Automatic landing system design using sliding mode control

This paper presents the application of sliding mode control technique for the design of a nonlinear aircraft controller to execute autonomous landing maneuvers. Complete aircraft landing maneuver is divided into two phases: glide-path capture and flare maneuver. Flight-path is specified for these two phases in the longitudinal landing plane as a straight line and an exponential curved profiles, along which the aircraft has to descend. This specified flight-path is treated as a reference trajectory to be tracked. Errors in spatial position with respect to the reference flight-path are transcribed into desired state variables. Sliding functions are then formulated in terms of the error dynamics of these state variables with the reference flight-path as the solution. Using Lyapunov stability criteria, a control law is derived to force the sliding functions to reach the solution and converge the aircraftÊ 1/4 s path to the reference trajectory. The controller obtained is validated by simulating the landing maneuver using a nonlinear aircraft model with a large offset in initial position from the nominal landing trajectory. The merits of the proposed controller are demonstrated by comparing the results with the ones achieved using the conventional proportional-integral-derivative controller. It is shown that the sliding mode controller yields successful tracking results, quick alignment with the reference glide-path, and smooth execution of the flare maneuver. © 2013 Elsevier Masson SAS.All rights reserved.