A method, device and vehicle for calculating a yaw rate of a four-wheel steering vehicle

Abstract

The application discloses a kind of four-wheel steering vehicle yaw angular velocity calculation method, equipment, vehicle.Belongs to vehicle technical field.The method comprises: obtaining the target parameter of vehicle, wherein the target parameter includes front wheel steering angle, rear wheel steering angle and vehicle speed;According to the target parameter of the vehicle and yaw angular velocity calculation formula determines yaw angular velocity, wherein the yaw angular velocity calculation formula is determined according to the two-degree-of-freedom vehicle dynamics model of introducing front wheel steering angle and rear wheel steering angle.This application introduces front wheel steering angle and rear wheel steering angle based on two-degree-of-freedom vehicle dynamics model, makes it more suitable for four-wheel steering vehicle, improves the calculation accuracy of yaw angular velocity.This application covers reverse steering and same direction steering scene by unified formula, simplifies calculation process, improves efficiency.This application corrects the influence of cornering stiffness and vehicle speed by characteristic vehicle speed and dynamic gain coefficient self-adaption.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vehicles, and particularly relates to a four-wheel steering vehicle yaw rate calculation method, device and vehicle. BACKGROUND

[0002] The traditional vehicle yaw rate calculation is based on a two-wheel steering (front wheel steering) model. The model ignores the tire side slip angle and rear wheel steering effect at high speed or in complex working conditions, resulting in insufficient control accuracy. With the popularization of four-wheel steering technology, rear wheel steering can significantly improve the dynamic performance of the vehicle. The existing method has low calculation accuracy for the yaw rate of the four-wheel steering vehicle. SUMMARY

[0003] An object of the present application is to provide a four-wheel steering vehicle yaw rate calculation method, device and vehicle, which can solve the technical problem of low calculation accuracy of the yaw rate of the four-wheel steering vehicle in the prior art.

[0004] According to a first aspect of the present application, a four-wheel steering vehicle yaw rate calculation method is provided, comprising:

[0005] Obtaining target parameters of the vehicle, wherein the target parameters include a front wheel steering angle, a rear wheel steering angle and a vehicle speed;

[0006] Determining a yaw rate according to the target parameters of the vehicle and a yaw rate calculation formula, wherein the yaw rate calculation formula is determined according to a two-degree-of-freedom vehicle dynamics model introducing the front wheel steering angle and the rear wheel steering angle.

[0007] Optionally, the yaw rate calculation formula is:

[0008] ;

[0009] wherein, is the yaw rate, is the vehicle speed, denotes the front wheel steering angle, denotes the rear wheel steering angle, denotes a dynamic gain coefficient, is a characteristic vehicle speed, denotes the distance between the front axle and the rear axle of the vehicle.

[0010] Optionally, the dynamic gain coefficient is denoted as:

[0011] ;

[0012] wherein, denotes the mass of the vehicle, denotes the vehicle speed, denotes the distance from the vehicle center of mass to the rear axle of the vehicle, denotes the rear wheel cornering stiffness, denotes the distance between the front axle and the rear axle of the vehicle.

[0013] Optionally, the characteristic vehicle speed denotes the characteristic vehicle speed,

[0014] ;

[0015] wherein, denotes the front wheel cornering stiffness, denotes the rear wheel cornering stiffness, denotes the distance between the front axle and the rear axle of the vehicle, denotes the mass of the vehicle, denotes the distance from the vehicle center of mass to the front axle of the vehicle, denotes the distance from the vehicle center of mass to the rear axle of the vehicle.

[0016] Optionally, the method further comprises:

[0017] In the reverse steering mode, the rear wheel steering angle is less than zero, the dynamic gain coefficient is increased to improve the yaw rate.

[0018] Optionally, the method further comprises:

[0019] In the same direction steering mode, the rear wheel steering angle is greater than zero, when the yaw rate is zero, the vehicle enters the crab mode, the rear wheel steering angle is determined according to the following formula:

[0020] ;

[0021] wherein, denotes the front wheel cornering stiffness, denotes the rear wheel cornering stiffness, denotes the distance between the front axle and the rear axle of the vehicle, denotes the distance from the vehicle center of mass to the rear axle of the vehicle, denotes the front wheel steering angle.

[0022] Optionally, the determination process of the yaw rate calculation formula is as follows:

[0023] Based on a two-degree-of-freedom vehicle dynamics model, the front wheel steering angle and the rear wheel steering angle are introduced to establish the lateral force balance and yaw moment balance equations;

[0024] The lateral force balance and yaw moment balance equations are solved in combination with the steady-state condition to determine the yaw rate calculation formula.

[0025] Optionally, the lateral force balance and yaw moment balance equations are expressed as follows:

[0026] ;

[0027] ;

[0028] wherein, represents the mass of the vehicle, represents the vehicle speed, represents the mass center side slip angle, represents the mass center side slip angle rate of change, represents the yaw rate of the vehicle, represents the yaw rate rate of change, represents the front wheel side slip stiffness, represents the front wheel steering angle, represents the distance from the vehicle mass center to the front axle of the vehicle, represents the rear wheel side slip stiffness, represents the rear wheel steering angle, represents the distance from the vehicle mass center to the rear axle of the vehicle, represents the moment of inertia of the vehicle along the Z axis.

[0029] According to a second aspect of the present application, an electronic device is provided, comprising a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions being executed by the processor to implement the steps of a four-wheel steering vehicle yaw rate calculation method according to the first aspect of the present application.

[0030] According to a third aspect of the present application, a vehicle is provided, comprising an electronic device according to the second aspect of the present application.

[0031] The present application has the beneficial effect that the present application introduces front wheel steering angle and rear wheel steering angle based on a two-degree-of-freedom vehicle dynamics model, making it more suitable for four-wheel steering vehicles and improving the calculation accuracy of yaw rate. The present application covers reverse steering and same direction steering scenarios through a unified formula, simplifying the calculation process and improving efficiency. The present application adaptively corrects the influence of side slip stiffness and vehicle speed through characteristic vehicle speed and dynamic gain coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a flowchart of a four-wheel steering vehicle yaw rate calculation method according to the present application. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0034] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0035] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0037] In the specification of this invention, the terms "first" and "second" may explicitly or implicitly include one or more of the same feature. In the description of this invention, unless otherwise stated, "multiple" means two or more. Furthermore, in the specification, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0038] The existing four-wheel steering control methods have the following problems: (1) They do not take into account the dynamic image of the yaw rate of the rear wheel steering mode in the same direction / opposite direction; (2) They do not combine the characteristic vehicle speed to correct the coupling effect of the lateral stiffness and the center of gravity position; (3) They lack stability control strategies in the crab mode.

[0039] like Figure 1 As shown in the figure, this embodiment introduces a method for calculating the yaw rate of a four-wheel steering vehicle, including steps 1100-1200.

[0040] Step 1100: Obtain the target parameters of the vehicle, wherein the target parameters include the front wheel steering angle, the rear wheel steering angle, and the vehicle speed.

[0041] Step 1200: Determine the yaw rate based on the target parameters of the vehicle and the yaw rate calculation formula, wherein the yaw rate calculation formula is determined based on a two-degree-of-freedom vehicle dynamics model that incorporates the front wheel steering angle and the rear wheel steering angle.

[0042] The vehicle in the application is a four-wheel steering vehicle, and the four wheels of the four-wheel steering vehicle can all steer. For a traditional two-degree-of-freedom vehicle dynamics model, only the front wheel steering angle is considered, and it is not applicable to the four-wheel steering vehicle. The two-degree-of-freedom vehicle dynamics model is extended in the application, and the front wheel steering angle and the rear wheel steering angle are introduced to adapt to the four-wheel steering vehicle.

[0043] Specifically, the determination process of the yaw rate calculation formula is as follows: based on the two-degree-of-freedom vehicle dynamics model, the front wheel steering angle and the rear wheel steering angle are introduced to establish the lateral force balance and yaw moment balance equation; the lateral force balance and yaw moment balance equation are solved in combination with the steady-state condition to determine the yaw rate calculation formula.

[0044] The lateral force balance and yaw moment balance equation is expressed as follows:

[0045] ;

[0046] ;

[0047] wherein, m represents the mass of the vehicle, v represents the vehicle speed, β represents the mass center side slip angle, β represents the mass center side slip angle, r represents the yaw rate of the vehicle, r represents the yaw rate of the vehicle, Cf represents the front wheel side stiffness, δf represents the front wheel steering angle, L represents the distance from the vehicle mass center to the front axle of the vehicle, Cr represents the rear wheel side stiffness, δr represents the rear wheel steering angle, L represents the distance from the vehicle mass center to the rear axle of the vehicle, Iz represents the moment of inertia of the vehicle along the Z axis.

[0048] Under the steady-state condition, , , the steady-state condition is brought into the above equation to obtain the yaw rate calculation formula:

[0049] ;

[0050] wherein, r represents the yaw rate, v represents the vehicle speed, δf represents the front wheel steering angle, δr represents the rear wheel steering angle, K represents the dynamic gain coefficient, v represents the characteristic vehicle speed, denotes the distance between the front axle of the vehicle and the rear axle of the vehicle.

[0051] dynamic gain factor denotes:

[0052] ;

[0053] wherein, denotes the mass of the vehicle, denotes the vehicle speed, denotes the distance between the center of mass of the vehicle and the rear axle of the vehicle, denotes the rear wheel cornering stiffness, denotes the distance between the front axle of the vehicle and the rear axle of the vehicle.

[0054] In the yaw rate calculation formula, the rear wheel steering angle contributes to the yaw rate is related to the dynamic gain factor. The dynamic gain factor is proportional to the square of the vehicle speed, so that the contribution of the rear wheel steering angle changes nonlinearly with the vehicle speed, which can optimize the high / low speed performance.

[0055] characteristic vehicle speed denotes:

[0056] ;

[0057] wherein, denotes the front wheel cornering stiffness, denotes the rear wheel cornering stiffness, denotes the distance between the front axle of the vehicle and the rear axle of the vehicle, denotes the mass of the vehicle, denotes the distance between the center of mass of the vehicle and the front axle of the vehicle, denotes the distance between the center of mass of the vehicle and the rear axle of the vehicle.

[0058] The characteristic vehicle speed includes the front wheel cornering stiffness, the rear wheel cornering stiffness, the distance between the center of mass of the vehicle and the front axle of the vehicle, and the distance between the center of mass of the vehicle and the rear axle of the vehicle, reflecting the coupling effect of the center of mass position and the cornering stiffness.

[0059] In this embodiment, the method further comprises: in the reverse steering mode, the rear wheel steering angle is less than zero, and the dynamic gain factor is increased to improve the yaw rate.

[0060] In the same direction steering mode, the rear wheel steering angle is greater than zero, when the yaw rate is zero, the vehicle enters the crab mode, and the rear wheel steering angle is determined according to the following formula:

[0061] ;

[0062] wherein, represents the front wheel side slip stiffness, represents the rear wheel side slip stiffness, represents the distance between the front axle of the vehicle and the rear axle of the vehicle, represents the distance between the vehicle center of mass and the rear axle of the vehicle, represents the front wheel steering angle.

[0063] For a four-wheel steering vehicle, the steering mode includes a reverse steering mode and a same direction steering mode. In the reverse steering mode, the rear wheels are steered in the opposite direction of the front wheels, such as the front wheels turning left while the rear wheels turning right. The reverse steering mode is suitable for low-speed driving scenarios. The reverse steering mode can reduce the turning radius and improve the flexibility of the vehicle.

[0064] In the same direction steering mode, the rear wheels are steered in the same direction of the front wheels, such as the front wheels turning left while the rear wheels also turning left. The same direction steering mode is suitable for high-speed driving scenarios. The same direction steering mode can improve the stability of the vehicle and reduce the body roll.

[0065] In the present invention, the switching between the reverse steering mode and the same direction steering mode is realized by switching the sign of the rear wheel steering angle In the reverse steering mode, the rear wheel steering angle is less than zero. By increasing the dynamic gain coefficient to improve the yaw angular velocity, it can be used for emergency obstacle avoidance.

[0066] In the same direction steering mode, the rear wheel steering angle is greater than zero, and the stability is maintained by the center of mass side slip angle control and lateral acceleration limitation. According to the rear wheel steering angle formula in crab mode, pure lateral translation is ensured.

[0067] The present invention introduces the front wheel steering angle and the rear wheel steering angle on the basis of the two-degree-of-freedom vehicle dynamics model, making it more suitable for four-wheel steering vehicles and improving the calculation accuracy of the yaw angular velocity. The present invention covers the reverse steering and same direction steering scenarios by a unified formula, simplifies the calculation process, and improves the efficiency. The present invention adaptively corrects the influence of the side slip stiffness and the vehicle speed by the characteristic vehicle speed and the dynamic gain coefficient.

[0068] The present embodiment introduces an electronic device, which includes a processor and a memory, the memory stores programs or instructions that can run on the processor, and the programs or instructions are executed by the processor to realize the steps of a four-wheel steering vehicle yaw angular velocity calculation method according to any embodiment of the present invention.

[0069] The present embodiment introduces a vehicle, which includes an electronic device according to the above embodiments of the present invention.

[0070] Although some specific embodiments of the present application have been described in detail by way of example with reference to the drawings, it is to be understood that the above examples are intended to be illustrative only and the application is not limited to those examples. It will be apparent to those skilled in the art that various modifications, adaptations and variations can be made to the above embodiments without departing from the scope and spirit of the application.

[0071] Those of skill in the art would understand that the modules and algorithm steps described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or combinations of both. The disclosure encompasses both hardware and software implementations of the disclosed embodiments. The functionality of the disclosed embodiments can be performed by various hardware and / or software components or modules, which can be combined into one or more modules. The functionality can also be performed by one or more processors and / or state machines. The one or more processors measures parameters and / or operates on parameters, and can do so in conjunction with software modules that can be used for implementing the disclosed embodiments.

[0072] Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. The disclosure encompasses both hardware and software implementations of the disclosed embodiments. The functionality of the disclosed embodiments can be performed by various hardware and / or software components or modules, which can be combined into one or more modules. The functionality can also be performed by one or more processors and / or state machines. The one or more processors measures parameters and / or operates on parameters, and can do so in conjunction with software modules that can be used for implementing the disclosed embodiments.

[0073] In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method can be implemented in other manners. For example, the described embodiments of the apparatus are merely schematic. For example, the division of the modules is merely logical function division. There can be another division manner for the actual implementation, for example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between different modules can be indirect couplings or communication connections through some interfaces, and can be in electrical, mechanical or other forms.

[0074] The modules illustrated as separate components can or can not be physically separate, and the components illustrated as modules can or can not be physical modules, i.e., can be located in one place, or can be distributed on multiple network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the embodiments of the present application.

[0075] In addition, each functional module in the embodiments of the present application can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0076] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in the embodiments of the present application. The aforementioned storage medium includes various media that can store program codes, such as a U disk, a mobile hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

[0077] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combinations of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by replacing the above features with the technical features disclosed in the present application (but not limited to) having similar functions.

[0078] It should be understood that the size of the serial number of the steps in the summary and the embodiments of the present application does not absolutely mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The foregoing description of the implementation of the present disclosure has been given for the purpose of illustration and description. The foregoing description is not exhaustive and does not limit the present disclosure to the exact form disclosed. Various modifications and changes can also be made according to the above teachings, or can be obtained from the practice of the present disclosure. These embodiments are chosen and described to explain the principles of the present disclosure and its practical application, so that those skilled in the art can utilize the present disclosure in various embodiments and various modifications suitable for the specific use of the concept.

Claims

1. A method of calculating a yaw rate of a four-wheel steering vehicle, characterized by, The method comprises: acquiring target parameters of the vehicle, wherein the target parameters comprise a front wheel steering angle, a rear wheel steering angle, and a vehicle speed; calculating a yaw rate according to the target parameters of the vehicle and a yaw rate calculation formula, wherein the yaw rate calculation formula is determined according to a two-degree-of-freedom vehicle dynamics model introducing the front wheel steering angle and the rear wheel steering angle; the yaw rate calculation formula is as follows: ； wherein, is a yaw angular velocity, is a vehicle speed, denotes a front wheel steering angle, denotes a rear wheel steering angle, denotes a dynamic gain coefficient, is a characteristic vehicle speed, denotes a distance between a front axle of the vehicle and a rear axle of the vehicle; The dynamic gain coefficient is expressed as: ； wherein, represents the mass of the vehicle, represents the vehicle speed, represents the distance from the vehicle center of mass to the rear axle of the vehicle, represents the rear wheel side slip stiffness, represents the distance from the front axle of the vehicle to the rear axle of the vehicle.

2. The method of claim 1, wherein, The characteristic vehicle speed is represented as: ； wherein, represents the front wheel cornering stiffness, represents the rear wheel cornering stiffness, represents the distance between the front axle of the vehicle and the rear axle of the vehicle, represents the mass of the vehicle, represents the distance between the center of mass of the vehicle and the front axle of the vehicle, represents the distance between the center of mass of the vehicle and the rear axle of the vehicle.

3. The method of claim 1, wherein, The method further comprises: In the reverse steering mode, the rear wheel steering angle is less than zero, the dynamic gain coefficient is increased to increase the yaw rate.

4. The method of claim 3, wherein, The method further comprises: In the same direction turning mode, the rear wheel turning angle is greater than zero, when the yaw rate is zero, the vehicle enters the crab mode, the rear wheel turning angle is determined according to the following formula: ； wherein, represents the front wheel cornering stiffness, represents the rear wheel cornering stiffness, represents the distance between the front axle of the vehicle and the rear axle of the vehicle, represents the distance between the center of mass of the vehicle and the rear axle of the vehicle, represents the front wheel steering angle.

5. The method of claim 1, wherein, The determination process of the yaw rate calculation formula is as follows: Based on a two-degree-of-freedom vehicle dynamics model, the front wheel steering angle and the rear wheel steering angle are introduced to establish a lateral force balance and yaw moment balance equation; The lateral force balance and yaw moment balance equation is solved in combination with a steady-state condition to determine the yaw rate calculation formula.

6. The method of claim 5, wherein, The lateral force balance and yaw moment balance equation is expressed as follows: ； ； wherein, denotes the mass of the vehicle, denotes the vehicle speed, denotes the mass center side slip angle, denotes the mass center side slip angle rate of change, denotes the yaw rate of the vehicle, denotes the yaw rate rate of change, denotes the front wheel side slip stiffness, denotes the front wheel steering angle, denotes the distance from the vehicle mass center to the vehicle front axle, denotes the rear wheel side slip stiffness, denotes the rear wheel steering angle, denotes the distance from the vehicle mass center to the vehicle rear axle, denotes the moment of inertia of the vehicle along the Z axis.

7. An electronic device, comprising: The electronic device comprises a processor and a memory, wherein the memory stores programs or instructions executable on the processor, and the programs or instructions are executed by the processor to implement the steps of the four-wheel steering vehicle yaw rate calculation method according to any one of claims 1 to 6.

8. A vehicle characterized by comprising: The electronic device comprises the electronic device according to claim 7.

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