Research On Active Control Technology Of Near Space Morphing Vehicle

Research on the near space morphing vehicle poses several challenges due to its multi-mission profiles, large attitude maneuvers and complicated flight conditions. Due to the sharply backward movement of the aerodynamic center in hypersonic flight, on one hand, the lift of the vehicle is reduced; on the other hand, the stability margin increases largely while the maneuverability decreases. The object in this paper is a horizontal taking-off near space vehicle. Owing to the high sweep angle and the slender structure, much less taking-off lift is produced by the vehicle compared with general aircrafts. Active control technology is proposed in this paper to solve the problems above. The main contents of this paper include:(1) Relaxed static stability(RSS) is proposed in this paper to increase the lift coefficient as well as to improve the maneuverability in hypersonic flight, and the numerical value of RSS is obtained on the premise of good maneuverability. The engineering realization methods are given at the same time.(2) The vehicle is quantitatively designed to be statically unstable in subsonic flight with RSS. Consequently, a stability augmentation system(SAS) is needed to ensure the stability in subsonic flight. Simulation studies are conducted comparing the linear SAS to the nonlinear SAS. Simulation results show that the nonlinear dynamic-inversion controller synthesized with PID controller robustly stabilizes the near space morphing vehicle.(3) The intelligence-nonlinear control scheme via backstepping method is proposed to solve the problems of stable tracking control of the vehicle in hypersonic flight considering compound disturbances. RBF is added to restrain unknown disturbances, and the dynamic surface control strategy is employed to eliminate the explosion terms. Simulation shows the controller has good dynamic responses and robustness with great disturbances.(4) At last, this paper introduces the direct force technology into the taking-off stage of hypersonic vehicle, and discussing the effect of direct force technology on taking-off performance. The simulation results indicate that the direct force technology obviously improves the taking-off performance of the vehicle and effectively solves the problem of lacking lift.