Reentry trajectory optimization of hypersonic vehicle with enhancing parametrization method

The paper considers the reentry trajectory optimization of the hypersonic vehicle as an optimal control problem. The purpose is to design the optimal control law to ensure that the hypersonic vehicle maximizes the downrange under the heating rate, dynamic pressure and overload constraints. It is formulated as a constrained optimal control problem, where specific requirements of this reentry trajectory optimization are all incorporated in the problem formulation. Traditional methods for solving the optimal control problems is to solve the necessary conditions by applying the Pontryagin minimum principle, which is difficult for solving the Two Points Boundary Value Problem. In this paper, the problem is transformed into an equivalent standard optimal control problem subject to continuous state inequality constraints. A computational method is developed based on the control parametrization in conjunction with a time scaling transform and the constraints transcription method. Finally, the two parametrization methods are compared and the result of the proposed method is better than that of the conventional parametrization one.