A method for distributing torque in a distributed drive vehicle without road adhesion information perception

Abstract

The application discloses a kind of road surface adhesion information perception-free distributed drive vehicle torque distribution methods, specifically related to distributed drive vehicle drive torque distribution technical field, first acquire vehicle state information and upper control demand, and combine tire vertical load to calculate each wheel initial torque;According to the slip / slip rate design anti-skid torque control law, and estimate the value range of each wheel torque;By analyzing feasible region, the satisfaction of the value range of each wheel torque to upper control demand is judged, and a kind of hierarchical constraint quadratic programming method is designed to optimize each wheel compensation torque;According to each wheel initial torque and anti-skid torque and compensation torque, each wheel expected torque is obtained.For the problem that road adhesion coefficient is difficult to accurately observe under small excitation and composite working condition, the method proposed in the application can maximize the stability and maneuverability of the vehicle without road surface adhesion information perception, and reduce the conflict between torque vector distribution system and anti-skid system and other functions.

Description

Technical Field

[0001] This invention relates to the field of distributed drive vehicle torque distribution technology, specifically to a distributed drive vehicle torque distribution method without road surface adhesion information sensing. Background Technology

[0002] Distributed drive vehicles utilize in-wheel motors or wheel-side motors to control driving force, enabling precise, rapid, and stable execution of vehicle electronic control system commands. This achieves superior performance and safety goals, providing users with a more comfortable, safe, and convenient driving experience, thus possessing enormous application potential. Currently, active safety technologies applied to distributed drive vehicle chassis mainly include Active Front Steering (AFS), Direct Yaw Curve Control (DYC), and Electronic Stability Program (ESP). Multiple subsystems can fully leverage the overdrive characteristics of distributed drive vehicles, allowing them to meet control requirements under more operating conditions. However, with the increase in subsystems, the complexity and coupling of the chassis control system also increase. Inappropriate or imperfect control strategies often lead to functional conflicts between subsystems, ultimately weakening overall vehicle performance. In existing distributed drive vehicle chassis coordinated control, most studies, after coordinating the control of DYC and other systems such as AFS, use the obtained desired steering angle and yaw moment to perform quadratic programming to distribute the torque of each wheel through adhesion constraints. However, they do not consider the functional conflicts that arise when the anti-slip system in ESP participates in torque control. Since DYC and anti-slip system control often start working when approaching the extreme conditions, they cannot guarantee the stability and handling of the whole vehicle under extreme conditions. Therefore, when distributing torque, it is also necessary to design a coordination strategy between DYC and other subsystems and the anti-slip system.

[0003] Existing torque distribution methods for distributed drive vehicles, such as quadratic programming, axle load distribution, and other coordinated distribution methods, heavily rely on accurate road adhesion coefficients. However, high-precision real-time observation of road adhesion coefficients, especially under low-excitation and complex operating conditions, is very difficult. Furthermore, when distributing torque in a distributed drive vehicle, it is necessary to obtain relevant information for each wheel. When the road adhesion coefficients of the four wheels are inconsistent, it is even more difficult to observe the road adhesion coefficient of each wheel in real time. Therefore, torque distribution methods that rely on accurate road adhesion coefficients cannot guarantee accuracy and practicality under various harsh operating conditions. Summary of the Invention

[0004] Therefore, the present invention provides a distributed drive vehicle torque distribution method without road surface adhesion information perception to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a distributed drive vehicle torque distribution method without road surface adhesion information perception, comprising the following steps:

[0006] Step 1: Real-time acquisition of status information, including the vehicle's longitudinal speed, longitudinal acceleration, yaw rate, center of gravity sideslip angle, speed of each tire, and the desired front wheel steering angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller;

[0007] Step 2: Calculate the initial torque of the four wheels based on the vertical load of the tires according to the vehicle status information;

[0008] Step 3: Calculate the slip / slip ratio and anti-slip torque of each wheel based on the vehicle status information;

[0009] Step 4: Determine the inequality constraints of the torque of each wheel based on the anti-slip torque, vertical load, initial torque, and compensation torque of each wheel.

[0010] Step 5: Determine whether the inequality constraints of each wheel torque satisfy the additional yaw moment requirement and the total longitudinal force requirement by analyzing the feasible region.

[0011] Step Six: Design a hierarchical constrained quadratic programming method with the compensation torque of each wheel as the optimization variable;

[0012] Step 7: Solve the quadratic programming problem established in Step 6 to obtain the compensation torque for each wheel;

[0013] Step 8: Calculate the desired torque based on the initial torque, anti-slip torque, and compensation torque of each wheel.

[0014] Preferably, the specific calculation method for step two is as follows: first, calculate the vertical load F of the four wheels based on the vehicle status information. zi Then, based on the tire vertical load F zi Solve for the initial longitudinal force F of the four tires. pxi To optimize the variables, minimize the longitudinal force F of the tire. px Vertical load F of tire zi The problem is a quadratic programming problem with the sum of squares of the proportions J as the optimization objective, the desired total longitudinal force and the desired additional yaw moment as constraints, and the road adhesion force limit. Solving the quadratic programming problem yields the initial longitudinal force F. pxi Then, the initial torque T of the four wheels is calculated using the tire radius. pi .

[0015] Preferably, the calculation process for the slip / slip ratio of each wheel in step three is as follows:

[0016] Based on the obtained longitudinal velocity of the vehicle, calculate the horizontal velocity vector v at the wheel center. i :

[0017] v i =v c+ω r ×x i ;

[0018] In the formula, v c The horizontal velocity vector representing the vehicle's center of mass requires information about the longitudinal velocity, ω. r The vector representing the vehicle's yaw rate, x i This represents the projection vector of the vector originating from the vehicle's center of mass and ending at the center of the wheel onto the horizontal plane.

[0019] Based on the horizontal velocity vector v at the center of the wheel i Calculate the horizontal velocity v of the wheel when it is rolling in pure motion. pi :

[0020] v pi =v i ·(cosδ i ,sinδ i ,0);

[0021] In the formula, δ i Indicates the turning angle of the wheel;

[0022] Based on the horizontal velocity v of the wheel during pure rolling pi Calculate the wheel slip / slip ratio λ i :

[0023]

[0024] In the formula, the linear velocity of the tire is v = ω i r, ω i R is the tire rotation speed, and r is the tire radius.

[0025] The anti-slip torque T of the wheel in step three asi The calculation formula is as follows:

[0026]

[0027] In the formula, λ u λ represents the maximum permissible wheel slip ratio. l λ represents the minimum permissible wheel slip ratio. i , Let k be the wheel slip / slip ratio and its derivative with respect to time. pi ,K pi ,k di ,K di ,h i H i ,c i C iTo control the increase and ensure all values ​​are greater than 0, `sat()` is a saturation function. Preferably, the specific method for determining the inequality constraint of the wheel torque in step four is as follows:

[0028] Determine the anti-slip torque T of the wheel at the current moment. asi Whether (k) is 0, the anti-slip torque T of the wheel at the current moment. asi When (k) is 0, the wheel torque T i The inequality constraints for (k) are as follows:

[0029] |T i (k)|≤min{T mi (k),T ui (k)};

[0030] In the formula, T i (k) represents the wheel torque, where i takes the value 1 or 2, representing the torque of the left front wheel and the right front wheel respectively; k represents the current time; T mi (k) represents the maximum wheel torque determined by the operating characteristics of the drive motor at the current moment, T. ui (k) is the maximum wheel torque determined by tire adhesion at the current moment, and satisfies:

[0031] T ui (k)=min{F zi (k)r,T ui (k-1)+T r};

[0032] In the formula, F zi (k) represents the vertical load on the wheel at the current moment, r is the wheel radius, and T ui (k-1) represents the maximum wheel torque determined by tire adhesion at the previous moment, T r To restore torque;

[0033] The anti-slip torque T of the wheel at the current moment asi When (k) is not 0, the wheel torque T i The inequality constraints for (k) are as follows:

[0034] |T i (k)|≤min{T mi (k),T ui (k)};

[0035] In the formula, T mi (k) represents the maximum wheel torque determined by the operating characteristics of the drive motor at the current moment, T. ui (k) is the maximum wheel torque determined by tire adhesion at the current moment, and satisfies:

[0036] T ui(k)=|T pi (k-1)+T ci (k-1)-T asi (k)|;

[0037] In the formula, T pi (k-1) represents the initial torque of the wheel at the previous moment, T ci (k-1) represents the compensation torque of the wheel at the previous moment.

[0038] Preferably, the specific method for determining whether the inequality constraints of each wheel torque satisfy the additional yaw moment requirement and the total longitudinal force requirement by analyzing the feasible region in step five is as follows:

[0039] The additional yaw moment requirement W is analytically calculated within the two-dimensional feasible region formed by the torques of the left and right front wheels, T1 and T2. M T=rΔM d Total longitudinal force requirement W F T = rF xsumd The four boundary lines L formed e1 ,L e2 ,L e3 ,L e4 Among them, W F =[cosδ f cosδ f 1 1],

[0040] W M =[asinδ f -lcosδ f asinδ f +lcosδ f -ll],δ f Desired front wheel steering angle:

[0041]

[0042] Simultaneously obtain the four boundary vertices p generated by the intersection of the four boundary lines. e1 ,p e2 ,p e3 ,p e4 The coordinates are analytically calculated within the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2, based on the range of the left front wheel torque T1: |T1|≤min{T m1 ,T u1 The range of values ​​for the torque T2 of the right front wheel is |T2|≤min{T m2 ,T u2 The four boundary lines L1, L2, L3, L4 formed by}

[0043]

[0044] Simultaneously, obtain the coordinates of the four boundary vertices p1, p2, p3, p4 generated by the intersection of the four boundary lines, and analytically calculate the additional yaw moment requirement W within the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2. M T=rΔM d The two boundary lines L formed m1 ,L m2 :

[0045]

[0046] Among them, T m1 T m2 T m3 T m4 T represents the maximum wheel torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, determined by the operating characteristics of the drive motor. u1 T u2 T u3 T u4 T1, T2, T3, and T4 represent the maximum wheel torque determined by tire adhesion at the current moment for the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. a is the longitudinal distance from the center of the front axle to the vehicle's center of gravity, b is the longitudinal distance from the center of the rear axle to the vehicle's center of gravity, l is half the track width, and δ... f Let F be the desired front wheel steering angle, r be the tire rolling radius, and F be the tire rolling radius. xsumd For the desired total longitudinal force, ΔM d To add a desired yaw moment;

[0047] When point p e1 ,p e2 ,p e3 ,p e4 There exist points p1, p2, p3, p4 within the region between parallel lines L1 and L2 and between parallel lines L3 and L4, or points p1, p2, p3, p4 within the region between parallel lines L1 and L2, and points p3, p4 within the region between parallel lines L3 and L4, satisfying the condition that p1, p2, p3, p4 are located within the region between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 When considering points within the region between the points, the inequality constraint for determining wheel torque can satisfy the additional yaw moment requirement and the total longitudinal force requirement.

[0048] When point p e1 ,p e2 ,p e3 ,p e4There are no points in the region between parallel lines L1 and L2 and between parallel lines L3 and L4, and none of the points p1, p2, p3, and p4 satisfy the condition of being located between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 Points within the region between L and L, and among p1, p2, p3, p4, there exists one that satisfies the condition of being located on a line parallel to L. m1 ,L m2 When the points are within the region between, the inequality constraint for determining wheel torque can satisfy the additional yaw moment requirement but cannot satisfy the total longitudinal force requirement.

[0049] When point p e1 ,p e2 ,p e3 ,p e4 There are no points in the region between parallel lines L1 and L2 and between parallel lines L3 and L4, and none of the points p1, p2, p3, and p4 satisfy the condition of being located between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 Points within the region between, and none of p1, p2, p3, p4 satisfy the condition of being located on a line parallel to L. m1 ,L m2 When the points are within the region between, the inequality constraint on wheel torque cannot satisfy the additional yaw moment requirement.

[0050] The specific method for determining whether a point lies within the region between two parallel lines is as follows:

[0051] Calculate the distances d1 and d2 from the point to the two parallel lines and the distance D between the two parallel lines, respectively. When |d1|+|d2|≤D, the point is determined to be located within the region between the two parallel lines. When |d1|+|d2|>D, the point is determined to be located outside the region between the two parallel lines.

[0052] Preferably, the specific process of the method in step six is ​​as follows:

[0053] When the inequality constraint of wheel torque can satisfy the additional yaw moment requirement and the total longitudinal force requirement, the compensation torque T of the four tires is established. ci To optimize the variables, minimize the tire compensation torque T ci Vertical load F of tire zi The problem is a quadratic programming problem with the sum of squares of the proportions J as the optimization objective, the desired total longitudinal force and the desired additional yaw moment as constraints, and the wheel torque inequality.

[0054]

[0055] When the inequality constraint of wheel torque can satisfy the additional yaw moment requirement but not the total longitudinal force requirement, a compensation torque T based on the four tires is established. ci To optimize the variables, with the goal of maximizing the total longitudinal force requirement, and constrained by the additional yaw moment requirement and the wheel torque inequality, this is a quadratic programming problem:

[0056]

[0057] When the inequality constraint of wheel torque cannot meet the additional yaw moment requirement, a compensation moment T based on the four tires is established. ci To optimize the variables and maximize the control of the additional yaw moment, the following quadratic programming problem is used, with the wheel torque inequality as the constraint:

[0058]

[0059] in:

[0060] T c =[T c1 T c2 T c3 T c4 ] Τ ;

[0061] T as =[T as1 T as2 T as3 T as4 ] Τ ;

[0062] W F =[cosδ f cosδ f 1 1];

[0063] W M =[a sinδ f -l cosδ f a sinδ f +l cosδ f -ll];

[0064] F z1 F z2 F z3 F z4 T represents the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. c1 T c2 T c3 T c4T represents the compensation torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. as1 T as2 T as3 T as4 T represents the anti-slip torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. p1 T p2 T p3 T p4 These represent the initial torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively.

[0065] Preferably, the desired torque T for each wheel i The formula for calculating (k) is as follows:

[0066] T i (k)=T pi (k)-T asi (k)+T ci (k);

[0067] In the formula, T pi (k) represents the initial torque of the wheel at the current moment, T asi (k) represents the anti-slip torque of the wheel at the current moment, T ci (k) represents the compensation torque of the wheel at the current moment.

[0068] The present invention has the following advantages:

[0069] 1. This invention designs a model-free anti-skid system control method that can prevent severe wheel slippage / skid when there is no road surface adhesion information. At the same time, it can make the output anti-skid torque zero in time before the wheel reaches the road surface adhesion limit, thereby minimizing the impact of the anti-skid system on the overall vehicle handling.

[0070] 2. This invention proposes a method for determining wheel torque inequality constraints. It uses the control information of the anti-skid system to calculate the maximum wheel torque limited by the tire adhesion force, so that the problem of high-precision real-time observation of the road adhesion coefficient is no longer needed in the torque optimization distribution task.

[0071] 3. This invention designs a compensation torque and its optimization algorithm, which can redistribute the torque of each wheel when the anti-slip system controls the wheel torque, so as to maximize the satisfaction of the vehicle's expected force and torque given by the upper control system, and improve the stability and handling of the vehicle under extreme conditions while coordinating different subsystems. Attached Figure Description

[0072] Figure 1 Flowchart of a distributed drive vehicle torque distribution method without road surface adhesion information perception;

[0073] Figure 2 This is a flowchart for obtaining wheel torque inequality constraints based on an anti-skid system;

[0074] Figure 3 This is a flowchart for optimizing the calculation of the compensation torque for each wheel in the torque distribution method. Detailed Implementation

[0075] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0076] As an embodiment of the present invention, such as Figures 1 to 3 As shown, a distributed drive vehicle torque distribution method without road surface adhesion information perception is described. The torque distribution method includes:

[0077] Step 1: Real-time acquisition of the vehicle's longitudinal velocity, longitudinal acceleration, yaw rate, center of gravity sideslip angle, tire speeds, and the desired front wheel steering angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller;

[0078] Step 2: Calculate the initial torque of the four wheels based on the vertical load of the tires according to the vehicle status information;

[0079] Step 3: Calculate the slip / slip ratio and anti-slip torque of each wheel based on the vehicle status information;

[0080] Step 4: Determine the inequality constraints of each wheel's torque based on the anti-slip torque, vertical load, initial torque, and compensation torque of each wheel.

[0081] Step 5: Based on the inequality constraints of the torque of each wheel, and the satisfaction of the additional yaw moment requirement and the total longitudinal force requirement, design a hierarchical constrained quadratic programming method with the compensation torque of each wheel as the optimization variable.

[0082] Step Six: Solve the quadratic programming problem established in Step Five to obtain the compensation torque for each wheel;

[0083] Step 7: Calculate the desired torque based on the initial torque, anti-slip torque, and compensation torque of each wheel.

[0084] As an embodiment of the present invention, such as Figure 1 As shown, the method for calculating the initial torque of each wheel is as follows:

[0085] Define F z1 F z2 Fz3 F z4 Let m represent the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively; m be the total vehicle mass; g be the acceleration due to gravity; a be the longitudinal distance from the center of the front axle to the vehicle's center of gravity; b be the longitudinal distance from the center of the rear axle to the vehicle's center of gravity; L be the longitudinal distance from the center of the front axle to the center of the rear axle; l be half the track width; and h be the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel. g v is the height of the vehicle's center of gravity. x Let F be the vehicle's longitudinal velocity, β be the vehicle's sideslip angle, and F be the vehicle's center of gravity. px1 F px2 F px3 F px4 T represents the initial longitudinal force on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. p1 T p2 T p3 T p4 F represents the initial torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. xsumd For the desired total longitudinal force, ΔM d To add the desired yaw moment, δ f Let r be the desired front wheel steering angle, and r be the tire rolling radius.

[0086] The vertical load F of the four wheels is calculated based on the vehicle status information. zi :

[0087]

[0088] This ignores the dynamic effects of the suspension system and road slope on the vertical load on the tires;

[0089] Secondly, based on the tire vertical load F zi Establish the initial longitudinal force F of the four tires pxi To optimize the variables, minimize the longitudinal force F of the tire. px Vertical load F of tire zi The problem is a quadratic programming problem with the sum of squares of the proportions J as the optimization objective, the desired total longitudinal force and the desired additional yaw moment as the constraints, and the road adhesion force limit.

[0090]

[0091] st W eq F px =[F xsumd ΔM d ] Τ ,

[0092] -F z ≤F px ≤F z ,

[0093] in:

[0094] F px =[F px1 F px2 F px3 F px4 ] Τ ,

[0095]

[0096] Solving the quadratic programming problem yields the optimal initial longitudinal force F. pxi Then, the initial torque T of the four wheels is calculated using the tire radius. pi :

[0097] T pi =F pxi r.

[0098] As an embodiment of the present invention, such as Figure 1 As shown, the method for calculating the anti-slip torque of each wheel is as follows:

[0099] Calculate the horizontal velocity vector v at the center of the wheel. i :

[0100] v i =v c +ω r ×x i ,

[0101] In the formula, v c ω represents the horizontal velocity vector of the vehicle's center of mass. r The vector representing the vehicle's yaw rate, x i This represents the projection vector of the vector originating from the vehicle's center of mass and ending at the center of the wheel onto the horizontal plane.

[0102] Based on the horizontal velocity vector v at the center of the wheel i Calculate the horizontal velocity v of the wheel when it is rolling in pure motion. pi :

[0103] v pi =v i ·(cosδ i ,sinδ i ,0),

[0104] In the formula, δ i Indicates the turning angle of the wheel;

[0105] Based on the horizontal velocity v of the wheel during pure rolling pi Calculate the wheel slip / slip ratio λ i :

[0106]

[0107] In the formula, the linear velocity of the tire is v = ω i r,ω i R is the tire rotation speed, and r is the tire radius.

[0108] Since there is no road surface adhesion information, the anti-skid system cannot use model-dependent control methods, so it relies solely on the wheel slip / slip ratio λ. i The anti-slip torque T of the wheel is designed as follows. asi :

[0109]

[0110] In the formula, λ u λ represents the maximum permissible wheel slip ratio. l λ represents the minimum permissible wheel slip ratio. i , Let k be the wheel slip / slip ratio and its derivative with respect to time. pi ,K pi ,k di ,K di ,h i H i ,c i C i To control the gain and ensure all values ​​are greater than 0, sat() is the saturation function:

[0111]

[0112] In the formula, p is the boundary layer thickness and is greater than 0.

[0113] As an embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the specific method for determining the inequality constraints of the torques of each wheel is as follows:

[0114] Determine the anti-slip torque T of the wheel at the current moment. asi Is (k) equal to 0?

[0115] When the anti-slip torque T of the wheel at the current moment asi When (k) is 0, the wheel torque T i The inequality constraints for (k) are as follows:

[0116] |T i (k)|≤min{T mi (k),T ui (k)},

[0117] In the formula, T mi (k) represents the maximum wheel torque determined by the operating characteristics of the drive motor at the current moment, T. ui(k) is the maximum wheel torque determined by tire adhesion at the current moment, and satisfies:

[0118] T ui (k)=min{F zi (k)r,T ui (k-1)+T r},

[0119] In the formula, F zi (k) represents the vertical load on the wheel at the current moment, r is the wheel radius, and T ui (k-1) represents the maximum wheel torque determined by tire adhesion at the previous moment, T r To restore torque;

[0120] Recovery torque T r The settings will continuously test the adhesion limit of the wheels, which can handle situations where the adhesion limit of the wheels increases from small to large, while avoiding large step changes in wheel torque constraints.

[0121] When the anti-slip torque T of the wheel at the current moment asi When (k) is not 0, the wheel torque T i The inequality constraints for (k) are as follows:

[0122] |T i (k)|≤min{T mi (k),T ui (k)},

[0123] In the formula, T i (k) represents the wheel torque, where i takes the value 1 or 2, representing the torque of the left front wheel and the right front wheel respectively; k represents the current time; T mi (k) represents the maximum wheel torque determined by the operating characteristics of the drive motor at the current moment, T. ui (k) is the maximum wheel torque determined by tire adhesion at the current moment, and satisfies:

[0124] T ui (k)=|T pi (k-1)+T ci (k-1)-T asi (k)|,

[0125] In the formula, T pi (k-1) represents the initial torque of the wheel at the previous moment, T ci (k-1) represents the compensation torque of the wheel at the previous moment.

[0126] As an embodiment of the present invention, such as Figure 1 and Figure 3As shown, the specific method for determining whether the upper-level control requirements are met by analyzing the feasible region is as follows:

[0127] Define T m1 T m2 T m3 T m4 T represents the maximum wheel torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, determined by the operating characteristics of the drive motor. u1 T u2 T u3 T u4 T1, T2, T3, and T4 represent the maximum wheel torque determined by tire adhesion at the current moment for the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. a is the longitudinal distance from the center of the front axle to the vehicle's center of gravity, b is the longitudinal distance from the center of the rear axle to the vehicle's center of gravity, l is half the track width, and δ... f Let F be the desired front wheel steering angle, r be the tire rolling radius, and F be the tire rolling radius. xsumd For the desired total longitudinal force, ΔM d To add the desired yaw moment and related matrices:

[0128] W F =[cosδ f cosδ f 1 1]

[0129] W M =[a sinδ f -l cosδ f a sinδ f +l cosδ f -ll]

[0130] The additional yaw moment requirement W is analytically calculated within the two-dimensional feasible region formed by the torques of the left and right front wheels, T1 and T2. M T=rΔM d Total longitudinal force requirement W F T = rF xsumd The four boundary lines L formed e1 ,L e2 ,L e3 ,L e4 Among them, W F =[cosδ f cosδ f 1 1], W M =[a sinδ f -l cosδ f a sinδ f +l cosδ f-ll],δ f Desired front wheel steering angle:

[0131]

[0132] Simultaneously obtain the four boundary vertices p generated by the intersection of the four boundary lines. e1 ,p e2 ,p e3 ,p e4 coordinates

[0133] Analytical calculations are performed within the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2, taking the value of the left front wheel torque T1 within the range |T1|≤min{T m1 ,T u1 The range of values ​​for the torque T2 of the right front wheel is |T2|≤min{T m2 ,T u2 The four boundary lines L1, L2, L3, L4 formed by}

[0134]

[0135] Simultaneously, obtain the coordinates of the four boundary vertices p1, p2, p3, and p4 formed by the intersection of the four boundary lines.

[0136] Analytical calculations are performed within the two-dimensional feasible region comprised of the left front wheel torque and the right front wheel torques T1 and T2, based solely on the additional yaw moment requirement W. M T=rΔM d The two boundary lines L formed m1 ,L m2 :

[0137]

[0138] Among them, T m1 T m2 T m3 T m4 T represents the maximum wheel torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, determined by the operating characteristics of the drive motor. u1 T u2 T u3 T u4 T1, T2, T3, and T4 represent the maximum wheel torque determined by tire adhesion at the current moment for the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. a is the longitudinal distance from the center of the front axle to the vehicle's center of gravity, b is the longitudinal distance from the center of the rear axle to the vehicle's center of gravity, l is half the track width, and δ... f Let F be the desired front wheel steering angle, r be the tire rolling radius, and F be the tire rolling radius. xsumd For the desired total longitudinal force, ΔMd To add a desired yaw moment;

[0139] When point p e1 ,p e2 ,p e3 ,p e4 There exist points p1, p2, p3, p4 within the region between parallel lines L1 and L2 and between parallel lines L3 and L4, or points p1, p2, p3, p4 within the region between parallel lines L1 and L2, and points p3, p4 within the region between parallel lines L3 and L4, satisfying the condition that p1, p2, p3, p4 are located within the region between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 When the points are within the region between, the inequality constraint for determining wheel torque can satisfy the additional yaw moment requirement and the total longitudinal force requirement; when point p e1 ,p e2 ,p e3 ,p e4 There are no points in the region between parallel lines L1 and L2 and between parallel lines L3 and L4, and there are no points among points p1, p2, p3, and p4 that satisfy the condition of being located between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 Points within the region between p1, p2, p3, p4, such that there exists one that lies parallel to line L. m1 ,L m2 When the points are within the region between, the inequality constraint for determining wheel torque satisfies the additional yaw moment requirement but not the total longitudinal force requirement; when point p e1 ,p e2 ,p e3 ,p e4 There are no points in the region between parallel lines L1 and L2 and between parallel lines L3 and L4, and there are no points among points p1, p2, p3, and p4 that satisfy the condition of being located between parallel lines L1 and L2. e1 ,L e2 Between and parallel lines L e3 ,L e4 Points within the region between, and none of p1, p2, p3, p4 satisfy the condition of being parallel to line L. m1 ,L m2 When the points are within the region between, the inequality constraint on wheel torque cannot satisfy the additional yaw moment requirement.

[0140] The method for determining whether a point is located within the region between two parallel lines is as follows: calculate the distances d1 and d2 from the point to the two parallel lines and the distance D between the two parallel lines respectively; when |d1|+|d2|≤D, the point is located within the region between the two parallel lines; when |d1|+|d2|>D, the point is located outside the region between the two parallel lines.

[0141] As an embodiment of the present invention, such as Figure 1 and Figure 3 As shown, the specific process of optimizing the solution for the compensation torque using the hierarchical constrained quadratic programming method is as follows:

[0142] Define F z1 F z2 F z3 F z4 T represents the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. c1 T c2 T c3 T c4 T represents the compensation torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. as1 T as2 T as3 T as4 T represents the anti-slip torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. p1 T p2 T p3 T p4 Let $\mathbf$ represent the initial torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively. The correlation coefficient matrix is ​​as follows:

[0143] T c =[T c1 T c2 T c3 T c4 ] Τ ,

[0144] T as =[T as1 T as2 T as3 T as4 ] Τ ,

[0145] W F =[cosδ f cosδ f 1 1],

[0146] W M =[a sinδ f -l cosδ f a sinδ f +l cosδ f -ll).

[0147] When the inequality constraint of wheel torque can meet the requirements of additional yaw moment control and total longitudinal force, a compensation torque T based on the four tires is established.c To optimize the variables, minimize the tire compensation torque T c Vertical load F of tire z The problem is a quadratic programming problem with the sum of squares of the proportions J as the optimization objective, the desired total longitudinal force and the desired additional yaw moment as constraints, and the wheel torque inequality.

[0148]

[0149] st W F T c =W F T as

[0150] W M T c =W M T as

[0151] -min{T mi ,T ui}+T asi -T pi ≤T ci ≤min{T mi ,T ui}+T asi -T pi ;

[0152] When the inequality constraint of wheel torque can meet the additional yaw moment control requirements but not the total longitudinal force requirements, a compensation torque T based on the four tires is established. c To optimize the variables, with the goal of maximizing the total longitudinal force requirement, and constrained by the additional yaw moment requirement and the wheel torque inequality, this is a quadratic programming problem:

[0153] min J=(W F T c -W F T as ) Τ (W F T c -W F T as ),

[0154] st W M T c =W M T as

[0155] -min{T mi ,T ui}+T asi -T pi ≤T ci≤min{T mi ,T ui}+T asi -T pi ,

[0156] Here, the standard form of the cost function J is J = T. c Τ W F Τ W F T c -2T as Τ W F Τ W F T c ;

[0157] When the inequality constraint of wheel torque cannot meet the requirements for additional yaw moment control, a compensation torque T based on the four tires is established. c To optimize the variables and maximize the control of the additional yaw moment, the following quadratic programming problem is used, with the wheel torque inequality as the constraint:

[0158] min J=(W M T c -W M T as ) Τ (W M T c -W M T as ),

[0159] st -min{T mi ,T ui}+T asi -T pi ≤T ci ≤min{T mi ,T ui}+T asi -T pi ,

[0160] Here, the standard form of the cost function J is J = T. c Τ W M Τ W M T c -2T as Τ W M Τ W M T c .

[0161] As an embodiment of the present invention, such as Figure 1As shown, the method for obtaining the desired torque of each wheel is to use the desired torque T of each wheel. i The formula for calculating (k) is:

[0162] T i (k)=T pi (k)-T asi (k)+T ci (k),

[0163] In the formula, T pi (k) represents the initial torque of the wheel at the current moment, T asi (k) represents the anti-slip torque of the wheel at the current moment, T ci (k) represents the compensation torque of the wheel at the current moment.

[0164] Finally, the expected torque T for each wheel was calculated. i (k) is then transmitted to the corresponding drive motor execution unit and braking mechanism execution unit of each wheel.

[0165] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for torque distribution in a distributed drive vehicle without road surface adhesion information perception, characterized in that: Includes the following steps: Step 1: Real-time acquisition of status information, including the vehicle's longitudinal speed, longitudinal acceleration, yaw rate, center of gravity sideslip angle, speed of each tire, and the desired front wheel steering angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller; Step 2: Calculate the initial torque of the four wheels based on the vertical load of the tires according to the vehicle status information; Step 3: Calculate the slip / slip ratio and anti-slip torque of each wheel based on the vehicle status information; Step 4: Determine the inequality constraints of the torque of each wheel based on the anti-slip torque, vertical load, initial torque, and compensation torque of each wheel. Step 5: Determine whether the inequality constraints of each wheel torque satisfy the additional yaw moment requirement and the total longitudinal force requirement by analyzing the feasible region. Step Six: Design a hierarchical constrained quadratic programming method with the compensation torque of each wheel as the optimization variable; Step 7: Solve the quadratic programming problem established in Step 6 to obtain the compensation torque for each wheel; Step 8: Calculate the desired torque based on the initial torque, anti-slip torque, and compensation torque of each wheel; The specific method for determining the inequality constraint of wheel torque in step four is as follows: Determine the anti-slip torque of the wheel at the current moment. Whether it is 0, the anti-slip torque of the wheel at the current moment. When it is 0, the torque of this wheel The inequality constraints are as follows: ； In the formula, This represents the wheel torque, where i takes the value 1 or 2, representing the torque of the left front wheel and the torque of the right front wheel, respectively; k represents the current time. This represents the maximum wheel torque at the current moment, determined by the operating characteristics of the drive motor. The maximum wheel torque determined by tire adhesion at the current moment, satisfying: ； In the formula, This represents the vertical load on the wheel at the current moment. For the wheel radius, This represents the maximum wheel torque determined by tire adhesion at the previous moment. To restore torque; The anti-slip torque of the wheel at the current moment When the torque is not zero, the torque of the wheel is... The inequality constraints are as follows: ； In the formula, This represents the maximum wheel torque at the current moment, determined by the operating characteristics of the drive motor. The maximum wheel torque determined by tire adhesion at the current moment, satisfying: ； In the formula, The initial torque of the wheel at the previous moment. This is the compensation torque of the wheel at the previous moment.

2. The method for distributed drive vehicle torque distribution without road surface adhesion information perception according to claim 1, characterized in that: The specific calculation method for step two is as follows: First, calculate the vertical load of the four wheels' tires based on the vehicle status information. ; Then based on the vertical load of the tire Solve for the initial longitudinal forces of the four tires. To optimize variables, minimize the longitudinal force of the tire. Vertical load of tire Sum of squares of proportions To optimize the objective, a quadratic programming problem is posed with constraints including the desired total longitudinal force, the desired additional yaw moment, and the road adhesion force. Solving the quadratic programming problem yields the initial longitudinal force. Then, the initial torque of the four wheels is calculated using the tire radius. .

3. The distributed drive vehicle torque distribution method without road surface adhesion information perception according to claim 1, characterized in that: The calculation process for the slip / slip ratio of each wheel in step three is as follows: Based on the obtained longitudinal velocity of the vehicle, calculate the horizontal velocity vector at the wheel center. : ； In the formula, The horizontal velocity vector representing the vehicle's center of mass. This represents the vehicle's yaw rate vector. This represents the projection vector of the vector originating from the vehicle's center of mass and ending at the center of the wheel onto the horizontal plane. Based on the horizontal velocity vector at the center of the wheel Calculate the horizontal velocity of the wheel when it is rolling in pure rolling mode. : ； In the formula, Indicates the turning angle of the wheel; Based on the horizontal speed of the wheel during pure rolling Calculate the wheel slip / slip ratio : ； In the formula, the tire linear velocity , For tire speed, The radius of the tire; The anti-slip torque of the wheel in step three The calculation formula is as follows: ； In the formula, Indicates the maximum permissible wheel slip ratio. This indicates the minimum permissible wheel slip ratio. These represent the wheel's slip / slip ratio and its derivative with respect to time. To control the gain and ensure that all values ​​are greater than 0, sat() is a saturation function.

4. The distributed drive vehicle torque distribution method without road surface adhesion information perception according to claim 1, characterized in that: The specific method for determining whether the inequality constraints of each wheel torque satisfy the additional yaw moment requirement and the total longitudinal force requirement by analyzing the feasible region in step five is as follows: Torque of the left front wheel and torque of the right front wheel Analytical calculations are performed within the two-dimensional feasible region to determine the additional yaw moment requirement. and total longitudinal force requirements The four boundary lines formed ,in, , , Desired front wheel steering angle: ； Simultaneously, obtain the four boundary vertices generated by the intersection of the four boundary lines. The coordinates of the left front wheel torque and the right front wheel torque Analytical calculation of the torque of the left front wheel within the two-dimensional feasible region. Range of values and right front wheel torque Range of values The four boundary lines formed : ； Simultaneously, obtain the four boundary vertices generated by the intersection of the four boundary lines. The coordinates of the left front wheel torque and the right front wheel torque Analytical calculations within the constructed two-dimensional feasible region are based solely on the additional yaw moment requirement. The two boundary lines formed : ； in, These represent the maximum wheel torque values ​​at the current moment, determined by the operating characteristics of the drive motor for the left front wheel, right front wheel, left rear wheel, and right rear wheel. These represent the maximum wheel torque determined by tire adhesion for the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. These represent the torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively. This is the longitudinal distance from the center of the front axle to the vehicle's center of gravity. is the longitudinal distance from the rear axle center to the vehicle's center of gravity, where l is half the track width. To achieve the desired front wheel steering angle, The tire's rolling radius, For the desired total longitudinal force, To add a desired yaw moment; On point There exist lines that satisfy the condition of being parallel to a line. Between and parallel lines Points or points within the area between There exist lines that satisfy the condition of being parallel to a line. Between and parallel lines When considering points within the region between the points, the inequality constraint for determining wheel torque can satisfy the additional yaw moment requirement and the total longitudinal force requirement. On point There is no line in the equation that satisfies the condition of being parallel to a line. Between and parallel lines Points within the region between, and point There is no line in the equation that satisfies the condition of being parallel to a line. Between and parallel lines Points within the area between, and There exist lines that satisfy the condition of being parallel to a line. When the points are within the region between, the inequality constraint for determining wheel torque can satisfy the additional yaw moment requirement but cannot satisfy the total longitudinal force requirement. On point There is no line in the equation that satisfies the condition of being parallel to a line. Between and parallel lines Points within the region between, and point There is no line in the equation that satisfies the condition of being parallel to a line. Between and parallel lines Points within the area between, and There is no line in the equation that satisfies the condition of being parallel to a line. When the points are within the region between, the inequality constraint on wheel torque cannot satisfy the additional yaw moment requirement. The specific method for determining whether a point lies within the region between two parallel lines is as follows: Calculate the distances from the point to the two parallel lines respectively. Distance to two parallel lines ;when When the decision point is located within the region between two parallel lines; when When the determination point is located outside the region between the two parallel lines.

5. The distributed drive vehicle torque distribution method without road surface adhesion information perception according to claim 1, characterized in that: The specific process of the method described in step six is ​​as follows: When the inequality constraint of wheel torque can meet the additional yaw moment requirement and the total longitudinal force requirement, a compensation torque based on the four tires is established. To optimize variables and minimize tire compensation torque Vertical load of tire Sum of squares of proportions To optimize the objective, a quadratic programming problem is proposed, constrained by the desired total longitudinal force, the desired additional yaw moment, and the wheel torque inequality: ； When the inequality constraint of wheel torque can satisfy the additional yaw moment requirement but not the total longitudinal force requirement, a compensation torque based on the four tires is established. To optimize the variables, with the goal of maximizing the total longitudinal force requirement, and constrained by the additional yaw moment requirement and the wheel torque inequality, this is a quadratic programming problem: ； When the inequality constraint of wheel torque cannot meet the additional yaw moment requirement, a compensation torque based on the four tires is established. To optimize the variables and maximize the control of the additional yaw moment, the following quadratic programming problem is used, with the wheel torque inequality as the constraint: ； In these three quadratic programming problems: ； ； ； ； These represent the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively. These represent the compensation torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively. These represent the anti-slip torque of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. These represent the initial torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, respectively.

6. The distributed drive vehicle torque distribution method without road surface adhesion information perception according to claim 1, characterized in that: Desired torque for each wheel The calculation formula is as follows: ； In the formula, The initial torque of the wheel at the current moment. This represents the anti-slip torque of the wheel at the current moment. This represents the compensation torque of the wheel at the current moment.

Images