Abstract
Considering the hypersonic aerospace vehicle, with high dynamic, strong varying parameters, strong nonlinear, strong coupling, and the complicated flight environment, conventional flight control methods based on linear system may become invalid. To the high precision and reliable control problem of this vehicle, nonlinear flight control strategy based on neural network robust adaptive dynamic inversion is proposed. Firstly, considering the nonlinear characteristics of aerodynamic coefficients varying with Mach numbers, attack angle, and sideslip angle, the complete nonlinear 6-DOF model of RBV is established. Secondly, based on the time-scale separation, using the nonlinear dynamic inversion control strategy achieves the pseudolinear decoupling of RBV. And then, using the neural network with single hidden layer approximates the dynamic inversion error for system model uncertainty. Next, the external disturbance and network approximating error are suppressed by robust adaptive control. Finally, using Lyapunov’s theory proves that all error signals of closed loop system are uniformly bounded finally under this control strategy. Nonlinear simulation verifies the feasibility and validity of this control strategy to the RBV control system.
Highlights
To meet the development of space research, space tourism, and military requirement and achieve the goal of speediness, high reliability, reusability, and low cost, the hypersonic aerospace vehicle especially reusable launch vehicle, RLV, emerges [1,2,3,4,5,6].Reusable boosted vehicle (RBV) experiences the subsonic, transonic, and supersonic phase during the whole flight, which the aerodynamic coefficients, dynamic pressure, and flight altitude acute change, especially in the large attitude adjusting phase with supersonic and large angle of attack
This paper focuses on the large attitude adjusting phase after the RBV separating between the core stages
In order to design the flight control system of RBV in this paper conveniently, aerodynamic data models of RBV are built in the velocity coordinate system, and body coordinate system respectively [25]
Summary
To meet the development of space research, space tourism, and military requirement and achieve the goal of speediness, high reliability, reusability, and low cost, the hypersonic aerospace vehicle especially reusable launch vehicle, RLV, emerges [1,2,3,4,5,6]. Considering the imprecise aerodynamic model, abominable flight condition at the high altitude, great system perturbation, and interference, gain scheduling and PID control strategy based on linearized with small disturbances cannot apply to the flight control system of RBV large attitude adjusting phase design. It is necessary to design RBV control system by using nonlinear control method. Shtessel designed the sliding mode control system of X-33 based on the time-scale separation principle, which has achieved the great control performance [7,8,9]. Using the above method designed the control law of the large angle of attack aircraft. Be pointed out that modeling error and serious unusual aerodynamic effect cause the decreased robustness in the NDI control law. NDI control methodology requires the accurate model. It is necessary to combine the other control methods to eliminate the influence of inaccurate model
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