Index approach law based sliding control for a hypersonic aircraft

A universal improved nonlinear longitudinal model of hypersonics developed by Langley lab is adopted. For the input/output (I/O) linearizing model, a sliding mode controller with index approach law as its reach method is designed. This method can solve the uncertainty problem and is insensitive to disturbance of outside interference. The simulation for tracking the height step and velocity step order at cruise conditions shows the sliding mode controller with index approach law boosts the tracking speed by more than 50 percent when compared with the controller with sign function as its reach law. In addition, the sliding controller with index approach law can eliminate steady state error which exists with the sign function method.