: ΔM rmax ≤ΔMd lmax , then the right motor can use the maximum available residual torque to meet the requirement, and the torque of the right brake caliper will not change. The torque scaling factor is calculated as:

[0198]

[0199] Furthermore, the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor ΔM rmax >ΔMd lmax , then the left motor should not use the maximum available residual torque, and the shortfall will be compensated by the left brake caliper. The torque scaling factor is calculated as:

[0200]

[0201] ③ The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed on the left side, i.e. ΔM fr >ΔM lmax .

[0202] In order to keep the left torque change the same, the additional yaw torque on the left side must also be the same, and at the same time be as close to ΔM as possible. fr At this time, the required unilateral additional yaw torque on the left and right sides of the vehicle is no longer ΔM fr , but instead the maximum additional yaw torque ΔM superimposed on the right side rmaxAt this time, the right motor and brake caliper all use the maximum executable residual torque, and the torque used by the left motor and brake caliper should be based on the maximum additional yaw torque ΔM superimposed on the right side. rmax Maximum additional yaw torque ΔMd superimposed on the left motor lmax The relative size relationship is determined.

[0203] Furthermore, the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is: ΔM rmax ≤ΔMd lmax , then the right motor can use the maximum available residual torque to meet the requirement, and the torque of the right brake caliper will not change. The torque scaling factor is calculated as:

[0204]

[0205] Furthermore, the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor ΔM rmax >ΔMd lmax , then the left motor should not use the maximum available residual torque, and the shortfall will be compensated by the left brake caliper. The torque scaling factor is calculated as:

[0206]

[0207] (2) The maximum additional yaw torque superimposed by the left motor and the brake caliper is less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, i.e., ΔM lmax <ΔM rmax hour.

[0208] ① If the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, that is, ΔM fr ≤ΔM lmax hour.

[0209] Furthermore, if the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≤ΔMd lmax And ΔM fr ≤ΔMd rmax The left and right motors only need to use part of their maximum available torque to achieve the additional yaw torque required on one side of the vehicle. The torque of the brake caliper does not change. The torque scaling factor is calculated as:

[0210]

[0211] Furthermore, if the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr >ΔMd lmax And ΔM fr ≤ΔMd rmax , then for the left side of the vehicle, the left motor uses all of its maximum available torque, and the remaining torque is supplemented by the left brake caliper; for the right side of the vehicle, the right motor only needs to use part of its maximum available torque to achieve the additional yaw torque required on one side of the vehicle, and the torque of the right brake caliper does not change. The torque scaling factor is calculated as:

[0212]

[0213] Furthermore, if the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the right motor ΔM fr ≤ΔMd lmax And ΔM fr >ΔMd rmax , then for the left side of the vehicle, the left motor only needs to use part of its maximum available torque to achieve the additional yaw torque required on one side of the vehicle, and the torque of the left brake caliper does not change; for the right side of the vehicle, the right motor uses all of its maximum available torque, and the remaining torque is supplemented by the right brake caliper. The torque scaling factor is calculated as:

[0214]

[0215] Furthermore, if the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the right motor ΔM fr >ΔMd lmax And ΔM fr >ΔMd rmax , then for the left wheel of the vehicle, the left motor uses its full maximum available torque, with any shortfall being supplemented by the left brake caliper; for the right wheel of the vehicle, the right motor uses its full maximum available torque, with any shortfall being supplemented by the right brake caliper. The torque scaling factor is then calculated as:

[0216]

[0217] ② If the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the left motor and the brake caliper, and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax <ΔM fr ≤ΔM rmax hour.

[0218] In order to keep the left torque change the same, the additional yaw torque on the left side must also be the same, and at the same time be as close to ΔM as possible. fr At this time, the required unilateral additional yaw torque on the left and right sides of the vehicle is no longer ΔM fr , but instead the maximum additional yaw torque ΔM superimposed on the left lmax At this time, the left motor and brake caliper all use the maximum executable residual torque, and the torque used by the right motor and brake caliper should be based on the maximum additional yaw torque ΔM superimposed on the left side. lmax Maximum additional yaw torque ΔMd superimposed on the right motor rmax The relative size relationship is determined.

[0219] Furthermore, if the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax The left motor can use part of its maximum available torque to achieve the additional yaw torque required on one side of the vehicle, and the left brake caliper torque remains unchanged. The torque scaling factor is calculated as:

[0220]

[0221] Furthermore, if the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side motor ΔM lmax >ΔMd rmax , the right motor uses its maximum executable remaining torque, and the shortfall is supplemented by the right brake caliper.

[0222]

[0223] ③ If the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, that is, ΔM fr >ΔM rmax .

[0224] In order to keep the left torque change the same, the additional yaw torque on the left side must also be the same, and at the same time be as close to ΔM as possible. fr At this time, the required unilateral additional yaw torque on the left and right sides of the vehicle is no longer ΔM fr , but instead the maximum additional yaw torque ΔM superimposed on the leftlmax At this time, the left motor and brake caliper all use the maximum executable residual torque, and the torque used by the right motor and brake caliper should be based on the maximum additional yaw torque ΔM superimposed on the left side. lmax Maximum additional yaw torque ΔMd superimposed on the right motor rmax The relative size relationship is determined.

[0225] Furthermore, if the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax The left motor can use part of its maximum available torque to achieve the additional yaw torque required on one side of the vehicle, and the left brake caliper torque remains unchanged. The torque scaling factor is calculated as:

[0226]

[0227] Furthermore, if the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side motor ΔM lmax >ΔMd rmax , the right motor uses its maximum executable remaining torque, and the shortfall is supplemented by the right brake caliper.

[0228]

[0229] Step 10: Calculate the torque increase or decrease performed by each motor and brake caliper.

[0230] The torque variable executed by the motor is equal to the product of the torque sign flag on that side, the torque scaling factor of the motor on that side, and the maximum remaining available torque that can be executed by the motor, that is:

[0231]

[0232] Where: ΔTd fl Indicates the torque increase or decrease performed by the left front motor; ΔTd fr Indicates the torque increase or decrease performed by the right front motor; ΔTd rl Indicates the torque increase or decrease performed by the left rear motor; ΔTd rr Indicates the torque increase or decrease performed by the right rear motor;

[0233] The torque of the brake caliper is the inverse of the product of the torque sign flag on that side, the torque scaling factor of the brake caliper on that side, and the maximum remaining available torque that the brake caliper can execute (because the torque effect of the brake caliper and the torque effect of the motor on yaw stability are opposite, so the inverse is needed), that is:

[0234]

[0235] Where: ΔTb fl Indicates the torque increase or decrease performed by the left front brake caliper; ΔTb fr Indicates the torque increase or decrease performed by the right front brake caliper; ΔTb rl Indicates the torque increase or decrease performed by the left rear brake caliper; ΔTb rr Indicates the amount of torque increase or decrease performed by the right rear brake caliper;

[0236] Step 11: Calculate the target torque ultimately output by each motor and brake caliper, which is equal to the driver's intended torque plus the torque increase or decrease.

[0237]

[0238] Where: Td flout Indicates the target torque output by the left front motor; Td frout Indicates the target torque output by the right front motor; Td rlout Indicates the target torque output by the left rear motor; Td rrout Indicates the target torque output by the right rear motor; Tb flout Indicates the target torque output by the left front brake caliper; Tb frout Indicates the target torque output by the right front brake caliper; Tb rlout Indicates the target torque output by the left rear brake caliper; Tb rrout Indicates the target torque output by the right rear brake caliper.

[0239] The present invention also provides a four-wheel drive vehicle, which adopts any one of the above-mentioned four-wheel drive vehicle yaw stability control methods.

[0240] To sum up, for hub motor vehicles, the present invention ensures that the brake caliper and the hub motor both operate within their capabilities during the yaw stability control process, and do not exceed their capabilities, thereby avoiding the risk of damage to the hub motor and the brake caliper; for hub motor vehicles, the present invention coordinates with the hub motor during the yaw stability process, firstly the hub motor provides the yaw stability torque, and then the brake caliper supplements the insufficient part provided by the hub motor, thereby maximizing the utilization of the vehicle's lateral stability control capabilities, while effectively avoiding confusion between the hub motor and the brake torque, such as simultaneous increase or decrease causing stability overlap, which in turn leads to the problem of vehicle stability control failing to achieve vehicle instability.

[0241] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0242] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A yaw stability control method for a four-wheel drive vehicle, characterized in that: The method comprises the following steps: Calculate the unilateral additional yaw torque required by the left and right wheels of the vehicle; Calculate the left and right wheel torque change direction flags based on the total additional yaw torque required by the vehicle; Calculate the remaining available torque of each motor, including two types: the remaining available torque with increasing torque and the remaining available torque with decreasing torque; Calculate the remaining available torque of each brake caliper, including two types: the remaining available torque with increasing torque and the remaining available torque with decreasing torque; Based on the remaining available torque of each motor and the remaining available torque of each brake caliper, the maximum additional yaw torque generated by the remaining available torque of the left and right motors and the left and right brake calipers is calculated, including two types: the maximum additional yaw torque generated by the remaining available torque with increased torque and the maximum additional yaw torque generated by the remaining available torque with decreased torque; Based on the left and right wheel torque change direction flags, the selection coefficients of the remaining available torque of the motor and brake caliper are calculated, including two types: torque increase selection coefficient and torque reduction selection coefficient; Calculating a maximum remaining available torque that can be executed by each motor and each brake caliper based on the remaining available torque of each motor, the remaining available torque of each brake caliper, and selection coefficients of the remaining available torque of the motor and the brake caliper; Calculate the maximum additional yaw torque superimposed on the same side based on the selection coefficients of the remaining available torque of the motor and the brake caliper, including the maximum additional yaw torque superimposed on the motor on the same side, the maximum additional yaw torque superimposed on the brake caliper on the same side, and the maximum additional yaw torque superimposed on the motor and the brake caliper on the same side; Calculate the scaling factor of the remaining available torque of each motor and each brake caliper based on the relative magnitude relationship between the maximum additional yaw torque superimposed on the same side and the required additional yaw torque on one side; Calculating the torque increase or decrease performed by each motor and each brake caliper based on the scaling factor of the remaining available torque of each motor and each brake caliper; The target torque ultimately output by each motor and each brake caliper is calculated, which is equal to the driver's intended torque plus the torque increase or decrease.

2. The yaw stability control method for a four-wheel drive vehicle according to claim 1, characterized in that: The calculation formula for the additional yaw torque required on one side is as follows: Where: ΔM fr represents the unilateral required additional yaw torque, that is, the required additional yaw torque required by the left wheel of the vehicle, and also the required additional yaw torque required by the right wheel of the vehicle; ΔM represents the total required additional yaw torque of the vehicle; Among them, ΔM=0 indicates that the vehicle is in a stable state and no additional yaw stabilization control is required; ΔM<0 indicates that the actual clockwise movement trend of the vehicle around the exact center of the vehicle is insufficient or the actual counterclockwise movement trend of the vehicle around the exact center of the vehicle is too large. In this case, the clockwise movement trend of the vehicle around the exact center of the vehicle should be enhanced or the counterclockwise movement trend of the vehicle around the exact center of the vehicle should be weakened; ΔM>0 indicates that the actual clockwise movement trend of the vehicle around the exact center of the vehicle is too large or the actual counterclockwise movement trend of the vehicle around the exact center of the vehicle is insufficient. In this case, the clockwise movement trend of the vehicle around the exact center of the vehicle should be weakened or the counterclockwise movement trend of the vehicle around the exact center of the vehicle should be enhanced.

3. The yaw stability control method for a four-wheel drive vehicle according to claim 1, characterized in that: Vehicle left wheel torque change direction flag s l for: Vehicle right wheel torque change direction flag s r for: s r =-s l Where s l Indicates the direction of the torque change of the left wheel of the vehicle, s r Indicates the direction of the torque change of the right wheel of the vehicle, ΔM indicates the total required additional yaw torque of the vehicle; s l =1 means the left wheel torque should be increased; s l =-1 means the left wheel torque should be reduced; s l =0 means the left wheel torque remains unchanged; s r =1 means the right wheel torque should be increased; s r =-1 means the right wheel torque should be reduced; s r =0 means the right wheel torque remains unchanged; A quadratic function is used to calculate a selection coefficient for the residual available torque of the motor and the brake caliper; the coefficient is used to select only the residual available torque with the same effect on vehicle stability control among the residual available torque with increased motor torque, the residual available torque with decreased motor torque, the residual available torque with increased brake caliper torque, and the residual available torque with decreased brake caliper torque; The remaining available torque when the motor torque increases and the remaining available torque when the brake caliper torque decreases are one type, i.e., the torque of the wheel increases; the remaining available torque when the motor torque decreases and the remaining available torque when the brake caliper torque increases are another type, i.e., the torque of the wheel decreases; The selection coefficient quadratic function formulas for the remaining available torque when the left front and left rear motor torques are increased, the remaining available torque when the left front and left rear motor torques are reduced, the remaining available torque when the left front and left rear brake caliper torques are increased, and the remaining available torque when the left front and left rear brake caliper torques are reduced are as follows: Where: k l1 Indicates the selection coefficient of the left torque increase; k l2 represents the selection coefficient for the left torque reduction; a1, a2, a3 represent the quadratic function coefficients of the selection coefficient for the left torque increase; β1, β2, β3 represent the quadratic function coefficients of the selection coefficient for the right torque reduction; specifically: The selection coefficient quadratic function formulas for the remaining available torque when the right front and right rear motor torques are increased, the remaining available torque when the right front and right rear motor torques are reduced, the remaining available torque when the right front and right rear brake caliper torques are increased, and the remaining available torque when the right front and right rear brake caliper torques are reduced are as follows: Where: k r1 Indicates the selection coefficient of the right torque increase; k r2 represents the selection coefficient for the right torque reduction; γ1, γ2, γ3 represent the quadratic function coefficients of the selection coefficients for the right torque increase; τ1, τ2, τ3 represent the quadratic function coefficients of the selection coefficients for the right torque reduction; specifically: It can be seen that: ΔM>0 is equivalent to s l =-1,s r =1, then k r1 =1,k r2 =0,k l1 =0,k l2 =1; ΔM<0 is equivalent to s l =1,s r =-1, then k r1 =0,k r2 =1,k l1 =1,k l2 =0; ΔM = 0 is equivalent to s l =0,s r =0, then k r1 =0,k r2 =0,k l1 =0,k l2 =0.

4. The yaw stability control method for a four-wheel drive vehicle according to claim 3, characterized in that: The remaining available torque after the driver's intended torque is increased to the maximum torque of each motor is the remaining available torque after the torque of each motor is increased. This torque represents the maximum increase in the motor torque. The calculation formula is as follows: Where: ΔTd1 flmax Indicates the remaining available torque of the left front motor torque increase; ΔTd1 frmax Indicates the remaining available torque of the right front motor torque increase; ΔTd1 rlmax Indicates the remaining available torque of the left rear motor torque increase; ΔTd1 rrmax Indicates the remaining available torque of the right rear motor torque increase; Td flmax (w fl ) indicates that the left front motor is at its actual speed w fl The maximum torque available in the state; Td frmax (w fr ) indicates that the right front motor is at its actual speed w fr The maximum torque available in the state; Td rlmax (w rl ) indicates that the left rear motor is at its actual speed w rl The maximum torque available in the state; Td rrmax (w rr ) indicates that the right rear motor is at its actual speed w rr The maximum torque that can be used in the state; Ta fl represents the driver's intended torque of the left front motor calculated based on the throttle opening and brake pedal opening; Ta fr represents the driver's intended torque of the right front motor calculated based on the throttle opening and brake pedal opening; Ta rl The driver's intended torque of the left rear motor is calculated based on the accelerator opening and brake pedal opening; Ta rr Indicates the driver's intended torque for the right rear motor calculated based on the accelerator opening and brake pedal opening; The remaining available torque based on the driver's intended torque reduction to the minimum torque of each motor is the remaining available torque after the torque of each motor is reduced. This torque represents the maximum value of the motor torque reduction. The calculation formula is as follows: Among them: the minimum motor torque is the opposite of the maximum motor torque; ΔTd2 flmax Indicates the remaining available torque after the left front motor torque is reduced; ΔTd2 frmax Indicates the remaining available torque after the right front motor torque is reduced; ΔTd2 rlmax Indicates the remaining available torque after the left rear motor torque is reduced; ΔTd2 rrmax Indicates the remaining available torque after the right rear motor torque is reduced; The remaining available torque after the driver's intended braking torque is increased to the maximum torque of each brake caliper is the remaining available torque after the torque of each brake caliper is increased. This torque represents the maximum increase in the brake caliper torque and is calculated as follows: Where: ΔTb1 flmax Indicates the remaining available torque after the left front brake caliper torque increases; ΔTb1 frmax Indicates the remaining available torque of the right front brake caliper torque increase; ΔTb1 rlmax Indicates the remaining available torque after the left rear brake caliper torque increases; ΔTb1 rrmax Indicates the remaining available torque of the right rear brake caliper torque increase; Tb flmax Indicates the maximum torque available for the left front brake caliper; Tb frmax Indicates the maximum torque available for the right front brake caliper; Tb rlmax Indicates the maximum torque available for the left rear brake caliper; Tb rrmax Indicates the maximum torque available for the right rear brake caliper; Tb fl Indicates the left front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb fr Indicates the right front brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rl Indicates the left rear brake caliper torque obtained by driving intention based on the brake pedal opening; Tb rr Indicates the right rear brake caliper torque obtained by calculating the driving intention based on the brake pedal opening; The remaining available torque based on the driver's intended braking torque being reduced to the minimum value of each brake caliper torque is the remaining available torque after the torque of each brake caliper is reduced. This torque represents the maximum value of the reduction amplitude of the brake caliper torque. The calculation formula is as follows: Among them: the minimum value of the brake caliper torque is 0; ΔTb2 flmax Indicates the remaining available torque after the left front brake caliper torque is reduced; ΔTb2 frmax Indicates the remaining available torque after the right front brake caliper torque is reduced; ΔTb2 rlmax Indicates the remaining available torque after the left rear brake caliper torque is reduced; ΔTb2 rrmax Indicates the remaining available torque with reduced torque at the right rear brake caliper.

5. The yaw stability control method for a four-wheel drive vehicle according to claim 4, characterized in that: The maximum additional yaw torque generated by the remaining available torque of the left and right motors and the left and right brake calipers is calculated as follows: Where: ΔMd1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front motor and the left rear motor; ΔMd1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front motor and the right rear motor torque increase; ΔMd2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front motor and the left rear motor; ΔMd2 rmax The maximum additional yaw torque provided by the remaining available torque after the torque reduction of the right front motor and the right rear motor; ΔMb1 lmax Indicates the maximum additional yaw torque provided by the remaining available torque of the left front brake caliper and the left rear brake caliper torque increase; ΔMb1 rmax The maximum additional yaw torque provided by the remaining available torque of the right front brake caliper and the right rear brake caliper torque increase; ΔMb2 lmax Indicates the maximum additional yaw torque provided by the remaining available torque after the torque reduction of the left front brake caliper and the left rear brake caliper; ΔMb2 rmax —The maximum additional yaw torque provided by the remaining available torque after the torque reduction of the right front brake caliper and the right rear brake caliper; r is the tire radius of the wheel; θ is the navigation angle of the front axle vehicle; d1 is the front axle track; d2 is the rear axle track.

6. The yaw stability control method for a four-wheel drive vehicle according to claim 5, characterized in that: The maximum remaining available torque that can be executed by each motor and each brake caliper is calculated as follows: Where: ΔTd flmax Indicates the maximum remaining available torque that can be executed by the left front motor; ΔTd frmax Indicates the maximum remaining available torque that can be executed by the right front motor; ΔTd rlmax Indicates the maximum remaining available torque that the left rear motor can execute; ΔTd rrmax Indicates the maximum remaining available torque that the right rear motor can perform; ΔTb flmax Indicates the maximum remaining available torque that the left front brake caliper can perform; ΔTb frmax Indicates the maximum remaining available torque that the right front brake caliper can perform; ΔTb rlmax Indicates the maximum remaining available torque that the left rear brake caliper can perform; ΔTb rrmax Indicates the maximum remaining available torque that can be performed by the right rear brake caliper; k l1 Indicates the selection coefficient of the left torque increase; k l2 Indicates the selection coefficient of the left torque reduction; k r1 Indicates the selection coefficient of the right torque increase; k r2 Indicates the selection coefficient of right torque reduction; ΔTd1 flmax Indicates the remaining available torque of the left front motor torque increase; ΔTd1 frmax Indicates the remaining available torque of the right front motor torque increase; ΔTd1 rlmax Indicates the remaining available torque of the left rear motor torque increase; ΔTd1 rrmax Indicates the remaining available torque of the right rear motor torque increase; ΔTd2 flmax Indicates the remaining available torque after the left front motor torque is reduced; ΔTd2 frmax Indicates the remaining available torque after the right front motor torque is reduced; ΔTd2 rlmax Indicates the remaining available torque after the left rear motor torque is reduced; ΔTd2 rrmax Indicates the remaining available torque after the right rear motor torque is reduced; ΔTb1 flmax Indicates the remaining available torque after the left front brake caliper torque increases; ΔTb1 frmax Indicates the remaining available torque of the right front brake caliper torque increase; ΔTb1 rlmax Indicates the remaining available torque after the left rear brake caliper torque increases; ΔTb1 rrmax Indicates the remaining available torque of the right rear brake caliper torque increase; ΔTb2 flmax Indicates the remaining available torque after the left front brake caliper torque is reduced; ΔTb2 frmax Indicates the remaining available torque after the right front brake caliper torque is reduced; ΔTb2 rlmax Indicates the remaining available torque after the left rear brake caliper torque is reduced; ΔTb2 rrmax Indicates the remaining available torque with reduced torque at the right rear brake caliper.

7. The yaw stability control method for a four-wheel drive vehicle according to claim 6, characterized in that: The maximum additional yaw torque superimposed on the same side is calculated as follows: Where: ΔM lmax Indicates the maximum additional yaw torque superimposed by the left motor and brake caliper; ΔM rmax Indicates the maximum additional yaw torque superimposed by the right motor and brake caliper; ΔMd lmax Indicates the maximum additional yaw torque superimposed by the left motor; ΔMd rmax Indicates the maximum additional yaw torque superimposed by the right motor; ΔMb lmax Indicates the maximum additional yaw torque superimposed by the left brake caliper; ΔMb rmax represents the maximum additional yaw torque superimposed by the right brake caliper; k l1 Indicates the selection coefficient of the left torque increase; k l2 Indicates the selection coefficient of the left torque reduction; k r1 Indicates the selection coefficient of the right torque increase; k r2 Indicates the selection factor for right-side torque reduction.

8. The yaw stability control method for a four-wheel drive vehicle according to claim 7, characterized in that: The calculation method of the scaling factor of the remaining available torque of each motor and each brake caliper includes: (1) If the maximum additional yaw torque superimposed by the left motor and the brake caliper is not less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax ≥ΔM rmax hour; ① The additional yaw torque required on one side is less than the maximum additional yaw torque superimposed on the right side, that is, ΔM fr <ΔM rmax If the additional yaw torque required on one side is less than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr <ΔMd rmax , then the torque scaling factor calculation formula is: Where: Kd l Indicates the torque scaling factor of the left motor; Kd r Indicates the torque scaling factor of the right motor; Kb l Indicates the torque scaling factor of the left brake caliper; Kb r Indicates the torque scaling factor of the right brake caliper; If the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr <ΔMd lmax And ΔM fr ≥ΔMd rmax , then the torque scaling factor calculation formula is: If the unilateral additional yaw torque required is not less than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr <ΔMd rmax , then the torque scaling factor calculation formula is: If the additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≥ΔMd lmax And ΔM fr ≥ΔMD rmax , then the torque scaling factor calculation formula is: ② The additional yaw torque required on one side is not less than the maximum additional yaw torque superimposed on the right side and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed on the left side, that is, ΔM rmax ≤ΔM fr ≤ΔM lmax If the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax ≤ΔMd lmax , then the torque scaling factor calculation formula is: If the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax >ΔMd lmax , then the torque scaling factor calculation formula is: ③ The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed on the left side, that is, ΔM fr >ΔM lmax If the maximum additional yaw torque superimposed on the right side is not greater than the maximum additional yaw torque superimposed on the left side motor, that is, ΔM rmax ≤ΔMd lmax , then the torque scaling factor is calculated as: If the maximum additional yaw torque superimposed on the right side is greater than the maximum additional yaw torque superimposed on the left side motor ΔM rmax >ΔMd lmax , then the torque scaling factor calculation formula is: (2) If the maximum additional yaw torque superimposed by the left motor and the brake caliper is less than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax <ΔM rmax hour; ① The additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, i.e. ΔM fr ≤ΔM lmax If the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≤ΔMd lmax And ΔM fr ≤ΔMd rmax , then the torque scaling factor calculation formula is: If the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr >ΔMd lmax And ΔM fr ≤ΔMd rmax , then the torque scaling factor calculation formula is: If the unilateral additional yaw torque required is not greater than the maximum additional yaw torque superimposed by the left motor and the unilateral additional yaw torque required is greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr ≤ΔMd lmax And ΔM fr >ΔMd rmax , then the torque scaling factor calculation formula is: If the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the left motor and the additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the right motor, that is, ΔM fr >ΔMd lmax And ΔM fr >ΔMd rmax , then the torque scaling factor calculation formula is: ② The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the left motor and the brake caliper, and the additional yaw torque required on one side is not greater than the maximum additional yaw torque superimposed by the right motor and the brake caliper, that is, ΔM lmax <ΔM fr ≤ΔM rmax If the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax , then the torque scaling factor calculation formula is: If the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side, that is, ΔM lmax >ΔMd rmax , the torque scaling factor calculation formula is: ③ The additional yaw torque required on one side is greater than the maximum additional yaw torque superimposed by the right motor and brake caliper, that is, ΔM fr >ΔM rmax If the maximum additional yaw torque superimposed on the left side is not greater than the maximum additional yaw torque superimposed on the right side motor, that is, ΔM lmax ≤ΔMd rmax , then the torque scaling factor calculation formula is: If the maximum additional yaw torque superimposed on the left side is greater than the maximum additional yaw torque superimposed on the right side, that is, ΔM lmax >ΔMd rmax , then the torque scaling factor calculation formula is: The torque increase or decrease calculation formula for each motor is as follows: Where: ΔTd fl Indicates the torque increase or decrease performed by the left front motor; ΔTd fr Indicates the torque increase or decrease performed by the right front motor; ΔTd rl Indicates the torque increase or decrease performed by the left rear motor; ΔTd rr Indicates the torque increase or decrease performed by the right rear motor; The torque increase or decrease performed by each brake caliper is calculated as follows: Where: ΔTb fl Indicates the torque increase or decrease performed by the left front brake caliper; ΔTb fr Indicates the torque increase or decrease performed by the right front brake caliper; ΔTb rl Indicates the torque increase or decrease performed by the left rear brake caliper; ΔTb rr Indicates the amount of torque increase or decrease performed by the right rear brake caliper.

9. The yaw stability control method for a four-wheel drive vehicle according to claim 8, characterized in that: The target torque calculation formula of each motor and each brake caliper is as follows: Where: Td flout Indicates the target torque output by the left front motor; Td frout Indicates the target torque output by the right front motor; Td rlout Indicates the target torque output by the left rear motor; Td rrout Indicates the target torque output by the right rear motor; Tb flout Indicates the target torque output by the left front brake caliper; Tb frout Indicates the target torque output by the right front brake caliper; Tb rlout Indicates the target torque output by the left rear brake caliper; Tb rrout Indicates the target torque output by the right rear brake caliper.

10. A four-wheel drive vehicle, characterized in that: The four-wheel drive vehicle adopts the four-wheel drive vehicle yaw stability control method according to any one of claims 1 to 9.

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