Research On Sense And Avoid Approaches Based On Stereo Visual For Small Unmanned Aerial Vehicle

The Unmanned Aerial Vehicle(UAV)has been the research hotspots at home and abroad.As the wide used of the UAV,it has been made more the autonomous flight safety demand.The Sense and Avoid(SAA)is the technology that the UAV embed into the airspace,ensure the UAV fly safety precondition.Because of the limitation of load,task,cost etc.the light and small UAV cannot take the large sense equipment like radar etc.Because of the advantage of the quality,power consumption and cost,the Vision based SAA system is easy to embed into the UAV.Also it can be wide used.In this paper,we study the visual SAA system of small UAV.Considering the monocular vision can only get the two-dimensional planar motion information of the target.In this paper,we adopt the stereo vision based SAA technology to realize the target accurate perception,reliable threat assessment and obstacle avoidance.It overcomes the shortcomings of the monocular vision,which is difficult to obtain the depth information of the target.The main research work of this paper is as follows:1)From the system program,policy standards,technical research and other aspects of the analysis the Sense and Avoid technology.The System comprehensive analysis of the history of the SAA development of technology and SAA technology research history.Also,the significance of UAV SAA and the research situation of UAV SAA technology are analyzed.The hierarchical decomposition and Technology Decomposition method of UAV is analyzed,and the SAA method is analyzed.According to the 100 years development history of SAA technology and the research status of SAA,the next step of the development of SAA technology is proposed and the key technology of SAA in the future is analyzed.2)Based on the characteristics and capabilities of the application of light and small UAV,the low power SAA system was Analyzed and built.In view of the low load and low flight speed of the small UAV system,and from the aspects of environmental data perception,airborne data processing,obstacle avoidance control and so on,and so on,the design of the hardware system is carried out.In view of the ability of perception and avoidance system,the modeling and calibration of the stereo vision sensing system are carried out.3)In view of the complex and changeable characteristics of low altitude,the algorithm of multi pattern UAV’s perception and avoidance is designed.In view of the different flight environment of UAV,the UAV in different airspace environment,the different environment for the corresponding was modeled.In low altitude environment,the obstacle detection is carried out by means of UV parallax method,which is behind the reconstruction of the 3D environment.In the high altitude environment,the background is relatively simple,and the spatial obstacles are mostly small,and little feature points.At last Background segmentation and small target detection algorithm are used to detect obstacles and the obstacles are detected by triangulation.The threat assessment of moving objects is carried out by using the safety envelope method.According to the results of the threat assessment,the obstacle avoidance is carried out by the method of target avoidance.The experimental results show that the perception and avoidance system based on stereo vision can realize the obstacle avoidance in different airspace environment,and it can also ensure the flight safety of UAV.