Optimal path planning for unmanned aircraft target observation through constrained urban environments

Abstract

The work herein determines the optimal flight path for a small unmanned aircraft system through a constrained urban environment. The implementation of unavoidable keep-out regions is evaluated by first solving the optimal flight path through a constrained simplex corridor and, second, minimizing incursions to keep-out regions given the same constraint field and ending on a defined orbit around a target of interest. Direct orthogonal collocation methods are combined with fast geometric path planning techniques where a triangulated mesh is used to produce a hybrid control routine, resulting in optimal flight paths through a defined triangulated corridor. Physical constraints are eliminated from the nonlinear program search space, while keep-out regions are modeled within the objective function of the optimal control problem and avoided according to a weighted distribution of the objective components. A scenario is presented for a small unmanned aircraft system to advance at constant altitude and constant speed through city building constraints while minimizing time in unavoidable keep-out regions. The path terminates outside the triangulated corridor on an orbit, encircling the target location. Results illustrate an optimal path solution through 37 polygonal constraints and 2 nonlinear, unavoidable keep-out regions with computational times on the order of 90 s.