CN114715087A - Automatic braking method, device and system for vehicle and storage medium - Google Patents

Automatic braking method, device and system for vehicle and storage medium Download PDF

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Publication number
CN114715087A
CN114715087A CN202110004846.2A CN202110004846A CN114715087A CN 114715087 A CN114715087 A CN 114715087A CN 202110004846 A CN202110004846 A CN 202110004846A CN 114715087 A CN114715087 A CN 114715087A
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vehicle
current
deceleration
current vehicle
braking
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CN114715087B (en
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郑志晓
梁伟强
林志超
蔡璐珑
王博
钟国旗
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Guangzhou Automobile Group Co Ltd
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Guangzhou Automobile Group Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T7/00—Brake-action initiating means
    • B60T7/12—Brake-action initiating means for automatic initiation; for initiation not subject to will of driver or passenger
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T2201/00—Particular use of vehicle brake systems; Special systems using also the brakes; Special software modules within the brake system controller
    • B60T2201/02—Active or adaptive cruise control system; Distance control
    • B60T2201/022—Collision avoidance systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

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  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Regulating Braking Force (AREA)

Abstract

The invention discloses an automatic braking method, a device, a system and a storage medium of a vehicle, wherein the method comprises the following steps: calculating the collision time and the predicted relative distance between the current vehicle and the target vehicle; judging whether the current running state of the vehicle is a driver braking state or not; when a first braking condition is met, braking the brake actuator according to the current running speed of the current vehicle; when a second braking condition is met, if the predicted relative distance is larger than the safety distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a braking actuator of the current vehicle according to the required deceleration; and when the collision time is not more than the third collision time, braking the brake actuator according to the maximum deceleration which can be executed by the brake actuator of the current vehicle. The invention can adjust the braking deceleration according to the actual vehicle running condition by avoiding the mutual drag of the primary braking and the secondary braking, thereby improving the safety of the braking process.

Description

Automatic braking method, device and system for vehicle and storage medium
Technical Field
The invention relates to the technical field of control of vehicle driving systems, in particular to an automatic braking method, device and system of a vehicle and a storage medium.
Background
The automobile with the forward collision avoidance system can calculate the collision time of the automobile in the driving process, and realize the automatic braking of the automobile according to the collision time, thereby avoiding the condition that a driver reacts or the braking is not timely.
At present, a common driving assistance function forward collision avoidance system includes both an early warning and an automatic emergency braking function. The common automatic emergency braking is open-loop braking, each stage of braking judges whether a braking triggering condition is met or not according to TTC (Time to Collision Time), each stage of braking deceleration is set as a fixed value, and the safe distance is controlled by calibrating and triggering the TTC. However, in the conventional braking system, the brakes of the respective stages are mutually restrained, and the braking deceleration of the respective stages is a fixed value, so that it is difficult to satisfy the actual braking condition.
Disclosure of Invention
Embodiments of the present invention provide an automatic braking method, apparatus, system and storage medium for a vehicle, which can adjust a braking deceleration according to an actual vehicle running condition by avoiding mutual drag between primary braking and secondary braking, thereby improving safety during a braking process.
An embodiment of the present invention provides an automatic braking method for a vehicle, including:
calculating the collision time and the predicted relative distance between the current vehicle and a target vehicle;
acquiring the running state of a current vehicle, and judging whether the running state of the current vehicle is a driver braking state or not;
when a first braking condition is met, sending a corresponding deceleration instruction to a braking actuator of the current vehicle according to the current running speed of the current vehicle; wherein the first braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a first collision time;
when a second braking condition is met, if the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration; wherein the second braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a second collision time; the second collision time is less than the first collision time and greater than a third collision time;
and when the collision time is not more than the third collision time, sending a corresponding deceleration instruction to the brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle.
As an improvement of the above scheme, the method further comprises the following steps:
when the current driving state of the vehicle is a driver braking state, executing the following steps:
judging whether the current running speed of the current vehicle is greater than a first running speed threshold value or not;
when the current running speed of the current vehicle is not greater than a first running speed threshold and the predicted relative distance is greater than a safe distance threshold, not braking;
when the current running speed of the current vehicle is larger than a first running speed threshold value, the collision time is not larger than a second collision time, and the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration.
As an improvement of the above, the calculating of the collision time of the current vehicle with the target vehicle includes:
acquiring the current running speed of the current vehicle, and acquiring the current running speed of the target vehicle and the running state of the target vehicle;
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle and the running state of the target vehicle is a decelerating state, calculating the collision time by:
Figure BDA0002882806990000031
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle and the running state of the target vehicle is not a decelerating state, calculating the collision time by:
Figure BDA0002882806990000032
when the current running speed of the current vehicle is not greater than the current running speed of the target vehicle, making the collision time TTC';
in the formula, vsv1Is the current running speed, v, of the current vehicleto1Is the current running speed of the target vehicle, SrelIs a current predicted relative distance between the current vehicle and the target vehicle, ato1TTC' is a preset time-to-collision calibration value, which is the current rate of change of the speed of the target vehicle.
As an improvement of the above aspect, when the second braking condition is satisfied, the method further includes:
acquiring a current deceleration of the current vehicle;
when the current speed change rate of the current vehicle is smaller than a preset deceleration state threshold value, judging that the running state of the current vehicle is a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle to be 0;
when the current speed change rate of the current vehicle is not less than a preset deceleration state threshold value, judging that the running state of the current vehicle is not a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle, wherein the braking delay time is not 0;
when the braking delay time is not 0, calculating first predicted travel distances of the current vehicle and the target vehicle, respectively, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the first predicted travel distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a first predicted relative distance;
wherein the first predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000041
calculating a first predicted travel distance of the target vehicle by:
Figure BDA0002882806990000042
calculating the first expected relative distance by:
Srel_1＝Sto1－Ssv1+Srel
in the formula, asv1Is the current speed change rate, t, of the current vehicledelayFor said braking delay time, Ssv1Is a first predicted travel distance, S, of the current vehicleto1Is a first predicted travel distance, S, of the target vehiclerel_1Is a first predicted relative distance between the current vehicle and the target vehicle.
As an improvement of the above solution, when the braking delay time is 0 and the current deceleration of the current vehicle is increased incrementally, a deceleration value corresponding to a deceleration command of a previous period is used as an initial deceleration, and the incremental deceleration is calculated according to the initial deceleration;
calculating second predicted travel distances of the current vehicle and the target vehicle, respectively, according to the incremental decelerations, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the second predicted travel distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a second predicted relative distance;
wherein the incremental deceleration is calculated by the initial deceleration according to:
decelt1＝min(decelt0+b，decelmax/2)
in the formula, decelt1For increasing deceleration, decelt0For initial deceleration, decelmaxA maximum deceleration performable for a brake actuator of the current vehicle; b is incremental change when decelt0When b is 0, let b be decel max2, when decelt0When not equal to 0, order
Figure BDA0002882806990000051
Wherein m is an integer, and j is a deceleration change rate; when the current deceleration of the current vehicle is smaller than the initial deceleration decelt0When j is>0; when the current deceleration of said current vehicle is equal to said initial deceleration decelt0When j is 0; when the current deceleration of the current vehicle is larger than the initial deceleration decelt0When j is<0；
Calculating a second predicted distance traveled by the current vehicle during the deceleration increment by:
Figure BDA0002882806990000052
calculating a second predicted distance traveled by the target vehicle during the deceleration increment by:
Figure BDA0002882806990000053
calculating a second predicted relative distance between the current vehicle and the target vehicle by:
Srel_2＝Sto2－Ssv2+Srel
in the formula, asv1Is the current speed change rate, t, of the current vehicledelayFor said braking delay time, t2Increment time for deceleration, and
Figure BDA0002882806990000054
Ssv2a second predicted travel distance, S, for the current vehicleto2A second predicted travel distance, S, for the target vehiclerel_2Is a second predicted relative distance between the current vehicle and the target vehicle.
As an improvement of the above scheme, the method further comprises the following steps:
when the braking delay time is 0 and the deceleration change rate is 0, calculating third traveling distances of the current vehicle and the target vehicle, respectively, according to the incremental deceleration, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the third predicted traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a third predicted relative distance;
wherein the third predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000061
calculating a third predicted travel distance of the target vehicle by:
Figure BDA0002882806990000062
calculating the travel time of the current vehicle at the incremental deceleration by:
Figure BDA0002882806990000063
calculating a third predicted relative distance between the current vehicle and the target vehicle by:
Srel_3＝Sto3－Ssv3+Srel
in the formula, t3For the current vehicle travel time at the incremental deceleration, Ssv3A third predicted travel distance, S, for the current vehicleto3A third predicted travel distance, S, for the target vehiclerel_3A third predicted relative distance between the current vehicle and the target vehicle.
As an improvement of the above scheme, the method further comprises the following steps:
and when the predicted relative distance is larger than a safe distance threshold value, taking the incremental deceleration as the required deceleration, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration.
As an improvement of the above scheme, the method further comprises the following steps: the second collision time is greater than a third collision time;
the third collision time is obtained according to the current running speed of the current vehicle and the target vehicle;
wherein the third collision time is calculated by:
Figure BDA0002882806990000064
in the formula, TTCthreshold_3Is the third collision time.
Another embodiment of the present invention correspondingly provides an automatic braking device for a vehicle, including:
the parameter calculation module is used for calculating the collision time and the predicted relative distance between the current vehicle and the target vehicle;
the state acquisition module is used for acquiring the running state of the current vehicle and judging whether the running state of the current vehicle is the driver braking state or not;
a brake control module to:
when a first braking condition is met, sending a corresponding deceleration instruction to a braking actuator of the current vehicle according to the current running speed of the current vehicle; wherein the first braking condition comprises that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a first collision time;
when a second braking condition is met, if the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration; wherein the second braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a second collision time; the second collision time is less than the first collision time and greater than a third collision time;
and when the collision time is not more than the third collision time, sending a corresponding deceleration command to the brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle.
Another embodiment of the present invention provides a control system of an autonomous vehicle, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the method of automatic braking of a vehicle according to the above embodiment of the invention when executing the computer program.
Another embodiment of the present invention provides a storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the automatic braking method for a vehicle according to the above-described embodiment of the present invention.
Compared with the prior art, in the embodiment of the invention, the driving state of the vehicle is judged by the depth of the brake pedal and the pressure of the brake master cylinder together, so that the misjudgment of the braking state of a driver is avoided; under the condition that the vehicle is not in a driver braking state, the collision time of the current vehicle and the previous vehicle, namely the target vehicle is calculated, so that the braking condition can be obtained in time, and the safety and timeliness of automatic braking are improved; the first-level open-loop braking is triggered when the collision time is not more than the first collision time, and the corresponding first deceleration instruction is sent to the brake actuator of the current vehicle according to the current running speed of the current vehicle, so that the shock and the danger caused by over-high deceleration or unnecessary emergency braking are avoided, the safety of vehicle braking is improved, and the comfort of a driver and other passengers can be improved; the secondary closed-loop control is triggered when the collision time is not more than the second collision time, and the braking deceleration is calculated in real time according to the states of the current vehicle and the target vehicle, so that the decoupling of primary braking and secondary braking is realized, the triggering time is not mutually restrained, the braking deceleration is adjusted according to the actual vehicle running condition, and the safety of the braking process is further improved; through the judgment of the safe collision distance, when the predicted relative distance is still larger than the safe distance threshold value, the time for carrying out deceleration according to the vehicle speed is still available at present, and the required deceleration of the current vehicle can be calculated according to the predicted relative distance, the vehicle speed of the current vehicle, the vehicle speed of the target vehicle and other parameters; under the condition that the vehicle is in a driver braking state, the braking behavior of the driver is considered, and braking control assistance is not provided for the driver who takes braking measures as far as possible under a low-speed scene; when collision is about to occur, the vehicle is braked to stop by the maximum braking force, so that safe braking is realized on the premise of ensuring the safety and comfort of a driver and other passengers.
Drawings
FIG. 1 is a schematic flow chart illustrating an automatic braking method for a vehicle according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a specific control process of an automatic braking method for a vehicle according to an embodiment of the invention;
FIG. 3 is a schematic diagram of a secondary braking control process of an automatic braking method for a vehicle according to an embodiment of the present invention;
fig. 4 is a schematic structural view of an automatic brake device of a vehicle according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a control system of an autonomous vehicle according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
referring to fig. 1, a schematic flow chart of an automatic braking method for a vehicle according to an embodiment of the present invention is shown.
The automatic braking method of the vehicle provided by the embodiment can be executed by an automatic braking control end. In this embodiment, the autobrake control end is preferably a control system for autobraking a vehicle, and may also be a cloud server, and the like, and the control system may be implemented in a software and/or hardware manner, and may be formed by two or more physical entities, or may be formed by one physical entity.
Further, the control system can acquire vehicle running state information such as speed, acceleration, vehicle braking state, and the like transmitted from each running state information generating device of the vehicle. In addition, the various information may be directly transmitted to the control system, or may be transmitted to another information processing apparatus, processed by the information processing apparatus, and then transmitted to the control system.
Specifically, referring to fig. 1, the automatic braking method of a vehicle includes steps S101 to S105:
s101, calculating the collision time and the predicted relative distance between the current vehicle and the target vehicle;
the method comprises the steps of calculating the collision time and the predicted relative distance between the current vehicle and the front vehicle (namely the target vehicle), obtaining the braking condition in time, and improving the safety and timeliness of automatic braking.
S102, acquiring the running state of the current vehicle, and judging whether the running state of the current vehicle is the braking state of a driver;
specifically, the running state of the current vehicle is acquired by: acquiring the current depth of a vehicle brake pedal and the pressure of a brake master cylinder; judging whether the depth of the brake pedal is higher than a preset pedal depth threshold value or not, and judging whether the pressure of a brake master cylinder is higher than a preset pressure threshold value or not; when the depth of the brake pedal is higher than a preset pedal depth threshold value, and the pressure of the brake master cylinder is higher than a preset pressure threshold value and is maintained for a certain time, judging that a driver takes a braking measure, namely the current running state of the vehicle is a driver braking state; otherwise, the driver is judged to take no braking measures, namely the current running state of the vehicle is not the driver braking state.
The driving state of the vehicle is judged through the depth of the brake pedal and the pressure of the brake master cylinder, so that the situation that a driver takes brake measures at the moment can be ensured, the vehicle receives a brake instruction and starts to brake, the misjudgment of the brake state of the driver is avoided, and the stability of automatic braking is improved.
It should be noted that, it is a preferable mode in this embodiment to obtain whether the current vehicle is in the driver braking state according to the depth of the brake pedal, the pressure of the brake master cylinder, or other existing modes.
When the running state of the current vehicle is not the driver braking state, the driver is indicated to fail to brake or brake in time, and at the moment, the braking condition can be timely obtained by calculating the collision time and the predicted relative distance between the two vehicles, so that the safety and timeliness of automatic braking are improved.
S103, when a first braking condition is met, sending a corresponding deceleration instruction to a braking actuator of the current vehicle according to the current running speed of the current vehicle; the first braking condition comprises that the current running state of the vehicle is not a driver braking state and the collision time is not more than first collision time;
when the collision time is not greater than the first collision time, the emergency degree of the current vehicle braking is low, so that a corresponding appropriate braking deceleration request can be sent to the brake actuator according to the running speed of the current vehicle. Specifically, the braking deceleration may be set as a one-dimensional table linearly interpolated according to the vehicle speed, and the table may empirically calibrate the first time to collision TTCthreshold_1Etc., and are not particularly limited herein. By performing adaptive automatic braking when the collision time is not greater than the first collision time, startle and danger due to too fast deceleration or unnecessary emergency braking are avoided, safety of vehicle braking is improved, and comfort of drivers and other passengers can be improved.
S104, when a second braking condition is met, if the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to the brake actuator of the current vehicle according to the required deceleration; the second braking condition comprises that the current running state of the vehicle is not a driver braking state and the collision time is not more than second collision time; the second collision time is less than the first collision time and greater than the third collision time;
and when the second collision time is not more than the first collision time, the urgency degree of braking of the current vehicle is increased, namely, the vehicle needs to be further braked according to the predicted relative distance. The emergency degree judgment of braking is realized by judging the collision time, so that the braking safety can be improved, and the traditional secondary braking can be decoupled; if the collision time is not more than the first collision time, the condition that the collision time is not more than the second collision time is used as a secondary brake, the primary brake is a primary open-loop brake for deceleration, the triggering time and the deceleration can be calibrated according to experience, the secondary brake is a secondary closed-loop brake for collision avoidance and safe distance control, the triggering time can be calibrated but not less than the time required for collision avoidance, and the brake deceleration is calculated in real time according to the states of the current vehicle and the target vehicle; therefore, the decoupling of the primary braking and the secondary braking can be realized, the trigger time is not mutually restrained, the braking deceleration is adjusted according to the actual vehicle running condition, and the safety of the braking process is further improved.
The second collision time is smaller than the first collision time and larger than the third collision time, and the second collision time is set in the range, so that the problem that the brake is too late due to the fact that the collision time is too small can be avoided.
When the predicted relative distance is still larger than the safety distance threshold value, the time for decelerating according to the vehicle speed still exists at present, and the required deceleration of the current vehicle can be calculated according to the parameters of the predicted relative distance, the vehicle speed of the current vehicle, the vehicle speed of the target vehicle and the like; on the contrary, if the predicted relative distance is not greater than the safety distance threshold, it indicates that the current vehicle needs emergency braking, and therefore, a corresponding deceleration command needs to be sent to the brake actuator of the current vehicle according to the maximum deceleration that can be executed by the brake actuator of the current vehicle, so that the actuator decelerates at the maximum deceleration that can be realized by the actuator; therefore, the safety brake is realized on the premise of ensuring the safety and comfort of the driver and other passengers.
Specifically, the expected relative distance between the current vehicle and the target vehicle can be calculated in real time in the running process of the current vehicle, and whether the expected relative distance is greater than the safety distance threshold value or not can be judged in real time, so that emergency braking can be realized in time, and the safety of the current vehicle in the running process can be ensured.
S105, when the collision time is not more than the third collision time, sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle;
for example, referring to fig. 2, when the collision time is not greater than the third collision time, which indicates that the braking urgency of the current vehicle is the greatest at the time when the collision is about to occur, braking is required according to the greatest maximum deceleration performable by the brake actuator of the current vehicle so as to avoid the collision with the preceding vehicle.
In this embodiment, it is preferable to further include: when the current driving state of the vehicle is a driver braking state, executing the following steps:
judging whether the current running speed of the current vehicle is greater than a first running speed threshold value or not;
when the current running speed of the current vehicle is not greater than the first running speed threshold value and the predicted relative distance is greater than the safe distance threshold value, braking is not carried out;
and when the current running speed of the current vehicle is greater than the first running speed threshold, the collision time is not greater than the second collision time and the predicted relative distance is greater than the safe distance threshold, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration command to a brake actuator of the current vehicle according to the required deceleration.
For example, referring to fig. 2, when the current driving state of the vehicle is not the driver braking state, it is determined that the driver has not taken a braking measure, it is determined whether the collision time is greater than a first collision time, and it is determined that the primary open-loop braking is triggered when the collision time is not greater than the first collision time; along with the continuous running of the vehicle, if the collision time of the current vehicle and the front vehicle is reduced and is less than the second collision time, triggering secondary closed-loop braking; and in the braking process, judging whether the predicted relative distance is larger than a safe distance threshold value or not, if not, judging that the collision is about to occur at the moment, and controlling a brake actuator to brake with the maximum braking force.
For example, referring to fig. 2, when the current driving state of the vehicle is the driver braking state, it is determined that the driver has taken a braking measure, at this time, it is determined whether the current driving scene is a low-speed driving scene or not by the current driving speed of the current vehicle and the first driving speed threshold value, and if the current driving speed is not greater than the first driving speed threshold value, it is determined that the current driving scene is a low-speed driving scene, and automatic braking is not performed; if the vehicle is not in a low-speed driving scene, a secondary closed-loop braking link is started, so that the collision accident caused by insufficient deceleration controlled by a driver to avoid collision is avoided.
Specifically, in consideration of the braking behavior of the driver, in the case where the driver has taken a braking measure and is traveling at a low speed, the driver who has taken a braking measure is not provided with braking control assistance as much as possible, the driving experience of the driver is prevented from being affected, and when a collision is about to occur, the vehicle is braked to a stop with a maximum braking force.
In this embodiment, preferably, the calculating of the collision time of the current vehicle with the target vehicle includes:
acquiring the current running speed of a current vehicle, and acquiring the current running speed of a target vehicle and the running state of the target vehicle;
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle, and the running state of the target vehicle is a decelerated state, the collision time is calculated by:
Figure BDA0002882806990000131
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle, and the running state of the target vehicle is not a decelerating state, calculating a collision time by:
Figure BDA0002882806990000132
when the current running speed of the current vehicle is not greater than the current running speed of the target vehicle, enabling the collision time to be TTC';
in the formula, vsv1Is the current running speed, v, of the current vehicleto1Is the current running speed of the target vehicle, SrelFor the current expected relative distance between the current vehicle and the target vehicle, ato1TTC' is a preset time-to-collision calibration value, which is the current rate of change of the speed of the target vehicle.
Specifically, if the target vehicle has started decelerating, ato1＜-1.0m/s2。
Specifically, a proper time to collision TTC is selected according to the current running speeds of the current vehicle and the target vehicle and the current speed change of the target vehicle, and if the calculated time to collision is greater than a preset time to collision calibration value TTC ', the preset time to collision calibration value TTC' is selected as the time to collision TTC, so that emergency braking time in an emergency situation is reserved; for the same reason, when the current running speed of the current vehicle is not greater than the current running speed of the target vehicle, i.e., vsv1-vto1When the collision time is less than or equal to 0, the collision time is TTC'.
It should be noted that, in the above embodiment, the preset time to collision calibration value TTC' may be selected to be 10.0s, and may be set to be 10.5s, 11.0s, 12.0s, etc. according to the actual situation of the vehicle due to the difference between the driving system and the control system of the vehicle, which is only provided as an optional implementation manner and is not limited in particular.
In this embodiment, it is preferable that, when the second braking condition is satisfied, the method further includes:
acquiring a current deceleration of a current vehicle;
when the current speed change rate of the current vehicle is smaller than a preset deceleration state threshold value, judging that the running state of the current vehicle is a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle to be 0;
when the current speed change rate of the current vehicle is not less than a preset deceleration state threshold value, judging that the running state of the current vehicle is not a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle, wherein the braking delay time is not 0;
when the braking delay time is not 0, calculating first expected traveling distances of the current vehicle and the target vehicle respectively, and calculating an expected relative distance between the current vehicle and the target vehicle according to the first expected traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a first predicted relative distance;
wherein the first predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000141
calculating a first predicted travel distance of the target vehicle by:
Figure BDA0002882806990000151
calculating the first expected relative distance by:
Srel_1＝Sto1－Ssv1+Srel
in the formula, asv1Is the current rate of change, t, of the current speed of the vehicledelayFor brake delay time, Ssv1Is a first predicted travel distance, S, of the current vehicleto1Is a first predicted travel distance, S, of the target vehiclerel_1Is a first expected relative distance between the current vehicle and the target vehicle.
For example, referring to fig. 3, since it is determined that the braking delay time is not 0 when the traveling state of the current vehicle is not the decelerating state, it can be understood that when the braking delay time is not 0, that is, the host vehicle has not decelerated; calculating the predicted relative distance from the moment to the moment when the braking delay time is over according to the speed and the speed change rate of the current vehicle and the target vehicle, judging whether the predicted relative distance is greater than the safe distance when the braking delay time is over, and if the predicted relative distance is less than the safe distance when the braking delay time is over, braking according to the executable maximum deceleration of a brake actuator to avoid collision accidents; if not, decelt1As current vehiclesDeceleration on demand, according to decelt1And sending a corresponding second deceleration command to a brake actuator of the current vehicle, and further ensuring the riding experience of a driver and passengers on the premise of ensuring safe braking.
In the present embodiment, preferably, when the braking delay time is 0 and the current deceleration of the current vehicle is incremented, a deceleration value corresponding to the deceleration command of the previous cycle is taken as the initial deceleration, and the incremented deceleration is calculated from the initial deceleration;
calculating second predicted travel distances of the current vehicle and the target vehicle, respectively, based on the incremental decelerations, and calculating a predicted relative distance between the current vehicle and the target vehicle based on the second predicted travel distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a second predicted relative distance;
wherein the incremental deceleration is calculated by the initial deceleration according to:
decelt1＝min(decelt0+b，decelmax/2)
in the formula, decelt1For increasing deceleration, decelt0For initial deceleration, decelmaxA maximum deceleration performable for a brake actuator of the current vehicle; b is incremental change when decelt0When b is 0, let b be decelmax2, when decelt0When not equal to 0, order
Figure BDA0002882806990000161
Wherein m is an integer, and j is a deceleration change rate; when the current deceleration of the current vehicle is smaller than the initial deceleration decelt0When j is>0; when the current deceleration of the current vehicle is equal to the initial deceleration decelt0When j is 0; when the current deceleration of the current vehicle is larger than the initial deceleration decelt0When j is<0；
Calculating a second predicted distance traveled by the current vehicle during the deceleration increment by:
Figure BDA0002882806990000162
calculating a second predicted travel distance of the target vehicle during the deceleration increment by:
Figure BDA0002882806990000163
calculating a second predicted relative distance between the current vehicle and the target vehicle by:
Srel_2＝Sto2－Ssv2+Srel
in the formula, asv1Is the current rate of change, t, of the current speed of the vehicledelayFor brake delay time, t2Increment time for deceleration, and
Figure BDA0002882806990000164
Ssv2is the second predicted travel distance, S, of the current vehicleto2Is the second predicted travel distance, S, of the target vehiclerel_2A second predicted relative distance between the current vehicle and the target vehicle.
For example, referring to fig. 3, since the braking delay time is set to 0 when it is determined that the current running state of the vehicle is the decelerating state, it can be understood that when the braking delay time is 0, that is, the host vehicle is already in the decelerating state; an incremental deceleration decel is now assumedt1Let the deceleration increase decelt1And if the sum of the initial deceleration and the incremental increment is greater than half of the maximum deceleration which can be executed by the brake actuator of the current vehicle, the value is half of the maximum deceleration which can be executed by the brake actuator of the current vehicle. By
Figure BDA0002882806990000165
It can be known that t2The period, i.e., the deceleration rising period, the deceleration change rate j may be taken according to the actual test result of the vehicle. When t is acquired2After the predicted relative distance of the deceleration rising period, judging whether the predicted relative distance is larger than the safe distance when the deceleration rising period is ended, if so, judging that the predicted relative distance is smaller than the safe distanceFull distance, then, t is stated2The deceleration in the period is not enough to ensure that the vehicle cannot generate collision accidents after being braked, therefore, the vehicle is braked according to the executable maximum deceleration of the brake actuator to avoid the collision accidents, if the deceleration is not less than the maximum deceleration, decel is carried outt1As demanded deceleration of the present vehicle, according to decelt1And sending a corresponding second deceleration command to a brake actuator of the current vehicle, and further ensuring the riding experience of a driver and passengers on the premise of ensuring safe braking.
In this embodiment, it is preferable to further include:
when the braking delay time is 0 and the deceleration change rate is 0, respectively calculating third traveling distances of the current vehicle and the target vehicle according to the incremental deceleration, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the third predicted traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a third predicted relative distance;
wherein the third predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000171
calculating a third predicted travel distance of the target vehicle by:
Figure BDA0002882806990000172
the travel time of the current vehicle at the incremental deceleration is calculated by:
Figure BDA0002882806990000173
calculating a third predicted relative distance between the current vehicle and the target vehicle by:
Srel_3＝Sto3－Ssv3+Srel
in the formula，t3For the current travel time of the vehicle at increasing deceleration, Ssv3Is the third predicted travel distance of the current vehicle, Sto3Is the third predicted travel distance, S, of the target vehiclerel_3A third predicted relative distance between the current vehicle and the target vehicle.
Exemplarily, see fig. 3, if t2The expected relative distance expected at the end of the period is still not less than the safe distance, indicating that the vehicle is stable at this deceleration to decelt1Can still avoid collision accidents during the period; t is t3After the period ends, the deceleration of the current vehicle reaches the incremental deceleration decelt1When the deceleration stabilization period is started; calculating decelt1The running time of the vehicle under deceleration, thereby obtaining the running time t of the current vehicle under the increasing deceleration3Predicted relative distance of and then judging t3Whether the predicted relative distance is larger than the safety distance or not, if so, the stable deceleration is not enough to ensure that no collision accident occurs after the vehicle is braked, and therefore, the vehicle is braked according to the executable maximum deceleration of the brake actuator to avoid the collision accident; if not, decelt1As demanded deceleration of the present vehicle, according to decelt1And sending a corresponding second deceleration command to a brake actuator of the current vehicle, and further ensuring the riding experience of a driver and passengers on the premise of ensuring safe braking.
In the present embodiment, it is preferable that when the predicted relative distance is greater than the safe distance threshold, the incremental deceleration is taken as the required deceleration, and a corresponding deceleration command is sent to the brake actuator of the present vehicle in accordance with the required deceleration.
In the present embodiment, it is preferable that the third collision time is derived from a current running speed of the current vehicle and the target vehicle;
wherein the third collision time is calculated by:
Figure BDA0002882806990000181
in the formula (I), the compound is shown in the specification,TTCthreshold_3is the third collision time.
Specifically, when the collision time is less than the third collision time, the maximum braking deceleration decel is usedmaxBraking to vehicle stop or brake deceleration limit; otherwise, maintaining the current braking deceleration; therefore, the double limits of the predicted relative distance and the collision time are realized, and meanwhile, the comfort and the safety of a driver and other passengers as well as the timeliness and the safety of braking are ensured.
Further, if the current time to collision TTC satisfies the following equation, it is determined that a collision is imminent:
Figure BDA0002882806990000191
in the formula, a mode that the collision time is the minimum value of 0.2s and the third collision time is adopted, a time limit of 0.2s is reserved for emergency braking, and the braking timeliness is further improved. It should be noted that 0.2s is only one preferable value provided in the present embodiment, and in a specific embodiment, may be set to 0.3s, 0.35s, and the like according to the actual vehicle condition of the vehicle, and is not limited specifically herein.
In conclusion, in the embodiment of the invention, the driving state of the vehicle is judged by the depth of the brake pedal and the pressure of the brake master cylinder together, so that the misjudgment of the braking state of the driver is avoided; under the condition that the vehicle is not in a driver braking state, the collision time of the current vehicle and the previous vehicle, namely the target vehicle is calculated, so that the braking condition can be obtained in time, and the safety and timeliness of automatic braking are improved; the first-level open-loop braking is triggered when the collision time is not more than the first collision time, and the corresponding first deceleration instruction is sent to the brake actuator of the current vehicle according to the current running speed of the current vehicle, so that the startle and the danger caused by over-high deceleration or unnecessary emergency braking are avoided, the safety of vehicle braking is improved, and the comfort of a driver and other passengers can be improved; the secondary closed-loop control is triggered when the collision time is not more than the second collision time, and the braking deceleration is calculated in real time according to the states of the current vehicle and the target vehicle, so that the decoupling of primary braking and secondary braking is realized, the triggering time is not mutually restrained, the braking deceleration is adjusted according to the actual vehicle running condition, and the safety of the braking process is further improved; through the judgment of the safe collision distance, when the predicted relative distance is still larger than the safe distance threshold value, the time for decelerating according to the vehicle speed still exists at present, and the required deceleration of the current vehicle can be calculated according to the parameters such as the predicted relative distance, the vehicle speed of the current vehicle, the vehicle speed of the target vehicle and the like; under the condition that the vehicle is in a driver braking state, the braking behavior of the driver is considered, and braking control assistance is not provided for the driver who takes braking measures as far as possible under a low-speed scene; when collision is about to occur, the vehicle is braked to stop by the maximum braking force, so that safe braking is realized on the premise of ensuring the safety and comfort of a driver and other passengers.
The second embodiment:
referring to fig. 4, a schematic structural diagram of an automatic braking device for a vehicle according to an embodiment of the present invention is shown, including:
a parameter calculation module 201, configured to calculate a collision time and a predicted relative distance between a current vehicle and a target vehicle;
the state acquisition module 202 is configured to acquire a driving state of a current vehicle and determine whether the driving state of the current vehicle is a driver braking state;
a brake control module 203 for:
when a first braking condition is met, sending a corresponding deceleration instruction to a braking actuator of the current vehicle according to the current running speed of the current vehicle; the first braking condition comprises that the current running state of the vehicle is not a driver braking state and the collision time is not more than first collision time;
when a second braking condition is met, if the predicted relative distance is greater than a safe distance threshold, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to the brake actuator of the current vehicle according to the required deceleration; the second braking condition comprises that the current running state of the vehicle is not a driver braking state and the collision time is not more than second collision time; the second collision time is less than the first collision time and greater than the third collision time;
and when the collision time is not more than the third collision time, sending a corresponding deceleration command to the brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle.
Further, still include: when the current driving state of the vehicle is a driver braking state, executing the following steps:
judging whether the current running speed of the current vehicle is greater than a first running speed threshold value or not;
when the current running speed of the current vehicle is not greater than the first running speed threshold value and the predicted relative distance is greater than the safe distance threshold value, braking is not carried out;
and when the current running speed of the current vehicle is greater than the first running speed threshold, the collision time is not greater than the second collision time and the predicted relative distance is greater than the safe distance threshold, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration command to a brake actuator of the current vehicle according to the required deceleration.
Further, calculating a time of collision of the current vehicle with the target vehicle includes:
acquiring the current running speed of a current vehicle, and acquiring the current running speed of a target vehicle and the running state of the target vehicle;
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle, and the running state of the target vehicle is a decelerated state, the collision time is calculated by:
Figure BDA0002882806990000211
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle, and the running state of the target vehicle is not a decelerating state, calculating a collision time by:
Figure BDA0002882806990000212
when the current running speed of the current vehicle is not greater than the current running speed of the target vehicle, enabling the collision time to be TTC';
in the formula, vsv1Is the current running speed, v, of the current vehicleto1Is the current running speed of the target vehicle, SrelFor the current expected relative distance between the current vehicle and the target vehicle, ato1TTC' is a preset time-to-collision calibration value, which is the current rate of change of the speed of the target vehicle.
Further, when the second braking condition is satisfied, the method further comprises the following steps:
acquiring a current deceleration of a current vehicle;
when the current speed change rate of the current vehicle is smaller than a preset deceleration state threshold value, judging that the running state of the current vehicle is a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle to be 0;
when the current speed change rate of the current vehicle is not less than a preset deceleration state threshold value, judging that the running state of the current vehicle is not a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle, wherein the braking delay time is not 0;
when the braking delay time is not 0, calculating first expected traveling distances of the current vehicle and the target vehicle respectively, and calculating an expected relative distance between the current vehicle and the target vehicle according to the first expected traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a first predicted relative distance;
wherein the first predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000221
calculating a first predicted travel distance of the target vehicle by:
Figure BDA0002882806990000222
calculating the first expected relative distance by:
Srel_1＝Sto1－Ssv1+Srel
in the formula, asv1Is the current rate of change, t, of the current speed of the vehicledelayFor brake delay time, Ssv1Is a first predicted travel distance, S, of the current vehicleto1Is a first predicted travel distance, S, of the target vehiclerel_1Is a first expected relative distance between the current vehicle and the target vehicle.
Further, when the braking delay time is 0 and the current deceleration of the current vehicle is increased progressively, the deceleration value corresponding to the deceleration command of the previous period is used as the initial deceleration, and the incremental deceleration is calculated according to the initial deceleration;
calculating second predicted travel distances of the current vehicle and the target vehicle, respectively, based on the incremental decelerations, and calculating a predicted relative distance between the current vehicle and the target vehicle based on the second predicted travel distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a second predicted relative distance;
wherein the incremental deceleration is calculated by the initial deceleration according to:
decelt1＝min(decelt0+b，decelmax/2)
in the formula, decelt1For increasing deceleration, decelt0For initial deceleration, decelmaxA maximum deceleration performable for a brake actuator of the current vehicle; b is incremental change when decelt0When b is equal to 0, let b be decelmax2, when decelt0When not equal to 0, order
Figure BDA0002882806990000231
Wherein m isInteger, j is the deceleration rate of change; when the current deceleration of the current vehicle is smaller than the initial deceleration decelt0When j is>0; when the current deceleration of the current vehicle is equal to the initial deceleration decelt0When j is 0; when the current deceleration of the current vehicle is larger than the initial deceleration decelt0When j is<0；
Calculating a second predicted distance traveled by the current vehicle during the deceleration increment by:
Figure BDA0002882806990000232
calculating a second predicted travel distance of the target vehicle during the deceleration increment by:
Figure BDA0002882806990000233
calculating a second predicted relative distance between the current vehicle and the target vehicle by:
Srel_2＝Sto2－Ssv2+Srel
in the formula, asv1Is the current rate of change, t, of the current speed of the vehicledelayFor brake delay time, t2Increment time for deceleration, and
Figure BDA0002882806990000234
Ssv2is the second predicted travel distance, S, of the current vehicleto2Is the second predicted travel distance, S, of the target vehiclerel_2A second predicted relative distance between the current vehicle and the target vehicle.
Further, when the braking delay time is 0 and the deceleration change rate is 0, calculating third traveling distances of the current vehicle and the target vehicle, respectively, based on the incremental decelerations, and calculating a predicted relative distance between the current vehicle and the target vehicle based on the third predicted traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a third predicted relative distance;
wherein the third predicted travel distance of the current vehicle is calculated by:
Figure BDA0002882806990000241
calculating a third predicted travel distance of the target vehicle by:
Figure BDA0002882806990000242
the travel time of the current vehicle at the incremental deceleration is calculated by:
Figure BDA0002882806990000243
calculating a third predicted relative distance between the current vehicle and the target vehicle by:
Srel_3＝Sto3－Ssv3+Srel
in the formula, t3For the current travel time of the vehicle at increasing deceleration, Ssv3Is the third predicted travel distance, S, of the current vehicleto3Is the third predicted travel distance, S, of the target vehiclerel_3A third predicted relative distance between the current vehicle and the target vehicle.
Further, still include:
and when the predicted relative distance is larger than the safe distance threshold value, taking the incremental deceleration as the required deceleration, and sending a corresponding deceleration command to the brake actuator of the current vehicle according to the required deceleration.
Further, the third collision time is obtained according to the current running speed of the current vehicle and the target vehicle;
wherein the third collision time is calculated by:
Figure BDA0002882806990000244
in the formula, TTCthreshold_3Is the third collision time.
In conclusion, in the embodiment of the invention, the driving state of the vehicle is judged by the depth of the brake pedal and the pressure of the brake master cylinder, so that the misjudgment of the braking state of the driver is avoided; under the condition that the vehicle is not in a driver braking state, the collision time of the current vehicle and the previous vehicle, namely the target vehicle is calculated, so that the braking condition can be obtained in time, and the safety and timeliness of automatic braking are improved; the first-level open-loop braking is triggered when the collision time is not more than the first collision time, and the corresponding first deceleration instruction is sent to the brake actuator of the current vehicle according to the current running speed of the current vehicle, so that the shock and the danger caused by over-high deceleration or unnecessary emergency braking are avoided, the safety of vehicle braking is improved, and the comfort of a driver and other passengers can be improved; the secondary closed-loop control is triggered when the collision time is not more than the second collision time, and the braking deceleration is calculated in real time according to the states of the current vehicle and the target vehicle, so that the decoupling of primary braking and secondary braking is realized, the triggering time is not mutually restrained, the braking deceleration is adjusted according to the actual vehicle running condition, and the safety of the braking process is further improved; through the judgment of the safe collision distance, when the predicted relative distance is still larger than the safe distance threshold value, the time for carrying out deceleration according to the vehicle speed is still available at present, and the required deceleration of the current vehicle can be calculated according to the predicted relative distance, the vehicle speed of the current vehicle, the vehicle speed of the target vehicle and other parameters; under the condition that the vehicle is in a driver braking state, the braking behavior of the driver is considered, and braking control assistance is not provided for the driver who takes braking measures as far as possible under a low-speed scene; when collision is about to occur, the vehicle is braked to stop by the maximum braking force, so that safe braking is realized on the premise of ensuring the safety and comfort of a driver and other passengers.
Example three:
referring to fig. 5, a schematic diagram of a control system of an autonomous vehicle according to an embodiment of the present invention is shown. The control system of the autonomous vehicle of the embodiment includes: a processor 1, a memory 2 and a computer program stored in said memory 2 and operable on said processor, such as an autobrake program of a vehicle. The processor 1, when executing the computer program, implements the steps in the above-described respective embodiments of the automatic braking method for a vehicle. Alternatively, the processor 1 implements the functions of the modules/units in the above-mentioned device embodiments when executing the computer program.
Illustratively, the computer program may be partitioned into one or more modules/units that are stored in the memory and executed by the processor to implement the invention. The one or more modules/units may be a series of computer program instruction segments capable of performing specific functions for describing the execution of the computer program in the automatic braking device of the vehicle.
The control system of the autonomous vehicle may include, but is not limited to, a processor, a memory. It will be appreciated by those skilled in the art that the schematic diagram is merely an example of a control system for the autonomous vehicle and does not constitute a limitation of the control system for the autonomous vehicle, and may include more or fewer components than shown, or some components in combination, or different components, e.g., the control system for the autonomous vehicle may also include input-output devices, network access devices, a CAN bus, etc.
The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like that is the control center of the control system of the autonomous vehicle, with various interfaces and lines connecting the various parts of the control system of the entire autonomous vehicle.
The memory may be used to store the computer programs and/or modules, and the processor may implement various functions of the control system of the autonomous vehicle by running or executing the computer programs and/or modules stored in the memory and invoking data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data (such as audio data, a phonebook, etc.) created according to the use of the cellular phone, and the like. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.
Wherein the vehicle autobrake/control system integrated module/unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like. It should be noted that the computer readable medium may contain content that is subject to appropriate increase or decrease as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable media does not include electrical carrier signals and telecommunications signals as is required by legislation and patent practice.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (11)

1. An automatic braking method for a vehicle, characterized by comprising:
calculating the collision time and the predicted relative distance between the current vehicle and a target vehicle;
acquiring the running state of a current vehicle, and judging whether the running state of the current vehicle is a driver braking state or not;
when a first braking condition is met, sending a corresponding deceleration command to a braking actuator of the current vehicle according to the current running speed of the current vehicle; wherein the first braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a first collision time;
when a second braking condition is met, if the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration; wherein the second braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a second collision time; the second collision time is less than the first collision time and greater than a third collision time;
and when the collision time is not more than the third collision time, sending a corresponding deceleration command to the brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle.
2. The automatic braking method of a vehicle according to claim 1, characterized by further comprising: when the current driving state of the vehicle is a driver braking state, executing the following steps:
judging whether the current running speed of the current vehicle is greater than a first running speed threshold value or not;
when the current running speed of the current vehicle is not greater than a first running speed threshold and the predicted relative distance is greater than a safe distance threshold, not braking;
when the current running speed of the current vehicle is larger than a first running speed threshold value, the collision time is not larger than a second collision time, and the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration.
3. The automatic braking method of a vehicle according to claim 1, wherein the calculating of the time of collision of the current vehicle with a target vehicle includes:
acquiring the current running speed of the current vehicle, and acquiring the current running speed of the target vehicle and the running state of the target vehicle;
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle and the running state of the target vehicle is a decelerating state, calculating the collision time by:
Figure FDA0002882806980000021
when the current running speed of the current vehicle is greater than the current running speed of the target vehicle and the running state of the target vehicle is not a decelerating state, calculating the collision time by:
Figure FDA0002882806980000022
when the current running speed of the current vehicle is not greater than the current running speed of the target vehicle, enabling the collision time to be TTC';
in the formula, vsv1Is the current running speed, v, of the current vehicleto1Is the current running speed of the target vehicle, SrelIs a current predicted relative distance between the current vehicle and the target vehicle, ato1TTC' is a preset time-to-collision calibration value, which is the current rate of change of the speed of the target vehicle.
4. The automatic braking method of a vehicle according to claim 3, characterized by, when the second braking condition is satisfied, further comprising:
acquiring a current deceleration of the current vehicle;
when the current speed change rate of the current vehicle is smaller than a preset deceleration state threshold value, judging that the running state of the current vehicle is a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle to be 0;
when the current speed change rate of the current vehicle is not less than a preset deceleration state threshold value, judging that the running state of the current vehicle is not a deceleration state, and setting the braking delay time of a braking actuator of the current vehicle, wherein the braking delay time is not 0;
when the braking delay time is not 0, calculating first expected traveling distances of the current vehicle and the target vehicle respectively, and calculating an expected relative distance between the current vehicle and the target vehicle according to the first expected traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a first predicted relative distance;
wherein the first predicted travel distance of the current vehicle is calculated by:
Figure FDA0002882806980000031
calculating a first predicted travel distance of the target vehicle by:
Figure FDA0002882806980000032
calculating the first expected relative distance by:
Srel_1＝Sto1－Ssv1+Srel
in the formula, asv1Is the current speed change rate, t, of the current vehicledelayFor said braking delay time, Ssv1Is a first predicted travel distance, S, of the current vehicleto1Is a first predicted travel distance, S, of the target vehiclerel_1Is a first predicted relative distance between the current vehicle and the target vehicle.
5. The automatic braking method of a vehicle according to claim 4, characterized by further comprising:
when the braking delay time is 0 and the current deceleration of the current vehicle is increased progressively, taking the deceleration value corresponding to the deceleration instruction of the previous period as the initial deceleration, and calculating the incremental deceleration according to the initial deceleration;
calculating second predicted travel distances of the current vehicle and the target vehicle, respectively, according to the incremental decelerations, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the second predicted travel distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a second predicted relative distance;
wherein the incremental deceleration is calculated by the initial deceleration according to:
decelt1＝min(decelt0+b，decelmax/2)
in the formula, decelt1For increasing deceleration, decelt0For initial deceleration, decelmaxA maximum deceleration performable for a brake actuator of the current vehicle; b is incremental change when decelt0When b is 0, let b be decelmax2, when decelt0When not equal to 0, order
Figure FDA0002882806980000041
Wherein m is an integer, and j is a deceleration change rate; when the current deceleration of the current vehicle is smaller than the initial deceleration decelt0When j is>0; when the current deceleration of said current vehicle is equal to said initial deceleration decelt0When j is 0; when the current deceleration of the current vehicle is larger than the initial deceleration decelt0When j is<0；
Calculating a second predicted distance traveled by the current vehicle during the deceleration increment by:
Figure FDA0002882806980000042
calculating a second predicted distance traveled by the target vehicle during the deceleration increment by:
Figure FDA0002882806980000043
calculating a second predicted relative distance between the current vehicle and the target vehicle by:
Srel_2＝Sto2－Ssv2+Srel
in the formula, asv1Is the current speed change rate, t, of the current vehicledelayFor said braking delay time, t2Increment time for deceleration, and
Figure FDA0002882806980000051
Ssv2a second predicted distance to travel for the current vehicle, Sto2A second predicted travel distance, S, for the target vehiclerel_2Is a second predicted relative distance between the current vehicle and the target vehicle.
6. The automatic braking method of a vehicle according to claim 5, characterized by further comprising:
when the braking delay time is 0 and the deceleration change rate is 0, calculating third traveling distances of the current vehicle and the target vehicle, respectively, according to the incremental deceleration, and calculating a predicted relative distance between the current vehicle and the target vehicle according to the third predicted traveling distances of the current vehicle and the target vehicle; wherein the predicted relative distance is a third predicted relative distance;
wherein the third predicted travel distance of the current vehicle is calculated by:
Figure FDA0002882806980000052
calculating a third predicted travel distance of the target vehicle by:
Figure FDA0002882806980000053
calculating the travel time of the current vehicle at the incremental deceleration by:
Figure FDA0002882806980000054
calculating a third predicted relative distance between the current vehicle and the target vehicle by:
Srel_3＝Sto3－Ssv3+Srel
in the formula, t3For the current vehicle travel time at the incremental deceleration, Ssv3A third predicted travel distance, S, for the current vehicleto3A third predicted travel distance, S, for the target vehiclerel_3A third predicted relative distance between the current vehicle and the target vehicle.
7. The automatic braking method of a vehicle according to any one of claims 5 to 6, characterized by further comprising:
and when the predicted relative distance is larger than a safe distance threshold value, taking the incremental deceleration as the required deceleration, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration.
8. The automatic braking method of a vehicle according to claim 1, characterized in that the third collision time is obtained from a current traveling speed of the current vehicle and the target vehicle;
wherein the third collision time is calculated by:
Figure FDA0002882806980000061
in the formula, TTCthreshold_3Is the third collision time.
9. An automatic brake device for a vehicle, characterized by comprising:
the parameter calculation module is used for calculating the collision time and the predicted relative distance between the current vehicle and the target vehicle;
the state acquisition module is used for acquiring the running state of the current vehicle and judging whether the running state of the current vehicle is the driver braking state or not;
a brake control module to:
when a first braking condition is met, sending a corresponding deceleration command to a braking actuator of the current vehicle according to the current running speed of the current vehicle; wherein the first braking condition comprises that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a first collision time;
when a second braking condition is met, if the predicted relative distance is larger than a safe distance threshold value, calculating the required deceleration of the current vehicle according to the predicted relative distance, and sending a corresponding deceleration instruction to a brake actuator of the current vehicle according to the required deceleration; wherein the second braking condition includes that the driving state of the current vehicle is not a driver braking state and the collision time is not greater than a second collision time; the second collision time is less than the first collision time and greater than a third collision time;
and when the collision time is not more than the third collision time, sending a corresponding deceleration instruction to the brake actuator of the current vehicle according to the executable maximum deceleration of the brake actuator of the current vehicle.
10. A control system for an autonomous vehicle, comprising a processor, a memory and a computer program stored in the memory and configured to be executed by the processor, the processor when executing the computer program implementing an automatic braking method for a vehicle as claimed in any one of claims 1 to 8.
11. A computer-readable storage medium, comprising a stored computer program, wherein the computer program, when executed, controls an apparatus in which the computer-readable storage medium is located to perform the method for automatic braking of a vehicle according to any one of claims 1 to 8.
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