阅读说明：本技术 一种车速确定方法及装置、设备、介质 (Vehicle speed determination method and device, equipment and medium ) 是由 徐显杰 张金广 袁丹阳 于 2021-03-23 设计创作，主要内容包括：本发明公开了一种车速确定方法及装置、设备、介质。所述车速确定方法包括：获取上一时刻速度、当前时刻车辆的制动加速度、当前时刻与上一时刻的时间差,以及当前时刻的仪表显示车速；根据上一时刻速度、当前时刻车辆的制动加速度以及当前时刻与上一时刻的时间差,确定当前时刻车辆的估算速度；采用互补滤波法融合估算速度和当前时刻的仪表显示车速,获得当前时刻车辆的车速。本发明实施例提供的技术方案,提高了自动紧急制动过程中车速确定的准确性。(The invention discloses a vehicle speed determination method, a vehicle speed determination device, vehicle speed determination equipment and a vehicle speed determination medium. The vehicle speed determination method includes: acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment, and the instrument display speed at the current moment; determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment; and fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment. According to the technical scheme provided by the embodiment of the invention, the accuracy of determining the vehicle speed in the automatic emergency braking process is improved.)

1. A vehicle speed determination method for determining vehicle speed in real time during automatic emergency braking of a vehicle, comprising:

acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment, and the instrument display speed at the current moment;

determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

2. The vehicle speed determination method according to claim 1, wherein fusing the estimated speed and the meter display vehicle speed at the present time using a complementary filtering method includes:

acquiring prestored radar speed measurement data;

determining a vehicle speed fusion coefficient according to the radar speed measurement data, the estimated speed and the instrument display vehicle speed;

and fusing the estimated speed and the instrument display speed by adopting the vehicle speed fusion coefficient.

3. The vehicle speed determination method according to claim 1, wherein obtaining the braking acceleration of the vehicle at the present time includes:

acquiring the linear acceleration of the vehicle at the current moment;

acquiring the attitude angle of the vehicle at the current moment;

and obtaining the braking acceleration without the gravity component according to the attitude angle and the linear acceleration.

4. The vehicle speed determination method according to claim 3, characterized in that obtaining the attitude angle of the vehicle at the present time includes:

acquiring angular velocity acquired by a gyroscope and linear acceleration acquired by an accelerometer at the current moment;

obtaining an attitude angle variable according to the angular velocity;

obtaining a first attitude angle of the vehicle according to the attitude angle variable and the attitude angle of the vehicle at the previous moment;

obtaining a second attitude angle of the vehicle according to the linear acceleration;

and acquiring the attitude angle of the vehicle at the current moment according to the first attitude angle and the second attitude angle by adopting a preset rule.

5. The vehicle speed determination method according to claim 4, after acquiring the angular velocity acquired by the gyroscope and the linear acceleration acquired by the accelerometer at the current time, further comprising:

denoising the angular velocity acquired by the gyroscope by adopting a moving average filtering method;

and denoising the linear acceleration acquired by the accelerometer by adopting a Kalman filtering method.

6. The vehicle speed determination method according to claim 4, wherein obtaining the attitude angle of the vehicle at the current time from the first attitude angle and the second attitude angle using a preset rule includes:

acquiring a first modulus value of triaxial acceleration according to linear acceleration acquired by an accelerometer at the current moment;

acquiring a second modulus value of the acceleration which is coaxial with the current attitude angle;

determining that the first modulus value is in a first preset range and the second modulus value is in a second preset range, and fusing the first attitude angle and the second attitude angle by adopting a positive attitude angle fusion coefficient to obtain the attitude angle of the vehicle at the current moment;

and determining that the first modulus value is located outside the first preset range or the second modulus value is located outside the second preset range, and adopting the second attitude angle as the attitude angle of the vehicle at the current moment.

7. A vehicle speed determination device, characterized by comprising:

the parameter acquisition module is used for acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed at the current moment;

the vehicle speed determining module is used for determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

the vehicle speed fusion module is used for fusing the estimated speed and the instrument display vehicle speed at the current moment by adopting a complementary filtering method to obtain the vehicle speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

8. An apparatus, characterized in that the apparatus comprises:

one or more processors;

a storage device for storing one or more programs,

when executed by the one or more processors, cause the one or more processors to implement the vehicle speed determination method as claimed in any one of claims 1-6.

9. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, is adapted to carry out a vehicle speed determination method according to any one of claims 1-6.

Technical Field

The embodiment of the invention relates to the technical field of automatic emergency braking, in particular to a method, a device, equipment and a medium for determining vehicle speed.

Background

Automatic Emergency Braking (AEB) is a technology for actively Braking when a vehicle encounters an Emergency or the distance between the vehicle and a preceding vehicle or a pedestrian is less than a safe distance in the normal driving process, so as to avoid or reduce collision accidents such as rear-end collision and the like, thereby improving the driving safety.

In the automatic emergency braking process, the control parameters of the active brake are determined based on the real-time vehicle speed of the vehicle, so the accuracy of the real-time vehicle speed directly influences the accuracy of the automatic emergency brake. In the prior art, the instrument in the vehicle is adopted to display the vehicle speed as the real-time vehicle speed, but the vehicle speed is changed very quickly in the automatic emergency braking process, and the display vehicle speed of the instrument in a plurality of vehicles is updated later, so that the updating of the display vehicle speed of the instrument is slow, and the accuracy of the automatic emergency braking is influenced.

Disclosure of Invention

The invention provides a method, a device, equipment and a medium for determining a vehicle speed, which are used for improving the accuracy of vehicle speed determination in an automatic emergency braking process.

In a first aspect, an embodiment of the present invention provides a vehicle speed determining method for determining a vehicle speed of a vehicle during automatic emergency braking in real time, including:

acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment, and the instrument display speed at the current moment;

determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

In a second aspect, an embodiment of the present invention further provides a vehicle speed determination device, including:

the parameter acquisition module is used for acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed at the current moment;

the vehicle speed determining module is used for determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

the vehicle speed fusion module is used for fusing the estimated speed and the instrument display vehicle speed at the current moment by a complementary filtering method to obtain the vehicle speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

In a third aspect, an embodiment of the present invention further provides an apparatus, where the apparatus includes:

one or more processors;

a storage device for storing one or more programs,

when the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the vehicle speed determination method as described in the first aspect above.

In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, which when executed by a processor implements the vehicle speed determination method according to the first aspect.

The technical scheme provided by the embodiment of the invention comprises the steps of obtaining the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed of the current moment, determining the estimated speed of the vehicle at the current moment, fusing the estimated speed and the instrument display speed of the current moment according to the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment, and obtaining the speed of the vehicle at the current moment, wherein the current moment is the other moments except the initial moment of automatic emergency braking, the braking acceleration is the acceleration without gravity component obtained based on the attitude angle of the vehicle, the current moment is the next moment of the initial moment of automatic emergency braking, the speed of the previous moment is the instrument display speed at the initial moment of automatic emergency braking, and the current moment is the other moments except the next moment of the initial moment of the automatic emergency, the speed at the last moment is the estimated speed of the vehicle at the last moment, the problem of inaccurate speed determination caused by slow updating speed of the speed displayed by the instrument in the automatic emergency braking process is solved, the accuracy of speed determination is improved, the accuracy of brake control executed based on the speed is improved, and the probability of traffic accidents is reduced.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

FIG. 1 is a schematic flow chart diagram of a vehicle speed determination method provided by an embodiment of the present invention;

FIG. 2 is a flow chart illustrating a method for fusing estimated speed and vehicle speed displayed by the meter according to an embodiment of the present invention;

FIG. 3 is a schematic flow chart of a method for obtaining braking acceleration of a vehicle according to an embodiment of the present invention;

FIG. 4 is a flowchart illustrating a method for obtaining an attitude angle of a vehicle in real time according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating a method for denoising by moving average filtering according to an embodiment of the present invention;

FIG. 6 is a flowchart illustrating a method for obtaining an attitude angle of a vehicle at a current time according to a first attitude angle and a second attitude angle according to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a vehicle speed determining apparatus according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of an apparatus according to an embodiment of the present invention.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given with reference to the accompanying drawings and preferred embodiments of a vehicle speed determining method and device, a vehicle speed determining apparatus, a vehicle speed determining medium, and specific embodiments, structures, features and effects thereof according to the present invention.

The embodiment of the invention provides a vehicle speed determining method, which is used for determining the vehicle speed of a vehicle in an automatic emergency braking process in real time and comprises the following steps:

acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment, and the instrument display speed at the current moment;

determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

The technical scheme provided by the embodiment of the invention comprises the steps of obtaining the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed of the current moment, determining the estimated speed of the vehicle at the current moment, fusing the estimated speed and the instrument display speed of the current moment according to the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment, and obtaining the speed of the vehicle at the current moment, wherein the current moment is the other moments except the initial moment of automatic emergency braking, the braking acceleration is the acceleration without gravity component obtained based on the attitude angle of the vehicle, the current moment is the next moment of the initial moment of automatic emergency braking, the speed of the previous moment is the instrument display speed at the initial moment of automatic emergency braking, and the current moment is the other moments except the next moment of the initial moment of the automatic emergency, the speed at the last moment is the estimated speed of the vehicle at the last moment, the problem of inaccurate speed determination caused by slow updating speed of the speed displayed by the instrument in the automatic emergency braking process is solved, the accuracy of speed determination is improved, the accuracy of brake control executed based on the speed is improved, and the probability of traffic accidents is reduced.

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 obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the protection scope of the present invention.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other embodiments that depart from the specific details disclosed herein, and it will be recognized by those skilled in the art that the present invention may be practiced without these specific details.

Next, the present invention is described in detail with reference to the schematic drawings, and in the detailed description of the embodiments of the present invention, the schematic drawings showing the structure of the device are not partially enlarged in general scale for convenience of description, and the schematic drawings are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and height should be included in the actual fabrication.

FIG. 1 is a flow chart illustrating a method for determining vehicle speed according to an embodiment of the present invention. The vehicle speed determination method is used for determining the vehicle speed of a vehicle in an automatic emergency braking process in real time, and can be executed by a vehicle speed determination device which can be realized in a hardware and/or software mode and can be generally integrated in the vehicle.

As shown in fig. 1, the vehicle speed determination method provided by the embodiment of the invention specifically includes the following steps:

step 11, obtaining the speed of the last moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the last moment, and the instrument display speed of the current moment, wherein the current moment is other moments except the initial moment of automatic emergency braking, the braking acceleration is the acceleration without gravity component obtained based on the attitude angle of the vehicle, the speed of the last moment is the instrument display speed of the initial moment of automatic emergency braking when the current moment is the next moment of the initial moment of automatic emergency braking, and the speed of the last moment is the estimated speed of the vehicle at the last moment when the current moment is other moments except the next moment of the initial moment of automatic emergency braking.

The vehicle speed of the vehicle at the initial time of the automatic emergency braking may be the vehicle speed indicated by the meter at that time.

It should be further noted that, in the process of constant speed running before automatic emergency braking, the meter displays that the speed of the vehicle is substantially equal to the actual speed of the vehicle, the accuracy is high, the initial time of automatic emergency braking is the ending time of constant speed running, and the meter displays that the speed of the vehicle is still accurate at this moment, so that when the current moment is the next moment of the initial time of automatic emergency braking, the speed of the vehicle is taken as the speed at the previous moment, and on the basis of ensuring the accuracy of the speed, the acquisition mode of the speed at the initial time of automatic emergency braking is simple.

The automatic emergency braking is usually triggered after a preset condition is met, and the first moment when the preset condition is met is the initial moment of the automatic emergency braking. For example, when the preset condition is that the vehicle-to-front distance between the vehicle and the front vehicle is smaller than the preset value, the first moment when the vehicle-to-front distance between the vehicle and the front vehicle is smaller than the preset value is the initial moment of automatic emergency braking.

In order to play a role in prompting, the vehicle can give an alarm when the automatic emergency braking is triggered, and the initial moment of the automatic emergency braking can also be understood as the moment when the alarm starts.

It should be noted that the braking acceleration is the real-time acceleration of the vehicle in the automatic emergency braking process, and it can be understood that, when the vehicle is braked rapidly in the automatic emergency braking process, the pitch angle of the vehicle is inevitably not zero, so that a gravity component exists in the acceleration measured by the accelerometer, and the gravity component is irrelevant to the vehicle speed. In particular, the method comprises the following steps of,， is the real-time motion acceleration of the vehicle in the advancing direction of the vehicle speed,the acceleration is directly collected by the accelerometer or collected by the accelerometer and subjected to denoising treatment,which is a pitch angle among attitude angles of the vehicle,acceleration of gravity, visible, braking accelerationIs obtained based on the attitude angle calculation of the vehicle.

It should be noted that the instrument display vehicle speed is vehicle speed information displayed by an instrument for displaying vehicle speed in the vehicle.

And step 12, determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment.

According to the velocity calculation formula:wherein, in the step (A),for the estimated speed of the vehicle at the present moment,in order to obtain the speed of the last moment,is the braking acceleration of the vehicle at the present moment,and calculating the estimated speed of the vehicle at the current moment according to the time difference between the current moment and the previous moment.

And step 13, fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment.

Because certain errors exist in the attitude angle calculation process, the obtained braking acceleration has smaller deviation, so that the directly calculated estimated vehicle speed is smaller than the real vehicle speed, in the automatic emergency braking process, the smaller the vehicle speed is, the correspondingly generated braking force is smaller, and the required braking distance is larger, so that the actually output braking force is smaller than the required braking force by directly taking the estimated speed as the vehicle speed, the following distance is further shortened, and even the avoidable collision is not effectively avoided.

The updating of the vehicle speed displayed by the instrument is slow, so that the vehicle speed displayed by the instrument is greater than the real vehicle speed, the estimated vehicle speed and the vehicle speed displayed by the instrument are fused, and the vehicle speed is determined in a complementary manner, so that the determined vehicle speed is closer to the real vehicle speed.

It should be noted that, in the embodiment, the estimation speed and the instrument display speed are fused by using a complementary filtering method, so that the calculation process is simplified, the operation speed is increased, and the result accuracy is improved.

The technical scheme provided by the embodiment of the invention comprises the steps of obtaining the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed of the current moment, determining the estimated speed of the vehicle at the current moment, fusing the estimated speed and the instrument display speed of the current moment according to the speed of the vehicle at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment, and obtaining the speed of the vehicle at the current moment, wherein the current moment is the other moments except the initial moment of automatic emergency braking, the braking acceleration is the acceleration without gravity component obtained based on the attitude angle of the vehicle, the current moment is the next moment of the initial moment of automatic emergency braking, the speed of the previous moment is the instrument display speed at the initial moment of automatic emergency braking, and the current moment is the other moments except the next moment of the initial moment of the automatic emergency, the speed at the last moment is the estimated speed of the vehicle at the last moment, the problem of inaccurate speed determination caused by slow updating speed of the speed displayed by the instrument in the automatic emergency braking process is solved, the accuracy of speed determination is improved, the accuracy of brake control executed based on the speed is improved, and the probability of traffic accidents is reduced.

On the basis of the embodiment, the step of fusing the estimated speed and the vehicle speed displayed by the instrument by adopting a complementary filtering method is further optimized. Specifically, fig. 2 is a schematic flow chart of a method for fusing an estimated speed and a vehicle speed displayed by an instrument by using a complementary filtering method according to an embodiment of the present invention. As shown in fig. 2, fusing the estimated speed and the meter-displayed vehicle speed by using the complementary filtering method may include the following:

and step 21, obtaining prestored radar speed measurement data.

The radar speed measurement data is the real-time speed of the vehicle in the automatic emergency braking process obtained by adopting radar test. Experimental data proves that the radar speed measurement data in the early stage and the middle stage of automatic emergency braking are basically the same as the real speed of the vehicle, but in the later stage of automatic emergency braking, the radar speed measurement data can generate a section of obvious abnormal data, so that the radar speed measurement data are not suitable to be directly applied, and the speed fusion coefficient is determined by taking the radar speed measurement data in the early stage and the middle stage as the fusion standard so as to accurately determine the speed in the whole process of automatic emergency braking.

Specifically, the radar speed measurement data in the automatic emergency braking process can be obtained in advance through an experimental mode test and prestored.

And step 22, determining a vehicle speed fusion coefficient according to the radar speed measurement data, the estimated speed and the instrument display vehicle speed.

Specifically, the vehicle speed fusion formula containing the vehicle speed fusion coefficient is as follows:wherein, in the step (A),in order to fuse the obtained vehicle speeds,the speed of the vehicle is displayed for the meter,for the vehicle speed to be calculated based on the acceleration,is a vehicle speed fusion coefficient.

After the estimated speed at the current moment and the vehicle speed displayed by the instrument are obtained, the estimated speed and the vehicle speed are substituted into the vehicle speed fusion formula, and the vehicle speed fusion coefficient is adjusted, so that the vehicle speed obtained by fusion is consistent with the radar speed measurement data at the current moment. In addition, in order to avoid the inaccuracy of the vehicle speed fusion coefficient determined by single data, the vehicle speed fusion coefficients at multiple moments can be determined in the above manner, and the vehicle speed fusion coefficient with the largest proportion or the average value of the multiple vehicle speed fusion coefficients distributed in a centralized manner is used as the determined vehicle speed fusion coefficient.

And step 23, adopting a vehicle speed fusion coefficient to fuse and estimate the vehicle speed and displaying the vehicle speed by an instrument.

Based on the vehicle speed fusion formula, after the vehicle speed fusion coefficient is determined, the estimated speed and the instrument display vehicle speed at each moment can be substituted into the vehicle speed fusion formula to obtain the corresponding vehicle speed.

Optionally, when the current time is a next time of the initial time of the automatic emergency braking, the vehicle speed of the vehicle at the previous time is the vehicle speed displayed by the instrument at the initial time of the automatic emergency braking.

It should be noted that, on the basis of the above embodiments, the step of obtaining the braking acceleration of the vehicle at the current time is further optimized. Specifically, fig. 3 is a schematic flowchart of a method for obtaining a braking acceleration of a vehicle at a current time according to an embodiment of the present invention. As shown in fig. 3, acquiring the braking acceleration of the vehicle at the present time may include the following:

and step 41, acquiring the linear acceleration of the vehicle at the current moment.

Specific ways of acquiring the linear acceleration include, for example: acquiring the acceleration obtained by the accelerometer test, or acquiring the acceleration obtained by the accelerometer test after denoising, wherein the denoising method is, for example, a kalman filtering method.

And step 42, acquiring the attitude angle of the vehicle at the current moment.

The attitude angle of the vehicle is a triaxial attitude angle, including a pitch angle, a roll angle and a course angle, and in this embodiment, the pitch angle and the roll angle which are important in the automatic emergency braking process are focused. The specific acquisition mode will be described later.

And 43, obtaining the braking acceleration without the gravity component according to the attitude angle and the linear acceleration.

It is to be noted thatBy usingThe specific manner of obtaining the braking acceleration is described in the foregoing, and is not described herein again.

On the basis of the above embodiment, the step of obtaining the attitude angle of the vehicle at the current time is further optimized. Specifically, fig. 4 is a schematic flowchart of a method for obtaining an attitude angle of a vehicle at a current time according to an embodiment of the present invention. As shown in fig. 4, acquiring the attitude angle of the vehicle at the present time may include the following:

and 51, acquiring the angular velocity acquired by the gyroscope and the linear acceleration acquired by the accelerometer at the current moment.

The angular velocity comprises three-axis angular velocity, and the linear acceleration comprises three-axis acceleration.

And step 52, acquiring an attitude angle variable according to the angular speed.

Integrating the three-axis angular velocity to obtain three-axis attitude angle, specifically, pitch anglePitchAnd roll angleRollFor example, for pitch anglePitchAt time of∆tThe corresponding attitude angle variable is obtained by the inner integral:for roll angleRollAt time of∆tThe corresponding attitude angle variable is obtained by the inner integral:wherein, GyrY is a pitch angle angular velocity, and GyrX is a roll angular velocity. Notably, time∆tThe method is extremely short, so the content calculates the discretization of the integral form.

And 53, obtaining a first attitude angle of the vehicle according to the attitude angle variable and the attitude angle of the vehicle at the previous moment.

In particular, the method comprises the following steps of,wherein P1 is the first attitude angle, P1 is the attitude angle determined at the last moment,as attitude angle variable, still in pitch anglePitchAnd roll angleRollFor example, a first attitude angle of a pitch angleFirst attitude angle to roll angle。

And the attitude angle of the vehicle at the last moment is a final attitude angle obtained according to the first attitude angle and the second attitude angle at the last moment.

And step 54, obtaining a second attitude angle of the vehicle according to the linear acceleration.

And determining the triaxial second attitude angle of the vehicle according to the arc tangent data of the ratio of the two accelerations related to the corresponding second attitude angle in the triaxial accelerations. Illustratively, for the case where the second attitude angle determined from the acceleration is a pitch angle and a roll angle, the acceleration includes a three-axis acceleration:ax、ay andazwherein, in the step (A),aythe same direction as the advancing direction of the vehicle, the planes of ax and ay are parallel to the plane of the chassis of the vehicle, and the pitch angleAngle of transverse rolling。

And step 55, acquiring the attitude angle of the vehicle at the current moment according to the first attitude angle and the second attitude angle by adopting a preset rule.

The preset rule is a method for determining the vehicle attitude angle by using the first attitude angle and the second attitude angle, which is preset, and this embodiment is not specifically limited to this, and may be set according to actual needs, and an optional implementation mode is provided for an exemplary description in the following. Optionally, after acquiring the angular velocity acquired by the gyroscope and the acceleration acquired by the linear accelerometer at the current time, the method may further include: and denoising the angular velocity acquired by the gyroscope by adopting a moving average filtering method, and denoising the linear acceleration acquired by the accelerometer by adopting a Kalman filtering method.

It should be noted that, because the linear acceleration noise collected by the accelerometer is large and is difficult to be directly applied to control, it is necessary to perform denoising processing on the linear acceleration data, and the linear acceleration noise is mainly high-frequency noise generated by the vibration of the engine of the vehicle itself.

Specifically, the kalman filtering method includes the following 5 basic formulas:

X(k|k-1)=AX(k-1|k-1)+BU(k)………(1)

P(k|k-1)=AP(k-1|k-1)A’+Q………(2)

X(k|k)=X(k|k-1)+Kg(k)(Z(k)-HX(k|k-1))………(3)

Kg(k)=P(k|k-1)H’/(HP(k|k-1)H’+R)………(4)

P(k|k)=(1-Kg(k)H)P(k|k-1)………(5)

wherein X (k | k-1) is a predicted value at the time k, X (k-1| k-1) is an estimated value at the time k-1, P (k | k-1) is a predicted covariance at the time k, P (k-1| k-1) is an estimated covariance at the time k-1, X (k | k) is an estimated value at the time k (data after denoising), Z (k) is a measured value, Kg (k) is a Kalman gain, Q is a prediction process noise covariance, H is a measurement transformation matrix, R is a covariance of measurement noise, U (k) is a state control quantity at the time k, A is a state transition matrix, B is a control matrix

Firstly, setting a predicted value at the time k to be equal to an estimated value at the time k-1 for linear acceleration data, and taking U (K) =0 because the linear acceleration original data does not have a state control quantity; take a = 1. The above equation (1) is thus transformed into:

X(k|k-1)= X(k-1|k-1)

after obtaining the predicted value X (k | k-1) at time k, the prediction covariance at time k needs to be calculated from the estimated covariance at time k-1. First, Q is defined, where noise refers to the covariance of the system process, and when a =1, a' =1, so the above equation (2) is transformed into:

P(k|k-1)= P(k-1|k-1)+Q

next, the kalman gain kg (k) is calculated, where H =1, and therefore H' =1, and therefore the above equation (4) is transformed into:

Kg(k)= P(k|k-1)/( P(k|k-1)+R)

after kalman gain kg (k) is obtained, the prediction value X (k | k-1) at time k is corrected by using the kalman gain kg (k) and the deviation between the measurement value and the prediction value to obtain an estimation value X (k | k) at time k, and when H =1, formula (3) is transformed into:

X(k|k)= X(k|k-1)+Kg(k)*(Z(k)- X(k|k-1))

in order to facilitate prediction and estimation at the next time, the estimated covariance needs to be updated, that is, the estimated covariance at time k is obtained, specifically, when H =1, equation (5) is transformed into:

P(k|k)=(1-Kg(k))P(k|k-1)

on the other hand, since the angular velocity data acquired by the gyroscope mainly includes zero point deviation and random drift, the embodiment uses a sliding average filtering method to smooth and denoise the angular velocity data, and the specific method is as shown in fig. 5, which can be simply understood as using a sliding window with a suitable window length and step length to perform sliding processing on the angular velocity data, and calculate the average value of all data in the sliding window as the angular velocity after filtering.

The embodiment removes noise by adopting different noise removing modes respectively aiming at different noise characteristics of linear acceleration and angular velocity so as to improve the noise removing effect and obtain more credible data.

On the basis of the above embodiment, the step of obtaining the attitude angle of the vehicle at the current time according to the first attitude angle and the second attitude angle by using the preset rule is further optimized. Fig. 6 is a flowchart illustrating a method for obtaining an attitude angle of a vehicle at a current time according to a first attitude angle and a second attitude angle according to an embodiment of the present invention. As shown in fig. 6, obtaining the attitude angle of the vehicle at the current time from the first attitude angle and the second attitude angle using a preset rule may include the following:

and 61, acquiring a first modulus value of the triaxial acceleration according to the linear acceleration acquired by the accelerometer at the current moment.

The first module value of the triaxial acceleration is the resultant acceleration value of the triaxial acceleration.

And step 62, acquiring a second modulus value of the acceleration coaxial with the current attitude angle.

Illustratively, for a pitch angle, which is an angle between a forward direction of the vehicle and the ground, the triaxial acceleration includes ax, ay, and az, the direction of ay is consistent with the forward direction of the vehicle, ay is an acceleration coaxial with the pitch angle, and the absolute value of ay is a second mode value corresponding to the pitch angle.

And step 63, determining that the first modulus is in a first preset range and the second modulus is in a second preset range, and fusing the first attitude angle and the second attitude angle by adopting a positive attitude angle fusion coefficient.

It should be noted that the positive attitude angle fusion coefficient indicates that the attitude angle obtained by fusion includes a first attitude angle component and a second attitude angle component.

When the first modulus is in the first preset range and the second modulus is in the second preset range, the vehicle can be fused with the first attitude angle and the second attitude angle to obtain the attitude angle of the vehicle under the conditions of non-bumpy road sections, non-rapid acceleration and deceleration and the like, and the accuracy is high. It should be noted that the method for obtaining the attitude angle by using the angular velocity is high in short-term accuracy, and has an integral drift accumulated error, if no correction compensation is added, severe drift occurs after long-term work, the method for obtaining the attitude angle by using the acceleration performs well under a static condition, but the attitude angle calculation can generate severe deviation under dynamic conditions, particularly under bump and brake conditions, and it can be seen that the accuracy of the attitude angle obtained by using a single calculation method is not high. In order to solve the problems, the first attitude angle and the second attitude angle are fused by adopting a complementary filtering method, the principle is simple, the operation speed is high, the parameter adjustment is simple, based on the complementary characteristics of the accelerometer and the gyroscope in the frequency domain, noise can be filtered and drift can be inhibited, the method is more suitable for solving the actual vehicle attitude, and the precision of the fused attitude angle is higher.

And step 64, determining that the first modulus is located outside the first preset range or the second modulus is located outside the second preset range, and adopting the second attitude angle as the attitude angle of the vehicle.

When the first modulus value is located outside the first preset range or the second modulus value is located outside the second preset range, it is indicated that the vehicle is in rapid acceleration, rapid braking or driving on a bumpy road section, and the like, at this time, the measured value of the accelerometer is obviously affected, and the attitude angle directly calculated from the measured value is greatly deviated, so that the attitude angle obtained by adopting the mode fusion in the step 63 is inaccurate, and the vehicle speed determined based on the attitude angle is inaccurate and cannot be used for subsequent vehicle speed optimization and auxiliary braking control. At this time, the present embodiment only trusts the attitude angle obtained by the angular velocity calculation, and it can also be understood that the coefficient of the attitude angle determined by the angular velocity in step 63 is set to be 1, and the coefficient of the attitude angle determined by the acceleration is set to be 0, so that the attitude angle fusion formula corresponding to the pitch angle in step 63 may be:

the attitude angle fusion formula corresponding to the roll angle in step 63 may be:

wherein the content of the first and second substances,is the pitch angle at the present moment,the pitch angle determined for the last moment in time,for the pitch angle change amount obtained based on the angular velocity calculation,for the pitch angle obtained based on the acceleration calculation,in order to obtain the attitude angle fusion coefficient,suitable attitude angle fusion coefficients are determined based on experimental data. The technical solution of the present invention is exemplified below with a complete example:

acquiring the three-axis angular velocity acquired by the gyroscope and the three-axis acceleration acquired by the accelerometer, denoising the angular velocities of the axes by respectively adopting a sliding average filtering method, and denoising the acceleration of the axes by respectively adopting a Kalman filtering method, wherein the specific denoising process refers to the related description.

Obtaining corresponding attitude angles for all axes respectively by adopting the following modes: and calculating an attitude angle variable by using the angular velocity after the noise removal, obtaining a first attitude angle of the current moment by using the attitude angle variable and the attitude angle determined at the last moment, and calculating a second attitude angle by using the acceleration after the noise removal, wherein the specific calculation method refers to the related description. Acquiring a first module value of triaxial acceleration and a second module value of acceleration coaxial with the current attitude angle, determining that the first module value is located in a first preset range, determining that the second module value is located in a second preset range, fusing the first attitude angle and the second attitude angle by adopting a positive attitude angle fusion coefficient, determining that the first module value is located outside the first preset range or the second module value is located outside the second preset range, and adopting the second attitude angle as the attitude angle of the vehicle.

Fig. 7 is a schematic structural diagram of a vehicle speed determination device provided by an embodiment of the invention. As shown in fig. 7, the vehicle speed determination device includes:

the parameter acquisition module 81 is used for acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment and the instrument display speed at the current moment;

the vehicle speed determining module 82 is used for determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

the vehicle speed fusion module 83 is used for fusing the estimated speed and the instrument display vehicle speed at the current moment by adopting a complementary filtering method to obtain the vehicle speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is the acceleration without the gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of the automatic emergency braking, the previous moment speed is the instrument display speed of the initial moment of the automatic emergency braking; and when the current moment is other than the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

In the present embodiment, the vehicle speed fusion module 83 may include:

the data acquisition unit is used for acquiring prestored radar speed measurement data;

the coefficient determining unit is used for determining a vehicle speed fusion coefficient according to the radar speed measurement data, the estimated speed and the vehicle speed displayed by the instrument;

and the speed fusion unit is used for fusing and estimating the speed and displaying the vehicle speed by the instrument by adopting a vehicle speed fusion coefficient.

In this embodiment, the parameter obtaining module 81 may include:

an acceleration obtaining unit for obtaining a linear acceleration of the vehicle at a current time;

an attitude angle obtaining unit for obtaining an attitude angle of the vehicle at the present time;

and the acceleration calculation unit is used for obtaining the braking acceleration without the gravity component according to the attitude angle and the linear acceleration.

In the present embodiment, the attitude angle obtaining unit may include:

the parameter acquisition subunit is used for acquiring the angular velocity acquired by the gyroscope and the acceleration acquired by the linear accelerometer at the current moment;

the variable obtaining subunit is used for obtaining an attitude angle variable according to the angular speed;

the angle determining subunit is used for obtaining a first attitude angle of the vehicle according to the attitude angle variable and the attitude angle of the vehicle at the previous moment;

an angle obtaining subunit configured to obtain a second attitude angle of the vehicle according to the linear acceleration;

and the attitude angle determining subunit is used for obtaining the attitude angle of the vehicle at the current moment according to the first attitude angle and the second attitude angle by adopting a preset rule.

In the present embodiment, the attitude angle obtaining unit may further include

The first processing subunit is used for performing denoising processing on the angular velocity acquired by the gyroscope by adopting a moving average filtering method after acquiring the angular velocity acquired by the gyroscope and the acceleration acquired by the linear accelerometer at the current moment;

and the second processing subunit is used for performing denoising processing on the linear acceleration acquired by the accelerometer by adopting a Kalman filtering method after acquiring the angular velocity acquired by the gyroscope and the acceleration acquired by the linear accelerometer at the current moment.

In this embodiment, the attitude angle determination subunit may be specifically configured to:

acquiring a first modulus value of triaxial acceleration according to linear acceleration acquired by an accelerometer at the current moment;

acquiring a second modulus value of the acceleration which is coaxial with the current attitude angle;

determining that the first modulus value is in a first preset range and the second modulus value is in a second preset range, and fusing the first attitude angle and the second attitude angle by adopting a positive attitude angle fusion coefficient to obtain the attitude angle of the vehicle at the current moment;

and determining that the first modulus value is positioned outside a first preset range or the second modulus value is positioned outside a second preset range, and adopting the second attitude angle as the attitude angle of the vehicle at the current moment.

Fig. 8 is a schematic structural diagram of an apparatus according to an embodiment of the present invention, as shown in fig. 8, the apparatus includes a processor 70, a memory 71, an input device 72, and an output device 73; the number of processors 70 in the device may be one or more, and one processor 70 is taken as an example in fig. 8; the processor 70, the memory 71, the input device 72 and the output device 73 of the apparatus may be connected by a bus or other means, as exemplified by the bus connection in fig. 8.

The memory 71, as a computer-readable storage medium, may be used to store software programs, computer-executable programs, and modules, such as program instructions/modules corresponding to the vehicle speed determination method in the embodiment of the present invention (e.g., the parameter acquisition module 81, the vehicle speed determination module 82, and the vehicle speed fusion module 83 included in the vehicle speed determination device). The processor 70 executes various functional applications of the device and data processing, i.e., implements the vehicle speed determination method described above, by executing software programs, instructions, and modules stored in the memory 71.

The memory 71 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 for at least one function; the storage data area may store data created according to the use of the terminal, and the like. Further, the memory 71 may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory 71 may further include memory located remotely from the processor 70, which may be connected to the device over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The input device 72 may be used to receive entered numeric or character information and to generate key signal inputs relating to user settings and function controls of the apparatus. The output device 73 may include a display device such as a display screen.

Embodiments of the present invention also provide a storage medium containing computer-executable instructions which, when executed by a computer processor, perform a method for vehicle speed determination, the method comprising:

acquiring the speed at the previous moment, the braking acceleration of the vehicle at the current moment, the time difference between the current moment and the previous moment, and the instrument display speed at the current moment;

determining the estimated speed of the vehicle at the current moment according to the speed at the previous moment, the braking acceleration of the vehicle at the current moment and the time difference between the current moment and the previous moment;

fusing the estimated speed and the instrument display speed at the current moment by adopting a complementary filtering method to obtain the speed of the vehicle at the current moment;

the current moment is other moments except the initial moment of automatic emergency braking, and the braking acceleration is acceleration without a gravity component obtained based on the attitude angle of the vehicle;

when the current moment is the next moment of the initial moment of automatic emergency braking, the speed at the last moment is the instrument display speed of the initial moment of automatic emergency braking; and when the current moment is other moments except the next moment of the initial moment of the automatic emergency braking, the speed at the last moment is the estimated speed of the vehicle at the last moment.

Of course, the storage medium containing the computer-executable instructions provided by the embodiments of the present invention is not limited to the method operations described above, and may also perform related operations in the vehicle speed determination method provided by any embodiments of the present invention.

From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.

It should be noted that, in the embodiment of the vehicle speed determination device, the included units and modules are merely divided according to the functional logic, but are not limited to the above division as long as the corresponding functions can be realized; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.