Vehicle rear wheel steering control method, device and system and vehicle

Abstract

The invention discloses a vehicle rear wheel steering control method, device and system and a vehicle. The method comprises the steps that the average wheel steering angle of the vehicle is obtained; based on the wheel average turning angle and a preset mapping relation, the turning angle difference of the left rear wheel and the right rear wheel is determined, and the preset mapping relation is a mapping relation designed for enabling the Ackerman rate to reach a preset threshold value; determining respective turning angles of the left and right rear wheels based on the wheel average turning angle and the turning angle difference of the left and right rear wheels; and controlling a left rear wheel and a right rear wheel of the vehicle based on the respective turning angles of the left and right rear wheels. According to the vehicle rear wheel steering control method, device and system and the vehicle, the rear wheel steering angle is adjusted through a reasonable control strategy, the steering performance better than that of other rear wheel steering modes can be achieved, the ultimate road holding capacity of steering can be improved, tire abrasion can be reduced, and the low-temperature abnormal sound probability of tires can be reduced.

Description

Technical Field

[0001] The present application relates to the field of vehicle control technology, and more specifically to a vehicle rear wheel steering control method, device, system and vehicle. Background Art

[0002] At present, the most commonly used steering method in the market is front-wheel steering + rear-wheel follow-up steering, that is, the driver turns the steering wheel, and the steering wheel drives the steering tie rod to move laterally through the steering transmission system, causing the front wheels to deflect left and right, and the vehicle starts to turn. Due to the elastic deformation of the tires, the rear wheels produce follow-up steering. Since the rear wheels are follow-up steering, there is a phase difference between the front and rear wheel steering, which increases the vehicle's center of mass side slip angle, making the vehicle's handling stability worse.

[0003] As people's requirements for vehicle operation stability and safety become higher and higher, the shortcomings of front-wheel steering vehicles, such as poor low-speed steering flexibility and low high-speed steering stability, have led researchers to start researching new steering technologies. On this basis, four-wheel steering technology, i.e. front-wheel steering + rear-wheel steering, was born. In the current rear-wheel steering control scheme, there is no relevant control method to improve the steering Ackerman rate through rear-wheel steering. Summary of the invention

[0004] According to one aspect of the present application, a vehicle rear wheel steering control method is provided, the method comprising: obtaining an average wheel steering angle of the vehicle; determining a steering angle difference between left and right rear wheels based on the average wheel steering angle and a preset mapping relationship, wherein the preset mapping relationship is a mapping relationship designed to make the Ackerman rate reach a preset threshold value; determining respective steering angles of the left and right rear wheels based on the average wheel steering angle and the steering angle difference of the left and right rear wheels; and controlling the left and right rear wheels of the vehicle based on respective steering angles of the left and right rear wheels.

[0005] In an embodiment of the present application, obtaining the average wheel turning angle of the vehicle includes: obtaining a steering wheel angle signal, and obtaining the average turning angle of the left and right front wheels based on the steering wheel angle signal; and obtaining the average turning angle of the left and right rear wheels based on the average turning angle of the left and right front wheels.

[0006] In an embodiment of the present application, determining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship includes: obtaining the actual steering angle of the inner front wheel used for turning among the left and right front wheels based on the average steering angle of the left and right front wheels; obtaining the ideal steering angle of the inner front wheel when the Ackerman rate reaches 100% based on the actual steering angle of the inner front wheel; obtaining the steering angle difference between the left and right rear wheels based on the ideal steering angle of the inner front wheel and a first preset mapping relationship, wherein the first preset mapping relationship is a preset mapping relationship between the ideal steering angle of the inner front wheel and the steering angle difference between the left and right rear wheels.

[0007] In an embodiment of the present application, determining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship includes: obtaining the actual steering angle of the outer front wheel used for turning among the left and right front wheels based on the average steering angle of the left and right front wheels; obtaining the ideal steering angle of the outer front wheel when the Ackerman rate reaches 100% based on the actual steering angle of the outer front wheel; obtaining the steering angle difference between the left and right rear wheels based on the ideal steering angle of the outer front wheel and a second preset mapping relationship, wherein the second preset mapping relationship is a preset mapping relationship between the ideal steering angle of the outer front wheel and the steering angle difference between the left and right rear wheels.

[0008] In an embodiment of the present application, obtaining the average turning angle of the left and right rear wheels based on the average turning angle of the left and right front wheels includes: obtaining the vehicle speed of the vehicle; obtaining the proportionality coefficient between the average turning angle of the left and right rear wheels and the average turning angle of the left and right front wheels based on a preset function, wherein the independent variable of the preset function is the vehicle speed, and the dependent variable of the preset function is the proportionality coefficient; multiplying the average turning angle of the left and right front wheels by the proportionality coefficient to obtain the average turning angle of the left and right rear wheels.

[0009] In an embodiment of the present application, when the vehicle speed is less than a preset speed, the proportional coefficient is a negative number, and the turning direction of the left and right rear wheels is opposite to the turning direction of the left and right front wheels; when the vehicle speed is not less than the preset speed, the proportional coefficient is a positive number, and the turning direction of the left and right rear wheels is the same direction as the turning direction of the left and right front wheels.

[0010] In an embodiment of the present application, the respective turning angles of the left and right rear wheels are determined based on the average turning angle of the wheels and the turning angle difference between the left and right rear wheels, including: multiplying the turning angle difference between the left and right rear wheels by a preset coefficient to obtain a turning angle offset, wherein the preset coefficient is greater than 0 and less than 1; adding the turning angle offset to the average turning angle of the left and right rear wheels to obtain the turning angle of the inner rear wheel; and subtracting the turning angle offset from the average turning angle of the left and right rear wheels to obtain the turning angle of the outer rear wheel.

[0011] According to another aspect of the present application, a vehicle rear-wheel steering control device is provided, the control device comprising a memory and a processor, wherein the memory stores a computer executable program run by the processor, and when the computer executable program is run by the processor, the processor executes the above-mentioned vehicle rear-wheel steering control method.

[0012] According to another aspect of the present application, a vehicle rear-wheel steering control system is provided, the control system comprising a sensor, a left rear wheel steering gear, a right rear wheel steering gear and the above-mentioned vehicle rear-wheel steering control device, wherein: the vehicle rear-wheel steering control device is used to obtain the average wheel steering angle of the vehicle from the sensor, determine the respective steering angles of the left and right rear wheels based on the average wheel steering angle, generate a left rear wheel steering angle signal and a right rear wheel steering angle signal, and send the left rear wheel steering angle signal and the right rear wheel steering angle signal to the left rear wheel steering gear and the right rear wheel steering gear respectively; the left rear wheel steering gear is used to control the left rear wheel based on the left rear wheel steering angle signal; the right rear wheel steering gear is used to control the right rear wheel based on the right rear wheel steering angle signal.

[0013] According to another aspect of the present application, a vehicle is provided, wherein the vehicle comprises the above-mentioned vehicle rear-wheel steering control device or the above-mentioned vehicle rear-wheel steering control system.

[0014] According to another aspect of the present application, a storage medium is provided, on which a computer program executed by a processor is stored. When the computer program is executed by the processor, the processor executes the above-mentioned vehicle rear wheel steering control method.

[0015] According to another aspect of the present application, a computer program is provided. When the computer program is executed by a processor, the processor executes the above-mentioned vehicle rear wheel steering control method.

[0016] The vehicle rear-wheel steering control method, device, system and vehicle of the present application adjust the rear wheel steering angle through a reasonable control strategy, which can achieve better steering performance than other rear-wheel steering methods, improve the ultimate steering grip ability, reduce tire wear, and reduce the probability of abnormal noise caused by low temperature of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By describing the embodiments of the present application in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present application will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0018] Figure 1 A schematic flowchart of a vehicle rear wheel steering control method according to an embodiment of the present application is shown.

[0019] Figure 2 Schematic diagram of a vehicle showing ideal Alman rate steering without rear wheel steering.

[0020] Figure 3Schematic diagram of a vehicle showing non-ideal Alman rate steering without rear wheel steering.

[0021] Figure 4 An exemplary vehicle schematic diagram showing an ideal Alman rate steering achieved based on the vehicle rear wheel steering control method according to an embodiment of the present application.

[0022] Figure 5 A schematic diagram of a vehicle showing another example of achieving an ideal Alman rate steering based on a vehicle rear wheel steering control method according to an embodiment of the present application.

[0023] Figure 6 A schematic structural block diagram of a vehicle rear wheel steering control device according to an embodiment of the present application is shown.

[0024] Figure 7 A schematic structural block diagram of a vehicle rear-wheel steering control system according to an embodiment of the present application is shown.

[0025] Figure 8 A schematic operation flow chart of a vehicle rear wheel steering control system according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application more obvious, the example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the example embodiments described herein. Based on the embodiments of the present application described in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0027] In order to make the purpose, technical solutions and advantages of the present application more obvious, the example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the example embodiments described herein. Based on the embodiments of the present application described in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0028] Figure 1 FIG. 1 is a schematic flow chart of a vehicle rear wheel steering control method 100 according to an embodiment of the present application. Figure 1 As shown, the vehicle rear wheel steering control method 100 according to the embodiment of the present application may include the following steps:

[0029] In step S110, the average wheel turning angle of the vehicle is obtained.

[0030] In step S120, the steering angle difference between the left and right rear wheels is determined based on the average steering angle of the wheels and a preset mapping relationship, wherein the preset mapping relationship is a mapping relationship designed to make the Ackerman rate reach a preset threshold.

[0031] In step S130, the turning angles of the left and right rear wheels are determined based on the average turning angle of the wheels and the turning angle difference between the left and right rear wheels.

[0032] In step S140, the left and right rear wheels of the vehicle are controlled based on the respective turning angles of the left and right rear wheels.

[0033] In an embodiment of the present application, a control method for controlling the left rear wheel and the right rear wheel respectively when the vehicle is turning is provided, wherein a method for calculating the required turning angle of each of the left and right rear wheels is provided. In this method, the average turning angle of the vehicle's wheels is first obtained, and the average turning angle of the wheels includes the average turning angle of the left and right front wheels and the average turning angle of the left and right rear wheels; then, based on the average turning angle of the wheels and a preset mapping relationship, the turning angle difference of the left and right rear wheels of the vehicle is obtained; finally, the turning angle of each of the left and right rear wheels can be obtained by using the obtained average turning angle of the wheels and the turning angle difference of the left and right rear wheels.

[0034] Here, in the preset mapping relationship, the average turning angle of the left and right front wheels is used as the independent variable, or the turning angle of each of the left and right front wheels obtained by the average turning angle of the left and right front wheels is used as the independent variable to obtain the dependent variable, that is, the turning angle difference of the left and right rear wheels. Since the preset mapping relationship is designed to make the Ackerman rate reach a preset threshold value (e.g., 90% to 100%), the turning angle of the left and right rear wheels calculated by the control method and the control of the left and right rear wheels based on the calculation method can improve the Ackerman rate, thereby improving the steering performance and reducing tire wear.

[0035] The concept of Ackerman rate is shown in the following formula (1):

[0036]

[0037] Where Ackerman is the Ackerman rate, θ i is the actual turning angle of the inner front wheel of the vehicle used for turning, θ o is the actual turning angle of the outer front wheel of the vehicle used for turning, θ id is the ideal turning angle of the inner front wheel of the vehicle for turning. That is, when the turning angle of the outer front wheel is taken as a quantity, the Ackerman rate is the ratio of the first difference to the second difference, where the first difference is the actual turning angle θ of the inner front wheel of the vehicle i The actual turning angle θ of the outer front wheel o The second difference is the ideal turning angle θ of the inner front wheel of the vehicle. id The actual turning angle θ of the outer front wheel o The difference between .

[0038] Alternatively, the concept of Ackerman rate can also be expressed as the following formula (2):

[0039]

[0040] Where Ackerman is the Ackerman rate, θ i is the actual turning angle of the inner front wheel of the vehicle used for turning, θ o is the actual turning angle of the outer front wheel of the vehicle used for turning, θ od is the ideal turning angle of the outer front wheel of the vehicle for turning. That is, when the turning angle of the inner front wheel is taken as a quantitative value, the Ackerman rate is: the ratio of the first difference to the third difference, where the first difference is the actual turning angle θ of the inner front wheel of the vehicle i The actual turning angle θ of the outer front wheel o The third difference is the actual turning angle θ of the inner front wheel of the vehicle. i The ideal turning angle θ with the outer front wheel od The difference between .

[0041] Without rear wheel steering, the vehicle diagram of ideal Alman rate steering is as follows Figure 2 As shown in the figure, the turning center of the front axle and the turning center of the rear axle can coincide at one point, and the four wheels of the vehicle can all roll. However, due to the layout of conventional vehicles, the steering trapezoid cannot achieve 100% Ackerman rate, that is, the ideal Ackerman rate. Figure 3 As shown in the figure, the turning center of the front axle of the vehicle is inconsistent with the turning center of the rear axle. Since the turning centers of the front and rear axles of the vehicle are inconsistent, the rubber of the front and rear tires will deform, resulting in a side slip angle, bending the actual movement center of the vehicle to the same movement center, which will cause tire wear. In addition, in winter, the tires become harder and the side slip angle limit decreases sharply. At this time, the side slip angle becomes larger and it is very easy to produce abnormal noise.

[0042] In the embodiment of the present application, since the rear wheel steering can be controlled, and the calculation of the rear wheel steering angle is based on the mapping relationship designed to improve the Ackerman rate, under certain circumstances, the Ackerman rate can reach more than 90%, or even 100%, so that the turning center of the front axle of the vehicle coincides or substantially coincides with the turning center of the rear axle, and the front and rear axle wheels are as pure as possible, and no initial side slip will be generated due to the different movement centers of the front and rear suspension wheel tires. In this case, the tire does not produce initial side slip, the tire eccentric wear is small, and the tire wear is reduced. At the same time, the side slip angle of the tire has an upper limit. Since the movement trajectory of the tire will not produce an initial side slip angle, the limit of the distance side slip angle is large, which can provide more lateral force and improve the lateral limit of the vehicle. At the same time, in winter, the tire becomes hard, and the side slip angle limit decreases sharply. At this time, the side slip angle becomes larger and it is very easy to produce abnormal noise. The rear wheel steering scheme of the present application effectively reduces the tire side slip angle and reduces the probability of abnormal noise of winter tires.

[0043] In one embodiment of the present application, obtaining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship in step S120 may include: obtaining the actual steering angle of the inner front wheel used for turning among the left and right front wheels based on the average steering angle of the left and right front wheels; obtaining the ideal steering angle of the inner front wheel when the Ackerman rate reaches 100% based on the actual steering angle of the inner front wheel; obtaining the steering angle difference between the left and right rear wheels based on the ideal steering angle of the inner front wheel and a first preset mapping relationship, wherein the first preset mapping relationship is a preset mapping relationship between the ideal steering angle of the inner front wheel and the steering angle difference between the left and right rear wheels.

[0044] In this embodiment, the aforementioned formula (1) is used. That is, when the turning angle of the outer front wheel is used as a quantitative value, the Ackerman rate is the ratio of the first difference to the second difference, wherein the first difference is the difference between the actual turning angle of the inner front wheel of the vehicle and the actual turning angle of the outer front wheel, and the second difference is the difference between the ideal turning angle of the inner front wheel of the vehicle and the actual turning angle of the outer front wheel. Based on this, in order to make the Ackerman rate reach a preset threshold, for example, 100%, it is necessary to make the ideal turning angle of the inner front wheel equal to the actual turning angle of the inner front wheel. The actual turning angle of the inner front wheel can be obtained from the steering wheel angle signal. Therefore, it is only necessary to design a mapping relationship (called the first preset mapping relationship) so that there is a mapping relationship between the ideal turning angle of the inner front wheel and the turning angle difference between the left and right rear wheels. The following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the actual turning angle of the inner front wheel is obtained, and then the ideal turning angle of the inner front wheel is obtained (wherein the ideal turning angle of the inner front wheel is equal to the actual turning angle of the inner front wheel), and then the turning angle difference between the left and right rear wheels is obtained through the first preset mapping relationship.

[0045] In a simpler example, since the ideal turning angle of the inner front wheel is equal to the actual turning angle of the inner front wheel when the Ackerman rate reaches 100%, the mapping relationship between the actual turning angle of the inner front wheel and the turning angle difference between the left and right rear wheels can also be directly designed (called the third preset mapping relationship), and the following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the actual turning angle of the inner front wheel is obtained, and then the turning angle difference between the left and right rear wheels is obtained through the third preset mapping relationship.

[0046] In a simpler example, when the Ackerman rate reaches 100%, the ideal turning angle of the inner front wheel is equal to the actual turning angle of the inner front wheel, and the actual turning angle of the inner front wheel can be obtained from the average turning angle of the left and right front wheels. Therefore, the mapping relationship between the average turning angle of the left and right front wheels and the turning angle difference of the left and right rear wheels can be directly designed (called the fourth preset mapping relationship), and the following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the turning angle difference of the left and right rear wheels is obtained through the fourth preset mapping relationship.

[0047] In another embodiment of the present application, in step S120, the steering angle difference between the left and right rear wheels is obtained based on the average steering angle of the wheels and a preset mapping relationship, including: obtaining the actual steering angle of the outer front wheel used for turning among the left and right front wheels based on the average steering angle of the left and right front wheels; obtaining the ideal steering angle of the outer front wheel when the Ackerman rate reaches 100% based on the actual steering angle of the outer front wheel; obtaining the steering angle difference between the left and right rear wheels based on the ideal steering angle of the outer front wheel and a second preset mapping relationship, wherein the second preset mapping relationship is a preset mapping relationship between the ideal steering angle of the outer front wheel and the steering angle difference between the left and right rear wheels.

[0048] In this embodiment, the aforementioned formula (2) is used. That is, when the turning angle of the inner front wheel is used as a quantitative value, the Ackerman rate is the ratio of the first difference to the third difference, wherein the first difference is the difference between the actual turning angle of the inner front wheel of the vehicle and the actual turning angle of the outer front wheel, and the third difference is the difference between the actual turning angle of the inner front wheel of the vehicle and the ideal turning angle of the outer front wheel. Based on this, in order to make the Ackerman rate reach a preset threshold, for example, 100%, it is necessary to make the ideal turning angle of the outer front wheel equal to the actual turning angle of the outer front wheel. The actual turning angle of the outer front wheel can be obtained from the steering wheel angle signal, so it is only necessary to design a mapping relationship (called the second preset mapping relationship) so that the ideal turning angle of the outer front wheel and the turning angle difference of the left and right rear wheels exist in a mapping relationship, and the following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the actual turning angle of the outer front wheel is obtained, and then the ideal turning angle of the outer front wheel is obtained (where the ideal turning angle of the outer front wheel is equal to the actual turning angle of the outer front wheel), and then the turning angle difference of the left and right rear wheels is obtained through the second preset mapping relationship.

[0049] In a simpler example, since the ideal turning angle of the outer front wheel is equal to the actual turning angle of the outer front wheel when the Ackerman rate reaches 100%, the mapping relationship between the actual turning angle of the outer front wheel and the turning angle difference of the left and right rear wheels (called the fifth preset mapping relationship) can also be directly designed, and the following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the actual turning angle of the outer front wheel is obtained, and then the turning angle difference of the left and right rear wheels is obtained through the fifth preset mapping relationship.

[0050] In a simpler example, when the Ackerman rate reaches 100%, the ideal turning angle of the outer front wheel is equal to the actual turning angle of the outer front wheel, and the actual turning angle of the outer front wheel can be obtained from the average turning angle of the left and right front wheels. Therefore, the mapping relationship between the average turning angle of the left and right front wheels and the turning angle difference of the left and right rear wheels can be directly designed (called the fourth preset mapping relationship, the same as described above), and the following can be obtained: the average turning angle of the left and right front wheels is obtained from the steering wheel angle signal, and then the turning angle difference of the left and right rear wheels is obtained through the fourth preset mapping relationship.

[0051] In an embodiment of the present application, obtaining the average turning angle of the left and right rear wheels of the vehicle based on the average turning angle of the left and right front wheels can include: obtaining the vehicle speed; obtaining the proportional coefficient between the average turning angle of the left and right rear wheels and the average turning angle of the left and right front wheels based on a preset function, wherein the independent variable of the preset function is the vehicle speed, and the dependent variable of the preset function is the proportional coefficient; multiplying the average turning angle of the left and right front wheels by the proportional coefficient to obtain the average turning angle of the left and right rear wheels.

[0052] For example, assuming that the vehicle speed is represented by v, the preset function is represented by f, and the average turning angle of the left and right front wheels is represented by θ f , the average turning angle of the left and right rear wheels is expressed as θ r , the proportionality coefficient is k, which can be expressed as the following formulas (3) and (4):

[0053] θ r = k × θ f (3)

[0054] k=f(v) (4)

[0055] Among them, the average turning angle θ of the left and right front wheels f The steering wheel angle signal can be obtained from the steering wheel angle sensor. The vehicle speed can be obtained from the vehicle speed sensor.

[0056] In the embodiment of the present application, when the vehicle speed is less than the preset speed, the proportional coefficient is a negative number, and the turning direction of the left and right rear wheels is opposite to the turning direction of the left and right front wheels; when the vehicle speed is not less than the preset speed, the proportional coefficient is a positive number, and the turning direction of the left and right rear wheels is the same as the turning direction of the left and right front wheels. Continuing with the example described above, in formula (4), f can be a piecewise function: when the vehicle speed is less than a certain value, k is a negative number, so that the average turning angle θ of the left and right front wheels is f The average turning angle θ between the left and right rear wheels r One is a positive value and the other is a negative value, so that the turning direction of the left and right rear wheels is opposite to the turning direction of the left and right front wheels; when the vehicle speed is not less than this value, k is a positive number, so that the average turning angle θ of the left and right front wheels is f The average turning angle θ between the left and right rear wheels r All are positive or all are negative, so that the turning direction of the left and right rear wheels is the same as the turning direction of the left and right front wheels. The advantages of this design are:

[0057] When the vehicle speed is lower than the vehicle speed threshold, the rear wheel turning angle is opposite to the front wheel turning angle, which has the effect of reducing the turning diameter. In this application, when the rear wheels are turned, the inner rear wheel turning angle is greater than the outer rear wheel turning angle. Taking left turn as an example, at this time, the turning angle of the left rear wheel is greater than the turning angle of the right rear wheel, and the relationship between the front and rear wheel turning angles can make the turning center of the front wheel coincide with the turning center of the rear wheel, such as Figure 4 As shown, the Ackerman rate of the vehicle reaches 100% at this time, and the front and rear axle wheels are in pure rolling, and no initial side slip will occur due to the different movement centers of the front and rear suspension wheel tires. In this case, the tire does not produce initial side slip, the tire wear is small, and the tire wear is reduced. At the same time, the side slip angle of the tire has an upper limit. Since the movement trajectory of the tire will not produce an initial side slip angle, the distance side slip angle limit is large, which can provide more lateral force and improve the lateral limit of the vehicle. At the same time, in winter, the tire becomes hard, and the side slip angle limit decreases sharply. At this time, the side slip angle becomes larger and it is very easy to produce abnormal noise. The rear-wheel steering scheme of the present application effectively reduces the tire side slip angle and reduces the probability of abnormal noise of winter tires.

[0058] When the vehicle has a certain speed, the tire will generate an initial side slip angle due to the lateral force. At this time, when the turning angle of the inner rear wheel is greater than that of the outer rear wheel by a certain angle, the turning centers of the two wheels on the front axle and the two wheels on the rear axle can basically coincide. Figure 5 As shown, the Ackerman rate is effectively improved. At this time, the lateral rubber deformation of the front and rear tires is less than that of the models without rear-wheel steering or other existing rear-wheel steering models. In this case, the lateral wear of the tire will be reduced. Similarly, in winter when the temperature is lower, the tire carcass becomes hard, and it is easy to produce abnormal creaking noise when lateral deformation occurs. The rear-wheel steering control method of the present application can effectively reduce the tire side slip angle and reduce the probability of the tire producing abnormal creaking noise.

[0059] In general, when the vehicle speed is below the threshold, the rear wheel turns in the opposite direction to the front wheel, which reduces the turning diameter. At the same time, the inner rear wheel turns greater than the outer rear wheel, achieving a higher Ackerman rate and reducing tire wear. When the vehicle speed is above the threshold, the rear wheel turns in the same direction as the front wheel, which enhances the stability of the rear axle. At the same time, the inner rear wheel turns greater than the outer rear wheel, achieving a higher Ackerman rate and reducing tire wear.

[0060] In an embodiment of the present application, step S130 determines the respective turning angles of the left and right rear wheels based on the average turning angle of the wheels and the turning angle difference between the left and right wheels, which may include: multiplying the turning angle difference between the left and right rear wheels by a preset coefficient to obtain a turning angle offset, wherein the preset coefficient is greater than 0 and less than 1; adding the turning angle offset to the average turning angle of the left and right rear wheels to obtain the turning angle of the inner rear wheel; and subtracting the turning angle offset from the average turning angle of the left and right rear wheels to obtain the turning angle of the outer rear wheel.

[0061] For example, the steering angle difference between the left and right rear wheels is obtained based on the average steering angle of the left and right front wheels and the preset mapping relationship, which is expressed by formula (5):

[0062] Δθ r =f(θ f ) (5)

[0063] Among them, Δθ r is the steering angle difference between the left and right rear wheels, θ f is the average turning angle of the left and right front wheels, f is the preset mapping relationship, and the turning angle of the inner rear wheel used for turning is θ ri , the turning angle of the outer rear wheel is denoted as θ ro , the average turning angle of the left and right rear wheels is θ r , then the turning angles of the inner and outer rear wheels are expressed by formula (6) and formula (7) respectively:

[0064] θ ri =θ r +0.5Δθ r (6)

[0065] θ ro =θ r -0.5Δθ r (7)

[0066] In this example, the steering angle difference Δθ between the left and right rear wheels is r Multiply by the preset coefficient 0.5 to get the angle offset 0.5Δθ r , the average turning angle θ of the left and right rear wheels r Add angular offset 0.5Δθ r , and the turning angle θ of the inner rear wheel is obtained ri ; The average turning angle θ of the left and right rear wheels r Minus angular offset 0.5Δθr , and the turning angle θ of the outer rear wheel is obtained ro .

[0067] The above exemplary shows the vehicle rear wheel steering control method 100 according to the embodiment of the present application. Based on the above description, the vehicle rear wheel steering control method 100 according to the embodiment of the present application adjusts the rear wheel steering angle through a reasonable control strategy, which can achieve better steering performance than other rear wheel steering methods, improve the steering limit grip ability and reduce tire wear, and reduce the probability of abnormal noise at low temperature of the tire.

[0068] Combine the following Figure 6 A vehicle rear wheel steering control device is described according to another aspect of the present application. Figure 6 FIG. 6 shows a schematic structural block diagram of a vehicle rear wheel steering control device 600 according to an embodiment of the present application. Figure 6 As shown, the vehicle rear wheel steering control device 600 includes a memory 610 and a processor 620, wherein the memory 610 stores a computer executable program executed by the processor, and when the computer executable program is executed by the processor 620, the processor 620 executes the above-mentioned vehicle rear wheel steering control method 100. The vehicle rear wheel steering control method 100 has been described in detail above, and those skilled in the art can understand the operation of the processor 620 in combination with the above, and for the sake of brevity, it will not be repeated here.

[0069] Combine the following Figure 7 A vehicle rear wheel steering control system is described according to another aspect of the present application. Figure 7 FIG. 2 shows a schematic structural block diagram of a vehicle rear wheel steering control system 700 according to an embodiment of the present application. Figure 7As shown, the vehicle rear wheel steering control system 700 includes a sensor 710, a left rear wheel steering gear 720, a right rear wheel steering gear 730 and a vehicle rear wheel steering control device 740. Among them: the vehicle rear wheel steering control device 740 can be the vehicle rear wheel steering control device 600 described above, which executes the vehicle rear wheel steering control method 100 described above. Specifically, the vehicle rear wheel steering control device 740 can obtain the average wheel angle of the vehicle from the sensor 710 (such as a steering wheel angle sensor), determine the respective angles of the left and right rear wheels based on the average wheel angle, generate a left rear wheel angle signal and a right rear wheel angle signal, and send the left rear wheel angle signal and the right rear wheel angle signal to the left rear wheel steering gear 720 and the right rear wheel steering gear 730 respectively. In this process, the vehicle speed of the vehicle speed sensor can also be used, as described above. The left rear wheel steering gear 720 is used to control the left rear wheel based on the left rear wheel angle signal. The right rear wheel steering gear 730 is used to control the right rear wheel based on the right rear wheel angle signal. The vehicle rear-wheel steering control method 100 executed by the vehicle rear-wheel steering control device 600 has been described in detail in the foregoing text. Those skilled in the art can understand the operation of the vehicle rear-wheel steering control device 740 in combination with the foregoing description. For the sake of brevity, it will not be repeated here.

[0070] The operation flow chart of the vehicle rear wheel steering control system 700 can be as follows: Figure 8 As shown (where Figure 8 The electronic control center in the vehicle can be equivalent to the vehicle rear wheel steering control device 740). When the vehicle speed is lower than the threshold, the direction of the rear wheel steering angle is opposite to that of the front wheel, which plays a role in reducing the turning diameter. At the same time, the inner rear wheel steering angle is greater than the outer rear wheel steering angle, achieving a higher Ackerman rate and reducing tire wear. When the vehicle speed is higher than the threshold, the rear wheel steering angle is in the same direction as the front wheel, which plays a role in enhancing the stability of the rear axle. At the same time, the inner rear wheel steering angle is greater than the outer rear wheel steering angle, achieving a higher Ackerman rate and reducing tire wear.

[0071] According to another aspect of the present application, a vehicle is further provided, the vehicle comprising the above-mentioned vehicle rear-wheel steering control device 600 or the above-mentioned vehicle rear-wheel steering control system 700.

[0072] According to another aspect of the present application, a storage medium is provided, on which a computer program executed by a processor is stored. When the computer program is executed by the processor, the processor executes the above-mentioned vehicle rear wheel steering control method 100.

[0073] According to another aspect of the present application, a computer program is provided. When the computer program is executed by a processor, the processor executes the above-mentioned vehicle rear wheel steering control method 100.

[0074] Based on the above description, the vehicle rear-wheel steering control method, device, system and vehicle according to the embodiments of the present application can adjust the rear wheel angle through a reasonable control strategy, which can achieve better steering performance than other rear-wheel steering methods, improve the steering's ultimate grip ability, reduce tire wear, and reduce the probability of abnormal noise caused by low tire temperatures.

[0075] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present application to this. Those of ordinary skill in the art may make various changes and modifications therein without departing from the scope and spirit of the present application. All these changes and modifications are intended to be included within the scope of the present application as required by the appended claims.

[0076] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein 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.

[0077] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0078] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0079] Similarly, it should be understood that in order to streamline the present application and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present application should not be interpreted as reflecting the following intention: the claimed application requires more features than the features clearly stated in each claim. More specifically, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with features less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby explicitly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present application.

[0080] It will be understood by those skilled in the art that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this specification may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0081] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0082] The various component embodiments of the present application can be implemented in hardware, or implemented in software modules running on one or more processors, or implemented in a combination thereof. It should be understood by those skilled in the art that a microprocessor or digital signal processor (DSP) can be used in practice to implement some or all functions of some modules according to the embodiments of the present application. The application can also be implemented as a part or all of a program (e.g., a computer program and a computer program product) for performing the method described herein. Such a program implementing the present application can be stored on a computer-readable medium, or can have the form of one or more signals. Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0083] It should be noted that the above embodiments illustrate the present application rather than limit the present application, and that those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be constructed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of multiple such elements. The present application may be implemented with the aid of hardware comprising several different elements and with the aid of a suitably programmed computer. In a unit claim listing several vehicle refrigerator control devices, several of these vehicle refrigerator control devices may be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words may be interpreted as names.

[0084] The above is only a specific implementation or description of a specific implementation of the present application, and the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A vehicle rear wheel steering control method, characterized in that: The method comprises: Get the average wheel turning angle of the vehicle; Determining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship, wherein the preset mapping relationship is a mapping relationship designed to make the Ackerman rate reach a preset threshold value; Determining the respective turning angles of the left and right rear wheels based on the average turning angle of the wheels and the turning angle difference between the left and right rear wheels; The left and right rear wheels of the vehicle are controlled based on the respective turning angles of the left and right rear wheels.

2. The method according to claim 1, characterized in that The step of obtaining the average wheel turning angle of the vehicle comprises: Acquire a steering wheel angle signal, and acquire an average steering angle of the left and right front wheels based on the steering wheel angle signal; The average turning angle of the left and right rear wheels is obtained based on the average turning angle of the left and right front wheels.

3. The method according to claim 2, characterized in that The determining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship comprises: Acquire an actual turning angle of an inner front wheel for turning among the left and right front wheels based on an average turning angle of the left and right front wheels; Obtaining an ideal turning angle of the inner front wheel when the Ackerman rate reaches 100% based on the actual turning angle of the inner front wheel; The turning angle difference between the left and right rear wheels is obtained based on the ideal turning angle of the inner front wheel and a first preset mapping relationship, wherein the first preset mapping relationship is a preset mapping relationship between the ideal turning angle of the inner front wheel and the turning angle difference between the left and right rear wheels.

4. The method according to claim 2, characterized in that: The determining the steering angle difference between the left and right rear wheels based on the average steering angle of the wheels and a preset mapping relationship comprises: Acquire an actual turning angle of an outer front wheel used for turning among the left and right front wheels based on the average turning angle of the left and right front wheels; Obtaining an ideal turning angle of the outer front wheel when the Ackerman rate reaches 100% based on the actual turning angle of the outer front wheel; The turning angle difference between the left and right rear wheels is obtained based on the ideal turning angle of the outer front wheel and a second preset mapping relationship, wherein the second preset mapping relationship is a preset mapping relationship between the ideal turning angle of the outer front wheel and the turning angle difference between the left and right rear wheels.

5. The method according to claim 2, characterized in that: The obtaining the average turning angle of the left and right rear wheels based on the average turning angle of the left and right front wheels comprises: Obtaining the speed of the vehicle; Obtaining a proportionality coefficient between the average turning angle of the left and right rear wheels and the average turning angle of the left and right front wheels based on a preset function, wherein the independent variable of the preset function is the vehicle speed and the dependent variable of the preset function is the proportionality coefficient; The average turning angle of the left and right front wheels is multiplied by the proportional coefficient to obtain the average turning angle of the left and right rear wheels.

6. The method according to claim 5, characterized in that When the vehicle speed is less than a preset vehicle speed, the proportional coefficient is a negative number, and the turning direction of the left and right rear wheels is opposite to the turning direction of the left and right front wheels; When the vehicle speed is not less than the preset vehicle speed, the proportional coefficient is a positive number, and the turning angle direction of the left and right rear wheels is in the same direction as the turning angle direction of the left and right front wheels.

7. The method according to claim 2, characterized in that The determining the respective turning angles of the left and right rear wheels based on the average turning angle of the wheels and the turning angle difference of the left and right rear wheels comprises: The turning angle difference between the left and right rear wheels is multiplied by a preset coefficient to obtain a turning angle offset, wherein the preset coefficient is greater than 0 and less than 1; The average turning angle of the left and right rear wheels is added to the turning angle offset to obtain the turning angle of the inner rear wheel; The turning angle of the outer rear wheel is obtained by subtracting the turning angle offset from the average turning angle of the left and right rear wheels.

8. A vehicle rear wheel steering control device, characterized in that: The control device includes a memory and a processor, wherein the memory stores a computer executable program run by the processor, and when the computer executable program is run by the processor, the processor executes the vehicle rear wheel steering control method as described in any one of claims 1-7.

9. A vehicle rear wheel steering control system, characterized in that: The control system comprises a sensor, a left rear wheel steering gear, a right rear wheel steering gear and the vehicle rear wheel steering control device according to claim 8, wherein: The vehicle rear wheel steering control device is used to obtain the average wheel steering angle of the vehicle from the sensor, determine the steering angles of the left and right rear wheels based on the average wheel steering angle, generate a left rear wheel steering angle signal and a right rear wheel steering angle signal, and send the left rear wheel steering angle signal and the right rear wheel steering angle signal to the left rear wheel steering gear and the right rear wheel steering gear respectively; The left rear wheel steering gear is used to control the left rear wheel based on the left rear wheel steering angle signal; The right rear wheel steering gear is used to control the right rear wheel based on the right rear wheel steering angle signal.

10. A vehicle, characterized in that: The vehicle includes the vehicle rear-wheel steering control device according to claim 8 or the vehicle rear-wheel steering control system according to claim 9.

11. A storage medium, characterized in that: The storage medium stores a computer program executed by a processor, and when the computer program is executed by the processor, the processor executes the vehicle rear wheel steering control method according to any one of claims 1 to 7.

12. A computer program, characterized in that When the computer program is executed by a processor, the processor is caused to execute the vehicle rear wheel steering control method according to any one of claims 1 to 7.

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