The feasibility of applying magnetorheological (MR) lag dampers to the mitigation of ground resonance instabilities and to control the damping level ofrotor lag modes was assessed. The biviscous MR damper model was motivated by the extensive and ongoing program of design, and testing of MR dampers at University of Maryland. The following conclusions were made in this study: 1) It is feasible to stabilize an unstable rotor using MR dampers. In the initial feasibility study it was showed that for a damper attachment point separation of 1.5 ft, the yield force of the MR damper is, Fy = 3158 lb, indicating that the size and force level of MR dampers are in a proper and feasible range to stabilize the ground resonance of the rotor system. 2) The stability of the rotor system is influenced only by the nondimensional yield force Fy of the biviscous MR dampers. The biviscous damping ratio of Cpo/Cpr has little effect on the stability. Therefore, the yield force controlled by applied magnetic field is the key control variable in MR dampers to mitigate ground resonance instability. 3) The study showed that using MR dampers and a semi-active controller can stabilize an unstable rotor. The feedback linearization control strategy can be used to maintain the design stability margin in the system. The sliding mode control, even though a stability diagram could not be computed, provides comparable results in the time domain to feedback linearization control. 4) The robustness study showed that the MR dampers, actuated with a properly designed controller can recover stability when the rotor system loses stability due to damper degradation in most cases. The method failed only when 100 % damping is lost on one blade. From the stand point of robustness to damper degradation, having two MR dampers per blade is better than having one damper per blade, because two MR dampers per blade afford the opportunity to nearly recover the stability margins of the undamaged system when a single damper is lost. Overall, MR dampers offer an opportunity to enhance stability augmentation strategies over passive elastomeric dampers, and should be considered in advanced rotor design.
Semi-active damping of ground resonance in helicopters using magnetorheological dampers
Halbaktive Dämpfung der Grundresonanz in Hubschraubern mittels magnetorheologischen Dämpfern
Journal of the American Helicopter Society ; 49 , 4 ; 468-482
2004
15 Seiten, 20 Bilder, 3 Tabellen, 26 Quellen
Aufsatz (Zeitschrift)
Englisch
SEMI-ACTIVE DAMPING OF GROUND RESONANCE IN HELICOPTERS USING MAGNETORHEOLOGICAL DAMPERS
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