Research On Improving The Target Localization Accuracy Of Airborne Optoelectronic Platform

In modern warfare,the role of real-time information is critical.For example,in several local wars in recent years,a variety of aviation and aerospace platforms have provided guidance for the US military's precision strikes.As an effective supplement to the space-based platform such as satellites,the Unmanned Aerial Vehicles(UAV)effectively solves the problem of poor real-time reconnaissance of the space-based reconnaissance,and can provide accurate real-time information of the target,which plays a key role in the battle.At present,in the application of UAV,auxiliary functions such as enemy reconnaissance and target localization are still the main application.Accurate target localization in real time is one of its core missions.The airborne optoelectronic platform is an important task payload for UAV.It integrates various high-precision sensors and plays an important role in aerial imaging,reconnaissance and measurement.It is also one of the main sub-systems for achieving target localization.Due to the complex aero environment,the target measurement and localization process of the aviation platform is susceptible to factors such as carrier vibration,attitude angle variation,electromagnetic interference and atmospheric disturbance.It is very difficult to achieve accurate target localization.Therefore,in order to reduce the localization error,it is necessary to explore the factors affecting the accuracy,and study the corresponding improvement method or propose a new and more suitable airborne target localization method,which is a very important direction in the field of aerospace imaging and measurement technology.In order to improve the target localization accuracy of the airborne optoelectronic platform,this paper first analyzes the development status of the aviation optoelectronic measurement technology through systematic research,and summarizes the main sections of the current target localization process in aviation reconnaissance and the extent of influence of its accuracy on the localization error.The existing methods are summarized and the coordinate transformation model in the localization process is established.According to this model,the synthetic pointing angle accuracy of the target relative to the geographic coordinate system has a great influence on the final result,which provides theoretical guidance for how to improve the accuracy in engineering applications.Based on further investigation and research,it was found that in the existing general coordinate transformation process,most of the research work pays insufficient attention to the alignment error angle between the photoelectric platform coordinate system and the carrier coordinate system.The essence of the error is due to the dynamic relative angular displacement caused by the flexible connection of the photoelectric platform and the aircraft through the vibration damper.The dynamic change of the angle causes the localization accuracy to have certain uncertainty.In this paper,a method based on image matching is proposed to dynamically measure the relative displacement between the photoelectric platform and the carrier,and then convert it into angular displacement,which realizes the perfection and refinement of the traditional target localization model,which can effectively improve the accuracy.At present,the research on the traditional localization method is relatively mature.If the accuracy of the measured value in the localization process is improved to achieve the effect of improving the localization accuracy,the cost of the system is bound to be greatly improved.Therefore,to study a new localization model,under the premise of controlling cost and volume,it is imperative to evade the requirements of measurement accuracy.The traditional localization model is a one-way conversion process,and the error will gradually accumulate,which will have a greater impact on the final result.Therefore,this paper adopts distance as conditions in the localization process,whose current accuracy has reached a higher level,using a new localization model and calculation method to achieve the purpose of improving localization accuracy.The method firstly uses the traditional method to delimit a target position range according to the traditional method and its error magnitude,and then uses the distance value as a constraint condition.Combined with the published digital elevation model(DEM)information,the possible position distribution of the target can be constrained near the arc.Finally,using the data measured by the carrier at its own any two positions,the more precise position of the target can be determined by the intersection of the arcs.The traditional single-point localization method mainly has two problems: on the one hand,the accuracy of the parameter is not satisfactory,thus the localization accuracy is limited;on the other hand,the range of the target localization is limited by the range of the rangefinder,and the remote high-precision localization cannot be performed.In the field of national defense,the accuracy of target localization is expected to be high,and the airborne platform is required to achieve lighter and smaller.Therefore,it is an important research direction to study a localization method that does not depend on measurement accuracy and can cancel the rangefinder.This paper introduces the idea that the target pointing angle is combined with the image acquired by the satellite or other reconnaissance system,and proposes a feasible method to automatically match the image with database to complete the target localization.Firstly,according to the position of the carrier and the orientation of the airborne platform,the spatial equation of the visual axis is determined,and a more conservative target possible distribution area is obtained according to the error range;then,the reconnaissance image is corrected,mosaicked and the like,In order to accommodate more ground features,improve the success rate of registration;then calculate the ground coverage of the image according to the focal length,height and other information,and pick the appropriate reconnaissance image;finally,register the database images with the reconnaissance image.Select the database image with the highest matching extent to complete the localization.The image matching method adopted,based on the structural features,can get rid of the type limitation of the imaging system,for example,matching the infrared reconnaissance image with the digital satellite map in the visible light band.This method based on map database matching not only significantly improves the localization accuracy compared with the traditional coordinate conversion method,but also does not rely on the laser rangefinder,which greatly promotes the miniaturization of the airborne platform.In summary,based on the actual design and experience of the airborne optoelectronic platform in the project and the existing localization method,a method to improve the accuracy of the existing coordinate transformation localization model,a distance constraint feedback localization method and a localization method based on map matching are proposed.These methods can effectively improve the target localization accuracy,and can be combined for different application,which is of great significance for the development of airborne photoelectric measurement.