Tire force vector distribution control method, medium and equipment based on safety mechanism min-max game optimization

Abstract

The invention discloses a control method, medium and equipment for optimizing tire force vector distribution based on a safety mechanism min-max game, and belongs to the field of distributed driving electric vehicle control. According to the method, in order to realize collaborative optimization of multiple targets, a'safety mechanism 'is added in a Min-Max multi-target optimization framework, and the tire utilization rate is used as the highest priority and is constrained through a Barrier function; and meanwhile, error indexes (longitudinal, lateral and yawing moments) are moderately relaxed by adopting soft constraint (Slack), so that the system can tolerate part of tracking deviation under necessary conditions, and the dynamic performance and safety redundancy of the vehicle are considered while the tire adhesive force is fully utilized.

Description

Technical Field

[0001] The present invention belongs to the field of distributed drive electric vehicle control, and specifically relates to a tire force vector distribution control method, medium and equipment based on a safety mechanism min-max game optimization. Background Art

[0002] Currently, research on tire force vectoring in electric wheel-drive vehicles focuses on its integration with torque vectoring strategies, with an emphasis on the distribution of longitudinal tire force. A common approach is to calculate the required longitudinal force and convert it into the output torque of the drive motor for control. Tire lateral force regulation typically relies on front wheel angle control. While some studies have considered the impact of tire utilization, most focus solely on minimizing the combined utilization of all four wheels. This strategy tends to overlook the actual needs of individual wheels, potentially leading to saturation of a particular tire and thus compromising vehicle stability and safety. Furthermore, under varying road adhesion conditions, the coupling effect of lateral and longitudinal forces on vehicle dynamic performance is significant. Failure to properly coordinate the distribution of these forces in the control strategy will adversely affect the vehicle's handling stability.

[0003] In vehicle control, how to accurately track the desired longitudinal force, lateral force, and yaw moment while ensuring safety under extreme vehicle conditions is a core research challenge in the field of intelligent driving and active safety. Because tire longitudinal force, lateral force, and torque requirements compete with each other, when the vehicle's available adhesion conditions are limited, simply pursuing a single goal (such as maximum longitudinal acceleration or precise yaw moment tracking) can easily lead to other requirements being neglected or problems such as oversaturation of a single tire. Therefore, it is urgent to consider controlling the longitudinal and lateral forces of the vehicle's tires solely through drive torque to improve the stability of the entire vehicle, and to design a reasonable tire force vectoring control strategy based on the tire's state under different adhesion conditions. Summary of the Invention

[0004] The present invention addresses the shortcomings of the existing technology and provides a tire force vector distribution control method, medium, and device based on a safety mechanism, min-max game optimization. To achieve multi-objective coordinated optimization, the present invention adds a "safety mechanism" to the Min-Max multi-objective optimization framework, prioritizing tire utilization and constraining it through a barrier function. At the same time, soft constraints (Slack) are used to moderately relax error indicators (longitudinal, lateral, and yaw moments), allowing the system to tolerate some tracking deviations when necessary. This fully utilizes tire adhesion while also taking into account vehicle dynamics performance and safety redundancy.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a tire force vector distribution control method based on a safety mechanism min-max game optimization, comprising the following steps:

[0007] S1: Calculate the tracking difference based on the longitudinal force, lateral force and yaw moment applied to the four wheels and the expected longitudinal force;

[0008] S2: Calculate tire utilization while constraining the longitudinal and lateral forces on the wheels. Use the barrier function to constrain tire utilization, and maximize the tire utilization of the four wheels to obtain the maximum barrier.

[0009] S3: For the calculated tracking difference, use soft constraints to moderately relax and set the penalty function of the soft constraints;

[0010] S4: Integrate the maximum barrier and penalty function into the same min-max game optimization model to distribute tire force vectors and obtain the optimal distribution amount.

[0011] Optionally, in step S1, the calculation formula of the tracking difference is as follows:

[0012]

[0013] Where, e x 、e y and e z Represent the tracking differences of longitudinal force, lateral force and yaw moment respectively, F x 、F y and M z They represent the longitudinal force, lateral force and yaw moment of the vehicle in the direction of the earth, respectively. xd 、F yd and M zd They represent the longitudinal force, lateral force and yaw moment expected by the vehicle in the direction of the earth respectively.

[0014] Optionally, the longitudinal force F x , lateral force F y and yaw moment M z The calculation formula is as follows:

[0015]

[0016] Where B f and B r are the front and rear wheel tracks respectively; a and b are the distances from the center of mass to the front and rear axles respectively; f x,ij and f y,ijare the longitudinal force and lateral force at each tire contact point in the vehicle body coordinate system, respectively. The subscript ij takes values of 11, 12, 21, and 22, representing the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The expressions are as follows:

[0017]

[0018] Where, f tx,ij and f ty,ij Respectively represent the longitudinal force and lateral force of a single tire in the tire coordinate system, δ ij Indicates the four wheel angles.

[0019] Optionally, in step S2, the tire utilization rate η ij The calculation formula is:

[0020]

[0021] Where, f tx,ij and f ty,ij They represent the longitudinal force and lateral force of a single tire in the tire coordinate system, F tz,ij is the vertical load of a single tire, the subscript ij takes values of 11, 12, 21 and 22, representing the left front wheel, right front wheel, left rear wheel and right rear wheel respectively; μ is the ground adhesion coefficient.

[0022] Optionally, in step S2, an octagon inscribed in the friction circle is used to constrain the longitudinal force and lateral force on the wheel as follows:

[0023]

[0024] Where R c =R e cos22.5°, R e =μF tz,ij ;

[0025] Using the Barrier function h η The following constraints are imposed on tire utilization:

[0026]

[0027] Where k hs is within the safe area ij The proportionality coefficient; p η is the power operation coefficient; A η is the gain coefficient; η safe is the safety threshold of tire utilization.

[0028] Optionally, in step S2, the maximum BarrierH s for:

[0029]

[0030] Optionally, in step S3, after introducing the soft constraint, the constraint range of the tracking difference is as follows:

[0031]

[0032] Where, e x 、e y and e z Represent the tracking differences of longitudinal force, lateral force and yaw moment, Δ ex , Δ ey and Δ ez is the corresponding allowable error boundary, ε ex , ε ey and ε ez is the corresponding soft constraint variable;

[0033] Design the penalty function E of the soft constraint s as follows:

[0034] E s =max(w ex ε ex ,w ey ε ey ,w ez ε ez );

[0035] Where w ex 、w ey and w ez are all weight coefficients.

[0036] Optionally, in step S4, when the min-max game optimization model is used to distribute tire force vectors, if there is a set of Make max(H s ,E s ) is minimized, then is the optimal allocation; and Respectively represent f tx,ij and f ty,ij The solution, and Represents ε ex , ε ey and ε ez The solution.

[0037] In a second aspect, the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program enables a computer to execute the tire force vector distribution control method based on the safety mechanism min-max game optimization as described in the first aspect.

[0038] In a third aspect, the present invention provides an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the tire force vector distribution control method based on the safety mechanism min-max game optimization as described in the first aspect is implemented.

[0039] The present invention achieves the following beneficial effects: By optimizing tire force vector distribution based on a safety mechanism, min-max game theory, and addressing the vehicle's longitudinal and lateral forces, the invention achieves independent control of longitudinal and lateral forces, ensuring the vehicle's lateral stability while maximizing the tire's lateral force performance. Furthermore, the invention minimizes errors while ensuring tire safety, only compromising tracking accuracy when unavoidable. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of the tire force vector distribution control method based on the min-max game optimization of the safety mechanism.

[0041] Figure 2 It is a schematic diagram of tire adhesion constraint. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0043] In one embodiment, the present invention proposes a tire force vector distribution control method based on a safety mechanism min-max game optimization, the specific process is as follows: Figure 1 As shown, the following steps are included:

[0044] S1: The upper controller obtains the desired longitudinal force, lateral force, and yaw moment of the vehicle in the direction of the earth and calculates the tracking difference.

[0045] Since 4WIDS EV can achieve independent control of the longitudinal and lateral forces of the four wheels through torque regulation and steering control, the difference between the actual total longitudinal force, lateral force, and yaw moment of the four wheels and the expected force and moment is defined as:

[0046]

[0047] Among them, F x 、F y and M z is the longitudinal force, lateral force and yaw moment acting on the vehicle in the direction of the earth, F xd 、F yd and M zd It is the longitudinal force, lateral force and yaw moment expected by the vehicle in the direction of the earth, obtained by the upper controller.

[0048] The actual generalized total longitudinal force F of the vehicle x , lateral force F y and yaw moment M z The expressions are:

[0049]

[0050] Where B f and B r are the front and rear wheel tracks respectively; a and b are the distances from the center of mass to the front and rear axles respectively; f x,ij and f y,ij are the longitudinal force and lateral force at the contact point of each tire in the vehicle body coordinate system, respectively. The subscript ij takes values of 11, 12, 21, and 22, representing the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively.

[0051] Due to the four wheel turning angles δ ij and the four tire longitudinal forces f x,ij All are independently controllable, and the longitudinal force f of a single tire in the tire coordinate system tx,ij With the lateral force f ty,ij The expressions of the longitudinal force and lateral force at each tire contact point in the vehicle body coordinate system are:

[0052]

[0053] S2: Calculate tire utilization while constraining the longitudinal and lateral forces on the wheels. Use the barrier function to constrain the tire utilization. Maximizing the tire utilization of the four wheels yields the maximum barrier.

[0054] The utilization formula of a single wheel is:

[0055]

[0056] Where, F tz,ij is the vertical load of a single tire, and μ is the ground adhesion coefficient.

[0057] During the tire distribution process, due to the constraints of adhesion conditions, the longitudinal force and lateral force of the tire should satisfy the friction circle constraint. However, directly using the friction circle as a constraint to solve the tire force distribution will introduce a quadratic nonlinear optimization problem, which not only increases the computational complexity but also makes the solution process more cumbersome. In order to solve this problem and reduce the computational burden to improve the solution efficiency, as shown in the following example: Figure 2 As shown, this embodiment uses an inscribed octagon of the friction circle to approximate the tire adhesion constraint, converting the quadratic constraint into a linear constraint. e =μF tz,ij , Rc =R e cos22.5°, the octagonal constraint can be described as:

[0058]

[0059] In order to avoid vehicle instability caused by excessive saturation of a single wheel under extreme working conditions, safety constraints are imposed on tire utilization and longitudinal force, lateral force, and yaw moment tracking errors under the min-max architecture. η Constrain the tire utilization rate. When the tire utilization rate is within the safe area; h η Keep it at a low level, and when the tire utilization exceeds the safety threshold, h η Will increase sharply to limit tire utilization saturation. It is defined as follows:

[0060]

[0061] Where k hs is within the safe area ij The proportionality coefficient; p η is the power operation coefficient, which is 3 here; A η is the gain coefficient, which is generally larger and accelerates the penalty; η safe is the safety threshold of tire utilization; η ij Indicates tire utilization.

[0062] Taking the maximum tire utilization of the four wheels can get the maximum BarrierH s :

[0063]

[0064] S3: Based on the difference between the actual total longitudinal force, lateral force, yaw moment and the expected force and moment of the four wheels, soft constraints are used for moderate relaxation, and a penalty function E is set. s .

[0065] Therefore, the difference between the actual total longitudinal force, lateral force, yaw moment of the four wheels and the expected force and moment is defined as:

[0066]

[0067] In the tire force distribution process, in order to allow the vehicle to moderately relax the deviation of the reference force and torque when necessary, this embodiment adjusts the tire force distribution to the tire force. x 、e y With e z All adopt the soft constraint form, which allows the system to sacrifice a certain tracking accuracy in extreme cases to give priority to the safety index of tire utilization. x 、ey With e z The constraints are as follows:

[0068]

[0069] Where, Δ ex , Δ ey and Δ ez All are allowable error boundaries; ε ex , ε ey and ε ez All are soft constraint variables and are greater than or equal to 0.

[0070] If e x 、e y With e z If the soft constraint variable of any item is 0, it means that the tracking error of the item does not exceed the allowable error limit; if it is greater than 0, it means that the limit has been exceeded and a penalty constraint is required. Therefore, the penalty function for designing soft constraints is:

[0071] E s =max(w ex ε ex ,w ey ε ey ,w ez ε ez )

[0072] Where w ex 、w ey and w ez are all weight coefficients.

[0073] S4: Integrate the maximum barrier and penalty function into the same min-max game optimization model to optimize the tire force vector distribution based on the safety mechanism min-max game. If any tire utilization approaches the limit or the relaxation of any error is too large, the maximum value will be significantly increased, thereby adaptively seeking a compromise between safety and performance requirements. If there is a set of Make max(H s ,E s ) is minimized, then The optimal distribution amount.

[0074] In completing the maximum barrier H for tire utilization s and the soft constraint penalty function E s After design, this embodiment further integrates the two into the same min-max game optimization model, as shown below:

[0075]

[0076] If any tire utilization approaches the limit or the relaxation of any error is too large, the maximum value will be significantly increased, thereby adaptively seeking a compromise between safety and performance requirements: while ensuring tire safety, the error is minimized as much as possible, and tracking accuracy is relaxed only when it is unavoidable.

[0077] If there is a set Make max(H s ,E s ) is minimized, then The tire force distribution of this embodiment is now complete.

[0078] In another embodiment, the present invention provides a computer-readable storage medium storing a computer program, which enables a computer to execute the tire force vector distribution control method based on the safety mechanism min-max game optimization of the aforementioned embodiment.

[0079] In another embodiment, the present invention proposes an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the tire force vector distribution control method based on the safety mechanism min-max game optimization of the aforementioned embodiment is implemented.

[0080] In the embodiments disclosed herein, computer storage media can be tangible media that can contain or store programs for use by or in conjunction with an instruction execution system, device, or apparatus. Computer storage media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. More specific examples of computer storage media can include electrical connections based on one or more lines, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memory), optical fibers, portable compact disk read-only memories (CDROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0081] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0082] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A tire force vector distribution control method based on a safety mechanism min-max game optimization, characterized in that: The steps include: S1: Calculate the tracking difference based on the longitudinal force, lateral force and yaw moment applied to the four wheels and the expected longitudinal force; S2: Calculate tire utilization while constraining the longitudinal and lateral forces on the wheels. Use the barrier function to constrain tire utilization, and maximize the tire utilization of the four wheels to obtain the maximum barrier. S3: For the calculated tracking difference, use soft constraints to moderately relax and set the penalty function of the soft constraints; S4: Integrate the maximum barrier and penalty function into the same min-max game optimization model to distribute tire force vectors and obtain the optimal distribution amount.

2. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 1, characterized in that: In step S1, the calculation formula of the tracking difference is as follows: Where, e x 、e y and e z Represent the tracking differences of longitudinal force, lateral force and yaw moment respectively, F x 、F y and M z They represent the longitudinal force, lateral force and yaw moment of the vehicle in the direction of the earth, respectively. xd 、F yd and M zd They represent the longitudinal force, lateral force and yaw moment expected by the vehicle in the direction of the earth respectively.

3. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 2, characterized in that: Longitudinal force F x , lateral force F y and yaw moment M z The calculation formula is as follows: Where B f and B r are the front and rear wheel tracks respectively; a and b are the distances from the center of mass to the front and rear axles respectively; f x,ij and f y,ij are the longitudinal force and lateral force at each tire contact point in the vehicle body coordinate system, respectively. The subscript ij takes values of 11, 12, 21, and 22, representing the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. The expressions are as follows: Where, f tx,ij and f ty,ij Respectively represent the longitudinal force and lateral force of a single tire in the tire coordinate system, δ ij Indicates the four wheel angles.

4. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 1, characterized in that: In step S2, the tire utilization rate η ij The calculation formula is: Where, f tx,ij and f ty,ij They represent the longitudinal force and lateral force of a single tire in the tire coordinate system, F tz,ij is the vertical load of a single tire, the subscript ij takes values of 11, 12, 21 and 22, representing the left front wheel, right front wheel, left rear wheel and right rear wheel respectively; μ is the ground adhesion coefficient.

5. The tire force vector distribution control method based on safety mechanism min-max game optimization as claimed in claim 4, characterized in that: In step S2, the longitudinal and lateral forces acting on the wheel are constrained as follows using the inscribed octagon of the friction circle: Where R c =R e cos22.5°, R e =μF tz,ij ; Using the Barrier function h η The following constraints are imposed on tire utilization: Where k hs is within the safe area ij The proportionality coefficient; p η is the power operation coefficient; A η is the gain coefficient; η safe is the safety threshold of tire utilization.

6. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 5, characterized in that: In step S2, the maximum BarrierH s for:

7. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 6, characterized in that: In step S3, after introducing the soft constraint, the constraint range of the tracking difference is as follows: Where, e x 、e y and e z Represent the tracking differences of longitudinal force, lateral force and yaw moment, Δ ex , Δ ey and Δ ez is the corresponding allowable error boundary, ε ex , ε ey and ε ez is the corresponding soft constraint variable; Design the penalty function E of the soft constraint s as follows: E s =max(w ex e ex ,w ey e ey ,w ez e ez ); Where w ex 、w ey and w ez are all weight coefficients.

8. The tire force vector distribution control method based on safety mechanism min-max game optimization according to claim 7, characterized in that: In step S4, when the min-max game optimization model is used to allocate tire force vectors, if there is a set of Make max(H s ,E s ) is minimized, then is the optimal allocation; and Respectively represent f tx,ij and f ty,ij The solution, and Represents ε ex , ε ey and ε ez The solution.

9. A computer-readable storage medium storing a computer program, characterized in that: The computer program enables a computer to execute the tire force vector distribution control method based on safety mechanism min-max game optimization according to any one of claims 1 to 8.

10. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the tire force vector distribution control method based on the safety mechanism min-max game optimization is implemented as described in any one of claims 1 to 8.

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