Variable structure control for aircraft in wind shear field

This paper examines the application of variable structure control theory to the design of a flight path control system for an aircraft landing in an unknown wind shear field. The objective in variable structure design is to confine the state trajectories to a subspace of the total state space. The motion in the subspace is insensitive to system parameter variations and external wind shear disturbance that lie within the space limits of the control. A switching type of control law is naturally obtained during the design procedure. The design process consists of three parts. First, the windshear and the system perturbation are taken as uncertain factors and the uncertain system model is presented. Then the invariance conditions for an aircraft with respect to the wind shear disturbance and the system parameter variations are derived. Finally the sliding hypersurface of the variable structure control system and the flight path control laws are designed. This control technique is feasible and efficient when applied to simulation calculations of CITATION II aircraft penetrating a wind shear field to land.