Tracking Control of Hypersonic Vehicles with Input Saturation Based on Fast Terminal Sliding Mode

In this paper, the track problem of hypersonic vehicle is studied and analyzed with external disturbances, parameter uncertainty and input saturation. First, to make the design of controller convenient, the input and output linearized high-order model of hypersonic vehicle is transformed into a multi-variable second-order system model by introducing auxiliary error variables. To ensure the sliding mode manifold is practical finite time stable, an adaptive fast nonsingular terminal sliding mode controller is designed for hypersonic vehicle with unknown upper bound of disturbance. An adaptive anti-saturation fast nonsingular terminal sliding mode controller is designed by introducing hyperbolic tangent function an auxiliary system, which further solves the input saturation problem. Not only the requirement for actuator physical restraint is satisfied, but also the finite time stability of system sliding mode manifold is guaranteed at the same time. The vigorous proof is given using Lyapunov theory for the designed controllers. The numerical simulations are also conducted with the longitudinal nonlinear dynamic mode of hypersonic vehicle. The results demonstrate the effectiveness of the two designed controllers.