Auxiliary emergency braking method and system after brake failure

Abstract

The present invention discloses a method and system for assisting emergency braking after brake failure, the method comprising: obtaining a brake system failure factor parameter value based on a brake system health state observer or a fault diagnosis module of the current vehicle; constructing a brake risk decision function based on the brake system failure factor and current vehicle related data to calculate the current brake risk value, and obtaining the current vehicle expected lateral displacement according to the current brake risk value and steering system data; constructing an integral heuristic barrier Lyapunov function based on the vehicle expected lateral displacement after decision and vehicle state information, and obtaining the expected vehicle driving yaw angle according to the function calculation result; converting it into the current vehicle input front wheel steering angle value, and converting the current vehicle input front wheel steering angle value into the output data of the steering power motor, so as to realize the intervention control of the steering system on safe braking after the brake process fails. The present invention realizes the emergency braking function under the brake system failure scenario, and ensures the safety of emergency braking.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle safety control after failure, and in particular to a method and system for auxiliary emergency braking after brake failure. Background Art

[0002] With the development of artificial intelligence technology, smart cars will play an indispensable role in future urban transportation. At the same time, the popularity of smart cars has also put forward higher requirements for their driving safety. In particular, as the number of subsystems increases, the risk of system failure increases sharply. How to improve the functional safety of smart driving cars after failure is an urgent problem to be solved.

[0003] A crucial function in the vehicle's active safety system is the emergency braking function. Generally speaking, the vehicle's emergency braking system relies on the intervention of the vehicle's wire control brake system, which consists of a master cylinder, four wheel cylinders and necessary hydraulic control valves. In response to obstacles or other vehicle information detected in front of the vehicle, the vehicle's emergency braking function is triggered and activated, and the master cylinder pressure is quickly built up. The wheel side braking force is adjusted through the hydraulic control valve to achieve the vehicle's emergency parking function. During this period, the vehicle's ABS function is triggered to prevent the vehicle's emergency braking tires from locking and ensure the safety of the braking process.

[0004] As an important part of the active safety technology of autonomous driving, the research and development of the emergency braking function and system of smart cars has played a huge role in ensuring vehicle safety. According to statistics from China News Network, the on-board emergency braking module effectively reduced the occurrence of rear-end collisions by 27%. Therefore, ensuring the correct implementation of the emergency braking (AEB) function is an important part of improving vehicle safety. However, the AEB function relies on the cooperation of many subsystems and components. After working for a long time, failure problems are very likely to occur, endangering the driving safety of the vehicle. Therefore, many patents focus on safety control after the failure of the braking system. For example, CN 104442410 A proposes an emergency braking system solution including a redundant second braking system. The driver triggers the emergency brake button, so that the vehicle controller controls the drive motor to be in the maximum torque power generation state to generate additional braking force. However, the motor feedback braking torque is often constrained by the motor torque output limit, the charging SOC value of the rechargeable battery pack, etc., and it is difficult to generate sufficient braking torque in time; therefore, patent CN 115195688 A designs an auxiliary brake device for vehicle driving brake failure. By introducing an independently controlled second brake system, the second auxiliary brake device is activated after the vehicle main brake device fails to ensure the vehicle's emergency braking capability. However, this method cannot solve the fault tolerance problem in the scenario of high-voltage source failure. When the master cylinder high-voltage source fails, the second auxiliary brake device cannot operate successfully. If a redundant master cylinder high-voltage source is arranged, the cost sensitivity and the limitation of the vehicle space make it difficult to implement a hardware-based redundant fault-tolerant solution. Therefore, a post-failure control method based on a fault-tolerant control algorithm is widely designed. At present, the research on brake failure mainly focuses on pre-failure redundancy, failure diagnosis, and post-failure control. The four-wheel braking force is redistributed through a fault-tolerant algorithm to ensure stable vehicle operation. However, this type of method cannot solve system-level faults, such as master cylinder leakage, power motor failure, etc. When the braking system is degraded, the longitudinal braking distance of the vehicle increases significantly, and it is difficult to solve this type of problem by redistributing the braking force. This type of problem can be solved by introducing the coordination of the steering system and replanning and making decisions after the vehicle fails. Patent CN 115230687A proposes a technical route for drift obstacle avoidance. The longitudinal collision risk of the vehicle in the current state is obtained by the vehicle braking failure level, and the control strategy of the vehicle with the current failure level is designed by the reinforcement learning algorithm to control the wheel-end braking force and use the lateral force to complete rapid braking and collision avoidance operations. This method collaborates with the actuators in the self-driving domain and the chassis domain, and ensures braking safety by introducing the steering system. This method effectively improves the emergency response capability and backup level of intelligent vehicles for brake failure. However, this method still lacks consideration for the transient time constraints of the algorithm. At the same time, the use of a large number of optimization solution algorithms makes the algorithm have a high demand for computing power resources. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the present invention proposes a method for auxiliary 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.

[0007] Another object of the present invention is to provide an auxiliary emergency braking system after brake failure.

[0008] To achieve the above object, the present invention provides, on one hand, a method for assisting emergency braking after brake failure, comprising:

[0009] Obtaining a brake system failure factor based on a diagnosis result of a brake system health status of the current vehicle;

[0010] Based on the braking system failure factor and the first operating state information of the vehicle, a braking risk decision function is constructed to calculate a current emergency braking risk value, and a current vehicle expected lateral displacement is obtained according to the current emergency braking risk value and the steering system data (decision data);

[0011] 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;

[0012] The desired vehicle driving 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 output data of the power steering motor, or the differential torque output value is converted 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.

[0013] It is worth noting that in the present invention, the reference trajectory we plan and obtain uses the vehicle's expected yaw angle information rather than the path and speed information as the planning output. The benefit of this design is that the output dimension that the system needs to track is reduced to one dimension. For vehicles without differential braking or cooperative control capabilities, our method effectively avoids the mismatch problem of the system's input and output dimensions and effectively solves the under-actuation problem.

[0014] In addition, the auxiliary emergency braking method after brake failure according to the above embodiment of the present invention may also have the following additional technical features:

[0015] Furthermore, in one embodiment of the present invention, 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 self-driving layer sensing system.

[0016] Furthermore, in one embodiment of the present invention, the braking risk decision function is expressed as:

[0017]

[0018] 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.

[0019] Furthermore, in one embodiment of the present invention, the expression of the integral heuristic barrier Lyapunov function is:

[0020] Construct a collision risk function with an obstacle:

[0021]

[0022] 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;

[0023] According to the collision risk function, a safety barrier function is constructed:

[0024]

[0025] 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;

[0026] Furthermore, in one embodiment of the present invention, an integral heuristic barrier Lyapunov function may be constructed according to the safety barrier function:

[0027]

[0028] Among them, Y e is the vehicle lateral displacement error.

[0029] Furthermore, in one embodiment of the present invention, a continuous time domain error transformation function is constructed:

[0030]

[0031] 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;

[0032] Based on the continuous time domain transformation function and the integral heuristic barrier Lyapunov function, the desired vehicle yaw angle is calculated:

[0033]

[0034] 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, parameter b>0 is the adjustable parameter of the controller, and function Φ T1 The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

[0035] To achieve the above object, the present invention provides, on the other hand, a brake failure auxiliary emergency braking system, comprising:

[0036] 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;

[0037] 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 vehicle expected lateral displacement according to the current braking risk value and the steering system data;

[0038] 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;

[0039] 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.

[0040] The auxiliary emergency braking method and system after brake failure of the embodiment of the present invention can effectively improve the active safety of the vehicle. The analytical nature of the algorithm makes the algorithm computationally inexpensive and easy to implement on a vehicle, and has great engineering application value.

[0041] The beneficial effects of the present invention are:

[0042] 1) The present invention proposes a new safe fault-tolerant braking strategy for steering intervention, which realizes the emergency braking function of steering-brake write-through in the scenario of brake system failure. Through the three important links of post-failure re-decision-making, re-motion planning and precise tracking control, after the brake system fails and before the rear-end collision occurs, lateral force is introduced to move the vehicle to a safe position to ensure the safety of emergency braking;

[0043] 2) In order to meet the requirements of the algorithm's transient convergence time in emergency braking scenarios, this method designs a time-domain constraint function with a preset time convergence to constrain the algorithm's transient convergence time and ensure that the vehicle runs to a safe decision-making position before stopping;

[0044] 3) Compared with the widely used model predictive control algorithm, the method of the present invention is easy to program and requires less computing power, which is conducive to application in actual vehicles.

[0045] Additional aspects and advantages of the present invention 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 invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0047] Figure 1 is a flow chart of a method for assisting emergency braking after brake failure according to an embodiment of the present invention;

[0048] Figure 2 is a structural diagram of a method for assisting emergency braking after brake failure according to an embodiment of the present invention;

[0049] Figure 3 is a diagram of an emergency braking scenario of an autonomous driving vehicle in an urban working condition according to an embodiment of the present invention;

[0050] Figure 4 4 is a schematic structural diagram of a system for assisting emergency braking after brake failure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0053] The following describes a method and system for assisting emergency braking after brake failure according to an embodiment of the present invention with reference to the accompanying drawings.

[0054] Figure 1 It is a flow chart of a method for assisting emergency braking after brake failure according to an embodiment of the present invention.

[0055] like Figure 1 As shown, the method includes but is not limited to the following steps:

[0056] S1, obtaining a brake system failure factor based on a diagnosis result or an observation result of a brake system health status of the current vehicle;

[0057] 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 vehicle expected lateral displacement according to the current braking risk value and the steering system data;

[0058] S3, obtaining a desired vehicle driving 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;

[0059] S4, converting 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 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.

[0060] According to the method for assisting emergency braking after brake failure of an embodiment of the present invention, by providing vehicle surrounding information perception and global trajectory planning according to the set mission objectives, a safety function is constructed and the obstacle function value is determined according to 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 collision. The autonomous collision avoidance system realizes the integration of the desired trajectory tracking and active collision avoidance functions by introducing the heuristic obstacle Lyapunov function and analyzing the row form of the expression. The present invention improves the active safety of the vehicle, effectively reduces the occurrence of rear-end collision accidents, and has high practicality.

[0061] The auxiliary emergency braking method after brake failure according to an embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0062] like Figure 2 FIG. 1 is a framework diagram of a method for assisting emergency braking after brake failure according to an embodiment of the present invention. Figure 2 As shown:

[0063] In one embodiment of the present invention, Figure 2 As shown in module 1, the vehicle triggers the AEB function according to the relative distance from the vehicle in front, and the vehicle enters the emergency braking state. At the same time, in order 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, controls the wheel slip rate through the braking force, prevents the wheel from locking during the vehicle braking process, and ensures that the wheel still has redundant lateral force, providing the possibility for the subsequent intervention of the steering system;

[0064] In one embodiment of the present invention, Figure 2 As shown in Module 2, this module is mainly responsible for the risk assessment of vehicle driving safety after the brake system fails during emergency braking. The current health status of the vehicle's brake system is collected, the brake system failure factor is obtained, and the current braking risk value is calculated and evaluated through the current relative speed of the front and rear vehicles, the relative distance and the expected actuator cold start time interval, to determine whether the steering system needs to intervene, and the expected longitudinal position of the vehicle driving is dynamically calculated based on the risk value.

[0065] In one embodiment of the present invention, Figure 2 As shown in module 31 in module 3, according to the expected longitudinal position of the vehicle, the vehicle-mounted sensors in module 4 collect the surrounding obstacle information and the key status information of the vehicle operation, construct a safety obstacle function, and design a heuristic obstacle Lyapunov function based on it, which transforms the complex motion planning problem into a simple yaw angle tracking problem.

[0066] In one embodiment of the present invention, Figure 2 As shown in module 32 of module 3, the desired yaw angle is converted into the vehicle input front wheel steering angle value and the additional yaw moment value through the vehicle's existing yaw angular velocity tracking algorithm.

[0067] In one embodiment of the present invention, Figure 2 As shown in Module 4, the vehicle's front wheel angle is converted into the output of the power steering motor through the vehicle's steering mechanism precision tracking control algorithm and tire inverse model, so that the steering system can intervene in safe braking after the braking process fails.

[0068] In one embodiment of the present invention, the vehicle emergency braking AEB function will be triggered normally, and the ABS function will be triggered auxiliaryly to ensure that the vehicle will not experience wheel locking during braking;

[0069] In one embodiment of the present invention, module 2 is mainly responsible for evaluating and judging the emergency braking operation risk after the current braking system fails, and obtaining the adjusted expected lateral displacement of the vehicle, wherein the normalized braking risk decision function can be defined as:

[0070]

[0071] Wherein, function exp(·) is an exponential function, exponential term a>0, variables TTS, TTC are key collision time-domain safety indicators, and their definitions can be obtained in the automobile collision safety specification standard; parameter eps is an adjustable threshold value, which is used to ensure that the vehicle steering operation is maintained after activation, and the threshold value can reflect the maintenance degree of steering intervention; parameter ρ is the degree of failure of the braking system, and parameter τ is the actuator and system cold start time, during which 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 invention, the module 3 is mainly responsible for realizing the desired lateral displacement of the vehicle in module 2. In the process of reaching the desired lateral displacement, the target position and the potential obstacle information in the trajectory need to be considered. Without loss of generality, the safety function is designed as:

[0073]

[0074] 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 ois the longitudinal and lateral position of a certain obstacle, and the parameter μ is the detection distance limit of the vehicle sensor. When there are other obstacles, the safety function can be expressed as the sum of the safety function values ​​of the vehicle and each obstacle. It is worth noting that the safety function can be designed by the user as long as it satisfies the positive definiteness.

[0075] According to the above collision risk function, a safety barrier function is designed as follows:

[0076]

[0077] Wherein, parameter r is the limit collision safety distance. 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 the safety barrier function, the following integral heuristic barrier Lyapunov function can be designed:

[0078]

[0079] Where Y e is the lateral displacement error of the vehicle. Considering that the entire safety braking strategy needs to reach the desired lateral position before the vehicle stops completely, that is, there is a certain upper limit on the transient execution time of the algorithm. In order to ensure that the transient process of the auxiliary braking algorithm designed in the present invention meets the time domain constraints, the continuous time domain error transformation function is introduced as follows:

[0080]

[0081] 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. Through this function, combined with the above integral heuristic barrier Lyapunov function, the expected vehicle yaw angle expected value of the safety auxiliary braking algorithm replanning can be obtained as:

[0082]

[0083] Among them, v x is the longitudinal velocity of the vehicle, 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 methods. The parameter b>0 is the controller parameter, and the function Φ T1 The function Φ represents the switching time from transient state to steady state of the algorithm, which is T1. T .

[0084] It is worth noting that, in the present invention, unlike the existing fault-tolerant planning technology, the realization of the auxiliary safety braking function does not re-plan to obtain a new reference trajectory, but directly obtains the desired yaw angle of the vehicle integrated with the collision avoidance function, so that the fault-tolerant safety function integration is more convenient to embed into the vehicle chassis motion control layer, which can effectively improve the intelligence of chassis motion control and reduce the chassis's demand for computing power at the autonomous driving layer. In addition, compared with the traditional optimization-based planning and control method, the method of the present invention explicitly expresses the algorithm time constraints in the algorithm controller design, and uses the hard constraint method to implement the time constraints on its motion transient process, optimize the intermediate process of driving operation, and improve the feasibility of the algorithm in emergency braking scenarios.

[0085] Finally, relying on the existing desired yaw angle tracking algorithm, the desired yaw angle is converted and allocated to the expected response value of the vehicle chassis actuator. Without loss of generality, this embodiment can be applied to front-wheel drive, rear-wheel drive, and four-wheel drive vehicles. The difference is mainly reflected in the conversion and tracking of the desired yaw angle to the underlying actuator response under different chassis architectures. In addition, differential braking can be additionally introduced to improve the lateral movement capability of the vehicle and expand the steering intervention capability during safe braking. The design method is mainly to add an additional yaw torque input when designing the vehicle tracking desired yaw angle algorithm, which can be achieved using the existing coordinated control algorithm.

[0086] Furthermore, if Figure 3 As shown, the present invention takes the emergency braking scenario of an autonomous driving car 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 present invention can effectively improve the active fault-tolerant 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.

[0087] In summary, after the emergency braking (AEB) system is activated and the braking system fails, module 1 of the present invention first calculates the danger of the vehicle continuing to maintain the original braking operation according to the failure degree of the vehicle braking system and the risk assessment index of rear-end collision with the preceding vehicle, and dynamically adjusts the vehicle braking target. After that, module 2 designs a heuristic obstacle Lyapunov function according to the vehicle braking lateral displacement corrected by module 1, and uses the heuristic Lyapunov function to convert the expected lateral displacement into the expected vehicle driving yaw angle; module 3 realizes precise yaw angle tracking according to the chassis system configuration, and converts the expected yaw angle into the chassis front wheel steering angle response value and differential braking torque value; finally, module 4 calculates and obtains the steering power motor torque and wheel-side braking force through the existing wire control steering system control algorithm and braking force distribution algorithm, so as to realize the intervention of the steering system and the auxiliary safety braking function after the partial failure of the braking system.

[0088] According to the auxiliary emergency braking method after brake failure of the embodiment of the present invention, under the condition of triggering the emergency braking function, the risk of rear-end collision of the vehicle is first determined by the failure degree of the current brake system of the vehicle, and the decision after failure is made and the expected lateral displacement of the vehicle is obtained to determine whether the intervention of the steering system is required; in order to safely achieve the expected lateral displacement, a hazard assessment function and a heuristic obstacle Lyapunov function are designed, and the expected yaw angle of the vehicle integrating the active collision avoidance function is directly obtained by using them, and the vehicle motion trajectory is converted into an expected vehicle yaw angle; through the tracking control algorithm, it is converted into the front wheel steering angle of the vehicle; finally, through the 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. Under the function of emergency braking, the method decomposes the longitudinal driving risk of the vehicle after brake failure into the lateral dimension by introducing lateral force and steering system, thereby reducing the driving risk. At the same time, the method designs a time domain constraint transformation function to solve the problem of limited transient time under emergency braking conditions, and ensures that the vehicle successfully reaches the expected position before the braking is completed by presetting the time stability characteristics. The present invention can effectively improve the active safety of vehicles. The analytical nature of the algorithm makes the algorithm computationally inexpensive and easy to implement on vehicles, thus having great engineering application value.

[0089] In order to implement the above embodiment, Figure 4 As shown, this embodiment also provides a post-brake failure auxiliary emergency braking system 10 , which includes a failure factor acquisition module 100 , a desired displacement calculation module 200 , a desired yaw angle calculation module 300 and an emergency braking control module 400 .

[0090] A failure factor acquisition module 100 obtains a brake system failure factor based on a diagnosis result of a brake system health status of a current vehicle;

[0091] 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 vehicle expected lateral displacement according to the current braking risk value and the steering system data;

[0092] The expected yaw angle calculation module 300 obtains the expected vehicle driving yaw angle according to the function calculation result of the 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;

[0093] The emergency braking control module 400 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 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.

[0094] Furthermore, 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 vehicle in front; 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 self-driving layer sensing system.

[0095] Furthermore, the expression of the braking risk auxiliary decision function is:

[0096]

[0097] 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.

[0098] Furthermore, the expression of the integral heuristic barrier Lyapunov function is:

[0099] Construct a collision risk function:

[0100]

[0101] 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;

[0102] According to the collision risk function, a safety barrier function is constructed:

[0103]

[0104] 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;

[0105] According to the safety barrier function, an integral heuristic barrier Lyapunov function is constructed:

[0106]

[0107] Among them, Y e is the vehicle lateral displacement error.

[0108] Furthermore, a continuous time domain error transformation function is constructed:

[0109]

[0110] 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;

[0111] Based on the continuous time domain error transformation function and the integral heuristic barrier Lyapunov function, the desired vehicle yaw angle is calculated:

[0112]

[0113] 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 .

[0114] According to the auxiliary emergency braking system after brake failure of an embodiment of the present invention, under the condition of triggering the emergency braking function, the risk of rear-end collision of the vehicle is first determined by the failure degree of the current braking system of the vehicle, and a post-failure decision is made and the desired lateral displacement of the vehicle is obtained to determine whether the intervention of the steering system is required; 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 by using them, and the vehicle motion trajectory is converted into an expected vehicle yaw angle; through a tracking control algorithm, it is converted into a front wheel steering angle of the vehicle; finally, through precise control of the chassis subsystem, the front wheel steering angle is converted into a driving torque of the steering system power assist motor to achieve the safety of the emergency braking function.

[0115] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 invention. 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 the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0116] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

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 a current vehicle input front wheel steering angle value or a differential torque output value through a vehicle yaw angle controller, and the current vehicle input front wheel steering angle value is converted into a steering power motor output data, or the differential torque output value is converted into a wheel side braking / driving force specific 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; 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 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 ; 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, an integral heuristic barrier Lyapunov function can be constructed: Among them, Y e is the vehicle lateral displacement error.

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, 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. 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 a current vehicle input front wheel steering angle value or a differential torque output value through a vehicle yaw angle controller, and converts the current vehicle input front wheel steering angle value into a steering power motor output data, or converts the differential torque output value into a wheel-side braking / driving force specific 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; 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 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 ; 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, an integral heuristic barrier Lyapunov function can be constructed: Among them, Y e is the vehicle lateral displacement error.

5. The system according to claim 4, 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.

6. The system according to claim 4, 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.

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