Abstract
The highly nonlinear and coupling characteristics of a flexible air-breathing hypersonic vehicle create great challenges to its flight control design. A unique parameter adaptive nonsingular terminal sliding mode method is proposed for longitudinal control law design of a flexible coupling air-breathing hypersonic vehicle. This method uses adaptive reaching law gain instead of the additional adaptive compensation term to handle the uncertainty to improve robustness. The stability of the close loop system is proved via a Lyapunov way. The longitudinal tracking control law for velocity and angle of attack is designed based on a rigid dynamic model of a flexible air-breathing hypersonic vehicle. A strong coupling model of the same vehicle, considering aerodynamic-scramjet engine-flight dynamic-elastic couplings, is established as the verification platform of the designed control law. The remarkable differences of flight dynamic characteristics between this strong coupling model and the rigid body model can be seen, which mean the controller needs to endure very great uncertainty, unmodeled dynamics, and other types of internal disturbance. Simulation results based on the coupling model demonstrate that the designed control law has good performance and acceptable robustness.
Highlights
A hypersonic vehicle is a kind of aircraft which can fly at more than Mach 5
The flight dynamic model considering the coupling among the aerodynamic, scramjet propulsion, and flexible dynamic is referred to as the weak coupling flexible dynamic model (WCFDM), and the flight dynamic model which includes the inertial coupling effects between the unsteady motion of air-breathing hypersonic vehicle (AHV) and the flexible dynamic is called the strong coupling flexible dynamic model (SCFDM)
Integrative design and special geometry make the flexible dynamic of the AHV strongly coupled with flight dynamic, scramjet propulsion, and aerodynamic
Summary
A hypersonic vehicle is a kind of aircraft which can fly at more than Mach 5. Xu et al [23] put forward an adaptive terminal sliding mode controller for a rigid body linearization model of AHV, in which parameters of the aircraft or aerodynamic parameters are estimated online via an adaptive law, and the desired performance is achieved under the influence of parameter uncertainties. In order to improve the control performance and robustness under the influence of external disturbance and model uncertainties, Yu et al [27] develop a continuous high-order finite-time arrival sliding mode control method based on a continuous adaptive second-order sliding mode disturbance observer. After introducing the controller design, the adaptive terminal sliding mode control method proposed in this paper will be simulated and validated based on the strong coupling flexible AHV model.
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