Trajectory Generation for Aircraft Avoidance Maneuvers Using Online Optimization
Rushen Patel, Paul J. Goulart · Journal of Guidance Control and Dynamics · 2010
This paper presents an aircraft trajectory generation scheme for use as a part of an autonomous counterhijack control system for civilian aircraft. In this scheme, buildings and other critical infrastructure and landmarks are modeled as constraint objects to be avoided in the aircraft flight path. A three degree-of-freedom nonlinear model and a direct multiple shooting method are employed to generate finite horizon avoidance trajectories for this system. A novel method for modeling nondifferentiable constraint obstacles (e.g., polytopes) is developed, employing dualization of the state exclusion regions to maintain continuity, thus allowing the use of a gradient-based optimization algorithm. The dualization method is further extended to construct positively invariant target sets that ensure the terminal state of each of the finite horizon trajectories generated remains feasible when extended over an infinite horizon. These conditions, when combined with a warm-start method based on shift initialization of prior solutions, ensure the optimization is initialized close to a feasible solution for the nonconvex problem. The results show, via a selection of simulation cases and for various classes of constraint objects, that the proposed strategy produces feasible avoidance trajectories with computation times viable for real-time applications.