Nonlinear control of flexible hypersonic vehicles with canard

For a hypersonic vehicle with unstable longitudinal dynamics, non-minimum phase and severe aeroelastic effects, the design of flight control system is a challenging task. The feasibility of the strategy using canard in conjunction with the elevator as an additional factor is investigated, aiming to eliminating the non-minimum phase behavior and suppress the elastic mode, and to improve the performance of control system. First, a flight dynamic model with flexibility effects is presented. Second, the effects of the placement and relative ganging gain of the canard on the non-minimum phase behavior and elastic modes are demonstrated. At last, with the design of a nonlinear controller based on feedback linearization and LQR technology, the performances of the strategies with and without canards are comparatively evaluated. The simulated results show that, with the placement and relative ganging gain carefully chosen, the proposed control strategy provides an increased level of closed loop performance by suppressing the non-minimum phase behavior and eliminating control excitation of the first elastic mode.