Composite control design with sliding mode for a hypersonic aircraft

A composite control treatment based on sliding mode is presented to a hypersonic nonlinear longitudinal dynamics. The aircraft model is developed with a unique integrated airframe-propulsion configuration which arise couplings between propulsion and aerodynamics and it is also a non-minimum phase systems with zero-dynamics. All of these result in intractable nonlinear system for control design. In this paper starting from lookup table data, a control-oriented model is obtained by high-fidelity curve fitting. The proposed controller consists of two close loops: the inner one tracks angle of attack command and maintains attitude stability; the outer one applies sliding mode control to achieve altitude and velocity tracking by taking the inner loop as unmodeled dynamics. Simulation is taken at the cruise condition with 30km and 6Ma. The results render supporting evidence that the two loops composite controller can track given trajectory accurately while maintaining altitude stable. Compared with single loop controller design method, the performance has been improved remarkably.