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Near-optimal control of altitude and path angle during aerospace plane ascent

par Kremer, Jean-Paul ;Mease, Kenneth K.D.
Référence Journal of guidance, control, and dynamics, 20, 4, page (789-796)
Publication Publié, 1997-07

Article révisé par les pairs

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Résumé :

Altitude and flight-path-angle control during the posttransonic airbreathing segment of aerospace plane ascent is addressed, with objectives to minimize fuel usage and respect the vehicle flight envelope. Based on a time-scale separation between energy/mass and altitude/path-angle dynamics, the altitude/path-angle control problem is viewed in a singular perturbation framework as an initial boundary-layer problem. A feedback law approximating the minimum-fuel initial boundary-layer control is obtained by solving a neighboring-optimal problem. To facilitate this derivation, the state constraint that is active on the slow solution is modeled in the boundary layer using an appropriate penalty function. The neighboring-optimal feedback law performs well as long as temporary constraint violations are acceptable in the boundary layer. An alternate linear feedback law is derived with gains calculated to reduce constraint violations, but this law leads to increased fuel usage. Numerical results are presented for a lifting-body configuration of an aerospace plane and a Mach 8 flight condition. The results show that fuel usage and control activity are reduced when the peak dynamic pressure is allowed to increase. Differences in fuel usage are small for the vehicle model employed.