A magnetorheolocial fluid elastomeric (snubber) lag damper is developed to provide adaptive lead-lag damping augmentation for a hingeless helicopter rotor. The MR fluid elastomeric (MRFE) lag damper consists of a flow valve, a flexible snubber body, and a flexible center wall separating the body into two fluid chambers. MR fluid enclosed in the snubber body can flow through the valve and be activated by a magnetic field in the valve. Consistent with the loading conditions for a helicopter lag damper, the MRFE damper is tested under single frequency (lag/rev) sinusoidal excitation. The complex modulus method was used to compare the MRFE damper damping characteristics with a baseline passive snubber type Fluidlastic® damper. The field-off damping of MRFE damper is smaller than the baseline damper. A significant controllable damping range is also observed as current was applied to a magnetic valve in the MRFE damper. Furthermore, the non-linear behavior of the MRFE damper is not sufficiently modeled using the complex modulus method. Thus, to account for the hysteresis behavior of the MRFE damper and estimate the damping force, a hydro-mechanical model is formulated based on lumped parameters. Parameters for the model are established using experimental data and a least-mean-square error minimization technique. The model is then applied to reconstruct the force time history under lag/rev excitation frequency. The average error between the predicted and measured damping forces is also evaluated to assess model accuracy.
- Aerospace Division
A Semi-Active Magnetorheological Fluid Snubber Lag Damper for a Hingeless/Bearingless Helicopter
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Ngatu, GT, Hu, W, Kothera, CS, & Wereley, NM. "A Semi-Active Magnetorheological Fluid Snubber Lag Damper for a Hingeless/Bearingless Helicopter." Proceedings of the ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. Smart Materials, Adaptive Structures and Intelligent Systems, Volume 1. Ellicott City, Maryland, USA. October 28–30, 2008. pp. 749-761. ASME. https://doi.org/10.1115/SMASIS2008-494
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