Tau Guidance in Boundary-Avoidance Tracking - New Perspectives on Pilot-Induced Oscillations

Abstract

DOI: 10.2514/1.54065 Tau theory, introduced to the flight control discipline as a model for natural guidance, is shown to provide an approach to predicting a class of adverse aircraft-pilot couplings described as boundary-avoidance tracking events and pilot-induced oscillations. These have previously been modeled a posterior as discrete events using timedependent feedback gains. Drawing on the prospective nature of the time-to-contact variable optical tau � , a new method is proposed for modeling such phenomenon and also for determining the critical incipience for this class of aircraft-pilotcoupling.Inthepresentstudy,theapproachhasbeenappliedtotauguidanceinarotorcrafttrajectory tracking maneuver, to predict the conditions under which aircraft-pilot couplings may occur. In addition, a strong correlation between motion and control activity and the derivatives of tau adds substance to the hypothesis that the pilot’sperceptualsystemworksdirectlywithinvariantsintheoptical flowduringvisualguidance.Resultsfrom flight simulation tests conducted at the University of Liverpool and complementary flight tests carried out with the National Research Council (Canada) advanced systems research aircraft in-flight simulator support the tau control hypothesis. The theory suggests ways that pilots could be alerted to the impending threat of such adverse aircraftpilot couplings.