Vehicle brake-by-wire method and system

Abstract

The invention relates to a vehicle brake-by-wire method and system, and relates to the technical field of brake-by-wire, and the method comprises the steps: obtaining environment information around a vehicle and vehicle attitude information; identifying road conditions based on the environment information and obtaining dynamic parameters of the vehicle based on the vehicle attitude information and a vehicle dynamics model; obtaining a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and the potential risk of the vehicle under the current road condition; determining a braking force distribution proportion and an adjustment amount of each wheel by using a braking force distribution matrix and a braking force adjustment algorithm based on the vehicle state evaluation result; and adjusting the brake fluid pressure of each wheel based on the determined brake force distribution ratio and adjustment amount of each wheel.

Description

Technical Field

[0001] The present application relates to the technical field of wire-controlled braking, and in particular to a vehicle wire-controlled braking method and system. Background Art

[0002] In the field of modern transportation, the vehicle's braking system plays a vital role in ensuring the vehicle's driving safety and performance. Traditional vehicle braking systems are mainly based on mechanical and hydraulic principles, and their braking force distribution often adopts a relatively fixed method. For example, for most vehicles, the braking force distribution between the front and rear wheels is pre-set according to the static axle load distribution of the vehicle, and can only be adjusted to a limited extent under different driving conditions. This traditional braking system has exposed many limitations when dealing with increasingly complex traffic environments and diverse road conditions.

[0003] How to solve the above problems is a technical problem that technicians in this field need to overcome. Summary of the invention

[0004] In order to at least partially solve the above technical problems, the present application provides a vehicle wire control braking method and system.

[0005] In a first aspect, a vehicle wire-control braking method provided in the present application adopts the following technical solution.

[0006] A vehicle brake-by-wire method, comprising: Obtaining environmental information around the vehicle and vehicle posture information; Identifying road conditions based on the environmental information and obtaining dynamic parameters of the vehicle based on the vehicle posture information and a vehicle dynamics model; Obtaining a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and potential risks of the vehicle under the current road condition; Determine the braking force distribution ratio and adjustment amount of each wheel by using a braking force distribution matrix and a braking force adjustment algorithm based on the vehicle state evaluation result; The brake fluid pressure of each wheel is adjusted based on the determined braking force distribution ratio and adjustment amount of each wheel.

[0007] By adopting the above technical solution,

[0008] Optionally, identifying the road condition based on the environmental information includes: Use the on-board camera to collect image information around the vehicle; Processing the collected image information to extract road features; the road features include road surface texture, logo, color and surrounding object features; The road conditions are divided into different categories according to the extracted road features, and the different categories of road conditions include dry road surface, wet road surface and icy road surface.

[0009] Optionally, obtaining the dynamic parameters of the vehicle based on the vehicle posture information and the vehicle dynamics model includes: Measuring the vehicle's acceleration, angular velocity and attitude angle based on an inertial measurement unit; Based on the vehicle dynamics model, calculate the vehicle's speed, center of mass position, center of mass sideslip angle and vertical load of each wheel; The vehicle's roll moment and pitch moment are calculated based on the vehicle's suspension system characteristics and tire characteristics.

[0010] Optionally, obtaining a vehicle state assessment result based on the identified road condition and the vehicle dynamic parameters includes: According to the identified road conditions, the basic braking characteristics of the vehicle under the current road conditions are determined; wherein, for a dry road surface, the braking friction coefficient range is determined to be the first braking friction coefficient range, and the maximum allowable braking deceleration is the first maximum braking deceleration; for a slippery road surface, the braking friction coefficient range is determined to be the second braking friction coefficient range, the maximum allowable braking deceleration is the second maximum braking deceleration, and the second braking friction coefficient range is smaller than the first braking friction coefficient range, and the second maximum braking deceleration is smaller than the first maximum braking deceleration; for an icy road surface, the braking friction coefficient range is determined to be the third braking friction coefficient range, the maximum allowable braking deceleration is the third maximum braking deceleration, and the third braking friction coefficient range is smaller than the second braking friction coefficient range, and the third maximum braking deceleration is smaller than the second maximum braking deceleration; Combine the vehicle's dynamic parameters to evaluate the vehicle's driving stability; The vehicle state assessment results are obtained based on the basic braking characteristics of the road conditions and the driving stability of the vehicle and are divided into different levels; the different levels include safe state, low-risk state, medium-risk state and high-risk state.

[0011] Optionally, a vehicle state assessment result is obtained based on basic braking characteristics of road conditions and driving stability of the vehicle and the vehicle state assessment result is divided into different levels, including: When the vehicle is on a dry road, the speed does not exceed the first speed threshold, the center of mass position offset does not exceed the first center of mass offset threshold, and the acceleration does not exceed the first acceleration threshold, and the center of mass side slip angle does not exceed the first side slip angle threshold, the vehicle state assessment result is classified as a safe state; when the vehicle is on a slippery road, the speed is greater than the first speed threshold and less than the second speed threshold, the center of mass position offset is greater than the first center of mass offset threshold and less than the second center of mass offset threshold, or the maximum difference in wheel vertical load is greater than the first load difference threshold and less than the second load difference threshold, the vehicle state assessment result is classified as a low-risk state; when the vehicle is on an icy road, the speed is greater than the second speed threshold, or the center of mass side slip angle is greater than the second side slip angle threshold, or the slip rate of the wheel during braking is greater than the first slip rate threshold, the vehicle state assessment result is classified as a medium-risk state; When the vehicle is in any road condition, the speed is greater than the third speed threshold, the center of mass position offset is greater than the second center of mass offset threshold, the acceleration is greater than the second acceleration threshold, or the maximum difference in wheel vertical load is greater than the second load difference threshold, the vehicle state assessment result is classified as a high-risk state.

[0012] Optionally, based on the vehicle state evaluation result, a braking force distribution matrix and a braking force adjustment algorithm are used to determine the braking force distribution ratio and adjustment amount of each wheel, including: According to the vehicle state evaluation result, the corresponding initial braking force distribution ratio range is searched in the braking force distribution matrix; wherein the braking force distribution matrix stores the braking force distribution ratio range of each wheel under different vehicle state evaluation results; for a safe state, the first braking force distribution ratio range is searched; for a low-risk state, the second braking force distribution ratio range is searched; for a medium-risk state, the third braking force distribution ratio range is searched; for a high-risk state, the fourth braking force distribution ratio range is searched; The vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration are used as input parameters and input into the braking force adjustment algorithm. The initial braking force distribution ratio range found in the braking force distribution matrix is ​​adjusted according to the input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel.

[0013] Optionally, adjusting the initial braking force distribution ratio range found from the braking force distribution matrix according to the input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel includes: The deceleration, wheel slip rate, yaw rate and wheel angular acceleration of the input vehicle are input as input vectors into a neural network; the neural network considers the optimal braking force distribution under different input parameter combinations during the training process; After the forward propagation calculation of the neural network, the braking force distribution ratio and adjustment amount of each wheel are obtained; The initial ratio range provided by the comprehensive braking force distribution matrix and the adjustment amount obtained by the braking force adjustment algorithm are used to determine the final braking force distribution ratio and adjustment amount of each wheel.

[0014] Optionally, the neural network has the following structure: an input layer includes four neurons, which receive the vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration; two hidden layers, the first hidden layer includes 16 neurons, and the second hidden layer includes 8 neurons; the output layer includes eight neurons, of which the first four neurons output the braking force distribution ratio of each wheel, and the last four neurons output the braking force adjustment amount of each wheel; the mean square error is used as the loss function; vehicle data of various braking operations performed by the vehicle under different road conditions are collected as training samples, and the vehicle data includes the vehicle's deceleration, wheel slip rate, yaw angular velocity, wheel angular acceleration and the corresponding optimal braking force distribution ratio and adjustment amount; the training data is input into the neural network, and forward propagation calculation is performed, and back propagation is performed to update the network weights and bias according to the mean square error between the calculated result and the true result, and the iteration is repeated until the loss value is less than the first preset value.

[0015] Optionally, the step of establishing the braking force distribution matrix includes: The vehicle status assessment results are divided into multiple status categories based on various possible road conditions and different driving states of the vehicle; For each state category, the braking force distribution ratio range of each wheel is preliminarily determined by combining vehicle dynamics theory and historical braking data; Using vehicle dynamics simulation software to simulate and verify the initially determined braking force distribution ratio range; adjusting the braking force distribution ratio range according to the simulation results; Conduct braking tests on different test sites according to the above different state categories and test scenarios; collect actual vehicle braking data, analyze the performance of the vehicle when braking according to the preliminary braking force distribution ratio range under different states, and adjust the braking force distribution ratio range according to the test results of the performance; The braking force distribution ratio range of each wheel under different vehicle state evaluation results determined after theoretical analysis, simulation verification and test verification is stored in a braking force distribution matrix.

[0016] In a second aspect, a vehicle wire control brake system provided in the present application adopts the following technical solution.

[0017] A brake-by-wire system for an unmanned vehicle, comprising: The first processing module is used to: obtain the environment information around the vehicle and the vehicle posture information; A second processing module is used to: identify the road condition based on the environmental information and obtain the dynamic parameters of the vehicle based on the vehicle posture information and the vehicle dynamics model; A third processing module is used to: obtain a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and potential risks of the vehicle under the current road condition; A fourth processing module is used to determine the braking force distribution ratio and adjustment amount of each wheel by using a braking force distribution matrix and a braking force adjustment algorithm based on the vehicle state evaluation result; The fifth processing module is used to adjust the brake fluid pressure of each wheel based on the determined braking force distribution ratio and adjustment amount of each wheel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a vehicle wire control braking method according to an embodiment of the present application; Figure 2 is a system block diagram of a vehicle brake-by-wire system according to an embodiment of the present application; In the figure, 201 is a first processing module; 202 is a second processing module; 203 is a third processing module; 204 is a fourth processing module; 205 is a fifth processing module. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1-2 The present application is further described with specific embodiments: The present application discloses a vehicle brake-by-wire method, comprising the following steps: Step 101, obtain the environmental information around the vehicle and the vehicle posture information. Specifically, the environmental information around the vehicle can be collected by various sensors installed on the vehicle, such as cameras, millimeter wave radars, laser radars, ultrasonic sensors, etc., and the information of the vehicle's external environment includes road conditions such as road surface texture, color, whether there are obstacles, the position and speed of other vehicles, and traffic signs. Vehicle posture information is data that describes the position and motion posture of the vehicle in space, usually measured by an inertial measurement unit. The vehicle posture information includes the vehicle's acceleration: longitudinal acceleration, lateral acceleration, angular velocity, and posture angle.

[0020] Step 102: Identify the road conditions based on the environmental information and obtain the dynamic parameters of the vehicle based on the vehicle posture information and the vehicle dynamics model. The vehicle dynamics model is a mathematical model established based on the principles of physics, and is used to describe the motion of the vehicle under the action of various forces and moments. The vehicle dynamics model is established based on the mass, moment of inertia, suspension system characteristics, tire characteristics, wheelbase, and track width of the vehicle. The dynamic parameters such as the center of mass position, center of mass sideslip angle, and vertical load of each wheel can be calculated through the vehicle dynamics model. The dynamic parameters of the vehicle will change in real time with the driving state of the vehicle and the changes in the external environment, and are used to evaluate the driving state and braking requirements of the vehicle.

[0021] Step 103, based on the identified road conditions and the vehicle dynamic parameters, a vehicle state assessment result is obtained; the vehicle state assessment result is obtained based on the driving state and potential risks of the vehicle under the current road conditions. The vehicle state and potential risks under the current state are comprehensively evaluated according to the current road conditions and dynamic parameters of the vehicle. The vehicle state assessment results are generally divided into different levels, such as safe state (the vehicle is stable and the risk is minimal), low-risk state (the vehicle may have slight instability factors, but the overall controllable), medium-risk state (the vehicle has a certain degree of instability and needs to take appropriate braking adjustments) and high-risk state (the vehicle is in an unstable state, may be out of control, and requires emergency braking adjustments).

[0022] Step 104: Based on the vehicle state evaluation result, the braking force distribution ratio and adjustment amount of each wheel are determined using the braking force distribution matrix and the braking force adjustment algorithm. The braking force distribution ratio is the basic value of the braking force distribution. The braking force distribution ratio obtains the initial distribution scheme from the braking force distribution matrix based on the vehicle state evaluation result, reflecting the approximate braking force distribution of the vehicle under different states. The braking force adjustment amount is a fine-tuning value calculated by the braking force adjustment algorithm based on this and the real-time information of the vehicle.

[0023] Ultimately, the actual braking force of each wheel is equal to the total braking force distributed according to the braking force distribution ratio, plus or minus the corresponding braking force adjustment amount. In this way, the braking system can accurately control the braking force of each wheel to ensure that the vehicle can achieve the best braking effect under different road conditions and driving conditions.

[0024] Step 105: Adjust the brake fluid pressure of each wheel based on the determined braking force distribution ratio and adjustment amount of each wheel.

[0025] Specifically, the environmental information around the vehicle and the vehicle posture information are obtained, and the dynamic parameters of the vehicle are calculated by identifying the road conditions and vehicle posture information and combining with the vehicle dynamics model; the vehicle state evaluation result is obtained according to the identified road conditions and dynamic parameters, and based on the vehicle state evaluation result, the braking force distribution ratio and adjustment amount of each wheel are determined using the braking force distribution matrix and the braking force adjustment algorithm. The braking force distribution matrix provides a basic value for the braking force distribution, and the braking force adjustment algorithm adjusts the braking force according to the real-time state of the vehicle. The two are combined to distribute the braking force according to the actual situation of the vehicle; the brake fluid pressure of each wheel is adjusted based on the determined braking force distribution ratio and adjustment amount of each wheel, so that the braking system can control the braking force of each wheel according to the different states and needs of the vehicle, thereby effectively shortening the braking distance under different road conditions, improving the braking stability of the vehicle, preventing wheel locking or vehicle loss of control, and significantly enhancing the braking performance and safety of the vehicle under various driving conditions, ensuring the safe driving of the vehicle.

[0026] As a specific implementation of a vehicle brake-by-wire method, identifying a road condition based on the environmental information includes: Use the on-board camera to collect image information around the vehicle; Processing the collected image information to extract road features; the road features include road surface texture, logo, color and surrounding object features; The road conditions are divided into different categories according to the extracted road features, and the different categories of road conditions include dry road surface, wet road surface and icy road surface.

[0027] Specifically, the on-board camera is used to collect image information around the vehicle, and the collected image information is processed to extract road features, and important information such as road surface texture, signs, color, and surrounding object features are filtered out from the image; the road conditions are divided into different categories according to the extracted road features.

[0028] As a specific implementation of a vehicle brake-by-wire method, the dynamic parameters of the vehicle are obtained based on the vehicle posture information and the vehicle dynamics model, including: Measuring the vehicle's acceleration, angular velocity and attitude angle based on an inertial measurement unit; Based on the vehicle dynamics model, calculate the vehicle's speed, center of mass position, center of mass sideslip angle and vertical load of each wheel; The vehicle's roll moment and pitch moment are calculated based on the vehicle's suspension system characteristics and tire characteristics.

[0029] Specifically, the acceleration, angular velocity and attitude angle of the vehicle are measured based on an inertial measurement unit; Based on the vehicle dynamics model, the vehicle speed, center of mass position, center of mass side slip angle and vertical load of each wheel are calculated. The calculated vehicle speed is used to characterize the vehicle's driving speed; the center of mass position is used to characterize the vehicle's weight distribution. When the vehicle brakes, the center of mass will shift, affecting the force of each wheel. The center of mass position information helps to avoid vehicle instability caused by improper braking force distribution, such as preventing excessive braking of the front wheels and insufficient braking force of the rear wheels due to the forward movement of the center of mass, or preventing the rear wheels from locking and the front wheels from braking insufficiently when the center of mass moves backward. The center of mass side slip angle is used to characterize whether the vehicle's driving trajectory is in line with expectations. When the center of mass side slip angle is large, it means that the vehicle may deviate. The vertical load of the wheel is used to characterize the weight borne by each wheel. Different vertical loads will affect the grip of the wheel. The vehicle's roll moment and pitch moment are calculated based on the vehicle's suspension system characteristics and tire characteristics. Rolling moment is used to characterize the roll of a vehicle when turning or passing through uneven roads. Excessive rolling moment may cause the vehicle to roll over. By calculating and monitoring it, the braking strategy can be adjusted in advance to ensure the stability of the vehicle. Pitching moment reflects the pitch of the vehicle during acceleration and braking. During emergency braking, a large pitching moment will cause the vehicle to tilt forward. At this time, the braking force distribution of the front and rear wheels can be adjusted based on this information to avoid the vehicle losing control due to excessive tilt.

[0030] As a specific implementation of a vehicle brake-by-wire method, a vehicle state evaluation result is obtained based on the identified road condition and the vehicle dynamic parameters, including: According to the identified road conditions, the basic braking characteristics of the vehicle under the current road conditions are determined; wherein, for a dry road surface, the braking friction coefficient range is determined to be the first braking friction coefficient range, and the maximum allowable braking deceleration is the first maximum braking deceleration; for a slippery road surface, the braking friction coefficient range is determined to be the second braking friction coefficient range, the maximum allowable braking deceleration is the second maximum braking deceleration, and the second braking friction coefficient range is smaller than the first braking friction coefficient range, and the second maximum braking deceleration is smaller than the first maximum braking deceleration; for an icy road surface, the braking friction coefficient range is determined to be the third braking friction coefficient range, the maximum allowable braking deceleration is the third maximum braking deceleration, and the third braking friction coefficient range is smaller than the second braking friction coefficient range, and the third maximum braking deceleration is smaller than the second maximum braking deceleration; Combine the vehicle's dynamic parameters to evaluate the vehicle's driving stability; The vehicle state assessment results are obtained based on the basic braking characteristics of the road conditions and the driving stability of the vehicle and are divided into different levels; the different levels include safe state, low-risk state, medium-risk state and high-risk state.

[0031] As one implementation of a vehicle brake-by-wire method, a vehicle state evaluation result is obtained based on basic braking characteristics of road conditions and driving stability of the vehicle and the vehicle state evaluation result is divided into different levels, including: When the vehicle is on a dry road, the speed does not exceed the first speed threshold, the center of mass position offset does not exceed the first center of mass offset threshold, and the acceleration does not exceed the first acceleration threshold, and the center of mass side slip angle does not exceed the first side slip angle threshold, the vehicle state assessment result is classified as a safe state; when the vehicle is on a slippery road, the speed is greater than the first speed threshold and less than the second speed threshold, the center of mass position offset is greater than the first center of mass offset threshold and less than the second center of mass offset threshold, or the maximum difference in wheel vertical load is greater than the first load difference threshold and less than the second load difference threshold, the vehicle state assessment result is classified as a low-risk state; when the vehicle is on an icy road, the speed is greater than the second speed threshold, or the center of mass side slip angle is greater than the second side slip angle threshold, or the slip rate of the wheel during braking is greater than the first slip rate threshold, the vehicle state assessment result is classified as a medium-risk state; When the vehicle is in any road condition, the speed is greater than the third speed threshold, the center of mass position offset is greater than the second center of mass offset threshold, the acceleration is greater than the second acceleration threshold, or the maximum difference in wheel vertical load is greater than the second load difference threshold, the vehicle state assessment result is classified as a high-risk state.

[0032] As one implementation of a vehicle brake-by-wire method, based on the vehicle state evaluation result, a braking force distribution matrix and a braking force adjustment algorithm are used to determine the braking force distribution ratio and adjustment amount of each wheel, including: According to the vehicle state evaluation result, the corresponding initial braking force distribution ratio range is searched in the braking force distribution matrix; wherein the braking force distribution matrix stores the braking force distribution ratio range of each wheel under different vehicle state evaluation results; for a safe state, the first braking force distribution ratio range is searched; for a low-risk state, the second braking force distribution ratio range is searched; for a medium-risk state, the third braking force distribution ratio range is searched; for a high-risk state, the fourth braking force distribution ratio range is searched; The vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration are used as input parameters and input into the braking force adjustment algorithm. The initial braking force distribution ratio range found in the braking force distribution matrix is ​​adjusted according to the input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel.

[0033] Specifically, according to the vehicle state assessment result, the corresponding initial braking force distribution ratio range is searched in the braking force distribution matrix, and a preliminary braking force distribution scheme is provided. When the vehicle is in a safe state, by searching the first braking force distribution ratio range, the braking system can ensure that the braking force is distributed to each wheel according to the conventional and verified ratio under the condition of stable vehicle operation, so as to ensure that the vehicle has good braking performance and maneuverability during normal driving, and avoid accidents caused by improper braking force distribution. When the vehicle is in a low-risk state, according to the second braking force distribution ratio range, the braking system can make adaptive adjustments in advance when the vehicle begins to have some minor unstable factors, such as slight changes in road conditions or slight fluctuations in vehicle dynamic parameters, to maintain the driving stability of the vehicle. For the third braking force distribution ratio range searched under the medium-risk state, the braking system prevents the risk from further expansion when the vehicle has a more obvious unstable situation, such as slight wheel slippage or vehicle deviation from the normal trajectory. In the high-risk state, the fourth braking force distribution ratio range is searched, so that the braking system can maximize the safety of the vehicle when the vehicle is in a critical situation where it may lose control. The vehicle's deceleration, wheel slip rate, yaw rate and wheel angular acceleration are used as input parameters to the braking force adjustment algorithm, and the initial braking force distribution ratio range is adjusted based on these key parameters that reflect the real-time status of the vehicle. When the vehicle's deceleration is large, it means that the vehicle needs stronger braking. The braking force adjustment algorithm can adjust the braking force distribution ratio and adjustment amount according to this situation to make braking more effective; when the wheel slip rate is high, it means that the wheel may be at risk of slipping. The algorithm can adjust the braking force distribution and appropriately reduce the braking force of the wheel to prevent locking and maintain the vehicle's steering ability; the change in yaw rate can reflect the steering stability of the vehicle, and adjusting the braking force according to its size can ensure that the vehicle will not lose control when turning; the wheel angular acceleration can reflect the rotation state of the wheel, and adjusting the braking force can ensure the normal rotation of the wheel and the stability of the vehicle.

[0034] As one implementation of a vehicle brake-by-wire method, adjusting the initial braking force distribution ratio range found from the braking force distribution matrix according to input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel includes: The deceleration, wheel slip rate, yaw rate and wheel angular acceleration of the input vehicle are input as input vectors into a neural network; the neural network considers the optimal braking force distribution under different input parameter combinations during the training process; After the forward propagation calculation of the neural network, the braking force distribution ratio and adjustment amount of each wheel are obtained; The initial ratio range provided by the comprehensive braking force distribution matrix and the adjustment amount obtained by the braking force adjustment algorithm are used to determine the final braking force distribution ratio and adjustment amount of each wheel.

[0035] As one of the implementation methods of a vehicle wire control braking method, the neural network has the following structure: an input layer includes four neurons, which receive the vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration; two hidden layers, the first hidden layer includes 16 neurons, and the second hidden layer includes 8 neurons; the output layer includes eight neurons, of which the first four neurons output the braking force distribution ratio of each wheel, and the last four neurons output the braking force adjustment amount of each wheel; the mean square error is used as the loss function; vehicle data of various braking operations performed by the vehicle under different road conditions are collected as training samples, and the vehicle data includes the vehicle's deceleration, wheel slip rate, yaw angular velocity, wheel angular acceleration and the corresponding optimal braking force distribution ratio and adjustment amount; the training data is input into the neural network, and forward propagation calculation is performed, and back propagation is performed to update the network weights and bias according to the mean square error between the calculated result and the true result, and iteration is repeated until the loss value is less than a first preset value.

[0036] As one implementation of a vehicle brake-by-wire method, the step of establishing the braking force distribution matrix includes: The vehicle status assessment results are divided into multiple status categories based on various possible road conditions and different driving states of the vehicle; For each state category, the braking force distribution ratio range of each wheel is preliminarily determined by combining vehicle dynamics theory and historical braking data; Using vehicle dynamics simulation software to simulate and verify the initially determined braking force distribution ratio range; adjusting the braking force distribution ratio range according to the simulation results; Conduct braking tests on different test sites according to the above different state categories and test scenarios; collect actual vehicle braking data, analyze the performance of the vehicle when braking according to the preliminary braking force distribution ratio range under different states, and adjust the braking force distribution ratio range according to the test results of the performance; The braking force distribution ratio range of each wheel under different vehicle state evaluation results determined after theoretical analysis, simulation verification and test verification is stored in a braking force distribution matrix.

[0037] Specifically, the vehicle state evaluation results are divided into multiple state categories based on various road conditions and different driving states that may occur in the vehicle; for each state category, the braking force distribution ratio range of each wheel is preliminarily determined in combination with vehicle dynamics theory and historical braking data. The preliminarily determined braking force distribution ratio range is simulated and verified using vehicle dynamics simulation software. By simulating various complex situations, potential problems such as wheel locking, vehicle loss of control or excessive braking distance that may occur under certain road conditions are discovered in advance. The braking force distribution ratio range is adjusted according to the simulation results; test scenarios are set up on different test sites according to different state categories for braking tests and actual vehicle braking data is collected. By analyzing the performance of the actual vehicle when braking according to the preliminary braking force distribution ratio range under different states, further adjustments are made according to the test results to make the braking force distribution ratio range more in line with the actual situation. Finally, the braking force distribution ratio range of each wheel under different vehicle state evaluation results determined after theoretical analysis, simulation verification and test verification is stored in the braking force distribution matrix.

[0038] The present application also provides a vehicle brake-by-wire system, comprising: The first processing module 201 is used to obtain the environment information around the vehicle and the vehicle posture information; The second processing module 202 is used to: identify the road condition based on the environmental information and obtain the dynamic parameters of the vehicle based on the vehicle posture information and the vehicle dynamics model; The third processing module 203 is used to obtain a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and potential risks of the vehicle under the current road condition; The fourth processing module 204 is used to determine the braking force distribution ratio and adjustment amount of each wheel by using the braking force distribution matrix and the braking force adjustment algorithm based on the vehicle state evaluation result; The fifth processing module 205 is used to adjust the brake fluid pressure of each wheel based on the determined braking force distribution ratio and adjustment amount of each wheel.

[0039] It should be noted that the above embodiments are only used to illustrate the present application and are not intended to limit the technical solutions described in the present application. Although the present application has been described in detail in this specification with reference to the above embodiments, a person of ordinary skill in the art should understand that a person of ordinary skill in the art can still modify or make equivalent substitutions to the present application, and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present application should be included in the scope of the claims of the present application.

Claims

1. A vehicle brake-by-wire method, characterized in that: include: Obtaining environmental information around the vehicle and vehicle posture information; Identifying road conditions based on the environmental information and obtaining dynamic parameters of the vehicle based on the vehicle posture information and a vehicle dynamics model; Obtaining a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and potential risks of the vehicle under the current road condition; Determine the braking force distribution ratio and adjustment amount of each wheel by using a braking force distribution matrix and a braking force adjustment algorithm based on the vehicle state evaluation result; The brake fluid pressure of each wheel is adjusted based on the determined braking force distribution ratio and adjustment amount of each wheel.

2. A vehicle brake-by-wire method according to claim 1, characterized in that: Identifying a road condition based on the environmental information includes: Use the on-board camera to collect image information around the vehicle; Processing the collected image information to extract road features; the road features include road surface texture, logo, color and surrounding object features; The road conditions are divided into different categories according to the extracted road features, and the different categories of road conditions include dry road surface, wet road surface and icy road surface.

3. A vehicle brake-by-wire method according to claim 2, characterized in that: The dynamic parameters of the vehicle are obtained based on the vehicle posture information and the vehicle dynamics model, including: Measuring the vehicle's acceleration, angular velocity and attitude angle based on an inertial measurement unit; Based on the vehicle dynamics model, calculate the vehicle's speed, center of mass position, center of mass sideslip angle and vertical load of each wheel; The vehicle's roll moment and pitch moment are calculated based on the vehicle's suspension system characteristics and tire characteristics.

4. A vehicle brake-by-wire method according to claim 3, characterized in that: Obtaining a vehicle state assessment result based on the identified road condition and the vehicle dynamic parameters, including: According to the identified road conditions, the basic braking characteristics of the vehicle under the current road conditions are determined; wherein, for a dry road surface, the braking friction coefficient range is determined to be the first braking friction coefficient range, and the maximum allowable braking deceleration is the first maximum braking deceleration; for a slippery road surface, the braking friction coefficient range is determined to be the second braking friction coefficient range, the maximum allowable braking deceleration is the second maximum braking deceleration, and the second braking friction coefficient range is smaller than the first braking friction coefficient range, and the second maximum braking deceleration is smaller than the first maximum braking deceleration; for an icy road surface, the braking friction coefficient range is determined to be the third braking friction coefficient range, the maximum allowable braking deceleration is the third maximum braking deceleration, and the third braking friction coefficient range is smaller than the second braking friction coefficient range, and the third maximum braking deceleration is smaller than the second maximum braking deceleration; Combine the vehicle's dynamic parameters to evaluate the vehicle's driving stability; The vehicle state assessment results are obtained based on the basic braking characteristics of the road conditions and the driving stability of the vehicle and are divided into different levels; the different levels include safe state, low-risk state, medium-risk state and high-risk state.

5. The vehicle brake-by-wire method according to claim 4, characterized in that: The vehicle status assessment results are obtained based on the basic braking characteristics of the road conditions and the driving stability of the vehicle and are divided into different levels, including: When the vehicle is on a dry road, the speed does not exceed the first speed threshold, the center of mass position offset does not exceed the first center of mass offset threshold, and the acceleration does not exceed the first acceleration threshold, and the center of mass side slip angle does not exceed the first side slip angle threshold, the vehicle state assessment result is classified as a safe state; when the vehicle is on a slippery road, the speed is greater than the first speed threshold and less than the second speed threshold, the center of mass position offset is greater than the first center of mass offset threshold and less than the second center of mass offset threshold, or the maximum difference in wheel vertical load is greater than the first load difference threshold and less than the second load difference threshold, the vehicle state assessment result is classified as a low-risk state; when the vehicle is on an icy road, the speed is greater than the second speed threshold, or the center of mass side slip angle is greater than the second side slip angle threshold, or the slip rate of the wheel during braking is greater than the first slip rate threshold, the vehicle state assessment result is classified as a medium-risk state; When the vehicle is in any road condition, the speed is greater than the third speed threshold, the center of mass position offset is greater than the second center of mass offset threshold, the acceleration is greater than the second acceleration threshold, or the maximum difference in wheel vertical load is greater than the second load difference threshold, the vehicle state assessment result is classified as a high-risk state.

6. A vehicle brake-by-wire method according to claim 5, characterized in that: Based on the vehicle state evaluation result, the braking force distribution matrix and the braking force adjustment algorithm are used to determine the braking force distribution ratio and adjustment amount of each wheel, including: According to the vehicle state evaluation result, the corresponding initial braking force distribution ratio range is searched in the braking force distribution matrix; wherein the braking force distribution matrix stores the braking force distribution ratio range of each wheel under different vehicle state evaluation results; for a safe state, the first braking force distribution ratio range is searched; for a low-risk state, the second braking force distribution ratio range is searched; for a medium-risk state, the third braking force distribution ratio range is searched; for a high-risk state, the fourth braking force distribution ratio range is searched; The vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration are used as input parameters and input into the braking force adjustment algorithm. The initial braking force distribution ratio range found in the braking force distribution matrix is ​​adjusted according to the input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel.

7. A vehicle brake-by-wire method according to claim 6, characterized in that: The initial braking force distribution ratio range found from the braking force distribution matrix is ​​adjusted according to the input parameters to determine the final braking force distribution ratio and adjustment amount of each wheel, including: The deceleration, wheel slip rate, yaw rate and wheel angular acceleration of the input vehicle are input as input vectors into a neural network; the neural network considers the optimal braking force distribution under different input parameter combinations during the training process; After the forward propagation calculation of the neural network, the braking force distribution ratio and adjustment amount of each wheel are obtained; The initial ratio range provided by the comprehensive braking force distribution matrix and the adjustment amount obtained by the braking force adjustment algorithm are used to determine the final braking force distribution ratio and adjustment amount of each wheel.

8. The vehicle brake-by-wire method according to claim 7, characterized in that: The neural network has the following structure: an input layer includes four neurons, which receive the vehicle's deceleration, wheel slip rate, yaw angular velocity and wheel angular acceleration; two hidden layers, the first hidden layer includes 16 neurons, and the second hidden layer includes 8 neurons; the output layer includes eight neurons, wherein the first four neurons output the braking force distribution ratio of each wheel, and the last four neurons output the braking force adjustment amount of each wheel; the mean square error is used as the loss function; vehicle data of various braking operations performed by the vehicle under different road conditions are collected as training samples, and the vehicle data includes the vehicle's deceleration, wheel slip rate, yaw angular velocity, wheel angular acceleration and the corresponding optimal braking force distribution ratio and adjustment amount; the training data is input into the neural network, forward propagation calculation is performed, and back propagation is performed to update the network weights and bias according to the mean square error between the calculation result and the true result, and iteration is repeated until the loss value is less than a first preset value.

9. The vehicle brake-by-wire method according to claim 8, characterized in that: The steps of establishing the braking force distribution matrix include: The vehicle status assessment results are divided into multiple status categories based on various possible road conditions and different driving states of the vehicle; For each state category, the braking force distribution ratio range of each wheel is preliminarily determined by combining vehicle dynamics theory and historical braking data; Using vehicle dynamics simulation software to simulate and verify the initially determined braking force distribution ratio range; adjusting the braking force distribution ratio range according to the simulation results; Conduct braking tests on different test sites according to the above different state categories and test scenarios; collect actual vehicle braking data, analyze the performance of the vehicle when braking according to the preliminary braking force distribution ratio range under different states, and adjust the braking force distribution ratio range according to the test results of the performance; The braking force distribution ratio range of each wheel under different vehicle state evaluation results determined after theoretical analysis, simulation verification and test verification is stored in a braking force distribution matrix.

10. A brake-by-wire system for an unmanned vehicle, characterized in that: include: The first processing module is used to: obtain the environment information around the vehicle and the vehicle posture information; A second processing module is used to: identify the road condition based on the environmental information and obtain the dynamic parameters of the vehicle based on the vehicle posture information and the vehicle dynamics model; A third processing module is used to: obtain a vehicle state evaluation result based on the identified road condition and the vehicle dynamic parameters; the vehicle state evaluation result is obtained based on the driving state and potential risks of the vehicle under the current road condition; A fourth processing module is used to determine the braking force distribution ratio and adjustment amount of each wheel by using a braking force distribution matrix and a braking force adjustment algorithm based on the vehicle state evaluation result; The fifth processing module is used to adjust the brake fluid pressure of each wheel based on the determined braking force distribution ratio and adjustment amount of each wheel.

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