Control Evaluations of Semiactive Fluid-Elastomeric Helicopter Lag Damper

摘要

A semiactive magnetorheological fluid–elastomeric device has been assembled and evaluated in controlrnexperiments to demonstrate its utility to compensate formeasured changes as a helicopter lag damper. The baselinernused in this study was lag damper (snubber) for a hingeless helicopter rotor that employs both elastomers and fluids:rnthat is, a fluid–elastomeric damper. This damper was disassembled and modified to include two internalrnmagnetorheological control valves, and the existing hydraulic fluid was replaced with magnetorheological fluid.rnHence, the resulting prototype damper is a retrofit design that can easily be installed in a test rotor in futurernevaluations. The magnetorheological fluid–elastomeric damper was subject to extensive performance char-rnacterization at displacement amplitudes ranging from 0.8 to 3.4 mm, temperatures ranging from 20 to 55u0001rnC, andrncontrol currents up to 2.0 A. Using this database and a hydromechanicalmodel of the damper, control systems wererndesigned to track a reference damping profile, which is a function of amplitude only, in the presence of measuredrnamplitude and temperature variations at the rotor lag frequency (3.8 Hz). Both open-loop (interpolating lookuprntable) and closed-loop (proportional-integral and gain scheduling) techniques were employed in simulations andrnexperiments. The results demonstrated that all of the control schemes were effective, although a minimum trackingrnerror was achieved with the closed-loop systems. Comparing the two closed-loop systems, the gain-schedulingrncontroller provided a faster response overall, but the improvement was marginal.