A longitudinal and lateral coordinated control method for distributed drive electric vehicles

Abstract

The present invention discloses a method for coordinated longitudinal and lateral control of a distributed drive electric vehicle, comprising: step 1, collecting the real-time slip angle, longitudinal speed, accelerator pedal travel, and real-time acceleration of the vehicle tire; step 2, calculating the tire slip angle in real time and determining the working range of the slip angle; step 3, if the real-time slip angle of the tire is in the linear region, distributing the torque of the four wheels according to an optimization formula; if the real-time slip angle of the tire is in the saturation region, using the longitudinal force obtained at the inflection point as the limit value of the distribution to the wheel, and distributing the excess driving force to the remaining wheels, provided that the remaining tires are in the linear region; if the real-time slip angles of all four wheels of the vehicle are in the saturation region, outputting the four-wheel driving force according to the limit value obtained in the four-wheel linear region and adjusting the lateral controller to intervene to maintain vehicle stability. The present invention has the characteristics of improving the vehicle's responsiveness and lateral stability.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and more particularly to a longitudinal and lateral coordinated control method for a distributed drive electric vehicle. Background Art

[0002] The current control methods for adjusting the longitudinal and lateral directions of distributed drive vehicles are:

[0003] (1) Based on the lateral and longitudinal parameter characteristics of the vehicle in the stable area and the stability analysis of the dynamic area, a phase diagram is established or the stability limit boundary is divided. The control rules and controller are formulated according to the vehicle state to improve the stability of the vehicle.

[0004] (2) Establish observation models and model prediction methods to improve the accuracy of control quantity estimation, and then calculate the longitudinal force and lateral force of the vehicle tire based on the constraints and optimization conditions.

[0005] (3) In order to improve the control effect, the two are decoupled by adopting advanced algorithms such as genetic algorithms and fuzzy neural networks to address the cross-influence between the longitudinal and lateral directions of the vehicle.

[0006] However, the above methods are all relatively cumbersome and require a lot of basic equipment and preliminary experimental data. Summary of the Invention

[0007] The purpose of this invention is to design and develop a longitudinal and lateral coordinated control method for a distributed drive electric vehicle. By introducing two parameters, speed and road adhesion coefficient, a new distribution rule is formulated to optimize the longitudinal force distribution of the four-wheel tires, thereby improving the vehicle's responsiveness and lateral stability.

[0008] The technical solution provided by the present invention is:

[0009] A longitudinal and lateral coordinated control method for a distributed drive electric vehicle comprises the following steps:

[0010] Step 1: Collect the longitudinal speed, lateral speed, accelerator pedal travel, longitudinal acceleration and lateral acceleration of the vehicle tire;

[0011] Step 2: Establish a Dougff tire model, calculate the tire slip angle in real time, and determine the working range of the slip angle;

[0012] The working range includes a linear region and a saturation region;

[0013] Step 3: Obtaining four-wheel drive / braking torque based on lateral and longitudinal coordinated control;

[0014] Wherein, the horizontal and vertical coordinated control includes: an upper controller, a vertical controller and a horizontal controller;

[0015] The horizontal and vertical coordinated control rules are:

[0016] If the real-time side slip angle of the tire is in the linear region, the longitudinal force of the tire is distributed to the four wheels according to the optimization formula;

[0017] Wherein, the optimization formula is:

[0018]

[0019] Where, J w For the optimization goal, F xi is the driving / braking force of the i-th tire, F yi is the tire cornering force of the i-th tire, F Zi is the vertical load of the i-th tire, i = 1, 2, 3, 4, corresponding to the left front, right front, left rear, and right rear tires of the vehicle respectively;

[0020] The tire cornering force of the i-th tire satisfies:

[0021] F yi =0.131α i 5 -1.16×10 -16 α i 4 -12α i 3 -9.19×10 -16 α i 2 -246α i -6.22×10 -14

[0022] Where, α i is the sideslip angle of the i-th tire;

[0023] If the tire's real-time slip angle is in the saturation zone, the tire uses the longitudinal force at the extreme point of the slip angle as the limit value for the wheel distribution, and distributes the excess driving force to the remaining wheels, provided that the remaining tires are in the linear region.

[0024] If the real-time sideslip angles of all four wheels of the vehicle are in the saturation zone, the four-wheel drive force is output according to the limit values ​​obtained in the four-wheel linear region and the lateral controller is adjusted to intervene to maintain vehicle stability.

[0025] Preferably, the Dougff tire model is established by the formula:

[0026]

[0027]

[0028]

[0029]

[0030] Where, f(λ) is the function definition for judging the tire state, λ is the state coefficient value at this time, C y is the tire lateral cornering stiffness, C x is the tire longitudinal cornering stiffness, s i is the tire slip rate of the i-th tire, α i is the tire slip angle of the i-th tire, μ is the road adhesion coefficient, F Zi is the vertical load of the i-th tire.

[0031] Preferably, the linear region is a region where the slip angle is located before the tire cornering force reaches an extreme cornering force point, and the saturation region is a region outside the linear region.

[0032] Preferably, the longitudinal controller adjusts the driving / braking force of the tire to satisfy:

[0033] max(-μF Z1 ,-F m )≤F x1 ≤min(μF Z1 ,F m );

[0034] max(-μF Z2 ,-F m )≤F x2 ≤min(μF Z2 ,F m );

[0035] max(-μF Z3 ,-F m ,P1-F m ,P1-μF Z1 )≤F x3 ≤min(μF Z3 ,F m ,P1+F m ,P1+μF Z1 );

[0036] max(-μF Z4 ,-F m ,P2-F m ,P2-μF Z2 )≤F x4 ≤min(μF Z4 ,F m ,P2+F m ,P2+μF Z2 );

[0037] Where, F m is the maximum driving / braking force that the four-wheel motor can provide, and the value on the right side of the inequality is greater than or equal to the value on the left side of the inequality.

[0038] Preferably, the rule for adjusting the intervention of the lateral controller is:

[0039] If all four tires of the vehicle are in the linear region and meet the lateral stability formula, the vehicle is stable and the lateral controller does not intervene;

[0040] If the four tires of the vehicle are all in the linear region and do not meet the lateral steady-state formula, the upper controller controls the AFS controller in the lateral controller to intervene;

[0041] If any tire of the vehicle is in the saturated area and does not meet the lateral steady-state formula, the upper controller controls the AFS controller and DYC controller in the lateral controller, and the two controllers are controlled collaboratively according to the priority strategies set by the two.

[0042] Preferably, the lateral steady-state formula is:

[0043]

[0044] Where c1 is the first constant, c2 is the second constant, Δγ is the dynamic difference between the actual yaw rate and the desired yaw rate, σ is the third constant, β is the actual center of mass sideslip angle, is the actual center of mass sideslip angular velocity.

[0045] Preferably, when the AFS controller and the DYC controller are used for collaborative control, the priority strategy is:

[0046]

[0047] q dyc =1-q afs ;

[0048] Where q afs is the intervention proportional coefficient of the AFS controller, q dyc is the DYC controller intervention proportional coefficient, δ afs is the additional front wheel turning angle, δ afsmax is the limit adjustment value;

[0049] The additional front wheel angle and output direct yaw moment are obtained as:

[0050]

[0051] Where δ is the front wheel turning angle, M Z is the direct yaw moment, δafs is the additional front wheel steering angle, ΔM is the output direct yaw moment, N1 is the speed change rate of the AFS controller's state point moving to the switching surface, N is the speed change rate of the DYC controller's state point moving to the switching surface, sgn(·) is the sign function, S1 is the sliding film surface function of the AFS controller, S is the sliding film surface function of the DYC controller, and they satisfy:

[0052]

[0053] Where λ1 is the weight coefficient of the AFS controller, λ is the weight coefficient of the DYC controller, and both λ1 and λ are positive values. e1 is the control error of the AFS controller, and e is the control error of the DYC system.

[0054] The control error of the AFS controller and the control error of the DYC controller satisfy:

[0055] e1=K1×(γ-γ d );

[0056] e=K1×(γ-γ d )+K2×(β-β d );

[0057] Where K1 is the yaw rate weight coefficient, γ is the actual yaw rate, and γ d is the desired yaw rate, K2 is the weight coefficient of the center of mass sideslip angle, β d is the desired sideslip angle of the center of mass, and β is the actual sideslip angle of the center of mass.

[0058] Preferably, the yaw rate weight coefficient and the center of mass sideslip angle weight coefficient are both obtained by a fuzzy controller, and the control rule of the fuzzy controller is:

[0059] The input of the fuzzy controller is the vehicle speed vx and the road adhesion coefficient μ, and the output is the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2;

[0060] The physical domain of the vehicle speed vx is [0-126] km / h, the physical domain of the road adhesion coefficient μ is [0-1], and the domain of the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2 is [1-3];

[0061] The fuzzy domain of the vehicle speed vx is:

[0062] [VS, ZS, S, M, ZB, B, VB];

[0063] The fuzzy domain of the road adhesion coefficient μ is:

[0064] [VS, ZS, S, M, ZB, B, VB];

[0065] The fuzzy domain of the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2 is:

[0066] [PE, PZ, PS, PM, ZB, PB, PL].

[0067] Preferably, the step three further comprises:

[0068] Adjust the four-wheel additional torque to meet the following requirements:

[0069]

[0070] Where, T si The additional torque k is obtained to prevent the vehicle tire from excessively slipping. tp is the third proportional coefficient, k ti is the third integral coefficient, k td represents the third differential coefficient, ω f is the wheel angular velocity threshold, ω i is the actual angular velocity of the wheel, and the third proportional coefficient, the third integral coefficient and the third differential coefficient are all obtained from the PID model.

[0071] Preferably, the method further comprises step 4:

[0072] When the vehicle is traveling straight, no additional adjustments are made to the vehicle's four-wheel drive or braking forces;

[0073] When the vehicle turns left, if δ>0 and Δγ>0, the vehicle brakes the left rear wheel, and the braking torque is -T rl , drives the right front wheel of the vehicle, the driving torque is T fr ;

[0074] When the vehicle turns left, if δ>0 and Δγ<0, the vehicle brakes the right front wheel, and the braking torque is -T fr , driving the left rear wheel of the vehicle, the driving torque is T rl ;

[0075] When the vehicle turns right, if δ<0 and Δγ>0, the vehicle brakes the right rear wheel, and the braking torque is -T rr , driving the left front wheel of the vehicle, the driving torque is T rl ;

[0076] When the vehicle turns right, if δ<0 and Δγ<0, the vehicle brakes the right rear wheel, and the braking torque is -T rl , drives the right rear wheel of the vehicle, the driving torque is T rr .

[0077] Among them, T fl The DYC controller output adjusts the vehicle left front wheel driving / braking torque, T rlThe DYC controller output adjusts the vehicle left rear wheel driving / braking torque, T fr The DYC controller output adjusts the vehicle's right front wheel driving / braking torque, T rr Adjust the vehicle's right rear wheel driving / braking torque for the DYC controller output.

[0078] The beneficial effects of the present invention are:

[0079] The present invention designs and develops a longitudinal and lateral coordinated control method for a distributed drive electric vehicle. By introducing two parameters, speed and road adhesion coefficient, a new distribution rule is formulated to optimize the longitudinal force distribution of the four tires, and fuzzy control rules are established to meet the control focus of the vehicle in different states. Diagonal tire control rules are established to reduce the impact on driver behavior while minimizing the longitudinal speed loss of the vehicle to ensure the vehicle's economy, etc., and greatly improve the vehicle's responsiveness and lateral stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 Schematic diagram of the relationship curve between tire cornering force and sideslip angle under different road adhesion coefficients according to the present invention.

[0081] Figure 2 Schematic diagram of the area division of the vehicle sideslip angle according to the present invention.

[0082] Figure 3 This is a schematic diagram of the vehicle control process of the longitudinal and lateral coordinated control method of the distributed drive electric vehicle described in the present invention.

[0083] Figure 4 Schematic diagram of the flow of the longitudinal controller of the present invention.

[0084] Figure 5 Schematic diagram of the control strategy of the upper and lateral controllers of the present invention.

[0085] Figure 6 Schematic diagram of the membership function of the fuzzy controller input variables in the lateral controller of the present invention.

[0086] Figure 7 Schematic diagram of the membership function of the fuzzy controller output variable in the lateral controller of the present invention.

[0087] Figure 8 This is a diagram showing the relationship between the yaw rate weight coefficient and the output variable of the fuzzy controller of the present invention.

[0088] Figure 9 This is a schematic diagram of the relationship between the output variable of the fuzzy controller and the weight coefficient of the center of mass sideslip angle of the present invention.

[0089] Figure 10Schematic diagram of the double lane shifting experiment path in the embodiment of the present invention.

[0090] Figure 11 Schematic diagram of the yaw rate response curve under low adhesion coefficient according to the embodiment of the present invention.

[0091] Figure 12 Schematic diagram of lateral acceleration response curve under low adhesion coefficient of the embodiment of the present invention.

[0092] Figure 13 Schematic diagram of the sideslip angle response curve at a low adhesion coefficient in the embodiment of the present invention.

[0093] Figure 14 Schematic diagram of the yaw rate response curve under high adhesion coefficient of the embodiment of the present invention.

[0094] Figure 15 Schematic diagram of lateral acceleration response curve under high adhesion coefficient of the embodiment of the present invention.

[0095] Figure 16 Schematic diagram of the sideslip angle response curve at a high adhesion coefficient in the embodiment of the present invention. DETAILED DESCRIPTION

[0096] The present invention is described in further detail below so that those skilled in the art can implement the invention with reference to the description.

[0097] like Figure 1 、 Figure 2 、 Figure 3 As shown, the present invention provides a longitudinal and lateral coordinated control method for a distributed drive electric vehicle, including:

[0098] Step 1: Collect the longitudinal speed, lateral speed, accelerator pedal travel, longitudinal acceleration and lateral acceleration of the vehicle tire;

[0099] Step 2: Set the road adhesion coefficient to a constant value, establish the Dougff tire model, and calculate the side slip angle α of the inflection point. gu Calculate the cornering force F when this inflection point is reached gu and longitudinal force F xgu , through the size of each wheel's cornering angle, to determine the area where the tire's cornering force is located;

[0100] The Dougff tire model is established as follows:

[0101]

[0102]

[0103]

[0104]

[0105] Where, F yi is the tire cornering force of the i-th tire, F xi is the driving / braking force (longitudinal force) of the i-th tire, i=1,2,3,4, f(λ) is the function definition formula for judging the tire state, λ is the state coefficient value at this time, C y is the tire lateral cornering stiffness, C x is the tire longitudinal cornering stiffness, s i is the tire slip rate, α i is the tire slip angle, μ is the road adhesion coefficient, F Zi is the vertical load.

[0106] The calculation formula in the above formula is implemented under the premise that the tire slip angle, vertical load and slip rate are known quantities. Therefore, the tire slip angle, vertical load and slip rate need to be obtained. The slip angle is obtained by calculation, and the calculation formula for the vertical load is as follows:

[0107]

[0108] Where a is the distance from the front wheel to the center of mass, b is the distance from the rear wheel to the center of mass, l d is half of the front and rear wheelbase of the vehicle, m is the vehicle mass, g is the acceleration of gravity, h is the height of the center of mass, ax is the longitudinal acceleration, ay is the lateral acceleration, F Z1 is the vertical load on the left front wheel, F Z2 is the vertical load on the right front wheel, F Z3 is the vertical load on the left rear wheel, F Z4 is the vertical load on the right rear wheel;

[0109] The formula for calculating the sideslip angle is:

[0110]

[0111] Where α1 is the left front wheel slip angle, α2 is the right front wheel slip angle, α3 is the left rear wheel slip angle, α4 is the right rear wheel slip angle, vx is the longitudinal velocity of the vehicle, vy is the lateral velocity of the vehicle, and γ is the yaw rate of the vehicle.

[0112] The slip ratio meets the following requirements:

[0113]

[0114] Where, ω i Indicates the actual angular velocity of the wheel, s i is the wheel slip rate.

[0115] like Figure 1As shown in the figure, based on the Dougff tire model, characteristic curves of cornering force and slip angle are plotted for different road adhesion coefficients. Different road adhesion coefficients correspond to different maximum cornering force values. The greater the road adhesion coefficient, the greater the maximum cornering force the ground can provide to the tire, and the less likely the vehicle will skid. Therefore, on roads with good adhesion, the vehicle is more likely to maintain stability. On roads with poor adhesion, such as ice and snow, the vehicle is more likely to become unstable.

[0116] To solve the above problems, Figure 2 As shown in the figure, the area where the slip angle is located before the cornering force reaches the limit value is defined as the linear area. It can be seen that the cornering force and the slip angle are roughly linearly related in this area; when the slip angle exceeds the corresponding cornering force limit value, the cornering force remains basically unchanged. This area is defined as the saturation area. When the slip angle is in the saturation area, the ground cannot provide enough lateral force to the tire, causing the vehicle to slip and become unstable. Therefore, keeping the slip angle within the linear area can improve the stability of the vehicle on low-adhesion roads. Figure 1 As shown in FIG, the range of the linear region is different under different road adhesion coefficients. The larger the road adhesion coefficient, the larger the range of the linear region and the smaller the possibility of vehicle skidding.

[0117] According to the curve of cornering force-slip angle corresponding to the adhesion coefficient, the slope obtained by connecting the two inflection points (extreme points) and the horizontal and vertical coordinate values ​​corresponding to the inflection points are shown in Table 1.

[0118] Table 1 Slope and inflection point value of linear region under different road surface coefficients

[0119]

[0120] From Table (1), the cornering force slope fitting formula can be obtained as follows:

[0121] F yi =0.131α i 5 -1.16×10 -16 α i 4 -12α i 3 -9.19×10 -16 α i 2 -246α i -6.22×10 -14 (8)

[0122] Where, F yi is the cornering force of the i-th tire, α iis the slip angle of the i-th tire, i = 1, 2, 3, 4, corresponding to the left front, right front, left rear, and right rear tires of the vehicle respectively;

[0123] The cornering force corresponding to the slip angle under the current road adhesion coefficient is calculated using formula (8). A table is then used to determine whether the cornering force limit (inflection point value) is exceeded. This allows the working range of the slip angle to be determined, and the longitudinal forces on the four wheels are distributed according to the established rules.

[0124] Step 3: Figure 3 As shown, the control parameters are output by the upper controller, combined with the ideal linear two-degree-of-freedom vehicle model, and the four-wheel drive force F is obtained through the longitudinal controller and the lateral controller. i , additional front wheel turning angle δ afs , direct yaw moment ΔM and diagonal control rule to obtain the four-wheel adjustment torque T ij , and then through the steering system and four-wheel torque distribution layer, finally obtain the four-wheel drive / braking torque and front wheel angle that meet the current vehicle body stability;

[0125] Specifically, the upper-level controller obtains the four-wheel torque output by the longitudinal controller to the running feedback parameters of the whole vehicle model. According to the divided tire sideslip characteristic area, in order to meet the lateral stability requirements, when the vehicle is in the linear or saturated area, the lateral controller control parameters are output through the established lateral stability judgment formula. In order to meet the low-speed tracking and high-speed stability requirements of the vehicle when driving, according to the vehicle's yaw rate and center of mass sideslip angle, based on the fuzzy rule control strategy, two factor parameters of vehicle speed and road adhesion coefficient are introduced to dynamically determine the proportions K1 and K2 (K1 is the yaw rate weight coefficient, K2 is the center of mass sideslip angle weight coefficient) of the yaw rate and center of mass sideslip angle in the controller solution process, so that it can better maintain the focus requirements that need to be met when the vehicle is driving.

[0126] Among them, Figure 4 As shown, the longitudinal controller is established as follows:

[0127] The force applied by the driver to the accelerator pedal is converted into pedal travel, and the upper controller outputs the desired acceleration a rep and the desired speed v input by the driver rep , and the actual vehicle speed vx and acceleration ax are input into the PID control model to obtain the adjustment acceleration a that meets the current driver's expectations dos :

[0128]

[0129] Where k p is the first proportional integral, vx is the real-time longitudinal speed of the vehicle, k i is the first integral coefficient, kd is the first differential coefficient, k ap is the second proportional integral, ax is the real-time acceleration of the vehicle, k ai is the second integral coefficient, k ad is the second differential coefficient;

[0130] The expected acceleration is obtained by converting the accelerator pedal stroke, the expected speed is determined according to the driver's needs, and k p 、k i 、k d 、k ap 、k ai and k ad All are output by the PID control model.

[0131] The total driving force required by the current vehicle is calculated as follows:

[0132] F=m×ax-F w -F d -F f =ma dos (9)

[0133] Where F is the total driving force required by the vehicle, m is the vehicle mass, and F w is the air resistance, F d is the slope resistance, F f is the rolling resistance;

[0134] In this embodiment, only the rolling resistance of the vehicle on a uniform road surface is considered, and slope resistance and air resistance are ignored.

[0135] The driving / braking force distributed to the four wheels should meet the following requirements:

[0136] F x1 +F x2 +F x3 +F x4 =F=ma dos =m×ax-F f (10)

[0137] Where, F x1 , F x2 , F x3 , F x4 The driving / braking force of the left front, right front, left rear and right rear wheels of each independent electric drive;

[0138] From the perspective of road adhesion, the driving / braking force generated by each independent drive motor cannot exceed the maximum ground tangential force determined by the tire vertical load and the road adhesion coefficient, that is:

[0139] |F xi |≤μ i FZi (i=1~4)(11)

[0140] Where μ i is the road load coefficient of the i-th tire. If it is on a uniform road surface, its value is the same, F Zi is the vertical load of the i-th tire.

[0141] From the performance of the motor, the four-wheel drive torque should be less than the maximum value that the motor can provide, that is:

[0142] |F xi |≤F m (i=1~4)(12)

[0143] Where, F m The maximum driving / braking force that the four-wheel motor can provide;

[0144] The four-wheel drive torque must also meet the requirements for direct yaw torque:

[0145] l f (F x2 -F x1 )+l r (F x4 -F x3 )=ΔM(13)

[0146] Where, l f Half of the front axle track, l r is half of the rear axle track, ΔM is the output direct yaw moment, in this embodiment, the front wheel track and rear wheel track of the vehicle are equal, that is, l f =l r =l d .

[0147] Combining equations (11) and (14), we can obtain the following equation by using the elimination method:

[0148] F x1 =P1-F x3 (14)

[0149] F x2 =P2-F x4 (15)

[0150] Where P1 is the first intermediate parameter, P2 is the second intermediate parameter, and:

[0151]

[0152]

[0153] On a uniform road surface, the above four-wheel drive / braking force is limited. x1The constraints based on the road adhesion coefficient are:

[0154] -μF z1 ≤F x1 ≤μF z1 (19)

[0155] Where μ is the road adhesion coefficient;

[0156] Substituting formula (15) into formula (19) yields:

[0157] P1-μF Z1 ≤F x3 ≤P2+μF Z1 (20)

[0158] The driving / braking torque constraint of the motor's maximum driving / braking force on the left front wheel is expressed as:

[0159] -F m ≤F x1 ≤F m (twenty one)

[0160] Substituting formula (15) into formula (21), we get:

[0161] P1-F m ≤F x3 ≤P2+F m (twenty two)

[0162] Combined with the road adhesion and the maximum driving capacity of the motor, F x3 The constraints are:

[0163] max(-μF z3 ,-F m )≤F x3 ≤min(μF z3 ,F m )(twenty three)

[0164] Combining formula (20), formula (22), and formula (23) we can get F x3 The value range of is:

[0165] max(-μF Z3 ,-F m ,P1-F m ,P1-μF Z1 )≤F x3 ≤min(μF Z3 ,F m ,P1+F m ,P1+μF Z1 ) (twenty four)

[0167] Combined formula (12), (13) Fx1 The value range of is:

[0168] max(-μF Z1 ,-F m )≤F x1 ≤min(μF Z1 ,F m )(25)

[0169] Similarly, we can get F x2 , F x4 Value range:

[0170] max(-μF Z2 ,-F m )≤F x2 ≤min(μF Z2 ,F m )(26)

[0171] max(-μF Z4 ,-F m ,P2-F m ,P2-μF Z2 )≤F x4 ≤min(μF Z4 ,F m ,P2+F m ,P2+μF Z2 ) (27)

[0173] To ensure that the four-wheel drive / braking force value is not an empty set, the value on the right side of the inequality must be greater than or equal to the value on the left side.

[0174] The establishment of the upper controller and the horizontal controller:

[0175] After the upper controller is adjusted according to the longitudinal controller, in order to better improve the effects of the two controllers in the lateral controller, the active front wheel steering (AFS) controller and the direct yaw moment control (DYC) controller, the control strategy adopted is as follows: Figure 5 As shown, the vehicle steady-state formula is formulated to obtain the AFS controller coefficient q afs , according to q afs Determine the coordinated control coefficients corresponding to the DYC controller as q dycThe AFS controller calculates the additional front wheel steering angle, and the DYC controller controls the driving / braking torque of multiple wheels by calculating the direct yaw moment ΔM. This control strategy controller executes the longitudinal controller and lateral controller according to the real-time driving status of the vehicle. When the upper-level controller fails, it will not affect the normal operation of the longitudinal controller and lateral controller, greatly improving the reliability of various chassis control systems.

[0176] According to the tire status of the vehicle during driving, the control rules are formulated as follows:

[0177] (1) If all four tires of the vehicle are in the linear region and the lateral steady-state formula is satisfied at this time, the vehicle is stable and the lateral controller does not intervene;

[0178] The lateral steady-state formula is:

[0179]

[0180] Where c1 and c2 are constants. Based on the actual vehicle structural parameters, c1 = 0.079 and c2 = 0.035 are selected. Δγ is the dynamic difference between the actual yaw rate and the expected yaw rate. σ is a constant with an empirical value of 0.165. β is the actual sideslip angle of the center of mass. is the actual center of mass sideslip angular velocity.

[0181] (2) If all four tires of the vehicle are in the linear region and the lateral steady-state formula is not satisfied at this time, a single AFS controller in the lateral controller controlled by the upper controller intervenes;

[0182] (3) If any of the four tires of the vehicle is in the saturated area and does not meet the lateral steady-state formula, the AFS controller and DYC controller in the lateral controller controlled by the upper controller will be coordinated and controlled according to the priority strategies set by the two controllers.

[0183] Among them, the AFS controller in the lateral controller uses Δγ as the sliding mode control error to construct the sliding surface to restore the vehicle to stability. However, the adjustment ability of the AFS controller is limited. In order to improve the adjustment margin and expand the adjustable range, the DYC controller is used for supplementary adjustment. When the yaw rate and the sideslip angle of the center of mass do not satisfy the formula (28) during the vehicle driving process and meet the above control rule (3), the two controllers need to adjust together. However, since the AFS controller will gradually exit when it exceeds the threshold, its threshold is set to 80% of the limit adjustment value, and its intervention proportional coefficient q afs for:

[0184]

[0185] In this embodiment, the limit adjustment value is 5°.

[0186] For the DYC controller, the two controller coefficients are assumed to satisfy:

[0187] q dyc =1-q afs (30)

[0188] The timing of horizontal control intervention and the size of intervention coefficient are given by formula (29) and formula (30).

[0189] The establishment process of AFS controller and DYC controller is as follows:

[0190] The AFS controller is based on the sliding mode control principle. The difference between the actual yaw rate and the desired yaw rate is selected as the control error e1 of the AFS controller. When the fuzzy control rule is introduced, the control error satisfies:

[0191] e1=K1×(γ-γ d ) (31)

[0192] Based on the sliding mode principle, the DYC controller selects the difference between the actual yaw rate and the desired yaw rate, and the difference between the actual center of mass sideslip angle and the desired center of mass sideslip angle as the control error e of the DYC system. Combined with fuzzy control, the following is obtained:

[0193] e=K1×(γ-γ d )+K2×(β-β d ) (32)

[0194] Where K1 is the yaw rate weight coefficient, K2 is the center of mass sideslip angle weight coefficient;

[0195] From the ideal linear two-degree-of-freedom vehicle model, the expected yaw rate γ of the vehicle is derived d and the desired sideslip angle β d .

[0196] The two sliding film surfaces constructed both adopt the integral sliding mode, namely:

[0197]

[0198] Where: S1 is the sliding surface function of the AFS controller, S is the sliding surface function of the DYC controller, λ1 is the weighting coefficient of the AFS controller, λ is the weighting coefficient of the DYC controller, and λ1 and λ are both positive values.

[0199] Derivative of Equation (33) and combining it with the ideal linear two-degree-of-freedom state space equation, we can get Substituting, we get the front wheel angle δ and direct yaw moment M Z The equivalent control expression, combined with the sliding membrane surface function, finally obtains the additional front wheel turning angle δ afs The output direct yaw moment ΔM is expressed as:

[0200]

[0201] Where N1 and N are the speed change rates of the state point moving to the switching surface of the AFS controller and the DYC controller, respectively, and sgn(·) is the sign function.

[0202] Therefore, by combining the two controller coefficients solved by the upper controller, the final additional front wheel angle and direct yaw moment formula are obtained as follows:

[0203]

[0204] At this time, δ afs and ΔM are the additional front wheel steering angle and direct yaw moment finally output by the system.

[0205] To meet the requirements of lateral focus, based on the vehicle's yaw rate and center of mass sideslip angle, a fuzzy rule control strategy is introduced, with the vehicle speed and road adhesion coefficient as two factor parameters. The proportions K1 and K2 of the yaw rate and center of mass sideslip angle in the controller solution are dynamically determined, so that the vehicle's lateral stability focus can be better maintained. The establishment process is as follows:

[0206] The physical domain of speed vx is [0-126] km / h; the speed unit conversion value range is [0-35], the physical domain of road adhesion coefficient μ is [0-1], and the domain of weight values ​​K1 and K2 is [1-3];

[0207] The fuzzy domain of the longitudinal vehicle speed vx is:

[0208] [VS (very small); ZS (medium small); S (small); M (medium); ZB (medium large); B (large); VB (very large)]

[0209] The fuzzy domain of the road adhesion coefficient μ is:

[0210] [VS (very small); ZS (medium small); S (small); M (medium); ZB (medium large); B (large); VB (very large)]

[0211] The fuzzy domain of K1 and K1 is:

[0212] [PE (very small); PZ (medium small); PS (small); PM (medium); ZB (medium large); PB (large); PL (limit value)]

[0213] like Figure 6 、 Figure 7 As shown in Table 2, Table 3 are the control rule tables for the yaw rate weight coefficient and the center of mass sideslip angle weight coefficient.

[0214] Table 2 Yaw angular velocity weight coefficient control rules

[0215]

[0216] Table 3. Rules for weight coefficient of center of mass sideslip angle

[0217]

[0218] like Figure 8 、 Figure 9 As shown in the figure, the establishment of the fuzzy rules is based on the vehicle speed vx and the road adhesion coefficient μ, and the rule operation is as follows: for the size of the yaw rate weight coefficient K1, when vx is in a medium-high speed (45-126 km / h) and the μ value is large (0.5-1), the output K1 is also relatively large (1.8-3); when it is in a low speed (0-45 km / h) and the adhesion is low (0-0.5), K1 is small (1-1.8), and the lateral controller focuses on stability control; for the size of the center of mass sideslip angle weight coefficient K2, when vx is in a medium-low speed (0-45 km / h) and the μ value is large (1.9-3), the output K2 is also relatively large (1.9-3); when it is in a high speed (45-126 km / h) and the adhesion is low (0-0.5), K2 is small (1-1.9), and the lateral controller focuses on tracking control.

[0219] If the real-time side slip angle of the tire is in the linear region, the longitudinal force of the tire is distributed to the four wheels according to the established optimization formula;

[0220] If the tire's real-time slip angle exceeds the inflection point slip angle (slip angle limit), that is, it is in the saturation zone, the longitudinal force obtained at the inflection point is used as the limit value for the tire's distribution. A constraint is added to the magnitude of the longitudinal force in the optimization formula, and the excess driving force is distributed to the remaining wheels, provided that the remaining tires are in the linear region.

[0221] Taking the left front wheel as an example, the longitudinal force of the tire of the left front wheel satisfies:

[0222] min(-F m , -F xgu )≤F x1 ≤min(F m ,F xgu ) (36)

[0223] Where, F m F is the maximum driving / braking force that the four-wheel motor can provide. x1 is the longitudinal force of the tire on the left front wheel;

[0224] The current tire cornering force limit is:

[0225] -F gu ≤F y1 ≤F gu (37)

[0226] Where, F y1 is the cornering force of the left front wheel;

[0227] If the four wheels of the vehicle cannot meet the distribution of driving force, the four-wheel driving force will be output according to the limit value obtained in the four-wheel linear area. At this time, the main focus is on meeting the utilization rate of the vehicle tires. If there is lateral instability, the lateral controller will intervene to restore the vehicle to stability.

[0228] Wherein, the optimization formula is:

[0229]

[0230] Where, J w For the optimization goal, F yi is the tire cornering force of the i-th tire, which is placed in the denominator of each term and takes into account the road load coefficient μ when expressing the maximum tangential force of the road i In the optimization objective, F xi The value of F is used as the object of optimization allocation, without yi The values ​​of are constrained and distributed, which conforms to the characteristics of the studied four-wheel independent electric drive chassis.

[0231] When F yi When the load increases, the road adhesion load of all wheels of the vehicle also increases. The coefficient before Also increases, so in the subsequent optimization allocation process F xi The calculated value of the distribution will be suppressed; similarly, when i When decreasing, The coefficient before will also increase, so F xi The distribution calculation value will also be suppressed, thereby realizing the design concept of a higher adhesion load coefficient for low-adhesion roads.

[0232] The tire lateral force and vertical load are directly provided by Carsim 2019 software. The constrained optimization problem is solved by substituting equations (15) and (16) into (38) and eliminating F. x1 and F x2 get:

[0233]

[0234] After eliminating the variables in equation (39), it can be decomposed into the sum of two independent quadratic functions, which are:

[0235]

[0236]

[0237] Where, J w1 is the first intermediate optimization objective, J w2 is the second intermediate optimization objective;

[0238] Perform two quadratic function minimization operations on equations (40) and (41) respectively to achieve the optimization goal J w Minimum value problem.

[0239] Targeting J w1 ,get:

[0240]

[0241] Where a w0 is the first optimization weight, a w1 is the second optimization weight, a w2 Optimize weights for the third;

[0242]

[0243]

[0244]

[0245] J w1 The axis of symmetry is:

[0246]

[0247] For F x3 Constraint range, let:

[0248] mean1=min(μF Z3 ,F m ,P1+F m ,P1+μF Z1 )(47)

[0249] mean2=max(-μF Z3 ,-F m ,P1-F m ,P1-μF Z1 )(48)

[0250] Where, mean1 is the first intermediate function, mean2 is the second intermediate function;

[0251] (1) When the symmetry axis satisfies:

[0252]

[0253] At this time, J w1 The minimum value of is:

[0254] J w1min =J w1 (mean1) (50)

[0255] At this point, there are:

[0256]

[0257] (2) When the symmetry axis satisfies:

[0258]

[0259] At this time, J w1 The minimum value of is:

[0260]

[0261] At this point, we get:

[0262]

[0263] (3) When the symmetry axis satisfies:

[0264]

[0265] At this time, J w1 The minimum value of is:

[0266] J w1min =J w1 (mean2) (56)

[0267] At this point, we get:

[0268]

[0269] With the above judgment conditions, the optimized F x1 and F x3 The driving / braking force can be calculated by the same method. x2 and F x4 The value is the size of the four-wheel drive force F xi .

[0270] At the same time, if the wheel slip is too large, the lateral adhesion coefficient of the wheel will be greatly reduced, resulting in poor vehicle stability. Therefore, it is necessary to design a slip rate controller. The slip rate threshold is 15%, denoted as S. f=15%. When the actual wheel slip is greater than the slip threshold, it is considered that the wheel has excessive slip, and the slip controller based on the PID control method intervenes. Otherwise, the wheel is considered normal, and the slip controller does not intervene. The four-wheel additional torque to prevent excessive slip is obtained:

[0271]

[0272] Where, T si The additional torque k is obtained to prevent the vehicle tire from excessively slipping. tp is the third proportional coefficient, k ti is the third integral coefficient, k td represents the third differential coefficient, ω f is the wheel angular velocity threshold, ω i is the actual angular velocity of the wheel;

[0273] After obtaining the wheel speed, it is converted into angular velocity. Therefore, the wheel angular velocity can be equivalently used as the control variable. The wheel angular velocity threshold corresponding to the slip rate threshold is:

[0274]

[0275] Where, ω f is the wheel angular velocity threshold, R is the wheel rotation radius;

[0276] The four-wheel drive / braking force F obtained by the optimization strategy xi , adjusting torque T to prevent excessive slip si , input moment distribution layer.

[0277] Step 4: Based on the independent controllability of each wheel in a distributed drive electric vehicle, the dynamic difference Δγ between the actual and desired yaw angular velocity and the front wheel steering angle δ are used as inputs to the logic controller to determine understeering and oversteering during vehicle steering. To better improve controllability and optimize driving behavior, a diagonal two-wheel control strategy is adopted as shown in Table 4:

[0278] Table 4 Wheel control rules

[0279]

[0280]

[0281] In combination with the wheel control rules in Table 4, when the vehicle is moving straight, that is, when the front wheel angle is 0, no additional adjustment is applied to the vehicle's four-wheel drive or braking force.

[0282] When the DYC controller starts to intervene, it determines the current values ​​of δ and Δγ, and calculates the required controlled wheels based on the values ​​of the above two parameters, and then calculates the magnitude of the applied torque.

[0283] When the vehicle turns left, the conditions of δ>0, Δγ>0 are met. At this time, the vehicle is oversteering, so the left rear wheel is braked, and the braking torque is -T. rl In order to compensate for the longitudinal speed loss and correct the yaw moment, a driving torque T is given to the right front wheel of the vehicle. fr , allowing the vehicle to reduce longitudinal speed loss while maintaining lateral stability.

[0284] Similarly, when the vehicle turns left, the conditions of δ>0, Δγ<0 are met, the vehicle is understeering, and the right front wheel is braked with a magnitude of -T fr , giving the vehicle's left rear wheel a driving torque T rl .

[0285] Similarly, when the vehicle turns right, the conditions of δ<0, Δγ>0 are met. At this time, the vehicle is over-steering, so the right rear wheel is braked with a force of -T. rr , giving the vehicle's left front wheel a driving torque T rl .

[0286] Similarly, when the vehicle turns right, the conditions of δ<0, Δγ<0 are met. At this time, the vehicle is understeering, so the left front wheel is braked with a magnitude of -T. rl , giving the right rear wheel of the vehicle a driving torque T rr .

[0287] In the set rules: T fl 、T rl 、T fr 、T rr The DYC controller outputs respectively adjust the driving / braking torque of the vehicle's left front, left rear, right front, and right rear wheels.

[0288] According to the tire friction ellipse principle:

[0289] F xi 2 +F yi 2 ≤μ 2 F Zi 2 (60)

[0290] Where, F xi is the tire longitudinal force, F yi is the tire lateral force, F Zi is the vertical load of the tire;

[0291] Therefore, when distributing the driving / braking force, the following conditions must be met:

[0292]

[0293] The yaw moment generated by the four wheels during distribution is calculated as follows:

[0294]

[0295] Where M Zfl Yaw moment distributed to the left front wheel, M Zfr Yaw moment distributed to the right front wheel, M Zrl Yaw moment distributed to the left rear wheel, M Zrr Yaw moment distributed to the right rear wheel.

[0296] According to the vertical loads on the front and rear axles, the additional yaw moment distributed to the diagonal two wheels is expressed as follows:

[0297]

[0298] Where a and b are the distances from the center of mass to the front and rear axles, respectively, and l is the wheelbase;

[0299] The torque size of the four-wheel distribution is calculated by formula (63).

[0300] The sign of the yaw moment is determined by combining the controlled rules in Table 4, and the diagonal wheel driving / braking adjustment torque for correcting the yaw moment is finally output.

[0301] The double lane change test simulation environment is set up in the software Carsim2019. The double lane change test path is as follows: Figure 10 As shown in the figure, the road adhesion coefficients in the double lane change test simulation conditions are selected as a low adhesion coefficient road surface of 0.45 and a high adhesion coefficient road surface of 0.85, and the constant speed is set to 80 km / h. In order to verify the diagonal two-wheel drive / brake coordinated control (indicated by the solid line) adopted by the present invention and the independent action without coordination (indicated by the dotted line), the simulation analysis results are compared as shown in the curve. Figures 11 to 16 As shown in Figure 3, the low-high attachment test results show that the cooperatively controlled vehicle has better lateral stability than the independently controlled vehicle.

[0302] This invention designs and develops a coordinated longitudinal and lateral control method for distributed drive electric vehicles. To ensure longitudinal speed, the longitudinal controller optimizes allocation strategies and proposes a rule based on the slip angle-cornering force characteristics under different road adhesion coefficients. This rule prioritizes longitudinal speed optimization within the linear region and lateral stability within the saturated region. These two judgment and allocation rules ensure a rational distribution of longitudinal forces across the vehicle's four wheels. Furthermore, the independent controllability of each wheel in a distributed vehicle maximizes tire utilization and adaptively adjusts tire characteristics to enhance vehicle stability. The established lateral judgment formula determines when the lateral stability controller intervenes. Fuzzy rules are used to weight low-speed-center-of-mass slip angle and speed-yaw rate, enabling the lateral controller to adapt to vehicle priorities at different speeds and road conditions, improving driver comfort and stability. While ensuring lateral stability, a direct yaw moment wheel diagonal braking strategy is developed to compensate for longitudinal speed. And through the four-wheel control rules of diagonal wheel driving or braking, the vehicle's responsiveness and lateral stability performance are improved as much as possible while reducing the impact on driver behavior and reducing the vehicle's longitudinal speed.

[0303] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for longitudinal and transverse coordinated control of a distributed drive electric vehicle, characterized in that: The steps include: Step 1: Collect the longitudinal speed, lateral speed, accelerator pedal travel, longitudinal acceleration and lateral acceleration of the vehicle tire; Step 2: Establish a Dugoff tire model, calculate the tire slip angle in real time, and determine the working range of the slip angle; The working range includes a linear region and a saturation region; Step 3: Obtaining four-wheel drive / braking torque based on lateral and longitudinal coordinated control; Wherein, the horizontal and vertical coordinated control includes: an upper controller, a vertical controller and a horizontal controller; The horizontal and vertical coordinated control rules are: If the real-time side slip angle of the tire is in the linear region, the longitudinal force of the tire is distributed to the four wheels according to the optimization formula; Wherein, the optimization formula is: Where, J w For the optimization goal, F xi is the driving / braking force of the i-th tire, F yi is the tire cornering force of the i-th tire, F Zi is the vertical load of the i-th tire, i = 1, 2, 3, 4, corresponding to the left front, right front, left rear, and right rear tires of the vehicle respectively; The tire cornering force of the i-th tire satisfies: F yi ＝0.131α i 5 -1.16×10 -16 α i 4 -12α i 3 -9.19×10 -16 α i 2 -246α i -6.22×10 -14 Where, α i is the sideslip angle of the i-th tire; If the tire's real-time slip angle is in the saturation zone, the tire uses the longitudinal force at the extreme point of the slip angle as the limit value for the wheel distribution, and distributes the excess driving force to the remaining wheels, provided that the remaining tires are in the linear region. If the real-time sideslip angles of all four wheels of the vehicle are in the saturation zone, the four-wheel drive force is output according to the limit values ​​obtained in the four-wheel linear region and the lateral controller is adjusted to intervene to maintain vehicle stability.

2. The longitudinal and lateral coordinated control method of a distributed drive electric vehicle according to claim 1, characterized in that: The formula for establishing the Dugoff tire model is: Where, f(λ) is the function definition for judging the tire state, λ is the state coefficient value at this time, C y is the tire lateral cornering stiffness, C x is the tire longitudinal cornering stiffness, s i is the tire slip rate of the i-th tire, α i is the tire slip angle of the i-th tire, μ is the road adhesion coefficient, F Zi is the vertical load of the i-th tire.

3. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 2, characterized in that: The linear region is the region where the slip angle is located before the tire cornering force reaches the extreme cornering force point, and the saturation region is the region outside the linear region.

4. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 3, characterized in that: The longitudinal controller adjusts the driving / braking force of the tire to satisfy: max(-μF Z1 ,-F m )≤F x1 ≤min(μF Z1 ,F m ); max(-μF Z2 ,-F m )≤F x2 ≤min(μF Z2 ,F m ); max(-μF Z3 ,-F m ,P1-F m ,P1-μF Z1 )≤F x3 ≤min(μF Z3 ,F m ,P1+F m ,P1+μF Z1 ); max(-μF Z4 ,-F m ,P2-F m ,P2-μF Z2 )≤F x4 ≤min(μF Z4 ,F m ,P2+F m ,P2+μF Z2 ); Where, F m is the maximum driving / braking force that the four-wheel motor can provide, and the value on the right side of the inequality is greater than or equal to the value on the left side of the inequality.

5. The longitudinal and lateral coordinated control method of a distributed drive electric vehicle according to claim 4, characterized in that: The rule for regulating the intervention of the lateral controller is: If all four tires of the vehicle are in the linear region and meet the lateral stability formula, the vehicle is stable and the lateral controller does not intervene; If the four tires of the vehicle are all in the linear region and do not meet the lateral steady-state formula, the upper controller controls the AFS controller in the lateral controller to intervene; If any tire of the vehicle is in the saturated area and does not meet the lateral steady-state formula, the upper controller controls the AFS controller and DYC controller in the lateral controller, and the two controllers are controlled collaboratively according to the priority strategies set by the two.

6. The longitudinal and lateral coordinated control method of a distributed drive electric vehicle according to claim 5, characterized in that: The lateral steady-state formula is: Where c1 is the first constant, c2 is the second constant, Δγ is the dynamic difference between the actual yaw rate and the desired yaw rate, σ is the third constant, β is the actual center of mass sideslip angle, is the actual center of mass sideslip angular velocity.

7. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 6, characterized in that: When the AFS controller and the DYC controller are used in collaboration, the priority strategy is: q dyc =1-q afs ; Where q afs is the intervention proportional coefficient of the AFS controller, q dyc is the DYC controller intervention proportional coefficient, δ afs is the additional front wheel turning angle, δ afsmax is the limit adjustment value; The additional front wheel angle and output direct yaw moment are obtained as: Where δ is the front wheel angle, M Z is the direct yaw moment, δ afs is the additional front wheel steering angle, ΔM is the output direct yaw moment, N1 is the speed change rate of the AFS controller's state point moving to the switching surface, N is the speed change rate of the DYC controller's state point moving to the switching surface, sgn(·) is the sign function, S1 is the sliding film surface function of the AFS controller, S is the sliding film surface function of the DYC controller, and they satisfy: Where λ1 is the weight coefficient of the AFS controller, λ is the weight coefficient of the DYC controller, and both λ1 and λ are positive values. e1 is the control error of the AFS controller, and e is the control error of the DYC system. The control error of the AFS controller and the control error of the DYC controller satisfy: e1=K1×(γ-γ d ); e=K1×(γ-γ d )+K2×(β-β d ); Where K1 is the yaw rate weight coefficient, γ is the actual yaw rate, and γ d is the desired yaw rate, K2 is the weight coefficient of the center of mass sideslip angle, β d is the desired sideslip angle of the center of mass, and β is the actual sideslip angle of the center of mass.

8. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 7, characterized in that: The yaw rate weight coefficient and the center of mass sideslip angle weight coefficient are both obtained by a fuzzy controller, and the control rule of the fuzzy controller is: The input of the fuzzy controller is the vehicle speed vx and the road adhesion coefficient μ, and the output is the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2; The physical domain of the vehicle speed vx is [0-126] km / h, the physical domain of the road adhesion coefficient μ is [0-1], and the domain of the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2 is [1-3]; The fuzzy domain of the vehicle speed vx is: [VS, ZS, S, M, ZB, B, VB]; The fuzzy domain of the road adhesion coefficient μ is: [VS, ZS, S, M, ZB, B, VB]; The fuzzy domain of the yaw rate weight coefficient K1 and the center of mass sideslip angle weight coefficient K2 is: [PE, PZ, PS, PM, ZB, PB, PL].

9. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 8, characterized in that: The step three also includes: Adjust the four-wheel additional torque to meet the following requirements: Where, T si The additional torque k is obtained to prevent the vehicle tire from excessively slipping. tp is the third proportional coefficient, k ti is the third integral coefficient, k td represents the third differential coefficient, ω f is the wheel angular velocity threshold, ω i is the actual angular velocity of the wheel, and the third proportional coefficient, the third integral coefficient and the third differential coefficient are all obtained from the PID model.

10. The longitudinal and transverse coordinated control method of a distributed drive electric vehicle according to claim 9, characterized in that: Also includes step four: When the vehicle is traveling straight, no additional adjustments are made to the vehicle's four-wheel drive or braking forces; When the vehicle turns left, if δ>0 and Δγ>0, the vehicle brakes the left rear wheel, and the braking torque is -T rl , drives the right front wheel of the vehicle, the driving torque is T fr ; When the vehicle turns left, if δ>0 and Δγ<0, the vehicle brakes the right front wheel, and the braking torque is -T fr , driving the left rear wheel of the vehicle, the driving torque is T rl ; When the vehicle turns right, if δ<0 and Δγ>0, the vehicle brakes the right rear wheel, and the braking torque is -T rr , driving the left front wheel of the vehicle, the driving torque is T rl ; When the vehicle turns right, if δ<0 and Δγ<0, the vehicle brakes the right rear wheel, and the braking torque is -T rl , drives the right rear wheel of the vehicle, the driving torque is T rr； Among them, T fl The DYC controller output adjusts the vehicle left front wheel driving / braking torque, T rl The DYC controller outputs the driving / braking torque of the vehicle’s left rear wheel, T fr The DYC controller output adjusts the vehicle right front wheel driving / braking torque, T rr Adjust the vehicle's right rear wheel driving / braking torque for the DYC controller output.

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