Distance-Fields-Over-Grids Method for Aircraft Envelope Determination

In this research, the concept of posing the flight envelope as a reachable set is explored further, and it is investigated whether the distance fields over grids (DFOG) method for reachability computations is a viable method for envelope determination. The DFOG method approximates the reachable set of a dynamic system by solving a number of optimal control problems over a grid in the state space. Then, the end points of the resulting optimal trajectories are used to provide an approximation of the reachable set. The DFOG method is improved by using a second-order Runge–Kutta method for the state discretization and developing a new adaptive grid-selection approach. This method is then applied to the computation of a four-dimensional reachable set of a nonlinear high-fidelity F-16 model. The results are compared to the results obtained with the level-set method, demonstrating that the DFOG method provides a less conservative approximation to the reachable set.