Method and system for auxiliary emergency braking after braking failure

Abstract

Provided are a method and system for auxiliary emergency braking after a braking failure, and an electronic device, a computer-readable storage medium, a computer program product and a computer program. The method comprises: obtaining a braking system failure factor parameter numerical value on the basis of a braking system health state observer or a fault diagnosis module of a current vehicle; constructing a braking risk decision function on the basis of a braking system failure factor and related data of the current vehicle to calculate a current braking risk value, and obtaining a desired lateral displacement of the current vehicle on the basis of the current braking risk value and steering system data; constructing an integral heuristic barrier Lyapunov function on the basis of the desired lateral displacement of the vehicle and vehicle state information after decision making, and obtaining a desired vehicle traveling yaw angle on the basis of a calculation result of the function; and converting the desired vehicle traveling yaw angle into an input front wheel steering angle value of the current vehicle, and converting the input front wheel steering angle value of the current vehicle into steering-assist electric motor output data, so that a steering system intervenes in and controls safe braking after a braking process fails.

Description

Auxiliary emergency braking method and system after brake failure

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to Chinese Patent Application No. 2023113036725 filed in China on October 9, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of vehicle safety control after vehicle failure, and in particular to a method and system for assisting emergency braking after brake failure, an electronic device, a computer-readable storage medium, a computer program product, and a computer program. Background Art

[0004] With the development of artificial intelligence (AI) technology, smart cars will play an indispensable role in future urban transportation. At the same time, their widespread adoption also places higher demands on driving safety. In particular, as the number of subsystems increases, the risk of system failure increases dramatically. Improving the functional safety of smart cars after failure is a pressing issue.

[0005] A crucial feature in a vehicle's active safety system is emergency braking. Typically, this system relies on the vehicle's brake-by-wire system, which consists of a master cylinder, four wheel cylinders, and the necessary hydraulic control valves. Upon detecting an obstacle or other vehicle ahead, the emergency braking system activates and rapidly builds master cylinder pressure. Hydraulic control valves then adjust the wheel braking force to bring the vehicle to an emergency stop. During this time, the vehicle's ABS system activates to prevent tire lock during emergency braking, ensuring safety during the braking process.

[0006] The development of intelligent vehicle emergency braking functions and systems, a crucial component of autonomous driving active safety technology, plays a significant role in ensuring vehicle safety. According to China News Network, on-board emergency braking modules have effectively reduced rear-end collisions by 27%. Therefore, ensuring the correct implementation of the emergency braking (AEB) function is crucial for improving vehicle safety. However, the AEB function relies on the collaboration of numerous subsystems and components. After prolonged operation, failures are very likely to occur, jeopardizing vehicle driving safety. Consequently, many patents focus on safety control after brake system failure. For example, CN 104442410 A proposes an emergency braking system solution that includes a redundant second braking system. By triggering the emergency brake button by the driver, the vehicle controller controls the drive motor to a maximum torque generation state, generating additional braking force. However, motor feedback braking torque is often constrained by factors such as motor torque output limits and the battery pack's state of charge (SOC), making it difficult to generate sufficient braking torque in a timely manner. Therefore, patent CN 115195688 A proposes an auxiliary brake device for vehicle braking failure. By introducing an independently controlled secondary braking system, the secondary auxiliary brake device activates upon failure of the vehicle's main brake system, ensuring emergency braking. However, this approach fails to address the fault tolerance issue in the event of a high-voltage source failure. If the master cylinder high-voltage source fails, the secondary auxiliary brake device will not function successfully. Cost sensitivity and vehicle space limitations make hardware-based redundant fault-tolerance solutions difficult to implement. Therefore, post-failure control methods based on fault-tolerant control algorithms have been widely developed. Current research on brake failure primarily focuses on pre-failure redundancy, failure diagnosis, and post-failure control. Fault-tolerant algorithms enable four-wheel braking force redistribution, ensuring stable vehicle operation. However, this approach cannot address system-level failures, such as master cylinder leakage and power-assisted motor failure. When the braking system degrades, the vehicle's longitudinal braking distance increases significantly, and brake force redistribution is difficult to resolve. By integrating the steering system and replanning and making decisions after a vehicle failure, this problem can be addressed. Patent CN 115230687A proposes a drift obstacle avoidance technology approach. This approach uses the vehicle's brake failure level to determine the longitudinal collision risk in the vehicle's current state. A reinforcement learning algorithm is then used to design a control strategy for the vehicle at the current failure level, controlling wheel-end braking force and utilizing lateral force to achieve rapid braking and collision avoidance. This approach collaborates between autonomous driving and chassis-domain actuators, ensuring braking safety through the introduction of a steering system. This approach effectively improves the intelligent vehicle's emergency response and backup capabilities for brake failures. However, this approach lacks consideration of the algorithm's transient time constraints, and the use of numerous optimization algorithms places high demands on computing resources.

[0007] Summary of the Invention

[0008] The present disclosure aims to solve one of the technical problems in the related art at least to a certain extent.

[0009] To this end, the present disclosure proposes a method for assisting emergency braking after brake failure, which can improve the active safety of the vehicle, effectively reduce the occurrence of rear-end collision accidents, and has high practicality.

[0010] Another object of the present disclosure is to provide a post-brake failure auxiliary emergency braking system, an electronic device, a computer-readable storage medium, a computer program product, and a computer program.

[0011] To achieve the above objectives, a first embodiment of the present disclosure provides a method for assisting emergency braking after brake failure, comprising:

[0012] Obtaining a brake system failure factor based on a diagnosis result of the current vehicle's brake system health status;

[0013] constructing a braking risk decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate a current emergency braking risk value, and obtaining a current expected lateral displacement of the vehicle based on the current emergency braking risk value and the steering system data (decision data);

[0014] Obtaining a desired vehicle yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the desired lateral displacement of the current vehicle and the second operating state information of the vehicle;

[0015] The desired vehicle yaw angle is converted into the current vehicle input front wheel steering angle value or differential torque output value through the vehicle yaw angle controller, and the current vehicle input front wheel steering angle value is converted into the steering power motor output data, or the differential torque output value is converted into the specific wheel-side braking / driving force distribution value, so as to realize the intervention control of the active steering system or the direct yaw torque control system for safe braking after the braking process fails.

[0016] It is worth noting that in this disclosure, the reference trajectory we plan and obtain uses the vehicle's desired yaw angle information as the planning output rather than path and speed information. The benefit of this design is that it reduces the output dimension required for the system to track to one dimension. For vehicles without differential braking or cooperative control capabilities, our method effectively avoids the mismatch between the system's input and output dimensions, effectively solving the under-actuation problem.

[0017] In addition, the auxiliary emergency braking method after brake failure according to the above embodiment of the present disclosure may also have the following additional technical features:

[0018] In one embodiment of the present disclosure, the first operating status information of the vehicle includes the relative speed, relative distance, preset diagnostic time and actuator cold start time interval between the current vehicle and the preceding vehicle; the second operating status information of the vehicle includes the surrounding obstacle information of the current vehicle and the key operating status information of the vehicle in the autonomous driving layer sensing system.

[0019] In one embodiment of the present disclosure, the braking risk decision function is expressed as:

[0020] where exp(·) is an exponential function with the exponential term a>0, variables TTS and TTC are key time-domain collision safety indicators, parameter eps is the designer-adjustable threshold, parameter ρ is the degree of brake system failure, and parameter τ is the actuator and system cold start time.

[0021] In one embodiment of the present disclosure, the expression of the integral heuristic barrier Lyapunov function is:

[0022] Construct a collision risk function with an obstacle:

[0023] Among them, parameter A f is the function amplitude, the exponential term b>0, the variables X and Y are the real-time longitudinal and lateral positions of the vehicle, and the variable X o ,Y o is the longitudinal and lateral position of an obstacle, and the parameter μ is the detection distance limit of the vehicle sensor;

[0024] According to the collision risk function, a safety barrier function is constructed:

[0025] The parameter r is the limit collision safety distance, and the function ln(·) is a logarithmic function with the natural function as the base.

[0026] In one embodiment of the present disclosure, the integral heuristic barrier Lyapunov function may be constructed based on the safety barrier function:

[0027] Among them, Y e is the vehicle lateral displacement error.

[0028] In one embodiment of the present disclosure, a continuous time-domain error transformation function is constructed:

[0029] Among them, the function parameter T is the upper bound of the transient time constraint, the parameter ∈ is the adjustable initial value parameter, and the exponential term n>0;

[0030] Based on the continuous time domain transformation function and the integral heuristic barrier Lyapunov function, the desired vehicle yaw angle is calculated:

[0031] Among them, v x is the longitudinal velocity of the vehicle, β is the sideslip angle of the vehicle center of mass, which is obtained by the vehicle speed sensor, and the parameter b>0 is an adjustable parameter of the controller. The function The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

[0032] To achieve the above objectives, a second embodiment of the present disclosure provides an auxiliary emergency braking system after brake failure, comprising:

[0033] A failure factor acquisition module obtains a brake system failure factor based on a diagnosis result of the current vehicle's brake system health status;

[0034] an expected displacement calculation module, which constructs a braking risk decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate a current braking risk value, and obtains a current expected lateral displacement of the vehicle based on the current braking risk value and steering system data;

[0035] an expected yaw angle calculation module, which obtains an expected vehicle yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the current expected lateral displacement of the vehicle and the second operating state information of the vehicle;

[0036] The emergency braking control module converts the desired vehicle yaw angle into the current vehicle input front wheel steering angle value or differential torque output value through the vehicle yaw angle controller, and converts the current vehicle input front wheel steering angle value into the output data of the power steering motor, or converts the differential torque output value into the specific distribution value of wheel-side braking / driving force, so as to realize the intervention control of the active steering system or the direct yaw torque control system for safe braking after the braking process fails.

[0037] To achieve the above-mentioned purpose, an embodiment of the third aspect of the present disclosure provides an electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect above when executing the computer program.

[0038] To achieve the above-mentioned purpose, an embodiment of the fourth aspect of the present disclosure provides a computer-readable storage medium, which stores computer instructions, and is characterized in that the computer instructions are used to enable the computer to execute the auxiliary emergency braking method after brake failure as described in any embodiment of the first aspect above.

[0039] To achieve the above-mentioned purpose, an embodiment of the fifth aspect of the present disclosure provides a computer program product, including a computer program, which, when executed by a processor, is used to implement the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect of the present disclosure.

[0040] To achieve the above-mentioned purpose, an embodiment of the sixth aspect of the present disclosure provides a computer program, including computer program code, which, when the computer program code is run on a computer, enables the computer to execute the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect of the present disclosure.

[0041] The auxiliary emergency braking method and system after brake failure, electronic equipment, computer-readable storage medium, computer program product and computer program of the embodiments of the present disclosure can effectively improve the active safety of the vehicle. The analytical nature of the algorithm makes the algorithm computationally low in cost and easy to implement on a vehicle, and has great engineering application value.

[0042] The beneficial effects of the present disclosure are:

[0043] 1) This disclosed embodiment proposes a new safe, fault-tolerant braking strategy with steering intervention, enabling steering-brake override for emergency braking in the event of a brake system failure. By leveraging three key processes: post-failure decision-making, re-motion planning, and precise tracking control, lateral force is introduced to maneuver the vehicle to a safe position before a rear-end collision occurs, ensuring the safety of emergency braking.

[0044] 2) To meet the requirements for the algorithm's transient convergence time in emergency braking scenarios, this method designs a time-domain constraint function with a preset convergence time to constrain the algorithm's transient convergence time and ensure that the vehicle reaches a safe decision-making position before coming to a complete stop.

[0045] 3) Compared with the widely used model predictive control algorithm, the method of the embodiment of the present disclosure is easy to program and requires less computing power, which is conducive to application in actual vehicles.

[0046] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and / or additional aspects and advantages of the present disclosure will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0048] FIG1 is a flow chart of a method for assisting emergency braking after brake failure according to an embodiment of the present disclosure;

[0049] FIG2 is a structural diagram of a method for assisting emergency braking after brake failure according to an embodiment of the present disclosure;

[0050] FIG3 is a diagram of an emergency braking scenario of an autonomous vehicle in an urban environment according to an embodiment of the present disclosure;

[0051] FIG4 is a schematic structural diagram of a system for assisting emergency braking after brake failure according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0052] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in the present disclosure can be combined with each other. The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0053] In order to enable those skilled in the art to better understand the embodiments of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present disclosure.

[0054] The following describes a method and system for assisting emergency braking after brake failure, an electronic device, a computer-readable storage medium, a computer program product, and a computer program according to embodiments of the present disclosure with reference to the accompanying drawings.

[0055] FIG1 is a flow chart of a method for assisting emergency braking after brake failure according to an embodiment of the present disclosure.

[0056] As shown in FIG1 , the method includes but is not limited to steps S1 to S4 .

[0057] S1, obtaining a brake system failure factor based on a diagnosis result or observation result of a current vehicle brake system health status.

[0058] S2, constructing a braking risk decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate a current braking risk value, and obtaining a current expected lateral displacement of the vehicle according to the current braking risk value and the steering system data.

[0059] S3, obtaining a desired vehicle yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the current desired vehicle lateral displacement and the second operating state information of the vehicle.

[0060] S4, converting the desired vehicle yaw angle into the current vehicle input front wheel steering angle value or differential torque output value through the vehicle yaw angle controller, and converting the current vehicle input front wheel steering angle value into the output data of the power steering motor, or converting the differential torque output value into the specific distribution value of the wheel-side braking / driving force, so as to realize the intervention control of the active steering system or the direct yaw torque control system for safe braking after the braking process fails.

[0061] According to the method for assisting emergency braking after brake failure according to the embodiment of the present disclosure, by providing information perception of the vehicle's surroundings and global trajectory planning based on the set mission objectives, a safety function is constructed and the value of the obstacle function is determined based on the mission reference trajectory and the geometric information of the surrounding obstacle positions. The autonomous collision avoidance system directly obtains the response of the desired actuator through the obstacle function, and executes the desired response through the chassis execution system, thereby achieving the purpose of accurately tracking the set reference trajectory and correcting the trajectory in real time to avoid collisions. The autonomous collision avoidance system achieves the fusion of desired trajectory tracking and active collision avoidance functions by introducing the heuristic obstacle Lyapunov function and analyzing the rows of the expression. The embodiment of the present disclosure improves the active safety of the vehicle, effectively reduces the occurrence of rear-end collision accidents, and has high practicality.

[0062] The auxiliary emergency braking method after brake failure according to an embodiment of the present disclosure is described in detail below with reference to the accompanying drawings.

[0063] As shown in FIG2 , it is a framework diagram of the auxiliary emergency braking method after brake failure according to an embodiment of the present disclosure.

[0064] In one embodiment of the present disclosure, as shown in module 1 in Figure 2, the vehicle triggers the AEB function based on the relative distance from the vehicle in front, and the vehicle enters the emergency braking state. At the same time, to ensure the safety of the deceleration and braking process and prevent the occurrence of wheel locking, the vehicle's ABS emergency anti-lock braking system operates normally, controlling the wheel slip rate through braking force to prevent wheel locking during the vehicle braking process and ensure that the wheels still have redundant lateral force, providing the possibility for subsequent steering system intervention;

[0065] In one embodiment of the present disclosure, as shown in Module 2 in Figure 2, this module is primarily responsible for assessing vehicle safety risks following brake system failure during emergency braking. This module collects the current health status of the vehicle's brake system and obtains the brake system failure factor. Based on the current relative speed and distance between the front and rear vehicles, as well as the expected actuator cold start interval, it calculates and assesses the current braking risk value, determines whether steering system intervention is necessary, and dynamically calculates the vehicle's desired longitudinal position based on the risk value.

[0066] In one embodiment of the present disclosure, as shown in module 31 in module 3 in FIG2 , based on the desired longitudinal position of the vehicle, the vehicle-mounted sensors in module 4 collect information on obstacles in the surrounding environment and key operating status information of the vehicle, construct a safety obstacle function, and thereby design a heuristic obstacle Lyapunov function, thereby converting the complex motion planning problem into a simple yaw angle tracking problem.

[0067] In one embodiment of the present disclosure, as shown in module 32 of module 3 in FIG. 2 , the desired yaw angle is converted into a vehicle input front wheel steering angle value and an additional yaw moment value through the vehicle's existing yaw rate tracking algorithm.

[0068] In one embodiment of the present disclosure, as shown in module 4 in FIG2 , the vehicle front wheel angle is converted into the output of the power steering motor through a precise tracking control algorithm of the vehicle steering mechanism and a tire inverse model, thereby enabling the steering system to intervene in safe braking after the braking process fails.

[0069] In one embodiment of the present disclosure, the vehicle's emergency braking AEB function will be triggered normally, and the ABS function will be triggered auxiliaryly to ensure that the vehicle does not experience wheel locking during braking;

[0070] In one embodiment of the present disclosure, module 2 is primarily responsible for assessing and determining the risk of emergency braking after the current braking system fails, and obtaining an adjusted expected lateral displacement of the vehicle. The normalized braking risk decision function can be defined as:

[0071] Wherein, the function exp(·) is an exponential function, the exponential term a>0, the variables TTS and TTC are key collision time-domain safety indicators, and their definitions can be obtained in the automobile collision safety specification standards; the parameter eps is an adjustable threshold value used to ensure that the vehicle steering operation is maintained after activation, and the threshold value can reflect the degree of maintenance of the steering intervention; the parameter ρ is the degree of failure of the braking system, and the parameter τ is the actuator and system cold start time. During this time, the vehicle will still execute the predetermined braking command. The above braking risk decision function can be freely defined by the designer, and this embodiment is only a reference. Through this decision function, the expected lateral displacement of the vehicle can be expressed as Y d =w road α, where the parameter w road The width of the road.

[0072] In one embodiment of the present disclosure, the module 3 is primarily responsible for achieving the desired lateral displacement of the vehicle in module 2. In the process of reaching the desired lateral displacement, the target position and potential obstacles in the trajectory must be considered. Without loss of generality, the safety function is designed as follows:

[0073] Among them, parameter A f is the function amplitude, the exponential term b>0, the variables X and Y are the real-time longitudinal and lateral positions of the vehicle, and the variable X o ,Y o is the longitudinal and lateral position of an obstacle, and the parameter μ is the detection range limit of the vehicle's sensors. When other obstacles are present, the safety function can be expressed as the sum of the safety function values ​​of the ego vehicle and each obstacle. It is worth noting that this safety function can be designed by the user as long as it satisfies positive definiteness.

[0074] According to the above collision risk function, a safety barrier function is designed as follows:

[0075] Where r is the limit collision safety distance. The function ln(·) is a logarithmic function. Similarly, the safety barrier function in this embodiment can be freely defined by the designer, as long as it meets the positive definite requirement. Based on this safety barrier function, the following integral-inspired barrier Lyapunov function can be designed:

[0076] Where Y e is the vehicle's lateral displacement error. Considering that the entire safety braking strategy requires the vehicle to reach the desired lateral position before coming to a complete stop, the algorithm's transient execution time has a definite upper bound. To ensure that the transient process of the auxiliary braking algorithm designed in this embodiment meets the time domain constraints, a continuous time domain error transformation function is introduced:

[0077] Among them, the function parameter T is the upper bound of the transient time constraint, and the parameter ∈ is an adjustable initial value parameter whose value satisfies The exponential term n>0 can be used. Through this function, combined with the above-mentioned integral heuristic barrier Lyapunov function, the expected value of the vehicle yaw angle for the re-planning of the safety auxiliary braking algorithm can be obtained as:

[0078] Among them, v x is the vehicle longitudinal velocity, which can be measured by the vehicle speed sensor; β is the vehicle side slip angle, which can be obtained by the vehicle sensor or existing estimation method. The parameter b>0 is the controller parameter, and the function The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

[0079] It is worth noting that, unlike existing fault-tolerant planning techniques, the implementation of the auxiliary safety braking function in the disclosed embodiment does not involve replanning to obtain a new reference trajectory. Instead, it directly obtains the desired yaw angle of the vehicle, which is integrated with the collision avoidance function. This allows the integration of this fault-tolerant safety function into the vehicle chassis motion control layer to be more conveniently integrated, effectively improving the intelligence of chassis motion control and reducing the chassis's demand for computing power at the autonomous driving layer. Furthermore, compared to traditional optimization-based planning and control methods, the method in the disclosed embodiment explicitly expresses the algorithm's time constraints in the algorithm controller design, using hard constraints to implement time constraints on its transient motion processes, optimizing the intermediate driving process, and improving the algorithm's feasibility in emergency braking scenarios.

[0080] Finally, relying on an existing desired yaw angle tracking algorithm, the desired yaw angle is converted and assigned to the desired response value of the vehicle chassis actuator. Without loss of generality, this embodiment is applicable to front-wheel drive, rear-wheel drive, and all-wheel drive vehicles. The differences primarily lie in the conversion and tracking of the desired yaw angle to the underlying actuator response for different chassis architectures. Furthermore, differential braking can be additionally introduced to enhance the vehicle's lateral motion capability and expand the ability to intervene in steering during safe braking. The design method primarily involves adding an additional yaw torque input to the vehicle's desired yaw angle tracking algorithm, which can be implemented using existing coordinated control algorithms.

[0081] In some embodiments, as shown in FIG3 , the embodiment of the present disclosure takes the emergency braking scenario of an autonomous vehicle under urban conditions as an example. During the implementation of emergency braking, the vehicle suddenly encounters a partial failure of the braking system, and the vehicle's braking ability cannot be restored by simply redistributing the wheel-end braking force. Therefore, starting the active assisted emergency collision avoidance function is of great significance to ensuring vehicle safety. The auxiliary safety braking algorithm designed by the embodiment of the present disclosure can effectively improve the active fault tolerance safety of the vehicle. The expectation of this embodiment is to re-decide and plan the vehicle's operating trajectory target when the braking system is degraded, and through the intervention of the steering system, change lanes to a safe position and stop the vehicle. During this period, the AEB system remains in operation and the vehicle remains in an emergency braking state.

[0082] In summary, after the AEB system activates and the brake system fails, Module 1 of the disclosed embodiment first calculates the risk of the vehicle continuing its original braking operation based on the degree of brake system failure and the risk assessment index of rear-end collision with the preceding vehicle, and dynamically adjusts the vehicle's braking target. Module 2 then designs a heuristic barrier Lyapunov function based on the vehicle's corrected lateral displacement after braking in Module 1. This heuristic Lyapunov function converts the desired lateral displacement into the desired vehicle yaw angle. Module 3 achieves precise yaw angle tracking based on the chassis system configuration, converting the desired yaw angle into a chassis front wheel angle response value and differential braking torque. Finally, Module 4 calculates the steering motor torque and wheel-side braking force using existing steer-by-wire system control algorithms and brake force distribution algorithms, enabling steering system intervention and auxiliary safety braking functions after partial brake system failure.

[0083] According to the disclosed embodiment of the brake failure assisted emergency braking method, when the emergency braking function is triggered, the vehicle's rear-end collision risk is first determined based on the current degree of brake system failure. This determines the vehicle's desired lateral displacement and determines whether steering intervention is required. To safely achieve this desired lateral displacement, a risk assessment function and a heuristic barrier Lyapunov function are designed to directly determine the desired yaw angle of the vehicle, integrated with the active collision avoidance function. The vehicle's motion trajectory is then converted into a desired yaw angle. This yaw angle is then converted into the vehicle's front wheel steering angle through a tracking control algorithm. Finally, through precise control of the chassis subsystem, the front wheel steering angle is converted into the steering system's power assist motor torque, ensuring the safety of the emergency braking function. This method, under the emergency braking function, decomposes the longitudinal driving risk of the vehicle after brake failure into the lateral dimension by introducing lateral forces and the steering system, thereby reducing driving risk. Furthermore, to address the limited transient time in emergency braking conditions, a time-constrained transformation function is designed. By pre-setting temporal stability characteristics, this ensures that the vehicle successfully reaches the desired position before braking is completed. The disclosed embodiments can effectively improve vehicle active safety. The analytical nature of the algorithm makes the algorithm computationally inexpensive and easy to implement on a vehicle, thus having great engineering application value.

[0084] In order to implement the above embodiment, as shown in Figure 4, this embodiment also provides an auxiliary emergency braking system 10 after brake failure. The system 10 includes a failure factor acquisition module 100, an expected displacement calculation module 200, an expected yaw angle calculation module 300 and an emergency braking control module 400.

[0085] A failure factor acquisition module 100 obtains a brake system failure factor based on a diagnosis result of a current vehicle brake system health status;

[0086] The expected displacement calculation module 200 constructs a braking risk decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate the current braking risk value, and obtains the current expected lateral displacement of the vehicle based on the current braking risk value and the steering system data;

[0087] The desired yaw angle calculation module 300 obtains a desired vehicle yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the current desired lateral displacement of the vehicle and the second operating state information of the vehicle;

[0088] The emergency braking control module 400 converts the desired vehicle yaw angle into the current vehicle input front wheel steering angle value or differential torque output value through the vehicle yaw angle controller, and converts the current vehicle input front wheel steering angle value into the output data of the power steering motor, or converts the differential torque output value into the specific distribution value of the wheel-side braking / driving force, so as to realize the intervention control of the steering system for safe braking after the braking process fails.

[0089] In some embodiments, the first operating status information includes the relative speed, relative distance, preset diagnostic time, and actuator cold start time interval between the current vehicle and the preceding vehicle; the second operating status information includes the surrounding obstacle information of the current vehicle and the key operating status information of the vehicle in the autonomous driving layer sensing system.

[0090] In some embodiments, the braking risk auxiliary decision function is expressed as:

[0091] where exp(·) is an exponential function with the exponential term a>0, variables TTS and TTC are key time-domain collision safety indicators, parameter eps is the designer-adjustable threshold, parameter ρ is the degree of brake system failure, and parameter τ is the actuator and system cold start time.

[0092] In some embodiments, the integral heuristic barrier Lyapunov function is expressed as:

[0093] Construct a collision risk function:

[0094] Among them, parameter A f is the function amplitude, the exponential term b>0, the variables X and Y are the real-time longitudinal and lateral positions of the vehicle, and the variable X o ,Y o is the longitudinal and lateral position of an obstacle, and the parameter μ is the detection distance limit of the vehicle sensor;

[0095] According to the collision risk function, a safety barrier function is constructed:

[0096] Among them, the parameter r is the limit collision safety distance, and the function ln(·) is a logarithmic function with the natural function as the base;

[0097] According to the safety barrier function, an integral heuristic barrier Lyapunov function is constructed:

[0098] Among them, Y e is the vehicle lateral displacement error.

[0099] In some embodiments, a continuous time-domain error transform function is constructed:

[0100] Among them, the function parameter T is the upper bound of the transient time constraint, the parameter ∈ is the adjustable initial value parameter, and the exponential term n>0;

[0101] Based on the continuous time-domain error transfer function and the integral heuristic barrier Lyapunov function, the desired vehicle yaw angle is calculated:

[0102] Among them, v x is the longitudinal velocity of the vehicle, β is the sideslip angle of the vehicle center of mass, which is obtained by the vehicle speed sensor, and the parameter b>0 is an adjustable parameter of the controller. The function The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

[0103] According to the auxiliary emergency braking system after brake failure of the embodiment of the present disclosure, under the condition of triggering the emergency braking function, the risk of rear-end collision of the vehicle is first judged by the current failure degree of the vehicle's brake system, and a post-failure decision is made and the desired lateral displacement of the vehicle is obtained to determine whether the steering system needs to intervene; in order to safely achieve the desired lateral displacement, a hazard assessment function and a heuristic obstacle Lyapunov function are designed, and the desired yaw angle of the vehicle integrated with the active collision avoidance function is directly obtained thereby, and the vehicle motion trajectory is converted into a desired vehicle yaw angle; through a tracking control algorithm, it is converted into the vehicle's front wheel steering angle; finally, through precise control of the chassis subsystem, the front wheel steering angle is converted into the driving torque of the steering system power assist motor to achieve the safety of the emergency braking function.

[0104] In order to implement the above embodiments, an embodiment of the third aspect of the present disclosure provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that when the processor executes the computer program, the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect above is implemented.

[0105] In order to implement the above embodiments, an embodiment of the fourth aspect of the present disclosure provides a computer-readable storage medium, which stores computer instructions, and is characterized in that the computer instructions are used to enable the computer to execute the auxiliary emergency braking method after brake failure as described in any embodiment of the first aspect above.

[0106] The computer-readable media of this embodiment include permanent and non-permanent, removable and non-removable media that can be used to store information by any method or technology. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0107] In order to implement the above embodiments, an embodiment of the fifth aspect of the present disclosure provides a computer program product, including a computer program, which, when executed by a processor, is used to implement the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect of the present disclosure.

[0108] In order to implement the above embodiments, an embodiment of the sixth aspect of the present disclosure provides a computer program, including computer program code, which, when the computer program code is run on a computer, enables the computer to execute the method for assisting emergency braking after brake failure as described in any embodiment of the first aspect of the present disclosure.

[0109] It should be noted that the aforementioned explanations of the method and system embodiments also apply to the electronic device, computer-readable storage medium, computer program product, and computer program of the above embodiments, and will not be repeated here.

[0110] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0111] Furthermore, 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 being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0112] All embodiments of the present disclosure may be implemented individually or in combination with other embodiments, and are all considered to be within the scope of protection claimed by the present disclosure.

Claims

1. A method for assisting emergency braking after brake failure, characterized in that: The following steps are involved: Obtaining a brake system failure factor based on a diagnosis result of a brake system health status of the current vehicle; constructing a braking risk auxiliary decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate a current braking risk value, and obtaining a current vehicle expected lateral displacement according to the current braking risk value and the steering system data; Obtaining a desired vehicle driving yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the desired lateral displacement of the current vehicle and the second operating state information of the vehicle; The desired vehicle driving yaw angle is converted into the current vehicle input front wheel steering angle value or differential torque output value through a vehicle yaw angle controller, and the current vehicle input front wheel steering angle value is converted into steering power motor output data, or the differential torque output value is converted into a specific wheel-side braking / driving force distribution value, so as to realize the intervention control of active steering system or direct yaw torque control system for safe braking after the braking process fails.

2. The method according to claim 1, characterized in that The first operating status information of the vehicle includes the relative speed, relative distance, preset diagnostic time and actuator cold start time interval between the current vehicle and the vehicle in front; the second operating status information of the vehicle includes the surrounding obstacle information of the current vehicle and the key operating status information of the vehicle in the self-driving layer sensing system.

3. The method according to claim 1 or 2, characterized in that: The expression of the braking risk auxiliary decision function is: Among them, the function exp(·) is an exponential function, the exponential term a>0, the variables TTS and TTC are key collision time-domain safety indicators, the parameter eps is the designer-adjustable threshold, the parameter ρ is the degree of brake system failure, and the parameter τ is the actuator and system cold start time.

4. The method according to any one of claims 1 to 3, characterized in that The expression of the integral heuristic barrier Lyapunov function is: Construct a collision risk function: Among them, parameter A f is the function amplitude, the exponential term b>0, the variables X and Y are the real-time longitudinal and lateral positions of the vehicle, and the variable X o ,Y o is the longitudinal and lateral position of a certain obstacle, and parameter μ is the detection distance limit of the vehicle sensor; According to the collision risk function, a safety barrier function is constructed: Among them, the parameter r is the limit collision safety distance, and the function ln(·) is a logarithmic function with the natural function as the base; According to the safety barrier function, the integral heuristic barrier Lyapunov function can be constructed: Among them, Y e is the vehicle lateral displacement error.

5. The method according to any one of claims 1 to 4, characterized in that Construct a continuous time-domain error transform function: Among them, the function parameter T is the upper bound of the transient time constraint, the parameter ∈ is the adjustable initial value parameter, and the exponential term n>0; Based on the continuous time-domain error transformation function and the integral heuristic barrier Lyapunov function, the desired vehicle driving yaw angle is calculated: Among them, v x is the longitudinal velocity of the vehicle, β is the sideslip angle of the vehicle center of mass, which is obtained by the vehicle speed sensor or the existing estimation algorithm, and the parameter b>0 is the adjustable parameter of the controller. The function The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

6. A brake failure auxiliary emergency braking system, characterized in that: include: A failure factor acquisition module obtains a brake system failure factor based on a diagnosis result of a brake system health status of a current vehicle; an expected displacement calculation module, which constructs a braking risk auxiliary decision function based on the braking system failure factor and the first operating state information of the vehicle to calculate a current braking risk value, and obtains a current vehicle expected lateral displacement according to the current braking risk value and the steering system data; an expected yaw angle calculation module, which obtains an expected vehicle driving yaw angle according to a function calculation result of an integral heuristic barrier Lyapunov function constructed based on the current expected lateral displacement of the vehicle and the second running state information of the vehicle; The emergency braking control module converts the desired vehicle driving yaw angle into the current vehicle input front wheel steering angle value or differential torque output value through the vehicle yaw angle controller, and converts the current vehicle input front wheel steering angle value into the output data of the power steering motor, or converts the differential torque output value into the specific distribution value of wheel-side braking / driving force, so as to realize the intervention control of the active steering system or the direct yaw torque control system for safe braking after the braking process fails.

7. The system according to claim 6, characterized in that The first operating status information of the vehicle includes the relative speed, relative distance, preset diagnostic time and actuator cold start time interval between the current vehicle and the vehicle in front; the second operating status information of the vehicle includes the surrounding obstacle information of the current vehicle and the key operating status information of the vehicle.

8. The system according to claim 6 or 7, characterized in that: The expression of the braking risk auxiliary decision function is: Among them, the function exp(·) is an exponential function, the exponential term a>0, the variables TTS and TTC are key collision time-domain safety indicators, the parameter eps is the designer-adjustable threshold, the parameter ρ is the degree of brake system failure, and the parameter τ is the actuator and system cold start time.

9. The system according to any one of claims 6 to 8, characterized in that The expression of the integral heuristic barrier Lyapunov function is: Construct a collision risk function: Among them, parameter A f is the function amplitude, the exponential term b>0, the variables X and Y are the real-time longitudinal and lateral positions of the vehicle, and the variable X o ,Y o is the longitudinal and lateral position of a certain obstacle, and parameter μ is the detection distance limit of the vehicle sensor; According to the collision risk function, a safety barrier function is constructed: Among them, the parameter r is the limit collision safety distance, and the function ln(·) is a logarithmic function with the natural function as the base; According to the safety barrier function, the integral heuristic barrier Lyapunov function can be constructed: Among them, Y e is the vehicle lateral displacement error.

10. The system according to any one of claims 6 to 9, characterized in that Construct a continuous time-domain error transform function: Among them, the function parameter T is the upper bound of the transient time constraint, the parameter ∈ is the adjustable initial value parameter, and the exponential term n>0; Based on the continuous time-domain error transformation function and the integral heuristic barrier Lyapunov function, the desired vehicle driving yaw angle is calculated: Among them, v x is the longitudinal velocity of the vehicle, β is the sideslip angle of the vehicle center of mass, obtained by the vehicle speed sensor, and the parameter b>0 is an adjustable parameter of the controller. The function The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method for assisting emergency braking after brake failure according to any one of claims 1 to 5 is implemented.

12. A computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to enable the computer to execute the post-brake failure auxiliary emergency braking method according to any one of claims 1 to 5. 13 . A computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements the post-brake failure auxiliary emergency braking method according to any one of claims 1 to 5.

14. A computer program, characterized in that The computer program comprises computer program codes, and when the computer program codes are run on a computer, the computer is enabled to execute the post-brake failure auxiliary emergency braking method according to any one of claims 1 to 5.

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