A SMART INTERNAL VIBRATION SUPPRESSOR FOR A HELICOPTER BLADE—A FEASIBILITY STUDY

Abstract

The concept of a vibration suppression device mounted inside the rotor blade of a helicopter is evaluated. Two problems are considered. First, the possibility of reducing the vibration level by applying generic/non-specific dynamic loads is examined. An optimisation technique is used to provide the most effective parameters of the applied loads. It is shown possible to obtain a reduction in vibration level by applying dynamic loads along the part of the blade span. Next the concept of using an active “bender” type element for vibration suppression mounted inside the blade and attached to the blade main spar is studied. The bender is modelled as an elastic cantilever beam sandwiched on the longitudinal faces normal to the bending plane by layers of piezoelectric material. When an alternating voltage is applied to the piezoelectric layers, the element is excited into a bending motion, which leads to a dynamic force and moment reaction at the attachment point. The performance of such a device is studied using a computer model of a hingeless rotor blade. The bender placement and design parameters are varied in order to obtain insight into their influence on the vibration suppression. For currently practical blade and bender parameters considered it appears that excitation by the blade motion overrides the control available from the piezoelectric device, although future developments in piezoelectric material performance will improve the situation.