Optimal trajectory planning for small-scale unmanned helicopter obstacle avoidance

Obstacle avoidance for unmanned helicopter safely flying in complex-low environments was investigated. A solving strategy based on nonlinear optimal control theory was developed. The computation of optimal obstacle avoiding maneuvers was viewed as an optimal control problem, where the solution minimized the maneuvering duration subjected to the 6-freedom nonlinear dynamics equations and limitations of helicopter flight performance, in which the obstacles in 3D space were formulated as inequality constraints by using 1-norms. Gauss pseudospectral method (GPM) was employed to transform the trajectory planning problem to non-linear programming(NLP) problem, which can be solved using a sequential quadratic programming algorithm. Moreover the influence of obstacles sizes to the planned trajectory was investigated. Simulation results show that the proposed method can generate feasible trajectories with high accuracy, and the optimal maneuver depends on the ratio of obstacle height and weight.