Comparison of Two Methods Used to Deal with Saturation of Multiple, Redundant Aircraft Control Effectors

Abstract

A comparison of two methods to deal with allocating controls for unattainable moments in an aircraft was performed using a testbed airframe that resembled an F/A-18 with a large control effector suite. The method of preserving the desired moment direction to deal with unattainable moments is currently used in a specific control allocator. A new method of prioritizing the pitch axis is compared to the moment-direction preservation. Realtime piloted simulations are completed to evaluate the characteristics and performance of these methods.A direct comparison between the method of preserving the moment direction by scaling the control solution vector and prioritizing the pitching moment axis is performed for a specific case. Representative maneuvers are flown with a highly unstable airframe to evaluate the ability to achieve the specific task. Flight performance and pilot interpretation are used to evaluate the two methods.Pilot comments and performance results favored the method of pitch-axis prioritization. This method provided favorable flight characteristics compared to the alternative method of preserving the moment direction for the specific tasks detailed in this paper. AcknowledgmentsI would like to thank first and foremost my parents for their support and unending advice that have helped me to make the most of myself and live my life to the fullest. To my sister Julie and my brother Daniel with whom I have the fortune of knowing. Julie's pursuit to make the most of life in the face of constant hurdles, and Dan's quest to never be in the shadow of older siblings has made our relationships both exhaustive and rewarding.I would like to thank my advisor Dr. Wayne Durham for his persistence and patience with me and my academic career. He has given me the perfect work environment and has constantly pushed me, with much resistance, to achieve all that I could. To the remaining members of my commitee, Dr. Fred Lutze and Dr. Chris Hall, thank you for making my education at Virginia Tech a wonderful experience and for sharing everyday life experiences with me.