Control method for vehicle braking, vehicle, storage medium, and program product

Abstract

The present disclosure relates to a control method of vehicle braking, a vehicle, a storage medium and a program product, applied to the field of intelligent driving, and the method comprises the following steps: in response to a braking control start instruction of the vehicle, determining an initial braking torque based on a brake pedal state, and controlling the vehicle to brake based on the initial braking torque; in response to the satisfaction of a safety condition, when the vehicle speed is reduced to a vehicle speed threshold value, controlling the vehicle to brake based on a braking torque curve; the braking torque curve represents that the braking torque decreases to a minimum braking torque from the initial braking torque starting with time variation, and the braking torque curve is determined based on a braking torque pressure relief ratio and a pressure relief duration; and the vehicle speed threshold value is determined based on the vehicle speed and a collision risk level. The present disclosure can ensure safe driving of the vehicle and perform comfortable braking parking, thereby improving the safety of driving.

Description

Technical Field

[0001] This disclosure relates to the field of vehicle control technology, and more specifically, to a vehicle braking control method, a vehicle, a storage medium, and a program product. Background Technology

[0002] With the rapid development of the automotive industry, users have increasingly higher requirements for vehicle driving comfort. During braking, due to inertia, the vehicle will produce a significant pitching impact, causing discomfort to the driver and passengers. In severe cases, it may even trigger motion sickness and other physiological reactions, affecting the riding experience.

[0003] To address the pitch impact problem, existing technologies include methods to reduce braking torque in a timely manner during vehicle braking to mitigate the pitch impact.

[0004] However, a reduction in braking torque inevitably increases the vehicle's braking distance, significantly raising the probability of rear-end collisions. Current technology struggles to effectively balance braking comfort and driving safety. When braking torque adjustment strategies prioritize comfort too much, driving safety is compromised; conversely, overemphasizing safety fails to adequately mitigate pitch impact, resulting in a diminished user experience.

[0005] Therefore, how to intelligently balance braking comfort and safety in complex traffic environments and avoid potential accidents caused by increased braking distance has become a core challenge facing the field of automotive control. Summary of the Invention

[0006] The purpose of this disclosure is to provide a vehicle braking control method, a vehicle, a storage medium, and a program product.

[0007] To achieve the above objectives, according to a first aspect of the present disclosure, a vehicle braking control method is provided, comprising: In response to a braking control initiation command for the vehicle, an initial braking torque is determined based on the brake pedal state, and the vehicle is controlled to brake based on the initial braking torque; the initial braking torque is input into a pitch dynamics model; and the braking torque relief ratio and relief duration output by the pitch dynamics model are obtained. In response to meeting safety conditions, when the vehicle speed decreases to a vehicle speed threshold, the vehicle is controlled to brake based on a braking torque curve; the braking torque curve represents the braking torque decreasing over time from the initial braking torque to the minimum braking torque value, and the braking torque curve is determined based on the braking torque relief ratio and the relief duration; the vehicle speed threshold is determined based on the vehicle speed and the collision risk level.

[0008] Optionally, the method further includes: When the vehicle is controlled to brake based on the braking torque curve so that the braking torque reaches the minimum value of the braking torque, the vehicle is controlled to brake based on the minimum value of the braking torque. When the vehicle speed decreases to 0, after a target time, the vehicle is controlled to brake based on the initial braking torque.

[0009] Optionally, the method further includes: The collision risk level is determined based on the speed difference and distance from the vehicle in front. Obtain the allowable increase in braking distance corresponding to the collision risk level; The vehicle speed threshold is determined by the allowable increase in braking distance.

[0010] Optionally, determining the collision risk level based on the speed difference with the vehicle in front and the distance to the vehicle in front includes: The collision time is determined based on the speed difference and distance from the vehicle in front. The collision risk level is determined based on the collision time.

[0011] Optionally, obtaining the permissible increase in braking distance corresponding to the collision risk level includes: Based on the vehicle speed, the road resistance acceleration is obtained; Based on the initial vehicle speed, the road resistance acceleration, the braking torque relief ratio, and the relief duration, the range of increase in braking distance is calculated for the vehicle under control braking based on the braking torque curve, the vehicle without control braking based on the braking torque curve, and the vehicle under control braking based only on the initial braking torque. The permissible increase in braking distance is determined based on the collision risk level, and the permissible increase in braking distance satisfies the range of braking distance increases.

[0012] Optionally, the method further includes: When the collision risk level is less than the preset risk level, the safety conditions are determined to be met. If the collision risk level is greater than or equal to the preset risk level, it is determined that the safety conditions are not met. In response to the failure to meet safety conditions, the vehicle is controlled to brake based on the initial braking torque, or emergency braking is performed.

[0013] According to a second aspect of the present disclosure, a vehicle is provided, comprising: processor; A memory for storing processor-executable instructions; wherein the processor is configured to perform the steps of any of the vehicle braking control methods provided in the first aspect of this disclosure.

[0014] According to a third aspect of the present disclosure, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the vehicle braking control methods provided in the first aspect of the present disclosure.

[0015] According to a fourth aspect of the present disclosure, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of any of the vehicle braking control methods provided in the first aspect of the present disclosure.

[0016] The above technical solution responds to the vehicle's braking control initiation command, determines the initial braking torque based on the brake pedal state, and controls braking. When safety conditions are met, and the vehicle speed decreases to a threshold speed, the vehicle is controlled to brake based on a braking torque curve. This braking torque curve is determined based on the braking torque relief ratio and duration. The vehicle speed threshold is determined based on the vehicle speed and collision risk level. The braking strategy can be intelligently adjusted according to the collision risk level. The initial braking torque is input into the pitch dynamics model to obtain the braking torque relief ratio and duration. After the vehicle speed decreases to the safety threshold, the braking torque is gradually reduced to suppress pitch impact, while ensuring the braking distance remains within a safe range. This effectively solves the problem of balancing comfort and safety in existing technologies, intelligently coordinating braking comfort and driving safety, effectively suppressing vehicle pitch impact, improving passenger comfort, and preventing safety hazards caused by excessive increases in braking distance due to braking torque adjustment.

[0017] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating a vehicle braking control method according to an exemplary embodiment; Figure 2 This is a schematic diagram illustrating the principle of a pitch dynamics model according to an exemplary embodiment; Figure 3 This is a schematic diagram illustrating a braking torque relief curve according to an exemplary embodiment; Figure 4 This is a schematic diagram illustrating a comparison of pitch angular velocities before and after applying braking torque depressurization according to an exemplary embodiment; Figure 5This is a schematic diagram illustrating the vehicle pitch rate response after applying a braking torque decompression curve, according to an exemplary embodiment. Figure 6 This is a schematic diagram illustrating a comparison of the increase in comfortable braking distance under different braking intensities and different depressurization start speeds, according to an exemplary embodiment. Figure 7 This is a schematic diagram illustrating the principle of a TTC collision distance monitoring model according to an exemplary embodiment; Figure 8 This is a schematic diagram illustrating a comfort braking strategy architecture based on a coupled collision distance monitoring model according to an exemplary embodiment; Figure 9 This is a block diagram illustrating a vehicle braking control device according to an exemplary embodiment. Detailed Implementation

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0020] In the description of the embodiments disclosed herein, terms such as "first" and "second" are used to distinguish similar objects and are not necessarily to be construed as a specific order or sequence. Furthermore, unless otherwise stated, in the description with reference to the accompanying drawings, the same reference numerals in different drawings denote the same elements.

[0021] It should be noted that all actions involving the acquisition of signals, information, or data in this disclosure are carried out in compliance with the relevant data protection laws and policies of the country where the location is situated, and with authorization from the owner of the relevant device.

[0022] Before introducing the specific implementation methods of this disclosure, the application scenarios of this disclosure will first be explained.

[0023] With the rapid development of the automotive industry, users have increasingly higher requirements for vehicle driving comfort. During braking, due to inertia, the vehicle will produce a significant pitching impact, causing discomfort to the driver and passengers. In severe cases, it may even trigger motion sickness and other physiological reactions, affecting the riding experience.

[0024] To address the pitch impact problem, existing technologies include methods to reduce braking torque in a timely manner during vehicle braking to mitigate the pitch impact.

[0025] However, reduced braking torque inevitably increases the vehicle's braking distance, significantly raising the probability of rear-end collisions. Current technologies struggle to effectively balance braking comfort and driving safety. When braking torque adjustment strategies prioritize comfort too much, driving safety is compromised; conversely, overemphasizing safety fails to adequately mitigate pitch impact, leading to a decreased user experience. How to intelligently balance braking comfort and safety in complex traffic environments, and avoid potential accidents caused by increased braking distance, has become a core challenge in the field of automotive control.

[0026] To address the aforementioned technical problems, this disclosure provides a vehicle braking control method, a vehicle, a storage medium, and a program product.

[0027] It should be noted that the subject of this disclosure may be a vehicle control unit, or a computing service device with data processing, network communication and program execution functions, such as a tablet computer, personal computer, mobile phone, etc., or an electronic device that can realize the above-mentioned vehicle braking control, etc. This disclosure does not specifically limit it.

[0028] The specific embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0029] Figure 1 A flowchart illustrating a vehicle braking control method provided in an embodiment of this disclosure. Figure 1 As shown, the method may include the following steps: S101: In response to the vehicle's braking control initiation command, determine the initial braking torque based on the brake pedal state, control the vehicle to brake based on the initial braking torque; input the initial braking torque into the pitch dynamics model; obtain the braking torque relief ratio and relief duration output by the pitch dynamics model.

[0030] In one embodiment of this disclosure, the brake control initiation command refers to a signal that triggers the vehicle braking process, which may originate from the driver's operation of the brake pedal. The brake pedal state refers to parameters such as the current position of the brake pedal, the depressing speed, or the depressing force, reflecting the driver's braking intention. The initial braking torque refers to the torque value determined based on the brake control initiation command and the brake pedal state at the beginning of the braking process, used to initiate braking. The driver generates the brake control initiation command by depressing the brake pedal, at which point the brake pedal state is detected by sensors and input to the vehicle control unit. The calculation of the initial braking torque can be performed using methods described in related technologies, and this disclosure does not limit it thereto.

[0031] Understandably, in response to the braking control initiation command for the vehicle, the initial braking torque is determined based on the brake pedal state, and the brakes are driven to apply this torque, causing the vehicle to begin deceleration. The initial braking torque is the torque applied at the start of braking, directly determining the vehicle's deceleration level and the resulting pitch motion tendency. The pitch dynamics model, by simulating the vehicle's dynamic response during braking, can predict key parameters such as the vehicle's pitch angle and pitch rate. By inputting the initial braking torque into the pitch dynamics model, the output parameters (braking torque relief ratio and relief duration) are obtained. This model can predict and analyze the vehicle's pitch response based on actual operating conditions. The pitch dynamics model can be a mathematical model based on physical equations. This model receives parameters such as the initial braking torque, wheel mass, overall vehicle pitch angle, and front / rear wheelbase as input. By solving the vehicle's motion differential equations, it outputs the braking torque relief ratio and relief duration that effectively suppress pitch under different braking conditions.

[0032] S102: In response to meeting safety conditions, when the vehicle speed decreases to a vehicle speed threshold, the vehicle is controlled to brake based on the braking torque curve; the braking torque curve represents the braking torque decreasing over time from the initial braking torque to the minimum braking torque value, and the braking torque curve is determined based on the braking torque relief ratio and the relief duration; the vehicle speed threshold is determined based on the vehicle speed and the collision risk level.

[0033] In one embodiment of this disclosure, safety conditions refer to the criteria used to determine whether braking torque adjustment can be made to improve comfort during vehicle braking, thus deciding whether braking according to the braking torque curve is permitted. The vehicle speed threshold refers to the specific speed point at which the vehicle control unit begins to execute braking according to the braking torque curve when the vehicle speed decreases to that threshold. The vehicle speed threshold can be a preset speed value, determined based on the vehicle speed and the collision risk level. The braking torque curve is a function characterizing the change of braking torque over time, defining the pattern of braking torque gradually decreasing from its initial value to its minimum value. The minimum braking torque value refers to the minimum braking torque that can be achieved when braking according to the braking torque curve. The braking torque relief ratio refers to the magnitude or percentage reduction of the braking torque relative to the initial braking torque. The relief duration refers to the length of time it takes for the braking torque to decrease from its initial value to its minimum value. The collision risk level refers to the degree of potential collision hazard assessed based on the vehicle's current driving environment and state (e.g., distance to the vehicle ahead, relative speed, etc.), and can be categorized as extremely low collision risk, low collision risk, medium collision risk, and high collision risk. For example, extremely low collision risk and low collision risk meet safety conditions and allow braking based on the braking torque curve.

[0034] Understandably, when the risk level is extremely low or low collision risk and the vehicle speed decreases to a speed threshold, the vehicle is controlled to brake based on the braking torque curve. As the vehicle speed gradually decreases from the higher speed at the start of braking and reaches the speed threshold, braking is then performed based on the braking torque curve.

[0035] By employing the above method, this disclosure effectively mitigates the pitching impact caused by sudden changes in braking torque during traditional braking by applying braking based on the braking torque curve when the vehicle speed decreases to a threshold speed, under the premise of meeting safety conditions. This significantly improves ride comfort. Furthermore, by correlating the vehicle speed threshold with vehicle speed and collision risk level, intelligent management of the risk of increased braking distance is achieved, thus ensuring braking safety while improving comfort.

[0036] As an optional implementation method, the vehicle braking control method further includes the following steps: When the vehicle is controlled to brake based on the braking torque curve so that the braking torque reaches the minimum value, the vehicle is controlled to brake based on the minimum value of the braking torque. When the vehicle speed decreases to 0, after the target time, the vehicle is controlled to brake based on the initial braking torque.

[0037] Understandably, when the vehicle is controlled to brake based on the braking torque curve until the braking torque reaches its minimum value, the purpose of controlling the vehicle to brake based on the minimum braking torque is to ensure that the vehicle can continuously and stably maintain the minimum braking torque at the end of the braking process, that is, after the braking torque curve drops to the preset minimum braking torque value, so as to avoid further decrease in braking torque, thereby ensuring the braking performance and ride comfort of the vehicle when it is close to a complete stop.

[0038] When the vehicle speed decreases to 0, after a target time, the vehicle is controlled to brake based on the initial braking torque. The core principle is to introduce a brief buffer period (the target time) after the vehicle comes to a complete stop, followed by a return to the initial braking torque, to prevent the vehicle from unexpectedly moving while stationary, such as rolling away. In one implementation, when the vehicle speed sensor detects that the vehicle speed has decreased to 0, the vehicle control unit starts an internal timer. After the target time has elapsed, the control unit sends a command to reapply the initial braking torque, thereby firmly fixing the vehicle in place.

[0039] By employing the above method, this disclosure further improves the entire braking control process from deceleration to complete stop, building upon the existing braking control based on the braking torque curve to mitigate pitch impact. After the braking torque curve drops to its minimum value, maintaining this minimum braking torque effectively avoids drastic fluctuations in braking torque at the end of deceleration, ensuring a smooth transition in deceleration as the vehicle approaches a stop, thus significantly improving ride comfort. Furthermore, when the vehicle speed decreases to 0, a target time is introduced as a buffer before restoring the initial braking torque. This strategy aims to provide sufficient holding force after the vehicle comes to a complete stop, effectively preventing the vehicle from rolling due to insufficient braking force, especially on slopes or uneven surfaces, thereby enhancing the overall driving experience and safety.

[0040] For example, such as Figure 2 As shown, the dynamic model includes components such as the vehicle body, front and rear active suspensions, and tires. Since the vehicle speed is low when braking, the effect of wind resistance can be ignored.

[0041] in, For the mass of the wheel; Center of mass; The pitch angle of the entire vehicle; The height of the center of mass; This refers to the front wheelbase; This refers to the rear wheelbase; This represents the vertical displacement of the vehicle body; Half the vehicle weight; The moment of inertia of the vehicle's center of mass; This refers to the speed of the entire vehicle. The vertical distance from the center of mass to the center of tilt; The horizontal distance from the center of mass to the center of tilt; This represents the vertical displacement of the front suspension. This refers to the vertical displacement of the rear suspension. For the front tire spring stiffness; For the rear tire spring stiffness; This refers to the damping coefficient of the front tires; This refers to the rear tire damping coefficient. The longitudinal force on the ground for the front wheel; This refers to the longitudinal force on the ground around the rear wheel.

[0042] The equation of motion for the vertical displacement of the vehicle body is shown in equation (1), where The vertical force is the force exerted on the front and rear suspensions. This refers to the vertical displacement of the vehicle body. This is the sprung mass of half the vehicle.

[0043] (1) The vertical force provided by the suspension includes the spring stiffness force, the damper damping force, and the active force of the active suspension system, calculated as shown in equation (2). This refers to the front suspension spring stiffness. For the rear suspension spring stiffness, This represents the vertical displacement of the ground. This refers to the vertical displacement of the ground afterward. This represents the vertical displacement of the front wheels. This refers to the vertical displacement of the rear wheels. This is the front suspension damping coefficient. This refers to the rear suspension damping coefficient. As the main power source for the front suspension, The rear suspension is the main power source; (2) Due to the pitch angle when the vehicle body sways The maximum vertical displacement is generally no more than 3°, therefore the vertical displacement of the front and rear suspensions in equation (2) can be determined according to... Figure 2 The approximate calculation is performed using equation (3).

[0044] (3) For the front and rear wheels, the vertical motion equation is the sum of the tire vertical force and the suspension vertical force, as shown in equation (4). (4) In the horizontal direction, the equation of motion of the vehicle caused by the longitudinal force generated by braking is shown in equation (5). (5) Combining the longitudinal force of ground braking and the active force of the suspension, With the pitch center as the center, the equation of motion for the entire vehicle pitching motion is shown in equation (6). (6) Inertia Calculated from the parallel axis theorem (7) (7) The state equations of the pitch dynamics model can be solved according to equations (1)-(7). Since the vertical disturbance of the ground under braking conditions of actual vehicles is generally manifested as a macroscopic slope effect, and the instantaneous vertical disturbance at low speed is weak, then... All values ​​can be taken as 0. Furthermore, the inherent stiffness of vehicle tires is generally more than ten times that of the suspension, a significant difference. Therefore, the vertical deformation of the tires and the displacement of the suspension can be equivalently combined to simplify the calculation of the state equation. The equivalent suspension stiffness coefficient... and damping coefficient As shown in equation (8), where These are the ratios of the tire stiffness coefficient to the front and rear suspension stiffness coefficients, respectively.

[0045] (8) Selecting pitch angle, pitch angular velocity, vertical displacement and velocity of sprung mass as state variables, the state variable matrix is ​​designed as follows: The active forces of the front and rear suspensions and the longitudinal forces of the front and rear wheels on the ground are selected as control variables, and their matrices are as follows: Choosing pitch angular velocity as the output variable, and combining equations (1)-(8), the state equation of the half-vehicle pitch dynamics model is shown in equation (9). (9) The state space matrices A, B, and C of the system are shown in equations (10)-(12), respectively. (10) (11) (12) Since the braking torque has a major effect on pitch motion during braking, to facilitate observation of the influence of the longitudinal braking force on the pitch angular velocity, we can first assume that the active forces of the front and rear suspensions are zero, and set the initial moment... The initial state is If the value is 0, then the time-domain solution of the linear differential equation for the pitch motion is shown in equation (13), where Let be the state transition matrix.

[0046] (13) When braking to a stop under normal conditions with a fixed braking torque, the longitudinal force exerted on the vehicle body by the ground disappears instantaneously upon stopping, which is equivalent to a reverse step input of longitudinal force. In the formula Let be the initial pedal braking torque, with a positive sign. The time-domain response of the pitch motion is shown in equation (14). (14) To mitigate braking pitch impact, this invention designs an adaptive three-stage braking torque relief curve, such as... Figure 3 As shown, the horizontal axis represents time, and the vertical axis represents the magnitude of the braking torque. Initial braking torque T b1 The braking force is supplied by the driver's brake pedal. When the vehicle speed decreases to a certain threshold, the comfort braking function is triggered and connected to the control torque. The braking torque follows a cubic curve (i.e., the braking torque curve). The braking torque decreases smoothly according to the initial braking torque ratio over the time period. When the pressure relief action is completed, the braking torque is maintained at its minimum value until complete braking (i.e., within time period t1), and then restored to the initial braking torque after a period of time (i.e., within time period t2) to prevent the vehicle from rolling away. The calculation of the three braking torque pressure relief curves is shown in equation (15), where This refers to the braking torque relief ratio. This refers to the duration of pressure relief.

[0047] (15) Therefore, the pitch response after applying the depressurization curve can be transformed into the superposition of two longitudinal force control inputs with a phase difference, namely the longitudinal force input during the depressurization phase. longitudinal force input during braking phase The pitch motion time-domain response is shown in equation (16). (16) To facilitate numerical calculations, the state transition matrix can be... Expanding the expression in Taylor series polynomial form, the expansion is shown in equation (17). (17) Substituting equation (17) into equations (15) and (16) for calculation and solution, we obtain a comparison of the pitch angular velocities before and after the application of the braking torque curve, as follows: Figure 4 As shown, the horizontal axis represents time, and the vertical axis represents the vehicle pitch angle. The comfort braking torque curve designed in this disclosure decomposes the pitch velocity impact at the end of braking into two smaller impacts: pressure relief and complete braking, effectively reducing the peak pitch velocity. In a real-world vehicle environment, due to the nonlinearity of the damping indicator curve, the suspension anti-roll angle, and the braking slip ratio, the pitch velocity response effect after applying the comfort braking curve is as follows: Figure 5 As shown, the theoretical and real-vehicle verification results are basically consistent.

[0048] The design of the three braking torque curves disclosed herein also facilitates the smooth intervention and disengagement of the comfort braking function. These curves can adaptively adjust their shape parameters based on brake pedal depth and the driver's preferred braking style, suppressing pitch shock during vehicle stopping. They achieve optimal optimization of the vehicle's pitch angular velocity under different braking intensities, effectively reducing calibration workload. Because these curves possess a precise mathematical expression, the increased braking distance due to comfort braking can also be quantitatively analyzed.

[0049] Specifically, after receiving the brake control start command, the vehicle's brake controller calculates the current initial braking torque based on the signals from the brake pedal sensors (e.g., pedal travel sensor, pedal force sensor), and sends this value to the control unit responsible for pitch dynamics model calculation via the vehicle's internal communication network (e.g., CAN bus).

[0050] By employing the above method, this disclosure can dynamically adjust the pressure relief strategy of the braking torque according to the vehicle's current braking intensity and pitch dynamics characteristics, thereby maximally suppressing the vehicle's pitch impact and significantly improving the ride comfort of the driver and passengers. Since the pressure relief parameters are calculated based on the vehicle dynamics model, they ensure both comfort and braking safety, avoiding risks such as excessively long braking distances caused by excessive pressure relief, thus achieving a precise balance between braking comfort and safety.

[0051] As an optional implementation method, the vehicle braking control method further includes the following steps: The collision risk level is determined based on the speed difference and distance from the vehicle in front, including: determining the collision time based on the speed difference and distance from the vehicle in front; and determining the collision risk level based on the collision time. Obtaining the permissible increase in braking distance corresponding to the collision risk level includes: obtaining the road resistance acceleration based on the vehicle speed; calculating the increase in braking distance based on the initial vehicle speed, road resistance acceleration, braking torque relief ratio, and relief duration, for vehicles with control applied braking based on the braking torque curve, vehicles without control applied braking based on the braking torque curve, and vehicles with control applied braking based only on the initial braking torque; determining the permissible increase in braking distance based on the collision risk level, ensuring that the permissible increase in braking distance meets the permissible increase in braking distance range; The vehicle speed threshold is determined by the increase in the allowable braking distance.

[0052] Understandably, collision risk level is a crucial indicator for assessing the safety of the current driving scenario, providing a basis for subsequent braking strategy adjustments. Time to Collision (TTC) is the predicted time required for a vehicle to collide with an obstacle or vehicle ahead; it's a key indicator of collision urgency, with a shorter TTC indicating a higher collision risk. Determining the collision risk level first requires assessing the speed difference and distance to the vehicle ahead. This information can be obtained using onboard radar, lidar, or visual sensors.

[0053] The abstract collision risk level is then transformed into a specific, actionable braking performance indicator (allowable increase in braking distance). The allowable increase in braking distance represents the additional braking distance the system can tolerate relative to the completely safe braking distance at the current collision risk level, in order to improve braking comfort. Road resistance acceleration refers to the deceleration generated by factors such as road friction, air resistance, and rolling resistance during vehicle braking, in addition to the deceleration generated by the braking torque. Specifically, the vehicle's deceleration can be monitored in real time using vehicle sensors (such as wheel speed sensors and accelerometers), and road resistance acceleration can be estimated based on the vehicle's rate of change of speed when the brake pedal is not depressed or the braking torque is zero. Further, the increase in braking distance resulting from braking using a braking torque curve compared to braking with the initial braking torque maintained throughout the braking process is quantified. The allowable increase in braking distance is determined by the collision risk level, and this allowable increase must fall within the previously calculated range of braking distance increases. For example, a larger increase in braking distance is allowed at low risk to maximize comfort, while a smaller increase is allowed at high risk to prioritize safety.

[0054] Finally, the allowable increase in braking distance is directly mapped to the vehicle speed threshold that triggers the braking torque curve. The vehicle speed threshold refers to the critical speed at which the vehicle switches from initial braking torque braking to braking based on the braking torque curve (i.e., the start of pressure relief) during braking. This vehicle speed threshold ensures that the comfort braking strategy is only activated when the collision risk is within a controllable range and the increase in braking distance is within the allowable range.

[0055] For example, this disclosure establishes a comfortable braking distance estimation model, and based on this model, solves the vehicle speed threshold of the braking torque curve. This includes the following steps: Step 1: Due to variations in road surface adhesion coefficient and slope, the driving resistance generated on the vehicle also varies, thus affecting the braking distance. Therefore, an accurate estimate of the road resistance deceleration is necessary before calculating the braking distance. First, based on the real-time brake master cylinder pressure and drive motor torque, it is determined whether the vehicle is in a coasting condition without driver intervention. The longitudinal acceleration signal from the IMU (Inertial Measurement Unit) under this condition is low-pass filtered, and then the average acceleration is calculated through a fixed-length sliding window, continuously updated. When driver intervention is detected, the calculation stops, and the average acceleration estimated in the last cycle is saved as the approximate road resistance acceleration under the current driving surface. .

[0056] Step 2: Based on the braking torque relief curve, divide the comfort braking condition into three stages: before relief, during relief, and after relief. Calculate the braking distance generated by the vehicle in each of the three stages, and sum them to obtain the total braking distance under the entire comfort braking condition. Set the starting speed for braking distance estimation. The vehicle speed threshold that triggers depressurization is (generally The vehicle speed at which the braking torque curve ends is Acceleration before depressurization The acceleration at the end of the depressurization is The duration of the pressure relief is The braking torque relief ratio is Assuming the vehicle stops after depressurization, the braking distances generated by the vehicle in the three stages are calculated as shown in equations (18)-(24). stage: (18) stage: (19) (20) Integration time range Substitute into equations (19) and (20) to calculate , As shown in equations (21)-(22), (twenty one) (twenty two) stage: (twenty three) The braking distance is calculated as shown in equation (24) when the vehicle is not depressurized. (twenty four) The final increase in braking distance due to comfort braking is shown in equation (25). (25) like If the value is too small, the vehicle will stop before the pressure relief is complete. At this point, the optimization effect of the pitch velocity amplitude deteriorates, but the increase in braking distance is even smaller. The stopping moment is marked by the critical point at which the braking torque pressure relief is complete. Therefore, the result calculated from equation (21) critical value As shown in equation (26), (26) Therefore Less than At that time, the vehicle braking distance only includes two segments. The calculation of the braking distance for each stage is consistent with equation (18). The time range of the phase integration becomes ,in The duration from the start of depressurization to the complete stop of the vehicle, as shown in equation (27), can be derived from... Calculated, therefore The stage braking distance is calculated as shown in equation (28). (27) (28) Therefore, the increase in braking distance under this operating condition is shown in equation (29). (29) The relationship between the increase in vehicle comfort braking distance and driver braking intensity and the initial speed of pressure relief is as follows: Figure 6 As shown, the lower the braking intensity and the earlier the vehicle depressurizes, the greater the increase in braking distance, and the greater the distance the algorithm needs to maintain for implementation. If the depressurization initiation speed is selected too high, then... Figure 5 As shown, the horizontal axis represents time, and the vertical axis, from top to bottom, represents velocity, pitch rate, and braking torque, respectively. Figure 5 The pitch rate curves during the depressurization phase and the braking phase are too far apart, and they do not overlap, thus failing to further improve the pitch rate optimization effect. Furthermore, the driver's braking experience feels sluggish and discontinuous. Therefore, the depressurization speed threshold needs to be adjusted. Set upper limit If the depressurization speed threshold is reached... When the speed is too low, the vehicle status signal error increases, and the accuracy of braking distance estimation is low. Therefore, the pressure relief speed threshold is... A lower limit also needs to be designed. Depressurization speed threshold The effective adjustment range is limited to Within this range, the corresponding increase in braking distance is as follows: .

[0057] Step 3: To avoid rear-end collisions caused by the activation of comfort braking, the vehicle needs to assess the current brake pressure relief safety in real time based on the TTC collision distance monitoring model and calculate the allowable increase in braking distance. The braking distance estimation model is used as input. The TTC collision time calculation refers to the time required for both vehicles to maintain their current speeds until a collision occurs, starting from the current moment. The shorter this time, the greater the current collision risk. The TTC collision algorithm is only entered when the speed of the following vehicle is greater than that of the preceding vehicle. Therefore, the preceding and following vehicles should satisfy equation (30), where... Represents the speed and acceleration of the vehicle in front. Represents the speed and acceleration of the vehicle behind. This represents the real-time relative distance between the two vehicles. This represents the safe parking distance, which is generally obtained by the AEB algorithm. Increase the braking distance for a more comfortable braking experience.

[0058] (30) The TTC collision time is obtained as shown in equation (31), where These represent the difference in relative speed and the difference in acceleration between the two vehicles. (31) First, based on the current vehicle inertia and braking performance, different time thresholds are defined for the TTC algorithm. This categorizes the collision risk level during vehicle braking into four types, and correspondingly employs different comfort or emergency braking strategies to balance comfort and safety. An example of the TTC time thresholds is provided, and the TTC collision distance monitoring model principle diagram is shown below. Figure 7 As shown.

[0059] (1) TTC > 2.6s, extremely low collision risk, strong comfort braking mode (larger depressurization start speed). (2) 2.6s≥TTC>1.6s, low collision risk, weaker comfort braking mode (smaller depressurization start speed). (3) 1.6s≥TTC>0.6s, medium collision risk, disable comfort braking and AEB partial braking intervention; (4) 0.6s≥TTC, high collision risk, disable comfort braking and AEB emergency braking intervention.

[0060] Considering that the effective braking distance increase range in step 2 is limited to To solve for the current allowable increase in braking distance It can generate an array of braking distance increases within a range. Substitute it into equation (31) to calculate the corresponding TTC time array. Based on the different values ​​of the elements in the array, it is divided into the following types. (1) If all elements in the TTC time array are greater than 2.6s, that is, all TTC time solutions have a very low collision risk, then select To achieve optimal braking comfort.

[0061] (2) If all elements in the TTC time array are less than or equal to 1.6s, that is, all TTC time solutions have medium / high collision risk, then select This means disabling the comfort braking function to ensure safety.

[0062] (3) If some elements in the TTC time array are greater than 1.6s and less than 2.6s, a weighting function can be established to comprehensively balance braking comfort and safety, as shown in equation (32), where The weighting coefficients are divided into braking distance and TTC time threshold, and there are Established.

[0063] (32) Substitute the TTC time array and braking distance array into equation (1) to calculate the weight of each group of elements. The element with the largest sum of weights is selected as the allowable increase in braking distance, i.e. .

[0064] Because the vehicle's speed and acceleration change during braking, and the TTC time array is constantly updated, the algorithm outputs the allowable braking distance increase. The output should also be calculated repeatedly until the vehicle's comfort braking is activated or AEB emergency braking intervenes.

[0065] Step 4: Increase the allowable braking distance output in Step 3. Substituting these equations into the analytical expressions for the increase in braking distance (25) and (29), the vehicle speed threshold can be obtained by inverse solving. Wait for the vehicle speed to decrease until the difference between the current actual vehicle speed and the initial speed at which pressure is released is less than 0.2 m / s before fixing the vehicle speed threshold. Combined with the duration of pressure relief Braking torque relief ratio The system outputs a complete braking torque curve based on parameters such as braking force, enabling comfortable braking.

[0066] The comfort braking strategy architecture disclosed herein is as follows: Figure 8 As shown, a cubic braking torque curve that can adaptively adjust according to braking intensity and driving conditions is designed. Its core parameters are the braking torque relief ratio, relief time, and relief speed threshold (relief initiation speed). First, relying on an offline theoretical half-vehicle pitch dynamics model, the optimal curve shape parameters are calculated by the pitch angular velocity time-domain solution module using the driver's braking torque as input. On the other hand, the actual vehicle braking condition calibration dataset also provides curve shape parameters. The parameter optimization module combines the module's output to determine the optimal braking torque relief ratio under the current braking intensity. and the duration of pressure relief Secondly, the TTC collision distance monitoring model estimates the current braking collision risk level and the allowable increase in braking distance by using the speed difference and acceleration difference of the vehicle ahead identified by lidar. This information is then passed to the braking distance estimation model, which uses comprehensive braking distance calculations to inversely determine the depressurization speed threshold under the current driving conditions. .

[0067] After determining the shape parameters of the braking torque curve, a vehicle braking torque request signal is sent to the electro-hydraulic brake. The braking system uses a feedforward + feedback control module to decompose the braking torque request into pressure control signals for each brake wheel cylinder, adjusting the brake oil valve opening to complete closed-loop control. At the same time, the suspension's built-in fuzzy PID damping controller also adjusts the damper current based on the pitch angle and pitch velocity values ​​obtained from the IMU, assisting in reducing the pitch motion amplitude.

[0068] This disclosure estimates the increase in braking distance caused by the execution of comfort braking function through an accurate mathematical expression of the braking torque curve, quantifies the impact of function intervention on braking distance at different vehicle speeds, and accurately calculates the range of braking distance increase by combining the optimization effect on pitch impact. Based on this range, the comfort braking strategy can dynamically calculate the optimal vehicle speed threshold by combining the allowable increase in braking distance, achieving a balance between comfort and safety. This disclosure proposes an improved TTC collision distance monitoring risk model that incorporates the additional braking distance generated by comfort braking into the TTC time calculation. According to different TTC time thresholds, braking collision risks are divided into very low risk, low risk, medium risk, and high risk. For different collision risks, various strategies such as stronger comfort braking, weaker comfort braking, and emergency braking are adopted to calculate the maximum allowable increase in braking distance for comfort braking, achieving a smooth transition of braking strategy.

[0069] By employing the above method, this disclosure determines the collision risk level based on the speed difference and distance from the vehicle in front, avoiding the safety hazards caused by blindly implementing braking torque decompression. It can dynamically adjust the braking strategy according to the collision risk in the actual driving scenario, ensuring that the vehicle only enters the braking torque decompression stage when the collision risk is within a controllable range. Thus, while ensuring driving safety, it optimizes the pitch impact during braking to the greatest extent, achieving a balance between comfort and safety, thereby improving the robustness and adaptability of the overall braking strategy.

[0070] As an optional implementation method, the vehicle braking control method further includes the following steps: When the collision risk level is less than the preset risk level, the safety conditions are met. If the collision risk level is greater than or equal to the preset risk level, it is determined that the safety conditions are not met. In response to a failure to meet safety conditions, the vehicle is controlled to brake based on the initial braking torque, or emergency braking is performed.

[0071] Understandably, a preset risk level is a pre-defined safety threshold used to distinguish whether the current collision risk is within an acceptable safety range. When the actual assessed collision risk level is below this threshold, the current environment is considered relatively safe, and comfort can be prioritized; when it is above or equal to this threshold, a potential hazard is considered, and safety should be prioritized. The preset risk level can be a fixed value, for example, calibrated at the factory according to regulatory requirements, vehicle type, or driving mode. Alternatively, the preset risk level can be dynamically adjustable, for example, adjusted in real time based on factors such as the driver's driving habits, road type (e.g., highway, city road), and weather conditions (e.g., rain, snow, fog, haze) to adapt to different driving scenarios.

[0072] Whether safety conditions are met is the basis for deciding on braking strategy switching. When safety conditions are met, a braking strategy aimed at improving comfort (braking based on the braking torque curve) can be implemented; when safety conditions are not met, it is necessary to switch to a braking strategy that prioritizes safety.

[0073] Emergency braking refers to actively applying the maximum braking torque in situations of medium to high collision risk to decelerate or stop the vehicle as quickly as possible, thereby avoiding or mitigating the consequences of a collision.

[0074] By employing the above method, the dynamic braking strategy disclosed herein can effectively balance braking comfort and driving safety, improve the driving experience, ensure that braking torque is not reduced in dangerous scenarios, and effectively avoid the occurrence of traffic accidents such as rear-end collisions.

[0075] Figure 9 This is a schematic diagram of a vehicle braking control device provided in an embodiment of this disclosure. Figure 9 As shown, the control device 900 includes: a first control module 901 and a second control module 902.

[0076] The first control module 901 is used to respond to the vehicle's braking control start command, determine the initial braking torque based on the brake pedal state, control the vehicle to brake based on the initial braking torque, input the initial braking torque into the pitch dynamics model, and obtain the braking torque relief ratio and relief duration output by the pitch dynamics model. The second control module 902 is used to control the vehicle to brake based on the braking torque curve when the vehicle speed decreases to the vehicle speed threshold in response to meeting safety conditions. The braking torque curve represents the braking torque decreasing from the initial braking torque to the minimum braking torque over time. The braking torque curve is determined based on the braking torque relief ratio and the relief duration. The vehicle speed threshold is determined based on the vehicle speed and the collision risk level.

[0077] The vehicle braking control device is determined according to any of the vehicle braking control methods in the above embodiments of this disclosure.

[0078] Optionally, the vehicle braking control device further includes a third control module for: When the vehicle is controlled to brake based on the braking torque curve so that the braking torque reaches the minimum value, the vehicle is controlled to brake based on the minimum value of the braking torque. When the vehicle speed decreases to 0, after the target time, the vehicle is controlled to brake based on the initial braking torque.

[0079] Optionally, the vehicle braking control device further includes a fourth control module, which includes: The first determination submodule is used to determine the collision risk level based on the speed difference with the vehicle in front and the distance to the vehicle in front; The first acquisition submodule is used to acquire the allowable increase in braking distance corresponding to the collision risk level; The second determining submodule is used to determine the vehicle speed threshold based on the allowable braking distance increase.

[0080] Optionally, the first determining submodule is specifically used for: The collision time is determined based on the speed difference and distance from the vehicle in front. The collision risk level is determined based on the collision time.

[0081] Optionally, the first acquisition submodule is specifically used for: Based on the vehicle speed, the road resistance acceleration is obtained; Based on the initial vehicle speed, road resistance acceleration, braking torque relief ratio, and relief duration, calculate the range of increase in braking distance resulting from braking based on the braking torque curve for vehicles with control executed, braking based on the braking torque curve for vehicles without control executed, and braking based on the initial braking torque for vehicles with only control executed. The permissible increase in braking distance is determined by the collision risk level, and the permissible increase in braking distance must meet the range for increasing braking distance.

[0082] Optionally, the vehicle braking control device further includes a fifth control module for: When the collision risk level is less than the preset risk level, the safety conditions are met. If the collision risk level is greater than or equal to the preset risk level, it is determined that the safety conditions are not met. In response to a failure to meet safety conditions, the vehicle is controlled to brake based on the initial braking torque, or emergency braking is performed.

[0083] Using the aforementioned device, in response to a braking control initiation command for the vehicle, the initial braking torque is determined based on the brake pedal state and braking is controlled. Furthermore, when safety conditions are met, and the vehicle speed decreases to a speed threshold, the vehicle is controlled to brake based on a braking torque curve. This braking torque curve is determined based on the braking torque relief ratio and duration. The speed threshold is determined based on the vehicle speed and collision risk level. The device can intelligently adjust the braking strategy according to the collision risk level, gradually reducing the braking torque after the vehicle speed decreases to a safe threshold to suppress pitch impact, while ensuring the braking distance remains within a safe range. This effectively solves the problem of balancing comfort and safety in existing technologies, intelligently coordinating braking comfort and driving safety, effectively suppressing vehicle pitch impact, improving passenger comfort, and preventing safety hazards caused by excessive increases in braking distance due to braking torque adjustment.

[0084] This disclosure also provides a vehicle, the vehicle comprising: A memory on which computer programs are stored; A processor for executing a computer program in memory, the processor being configured to perform the steps of the vehicle braking control method described above.

[0085] For example, the vehicle can be a hybrid vehicle, a non-hybrid vehicle, an electric vehicle, a fuel cell vehicle, or other types of vehicles. The vehicle can be an autonomous vehicle, a semi-autonomous vehicle, or a non-autonomous vehicle.

[0086] This disclosure also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the vehicle braking control method described above.

[0087] This disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the vehicle braking control method described above.

[0088] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0089] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A vehicle braking control method, characterized in that, include: In response to a braking control initiation command for the vehicle, an initial braking torque is determined based on the brake pedal state, and the vehicle is controlled to brake based on the initial braking torque. Input the initial braking torque into the pitch dynamics model; obtain the braking torque relief ratio and relief duration output by the pitch dynamics model; In response to meeting safety conditions, when the vehicle speed decreases to a vehicle speed threshold, the vehicle is controlled to brake based on a braking torque curve; the braking torque curve represents the braking torque decreasing over time from the initial braking torque to the minimum braking torque value, and the braking torque curve is determined based on the braking torque relief ratio and the relief duration; the vehicle speed threshold is determined based on the vehicle speed and the collision risk level.

2. The method according to claim 1, characterized in that, The method further includes: When the vehicle is controlled to brake based on the braking torque curve so that the braking torque reaches the minimum value of the braking torque, the vehicle is controlled to brake based on the minimum value of the braking torque. When the vehicle speed decreases to 0, after a target time, the vehicle is controlled to brake based on the initial braking torque.

3. The method according to claim 1, characterized in that, The method further includes: The collision risk level is determined based on the speed difference and distance from the vehicle in front. Obtain the allowable increase in braking distance corresponding to the collision risk level; The vehicle speed threshold is determined by the allowable increase in braking distance.

4. The method according to claim 3, characterized in that, The method of determining the collision risk level based on the speed difference and distance from the vehicle in front includes: The collision time is determined based on the speed difference and distance from the vehicle in front. The collision risk level is determined based on the collision time.

5. The method according to claim 3, characterized in that, The step of obtaining the permissible increase in braking distance corresponding to the collision risk level includes: Based on the vehicle speed, the road resistance acceleration is obtained; Based on the initial vehicle speed, the road resistance acceleration, the braking torque relief ratio, and the relief duration, the range of increase in braking distance is calculated for the vehicle under control braking based on the braking torque curve, the vehicle without control braking based on the braking torque curve, and the vehicle under control braking based only on the initial braking torque. The permissible increase in braking distance is determined based on the collision risk level, and the permissible increase in braking distance satisfies the range of braking distance increases.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: When the collision risk level is less than the preset risk level, the safety conditions are determined to be met. If the collision risk level is greater than or equal to the preset risk level, it is determined that the safety conditions are not met. In response to the failure to meet safety conditions, the vehicle is controlled to brake based on the initial braking torque, or emergency braking is performed.

7. A vehicle, characterized in that, include: processor; A memory for storing processor-executable instructions; wherein the processor is configured to perform the steps of the method according to any one of claims 1-6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method described in any one of claims 1-6.

9. A computer program product, characterized in that, Includes a computer program that, when executed by a processor, implements the steps of the method according to any one of claims 1-6.

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