Nonlinear control law for hypersonic vehicle with nonlinear disturbance observer

Hypersonic vehicle's nonlinear dynamics system is highly nonlinear,multivariable coupled and includes uncertain parameters.Particularly for this problem,a new backstepping sliding mode controller is designed based on nonlinear disturbance observer(NDO) and backstepping sliding mode control scheme.NDO is used to observe the disturbance of the system and the limitation of the disturbance can be unknown.Sliding mode control is adopted in every backstepping design to compensate for unknown disturbance.The approach prevents cumulative error and realizes robust output tracking to guide order.The system is proved to be stable.Simulation results show this method can observe the disturbance ideally and enhance the robust performance of system.