Abstract:

A segmented trajectory optimization strategy based on the Gauss pseudospectral method (GPM) is proposed for hypersonic vehicles during reentry where some monitoring and no-fly zones are inevitably encountered. The segmentation of the trajectory converts the original optimal control problem of the trajectory optimization into the multi-segment optimal control problem. With the help of GPM, each segment trajectory is planned according to the standard computing procedure of GPM. The whole trajectory thus obtained can make the vehicle smoothly enter into the monitoring zones, successfully circumvent the no-fly areas, and finally reach the predetermined point. Besides, considering the requirements of the high computing efficiency and the engineering practicability, we put forward a weighted performance index of reentry time and path-and-heading-angle related variables. The proposed performance index and corresponding optimization strategies definitely provide us the rapidity of the path planning, the smoothness of the flight trajectory, the flatness of the controlled variables, and the improvement of the computational efficiency. The simulation results show that the piecewise optimization scheme proposed in this paper can quickly plan a reentry trajectory for a hypersonic vehicle with complex constraints.

Key words:  Hypersonic vehicle, Segmented trajectory optimization, Monitoring zone, No-fly area, Gauss pseudospectral method