Reserch On Down-looking Radar System Of Helicopter

In recent years,with the rapid development of domestic helicopter industry,helicopter has been more and more widely used in our modern society,including emergency rescue,disaster relief,geological exploration and so on.When a helicopter carries out search and rescue missions or other urgent tactical tasks,the landing site may be temporary and unpredictable.Rain,fog,smoke and all kinds of unpredictable obstacles will cause the helicopter pilot's sight to be blocked,which may lead to dangerous occurrence.In this paper,a ground obstacle detection device with penetrating ability is studied to help helicopter pilots detect landing sites,enhance helicopter pilots' perception of ground conditions,and assist helicopter landing safely.Through the comparative study of infrared,laser,radar and other imaging methods,millimeter wave radar imaging has the advantages of all-weather work,strong penetration,less impact by rain and fog and other external environment.The aim of this paper is to study a ground obstacle detection equipment based on millimeter wave radar technology.By analyzing the landing characteristics of helicopter and the requirement of landing site,the key technical indicators of radar are defined,including detection range,scanning range,range resolution,etc.The installation environment,working frequency band,working system and imaging requirements of radar are further studied.After that,the radar sensor is studied deeply.The monopulse high-precision angle measurement technology and range high-resolution technology are studied by using 3 mm linear frequency modulation wave.The servo system scheme and imaging plan are worked out to enable the system to penetrate sand,dust,snow,fog,rain and smoke under the condition of line-of-sight obstacle,and the obstacles in the landing field are also studied.Complete the detection.Provide real-time and accurate 3D or two-dimensional view of landing site for pilots.The range high resolution technology is deeply studied.The characteristics and engineering difficulties of LFM signal,stepped frequency signal and stepped LFM signal are compared and analyzed.High precision angle measuring technology is studied,including amplitude and phase methods.In the design process of radar system,both AGC control and antenna servo control need to establish a stable output control system.This paper makes a thorough study on it,and establishes a comprehensive algorithm combining PID and linear algorithm.The simulation and practical verification show that the algorithm can solve the contradiction between the initial response speed of gain,energy jitter and the sudden change of gain.It is well applied in AGC control and antenna servo control.The down-looking radar system in the scheme has complex composition,expensive millimeter wave devices and long development cycle.In order to improve the development efficiency,a system verification platform is built,including radio frequency generation,reception and signal data processing.Through this platform,the principle of radar is verified quickly,and the key technologies such as radar detection range are simulated.This paper completes the technical scheme of down-looking radar for assistant helicopter landing,focuses on the radar sensor part,builds a verification platform and completes the verification of radar system.The verification results show that the designed down-looking radar can complete the obstacle detection of helicopter landing site,assist helicopter landing,and achieve the desired research objectives.