阅读说明：本技术 一种车辆速度测量系统及方法 (Vehicle speed measuring system and method ) 是由 陈凡 张晓宇 方镕城 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种车辆速度测量系统及方法。该系统包括：信号处理单元以及至少两个传声器；传声器设置于道路旁或道路之上,且传声器的声波采集端口朝向道路,传声器之间具有设定距离；信号处理单元根据设定距离以及来自至少两个传声器的声波信号的时间信息和幅值信息确定声波信号对应的车辆的速度。上述方法包括：1)获取来自至少两个传声器的声波信号；至少两个传声器设置于道路旁或道路之上,且传声器的声波采集端口朝向道路,传声器之间具有设定距离；2)根据设定距离以及来自至少两个传声器的声波信号的时间信息和幅值信息确定声波信号对应的车辆的速度。本发明基于车辆行驶时产生的声波信号实现了其速度的测量。(The invention discloses a vehicle speed measuring system and a vehicle speed measuring method. The system comprises: a signal processing unit and at least two microphones; the microphones are arranged beside a road or on the road, sound wave acquisition ports of the microphones face the road, and a set distance is reserved between the microphones; the signal processing unit determines the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signal from the at least two microphones. The method comprises the following steps: 1) acquiring sound wave signals from at least two microphones; the at least two microphones are arranged beside a road or on the road, sound wave acquisition ports of the microphones face the road, and a set distance is reserved between the microphones; 2) and determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones. The invention realizes the speed measurement based on the sound wave signal generated when the vehicle runs.)

1. A vehicle speed measurement system, comprising: a signal processing unit and at least two microphones; the microphones are arranged beside a road or on the road, sound wave collecting ports of the microphones face the road, and a set distance is reserved between the microphones; and the signal processing unit determines the speed of the vehicle corresponding to the sound wave signals according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones.

2. The vehicle speed measurement system of claim 1, wherein the at least two microphones include a first microphone and a second microphone, a line connecting the first microphone and the second microphone being parallel to the road;

the signal processing unit comprises a first signal processing module, and the first signal processing module is used for calculating the time difference between the valley point of the first pulse sound wave signal and the valley point of the second pulse sound wave signal and calculating the speed of the vehicle according to the set distance and the time difference; the first pulse sound wave signal is a sound wave signal which is acquired by the first microphone and corresponds to the vehicle, and the second pulse sound wave signal is a sound wave signal which is acquired by the second microphone and corresponds to the vehicle.

3. The vehicle speed measurement system of claim 1, wherein the at least two microphones include a third microphone and a fourth microphone, a line connecting the third microphone and the fourth microphone being perpendicular to the road;

the signal processing unit comprises a second signal processing module, and the second signal processing module is used for:

determining a first distance between the vehicle and a third microphone or a second distance between the vehicle and a fourth microphone according to a valley point of a third pulse sound wave signal, a valley point of a fourth pulse sound wave signal and the set distance; the third pulse sound wave signal is a sound wave signal which is acquired by the third microphone and corresponds to the vehicle, and the fourth pulse sound wave signal is a sound wave signal which is acquired by the fourth microphone and corresponds to the vehicle;

calculating the speed of the vehicle according to the first distance and the first time difference or according to the second distance and the second time difference; the first time difference is a time difference between a valley point of the third pulse acoustic wave signal and a first target point of the third pulse acoustic wave signal, and the first target point is a target point of the third pulse acoustic wave signal, wherein the amplitude value of the target point is equal to the valley valueA point earlier in time than the valley point; the second time difference is a time difference between the fourth pulsed acoustic signal evaluation point and a second target point of the fourth pulsed acoustic signal, the second target point being a point on the fourth pulsed acoustic signal where the amplitude is equal to the troughAnd a point earlier in time than the valley point.

4. The vehicle speed measurement system of claim 1, wherein the at least two microphones comprise a trigger microphone, and when the amplitude of the sound wave signal collected by the trigger microphone reaches a predetermined value, the sound wave signals collected by all the microphones are recorded, and the recorded sound wave signals are transmitted to the signal processing unit.

5. The vehicle speed measurement system of claim,

the sound wave signal processed by the signal processing unit is a low-pass filtered sound wave signal;

the system further comprises: and the low-pass filtering unit is used for performing low-pass filtering on the sound wave signal.

6. A vehicle speed measurement method, characterized by comprising:

acquiring sound wave signals from at least two microphones; the at least two microphones are arranged beside a road or on the road, sound wave collecting ports of the microphones face the road, and a set distance is reserved between the microphones;

and determining the speed of the vehicle corresponding to the sound wave signals according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones.

7. The vehicle speed measuring method according to claim 6, wherein the determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones specifically comprises:

calculating a time difference between a valley point of the first pulse sound wave signal and a valley point of the second pulse sound wave signal; the at least two microphones comprise a first microphone and a second microphone, the connecting line of the first microphone and the second microphone is parallel to the road, the first pulse sound wave signal is a sound wave signal which is acquired by the first microphone and corresponds to the vehicle, and the second pulse sound wave signal is a sound wave signal which is acquired by the second microphone and corresponds to the vehicle;

and calculating the speed of the vehicle according to the set distance and the time difference.

8. The vehicle speed measuring method according to claim 6, wherein the determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones specifically comprises:

determining a first distance between the vehicle and a third microphone or a second distance between the vehicle and a fourth microphone according to a valley point of a third pulse sound wave signal, a valley point of a fourth pulse sound wave signal and the set distance; wherein the at least two microphones comprise a third microphone and a fourth microphone, and a connecting line of the third microphone and the fourth microphone is perpendicular to the road; the third pulse sound wave signal is a sound wave signal which is acquired by the third microphone and corresponds to the vehicle, and the fourth pulse sound wave signal is a sound wave signal which is acquired by the fourth microphone and corresponds to the vehicle;

calculating the speed of the vehicle according to the first distance and the first time difference or according to the second distance and the second time difference; the first time difference is a time difference between a valley point of the third pulse acoustic wave signal and a first target point of the third pulse acoustic wave signal, and the first target point is a target point of the third pulse acoustic wave signal, wherein the amplitude value of the target point is equal to the valley valueA point earlier in time than the valley point; the second time difference is a time difference between the fourth pulsed acoustic signal evaluation point and a second target point of the fourth pulsed acoustic signal, the second target point being a point on the fourth pulsed acoustic signal where the amplitude is equal to the troughAnd a point earlier in time than the valley point.

9. The vehicle speed measuring method according to claim 6, further comprising, before the determining the speed of the vehicle corresponding to the acoustic wave signal based on the set distance and the time information and the amplitude information of the acoustic wave signals from the at least two microphones, the step of:

and carrying out low-pass filtering on the sound wave signals collected by the at least two microphones.

10. The vehicle speed measurement method according to claim 6, wherein the at least two microphones include a trigger microphone, and prior to said acquiring the acoustic wave signals from the at least two microphones, further comprising:

and when the amplitude of the sound wave signals collected by the trigger microphone reaches a preset value, starting to record the sound wave signals collected by all the microphones.

Technical Field

The invention relates to the field of vehicle speed measurement, in particular to a vehicle speed measurement system and method.

Background

With the popularization of automobiles, the overspeed of the automobile often occurs, so people often need various technical means to measure the speed of the automobile.

Disclosure of Invention

The invention aims to provide a vehicle speed measuring system and a vehicle speed measuring method.

In order to achieve the purpose, the invention provides the following scheme:

a vehicle speed measurement system comprising: a signal processing unit and at least two microphones; the microphones are arranged beside a road or on the road, sound wave collecting ports of the microphones face the road, and a set distance is reserved between the microphones; and the signal processing unit determines the speed of the vehicle corresponding to the sound wave signals according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones.

Optionally, the at least two microphones include a first microphone and a second microphone, and a connection line of the first microphone and the second microphone is parallel to the road;

the signal processing unit comprises a first signal processing module, and the first signal processing module is used for calculating the time difference between the valley point of the first pulse sound wave signal and the valley point of the second pulse sound wave signal and calculating the speed of the vehicle according to the set distance and the time difference; the first pulse sound wave signal is a sound wave signal which is acquired by the first microphone and corresponds to the vehicle, and the second pulse sound wave signal is a sound wave signal which is acquired by the second microphone and corresponds to the vehicle.

Optionally, the at least two microphones include a third microphone and a fourth microphone, and a connection line of the third microphone and the fourth microphone is perpendicular to the road;

the signal processing unit comprises a second signal processing module, and the second signal processing module is used for:

determining a first distance between the vehicle and a third microphone or a second distance between the vehicle and a fourth microphone according to a valley point of a third pulse sound wave signal, a valley point of a fourth pulse sound wave signal and the set distance; the third pulse sound wave signal is a sound wave signal which is acquired by the third microphone and corresponds to the vehicle, and the fourth pulse sound wave signal is a sound wave signal which is acquired by the fourth microphone and corresponds to the vehicle;

calculating the speed of the vehicle according to the first distance and the first time difference or according to the second distance and the second time difference; the first time difference is a time difference between a valley point of the third pulse acoustic wave signal and a first target point of the third pulse acoustic wave signal, and the first target point is a target point of the third pulse acoustic wave signal, wherein the amplitude value of the target point is equal to the valley valueA point earlier in time than the valley point; the second time difference is a time difference between the fourth pulsed acoustic signal evaluation point and a second target point of the fourth pulsed acoustic signal, the second target point being a point on the fourth pulsed acoustic signal where the amplitude is equal to the troughAnd a point earlier in time than the valley point.

Optionally, the at least two microphones include a trigger microphone, when the amplitude of the sound wave signal collected by the trigger microphone reaches a preset value, the sound wave signals collected by all the microphones are recorded, and the recorded sound wave signals are used for being transmitted to the signal processing unit.

Optionally, the sound wave signal processed by the signal processing unit is a low-pass filtered sound wave signal;

the system further comprises: and the low-pass filtering unit is used for performing low-pass filtering on the sound wave signal.

The invention also provides a vehicle speed measuring method, which comprises the following steps:

acquiring sound wave signals from at least two microphones; the at least two microphones are arranged beside a road or on the road, sound wave collecting ports of the microphones face the road, and a set distance is reserved between the microphones;

and determining the speed of the vehicle corresponding to the sound wave signals according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones.

Optionally, the determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones specifically includes:

calculating a time difference between a valley point of the first pulse sound wave signal and a valley point of the second pulse sound wave signal; the at least two microphones comprise a first microphone and a second microphone, the connecting line of the first microphone and the second microphone is parallel to the road, the first pulse sound wave signal is a sound wave signal which is acquired by the first microphone and corresponds to the vehicle, and the second pulse sound wave signal is a sound wave signal which is acquired by the second microphone and corresponds to the vehicle;

and calculating the speed of the vehicle according to the set distance and the time difference.

Optionally, the determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones specifically includes:

determining a first distance between the vehicle and a third microphone or a second distance between the vehicle and a fourth microphone according to a valley point of a third pulse sound wave signal, a valley point of a fourth pulse sound wave signal and the set distance; wherein the at least two microphones comprise a third microphone and a fourth microphone, and a connecting line of the third microphone and the fourth microphone is perpendicular to the road; the third pulse sound wave signal is a sound wave signal which is acquired by the third microphone and corresponds to the vehicle, and the fourth pulse sound wave signal is a sound wave signal which is acquired by the fourth microphone and corresponds to the vehicle;

calculating the speed of the vehicle according to the first distance and the first time difference or according to the second distance and the second time difference; the first time difference is a time difference between a valley point of the third pulse acoustic wave signal and a first target point of the third pulse acoustic wave signal, and the first target point is a target point of the third pulse acoustic wave signal, wherein the amplitude value of the target point is equal to the valley valueA point earlier in time than the valley point; the second time difference is a time difference between the fourth pulsed acoustic signal evaluation point and a second target point of the fourth pulsed acoustic signal, the second target point being a point on the fourth pulsed acoustic signal where the amplitude is equal to the troughAnd a point earlier in time than the valley point.

Optionally, before determining the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones, the method further includes:

and carrying out low-pass filtering on the sound wave signals collected by the at least two microphones.

Optionally, the at least two microphones include a trigger microphone, and before the acquiring the acoustic wave signals from the at least two microphones, the method further includes:

and when the amplitude of the sound wave signals collected by the trigger microphone reaches a preset value, starting to record the sound wave signals collected by all the microphones.

According to the specific embodiment provided by the invention, the following technical effects are disclosed: the application provides a vehicle speed measurement system includes: the system comprises a signal processing unit and at least two microphones, wherein the microphones are arranged beside a road, and a set distance is reserved between the microphones. And the signal processing unit determines the speed of the vehicle corresponding to the sound wave signal according to the set distance and the time information and the amplitude information of the sound wave signal acquired by the at least two microphones. When the automobile passes through the microphone, the sound wave signal collected by the microphone realizes the measurement of the speed of the automobile.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic diagram of the noise of a certain type of vehicle passing through a microphone at a speed of 45 km/h;

FIG. 2 is a diagram of the 20Hz low pass filtered noise signal of FIG. 1;

fig. 3 is a schematic structural view of a vehicle speed measurement system in embodiment 1 of the present invention;

fig. 4 is a schematic diagram of vehicle speed measurement in embodiment 1 of the present invention;

fig. 5 is a schematic structural view of a vehicle speed measurement system in embodiment 2 of the present invention;

fig. 6 is a schematic diagram of vehicle speed measurement in embodiment 2 of the present invention.

Detailed Description

In the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same or similar items having substantially the same function and action. For example, the first wireless communication module and the second wireless communication module are only used for distinguishing different wireless communication modules, and the sequence order thereof is not limited. Those skilled in the art will appreciate that the words "first," "second," and the like do not limit the number or order of execution.

It is noted that, in the present application, words such as "exemplary" or "for example" are used to mean exemplary, illustrative, or descriptive. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

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 invention aims to provide a vehicle speed measuring system and a vehicle speed measuring method.

When an automobile runs on a highway, the automobile is used as a large fast moving object, and the fluctuation of near-field pressure of the automobile can be caused during movement, so that low-frequency pressure pulse sound waves are formed. The pulse sound wave has low frequency and large energy, and is not easily interfered by other environmental noises. The higher the vehicle speed, the faster the ambient air pressure changes, and the higher the frequency of the generated pulsed sound waves, but generally no higher than 20Hz, and no overlap with ambient noise or other noise of the vehicle. The inventor finds that since the sound pressure amplitude is inversely proportional to the distance, the low-frequency pulse sound wave generated when the automobile passes can be used for identifying the position of the automobile and calculating the speed of the automobile.

Based on this, the vehicle speed measurement system that this application provided is through arranging the microphone beside the road, gathers the noise when the car passes through the microphone. And low-pass filtering the noise to obtain a low-frequency signal. And analyzing the low-frequency signal to obtain the speed information when the automobile passes through the microphone.

The following describes a vehicle speed measurement system provided by the present application

The vehicle speed measuring system includes: a signal processing unit and at least two microphones; the microphones are arranged beside a road or on the road, sound wave collecting ports of the microphones face the road, and a set distance is reserved between the microphones; and the signal processing unit determines the speed of the vehicle corresponding to the sound wave signals according to the set distance and the time information and the amplitude information of the sound wave signals from the at least two microphones.

The present application is specifically explained based on the following two schemes

Example 1

Beside the road, two microphones are arranged along the driving direction of the automobile according to a set distance D: a first microphone 11 and a second microphone 2. The microphones collect noise in real time when the automobile passes through the microphones, one of the microphones is used as a trigger microphone, and a trigger threshold value of the trigger microphone is set, wherein the trigger threshold value is exemplarily 50% of a signal peak value when the automobile speed is 20 km/h. When the noise signal amplitude reaches the trigger threshold, the signals of all the microphones are recorded, as shown in fig. 1. The recorded two sets of pulse signals (from the first microphone 11 and the second microphone 2, respectively) are low-pass filtered, respectively, with the filtering frequency set to 20Hz, as shown in fig. 2, and the filtered signals are low-frequency pulse waves.

The reason why the low frequency pulse wave is generated is as follows:

when a vehicle runs at a certain speed, the air pressure around the vehicle body is changed, so that the microphone diaphragm nearby deforms under the action of pressure waves, and a low-frequency pulse wave signal is generated. The vehicle speed can be calculated from the phase difference of the pulse waves obtained by the two microphones.

In this case, the signal processing unit (which may be a part of the analysis and display device in fig. 3) includes a first signal processing module, and the first signal processing module is configured to:

1) and calculating the time difference between the valley point of the first pulse sound wave signal and the valley point of the second pulse sound wave signal. The first pulse sound wave signal is a sound wave signal acquired by the first microphone 11 and corresponding to the vehicle, and the second pulse sound wave signal is a sound wave signal acquired by the second microphone 2 and corresponding to the vehicle.

2) And calculating the speed of the vehicle according to the set distance and the time difference.

The specific principle and calculation process are as follows:

referring to fig. 3, the car is simplified to a point sound source, and its sound pressure is kept constant, so that p is₀. When the sound source radiation sound pressure is inversely proportional to the distance, it can be known from fig. 4 that:

in the above formula, p₁，p₂Respectively a first pulsed acoustic wave signal and a second pulsed acoustic wave signal, R₁，R₂Respectively the distance between two microphones and the sound source, L is the perpendicular distance between the microphones and the sound source, alpha₁，α₂Respectively is the angle between the connecting line of the sound source and the microphone and the moving track of the sound source.

When the vehicle is positioned directly to the side of the microphone, the angle α is 90 °, and the absolute value of the sound pressure is the largest, as shown by the trough in fig. 1 and 2. Therefore, the vehicle speed can be calculated according to the time difference t between the valley points of the two microphone signals.

And determining the driving direction of the vehicle according to the arrival sequence of the valleys of the two microphones.

Example 2

As shown in fig. 5, two microphones are arranged beside the road in the direction perpendicular to the traveling direction of the automobile: a third microphone 3 and a fourth microphone 4, the distance between the microphones and the vehicle being L. The microphone collects noise when the automobile passes through in real time, and a collection trigger threshold value of the microphone is set. And when the amplitude of the noise signal reaches a trigger threshold value, recording and analyzing the microphone signal. The recorded pulse signal was low-pass filtered with the filter frequency set to 20Hz, as shown in fig. 2. The filtered signal is low-frequency pulse wave, the negative half cycle of the pulse wave is set as a sine signal, the passing time of the automobile is determined according to the negative half cycle signal of the pulse wave, and the automobile speed is further calculated.

In this case, the signal processing unit (which may be a part of the analysis and display device in fig. 5) includes a second signal processing module, and the second signal processing module is configured to:

1) determining a first distance between the vehicle and the third microphone 3 or a second distance between the vehicle and the fourth microphone 4 according to a valley point of the third pulse sound wave signal, a valley point of the fourth pulse sound wave signal and the set distance; the third pulse sound wave signal is a sound wave signal which is acquired by the third microphone 3 and corresponds to the vehicle, and the fourth pulse sound wave signal is a sound wave signal which is acquired by the fourth microphone 4 and corresponds to the vehicle.

2) Calculating the speed of the vehicle according to the first distance and the first time difference or according to the second distance and the second time difference; the first time difference is a time difference between a valley point of the third pulse acoustic wave signal and a first target point of the third pulse acoustic wave signal, and the first target point is a target point of the third pulse acoustic wave signal, wherein the amplitude value of the target point is equal to the valley valueA point earlier in time than the valley point; the second time difference is a time difference between the fourth pulsed acoustic signal evaluation point and a second target point of the fourth pulsed acoustic signal, the second target point being a point on the fourth pulsed acoustic signal where the amplitude is equal to the troughAnd a point earlier in time than the valley point.

The specific principle and calculation process are as follows:

referring to fig. 5, the car is simplified to a point sound source, and its sound pressure is kept constant, so that p is₀. The sound source radiation sound pressure is inversely proportional to the distance, and it can be known from fig. 6 that:

when the vehicle is on the line connecting the two microphones, the angle alpha₃＝α₄When the sound pressure is 0 °, the absolute value of the sound pressure is maximum.

Known as p₃(third pulsed Acoustic wave Signal), p₄(fourth pulse acoustic wave signal) and D, the vertical distance L between the vehicle travel locus and the fourth microphone 4 can be obtained.

When alpha is₃At 45 °, the distance of the vehicle from the third microphone 3 is L, and p3 is the valley valueThe point is the first target point, and the time difference t between the valley point and the first target point is measured on the third pulse sound wave signal₁And calculating to obtain:

when alpha is₄At 45 °, the distance of the vehicle from the fourth microphone 4 is L, and p4 is the valley valueThe second target point is measured as a time difference t between the valley point and the second target point on the fourth pulse acoustic wave signal₂And calculating to obtain:

this application has only been explained with the two kinds of condition that the straight line that microphone place is on a parallel with the road and perpendicular to road as the example, certainly, the straight line that microphone place can also be certain contained angle with the road, nevertheless based on the principle of this application, still can realize the measurement to the speed of a motor vehicle, and this is also in the protection scope of this application.

The passive detection method has the outstanding advantages of low cost, good concealment performance, all weather, low power consumption, simple algorithm, high precision, difficulty in interference and the like.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.