Wheel steering control method and device, vehicle and storage medium

Abstract

The invention relates to the technical field of vehicles, in particular to a wheel steering control method and device, a vehicle and a storage medium. The method comprises the steps that in the vehicle steering process, the target yaw velocity of a vehicle is determined based on state parameters of the vehicle; based on the target yaw velocity and the actual yaw velocity of the vehicle, calculating a steering compensation angle required by steering of rear wheels of the vehicle; determining a target steering angle of the vehicle according to the steering compensation angle and the speed-following ratio steering angle of the rear wheels of the vehicle; and controlling rear wheels of the vehicle to steer based on the target steering angle. The steering compensation angle is calculated based on the state parameters of the vehicle and the actual yaw velocity of the vehicle so as to compensate the steering angle of the rear wheels of the vehicle along with the speed ratio, and the technical effect of improving the stability of the vehicle can be achieved.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, specifically to a wheel steering control method, device, vehicle, and storage medium. Background Technology

[0002] Active Rear Wheel Steering (RWS) is a core chassis technology that improves a vehicle's low-speed agility and high-speed stability. Traditional speed-sensitive proportional control active rear wheel steering mainly relies on vehicle speed and steering wheel angle to output the rear wheel steering angle, without considering the actual driving conditions of the vehicle, thus affecting the vehicle's stability. Summary of the Invention

[0003] In view of the above, it is necessary to propose a wheel steering control method, device, vehicle and storage medium to solve the technical problem of low vehicle stability when driving on high-friction and low-friction surfaces in the prior art.

[0004] In a first aspect, this application provides a wheel steering control method, the method comprising: during vehicle steering, determining a target yaw rate of the vehicle based on the vehicle's state parameters; calculating a steering compensation angle required for the rear wheels of the vehicle to steer based on the target yaw rate and the vehicle's actual yaw rate; determining a target steering angle of the vehicle based on the steering compensation angle and the speed-ratio steering angle of the rear wheels of the vehicle; and controlling the rear wheels of the vehicle to steer based on the target steering angle.

[0005] Optionally, in the aforementioned wheel steering control method, the state parameters include steering parameters, acceleration parameters, wheel-end moment parameters, road surface adhesion coefficient, the sideslip angle of the center of gravity at the previous moment based on the current moment, and the yaw rate at the previous moment. Determining the target yaw rate of the vehicle based on the vehicle's state parameters includes: using a pre-built vehicle load transfer model, determining the vehicle's dynamic vertical tire load based on the acceleration parameters; obtaining the vehicle's front and rear axle slip ratios based on the steering parameters, the sideslip angle of the center of gravity at the previous moment, and the yaw rate at the previous moment; calculating the vehicle's external yaw moment based on the dynamic vertical tire load, the wheel-end moment parameters, and the road surface adhesion coefficient; using a pre-built tire model, determining the vehicle's front and rear axle lateral forces based on the front and rear axle slip ratios and the road surface adhesion coefficient; using a pre-built vehicle reference model, determining the yaw rate at the current moment based on the front and rear axle lateral forces and the external yaw moment; and using the yaw rate at the current moment as the target yaw rate.

[0006] Optionally, in the above-described wheel steering control method, determining the front and rear axle lateral forces of the vehicle based on the front and rear axle slip ratios and the road surface adhesion coefficient using a pre-built tire model includes: obtaining preset adhesion coefficient adjustment factors and adhesion coefficient correction factors; and determining the front and rear axle lateral forces using the tire model based on the adhesion coefficient adjustment factors, the adhesion coefficient correction factors, the front and rear axle slip ratios, and the road surface adhesion coefficient.

[0007] Optionally, in the above-described wheel steering control method, the acceleration parameters include the vehicle's longitudinal acceleration and lateral acceleration. The step of determining the vehicle's dynamic vertical tire load based on the acceleration parameters using a pre-built vehicle load transfer model includes: using the vehicle load transfer model to obtain the vehicle's longitudinal load offset, lateral load offset, and static vertical tire load; and determining the dynamic vertical tire load based on the longitudinal acceleration, lateral acceleration, longitudinal load offset, lateral load offset, and static vertical tire load.

[0008] Optionally, in the above-described wheel steering control method, the steering parameters include tire angle, longitudinal vehicle speed, and tire speed. The step of obtaining the front and rear axle slip ratios of the vehicle based on the steering parameters, the previous moment's center of gravity sideslip angle, and the previous moment's yaw rate includes: obtaining the vehicle's tire radius and vehicle center of gravity position; and calculating the front and rear axle slip ratios based on the tire radius, vehicle center of gravity position, tire angle, longitudinal vehicle speed, tire speed, the previous moment's center of gravity sideslip angle, and the previous moment's yaw rate.

[0009] Optionally, in the above-described wheel steering control method, the wheel-end torque parameters include wheel-end driving torque and wheel-end braking torque. The step of calculating the vehicle's external yaw moment based on the tire dynamic vertical load, the wheel-end torque parameters, and the road surface adhesion coefficient includes: obtaining the vehicle's tire radius and track width; calculating the tire longitudinal force based on the wheel-end driving torque, the wheel-end braking torque, the tire dynamic vertical load, the tire radius, and the road surface adhesion coefficient; and determining the external yaw moment based on the tire longitudinal force and the track width.

[0010] Optionally, in the above-described wheel steering control method, the step of calculating the steering compensation angle required for the rear wheel steering of the vehicle based on the target yaw rate and the actual yaw rate of the vehicle includes: calculating the yaw rate difference based on the target yaw rate and the actual yaw rate of the vehicle; if the yaw rate difference exceeds a preset yaw rate range, determining the steering compensation angle required for the rear wheel steering of the vehicle based on the yaw rate difference.

[0011] In a second aspect, an electronic device is provided, the electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the wheel steering control method as described in any of the preceding claims.

[0012] Thirdly, a vehicle is provided, the vehicle including the electronic equipment described above.

[0013] Fourthly, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when executed by a processor, the computer program implements the wheel steering control method as described in any one of the preceding claims.

[0014] Based on the above, this application provides a wheel steering control method, device, vehicle, and storage medium. The method includes: during vehicle steering, determining a target yaw rate of the vehicle based on the vehicle's state parameters; calculating the steering compensation angle required for rear wheel steering based on the target yaw rate and the vehicle's actual yaw rate; determining a target steering angle of the vehicle based on the steering compensation angle and the speed-ratio steering angle of the rear wheels; and controlling the rear wheels to steer based on the target steering angle. This application calculates the steering compensation angle based on the vehicle's state parameters and actual yaw rate to compensate for the speed-ratio steering angle of the rear wheels, thereby improving vehicle stability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating an application scenario of the wheel steering control method provided in an embodiment of this application.

[0016] Figure 2 This is a flowchart of a wheel steering control method provided in an embodiment of this application.

[0017] Figure 3 This is a schematic diagram of a wheel steering control device provided in an embodiment of this application.

[0018] Figure 4 This is a schematic diagram of an electronic device provided in an embodiment of this application.

[0019] Component Symbol Explanation Vehicle 1 Electronic devices 10 Memory 11 Processor 12 Wheel steering control device 100 First Determination Module 110 Angle Calculation Module 120 Second determination module 130 Steering control module 140 The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0021] In the embodiments of this application, it should be noted that, unless otherwise expressly specified and limited, the word "for example" is used to indicate an example, illustration, or description. Any embodiment or design scheme described as "for example" in the embodiments of this application should not be construed as being better or more advantageous than other embodiments or design schemes. Specifically, the use of the word "for example" is intended to present the relevant concepts in a specific manner.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. Furthermore, in the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited.

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0025] Please see Figure 1 This is a schematic diagram illustrating an application scenario of the wheel steering control method provided in an embodiment of this application. Figure 1As shown, when a vehicle enters a curve, if the vehicle's Active Rear Wheel Steering (RWS) controls the rear wheels to steer according to the speed ratio method without considering the actual driving conditions of the vehicle, understeer or oversteer may occur, which can easily lead to traffic accidents.

[0026] To address the aforementioned issues, some embodiments of this application provide a wheel steering control method that, when a vehicle is steering, can effectively control the rear wheels of the vehicle by combining the vehicle's state and rotational speed, thereby improving vehicle stability.

[0027] Please see Figure 2 The diagram shows a flowchart of a wheel steering control method according to an embodiment of this application. Specifically, the wheel steering control method includes the following steps. Depending on different requirements, the order of some steps in the flowchart can be changed, and some steps can be omitted.

[0028] S201: During vehicle steering, determine the target yaw rate of the vehicle based on the vehicle's state parameters.

[0029] In some embodiments of this application, the vehicle's state parameters can be state parameters collected by sensors during vehicle steering. For example, vehicle state parameters may include parameters such as longitudinal acceleration, lateral acceleration, estimated road slope, front and rear tire steering angles, tire speed, longitudinal vehicle speed, and yaw rate. During vehicle steering, the vehicle's state parameters continuously change. Each time the sensors collect a set of vehicle state parameters, they are sent to the processor, which determines the corresponding target yaw rate based on the vehicle's state parameters. The target yaw rate can be calculated or predicted based on the currently collected state parameters from the sensors; different sensor-collected state parameters result in different target yaw rates.

[0030] In some embodiments of this application, when it is determined that a vehicle is entering or about to enter a curved road segment, the vehicle's state parameters can be acquired, and the target yaw rate of the vehicle can be determined based on the vehicle's state parameters. For example, the vehicle's vision system (such as a front camera) can acquire a road image in front of the vehicle, and then the road image can be used to determine whether the vehicle is entering or about to enter a curve. After acquiring the road image in front of the vehicle through the vehicle's vision system, the road boundary lines (such as lane lines, shoulders, guardrails) and the road centerline are extracted from the road image using an image processing algorithm (such as an edge detection algorithm). Then, based on the curvature of the road boundary lines and / or the road centerline, the curvature of the road ahead is determined. If the curvature of the road ahead is greater than or equal to a preset curvature threshold, it is determined that the vehicle is entering or about to enter a curve, triggering the acquisition of the vehicle's state parameters.

[0031] In another example, the current steering angle of the steering wheel can be obtained through a steering wheel angle sensor (SWAS). If the current steering angle is greater than or equal to a preset steering threshold, it is determined that the vehicle has entered a curve, triggering the acquisition of the vehicle's state parameters.

[0032] In some embodiments of this application, the state parameters may include steering parameters, acceleration parameters, wheel-end moment parameters, road adhesion coefficient, the sideslip angle of the center of gravity at the previous moment based on the current moment, and the yaw rate at the previous moment. Determining the target yaw rate of the vehicle based on the vehicle's state parameters includes: using a pre-built vehicle load transfer model, determining the vehicle's dynamic vertical tire load based on the acceleration parameters; obtaining the vehicle's front and rear axle slip ratios based on the steering parameters, the sideslip angle of the center of gravity at the previous moment, and the yaw rate at the previous moment; calculating the vehicle's external yaw moment based on the tire dynamic vertical load, wheel-end moment parameters, and road adhesion coefficient; using a pre-built tire model, determining the vehicle's front and rear axle lateral forces based on the front and rear axle slip ratios and road adhesion coefficient; using a pre-built vehicle reference model, determining the yaw rate at the current moment based on the front and rear axle lateral forces and the external yaw moment; and using the yaw rate at the current moment as the target yaw rate.

[0033] In some embodiments of this application, acceleration parameters may include the vehicle's lateral acceleration and longitudinal angular velocity. The vehicle's lateral acceleration and longitudinal angular velocity can be acquired by an inertial measurement unit (IMU) during vehicle steering. The vehicle load transfer model can be a mechanical model describing the redistribution of vehicle weight among different wheels under dynamic conditions such as acceleration, braking, and steering.

[0034] In some embodiments of this application, the dynamic vertical load of a vehicle's tires is determined using a pre-built vehicle load transfer model based on acceleration parameters. This may include: using the vehicle load transfer model to obtain the vehicle's longitudinal load offset, lateral load offset, and static vertical load of the tires; and determining the dynamic vertical load of the tires based on the longitudinal acceleration, lateral acceleration, longitudinal load offset, lateral load offset, and static vertical load of the tires.

[0035] In some embodiments of this application, the longitudinal load offset, lateral load offset, and static vertical load of the tires are obtained using a vehicle load transfer model. This requires first obtaining the vehicle's fixed parameters, and then using the vehicle load transfer model to obtain these parameters. In this embodiment, the vehicle's fixed parameters may include the sprung mass, unsprung mass of a single wheel, distance from the vehicle's center of gravity to the front axle, distance from the vehicle's center of gravity to the rear axle, wheelbase between the front and rear axles, track width between the left and right wheels, and the vehicle's center of gravity height. These parameters are the vehicle's fixed parameters and can be obtained from the vehicle's design images or through actual vehicle testing and calibration. The vehicle's fixed parameters are input into the vehicle load transfer model to obtain the longitudinal load offset and lateral load offset. Then, based on the longitudinal acceleration, lateral acceleration, longitudinal load offset, lateral load offset, and static vertical load of the tires, the dynamic vertical load of the tires is determined.

[0036] In one example, the longitudinal load offset and the lateral load offset can be calculated using the vehicle load transfer model using the following formula: In the above formula, Indicates the sprung mass. Indicates the unsprung mass of a single wheel. Indicates the height of the center of mass. Indicates wheelbase. Indicates wheelbase. This indicates the distance from the vehicle's center of gravity to the front axle. This indicates the distance from the vehicle's center of gravity to the rear axle. This indicates the longitudinal load offset. This indicates the lateral load offset.

[0037] In some embodiments of this application, during the determination of the dynamic vertical load of the tire based on longitudinal acceleration, lateral acceleration, longitudinal load offset, lateral load offset, and tire static vertical load, longitudinal acceleration is used to drive the longitudinal load transfer, and lateral acceleration is also used to drive the longitudinal load transfer. If the longitudinal acceleration is greater than 0, the load is shifted rearward, and the rear wheel vertical force is increased by a longitudinal load offset based on the tire static vertical load, while the front wheel vertical force is decreased by a longitudinal load offset based on the tire static vertical load. If the longitudinal acceleration is less than 0, the load is shifted forward, and the front wheel vertical force is increased by a longitudinal load offset based on the tire static vertical load, while the rear wheel vertical force is decreased by a longitudinal load offset based on the tire static vertical load. If the lateral acceleration is greater than 0, the load shifts to the right, and the vertical force on the right wheel increases by a longitudinal load offset based on the static vertical load of the tire. At the same time, the vertical force on the left wheel decreases by a longitudinal load offset based on the static vertical load of the tire. If the lateral acceleration is less than 0, the load shifts to the left, and the vertical force on the left wheel increases by a longitudinal load offset based on the static vertical load of the tire. At the same time, the vertical force on the right wheel decreases by a longitudinal load offset based on the static vertical load of the tire.

[0038] In some embodiments of this application, the static vertical load of the tires includes the static vertical load of each wheel of the vehicle. For example, the static vertical load of the tires may include the static vertical load of the right front wheel, the static vertical load of the left front wheel, the static vertical load of the right rear wheel, and the static vertical load of the left rear wheel. The corresponding dynamic vertical load of the tires may include the dynamic vertical load of the right front wheel, the dynamic vertical load of the left front wheel, the dynamic vertical load of the right rear wheel, and the dynamic vertical load of the left rear wheel.

[0039] In one example, if the longitudinal acceleration is greater than 0 and the lateral acceleration is greater than 0, the vehicle accelerates and turns to the left. At this time, the dynamic vertical loads of each wheel of the vehicle can be calculated using the vehicle load transfer model through the following formula: In the above formula, This indicates the longitudinal load offset. Indicates the lateral load offset. This indicates the static vertical load on the left front wheel. This indicates the static vertical load on the right front wheel. This indicates the static vertical load on the left rear wheel. This indicates the static vertical load on the right rear wheel. This indicates the dynamic vertical load on the left front wheel. This indicates the dynamic vertical load on the right front wheel. This indicates the dynamic vertical load on the left rear wheel. This indicates the dynamic vertical load on the right rear wheel.

[0040] In some embodiments of this application, the steering parameters include tire angle, longitudinal vehicle speed, and tire speed. Based on the steering parameters, the sideslip angle of the center of gravity at the previous moment, and the yaw rate of the previous moment, the front and rear axle slip ratios of the vehicle are obtained, including: obtaining the tire radius and the position of the vehicle's center of gravity; and calculating the front and rear axle slip ratios based on the tire radius, the position of the vehicle's center of gravity, the tire angle, the longitudinal vehicle speed, the tire speed, the sideslip angle of the center of gravity at the previous moment, and the yaw rate of the previous moment.

[0041] In some embodiments of this application, the front and rear axle slip ratios may include the front axle longitudinal slip ratio, the front axle lateral slip ratio, the rear axle longitudinal slip ratio, and the rear axle lateral slip ratio. The vehicle's center of gravity position typically includes three parameters: the distance from the center of gravity to the front axle, the distance from the center of gravity to the rear axle, and the center of gravity height. Tire speeds may include the tire speeds of the left front tire, the right front tire, the left rear tire, and the rear tire. Tire speeds can be acquired by wheel speed sensors mounted on the four tires.

[0042] In one example, the front axle longitudinal slip ratio, front axle lateral slip ratio, rear axle longitudinal slip ratio, and rear axle lateral slip ratio can be calculated using the following formula: In the above formula, Indicates the tire swerve angle or the front axle swerve angle. Indicates the tire swerve angle or the swerve angle of the rear axle. Indicates longitudinal vehicle speed. This represents the sideslip angle of the center of mass at the previous moment. This represents the yaw rate at the previous moment. This indicates the distance from the vehicle's center of gravity to the front axle. This indicates the tire speed of the left front tire. This indicates the tire speed of the right front tire. This indicates the tire speed of the left rear tire. This indicates the tire speed of the right rear tire. Indicates the tire radius. This indicates the distance from the vehicle's center of gravity to the rear axle. Indicates the longitudinal slip ratio of the front axle. Indicates the front axle lateral slip ratio. Indicates the longitudinal slip ratio of the rear axle. This indicates the rear axle lateral slip ratio.

[0043] In some embodiments of this application, the wheel-end torque parameters include wheel-end driving torque and wheel-end braking torque. The external yaw moment of the vehicle is calculated based on the tire dynamic vertical load, wheel-end torque parameters, and road surface adhesion coefficient, including: obtaining the vehicle's tire radius and track width; calculating the tire longitudinal force based on the wheel-end driving torque, wheel-end braking torque, tire dynamic vertical load, tire radius, and road surface adhesion coefficient; and determining the external yaw moment based on the tire longitudinal force and track width.

[0044] In some embodiments of this application, the wheel-end driving torque includes: the driving torque of the left front tire, the driving torque of the right front tire, the driving torque of the left rear tire, and the driving torque of the left rear tire. The wheel-end braking torque includes: the braking torque of the left front tire, the braking torque of the right front tire, the braking torque of the left rear tire, and the braking torque of the left rear tire. The wheel-end driving torque and wheel-end braking torque can be acquired in real time by a torsional torque sensor.

[0045] In some embodiments of this application, the road surface adhesion coefficient can be a core parameter describing the magnitude of friction between the tire and the road surface, reflecting the road surface's grip capability. It is equal to the ratio of the maximum adhesion force the tire can obtain to the tire's vertical load. For example, during vehicle operation, the vehicle's Electronic Stability Program (ESP) or Traction Control System (TCS) collects the tire's longitudinal force (derived from driving / braking torque) and the tire's dynamic vertical load (calculated through a load transfer model). The extreme value of the ratio between the two (i.e., the value at the critical state where the tire is about to slip) is taken as the current road surface adhesion coefficient.

[0046] In some embodiments of this application, the longitudinal force of the tire may include: longitudinal force of the left front tire, longitudinal force of the right front tire, longitudinal force of the left rear tire, and longitudinal force of the right rear tire.

[0047] In one example, the longitudinal force of the tire can be calculated using the following formula: In the above formula, This indicates the longitudinal force on the left front tire. This indicates the longitudinal force on the right front tire. This indicates the longitudinal force on the left rear tire. This indicates the longitudinal force on the right rear tire. This indicates the driving torque of the left front tire. This indicates the driving torque of the right front tire. This indicates the driving torque of the left rear tire. This indicates the driving torque of the right rear tire. This indicates the braking torque of the left front tire. This indicates the braking torque of the right front tire. This indicates the braking torque of the left rear tire. This indicates the braking torque of the right rear tire. This indicates the dynamic vertical load on the left front wheel. This indicates the dynamic vertical load on the right front wheel. This indicates the dynamic vertical load on the left rear wheel. This indicates the dynamic vertical load on the right rear wheel. This represents the road surface adhesion coefficient.

[0048] In the above formula, This represents the theoretical longitudinal force of the left front tire. The maximum longitudinal force of the left front tire is represented by the value of the minimum between the theoretical left front tire longitudinal force and the maximum left front tire longitudinal force. Then, the maximum value between the opposites of the candidate left front tire longitudinal force and the maximum left front tire longitudinal force is selected as the final left front tire longitudinal force. This process is repeated to obtain the longitudinal force of each tire. Based on the above, this embodiment ensures that under driving conditions, the tire longitudinal force does not exceed the maximum driving force that the road surface can provide, and under braking conditions, the tire longitudinal force does not exceed the maximum braking force that the road surface can provide. This limits the tire longitudinal force within the road surface adhesion limit range, achieving the technical effect of preventing tire slippage.

[0049] In one example, the external yaw moment can be calculated using the following formula: In the above formula, This indicates the longitudinal force on the left front tire. This indicates the longitudinal force on the right front tire. This indicates the longitudinal force on the left rear tire. This indicates the longitudinal force on the right rear tire. Indicates the external yaw moment. This indicates 1 / 2 wheel track.

[0050] In some embodiments of this application, the lateral forces of the front and rear axles of a vehicle are determined using a pre-built tire model based on the front and rear axle slip ratio and the road surface adhesion coefficient, including: obtaining a preset adhesion coefficient adjustment factor and adhesion coefficient correction factor; and using the tire model to determine the lateral forces of the front and rear axles based on the adhesion coefficient adjustment factor, adhesion coefficient correction factor, front and rear axle slip ratio and the road surface adhesion coefficient.

[0051] In some embodiments of this application, the Actual Friction Coefficient Adjustment Factor can be used to correct the actual usable friction coefficient of the tire under high slip ratios. The friction coefficient adjustment factor can dynamically adjust the effective value of the road surface friction coefficient according to the increase of the slip ratio. For example, as the front and rear axle slip ratios increase, the effective value of the road surface friction coefficient is dynamically decreased. The friction coefficient adjustment factor can be obtained based on R&D experience or laboratory testing. It can be a fixed value, or the friction coefficient adjustment factor can be larger as the front and rear axle slip ratios increase, establishing a positive correlation between the front and rear axle slip ratios and the friction coefficient adjustment factor.

[0052] In some embodiments of this application, the incremental friction coefficient correction term is a correction parameter for the gradient of the road surface friction coefficient under high slip ratios. It is used to adjust the decay rate of the road surface friction coefficient as the slip ratio increases, making the model more closely reflect the friction characteristics of different tires / road surfaces under high slip. For example, the larger the friction coefficient correction term, the greater the decay rate of the road surface friction coefficient as the slip ratio increases; the smaller the friction coefficient correction term, the smaller the decay rate of the road surface friction coefficient as the slip ratio increases.

[0053] In one example, the lateral forces on the front and rear axles can be calculated using a tire model with the following formula: In the above formula, Indicates longitudinal tire stiffness. Indicates lateral tire stiffness. Indicates the longitudinal stiffness coefficient. Indicates the lateral stiffness coefficient. The vertical force correction factor, representing longitudinal stiffness, can be obtained from R&D experience and laboratory tests. This refers to the dynamic vertical load on the tire (e.g., any one of the dynamic vertical loads of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel). This indicates the tire reference vertical load (e.g., any one of the following: left front wheel reference vertical load, right front wheel reference vertical load, left rear wheel reference vertical load, and right rear wheel reference vertical load). , , These represent the vertical force correction coefficients for lateral stiffness, which can be obtained based on R&D experience and laboratory tests.

[0054] In one example, when calculating the longitudinal and lateral tire stiffness of the left front wheel, This indicates the dynamic vertical load on the left front wheel. This represents the reference vertical load on the left front wheel. Similarly, the longitudinal and lateral tire stiffness of each tire can be calculated.

[0055] In the above formula, Indicates the longitudinal tire slippage. Indicates the amount of lateral tire slip. Indicates longitudinal tire stiffness. Indicates lateral tire stiffness. Indicates the longitudinal slip ratio of the tire. Indicates the tire's lateral slip ratio. Indicates the road surface adhesion coefficient. This indicates the dynamic vertical load on the tire.

[0056] In one example, when calculating the longitudinal tire slip and lateral tire slip of the left front tire, This indicates the longitudinal tire stiffness of the left front tire. This indicates the lateral stiffness of the left front tire. This indicates the longitudinal slip ratio of the left front tire. This indicates the tire lateral slip ratio of the left front tire. This represents the dynamic vertical load on the left front tire. Similarly, the longitudinal and lateral tire slippage of each tire can be calculated.

[0057] In the above formula, Indicates the longitudinal tire slippage. Indicates the amount of lateral tire slip. This indicates the total slip.

[0058] In one example, the combined slip of the left front tire is calculated based on its longitudinal and lateral tire slip. This process is repeated for each tire to calculate its combined slip.

[0059] In the above formula, Indicates the total slip. Constants representing tire models (such as constants controlling the shape of the curve that control slip characteristics). Represents an exponential function. This represents the original normalization factor.

[0060] In one example, when calculating the original normalization factor for the left front tire, it can be calculated based on the left front tire's constant E and its total slip. This process can be repeated to calculate the original normalization factor for each tire.

[0061] In the above formula, Represents the original normalization factor. This represents the adhesion coefficient adjustment factor. This represents the adhesion coefficient correction factor. Indicates the total slip. This represents the corrected normalization factor.

[0062] In some embodiments of this application, the adhesion coefficient adjustment factors corresponding to different tires of the vehicle may be the same or different, and the adhesion coefficient correction factors corresponding to different tires of the vehicle may also be the same or different.

[0063] In one example, the normalized factor corrected for the left front tire can be calculated based on the original normalized factor of the left front tire, the adhesion coefficient adjustment factor of the left front tire, the adhesion coefficient correction factor of the left front tire, and the overall slip of the left front tire. This process is repeated for each tire to calculate its corrected normalized factor.

[0064] In the above formula, This represents the correction factor for normalized slip. Indicates longitudinal tire stiffness. Indicates lateral tire stiffness. This represents the adhesion coefficient adjustment factor. This indicates the total slip.

[0065] In one example, the normalized slip correction factor includes the normalized slip correction factor for the left front tire, the normalized slip correction factor for the left rear tire, and the normalized slip correction factor for the right rear tire.

[0066] In the above formula, This represents the normalized vertical offset. This represents the normalized lateral offset. This represents the correction factor for normalized slip. This indicates the longitudinal offset of the tire. This indicates the lateral offset of the tire.

[0067] In the above formula, This represents the normalized vertical offset. This represents the normalized lateral offset. This represents the normalized overall slip.

[0068] In the above formula, Indicates the road surface adhesion coefficient. Indicates the dynamic vertical load on the tire. This represents the corrected normalization factor. This represents the normalized vertical offset. This represents the normalized overall slip. This indicates the lateral forces on the front and rear axles (which may include the lateral forces on the front and rear axles).

[0069] In some embodiments of this application, using a pre-built vehicle reference model, the yaw rate at the current moment can be calculated using the following formula based on the lateral forces of the front and rear axles and the external yaw moment: In the above formula, Indicates the overall vehicle weight. This indicates the lateral acceleration of the vehicle. Indicates the front axle measuring force. Indicates the lateral force on the rear axle. This represents the moment of inertia of the vehicle about its vertical axis (Z-axis). This represents the yaw rate at the current moment. This indicates the distance from the vehicle's center of gravity to the front axle. This indicates the distance from the vehicle's center of gravity to the rear axle. This indicates the external yaw moment.

[0070] When it is necessary to calculate the centroid sideslip angle at the current moment, This represents the yaw rate at the current moment. This represents the sideslip angle of the center of mass at the current moment. This indicates the lateral acceleration of the vehicle. This indicates the vehicle's longitudinal speed.

[0071] Based on the above, this embodiment adds an adhesion coefficient adjustment factor and an incremental adhesion coefficient correction factor to the tire model. This can accurately correct the difference in lateral force attenuation between the front and rear axles under large slip, eliminate the model defect of good fit under small and medium slip but large deviation under large slip, effectively improve the accuracy and applicability of the model under large slip ratio conditions, and make the model more consistent with the friction characteristics of real tires and road surfaces.

[0072] S202: Calculate the steering compensation angle required for the rear wheels of the vehicle based on the target yaw rate and the actual yaw rate of the vehicle.

[0073] In some embodiments of this application, the difference in yaw rate can be calculated based on the target yaw rate and the vehicle's actual yaw rate. Based on this difference, the steering compensation angle required for the rear wheels of the vehicle can be determined. The actual yaw rate can be directly measured by the vehicle's IMU (Inertial Measurement Unit).

[0074] In some embodiments of this application, the steering compensation angle required for the rear wheel steering of the vehicle is calculated based on the target yaw rate and the actual yaw rate of the vehicle, including: calculating the yaw rate difference based on the target yaw rate and the actual yaw rate of the vehicle; if the yaw rate difference exceeds a preset yaw rate range, determining the steering compensation angle required for the rear wheel steering of the vehicle based on the yaw rate difference.

[0075] In some embodiments of this application, the preset yaw rate range can be obtained based on research and development experience or laboratory testing. If the yaw rate difference does not exceed the preset yaw rate range, the rear wheels of the vehicle are controlled to steer based on the steering angle with respect to the speed ratio.

[0076] In some embodiments of this application, the steering compensation angle required for the rear wheel steering of the vehicle can be calculated using a PID algorithm (proportional-integral-derivative controller) based on the yaw rate difference.

[0077] S203: Determine the target steering angle of the vehicle based on the steering compensation angle and the speed ratio steering angle of the rear wheels.

[0078] In one embodiment, if the vehicle speed is high (e.g., greater than or equal to 80 km / h) and the coefficient of adhesion of the curve is high (e.g., on a dry road surface, the coefficient of adhesion is greater than or equal to 0.6), this embodiment can increase the steering angle with respect to the speed ratio based on the steering compensation angle to obtain the target steering angle of the vehicle, thereby avoiding understeer. If the vehicle speed is low (e.g., less than or equal to 40 km / h) and the coefficient of adhesion of the curve is low (e.g., on a snow-covered or icy road surface, the coefficient of adhesion is less than or equal to 0.4), this embodiment can decrease the steering angle with respect to the speed ratio based on the steering compensation angle to obtain the target steering angle of the vehicle, thereby avoiding oversteer.

[0079] When a vehicle's tires are unlikely to exceed their grip limit and can transmit sufficient lateral force, if the vehicle's active rear-wheel steering (RWS) actively controls the rear wheels to steer in the same direction according to the speed ratio method, the steering load that the front wheels need to bear will further increase, resulting in understeer.

[0080] S204: Based on the target steering angle, control the rear wheels of the vehicle to steer.

[0081] In some embodiments of this application, the rear wheels of a vehicle can be steered based on a target steering angle using an active rear wheel steering (RWS) system.

[0082] For example, the vehicle's Electronic Stability Program (ESP) or Traction Control System (TCS) sends a target steering angle to the active rear-wheel steering system, so that the active rear-wheel steering system can control the vehicle's rear wheels to steer based on the target steering angle.

[0083] Based on the above, this embodiment calculates the steering compensation angle based on the vehicle's state parameters and actual yaw rate to compensate for the speed-dependent steering angle of the rear wheels, thereby improving vehicle stability.

[0084] Please see Figure 3 This is a functional module diagram of a wheel steering control device 100 provided in an embodiment of this application.

[0085] In this embodiment, based on the above... Figure 2Following the same concept as the wheel steering control method in the illustrated embodiments, this application also provides a wheel steering control device 100, which can be used to execute the above-described wheel steering control method. For ease of explanation, the schematic diagram of the wheel steering control device 100 embodiment only shows the parts related to the embodiments of this application. Those skilled in the art will understand that the illustrated structure does not constitute a limitation on the wheel steering control device 100, and may include more or fewer components than illustrated, or combine certain components, or have different component arrangements.

[0086] Specifically, the wheel steering control device 100 provided in this application embodiment includes a first determining module 110, an angle calculation module 120, a second determining module 130, and a steering control module 140. The first determining module 110 is used to determine the target yaw rate of the vehicle based on the vehicle's state parameters during vehicle steering; the angle calculation module 120 is used to calculate the steering compensation angle required for the rear wheels of the vehicle to steer based on the target yaw rate and the actual yaw rate of the vehicle; the second determining module 130 is used to determine the target steering angle of the vehicle based on the steering compensation angle and the speed-ratio steering angle of the rear wheels; and the steering control module 140 is used to control the rear wheels of the vehicle to steer based on the target steering angle to improve the stability of the vehicle during steering.

[0087] Please see Figure 4 The diagram shown is a schematic of an electronic device provided in an embodiment of this application. The wheel steering control method provided in the above embodiment can be applied to one or more electronic devices 10. The electronic device 10 is a device that can automatically perform numerical calculations and / or information processing according to pre-set or stored instructions. Its hardware includes, but is not limited to, microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), embedded devices, etc.

[0088] This application embodiment also provides a vehicle 1, which includes an electronic device 10. The electronic device 10 can be an on-board device of the vehicle 1, such as any one of a Body Control Module (BCM), a Vehicle Control Unit (VCU), an Electronic Stability Program (ESP), and a Traction Control System (TCS).

[0089] Specifically, the electronic device 10 is used to: calculate the steering compensation angle based on the vehicle's state parameters and the vehicle's actual yaw rate, so as to compensate for the speed-ratio steering angle of the vehicle's rear wheels and improve the vehicle's stability when steering.

[0090] Combination Figure 4 As shown, in some embodiments of this application, the electronic device 10 includes, but is not limited to, a memory 11, a processor 12, and a computer program stored in the memory 11 and executable on the processor 12, such as a wheel steering control program. When the computer program is executed by the processor, it implements the wheel steering control method as described in the above embodiments.

[0091] Figure 4 Only the electronic device 10 with memory 11 and processor 12 is shown. It will be understood by those skilled in the art that... Figure 4 The structure shown does not constitute a limitation on the electronic device 10, and may include fewer or more components than shown, or combine certain components, or have different component arrangements.

[0092] The memory 11 in the electronic device 10 stores multiple computer-readable instructions to implement a wheel steering control method. The processor 12 can execute multiple instructions to: calculate the steering compensation angle based on the vehicle's state parameters and the vehicle's actual yaw rate, so as to compensate the speed-ratio steering angle of the vehicle's rear wheels to improve the stability of the vehicle when steering.

[0093] Specifically, the processor 12's implementation method for the above instructions can be found in [reference needed]. Figure 2 The descriptions of the relevant steps in the corresponding embodiments are not repeated here.

[0094] The memory 11 includes at least one type of computer-readable storage medium, which can be non-volatile or volatile. Computer-readable storage media include flash memory, portable hard drives, multimedia cards, card-type memories (e.g., SD memory, DX memory, etc.), magnetic memory, magnetic disks, optical disks, etc. In some embodiments, the memory 11 can be an internal storage unit of the electronic device 10, such as the portable hard drive of the electronic device 10. In other embodiments, the memory 11 can also be an external storage device of the electronic device 10, such as a plug-in portable hard drive, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the electronic device 10. The memory 11 can be used not only to store application software and various types of data installed on the electronic device 10, such as the code of a wheel steering control program, but also to temporarily store data that has been output or will be output.

[0095] In some embodiments, the processor 12 may be composed of integrated circuits, such as a single packaged integrated circuit or multiple integrated circuits packaged with the same or different functions, including combinations of one or more central processing units (CPUs), microprocessors, digital processing chips, graphics processors, and various control chips. The processor 12 is the control unit of the electronic device 10, connecting various components of the electronic device 10 via various interfaces and lines. It executes programs or modules stored in the memory 11 (e.g., executing a wheel steering control program) and calls data stored in the memory 11 to perform various functions and process data for the electronic device 10.

[0096] The processor 12 executes the operating system of the electronic device 10 and various installed applications. The processor 12 executes these applications to implement the steps described in each of the above-described wheel steering control method embodiments, for example... Figure 2 The steps are shown.

[0097] For example, a computer program may be divided into one or more modules / units, one or more of which are stored in memory 11 and executed by processor 12 to complete this application. One or more modules / units may be a series of computer-readable instruction segments capable of performing a specific function, which describe the execution process of the computer program in electronic device 10. For example, the computer program may be divided into a first determining module 110, an angle calculation module 120, a second determining module 130, and a steering control module 140.

[0098] The integrated unit implemented as a software functional module described above can be stored in a computer-readable storage medium. This software functional module, stored in a storage medium, includes several instructions to cause a computer device (which may be a personal computer, computer equipment, or network device, etc.) or processor to execute a portion of a wheel steering control method according to various embodiments of this application.

[0099] If the modules / units integrated in the electronic device 10 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware devices. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above.

[0100] Computer programs include computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. Computer-readable media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory, and other types of memory.

[0101] Furthermore, the computer-readable storage medium may primarily include a stored program area and a stored data area, wherein the stored program area may store the operating system, an application program required for at least one function, etc.; and the stored data area may store data created based on the use of blockchain nodes, etc.

[0102] The bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This bus can be divided into address bus, data bus, control bus, etc. For ease of representation, in... Figure 4 The symbol is represented by only one arrow, but this does not mean that there is only one bus or one type of bus. The bus is configured to implement communication between memory 11 and at least one processor 12, etc.

[0103] This application also provides a computer-readable storage medium (not shown), which stores computer-readable instructions that are executed by a processor in an electronic device to implement a wheel steering control method of any of the above embodiments.

[0104] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0105] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0106] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0107] Furthermore, it is clear that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units or devices described in the specification may also be implemented by a single unit or device through software or hardware. Terms such as "first," "second," etc., are used to indicate names and do not indicate any specific order.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A wheel steering control method, characterized in that, The method includes: During vehicle steering, the target yaw rate of the vehicle is determined based on the vehicle's state parameters; Based on the target yaw rate and the actual yaw rate of the vehicle, calculate the steering compensation angle required for the rear wheel steering of the vehicle; The target steering angle of the vehicle is determined based on the steering compensation angle and the speed ratio steering angle of the rear wheels of the vehicle. Based on the target steering angle, the rear wheels of the vehicle are controlled to steer.

2. The wheel steering control method as described in claim 1, characterized in that, The state parameters include steering parameters, acceleration parameters, wheel-end moment parameters, road adhesion coefficient, the sideslip angle of the center of gravity at the previous moment based on the current moment, and the yaw rate at the previous moment. Determining the target yaw rate of the vehicle based on the vehicle's state parameters includes: Using a pre-built vehicle load transfer model, the dynamic vertical load on the vehicle's tires is determined based on the acceleration parameters; Based on the steering parameters, the sideslip angle of the center of gravity at the previous moment, and the yaw rate at the previous moment, the front and rear axle slip ratios of the vehicle are obtained. The external yaw moment of the vehicle is calculated based on the tire dynamic vertical load, the wheel end moment parameters, and the road surface adhesion coefficient. Using a pre-built tire model, the lateral forces of the front and rear axles of the vehicle are determined based on the front and rear axle slip ratios and the road surface adhesion coefficient. Using a pre-built vehicle reference model, the yaw rate at the current moment is determined based on the front and rear axle lateral forces and the external yaw moment; The current yaw rate is taken as the target yaw rate.

3. The wheel steering control method as described in claim 2, characterized in that, The determination of the lateral forces on the front and rear axles of the vehicle using a pre-built tire model, based on the front and rear axle slip ratios and the road adhesion coefficient, includes: Obtain the preset adhesion coefficient adjustment factor and adhesion coefficient correction factor; Using the tire model, the front and rear axle lateral forces are determined based on the adhesion coefficient adjustment factor, the adhesion coefficient correction factor, the front and rear axle slip ratios, and the road surface adhesion coefficient.

4. The wheel steering control method as described in claim 2, characterized in that, The acceleration parameters include the vehicle's longitudinal acceleration and lateral acceleration. The step of determining the vehicle's dynamic vertical tire load based on the acceleration parameters using a pre-built vehicle load transfer model includes: Using the vehicle load transfer model, the longitudinal load offset, lateral load offset, and static vertical load of the tires are obtained. The dynamic vertical load of the tire is determined based on the longitudinal acceleration, the lateral acceleration, the longitudinal load offset, the lateral load offset, and the static vertical load of the tire.

5. The wheel steering control method as described in claim 2, characterized in that, The steering parameters include tire steering angle, longitudinal vehicle speed, and tire rotational speed. The method of obtaining the front and rear axle slip ratios of the vehicle based on the steering parameters, the previous moment's center of gravity sideslip angle, and the previous moment's yaw rate includes: Obtain the tire radius and the position of the vehicle's center of gravity; The front and rear axle slip ratios are calculated based on the tire radius, the vehicle center of gravity position, the tire rotation angle, the longitudinal vehicle speed, the tire rotation speed, the center of gravity sideslip angle at the previous moment, and the yaw rate at the previous moment.

6. The wheel steering control method as described in claim 2, characterized in that, The wheel-end torque parameters include wheel-end driving torque and wheel-end braking torque. The calculation of the vehicle's external yaw moment based on the tire dynamic vertical load, the wheel-end torque parameters, and the road surface adhesion coefficient includes: Obtain the tire radius and track width of the vehicle; The longitudinal force of the tire is calculated based on the wheel-end driving torque, the wheel-end braking torque, the tire dynamic vertical load, the tire radius, and the road adhesion coefficient. The external yaw moment is determined based on the longitudinal force of the tire and the wheel track.

7. The wheel steering control method as described in claim 1, characterized in that, The step of calculating the steering compensation angle required for the rear wheel steering of the vehicle based on the target yaw rate and the actual yaw rate of the vehicle includes: Calculate the yaw rate difference based on the target yaw rate and the actual yaw rate of the vehicle; If the yaw rate difference exceeds a preset yaw rate range, the steering compensation angle required for the rear wheel steering of the vehicle is determined based on the yaw rate difference.

8. An electronic device, characterized in that, The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the wheel steering control method as described in any one of claims 1 to 7.

9. A vehicle, characterized in that, The vehicle includes the electronic equipment as described in claim 8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the wheel steering control method as described in any one of claims 1 to 7.

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