Research On Detection Method Of Power Line Position And Relative Velocity Of Helicopter Anticollision Line System

Helicopters are playing an increasingly important role in both military and civil fields because of their excellent flight performance,such as taking off and landing in a small space area,hovering in the air,maneuverability and flexibility.In the military field,armed helicopters are usually used to attack the enemy’s military facilities.In order to prevent premature exposure of helicopters when approaching targets,pilots usually fly in ultra-low altitude to avoid enemy radar detection.When flying at low altitude,the collision of high-voltage power lines at low altitude is likely to occur because they are not easy to be found.In addition,in the civil field,especially in natural disasters such as earthquake relief,helicopters are usually used to search and rescue,transporting wounded people,transporting relief materials and equipment.These tasks also need helicopters to carry out at low altitude,and accidents of low altitude flight colliding with power lines are common.This paper focuses on the identifying of power line position and the measurement of early warning time of helicopter collision line system.Firstly,the parameters of detection distance,elevation angle and azimuth angle of beam scanning involved in the anti-collision line system are analyzed.RCS of power lines with different radii,frequencies and lengths is simulated.According to the simulation results,we can calculate the effective length of power lines detected in the air by millimeter wave radar.The overall scheme of aerial power line detection is proposed.The grating lobe problem in the process of antenna beam scanning is analyzed.An effective solution is given and simulated,which verifies the rationality and feasibility of the scheme.The application of Doppler effect in measuring the relative velocity between radar and power line is deduced.Aiming at the blind speed and stroboscopic problem in the process of velocity measurement,the processing methods of repetition frequency difference are given.The space random discrete points acquired by millimeter wave radar detecting power line are simulated by using MATLAB software.Aiming at dealing with the problem of three-dimensional straight line fitting which is difficult to deal with,the problem of three-dimensional straight line fitting is transformed into that of plane straight line fitting by projection method.Using the discrete points obtained by the simulation of matlab,the fitting of spatial straight line is carried out based on the least square method and the whole least square method respectively,and the fitting effect of the two methods is analyzed and compared.The results show that when the standard deviation of discrete point data is small,the two methods have the same fitting effect.With the increase of standard deviation,the fitting effect based on global least squares method is better than that based on least squares method.