Aircraft Loss-of-Control Recovery Using High Order Sliding Mode Control with Optimal Sliding Surfaces

Abstract

The complexity of modern commercial and military aircraft requires an advanced level of automation that would prevent the aircraft from losing controllability due to failure, or maneuverability near critical points, and also assist the pilot during the recovering process following Loss-of-Control (LOC). Here, recovery is regarded as the ability to regulate key variables to an acceptable performance during abnormal behaviors that are qualied as LOC. LOC has been among the most predominant causes of aircraft accidents over the past decade. Few research reports directly address the connection of LOC with in ight bifurcation phenomenon. In this paper we are concerned mainly with bifurcation of the equilibrium equations, ordinarily associated with stall, spin, falling leaf and others aircraft upset scenarios. Such bifurcation points are not usually associated to a particular failure of components but once the vehicle maneuvers near those irregular points, it loses its ability to regulate in ight keys outputs due to the occurrence of structurally unstable zero dynamics. Throughout this analysis, an investigation of the bifurcation point is carried out and a recovery strategy is designed using Dynamic Extension and High Order Sliding Mode Control techniques. The resulting controller would assist the pilot during post LOC to recovery to the normal ight regime where safety requirements are ensured. The Generic Transportation Model (GTM) model is uses for illustration of the recovery process.