Life Detection Technology Types and Development History

Since the last century, some countries have begun to conduct research on life exploration technology. Generally speaking, the life detector is based on the principles of physics such as electromagnetic waves, sound waves, and light waves, and converts the physical signals into electrical signals through dedicated sensors, and then filters and amplifies them to output visual or audible signals. These components can be searched and detected. , looking for life equipment .

Life detectors are classified according to the detection function and can be divided into direct life detectors and indirect life detectors; they can be classified into active life detectors and passive life detectors according to the detection methods; they can be divided into terrestrial probes and underwater objects according to the detection environment. Detecting life detectors, etc.

In terms of detector research, the United States and Germany started earlier and developed more comprehensively and systematically. Because Japan is a country with many earthquake disasters, its detection technology for earthquake rescue has developed rapidly. Russia’s technology is also more advanced. China has gradually increased its research in this area since 2000 , and it is only at the initial stage.

1 sound and video life detector

The audio life detector applies the basic principles of audio sound waves. People who are trapped, shouted, crawled, beat, etc. emit audio sound waves or shock waves, which are received, filtered, and amplified by highly sensitive sensor probes and can be heard directly by rescuers .

Audio Life Detector has now developed into the fourth generation of products. Fire and rescue personnel from more than 10 countries , including the United States, Britain, France, Japan, Singapore, and Israel , are currently using audio life detectors to find trapped lives. Such as the United States 80M 287612 mini audio life detector, the detection frequency of 1 ~ 3000Hz , can receive two sensor information at the same time, the spectrum shows two sensor information, and equipped with a small walkie-talkie , can directly dialogue with the trapped. More commonly used in the market is a French-made audio life detector. As shown in Figure 1.1 , the instrument uses two extremely sensitive audio vibration detectors to identify tiny vibrations that propagate in air or solids. It is suitable for searching for survivors trapped under concrete, rubble, or other solids, and can pass through. The audio transmission system establishes contact with the people who are buried. The instrument uses two audio filters to filter the surrounding background noise, effectively shielding the noise generated by heavy trucks or other heavy machinery from the rescue site.

Because the audio life detector is an instrument that passively receives audio sound waves, this type of detector has certain limitations and is easily affected by the noise in the field, and the detection speed is slow. Video life detection is mainly to use the camera for visibility detection, which can be simply understood as a “gastroscope”. It can be intuitively discovered that trapped persons are caught by the probe penetrating into the small gaps in the disaster scene [1] . Due to the pixel height of the imaging unit, the diameter of the probe, the length of the probe, and whether the probe can be rotated, the applicable range is not the same and the price is not the same.

The video-based life detector used in the rescue is sturdy and lightweight, making it ideal for rescue search operations in collapsed buildings or in narrow spaces. The instrument provides rescuers with information on trapped people under the rubble through high-definition video signals. Its sensitive professional camera can quickly capture a clear picture of 2m away in a completely dark environment . The lens can rotate 360 degrees. The instrument is equipped with a three-way communication system that can effectively pacify trapped persons through translators. China started late in audio and video integration, but is good at learning foreign advanced technology. Its independently developed DVL-360 full-angle audio and video life detector has better performance and is cheaper than foreign products.

DVL-360 full-angle audio and video life detector is small in appearance and suitable for rescue search operations in collapsed buildings or in narrow spaces. The detector uses high-definition video and audio signals to find information about victims under the rubble and establish audiovisual links. Easy to use and intuitive. Audio detection uses a high-sensitivity audio acquisition system with a detection range of 12m2 . The video detection range is in full darkness and the probe can be rotated 360o . The instrument rechargeable battery can be used continuously for more than 4 hours.

Video life detectors must have large or small holes or cracks in the scene to allow the probe to protrude into the interior. The fiber probes are easily contaminated by soil and cause unclear images. Therefore, they are also subject to certain restrictions in use. limit. Video life detectors are integrated with audio life detection and are used in combination with poor efficiency. They are generally only used to determine the specific location of survivors.

2 infrared life detector

The infrared life detector can withstand the harsh conditions of the rescue site, detect the heat of the victim's body, use infrared detectors, optical imaging objectives to convert infrared radiation energy into electrical signals, and display the infrared heat through the TV screen or monitor after processing. Like the map, thus helping the rescue team quickly determine the location of the victims buried under the rubble or behind the dust , with the name “angel's eyes” [4] . At present, the technology of infrared life detector is relatively mature, the price is relatively low, and the good price/performance ratio promotes that it is generally equipped in the rescue and rescue departments of various countries and has a wide range of applications.

After the Second World War, after nearly a year of exploration, the US-based Dexarlan Instrument Company developed and developed the first-generation infrared imaging device for the military field, which is called the infrared search system ( FLIR ). In the early 1960s , the Swedish AGA company developed a second-generation infrared imaging device. This device adds the function of temperature measurement based on the infrared look-up system, which is called an infrared thermal imager . After several improvements, the full-featured thermal imager introduced in 1988 has integrated temperature measurement, modification, analysis, image acquisition, and storage. The function, accuracy and reliability of the instrument have been significantly improved. In 2004 , a sub-millimeter wave thermal imager was successfully studied at the University of Moscow, Russia [3] . Submillimeter waves still belong to heat waves, but they have unique performances and can penetrate obstacles such as walls that cannot be penetrated by ordinary infrared rays. The system uses photolithographic technology to make ordinary semiconductor materials into a cake-like layered structure. The sub-millimeter waves emitted by the target after capturing the obstacle are designed so as to be further converted into images.

The infrared life detector used at this stage includes the American M271328 infrared life detector, which is convenient and lightweight. It can not only find the injured miners, but also find the victims. At the same time, because it can accurately measure the temperature remotely, it can directly show the distribution of the surface temperature of the coal seam. The complete digital compass on the screen shows the visual direction so as to accurately locate the location of the victims for quick rescue. From a 36- degree angle of view, not only can a quick scan of the ruins be performed at a safe distance, but it can also be effectively searched indoors.

The infrared life detector designed and manufactured in China is explosion-proof sy-250 . Infrared detection plays a very important role in monitoring the local temperature and mine disaster rescue, and can be used normally in the dark.

Sy-250 detector is a high-performance life testing instrument integrating infrared physics, infrared photoelectron technology, image processing technology, micro computer technology and coal mine explosion-proof technology. It is mainly used to detect the distribution of invisible fire zone in underground coal mines and non-contact detection of potential accidents of various switch joints underground. The instrument can automatically capture the maximum temperature and minimum temperature displayed on the screen, with a semi-transparent menu display, the operator can observe the entire infrared heat map in the analysis mode. The front end of the instrument is equipped with a laser positioner, which can accurately measure the specific position of the observation target.

3 gas sensitive life detector

According to the principle of human exhalation of carbon dioxide, when the gas concentration in a certain space on the search site rises above 1100 ppm , the gas-sensing life detector can detect the presence of human or animal signals. The detector is suitable for basements, containers, confined spaces and other places. It is not necessary to dig underground or open containers, doors and windows. It can search for life goals. It is easy to operate and maintain. The detector uses a basic AA battery for low cost and up to 12 hours of battery life . During the Wenchuan earthquake, Japanese rescue teams dispatched to China carried such an instrument.

4 Ultra-low frequency electromagnetic life detector

The ultra-low frequency electromagnetic life detector uses the ultra-low frequency electromagnetic energy generated by the human body's heartbeat to perform life detection [5] . The life detection system adopts a passive working method and does not produce sound when working. It can not only be discovered by the other party, but also can determine the exact position of a person through metal, walls, and deep water. The polarization filter in the system can filter out other clutter signals arriving at this device, and can effectively distinguish the ultra-low frequency signals generated by humans and other animals [3] .

The DKL life detector in the United States has been developed with cutting-edge biochemical, dielectric, ultra low-frequency transmission and DNA technology. Each beat of the heart produces a weak electric field signal, which constitutes an ultra-low frequency non-uniform electric field that expands 360 degrees around the human body . Every part of the human body has an effect on the electric field, but the electric field behavior around the heart is the main electric field. The detector's filter circuit allows only a non-uniform body electric field to polarize the special dielectric material in the life detector. When the life detector penetrates the body electric field, the dielectric material is polarized, positive and negative charges are separated, and are collected at both ends of the device, respectively. The life detection antenna points to the strongest part of the non-uniform electric field. The DKL is equipped with a special radio wave filter that filters out other animal frequencies that are different from humans, allowing the DKL life detector to sense only the frequencies that humans emit. The detector can detect distances up to 500m from open spaces and water levels up to 1km . 5 Electrostatic Field Life Detector The electrostatic field partition wall detector developed by the U.S. Army for special forces is designed using the attractive principle that the human body can produce an electrostatic field and two electrostatic fields with opposite polarities. This instrument can be used normally when the wind speed is less than 9s/m , and it can detect the target from 120 to 140m from the interior wall. The system weighs 0.45kg , is powered by 9v battery and can be used for 3~4 days. The detector consists mainly of a modular array of antennas, including corner reflectors, directors and amplifiers. When using, just hold the device in a suspicious direction, or scan around. When scanning the human body signal, the static field of the detector and the electrostatic field of the human body generate an attractive force, pulling the antenna to the strongest direction of the electrostatic field. The direction is the hidden direction of the enemy. Tests have shown that the detection range of the system is related to the nature of the screen and the changes in the operator's hand. The experimental results show that when the detected person is behind a screen such as a wall, the detection distance is only 10%~20% lower than that without the screen . However, due to the difference in the operation direction and the electrostatic field of each person, there is a large gap in the detection effect.

6 radar wave life detector

6.1 Characteristics of Radar Life Detector

Radar life detector is currently the world's most advanced life detection instrument. Its active detection method makes it less susceptible to adverse factors such as temperature, humidity, noise, site topography, etc. The continuous emission mechanism of electromagnetic signals has increased its area. Sex detection function.

Compared to other types of detectors, radar life detectors have their own unique features:

1 . Instant motion detection can be done through concrete, brick, snow, ice and mud.

2 . Can detect motion.

3 . Can detect the distance of the person in danger.

4 . Works in all climate conditions.

5 . The demand for power supply is low, and almost no system maintenance is required.

6 . Firmware programs can be upgraded over wireless or wired networks.

7 . There is no need to drill holes, arrange cables, and mute the environment to make search and rescue work simple and easy.

At present, the development of radar life detection instruments is not perfect, and there are many problems in the processing of many key technologies. At present, the price of radar life detectors is relatively expensive, at hundreds of thousands.

6.2 Overseas Research Status

Late, American, German researchers began to study the life detection radar will be the last 1980s. The parabolic antenna structure detection system was used at the Atlanta Olympics to study the effects of breathing and heartbeat firing accuracy on rifle and archery athletes. The system monitors the athlete's heartbeat 10 meters away. In the late 1990s, in order to meet law enforcement requirements, the United States began to develop a flashlight radar life detector [7] . Flashlight radars can detect people hidden behind concrete walls, wooden walls and steel doors. The flashlight radar system combines Doppler radar technology with high-speed signal processing technology, and uses a fast Fourier transform and a very steep frequency response curve filtering function to extract signals unique to the human body from cluttered echo signals. The system uses a commercially available antenna as a microwave lens that concentrates the output beam in a fan zone of 15-20 degrees. The flashlight type radar is used to detect the tiny movement of human chest caused by heartbeat or breathing. The system's signal processor mainly acts as a low-pass filter, which makes it impossible for the frequency above the preset maximum heartbeat frequency to pass. Therefore, the human body Very weak movements can be detected.

It is Michigan State University in the United States that has achieved relatively great results on the radar life detector . They carried out research on the detection of human respiration and heartbeat movement in the bands of 10 GHz , L -band 2 GHz and 1.15 GHz , UHP band 450 MHz , and achieved some more valuable results. In the x -band carrier-frequency 10 GHz life detection system, when the transmitting power of the antenna is 4.5 mW , the breathing and heartbeat signals in a sleeping posture of 30.48 meters outside the free space can be found . When the transmission power is increased to 20mW , a 25cm concrete wall can be penetrated and the heartbeat and breathing signals of a person seated on a stool can be detected.

At present, more American products are used for Radford radar life detectors [6] . The Rayford detector can help the fire rescue personnel find the target within 30 seconds and confirm the trapped person within 2 minutes. The entire device consists of a radar signal transmitter and a computer. The radar transmitter uses ultra-wideband transmission technology to transmit radar waves, and transmits the signal to the computer in a wireless manner. The computer embeds hundreds of human chest breathing dynamic data signals, and after receiving the signal clutter processing and waveform comparison, it directly gives signs of whether there are signs of life. The detector features: no probe, no cable, small size, light weight, convenient on-site installation, simple operation, precise positioning, sturdiness and durability, waterproof function, can operate in rainy days.

6.3 Domestic Research

China's research on radar wave life detection technology started late. In 1998 , the research team of the Department of Biomedical Engineering of the Fourth Military Medical University began to study this topic. In 2003 , the research group of the Fourth Military Medical University developed the prototype of the S2000-I equipment for the detection of the wounded and designed a set of wounded personnel by using the experimental platform of the millimeter-wave and decimeter-wave radar systems and using the detection method based on FFT frequency domain accumulation. Detecting living organism identification systems. However, the recognition accuracy rate decreases with the decrease of the signal-to-noise ratio, and advanced signal processing technology is required to improve the performance of the entire system.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.