Suppression of ground resonance in rotorcraft using active landing gear. (March 2022)

• Record Type: Journal Article
• Authors: Krishnan, Arjun; Krishnan, Ashwin; Costello, Mark
• Is Part Of: Proceedings of the Institution of Mechanical Engineers. Volume 236:Number 4(2022)
• Page Start: 789
• Page End: 801
• Publication Date: 2022-03
• Subjects: Ground resonance -- active landing gear -- optimal control -- rotorcraft -- dynamics; Aeronautics -- Periodicals; Astronautics -- Periodicals; Airplanes -- Design and construction -- Periodicals; Aerospace industries -- Periodicals; 629.1
• DOI: 10.1177/09544100211023008
• Languages: English
• ISSNs: 0954-4100

Abstract

This article examines the fundamental aspects of controlling ground resonance in rotorcraft equipped with actively controlled landing gear. Ground resonance is a mechanical instability affecting rotorcraft on the ground. It occurs at certain rotor speeds, where the lead–lag motion of the rotor couples with the motion of fuselage creating a self-excited oscillation. Typically, passive or semi-active lag dampers are used to avoid instability; however, these are undesirable from a design and maintenance perspective. Innovations in active landing gear for rotorcraft, such as articulated robotic legs, have provided an alternate approach to avoid the instability, eliminating the need for lag dampers with respect to ground resonance. This article extends classic ground resonance to include movable landing gear and identifies key physical parameters affecting dynamic behavior. Applying LQ optimal control to this model, it is shown that ground resonance instability can be eliminated using active landing gear as the control mechanism, even when there is no lag damping present in the rotor. In addition, while superior performance is achieved when landing gear movement can occur both longitudinally and laterally, it is still possible to stabilize ground resonance with inputs in a single direction, albeit with reduced performance.