Cross range trajectory optimization of hypersonic vehicle for obstacle avoidance in level plane

The cross range trajectory optimization of the hypersonic vehicle is considered for avoiding the obstacle in level plane. The obstacle results in the noncontinuous constraint in the problem. The control parametrization method with time scaling and the constraints transformation is used to solve the optimal control problem. The purpose is to design an optimal obstacle avoidance trajectory to maximize the down range under the heating rate, dynamic pressure and overload constraints within a fixed time. Because the obstacle constraints are noncontinuous constraints, it is difficult to obtain its gradient. Based on the constraint transformation the noncontinuous constraint is changed into the canonical constraint equally. The time axis is divided into some segments with different lengths by the time scaling method. The proposed method gets the better results than that of the method with equal segments by the simulations. The performance doesn´t get longer down range greatly as the number of the segments increase.