Nonlinear Analysis and Bifurcation Characteristics of Whirl Flutter in Unmanned Aerial Systems

Aerial drones have improved significantly over the recent decades with stronger and smaller motors, more powerful propellers, overall optimization of systems. These improvements consequently increased top speeds a variety performance aspects, along introducing new structural challenges, such as whirl flutter. Whirl flutter is an aeroelastic instability that can be affected by or aerodynamic nonlinearities. This may affect prediction potentially dangerous behaviors. In this work, nonlinear reduced-order model for nacelle-rotor system, considering quasi-steady aerodynamics, implemented. First, parametric study linear system performed to determine main characteristics onset instability. Multiple polynomial nonlinearities in two degrees freedom are tested simulate possible effects including symmetric cubic hardening pitch yaw freedom; purely nonlinearity; combination quadratic, cubic, fifth-order both freedom. Results show presence introduces limit cycle oscillations post-flutter regime. Moreover, it demonstrated inclusion quadratic nonlinearity asymmetric subcritical behavior, where large deformations reached before predicted speed.