When it comes to geomagnetic detectors, there are not many people who know it in our lives, but we still have to understand the geomagnetic detectors. Today, the wireless geomagnetic detectors introduce the application range of geomagnetic detectors. And its market advantage.

1 Overview

With the acceleration of traffic construction at home and abroad, intelligent transportation has become the inevitable development direction of urban traffic management, and is an important aspect to alleviate traffic congestion and improve transportation and management efficiency. The foundation of the construction of intelligent transportation system is road traffic information collection. The excellent road traffic information collection method is the strong backing of road traffic information release and the cornerstone of intelligent transportation system.

Vehicle detection technology, as the data base of intelligent transportation, has been evolving over the years. At present, there are various vehicle detection methods in the field of intelligent transportation. The mainstream vehicle detection methods include coil detection, microwave detection, video detection, and geomagnetic detection.

Detection method Advantages Disadvantages

The coil detection technology is mature and accurate.

low cost. It is easy to be damaged by crushing the cart.

The installation process has a significant impact on reliability and longevity.

Long construction time affects traffic.

The long distance of the coil feeder affects the detection effect.

Microwave detection allows direct detection of speed.

Poor detection of low speed vehicles.

The price is high.

The debugging is complicated and difficult to use.

Video detection provides video recording for intersection traffic.

A single camera can handle multiple lanes. Not easy to debug.

The requirements for light and weather are high, and the accuracy of detection will be seriously affected by rain, snow and haze.

Large vehicles can block small vehicles that accompany them.

Geomagnetic detection has strong stability and long service life.

It is convenient to install and construct, does not affect traffic, and has little damage to the road surface.

Wireless communication, no wiring required, construction cost is extremely low. The detection accuracy can only meet the triggering and counting of the vehicle and does not meet the speed measurement requirements.

Among the above four mainstream vehicle detection methods, coil detection is the most widely used in China, but its construction is complicated, its service life is short, and it is easy to be damaged. Therefore, it has been inferior in the field of flow detection.

As the latest vehicle detection method, geomagnetic detection has been widely used in foreign countries. Due to its convenient installation and construction, geomagnetic detection has obvious advantages in the fields of traffic signal control and parking lot parking detection. At present, first-line signal manufacturers at home and abroad, such as McCann, Keli, Hisense, ZTE, etc., have used geomagnetic detectors as their main vehicle detection equipment. At the same time, geomagnetic detection is becoming more and more widely used in parking lot parking spaces.

  1. Geomagnetic detector principle

On the earth we live in, there are Earth’s magnetic fields everywhere, and the Earth’s magnetic fields vary in intensity around the world, with an average intensity of 0.05 to 0.06 mT. When there are metal objects in the space, the direction of the earth’s magnetic field will be distorted and the intensity will change. The geomagnetic detector is based on this principle. The vehicle detector uses a high-precision magnetoresistive sensor to measure the magnetic field in the space. When the magnetic field change is detected, the magnetic field change data is matched and judged with the vehicle model library, thereby performing accurate vehicle. Detection.

  1. Main components and technical parameters

The geomagnetic detection system consists of a detector and a flow detection host (receiver). The detector is buried underground, powered by a battery, and communicates wirelessly with the traffic detection host. The traffic monitoring host collects the vehicle information from the geomagnetic detector for aggregation, processing, protocol forwarding, and finally sends it to other devices, such as a signal. The wireless communication between the detector and the flow detection host uses high-performance spread spectrum technology to achieve the lowest power consumption while ensuring communication distance.

3.1. Detector

The detector uses a high-sensitivity magnetoresistive sensor to detect vehicle presence information above the lane and transmits the vehicle information to the receiver via 470M wireless transmission. In order to be suitable for vehicle detection on different roads, each detector can be set with independent detection parameters. The specific parameters are as follows:

a. Incoming sensitivity

Since the sensor used in the detector is a highly sensitive magnetoresistive sensor, it is necessary to filter the vehicle interference in the adjacent lane. The sensitivity of entering the vehicle is the basis for filtering the interference when the adjacent lanes are approaching. The higher the value, the lower the sensitivity. The entering sensitivity is adjustable from 0 to 15 levels, generally set to 4.

b. Exit sensitivity

Similar to the sensitivity of entering the vehicle, the driving sensitivity is the basis for filtering the interference when the adjacent lane leaves. The higher the value, the higher the sensitivity. The driving sensitivity is adjustable from 0 to 15 levels, and is generally set to 2.

c. Maximum time of existence

Consider the occurrence of extremely special situations, such as earthquakes, lane damage, etc. A false detection may occur when the detector encounters these conditions. The maximum lifetime is the automatic recovery time for these false detections. Can be set to 1s10~254s10, generally set to 200s10. When used in the parking lot area, the maximum lifetime needs to be adjusted to an infinitely long time because the maximum time the vehicle is parked above the detector is not measurable. At this time, if the maximum lifetime is adjusted to 255s10, the actual maximum lifetime of the detector will be set to infinitely long.

d. Entering the filter

In-vehicle filtering is a delay process when the vehicle enters the detector, which can effectively avoid repeated counting of large trucks. The input filter is adjustable from 0 to 15 levels, generally set to 5.

e. Driver filtering

The out-of-vehicle filtering is a delay process when the vehicle leaves the detector, which can effectively avoid repeated counting of large trucks. The vehicle filtering is adjustable from 0 to 15 levels, and is generally set to 5.

f. Sensor speed

The sensor rate can be set to high, medium, low, and minimum. In order to extend battery life, the sensor speed is generally set to medium. The medium rate can satisfy most applications.

The technical specifications of the detector are as follows:

a. Working environment: -40~70 °C, waterproof soaking, protection grade IP67.

b. Product size: 100mm (diameter) × 100mm (height).

c. Battery: 3.6V, continuous working for an average of 4 years or more (average 10,000 vehicles per day).

d. Receive sensitivity: -132dBm@810bps.

e. Transmit power: 100mW.

f. Wireless communication distance: 300 meters visible.

3.2. Traffic Monitoring Host

The traffic detection host has two major functions: parameter configuration and protocol forwarding. The traffic detection host can configure the parameters of the detector through parameter management software.

The technical indicators of the traffic monitoring host are as follows:

a. Working environment: -40~70 °C.

b. Power supply: 7V~24V DC.

c. Receive sensitivity: -132dBm@810bps.

d. Transmit power: 100mW.

e. Wireless communication distance: 300 meters visible.

f. Communication interface: Ethernet, RS232, CAN bus, 2-way RS485, support GPRS communication.

  1. Application scenario

4.1 Intelligent Signal Control System

The intelligent signal control system is an effective solution to traffic congestion. The geomagnetic detector provides traffic flow data for the intelligent signal light control system, and can realize various control schemes such as adaptive control of the signal light, induction control, and centralized coordinated control. The receiver has a rich communication interface and can be directly connected to each signal.

4.2 Roadside automatic notification system

Ground geomagnetic detectors are laid every 4 meters on the roadside of the key roads, and automatic monitoring of roadside violations can be carried out on all roads. When the receiving device senses the violation, it will report to the cloud server through GPRS. The cloud server can push the information to the nearby traffic police through the WeChat public platform or short message, so that the traffic police can quickly deal with the violation. The system is easy to install, debug and maintain, and has high cost performance and practical functions.

4.3 Parking lot parking space detection system

At present, parking lot parking detection systems mainly include ultrasonic detection and video detection. Ultrasonic testing requires complex wiring and is generally only available in underground parking lots. Video detection is extremely costly and not suitable for most parking lots.

The wireless geomagnetic detector eliminates the need for wiring, 24 hours of uninterrupted operation, and excellent water resistance. These features solve the problem of outdoor parking space detection. In order to facilitate the management and implementation of the geomagnetic parking space detection system, a large parking lot is usually divided into several areas, and each area is set as a parking space detection subsystem. Each subsystem includes several geomagnetic detectors and one receiver. After the receiver receives the parking space information sent by the geomagnetic detector, the parking space information data is transmitted to the cloud server for processing through GPRS.

M&T Technology is a professional equipment supplier and solution service provider in the field of smart parking in China. Products cover dynamic flow detection, static parking space detection, cloud smart parking space control system and so on. The main products include wireless geomagnetic vehicle detector, NB-IoT geomagnetic parking position detector, ultrasonic parking position detector, shared parking lock, intelligent parking lock, etc., which are widely used in urban road traffic statistics, roadside parking systems, shared parking and other fields. The Mb wireless geomagnetic parking position detector adopts dual-mode detection technology, and the precision is leading in the industry. Especially the complex application scenarios can reduce the false positive rate by 99.9%. The shared parking lock is based on the cloud platform technology architecture system design, which can realize people and vehicles. The parking space and the parking lot operator are perfectly interactive. The user can remotely realize the monitoring, management, authorized use and settlement of the parking space remotely anytime and anywhere through the cloud platform or app, and promote the development of unattended and shared parking. trend.