CN106683416B

CN106683416B - Ground sensing vehicle detector background noise removing method and device

Info

Publication number: CN106683416B
Application number: CN201710008914.6A
Authority: CN
Inventors: 李增强
Original assignee: Hit Robot Group Harbin Huacui Intelligent Equipment Co ltd
Current assignee: Hit Robot Group Harbin Huacui Intelligent Equipment Co ltd
Priority date: 2017-01-06
Filing date: 2017-01-06
Publication date: 2021-03-02
Anticipated expiration: 2037-01-06
Also published as: CN106683416A

Abstract

The method and the device can also utilize a plurality of vehicle detectors as reference modules to compare and identify the background noise with each other, so that the accuracy of the parking space information can be improved to more than 98 percent by the judging method. Meanwhile, the device is arranged in the vehicle deceleration strip, can be installed and used without being buried, and is wide in application range.

Description

Ground sensing vehicle detector background noise removing method and device

Technical Field

The invention relates to a vehicle geomagnetic detection technology, in particular to a device and a method for removing background noise of a geomagnetic sensor.

Background

The concept of smart cities is increasingly well known, with intelligent transportation being an important ring. Intelligent roads, intelligent parking lots and the like put higher demands on vehicle detection sensors. In the prior art, there are mainly induction coils, microwave technology, infrared technology, video identification, radio frequency technology, and the like. The ground induction coil vehicle detector is a main detection means for collecting vehicle parking information at present. The system aims to collect in-road parking information and immediately send signals (parking space information) to a communication base station.

The Hall linear magnetic field sensor is used as a sensor output voltage and is arranged under the road surface where the vehicle talks. When no vehicle passes by, the output voltage of the Hall linear sensor is low; when a vehicle drives to pass through the parking space from the sensor, the geomagnetic field intensity of the sensor is enhanced, and the Hall linear magnetic field sensor outputs high voltage. Whether the vehicle passes, approaches, parks or drives away is judged by comparing the change of the voltage.

Patent document 1: CN205491510U

Patent document 2: CN205194074U

Patent document 3: CN205211169U

Patent document 4: CN101383097U

Patent document 5: CN2731611Y

Patent document 6: CN2708418Y

Patent document 7: CN104076404A

As most of the prior art adopts the underground installation, the installation is not easy, the road surface is damaged, the application range is limited, the power supply is difficult to lay, and the like. Meanwhile, the geomagnetic sensor as a magnetic inductor has the defects of being easily influenced by geomagnetic background noise, high in false alarm rate and the like.

Disclosure of Invention

In view of the above problems, the present invention provides a ground sensor vehicle detector having a deceleration strip structure, which can be installed without being buried in the ground, without damaging the ground structure. Meanwhile, the characteristics of background magnetic noise are analyzed, the background magnetic noise changes slowly or disappears after appearing suddenly, and the duration is short; and the amplitude and the change rate of the magnetic change signal of the detected object vehicle are not in an order of magnitude range. Therefore, the method and the device set the background magnetic noise parameter, replace the parameter through real-time detection, screen the noise signal through the noise amplitude threshold and the time threshold, and reduce the influence caused by the background magnetic noise through an iteration mode, so that the sensitivity of the background magnetic noise to the rapidly changing magnetic field is maintained. According to the present invention, it is possible to provide a method for eliminating geomagnetic background noise and a geo-sensor vehicle detector that are easy to install.

Drawings

FIG. 1 shows an appearance structure of a ground sensing car inspection device of the present invention

FIG. 2 shows a concrete structure of a ground sensing car inspection device module

FIG. 3, modular structure of ground sensing car detector

FIG. 4 is a flow chart of a method for removing background noise of a ground sensing vehicle detector

FIG. 5 illustrates a plurality of geo-sensing car detector modules configured for the same geo-sensing car detector

FIG. 6, road surface installation and laying scheme

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Example 1, fig. 1 shows the overall constitution of the present invention. The detection device 1 comprises a ground sensing vehicle detector module 2 and a power supply module 3, and is arranged in a general deceleration strip shape, and the surface of the deceleration strip is an arc or a similar structure. The ground sensing vehicle detector module 2 is arranged between the two power supply modules 3. The top of the battery module 3 and the top of the ground sensing vehicle inspection module 2 jointly form an arc or a similar structure, the whole device is protected, and a deceleration bump can be arranged on the device. Ground is felt car and is examined ware module 2 and power module 3 and realize being connected electrically, and power module 3 is felt car and is examined ware module 2 to ground and supplies power.

The power module 3 may be an external power source, a battery, or a mechanically self-generating structure or a combination thereof. When the power module 3 is a mechanical self-generating structure, the mechanical energy of automobile rolling can be changed into electric energy.

Fig. 2 shows a specific structure of the ground-sensing vehicle inspection module 2, and the ground-sensing vehicle inspection module 2 includes a protection portion 21,

sensors

22 and 23, and a control module. The protection part 21 is a shell with an arc-shaped top or a similar structure, is of a rigid or semi-flexible structure, and can realize mechanical deformation in a local range by being matched with the power module 3. The sensor 22 may be a ground coil, a piezoelectric sensor, a metal thin film magneto-resistive type, or the like, and is capable of detecting a vehicle-carried signal. The

sensors

22 and 23 are electrically connected to the control module and are powered by the power module 3.

Fig. 3 shows a specific structure of the control module 23. The control module 23 is composed of an arithmetic unit, a magnetic signal processing circuit, a reference module, and a wireless transmission/reception module. The magnetic signal processing circuit receives the signal from the sensor 22, performs trimming filtering, and sends the signal to the arithmetic section. The arithmetic part receives the signal of the magnetic signal processing circuit and the reference signal of the reference module, then carries out arithmetic judgment on the signals, and transmits the judgment result by the wireless receiving and transmitting module. The wireless transceiving module transmits the signal to the upper computer or other reference modules and receives a control signal of the upper computer or a signal transmitted by other control modules. The reference module receives a reference signal sent by an upper computer or other vehicle detector control modules, and the signal can be transmitted by the wireless transceiving module.

The magnetic signal processing circuit receives the signal of the sensor 22, and performs trimming filtering, adopting gaussian filtering, and specifically comprising the following steps: where σ s determines the width of the gaussian function and xs is the sensor signal.

Fig. 4 shows the main operation steps of the operation unit of the present invention.

Step 1, initializing P₀、P₁、t、P_max1、P_max2，T_maxIn which P is_max1＜P_max2；

Step 2, acquiring a magnetic field signal, performing wavelet denoising on the magnetic field signal, and setting P after denoising the magnetic field signal₁；

Step 3, determining P₁-P₀≤P_max1If yes, entering step 7; if not, entering the step 4;

step 4, determining P₁-P₀≤P_max2If yes, entering a step 6, and if not, entering a step 5;

step 5, judging that the nearby vehicle moves and recording P₁-P₀；

Step 6, changing T to T +1, and judging that T is more than or equal to T_maxIf yes, making t equal to 0, and entering step 7; if not, directly entering the step 2;

step 7, enabling P₀＝P₁Returning to the step 2;

wherein step 2 is to carry out wavelet denoising on the magnetic field, and the step specifically comprises the following steps:

e. selecting a wavelet basis function and determining wavelet decomposition levels;

f. filtering the signal to obtain a wavelet coefficient;

g. performing threshold quantization processing on the wavelet coefficients according to a preset wavelet decomposition level to obtain quantized wavelet coefficients;

h. and obtaining a reconstruction signal through wavelet reconstruction filtering.

Said step c further comprises performing a threshold quantization process according to the following formula,

wherein σ is a noise standard deviation, mid (| D1, k |) is an absolute median of the first-layer high-frequency coefficient, D is an adjustment coefficient of the noise standard deviation, N is a length of a signal, and T is a wavelet quantization threshold.

Example 2, multiple detection sensor arrays were constructed, referenced to each other, as shown in fig. 5, fig. 6, or a combination of both. The reference module is added to the embodiment 1 to implement the step of coherent suppression of background geomagnetic noise by two channels or multiple channels. The reference module may be a signal sent by another ground sensing vehicle detection module 2 in the same detection device 1 or a signal sent by the ground sensing vehicle detection module 2 in another detection device 1.

Obtaining N sensor detection signals, y, respectively at a specific sampling period₁(n)、y₂(n)…y_N(n) converting it into the frequency domain Y₁(ω,k)，Y₂(ω,k)…Y_N1(ω, k), where k is the number of data windows and ω represents the signal frequency. Each frequency domain signal is coherent pairwise to obtain a common power spectrum, the power spectrum is the background noise E (ω, k), the background noise E (ω, k) is converted into the time domain E (n), and the steps 7 in the embodiment 1 are modified as follows:

step 7, enabling P₀＝min(P₁And e), returning to the step 2, and performing other normal calculations.

The ground sensing vehicle detector is arranged in a deceleration strip structure, can be installed without being buried, does not damage the ground structure, and has strong adaptability. Meanwhile, the setting parameters are changed according to the change of the background magnetic field, so that the device reduces the interference of background magnetic noise and does not influence the sensitivity of the device. I.e. attenuates slowly varying magnetic field variations, and is selectively sensitive to rapidly varying magnetic fields. Whether the magnetic field disturbance amount stably exceeds the threshold value within a certain time is detected, whether the parking space has a car is judged by comparing with the standard magnetic field disturbance amount when the car is in the parking space, and the accuracy of the parking space information can be improved to more than 98%.

Claims

1. A method for removing background noise of a ground sensing vehicle detector comprises the following steps:

step 1, initializing P₀、P₁、t、P_max1、P_max2，T_maxIn which P is_max1＜P_max2；P₀Is P₁The minimum value of e,t is an identifier counted in the flow, T_maxIs the upper limit of t;

step 2, acquiring the magnetic field signal, performing wavelet denoising on the magnetic field signal, and setting the denoised magnetic field signal as P₁；

step 5, judging that the vehicle moves nearby, and recording P1-P0;

step 7, constructing a plurality of detection sensor arrays, and respectively obtaining N through the detection sensor arrays in a specific sampling time period₁The individual sensors detect the signal(s) of the,

convert it into frequency domain

Wherein k is the data window ordinal number, and ω represents the signal frequency; coherent pairwise signals of each frequency domain to obtain a common power spectrum, wherein the power spectrum is background noise E (omega, k), and the background noise E (omega, k) is converted into a time domain E; so that P is₀＝min(P₁And e), returning to the step 2,

wherein step 2 is to carry out wavelet denoising on the magnetic field signal, and the step specifically comprises the following steps:

a. selecting a wavelet basis function and determining wavelet decomposition levels;

b. filtering the signal to obtain a wavelet coefficient;

c. performing threshold quantization processing on the wavelet coefficients according to a preset wavelet decomposition level to obtain quantized wavelet coefficients;

d. obtaining a reconstruction signal through wavelet reconstruction filtering;

where σ is the noise standard deviation, mid (| d)_1,kI) is the absolute median of the first-layer high-frequency coefficient, D is the adjustment coefficient of the standard deviation of noise, N is the length of a signal, and T is a wavelet quantization threshold;

the method is realized by a background noise removing device of the ground sensing vehicle detector, the device comprises a ground sensing vehicle detector module (2) and a power supply module (3), the overall shape of the ground sensing vehicle detector module is a general deceleration strip shape, and the surface of the ground sensing vehicle detector module is an arc or similar structure; the ground sensing vehicle detector module (2) is arranged between the two power supply modules (3), the top of the power supply module (3) and the top of the ground sensing vehicle detector module (2) jointly form an arc or a similar structure to protect the whole device, and a deceleration bump is arranged on the top of the power supply module; the ground sensing vehicle detector module (2) is electrically connected with the power supply module (3), and the power supply module (3) supplies power to the ground sensing vehicle detector module (2); the power module (3) is an external power supply, a battery, or a mechanical self-generating structure or a combination thereof; when the power supply module (3) is in a mechanical self-generating structure, the mechanical energy of automobile rolling can be converted into electric energy; the ground sensing vehicle detector module (2) comprises a protective part (21), a sensor (22) and a control module (23); the protection part (21) is a shell with an arc-shaped top or a similar structure, is of a rigid or semi-flexible structure, and can realize mechanical deformation in a local range by being matched with the power module (3); the sensor (22) is a ground induction coil, a piezoelectric sensor or a metal film magneto-resistance type sensor and can detect a vehicle motion signal; the sensor (22) is electrically connected with the control module (23) and is powered by the power supply module (3).

2. The method according to claim 1, wherein the control module (23) is composed of an arithmetic part, a magnetic signal processing circuit, a reference module and a wireless transceiver module; the magnetic signal processing circuit receives the signal of the sensor (22), and the signal is renovated, filtered and sent to the arithmetic part; the arithmetic part receives the signal of the magnetic signal processing circuit and the reference signal of the reference module, then carries out arithmetic judgment on the signals and transmits the judgment result by the wireless transceiving module; the wireless transceiving module transmits the signal to the upper computer or other control modules and receives the control signal of the upper computer or the signal transmitted by other control modules; the reference module receives a reference signal sent by an upper computer or other control modules, and the reference signal is transmitted by the wireless transceiving module.