Risk Assessment And Path Planning For Unmanned Aerial Vehicle Operations In Urban Environments

With the development of Unmanned Aerial Vehicle(UAV)industries,the demand for UAV operations has been fast growing in recent years.Increasing use of UAV in urban environments brings safety issues,as UAV may fail to operate resulting in human fatality risk or infrastructure property damage risk in urban environments.Risk management of UAV flights for safe operations is therefore critical.This thesis studies risk modeling and assessment problems for UAV safe operations in urban environments.Three main risk types are considered: UAV impacts people on the ground,UAV impacts ground vehicles,and UAV collides with commercial manned aircraft in the vicinity of airport.We establish risk assessment models to quantify the costs of each risk and then generate a risk cost map.Selected urban areas are meshed and the risk cost of each cell is computed and presented in the map.Based on that,UAV cost-effective path planning methods are studied with the proposed concept of risk awareness and avoiding.Characteristics of different kinds of algorithms are analyzed and then ant colony optimization(ACO)algorithm and rapid-exploring random tree(RRT)algorithm are chosen as basic path planning algorithms to produce the UAV cost-effective paths.Based on the two original algorithms’ strengths and weaknesses,four algorithms are designed and improved to solve various path planning problems.According to the proposed operation environment model,flight rules,and various demands of path planning,several urban UAV path planning models are established respectively.The feasibility and effectiveness of the proposed risk assessment models,path planning models,and improved algorithms are validated by simulation studies.This research is conducive to reducing operational risks in urban environments posed by UAV operations and enhancing the efficiency and utility rate of urban airspace.By conducting the risk assessment,this research is useful to provide risk information for UAV safety risk management.Moreover,the proposed path planning method enables more efficient and organized UAV traffic flows under complex risk environments,which can further act as the theoretic foundation for designing route network in urban low-altitude airspace for future highdensity UAV operations.