Vehicle braking method and related device

Abstract

The invention discloses a vehicle braking method and a related device, and if the vehicle speed of a vehicle is smaller than a preset vehicle speed threshold value, the vehicle is controlled to enter a comfortable braking mode. In the comfortable braking mode, deceleration of the vehicle is acquired, and an upper limit value of a wheel braking force is determined based on the deceleration. A rear wheel braking force setting value and a front wheel braking force setting value are determined according to the wheel braking force upper limit value, and rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and front wheels of the vehicle are braked based on the front wheel braking force setting value. Therefore, after the vehicle enters the comfortable braking mode, the front wheel braking force or the rear wheel braking force is distributed according to the upper limit value of the wheel braking force, so that the braking force of the vehicle is distributed to the front wheels or the rear wheels as much as possible, vehicle pitching caused by braking is reduced, comfortable braking is achieved, and meanwhile the braking force of the vehicle cannot be reduced; the problem that the driving safety is low due to the fact that the braking force is reduced without considering the braking intention of a driver is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle control, and in particular to a vehicle braking method and related devices. Background Art

[0002] Braking refers to the action of stopping or slowing down a moving vehicle. For the driver, if the brake pedal cannot be properly controlled, the vehicle speed may drop to zero but the braking force is still large at the end of braking. At this time, the vehicle's pitch angle will change greatly, which is often called the "nodding" phenomenon of braking. This change in the vehicle body angle will eventually be transmitted to the driver and passengers. Due to inertia, the driver and passengers' bodies, especially the head, will change their front and rear tilt angles, causing discomfort.

[0003] In the related art, the commonly used braking strategy is to reduce the braking force setting value of the whole vehicle at the end of braking to reduce the braking force of the vehicle during braking, thereby reducing the pitch of the vehicle. However, the problem with this strategy is that the vehicle reduces the braking force regardless of the driver's braking intention, that is, the braking force of the vehicle during braking is reduced, which will increase the braking distance, that is, the under-braking phenomenon, giving the driver a feeling of "unable to brake", and it is more likely to cause traffic accidents, which is not conducive to driving safety. Summary of the invention

[0004] In view of the above problems, the present application provides a vehicle braking method and related devices, which are used to solve the problem of low driving safety caused by reducing the braking force regardless of the driver's braking intention.

[0005] Based on this, the embodiments of the present application disclose the following technical solutions:

[0006] On the one hand, an embodiment of the present application provides a braking method for a vehicle, the method comprising:

[0007] If the speed of the vehicle is less than a preset speed threshold, controlling the vehicle to enter a comfort braking mode;

[0008] In the comfort braking mode, obtaining the deceleration of the vehicle;

[0009] determining an upper limit value of wheel braking force according to the deceleration;

[0010] Determining a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, wherein the rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle;

[0011] The rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and the front wheels of the vehicle are braked based on the front wheel braking force setting value.

[0012] Optionally, determining the upper limit value of the wheel braking force according to the deceleration includes:

[0013] According to the deceleration, the upper limit of the wheel braking force is calculated, and the calculation formula is as follows:

[0014]

[0015] Among them, F r is the upper limit of the wheel braking force; μ is the safety adhesion coefficient; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0016] Optionally, if the first ratio is less than the second ratio, the rear wheel braking force setting value is less than or equal to the wheel braking force upper limit value; if the first ratio is greater than the second ratio, the front wheel braking force setting value is less than or equal to the wheel braking force upper limit value;

[0017] The first ratio is the ratio between the tangent of the first angle and the torsional stiffness of the front suspension of the vehicle, the first angle being the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground, and the second ratio is the ratio between the tangent of the second angle and the torsional stiffness of the rear suspension of the vehicle, the second angle being the angle between the line connecting the instantaneous center of rotation of the rear suspension and the tire contact surface of the vehicle and the horizontal ground.

[0018] Optionally, if the first ratio is less than the second ratio, determining a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value includes:

[0019] Determining the wheel braking force upper limit value as the rear wheel braking force setting value;

[0020] determining a total braking force of the vehicle based on the deceleration;

[0021] The front wheel braking force setting value is determined according to the total braking force and the rear wheel braking force setting value.

[0022] Optionally, determining the wheel braking force upper limit value as the rear wheel braking force setting value includes:

[0023] Get the current rear wheel braking force value;

[0024] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is greater than or equal to a preset difference threshold, gradually adjusting the current rear wheel braking force value to the rear wheel braking force setting value within a preset time;

[0025] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is smaller than the preset difference threshold, the wheel braking force upper limit value is determined as the rear wheel braking force setting value.

[0026] Optionally, controlling the vehicle to enter a comfort braking mode includes:

[0027] If it is determined that the driver has a non-emergency braking intention or the deceleration is less than a preset deceleration threshold, the vehicle is controlled to enter a comfort braking mode.

[0028] Optionally, the method further includes:

[0029] If it is determined that the state of the vehicle satisfies an exit condition, controlling the vehicle to exit the comfort braking mode;

[0030] The exit conditions include determining that the driver has an emergency braking intention, determining that the driver has no braking intention, determining that the vehicle is in an unstable state, or that the vehicle speed is zero.

[0031] On the other hand, the present application provides a braking device for a vehicle, the device comprising: a control unit, an acquisition unit, a determination unit and a braking unit;

[0032] The control unit is used to control the vehicle to enter a comfort braking mode if the vehicle speed is less than a preset vehicle speed threshold;

[0033] The acquisition unit is used to acquire the deceleration of the vehicle in the comfort braking mode;

[0034] The determining unit is used to determine the upper limit value of the wheel braking force according to the deceleration;

[0035] The determining unit is further used to determine a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, wherein the rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle;

[0036] The brake unit is used to brake the rear wheels of the vehicle based on the rear wheel braking force setting value, and to brake the front wheels of the vehicle based on the front wheel braking force setting value.

[0037] Optionally, the determining unit is specifically configured to:

[0038] According to the deceleration, the upper limit of the wheel braking force is calculated, and the calculation formula is as follows:

[0039]

[0040] Among them, F r is the upper limit of the wheel braking force; μ is the safety adhesion coefficient; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0041] Optionally, if the first ratio is less than the second ratio, the rear wheel braking force setting value is less than or equal to the wheel braking force upper limit value; if the first ratio is greater than the second ratio, the front wheel braking force setting value is less than or equal to the wheel braking force upper limit value;

[0042] The first ratio is the ratio between the tangent of the first angle and the torsional stiffness of the front suspension of the vehicle, the first angle is the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground, and the second ratio is the ratio between the tangent of the second angle and the torsional stiffness of the rear suspension of the vehicle, the second angle is the angle between the line connecting the instantaneous center of rotation of the rear suspension and the tire contact surface of the vehicle and the horizontal ground.

[0043] Optionally, if the first ratio is less than the second ratio, the determining unit is specifically configured to:

[0044] Determining the wheel braking force upper limit value as the rear wheel braking force setting value;

[0045] determining a total braking force of the vehicle based on the deceleration;

[0046] The front wheel braking force setting value is determined according to the total braking force and the rear wheel braking force setting value.

[0047] Optionally, the determining unit is specifically configured to:

[0048] Get the current rear wheel braking force value;

[0049] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is greater than or equal to a preset difference threshold, gradually adjusting the current rear wheel braking force value to the rear wheel braking force setting value within a preset time;

[0050] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is smaller than the preset difference threshold, the wheel braking force upper limit value is determined as the rear wheel braking force setting value.

[0051] Optionally, the control unit is specifically used to:

[0052] If it is determined that the driver has a non-emergency braking intention or the deceleration is less than a preset deceleration threshold, the vehicle is controlled to enter a comfort braking mode.

[0053] Optionally, the control unit is further used to:

[0054] If it is determined that the state of the vehicle satisfies an exit condition, controlling the vehicle to exit the comfort braking mode;

[0055] The exit conditions include determining that the driver has an emergency braking intention, determining that the driver has no braking intention, determining that the vehicle is in an unstable state, or that the vehicle speed is zero.

[0056] In another aspect, the present application provides a computer device, the device comprising a processor and a memory:

[0057] The memory is used to store program code and transmit the program code to the processor;

[0058] The processor is used to execute the method described in the above aspects according to the instructions in the program code.

[0059] On the other hand, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method described in the above aspects.

[0060] On the other hand, an embodiment of the present application provides a computer program product or a computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the method described in the above aspects.

[0061] The advantages of the above technical solution of this application are:

[0062] If the vehicle speed is less than the preset speed threshold, the vehicle is controlled to enter the comfort braking mode. In the comfort braking mode, the vehicle's deceleration is obtained, and the upper limit of the wheel braking force is determined based on the deceleration. According to the upper limit of the wheel braking force, the rear wheel braking force setting value and the front wheel braking force setting value are determined, and the rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and the front wheels of the vehicle are braked based on the front wheel braking force setting value. Therefore, after the vehicle enters the comfort braking mode, the front wheel braking force or the rear wheel braking force is allocated according to the upper limit of the wheel braking force, so that the braking force of the vehicle is allocated to the front wheel or the rear wheel as much as possible, thereby reducing the pitch of the vehicle caused by braking, achieving comfortable braking, and not reducing the braking force of the vehicle, avoiding the problem of low driving safety due to reducing the braking force regardless of the driver's braking intention. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0064] Figure 1 A flowchart of a vehicle braking method provided in an embodiment of the present application;

[0065] Figure 2 A schematic diagram of a vehicle torque provided in an embodiment of the present application;

[0066] Figure 3 A schematic diagram of the relationship between a deceleration value and a rear wheel braking force distribution ratio provided in an embodiment of the present application;

[0067] Figure 4 A schematic diagram of a braking device for a vehicle provided in an embodiment of the present application;

[0068] Figure 5 A structural diagram of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0069] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0070] In order to avoid the problem of discomfort caused by the change of the front and rear tilt angle of the driver and passengers' bodies, especially the head, due to inertia during the vehicle braking process, the concept of comfortable braking is proposed. In the related art, in order to achieve comfortable braking, the generally adopted comfortable braking strategy is to reduce the braking force setting value of the whole vehicle at the end of braking to reduce the braking force during the vehicle braking process, thereby reducing the pitch degree of the vehicle. However, the problem with this comfortable braking strategy is that the vehicle reduces the braking force regardless of the driver's braking intention, that is, the braking force of the vehicle during the braking process is reduced, which will increase the braking distance, that is, the under-braking phenomenon, giving the driver a feeling of "unable to brake", and it is more likely to cause traffic accidents, which is not conducive to driving safety.

[0071] In order not to reduce the braking force setting value and avoid giving the driver an illusion, braking can be achieved by combining software and hardware. Taking a vehicle with energy recovery function as an example, when the driver brakes at low speed, the energy recovery function will be entered, and the braking force generated after energy recovery will be applied to the rear wheels of the vehicle to achieve deceleration. However, when the vehicle speed is low, due to the low efficiency of energy recovery, the energy recovery function will be exited. At this time, the braking force of the whole vehicle will be generated by clamping braking force (that is, the traditional method of clamping the brake disc with a brake caliper). After the source of the braking force is switched, the pitch angle of the vehicle will also change, causing discomfort to the driver and passengers.

[0072] After research, it was found that due to the limitations of existing hardware and software strategies, the braking force setting values ​​will be equally distributed to the front and rear wheels of the vehicle. The clamping braking force will act on the front and rear wheels, causing the braking force acting on the front wheels to increase relatively, while the braking force acting on the rear wheels to decrease relatively. This unreasonable distribution of braking force leads to changes in the vehicle's pitch angle and a "vehicle nodding problem", which affects the comfort of the driver and passengers.

[0073] Based on this, an embodiment of the present application provides a vehicle braking method and related devices. After the vehicle enters the comfort braking mode, the front wheel braking force or the rear wheel braking force is allocated according to the upper limit value of the wheel braking force, so that the braking force of the vehicle is allocated to the front wheel or the rear wheel as much as possible, thereby reducing the vehicle pitch caused by braking, and achieving comfortable braking without reducing the braking force of the vehicle, thereby avoiding the problem of lower driving safety due to reducing the braking force regardless of the driver's braking intention.

[0074] Combine the following Figure 1 , a vehicle braking method provided in an embodiment of the present application is introduced. Figure 1 The method shown, in one implementation, may be executed by, for example, an electronic control unit (ECU) included in a vehicle. Figure 1, this figure is a flow chart of a vehicle braking method provided in an embodiment of the present application, and the method may include S101-S105.

[0075] S101: If the vehicle speed is less than a preset speed threshold, control the vehicle to enter a comfort braking mode.

[0076] During normal braking of the vehicle, the vehicle status can be continuously detected. If the vehicle speed is less than the preset speed threshold, the probability of the vehicle pitch angle change increases, thereby affecting the comfort of the driver and passengers or increasing the possibility of safety problems. For example, a vehicle with energy recovery function may exit the energy recovery function at low speed, resulting in a change in the vehicle pitch angle, which in turn affects the comfort of the driver and passengers. Based on this, if the vehicle speed is less than the preset speed threshold, the vehicle is controlled to enter the comfort braking mode, so that the comfort of the driver and passengers is not affected as much as possible without reducing the braking force setting value.

[0077] The embodiment of the present application does not specifically limit the value of the preset vehicle speed threshold, and those skilled in the art can set it according to actual needs. As a possible implementation, the current vehicle speed can be calculated based on signals collected by devices such as wheel speed sensors and inertial measurement units.

[0078] As a possible implementation method, in addition to controlling the vehicle to enter the comfort braking mode when the vehicle speed is less than a preset speed threshold, in order to ensure that the driver enters the comfort braking mode under safe conditions, the vehicle can also be controlled to enter the comfort braking mode when it is determined that the driver has non-emergency braking intentions and / or the deceleration is less than a preset deceleration threshold.

[0079] Among them, non-emergency braking intention means that the driver only has the intention to brake and is currently in a safe driving state, without the need for emergency braking, etc. As a possible implementation, it is possible to determine whether the driver has the intention to brake based on the brake pedal movement stroke and / or pressure signal collected by the sensor for the brake pedal.

[0080] If the deceleration is less than the preset deceleration threshold, the driver can avoid the situation where he needs to brake urgently, which proves that he is in a safe driving state. As a possible implementation method, the deceleration can be limited not only to be less than the preset deceleration threshold, but also to be greater than the preset deceleration threshold, that is, the deceleration is limited to a given range, because if the deceleration is too small, the vehicle may not nod, and there is no need to enter the comfort braking mode. As a possible implementation method, the current acceleration of the vehicle can be calculated based on the signals collected by the wheel speed sensor, inertial measurement unit and other equipment. The vehicle deceleration is the negative value of the vehicle acceleration.

[0081] Therefore, based on two or three judgment conditions, the current complex vehicle condition can be judged more accurately, so that the vehicle can safely enter the comfort braking mode.

[0082] In addition, if it is determined that the state of the vehicle meets the exit condition, the vehicle is controlled to exit the comfort braking mode. The exit condition includes determining that the driver has an emergency braking intention, determining that the driver has no braking intention, determining that the vehicle is in an unstable state or the vehicle speed is zero.

[0083] The driver's emergency braking intention means that the driver needs emergency braking in an unsafe situation, and the vehicle's deceleration may be higher than that of a non-emergency braking intention. As a possible implementation, the brake pedal movement stroke and / or pressure signal collected by the sensor for the brake pedal can be used to determine whether the driver has an emergency braking intention. It is understandable that when the driver has an emergency braking intention, the collected brake pedal movement stroke and / or pressure signal will be greater.

[0084] The driver's lack of braking intention means that the driver may not need to brake, and the vehicle does not need to be in the comfort braking mode and can exit. As a possible implementation, it is possible to determine whether the driver has an emergency braking intention based on the brake pedal movement stroke and / or pressure signal collected by a sensor for the brake pedal.

[0085] The vehicle is in an unstable state, including but not limited to the following functions being triggered: ABS (antilock brake system), EBD (Electronic Brake force Distribution), AYC (Active Yaw Control), etc.

[0086] When the vehicle speed is zero, it means that the vehicle has stopped. At this time, the vehicle does not need to be in the comfort braking mode and can exit. As a possible implementation, in order to avoid the vehicle not really stopping and not moving, the condition can be further limited to the vehicle speed being zero and maintained for a period of time. As a possible implementation, the vehicle speed can be calculated based on the signals collected by the wheel speed sensor, inertial measurement unit and other devices.

[0087] S102: In the comfort braking mode, obtain the deceleration of the vehicle.

[0088] S103: Determine the upper limit value of the wheel braking force according to the deceleration.

[0089] The wheel braking force upper limit value refers to the front wheel braking force upper limit value or the rear wheel braking force upper limit value, which can be determined according to the structure of the vehicle.

[0090] If the first ratio is less than the second ratio, the upper limit of the wheel braking force is the upper limit of the rear wheel braking force; if the first ratio is greater than the second ratio, the upper limit of the wheel braking force is the upper limit of the front wheel braking force. The first ratio is the ratio between the tangent of the first angle and the torsional stiffness of the front suspension of the vehicle, the first angle being the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground, and the second ratio is the ratio between the tangent of the second angle and the torsional stiffness of the rear suspension of the vehicle, the second angle being the angle between the line connecting the instantaneous center of rotation of the rear suspension and the tire contact surface of the vehicle and the horizontal ground. The following is expressed based on the formula:

[0091]

[0092]

[0093] Among them, tanθ f is the tangent value of the first angle, θ f k is the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground; f is the torsional stiffness of the vehicle’s front suspension; is the first ratio; tanθ r is the tangent value of the second angle, θ r k is the angle between the line connecting the instantaneous center of rotation of the rear suspension and the contact surface of the tire of the vehicle and the horizontal ground; r is the torsional stiffness of the rear suspension of the vehicle; is the second ratio.

[0094] If formula (1) is satisfied, the first ratio is less than the second ratio, and the upper limit value of the wheel braking force is the upper limit value of the rear wheel braking force; if formula (2) is satisfied, the first ratio is greater than the second ratio, and the upper limit value of the wheel braking force is the upper limit value of the front wheel braking force.

[0095] For the convenience of explanation, the following explanation is given by taking the case where formula (1) is satisfied.

[0096] The axle load transfer during braking will cause the positive pressure of the rear wheel to drop, and the excessive braking force of the rear wheel will further increase the possibility of rear wheel locking, affecting driving safety. Based on this, the embodiment of the present application proposes an upper limit value of wheel braking force, that is, in the comfort braking mode, the braking force should be distributed to the rear wheel as much as possible, that is, the clamping force generated by the rear wheel brake caliper should be increased as much as possible, and the clamping force generated by the front wheel brake caliper should be reduced as much as possible, but the braking force acting on the rear wheel cannot be increased infinitely to ensure that the rear wheel will not lock.

[0097] Based on this, if the first ratio is less than the second ratio, that is, formula (1) is satisfied, the rear wheel braking force setting value is less than or equal to the wheel braking force upper limit value; if the first ratio is greater than the second ratio, that is, formula (2) is satisfied, the front wheel braking force setting value is less than or equal to the wheel braking force upper limit value. In this way, the comfort of the driver and passengers can be increased without changing the driver's braking intention, while ensuring that the vehicle braking force is not weakened, thereby improving the vehicle driving experience and driving safety.

[0098] It should be noted that when When the rear wheel braking force is set to a value less than or equal to the upper limit of the wheel braking force, the front wheel braking force may be set to a value less than or equal to the upper limit of the wheel braking force, and the embodiment of the present application does not make any specific limitation on this.

[0099] As a possible implementation method, the upper limit of the wheel braking force can be calculated according to the deceleration, and the calculation formula is as follows:

[0100]

[0101] Among them, F r is the upper limit of wheel braking force; μ is the safety adhesion coefficient; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0102] The safety adhesion coefficient can be the road adhesion coefficient or can be determined based on the road adhesion coefficient. Taking the safety adhesion coefficient determined based on the road adhesion coefficient as an example, assuming that the road adhesion coefficient is μ0 at this time, it can be estimated in real time by the ECU. In order to leave a certain safety margin, it can be multiplied by a safety factor k greater than 0 and less than or equal to 1, where k is a calibrable parameter, to obtain the safety adhesion coefficient μ=kμ0.

[0103] During braking, axle load transfer occurs due to vehicle deceleration. Figure 2 , which is a schematic diagram of a vehicle torque provided by an embodiment of the present application. Taking the front wheel as the rotation center, based on the torque balance, it can be obtained:

[0104] mga=F z,r L+md x h (4)

[0105]

[0106] Among them, F z,r is the vertical pressure on the rear wheel; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d xis the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0107] At this time, the maximum friction force that the rear wheel can generate with the ground, that is, the maximum braking force that the rear wheel can generate, can be expressed as

[0108]

[0109] Among them, F r is the upper limit of wheel braking force; μ is the safety adhesion coefficient; F z,r is the vertical pressure on the rear wheel; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0110] S104: Determine a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value.

[0111] The rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle.

[0112] Continue to see Figure 2 , in order to produce the required deceleration, the total braking force of the vehicle can be expressed as:

[0113] F=md x (7)

[0114] Where F is the total braking force of the vehicle; m is the mass of the vehicle; d x For deceleration.

[0115] In order to conveniently explain how to determine the rear wheel braking force setting value and the front wheel braking force setting value, the rear wheel braking force distribution ratio is introduced for explanation below. Wherein, the rear wheel braking force distribution ratio = rear wheel braking force upper limit value / total braking force.

[0116]

[0117] Among them, λ is the rear wheel braking force distribution ratio; F r is the upper limit of wheel braking force; F is the total braking force of the vehicle; μ is the safety adhesion coefficient; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0118] It can be seen that the λ value is between 0 and 1. The larger the value, the greater the braking force allowed to be allocated to the rear wheels. Conversely, the smaller the braking force allowed to be allocated to the rear wheels, the smaller the braking force ratio. Based on this, the upper limit of the wheel braking force can be determined as the rear wheel braking force setting value; the total braking force of the vehicle can be determined according to the deceleration; and the front wheel braking force setting value can be determined according to the total braking force and the rear wheel braking force setting value.

[0119] See also Figure 3 , which is a schematic diagram of the relationship between the deceleration value and the rear wheel braking force distribution ratio provided by an embodiment of the present application. Figure 3 In the figure, taking a certain vehicle model as an example, it includes the rear wheel braking force distribution ratio λ curve corresponding to different safety adhesion coefficients μ, the horizontal axis is the deceleration value, and the vertical axis is the rear wheel braking force distribution ratio. When the comfort braking function is activated, the rear wheel braking force distribution ratio can be selected / changed below the corresponding curve according to the change of real-time vehicle deceleration without affecting vehicle safety (the shaded area in the figure taking μ=0.6 as an example), and the larger the λ value, the higher the braking comfort.

[0120] As a possible implementation method, the instantaneous change of braking force will also lead to unreasonable distribution of braking force, resulting in changes in the vehicle pitch angle and the "vehicle nodding problem", which affects the comfort of the driver and passengers. Based on this, the front wheel braking force setting value and the rear wheel braking force setting value can be slowly adjusted to avoid instantaneous changes in braking force.

[0121] Specifically, the current rear wheel braking force value is obtained; if the difference between the current rear wheel braking force value and the rear wheel braking force setting value is greater than or equal to the preset difference threshold, it means that if the current rear wheel braking force value is directly adjusted to the rear wheel braking force setting value, the braking force will change instantly, the vehicle pitch angle will change, and the "vehicle nodding problem" will occur, affecting the comfort of the driver and passengers. Therefore, the current rear wheel braking force value can be gradually adjusted to the rear wheel braking force setting value within a preset time, that is, the current rear wheel braking force value is slowly controlled to become the rear wheel braking force setting value to avoid instantaneous changes in braking force. In addition, if the difference between the current rear wheel braking force value and the rear wheel braking force setting value is less than the preset difference threshold, it means that there will be no instantaneous change in braking force at present, and the wheel braking force upper limit value is determined as the rear wheel braking force setting value, and the adjustment is made directly.

[0122] S105: Braking the rear wheels of the vehicle based on the rear wheel braking force setting value, and braking the front wheels of the vehicle based on the front wheel braking force setting value.

[0123] It can be seen from the above technical solution that if the speed of the vehicle is less than the preset speed threshold, the vehicle is controlled to enter the comfort braking mode. In the comfort braking mode, the deceleration of the vehicle is obtained, and the upper limit of the wheel braking force is determined based on the deceleration. According to the upper limit of the wheel braking force, the rear wheel braking force setting value and the front wheel braking force setting value are determined, and the rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and the front wheels of the vehicle are braked based on the front wheel braking force setting value. Therefore, after the vehicle enters the comfort braking mode, the front wheel braking force or the rear wheel braking force is allocated according to the upper limit of the wheel braking force, so that the braking force of the vehicle is allocated to the front wheel or the rear wheel as much as possible, thereby reducing the pitch of the vehicle caused by braking, achieving comfortable braking, and not reducing the braking force of the vehicle, avoiding the problem of low driving safety due to reducing the braking force regardless of the driver's braking intention.

[0124] In addition to the vehicle braking method provided in the embodiment of the present application, a vehicle braking device is also provided, such as Figure 4 As shown, it includes: a control unit 401, an acquisition unit 402, a determination unit 403 and a braking unit 404;

[0125] The control unit 401 is used to control the vehicle to enter a comfort braking mode if the vehicle speed is less than a preset vehicle speed threshold;

[0126] The acquisition unit 402 is used to acquire the deceleration of the vehicle in the comfort braking mode;

[0127] The determining unit 403 is used to determine the upper limit value of the wheel braking force according to the deceleration;

[0128] The determining unit 403 is further configured to determine a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, wherein the rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle;

[0129] The brake unit 404 is used to brake the rear wheels of the vehicle based on the rear wheel braking force setting value, and to brake the front wheels of the vehicle based on the front wheel braking force setting value.

[0130] It can be seen from the above technical solution that if the speed of the vehicle is less than the preset speed threshold, the vehicle is controlled to enter the comfort braking mode. In the comfort braking mode, the deceleration of the vehicle is obtained, and the upper limit of the wheel braking force is determined based on the deceleration. According to the upper limit of the wheel braking force, the rear wheel braking force setting value and the front wheel braking force setting value are determined, and the rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and the front wheels of the vehicle are braked based on the front wheel braking force setting value. Therefore, after the vehicle enters the comfort braking mode, the front wheel braking force or the rear wheel braking force is allocated according to the upper limit of the wheel braking force, so that the braking force of the vehicle is allocated to the front wheel or the rear wheel as much as possible, thereby reducing the pitch of the vehicle caused by braking, achieving comfortable braking, and not reducing the braking force of the vehicle, avoiding the problem of low driving safety due to reducing the braking force regardless of the driver's braking intention.

[0131] As a possible implementation manner, the determining unit 403 is specifically configured to:

[0132] According to the deceleration, the upper limit of the wheel braking force is calculated, and the calculation formula is as follows:

[0133]

[0134] Among them, F r is the upper limit of the wheel braking force; μ is the safety adhesion coefficient; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

[0135] As a possible implementation, if the first ratio is less than the second ratio, the rear wheel braking force setting value is less than or equal to the wheel braking force upper limit value; if the first ratio is greater than the second ratio, the front wheel braking force setting value is less than or equal to the wheel braking force upper limit value;

[0136] The first ratio is the ratio between the tangent of the first angle and the torsional stiffness of the front suspension of the vehicle, the first angle is the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground, and the second ratio is the ratio between the tangent of the second angle and the torsional stiffness of the rear suspension of the vehicle, the second angle is the angle between the line connecting the instantaneous center of rotation of the rear suspension and the tire contact surface of the vehicle and the horizontal ground.

[0137] As a possible implementation manner, if the first ratio is less than the second ratio, the determining unit 403 is specifically configured to:

[0138] Determining the wheel braking force upper limit value as the rear wheel braking force setting value;

[0139] determining a total braking force of the vehicle based on the deceleration;

[0140] The front wheel braking force setting value is determined according to the total braking force and the rear wheel braking force setting value.

[0141] As a possible implementation manner, the determining unit 403 is specifically configured to:

[0142] Get the current rear wheel braking force value;

[0143] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is greater than or equal to a preset difference threshold, gradually adjusting the current rear wheel braking force value to the rear wheel braking force setting value within a preset time;

[0144] If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is smaller than the preset difference threshold, the wheel braking force upper limit value is determined as the rear wheel braking force setting value.

[0145] As a possible implementation manner, the control unit 401 is specifically configured to:

[0146] If it is determined that the driver has a non-emergency braking intention or the deceleration is less than a preset deceleration threshold, the vehicle is controlled to enter a comfort braking mode.

[0147] As a possible implementation manner, the control unit 401 is further configured to:

[0148] If it is determined that the state of the vehicle satisfies an exit condition, controlling the vehicle to exit the comfort braking mode;

[0149] The exit conditions include determining that the driver has an emergency braking intention, determining that the driver has no braking intention, determining that the vehicle is in an unstable state, or that the vehicle speed is zero.

[0150] The present application also provides a computer device, see Figure 5 , which shows a structural diagram of a computer device provided in an embodiment of the present application, such as Figure 5 As shown, the device includes a memory 510 and a processor 520:

[0151] The memory 510 is used to store program codes and transmit the program codes to the processor;

[0152] The processor 520 is used to execute any one of the vehicle braking methods provided in the above embodiments according to the instructions in the program code.

[0153] An embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program, wherein the computer program is used to execute any one of the vehicle braking methods provided in the above embodiments.

[0154] The embodiment of the present application also provides a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. The processor of the computer device reads the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes the vehicle braking method provided in various optional implementations of the above aspects.

[0155] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0156] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0157] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0158] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0159] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vehicle braking method, characterized in that: The method comprises: If the speed of the vehicle is less than a preset speed threshold, controlling the vehicle to enter a comfort braking mode; In the comfort braking mode, obtaining the deceleration of the vehicle; determining an upper limit value of wheel braking force according to the deceleration; Determining a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, wherein the rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle; The rear wheels of the vehicle are braked based on the rear wheel braking force setting value, and the front wheels of the vehicle are braked based on the front wheel braking force setting value.

2. The method according to claim 1, characterized in that Determining the upper limit value of the wheel braking force according to the deceleration includes: According to the deceleration, the upper limit of the wheel braking force is calculated, and the calculation formula is as follows: Among them, F r is the upper limit of the wheel braking force; μ is the safety adhesion coefficient; m is the mass of the vehicle; g is the acceleration of gravity; a is the distance between the front axle of the vehicle and the center of gravity of the vehicle; d x is the deceleration; h is the distance between the center of gravity and the ground; L is the distance between the front wheels of the vehicle and the rear wheels of the vehicle.

3. The method according to claim 1, characterized in that If the first ratio is less than the second ratio, the rear wheel braking force setting value is less than or equal to the wheel braking force upper limit value; if the first ratio is greater than the second ratio, the front wheel braking force setting value is less than or equal to the wheel braking force upper limit value; The first ratio is the ratio between the tangent of the first angle and the torsional stiffness of the front suspension of the vehicle, the first angle being the angle between the line connecting the instantaneous center of rotation of the front suspension and the tire contact surface of the vehicle and the horizontal ground, and the second ratio is the ratio between the tangent of the second angle and the torsional stiffness of the rear suspension of the vehicle, the second angle being the angle between the line connecting the instantaneous center of rotation of the rear suspension and the tire contact surface of the vehicle and the horizontal ground.

4. The method according to claim 3, characterized in that If the first ratio is less than the second ratio, determining a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, including: Determining the wheel braking force upper limit value as the rear wheel braking force setting value; determining a total braking force of the vehicle based on the deceleration; The front wheel braking force setting value is determined according to the total braking force and the rear wheel braking force setting value.

5. The method according to claim 3, characterized in that: The step of determining the wheel braking force upper limit value as the rear wheel braking force setting value comprises: Get the current rear wheel braking force value; If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is greater than or equal to a preset difference threshold, gradually adjusting the current rear wheel braking force value to the rear wheel braking force setting value within a preset time; If the difference between the current rear wheel braking force value and the rear wheel braking force setting value is smaller than the preset difference threshold, the wheel braking force upper limit value is determined as the rear wheel braking force setting value.

6. The method according to any one of claims 1 to 5, characterized in that: The controlling the vehicle to enter a comfort braking mode comprises: If it is determined that the driver has a non-emergency braking intention or the deceleration is less than a preset deceleration threshold, the vehicle is controlled to enter a comfort braking mode.

7. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: If it is determined that the state of the vehicle satisfies an exit condition, controlling the vehicle to exit the comfort braking mode; The exit conditions include determining that the driver has an emergency braking intention, determining that the driver has no braking intention, determining that the vehicle is in an unstable state, or that the vehicle speed is zero.

8. A braking device for a vehicle, characterized in that: The device comprises: a control unit, an acquisition unit, a determination unit and a braking unit; The control unit is used to control the vehicle to enter a comfort braking mode if the vehicle speed is less than a preset vehicle speed threshold; The acquisition unit is used to acquire the deceleration of the vehicle in the comfort braking mode; The determining unit is used to determine the upper limit value of the wheel braking force according to the deceleration; The determining unit is further used to determine a rear wheel braking force setting value and a front wheel braking force setting value according to the wheel braking force upper limit value, wherein the rear wheel braking force setting value is a braking force value set for the rear wheels of the vehicle, and the front wheel braking force setting value is a braking force value set for the front wheels of the vehicle; The brake unit is used to brake the rear wheels of the vehicle based on the rear wheel braking force setting value, and to brake the front wheels of the vehicle based on the front wheel braking force setting value.

9. A computer device, characterized in that: The device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the method according to any one of claims 1 to 7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method according to any one of claims 1 to 7.

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