Nandan Kumar Sinha

In this paper, we present a variable structure based sliding mode controller for recovery of an aircraft from spin. The spin recovery problem is formulated as a two point boundary value problem where the two points, different steady states of the aircraft, are obtained from a bifurcation analysis of the aircraft model. Using the bifurcation analysis results of the aircraft, the spin states of aircraft are identified. Once the aircraft enters into spin, the controller is activated to bring it back to a desired state which is a level flight trim solution also found from a bifurcation map of the aircraft model.

In this paper, two controllers are presented for commanded departure of an aircraft into spin. The first controller is designed based on the information obtained from the bifurcation analysis results of the aircraft model and trial and error simulation experiments. The second controller is a nonlinear sliding mode controller also designed using bifurcation analysis results of the aircraft as reference maps. The sliding mode controller design problem is formulated as a trajectory tracking problem, where, the reference trajectory to be tracked is defined by spin simulation. Initial conditions are level-flight trim states, computed using extended bifurcation analysis and final states are stable, steady and flat oscillatory spin states. © 2012 Elsevier Masson SAS. All rights reserved.