Aplicação do Nonlinear Energy Sink (NES) no controle passivo da instabilidade em helicóptero com anisotropia

Abstract

During landing or take-off procedures, helicopters with articulated blade rotors can show an unstable response, known as ground resonance. The occurrence of this phenomenon may compromise the structural integrity of the aircraft and the crew’s safety. Physical-mathematical models were developed to map the instability zones. The isotropic model considers that all blades have the same mechanical properties, while the anisotropic model concerns different properties between blades. The last model leads to the appearance of new instability regions, as compared with the isotropic one, and it hinders the aircraft control. The addition of a nonlinear dynamical absorber, Nonlinear Energy Sink (NES), into the helicopter has demonstrated to be efficient in controlling this phenomenon. However, there is the need to answer if the NES designed for the isotropic case can also control the instabilities presented in the anisotropic system? For answering this question, the Method of Multiple Scale (MME) is used. Through this method, analytical equations representing the Slow Invariant Manifold (SIM0) and the Super Slow Invariant Manifold (SIM1) are obtained. The interaction between these curves captures the nonlinear effects from the NES on the dynamics of the anisotropic helicopter. The obtained results are validated using a numerical integration method and they could highlight the potential applicability of NES to control the helicopter instability with anisotropic rotor.