Tracking control of air-breathing hypersonic aircrafts in cruising flight based on sliding mode method

Due to nonlinear coupling and complex fight dynamics, the control of hypersonic aircrafts is usually challenging. In this paper, taking the longitudinal motion of a general air-breathing hypersonic aircraft as the controlled object, we designed a sliding mode controller to control velocity and altitude tracking based on input-output linearization. The velocity and altitude subsystems can be obtained by linearization and highest order derivatives of outputs in the two subsystems are designed to satisfy the sufficient and necessary condition of sliding mode control based on Lyapunov functions. A saturation function is used in the sliding mode controller to reduce chattering instead of the discontinuous sign function. Simulation is studied to validate that the controller based on sliding mode can make the aircraft system stable and meet the desired tracking performance.