Trajectory optimization for parafoil delivery system considering complicated dynamic constraints in high-order model

Trajectory optimization is essential for all unmanned aerial vehicles, especially the parafoil delivery system, as the optimized trajectory must be practical and realizable. However, with the traditional 3-degree of freedom (DOF) model used in trajectory optimization, the realizability of the optimized trajectory is largely reduced without consideration of its dynamic constraints. Moreover, the landing and tracking precision of the system will also be reduced. To solve this problem, in this paper, a novel trajectory optimization method is explored. Different from existing research, trajectory optimization is achieved with a complete 6-DOF dynamic model of the parafoil delivery system. When this is combined with the Gauss pseudospectral method, complicated dynamic constraints can be taken into account in the trajectory optimization. In addition to achieving a global optimal control objective under dynamic constraints, the proposed method also can include multiple external environment constraints, such as terrain, wind disturbance and flared landing. Finally, our results show that the proposed method can achieve all the control objectives successfully. The optimized trajectory is smooth and realizable. Compared with other trajectory optimization methods that use a 3-DOF model, the advantage of the proposed method is clear. Considering the complicated dynamic constrains of the system, it has much better realizability and is more consistent with reality.