Abstract
This paper deals with a novel procedure to generate optimum flight paths for multiple unmanned aircraft in the presence of obstacles and/or no-fly zones. A real-time collision avoidance algorithm solving the optimization problem as a minimum cost piecewise linear path search within the so-called Essential Visibility Graph (EVG) is first developed. Then, a re-planning procedure updating the EVG over a selected prediction time interval is proposed, accounting for the presence of multiple flying vehicles or movable obstacles. The use of Dubins curves allows obtaining smooth paths, compliant with flight mechanics constraints. In view of possible future applications in hybrid scenarios where both manned and unmanned aircraft share the airspace, visual flight rules compliant with International Civil Aviation Organization (ICAO) Annex II Right of Way were implemented. An extensive campaign of numerical simulations was carried out to test the effectiveness of the proposed technique by setting different operational scenarios of increasing complexity. Results show that the algorithm is always able to identify trajectories compliant with ICAO rules for avoiding collisions and assuring a minimum safety distance as well. Furthermore, the low computational burden suggests that the proposed procedure can be considered a promising approach for real-time applications.
Highlights
In the last few years, improvements in technology have led to an increasing use of unmanned aerial vehicles, especially for the reduction of costs and human risks they can assure
The proposed collision avoidance algorithm consists of a path re-planning procedure based on the Essential Visibility Graph (EVG) and Dubins’ paths, to avoid UAVs that are on a collision course
To avoid ambiguity, the EVG is cut according to the Right of Way rules prescribed in the Annex II of International Civil Aviation Organization (ICAO)
Summary
In the last few years, improvements in technology have led to an increasing use of unmanned aerial vehicles, especially for the reduction of costs and human risks they can assure. The article is organized as follows: In Section 2, the geometrical approach based on Dubins’ car is recalled, aimed at providing smooth trajectories compliant with the aircraft minimum turn radius constraint; in Section 3, a graph based approach based on the Essential Visibility Graph (EVG) is presented, with the proof of the optimality of the resulting path.
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