English 
Views: 84 Author: Site Editor Publish Time: 2019-05-28 Origin: Site
Unmanned Aerial Vehicle, abbreviated as "UAV", is a non-manned aircraft operated by radio remote control equipment and independently developed program control devices or operated by the onboard computer autonomously or intermittently. Compared to ordinary pilot aircraft, UAVs are more suitable for dangerous missions. UAVs can be divided into military and civilian drones depending on the field of application. Generally, in maritime search and rescue operations, drones or manned aircraft are often used to quickly search for targets at the scene of accident and then carry out rescue activities by low flying in the target area. At the same time, the on-site situation can be sent to the command center in time by the drone digital wireless transmitter, which facilitates the formulation of the rescue strategy and coordination with the passing vessels.
The first time that drones were used to perform search and rescue work was in the 2008 freezing disaster. In the same year in Wenchuan earthquake, drones were also used as aerial photography tools in earthquake search and rescue work. In recent years, drones have been frequently used in various disaster sites to provide reliable information for rescue work. The outstanding performance in search and rescue and unique advantages have made people pay more and more attention to drones and the related technologies have also been greatly developed such as low-altitude remote sensing technology, long-distance video and data wireless transmission technology, flying Control technology and engine improvements. The continuous development of various technologies has made the application of drones more common and gradually applied to maritime search and rescue work. At the same time, drone’s search and rescue application is transforming into a systematic and specialized direction. For example, some departments in China have established an integrated search and rescue system. When an accident occurs, the drone can quickly carry out accident site detection and information collection sending to the command department. Then the command department will makes targeted relief measures.
With the tremendous advancement of high-definition video shooting, low-altitude hovering, remote controlling and COFDM long-distance video transmission technology, the development of drones has reached an unprecedented level. At present, there are three types of drones in China that always are used for maritime search and rescue work:
1. Maritime Search and rescue drones. Its power system can boost the drone by buoyancy, which cam greatly reduce the fuel consumption and enhance its endurance. In addition, it also could achieve air hovering and has low requirements for lifting sites with rising and falling on large ships at critical times.
2. High altitude and long-haul drones. This type of drone has a long endurance for long-distance navigation and high vertical fly height for long time high altitude flight work . In addition, high-altitude flying can effectively avoid the harsh natural environment. These excellent features make this type drone not only always used for offshore search and rescue work, but also for long-range maritime search and rescue work.
3. Ground effect drones. It is also very suitable for maritime search and rescue. Such drones can carry out simple take-off and landing on the sea during rescue work. Moreover, it also has a high carrying capacity for the salvage materials delivery. At the same time, the drone is equipped with high-definition camera, remote operating system and long-distance transmission system making it more widely used. For example, it can be used for sea area traffic monitoring, ship navigation route re-enactment, sea area pollution monitoring and accident reporting. In addition, the long-distance transmission function can be used to provide the sea management department with instant information to facilitate the maritime management department to carry out emergency response processing and flow control of vessels. Thereby effectively protect the safety of maritime traffic.
Unmanned Aerial Vehicles do not need the driver's control so the cost of installation the cockpit-related control device, the safety life-saving device and training and educating a large number of aircraft and ship operators can be eliminated. In addition, the development, production and maintenance costs of drones are much lower than those of search and rescue vessels and manned aircraft. Take the 45-meter patrol search and rescue ship as an example. It takes about two hours to go back and forth from the starting port to the destination. The cost of two-hour patrolling includes 500 kilograms fuel, staff salaries and ship loss. However the patrol of one drone from the starting port to the destination is around 35 minutes and the fuel consumption is very small. Therefore, UAVs is not only efficient in operation but also low in cost, so it is very suitable for supervision under normal conditions.
Drones are light and small. Fixed-wing drones require short slip distances for take-off and landing. So ordinary roofs and playgrounds can meet their take-off and landing requirements. On the other hand, the drone's operation is very simple. The navigation route can be set in advance through the ground station and a suitable flight attitude and flight altitude can also be adjust according to actual needs by flight control command data wireless sending via the wireless transmission system.
UAV search technology combines RF technology with personal positioning search to achieve long-distance search and rescue. This search system is mainly composed of seven parts: drone, high-definition camera, UAV video transmitter, positioning search and rescue device, beacon, detector and ground station. The beacon is the most critical. The application of the system for search and rescue at sea requires a beacon device in the crew's life-saving equipment. During the search and rescue process, the UAV-loaded equipment can activate the beacon within 15 km range, send back the accident crew information and quickly perform satellite positioning. Compared with the traditional search and rescue vessels, the UAV positioning search and rescue has the advantages of wide vision, high efficiency, all-weather and high mobility. The drone can also take instant photos of the accident vessel through the high-definition camera and timely transmit the photo information to the rescue command center through the drone long range video transmitter so that the relevant staff can be rescued in time.
FIM-1440 is a 50km long range wireless transmission module designed for fixed wing drone, VTOL and Long range UAV to transmit HD video. It adopts COFDM(Coded Orthogonal Frequency Division Multiplexing) technology, which currently is the most advanced and most promising modulation technology in the world. Its practical value lies in breaking the limitation of line of sight distance and it is a technology that is fully utilized in radio spectrum resources and can have good immunity to noise and interference. Diffraction and penetration occlusion are the core of COFDM technology. The superior "diffraction" and "penetration" capabilities enable the UAV Video transmitter to achieve stable video transmission with high probability in the environment that is invisible and obstructed such as in urban areas, mountains and inside buildings without being affected by the environment.
Advantages
Ø Modulation: DVB-T/DVB-T2/DVB-T2
Ø Frequency: 300Mhz-1.4Ghz
Ø Distance: 50km(Air to ground), 1-2km NLOS(Ground to ground)
Ø Latency: 50ms
Ø RF Power: 2.5Watts
Ø RX Sensitivity: -103dbm
Ø Data Rates: 1.5/3/6Mbps
Ø Bandwidth: 2/4/8MHZ
After discovering the accident vessel and the distressed person through the search and positioning system, the drone equipped with the long-distance UAV video transmission system can transmit the situation video to the command department in time through the loaded high-definition camera so that the search and rescue personnel can be timely make reasonable search and rescue measures to improve search and rescue efficiency and success rate.
Most of the marine accidents in recent years have been small vessels and ships that transport sand and stones. The life-saving configuration on such type of ship is very simple. Therefore, in the event of an accident, the search and rescue patrol ship is difficult to find them accurately, which greatly reduces the search and rescue rate. Furthermore, the environment on sea is complex, facing hunger and injury, people in distress can be life-threatening at any time. In this case, the drone application is very important. Drones can be equipped with the necessary food, fresh water and medical equipment for delivery to make the search and rescue efficiency greatly improved.
In summary, the development of drone technology has met the needs of current maritime search and rescue activities. In addition, drone search and rescue has the advantages of low cost, flexibility and high efficiency. The drone can transmit the situation of the vessel in distress to the command department in real time through the long-distance video transmission function, which makes it easier to formulate and carry out search and rescue activities. Therefore, the application of drones in maritime search and rescue has greatly improved the efficiency and should be widely applied. Although there are still some defects in UAVs today, we believe that under the efforts of researchers, we will be able to overcome these problems and make UAVs better used in search and rescue.
