| When there is a water accident for a civil aviation aircraft,the aviation life preservers are the main life-saving devices that ordinary passengers can rely on.However,the conditions at sea are complex and changeable,affected by many factors such as tides,currents,and wind in the water.The victim may float for several nautical miles at sea with irregular drifting direction in just a few hours.In general,the victim who falls into the water may only expose one-third of the head or body on the water.Even if the weather conditions are good,it can only search 500-600 meters by visual observation.The visibility is poorer at night,which shows that positioning performance is very important for life preservers.Based on this,the BDS/GPS dual-mode life-saving positioning system is proposed in this study.This system uses the positioning module to accurately locate the person who fell into the water and uses the AIS signal to transmit position information,which can greatly improve position performance of the aviation life preserver.Obviously,this system can help to save the rescue time and improve rescue efficiency.This article mainly focuses on the dual-mode positioning system of the life preserver.The whole positioning system is fixed on the upper part of the airbag of the life preserver,consist of an active antenna,a BDS/GPS dual-mode positioning module,a STM32 control module,a AIS code modulation module,an integrated VCO phase locked loop frequency synthesizer and a power amplifier.Once the life preserver comes into water,the water activated battery automatically turns on to provide energy to the dual-mode positioning system.After the active antenna receives BDS/GPS satellite signals,the positioning module receives the positioning information,and transmits it to STM32 control module,which intercepts and analyzes the signal information,and then converts into the standard AIS message.The active antenna can send the AIS message,which may be received by the AIS receiver at the end of the ship passby.By comparing with the sea chart,the ship passby can determine the specific location of the victim and take rescue measures.The main work of this paper is as follows: firstly,the BDS/GPS dual-mode positioning and AIS technology are introduced.Based on this,the technical route planning and overall design of the dual-mode life-saving positioning system are carried out.Secondly,the positioning module,control module,and AIS code modulation module and the phase-locked loop frequency synthesizer with integrated VCO are reasonable selected and designed.Among them,the phase-locked loop frequency synthesizer with integrated VCO is the core job with a test board making and testing.Thirdly,the programs of the system are designed.These program including the overall process of the search and rescue system,the NMEA-0183 protocol and the corresponding sentence format,data transmission program,positioning information interception and parsing program,phase-locked loop module program,AIS message modulation coding and message sending process.The paper also tested part performance of the system,including the positioning performance of the BDS/GPS dual-mode positioning module,data transmission,and the phase-locked loop module test board.The test results show that the system has good positioning performance,good data transmission performance,and the test board can output a relatively pure output spectrum.The research in this article will help to improve the position performance of aviation inflatable life preservers,ensure the safety of passengers in the case of aircraft water-related accidents,and increase the probability of rescue. |
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