Distributed driving automobile torque distribution method without road surface attachment information perception

Abstract

The invention discloses a distributed driving automobile torque distribution method without road surface attachment information perception, and particularly relates to the technical field of distributed driving automobile driving torque distribution.The method comprises the steps that firstly, vehicle state information and upper layer control requirements are obtained, and the initial torque of each wheel is calculated in combination with tire vertical loads; designing an anti-slip torque control law according to the slip / slip rate, and estimating the value range of the torque of each wheel; the condition that the value range of the torque of each wheel meets the upper-layer control requirement is judged by analyzing the feasible region, and a layered constraint quadratic programming method is designed to optimize and solve the compensation torque of each wheel; and obtaining expected torque of each wheel according to the initial torque, the anti-skid torque and the compensation torque of each wheel. Aiming at the problem that the road adhesion coefficient is difficult to accurately observe under small excitation and composite working conditions, the method provided by the invention can be used for improving the stability and the maneuverability of the vehicle to the greatest extent when no road adhesion information is perceived, and reducing conflicts between functions of a torque vector distribution system, an anti-skid system and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed drive vehicle drive torque distribution, and particularly relates to a torque distribution method for a distributed drive vehicle without road adhesion information perception. Background Art

[0002] Distributed drive vehicles control driving forces by using in-wheel motors or wheel-side motors, and can accurately, quickly, and stably execute the control instructions of the vehicle's electronic control system, achieving better performance and safety goals, and bringing a more comfortable, safe, and convenient driving experience to users. Therefore, they have great application potential. Currently, the active safety technologies applied to the chassis of distributed drive vehicles mainly include an active front-wheel steering system (AFS), a direct yaw moment control system (DYC), and an electronic stability control system (ESP), etc. Multiple subsystems can give full play to the over-drive characteristics of distributed drive vehicles, enabling them to meet the control requirements under more working conditions. However, at the same time, with the increase in subsystems, the complexity and coupling of the chassis control system will also increase. Inappropriate and imperfect control strategies often lead to functional conflicts between subsystems, which instead weakens the performance of the whole vehicle. In the existing coordinated control of distributed drive vehicle chassis, most studies perform quadratic programming distribution of the torque of each wheel through adhesion constraints on the expected steering angle, yaw moment, etc. obtained after coordinating the control of DYC and other systems, without considering the functional conflicts generated when the anti-skid system in ESP participates in torque control. And DYC and anti-skid system control often start to work when approaching the limit working conditions. Therefore, it is impossible to ensure the stability and maneuverability of the whole vehicle under limit working conditions. Therefore, a coordinated strategy for subsystems such as DYC and the anti-skid system needs to be designed when distributing torque.

[0003] In the existing torque distribution methods for distributed drive vehicles, such as quadratic programming, axle load distribution, and other coordinated distribution methods, they all rely very much on the accurate road adhesion coefficient. However, it is very difficult to accurately observe the road adhesion coefficient in real time, especially under small excitation and complex working conditions. Moreover, when distributing torque for distributed drive vehicles, relevant information of each wheel needs to be obtained. In the working condition where the road adhesion coefficients corresponding to the four wheels are inconsistent, it is even more difficult to observe the road adhesion coefficient of each wheel in real time. Therefore, the torque distribution method relying on the accurate road adhesion coefficient cannot ensure the accuracy and practicability under various harsh working conditions. Summary of the Invention

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

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

[0006] Step 1: Obtain the status information in real time, including the longitudinal speed, longitudinal acceleration, yaw rate, sideslip angle of the center of mass, rotational speed of each tire, and the desired front wheel angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller;

[0007] Step 2: Calculate the initial torques of the four wheels according to the vehicle status information and the tire vertical loads;

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

[0009] Step 4: Determine the inequality constraints of the torques of each wheel according to the anti-skid torque, vertical load, initial torque, and compensation torque of each wheel;

[0010] Step 5: Judge the satisfaction of the inequality constraints of the torques of each wheel for the demand of additional yaw moment and total longitudinal force by analyzing the feasible region;

[0011] Step 6: Design a hierarchical constrained quadratic programming method with the compensation torques of each wheel as the optimization variables;

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

[0013] Step 8: Calculate the desired torques according to the initial torques, anti-skid torques, and compensation torques of each wheel.

[0014] Preferably, the specific calculation method of Step 2 is: first, solve the tire vertical loads F of the four wheels according to the vehicle status information zi ; then, with the initial longitudinal forces F of the four tires zi as the optimization variables, solve the quadratic programming problem with minimizing the sum of the squares of the ratio of the tire longitudinal force F pxi to the tire vertical load F px as the optimization objective, and the demands of the desired total longitudinal force and desired additional yaw moment and the road adhesion limit as the constraints; after solving the quadratic programming problem to obtain the initial longitudinal force F zi pxi pxi pi pi , calculate the initial torques T of the four wheels using the tire radius.

[0015] Preferably, the calculation process of the slip / slip ratio of each wheel in Step 3 is as follows:

[0016] According to the obtained longitudinal speed of the vehicle, calculate the horizontal speed vector v of the wheel center i :

[0017] v i = v c+ω r ×x i ;

[0018] wherein, v c represents the horizontal velocity vector of the vehicle's center of mass, which requires information on the longitudinal velocity, ω r represents the yaw angular velocity vector of the vehicle, and x i represents the projection vector on the horizontal plane of the vector starting from the vehicle's center of mass and ending at the wheel center;

[0019] Based on the horizontal velocity vector v i of the wheel center, calculate the horizontal velocity v pi during pure rolling of the wheel:

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

[0021] wherein, δ i represents the wheel angle;

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

[0023]

[0024] wherein, the linear velocity of the tire v = ω i r, ω i is the tire rotational speed, and r is the tire radius.

[0025] The anti-slip torque T asi of the wheel in the third step is calculated as follows:

[0026]

[0027] wherein, λ u represents the maximum allowable wheel slip ratio, λ l represents the minimum allowable wheel slip ratio, λ i , are respectively the slip ratio of the wheel and its derivative with respect to time, k pi , K pi , k di , K di , h i , H i , c i , C iBoth are greater than 0 for control increase, and sat() is a saturation function. Preferably, the specific determination method of the inequality constraint of the wheel torque in the fourth step is as follows:

[0028] Judge whether the anti-slip torque T asi (k) of the wheel at the current moment is 0. When the anti-slip torque T asi (k) of the wheel at the current moment is 0, the inequality constraint of the wheel torque T i (k) is 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 of 1 or 2, representing the left front wheel torque and the right front wheel torque respectively; k represents the current moment; T mi (k) is the maximum wheel torque determined by the working characteristics of the drive motor at the current moment, and T ui (k) is the maximum wheel torque determined by the 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) is the vertical load of the wheel at the current moment, r is the wheel radius, T ui (k - 1) is the maximum wheel torque determined by the tire adhesion at the previous moment, and T r is the recovery torque;

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

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

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

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

[0037] Wherein, T pi (k - 1) is the initial torque of the wheel at the previous moment, and T ci (k - 1) is the compensation torque of the wheel at the previous moment.

[0038] Preferably, the specific judgment method for judging the satisfaction of the inequality constraints of the torques of each wheel on the additional yaw moment demand and the total longitudinal force demand in the fifth step is as follows:

[0039] In the two-dimensional feasible region formed by the torques T1 and T2 of the left front wheel and the right front wheel, analyze and calculate the additional yaw moment demand W M T = rΔM d and the total longitudinal force demand W F T = rF xsumd to form four boundary lines L e1 , L e2 , L e3 , L e4 , where W F = [cosδ f cosδ f 1 1],

[0040] W M = [asinδ f - lcosδ f asinδ f + lcosδ f - l l], δ f is the desired front wheel angle:

[0041]

[0042] At the same time, obtain the coordinates of the four boundary vertices p e1 , p e2 , p e3 , p e4 formed by the intersection of the four boundary lines. Analyze and calculate in the two-dimensional feasible region formed by the torques T1 and T2 of the left front wheel and the right front wheel the four boundary lines L1, L2, L3, L4 formed by the value range of the left front wheel torque |T1| ≤ min{T m1 , T u1} and the value range of the right front wheel torque |T2| ≤ min{T m2 , T u2}:

[0043]

[0044] Simultaneously obtain the coordinates of the four boundary vertices p1, p2, p3, and p4 generated by the intersection of the four boundary lines, and analytically calculate only the additional yaw moment requirement W in 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 to form two boundary lines L m1 , L m2 :

[0045]

[0046] where T m1 , T m2 , T m3 , T m4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the driving motor operating characteristics at the current moment, T u1 , T u2 , T u3 , T u4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the tire adhesion at the current moment, T1, T2, T3, and T4 respectively represent the torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, a is the longitudinal distance from the front axle center to the vehicle center of mass, b is the longitudinal distance from the rear axle center to the vehicle center of mass, l is half of the wheelbase, δ f is the desired front wheel angle, r is the tire rolling radius, F xsumd is the desired total longitudinal force, ΔM d is the desired additional yaw moment;

[0047] When there are points in points p e1 , p e2 , p e3 , p e4 that satisfy being within the region between the parallel lines L1 and L2 and between the parallel lines L3 and L4, or when there are points in points p1, p2, p3, p4 that satisfy being within the region between the parallel lines L e1 , L e2 and between the parallel lines L e3 , L e4 , it is determined that the inequality constraints of the wheel torque can meet the additional yaw moment requirement and the total longitudinal force requirement;

[0048] When points p e1 , p e2 , p e3 , p e4There are no points in it that satisfy being in the area between parallel lines L1 and L2 and between parallel lines L3 and L4, and among points p1, p2, p3, p4, there are no points that satisfy being in the area between parallel lines L e1 , L e2 and between parallel lines L e3 , L e4 . And when there are points among p1, p2, p3, p4 that satisfy being in the area between parallel lines L m1 , L m2 , it is determined that the inequality constraint of the wheel torque can meet the additional yaw moment requirement but cannot meet the total longitudinal force requirement;

[0049] When points p e1 , p e2 , p e3 , p e4 There are no points in it that satisfy being in the area between parallel lines L1 and L2 and between parallel lines L3 and L4, and among points p1, p2, p3, p4, there are no points that satisfy being in the area between parallel lines L e1 , L e2 and between parallel lines L e3 , L e4 . And when there are no points among p1, p2, p3, p4 that satisfy being in the area between parallel lines L m1 , L m2 , it is determined that the inequality constraint of the wheel torque cannot meet the additional yaw moment requirement;

[0050] The method for specifically determining whether a point is in the area 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, it is determined that the point is in the area between the two parallel lines; when |d1| + |d2| > D, it is determined that the point is outside the area 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 the wheel torque can meet the additional yaw moment requirement and the total longitudinal force requirement, establish a quadratic programming problem with the compensation torques T ci of the four tires as the optimization variables, minimizing the sum of the squares J of the ratio of the tire compensation torque T ci to the tire vertical load F zi as the optimization objective, and the requirements of the desired total longitudinal force and the desired additional yaw moment and the wheel torque inequality as the constraints:

[0054]

[0055] When the inequality constraint of the wheel torque can meet the additional yaw moment requirement but cannot meet the total longitudinal force requirement, a quadratic programming problem is established with the compensation torques T of the four tires as the optimization variables, maximizing the satisfaction of the total longitudinal force requirement as the optimization objective, and the requirements of the desired additional yaw moment and the wheel torque inequality as the constraints: ci

[0056]

[0057] When the inequality constraint of the wheel torque cannot meet the additional yaw moment requirement, a quadratic programming problem is established with the compensation torques T of the four tires as the optimization variables, maximizing the satisfaction of the additional yaw moment control requirement as the optimization objective, and the wheel torque inequality as the constraint: ci

[0058]

[0059] Where:

[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 -l l];

[0064] F z1 、F z2 、F z3 、F z4 respectively represent the vertical loads of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T c1 、T c2 、T c3 、T c4 ​​​​respectively represent the compensation torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T as1 , T as2 , T as3 , T as4 respectively represent the anti-slip torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T p1 , T p2 , T p3 , T p4 respectively represent the initial torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment.

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

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

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

[0068] The present invention has the following advantages:

[0069] 1. The present invention designs a model-free anti-slip system control method, which can prevent the wheels from severely spinning / sliding without road adhesion information, and at the same time can make the output anti-slip torque zero in time when the wheels do not reach the road adhesion limit, thus minimizing the impact of the anti-slip system on the vehicle's maneuverability.

[0070] 2. The present invention proposes a method for determining the wheel torque inequality constraint, and calculates the maximum value of the wheel torque limited by the tire adhesion force by using the control information of the anti-slip system, so that the problem of accurately and real-time observing the road adhesion coefficient does not need to be solved in the torque optimization distribution task.

[0071] 3. The present invention designs a compensation torque and its optimization algorithm, which can re-coordinate and distribute the torques of each wheel when the anti-slip system controls the wheel torque, maximize the satisfaction of the vehicle's desired force and moment given by the upper control system, coordinate different subsystems, and improve the stability and maneuverability of the vehicle under extreme conditions. Brief Description of the Drawings

[0072] Figure 1 is a flowchart of the torque distribution method for a distributed drive vehicle without road adhesion information perception;

[0073] Figure 2 Flow chart for obtaining the inequality constraint of wheel torque based on the anti-slip system;

[0074] Figure 3 Flow chart for optimizing and solving the compensation torque of each wheel in the torque distribution method. Detailed implementation manners

[0075] The following specific embodiments illustrate the implementation manners 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 part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

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

[0077] Step 1: Obtain the longitudinal speed, longitudinal acceleration, yaw rate, sideslip angle of the center of mass, the rotational speed of each tire, and the desired front wheel angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller of the vehicle in real time;

[0078] Step 2: Calculate the initial torque of the four wheels according to the vehicle state information and the tire vertical load;

[0079] Step 3: Calculate the slip / slip ratio and anti-slip torque of each wheel according to the vehicle state information;

[0080] Step 4: Determine the inequality constraint of each wheel torque according to the anti-slip torque, vertical load, initial torque, and compensation torque of each wheel;

[0081] Step 5: Design a hierarchical constrained quadratic programming method with the compensation torque of each wheel as the optimization variable according to the satisfaction of the additional yaw moment demand and the total longitudinal force demand by the inequality constraint of each wheel torque;

[0082] Step 6: Solve the quadratic programming problem established in Step 5 to obtain the compensation torque of each wheel;

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

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

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

[0086] Solve for the tire vertical loads F of the four wheels based on the vehicle state information zi :

[0087]

[0088] Here, the dynamic effects of the suspension system and road surface gradient on the tire vertical loads are ignored;

[0089] Secondly, based on the tire vertical loads F zi establish a quadratic programming problem with the initial longitudinal forces F of the four tires pxi as the optimization variables, minimizing the sum of the squares J of the ratio of the tire longitudinal force F px to the tire vertical load F zi as the optimization objective, and the requirements of the desired total longitudinal force and desired additional yaw moment, as well as the road surface adhesion limit as the constraints:

[0090]

[0091] s.t W eq F px = [F xsumd ΔM d Τ ,

[0092] -F z ≤F px ≤F z ,

[0093] ​Wherein:

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

[0095]

[0096] Solve the quadratic programming problem to obtain the optimal initial longitudinal force F pxi After that, calculate the initial torque T of the four wheels using the tire radius pi :

[0097] T pi = F pxi r.

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

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

[0100] v i = v c + ω r × x i ,

[0101] In the formula, v c represents the horizontal velocity vector of the vehicle's center of mass, ω r represents the vehicle's yaw angular velocity vector, and x i represents the projection vector in the horizontal plane of the vector starting from the vehicle's center of mass and ending at the wheel center;

[0102] According to the horizontal velocity vector v of the wheel center i Calculate the horizontal velocity v during pure rolling of the wheel pi :

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

[0104] In the formula, δ i represents the wheel's steering angle;

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

[0106] ​

[0107] wherein, the tire linear velocity v = ω i r, ω i is the tire rotational speed, and r is the tire radius.

[0108] Since there is no road surface adhesion information, the anti-skid system cannot use a model-dependent control method. Therefore, only based on the wheel slip / slip ratio λ i the anti-skid torque T of the following wheel is designed asi :

[0109]

[0110] wherein, λ u represents the maximum allowable wheel slip ratio, λ l represents the minimum allowable wheel slip ratio, λ i , are respectively the wheel slip / slip ratio and its derivative with respect to time, k pi , K pi , k di , K di , h i , H i , c i , C i are control gains and are all greater than 0, and sat() is a saturation function:

[0111]

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

[0113] As an embodiment of the present invention, as Figure 1 and Figure 2 shown, the specific determination method of the inequality constraint of each wheel torque is:

[0114] Judge whether the anti-skid torque T asi (k) of the wheel at the current moment is 0;

[0115] When the anti-skid torque T asi (k) of the wheel at the current moment is 0, the inequality constraint of the wheel torque T i (k) is as follows:

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

[0117] wherein, T mi (k) is the maximum value of the 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 the tire adhesion at the current moment and satisfies:

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

[0119] wherein, F zi (k) is the vertical load of the wheel at the current moment, r is the wheel radius, T ui (k - 1) is the maximum wheel torque determined by the tire adhesion at the previous moment, T r is the recovery torque;

[0120] The setting of the recovery torque T r will continuously probe the adhesion limit of the wheel, can handle the situation where the adhesion limit of the wheel increases from small to large, and at the same time avoid large step changes in the wheel torque constraint.

[0121] When the anti-skid torque T asi (k) of the wheel at the current moment is not 0, the inequality constraint of the wheel torque T i (k) is as follows:

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

[0123] wherein, T i (k) represents the wheel torque, wherein, i takes the value of 1 or 2, respectively representing the left front wheel torque and the right front wheel torque; k represents the current moment; T mi (k) is 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 the tire adhesion at the current moment and satisfies:

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

[0125] wherein, T pi (k - 1) is the initial torque of the wheel at the previous moment, T ci (k - 1) is 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 judging whether the upper-layer control requirements are met in the parsing feasible region is as follows:

[0127] Define T m1 、T m2 、T m3 、T m4 to represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the working characteristics of the drive motor at the current moment respectively. T u1 、T u2 、T u3 、T u4 represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the tire adhesion at the current moment respectively. T1, T2, T3, and T4 represent the torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment respectively. a is the longitudinal distance from the center of the front axle to the vehicle's center of mass, b is the longitudinal distance from the center of the rear axle to the vehicle's center of mass, l is half of the wheelbase, δ f is the desired front wheel angle, r is the tire rolling radius, F xsumd is the desired total longitudinal force, ΔM d is the desired additional 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 -l l]

[0130] In the two-dimensional feasible region formed by the torques T1 and T2 of the left front wheel and the right front wheel, analytically calculate the four boundary lines L M T = rΔM d and the total longitudinal force requirement W F T = rF xsumd formed. Here, W e1 , L e2 , L e3 , L e4 , where W F =[cosδ f cosδ f 1 1], W M =[a sinδ f -l cosδ f a sinδ f +l cosδ f-l l],δ f is the desired front wheel steering angle:

[0131]

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

[0133] In the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2, analytically calculate the four boundary lines L1, L2, L3, L4 formed by the value range of the left front wheel torque |T1| ≤ min{T m1 , T u1} and the value range of the right front wheel torque |T2| ≤ min{T m2 , T u2}:

[0134]

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

[0136] In the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2, analytically calculate the two boundary lines L M T = rΔM d formed only by the additional yaw moment demand W m1 , L m2 :

[0137]

[0138] where T m1 , T m2 , T m3 , T m4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the driving motor operating characteristics at the current moment, T u1 , T u2 , T u3 , T u4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the tire adhesion at the current moment, T1, T2, T3, and T4 respectively represent the torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, a is the longitudinal distance from the center of the front axle to the vehicle's center of mass, b is the longitudinal distance from the center of the rear axle to the vehicle's center of mass, l is half of the wheelbase, δ f is the desired front wheel steering angle, r is the tire rolling radius, F xsumd is the desired total longitudinal force, ΔMd is the desired additional yaw moment;

[0139] When point p e1 , p e2 , p e3 , p e4 there are points in the region that satisfy being between the parallel lines L1, L2 and between the parallel lines L3, L4, or among the points p1, p2, p3, p4 there are points that satisfy being between the parallel lines L e1 , L e2 and between the parallel lines L e3 , L e4 and between the parallel lines L e1 , p e2 , p e3 , p e4 there are no points in the region that satisfy being between the parallel lines L1, L2 and between the parallel lines L3, L4, and among the points p1, p2, p3, p4 there are no points that satisfy being between the parallel lines L e1 , L e2 and between the parallel lines L e3 , L e4 and between the parallel lines L m1 , L m2 and between the parallel lines L e1 , p e2 , p e3 , p e4 there are no points in the region that satisfy being between the parallel lines L1, L2 and between the parallel lines L3, L4, and among the points p1, p2, p3, p4 there are no points that satisfy being between the parallel lines L e1 , L e2 and between the parallel lines L e3 , L e4 and between the parallel lines L m1 , L m2 and among the points p1, p2, p3, p4 there are no points that satisfy being between the parallel lines L

[0140] The method for determining whether a point is in the region between two parallel lines is specifically to calculate the distances d1, d2 from the point to the two parallel lines and the distance D between the two parallel lines respectively; when |d1| + |d2| ≤ D, it is determined that the point is in the region between the two parallel lines; when |d1| + |d2| > D, it is determined that the point is outside the region between the two parallel lines;

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

[0142] Define F z1 、F z2 、F z3 、F z4 to represent the vertical loads of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment respectively, and T c1 、T c2 、T c3 、T c4 to represent the compensation torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment respectively, and T as1 、T as2 、T as3 、T as4 to represent the anti-skid torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment respectively, and T p1 、T p2 、T p3 、T p4 to 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:

[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 -l l]。

[0147] When the inequality constraints of the wheel torque can meet the additional yaw moment control requirements and the total longitudinal force requirements, establish the compensation torques T of the four tires​​c To optimize the variables and minimize the tire compensation torque T c and the square sum J of the ratio of the tire vertical load F z is the optimization objective, and the quadratic programming problem is constrained by the requirements of the expected total longitudinal force and the expected additional yaw moment and the wheel torque inequality:

[0148]

[0149] s.t 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 the wheel torque can meet the demand of the additional yaw moment control but cannot meet the demand of the total longitudinal force, a quadratic programming problem is established with the compensation torques T c of the four tires as the optimization variables and maximizing the satisfaction of the total longitudinal force demand as the optimization objective, and the requirements of the expected additional yaw moment and the wheel torque inequality as the constraints:

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

[0154] s.t 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 the wheel torque cannot meet the additional yaw moment control requirement, a quadratic programming problem is established with the compensation torques T c of the four tires as the optimization variables, the maximum satisfaction of the additional yaw moment control requirement as the optimization objective, and 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] s.t - 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, as Figure 1As shown, the method for obtaining the expected torque of each wheel is to use the calculation formula of the expected torque T i (k):

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

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

[0164] Finally, after calculating the expected torque T i (k) of each wheel, it is respectively transmitted to the corresponding drive motor execution unit and brake mechanism execution unit of each wheel.

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

Claims

1. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception, characterized in that: Including the following steps: Step 1: Obtain the status information in real time, including the longitudinal speed, longitudinal acceleration, yaw rate, sideslip angle of the center of mass, rotational speeds of each tire, and the desired front wheel angle, desired total longitudinal force, and desired additional yaw moment output by the upper controller; Step 2: Calculate the initial torques of the four wheels according to the tire vertical loads based on the vehicle status information; Step 3: Calculate the slip / slip ratio and anti-slip torque of each wheel according to the vehicle status information; Step 4: Determine the inequality constraints of the torques of each wheel according to the anti-slip torque, vertical load, initial torque, and compensation torque of each wheel; Step 5: Judge whether the inequality constraints of the torques of each wheel meet the requirements of the additional yaw moment demand and the total longitudinal force demand by analyzing the feasible region; Step 6: Design a hierarchical constrained quadratic programming method with the compensation torques of each wheel as the optimization variables; Step 7: Solve the quadratic programming problem established in Step 6 to obtain the compensation torques of each wheel; Step 8: Calculate the desired torques according to the initial torques, anti-slip torques, and compensation torques of each wheel.

2. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 1, characterized in that: The specific calculation method of the second step is as follows: First, solve the vertical tire loads F of the four wheels according to the vehicle state information zi ; then, according to the vertical tire loads F zi solve the quadratic programming problem with the initial longitudinal forces F of the four tires pxi as the optimization variables, minimizing the sum of squares J of the ratio of the longitudinal tire force F px to the vertical tire load F zi as the optimization objective, and the requirements of the desired total longitudinal force and the desired additional yaw moment as well as the road adhesion limit as the constraints; after solving the quadratic programming problem to obtain the initial longitudinal forces F pxi , calculate the initial torques T of the four wheels using the tire radius pi .

3. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 1, characterized in that: The calculation process of the slip / slip ratio of each wheel in Step 3 is as follows: Calculate the horizontal velocity vector v of the wheel center based on the acquired longitudinal speed of the vehicle i : v i = v c + ω r × x i ; where v c represents the horizontal velocity vector of the vehicle's center of mass, ω r represents the vehicle's yaw angular velocity vector, x i represents the projection vector on the horizontal plane of the vector starting from the vehicle's center of mass and ending at the wheel center; According to the horizontal velocity vector v of the wheel center i Calculate the horizontal velocity v during pure rolling of the wheel pi : v pi = v i ·(cosδ i , sinδ i , 0); where δ i represents the steering angle of the wheel; According to the horizontal speed v of the wheel during pure rolling pi calculate the slip rate λ of the wheel i : wherein, the linear velocity v of the tire = ω i r, ω i is the rotational speed of the tire, and r is the radius of the tire; The anti-slip torque T of the wheel in the third step asi has the following calculation formula: where λ u represents the maximum allowable wheel slip ratio, λ l represents the minimum allowable wheel slip ratio, λ i , are respectively the wheel slip / sliding ratio and its derivative with respect to time, k pi , K pi , k di , K di , h i , H i , c i , C i are control gains and are all greater than 0, and sat() is the saturation function.

4. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 1, characterized in that: The specific determination method of the inequality constraints of the wheel torques in Step 4 is: Determine the anti-slip torque T of the wheel at the current moment asi (k) whether it is 0, the anti-slip torque T of the wheel at the current moment asi When (k) is 0, the torque T of the wheel i The inequality constraint of (k) is as follows: |T i (k)| ≤ min{T mi (k), T ui (k)}; where T i (k) represents the wheel torque, where i takes the value of 1 or 2, representing the left front wheel torque and the right front wheel torque respectively; k represents the current moment; T mi (k) is 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 the tire adhesion at the current moment and satisfies: T ui (k) = min{F zi (k)r, T ui (k - 1)+T r}; where F zi (k) is the vertical load of the wheel at the current moment, r is the wheel radius, T ui (k - 1) is the maximum wheel torque determined by the tire adhesion at the previous moment, T r is the restoring torque; 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 constraint of (k) is as follows: |T i (k)| ≤ min{T mi (k), T ui (k)}; where T mi (k) is the maximum wheel torque determined by the operating characteristics of the drive motor at the current moment, and T ui (k) is the maximum wheel torque determined by the tire adhesion at the current moment and satisfies: T ui T(k) = |T pi (k - 1) + T ci (k - 1) - T asi (k)|; where T pi (k - 1) is the initial torque of the wheel at the previous moment, and T ci (k - 1) is the compensation torque of the wheel at the previous moment.

5. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 4, characterized in that: The specific judgment method in Step 5 for judging whether the inequality constraints of the torques of each wheel meet the requirements of the additional yaw moment demand and the total longitudinal force demand by analyzing the feasible region is: Analytically calculate the four boundary lines L formed by the additional yaw moment demand W and the total longitudinal force demand W in the two-dimensional feasible region composed of the left front wheel torque and the right front wheel torques T1 and T2 M T = rΔM d and the total longitudinal force demand W F T = rF xsumd where W e1 , L e2 , L e3 , L e4 , and W F = [cosδ f cosδ f 1 1], W M = [asinδ f -lcosδ f asinδ f +lcosδ f -l -l], δ f is the desired front wheel steering angle Simultaneously obtain the coordinates of the four boundary vertices p generated by the intersection of the four boundary lines e1 , p e2 , p e3 , p e4 . In the two-dimensional feasible region formed by the left front wheel torque and the right front wheel torques T1 and T2, analytically calculate the four boundary lines L1, L2, L3, and L4 formed by the value range of the left front wheel torque |T1| ≤ min{T m1 , T u1} and the value range of the right front wheel torque |T2| ≤ min{T m2 , T u2}: Simultaneously obtain the coordinates of the four boundary vertices p1, p2, p3, and p4 generated by the intersection of the four boundary lines, and analytically calculate only the additional yaw moment requirement W in 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 Form two boundary lines L m1 , L m2 : Among them, T m1 , T m2 , T m3 , T m4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the working characteristics of the drive motor at the current moment. T u1 , T u2 , T u3 , T u4 respectively represent the maximum wheel torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel determined by the tire adhesion at the current moment. T1, T2, T3, and T4 respectively represent the torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment. a is the longitudinal distance from the center of the front axle to the vehicle's center of mass, b is the longitudinal distance from the center of the rear axle to the vehicle's center of mass, l is half of the wheelbase, δ f is the desired front wheel angle, r is the tire rolling radius, F xsumd is the desired total longitudinal force, and ΔM d is the desired additional yaw moment; When point p e1 , p e2 , p e3 , p e4 contains a point that satisfies being within the region between parallel lines L1 and L2 and between parallel lines L3 and L4, or among points p1, p2, p3, p4 there exists a point that satisfies being within the region between parallel lines L e1 , L e2 and between parallel lines L e3 , L e4 , the inequality constraint for determining the wheel torque can satisfy the additional yaw moment demand and the total longitudinal force demand; When point p e1 , p e2 , p e3 , p e4 there is no point within the region that satisfies being between the parallel lines L1 and L2 and between the parallel lines L3 and L4, and there is no point among points p1, p2, p3, p4 that satisfies being within the region between the parallel lines L e1 , L e2 and between the parallel lines L e3 , L e4 and there is a point among p1, p2, p3, p4 that satisfies being within the region between the parallel lines L m1 , L m2 then it is determined that the inequality constraint of the wheel torque can meet the additional yaw moment requirement but cannot meet the total longitudinal force requirement; When point p e1 , p e2 , p e3 , p e4 contains no points that satisfy being within the region between parallel lines L1 and L2 and between parallel lines L3 and L4, and among points p1, p2, p3, p4, there are no points that satisfy being within the region between parallel lines L e1 , L e2 and between parallel lines L e3 , L e4 , and among p1, p2, p3, p4, there are no points that satisfy being within the region between parallel lines L m1 , L m2 , it is determined that the inequality constraint of the wheel torque cannot meet the additional yaw moment requirement; The specific method for judging whether a point is located in the region between two parallel lines is: 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, it is determined that the point is located in the region between the two parallel lines; when |d1| + |d2| > D, it is determined that the point is located outside the region between the two parallel lines.

6. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 1, characterized in that: The specific process of the method in Step 6 is: When the inequality constraints of the wheel torque can meet the requirements of the additional yaw moment and the total longitudinal force, a quadratic programming problem is established with the compensation torques T ci of the four tires as the optimization variables to minimize the sum of the squares of the ratio of the tire compensation torque T ci to the tire vertical load F zi , with the requirements of the desired total longitudinal force and the desired additional yaw moment and the wheel torque inequality as constraints: When the inequality constraint of the wheel torque can meet the additional yaw moment demand but cannot meet the total longitudinal force demand, a quadratic programming problem is established with the compensation torques T of the four tires ci as the optimization variables, maximizing the satisfaction of the total longitudinal force demand as the optimization objective, and the demand for the desired additional yaw moment and the wheel torque inequality as the constraints: When the inequality constraint of wheel torque cannot meet the additional yaw moment requirement, a quadratic programming problem is established with the compensation torques T of the four tires ci as the optimization variables, the maximum satisfaction of the additional yaw moment control requirement as the optimization objective, and the wheel torque inequality as the constraint Among these three quadratic programming problems: T c = [T c1 T c2 T c3 T c4 Τ ;​ T as = [T as1 T as2 T as3 T as4 Τ ;​ W F = [cosδ f cosδ f 11]; W M = [asinδ f - lcosδ f asinδ f + lcosδ f - l l]; F z1 、F z2 、F z3 、F z4 respectively represent the vertical loads of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T c1 、T c2 、T c3 、T c4 respectively represent the compensation torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T as1 、T as2 、T as3 、T as4 respectively represent the anti-skid torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment, T p1 、T p2 、T p3 、T p4 respectively represent the initial torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel at the current moment.

7. A torque distribution method for a distributed drive vehicle without road surface adhesion information perception according to claim 1, characterized in that: Desired torque T of each wheel i (k) is calculated as follows: T i T(k) = T pi T(k) - T asi T(k) + T ci T(k); where, T pi (k) is the initial torque of the wheel at the current moment, T asi (k) is the anti-slip torque of the wheel at the current moment, T ci (k) is the compensation torque of the wheel at the current moment.

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