With the rapid development of radio technology, millimeter-wave radar sensors have gradually become an important research field for intelligent security systems. Millimeter-wave radar sensors play an important role in intelligent security systems and have the advantages of strong anti-interference ability, high precision, and remote measurement. At present, the millimeter-wave personnel monitoring radar based on the moving target detection and tracking algorithm of the millimeter-wave radar sensor is increasingly used in intelligent security monitoring fields such as platform early warning, pedestrian monitoring, intelligent security, intelligent elderly care, and intelligent communities.
Millimeter wave is an electromagnetic wave that works in the millimeter wave band, with an operating frequency of 30 to 300 GHz and a wavelength of 1 to 10 mm. The wavelength of millimeter wave is between microwave and infrared, so millimeter wave radar has some advantages of microwave radar and photoelectric radar. In addition to millimeter-wave radar, personnel monitoring sensors also include lidar, ultrasonic radar, and cameras.
The camera has a wide detection range, a large amount of monitoring information, and can be telemetry, but the data calculation is large, the transmission bandwidth is large, and it is easily affected by weather and obstructions.
The ultrasonic radar ranging method is simple and low in cost, but its transmission speed is easily affected by the weather, and the ultrasonic scattering angle is large and the directionality is poor. When measuring long-distance targets, its echo signal is weak, which affects the measurement accuracy.
Lidar has high measurement accuracy, but is easily affected by natural light or thermal radiation. When the natural light is strong or the radiation area, the lidar will be greatly weakened, the cost of the lidar is high, and the technological level is high.
Millimeter-wave radar sensors can directly obtain depth information, without the influence of external environmental factors such as light, heat, fog, smoke, dust, etc., strong anti-interference ability, good environmental adaptability, and will not reveal personal privacy. Its measurement accuracy and stability are better than those of cameras and ultrasonic radars, and its technological level requirements and costs are lower than those of lidars, and it has higher commercial application value.
1. Intelligent security: personnel counting and trajectory tracking
The personnel monitoring radar is based on the millimeter-wave chirp millimeter-wave radar module, and adopts the millimeter-wave chirp millimeter-wave radar module FMCW, MIMO and other technologies. It can achieve high indoor speed measurement accuracy, high angle measurement resolution, and low false alarm rate. Accurately monitor outdoor multi-scene, multi-target people, accurate positioning and stable tracking, effectively distinguish people from non-persons, count the number of targets, and output multiple targets stably Information such as distance, speed, and angle between people.
1. Personnel monitoring and quantity statistics
Personnel monitoring and quantity statistics are indispensable data in many existing scenarios, such as airports, shopping malls, chain stores, stations, museums, in conference rooms and other occasions. Personnel discovery inventory and data estimation play an important role in safety management and improving overall service levels. important role. In the existing people counting applications, it mainly includes camera identification, infrared identification, traditional manual inventory, automatic inventory mechanical equipment and rfid access control system. However, these methods are limited by cost, accuracy, and difficulty of implementation, making it difficult to balance economy and accuracy for people counting applications. The use of millimeter-wave radar sensors can make up for these shortcomings of people counting and has broad application prospects.
The millimeter wave radar sensor can obtain the current speed and position of the target person by calculating and analyzing the electromagnetic waves reflected by the moving target person in the monitoring area, and realize the trajectory tracking while outputting the speed and position of the target person. In addition, by analyzing the location of the target person, it can be judged whether the target person has entered the drawn monitoring area, and the number of targets monitored in each area can be counted and output.
2. False alarm elimination and tracking
Comprehensive millimeter wave radar sensor personnel monitoring radar FMCW, MIMO using static object elimination algorithm and other technologies. Human and non-person distinction algorithm, multi-path interference elimination algorithm and multi-target tracking algorithm, effectively distinguish people and other objects, eliminate false detection, and achieve indoor Tracking and recognition of multiple objects in the environment.
The static object elimination algorithm is mainly used to eliminate static objects (such as walls, tables and chairs, etc.) in the indoor environment, and the algorithm involves a signal processing module and a data processing module. By eliminating zero-Doppler channel targets, static objects can be filtered to avoid static objects from interfering with moving targets.
The algorithm for distinguishing between people and non-characters is mainly used to distinguish between people and micro-animals (such as rotating electric fans, floating curtains, etc.). The algorithm for distinguishing people and non-persons will count the characteristics of people and micro-animals, extract effective features, distinguish targets, and only output the tracking results of the target people.
The multipath interference elimination algorithm is mainly used to eliminate false detection points caused by target motion in indoor scenes, so as to avoid these false detection points being mistaken for the target by the millimeter wave radar sensor for tracking output, resulting in false alarms. The algorithm will make a comprehensive judgment based on the indoor environment area and the original detection point information (such as distance, speed, angle and signal-to-noise ratio, etc.) obtained by the millimeter-wave radar sensor to determine whether the original detection point is a false point, thereby filtering out, Greatly reduces virtual alarm problems caused by multipath in indoor environments.
The multi-target tracking algorithm is mainly used to accurately locate and stably track multiple moving targets in an indoor environment. The algorithm first effectively clusters the original detection points to obtain different target clusters, and then uses the extended Kalman filter algorithm to track different clusters to obtain stable moving target trajectories.
2. Platform early warning: Intrusion monitoring and early warning at the end of the platform
With the basic completion of the "four horizontal and four vertical" high-speed rail network, the number of platforms and passages at each hub station has increased, the number of operating vehicles has increased, the departure interval has been shortened, and the density of people's flow has increased simultaneously. In addition, there will be passengers who try to escape fare evasion and invade the railway line through the end of the platform, which will not only bring great safety risks to passengers, but also affect the order of railway operations.
At present, the protection of the end of the platform generally adopts the way of on-duty personnel on duty around the clock. Each station can only increase the number of inspectors and increase the frequency of inspections to ensure safe operation. However, based on manual inspection, the centralized supervision of the safety management of the station building is realized in the form of intercom and telephone in emergency situations. In view of this form, the station-side intrusion alarm system came into being. The intrusion alarm system on the platform side can realize all-weather and automatic monitoring on the platform side, saving manpower and material resources. Combined with the video system, the historical video of the corresponding time of the alarm record can be called up at any time, which is convenient to prove the intrusion, limit the behavior of passengers on the platform, and play a deterrent role.
As the technical core of the intrusion warning system at the end of the high-speed railway platform, the measurement sensitivity and accuracy of the intruder monitoring radar of the millimeter-wave radar sensor determine the timeliness and reliability of the entire intrusion warning system. Personnel monitoring radar millimeter wave adopts MMIC integrated radio frequency solution with good stability and reasonable cost; combined MIMO multi-antenna design, beam forming (DBF) technology, strong echo direction and wide coverage; innovative column optimizes and adjusts power distribution to achieve greater gain , to ensure the sensitivity and accuracy of radar measurements. In addition, the radar also has the functions of automatic start calibration and temperature compensation, strong anti-interference ability, and the center frequency does not drift, ensuring that the radar monitoring is not affected by wind, light, temperature changes and interference from external environmental factors such as smoke, fog, dust, etc. Accuracy and stability of radar measurements.
According to the needs of the station, set up multiple personnel monitoring radar detection lines perpendicular to the direction of the track at the end of the station where intrusion detection is required to track the trajectory of intruders in the monitoring area in real time, and cooperate with cameras for real-time monitoring, which is convenient for the management center staff to monitor and warn in real time. and subsequent violations. When someone illegally crosses or destroys the first line of defense, the millimeter wave radar sensor can immediately detect the intrusion information and convince the police of the situation through the intrusion alarm master controller or the local alarm voice; when someone illegally crosses or destroys the second line of defense, the radar can detect the intrusion information. Immediately detect the intrusion information, transmit the alarm to the back-end platform management center through the intrusion alarm master controller, the management center receives and processes the alarm signal, and the client displays the location of the intrusion alarm platform; at the same time, the management center and the on-site external sound alarm start to alarm , the terminal monitoring picture pops up on the computer screen. The on-duty personnel of the command center can persuade to retreat through the voice walkie-talkie. At the same time, the management center and the on-site external sound alarm began to alarm, and the terminal monitoring picture popped up.
