Aircraft Stall Recovery using Sliding-Mode Based Pitch-Attitude and Altitude Control

This paper presents the control law design for transferring the aircraft from stall flight to steady-straight-level flight using a sliding-mode based pitch attitude and altitude control. The exponential convergence of errors is discussed by invoking Barbalat's Lemma theorem. Thereafter, settling time expression, for commanded variables, to reach the sliding surface is obtained. Finite-time stability to reach sliding manifold is also proved. In the proposed control strategy, control inputs viz., elevator and throttle are obtained in a closed-loop form. The results of this research indicate the proposed controller first stops the aircraft pitching motion by controlling the aircraft pitch angle then reaches the commanded altitude to attain constant-altitude-level flight.