Multi-loop Gain-scheduling Control of Flexible Air-breathing Hypersonic Vehicle

For a flexible air-breathing hypersonic vehicle model, this paper is concerned with the application of linear control theory to address its complex control problem over wide range of flight conditions. Because of the complexity of the numerical nonlinear model of the vehicle dynamics, a curve-fitted model in closed form is created. Based on the analytical model, a linear parameter-varying (LPV) model is derived for dynamic analysis and control design. A brief dynamic analysis of the vehicle is conducted to reveal its key dynamic characteristics. Under the guidance of the open-loop analysis, a multi-loop control architecture is proposed to decompose the full control problem into three lower-order sub-problems, which are solved at different frequency band. The control design combines pitch rate loop, attitude loop, and trajectory loop as sequential feedback structure, and the rate gyro placement is also a part of the control design procedure. The resulting flight control system is scheduled with dynamic pressure and Mach number to accommodate the variations of flight conditions. The effectiveness of the control strategy is demonstrated on the full nonlinear model of the vehicle dynamics.