ASSESSMENT OF A STATE-SPACE AEROELASTIC ROTOR MODEL FOR ROTORCRAFT DYNAMICS ANALYSIS

The aim of the paper is the assessment of a methodology for the identification of helicopter rotor state-space aeroelastic representation relating hub motion and blade pitch controls to the loads transmitted to the fuselage. It is suited for the simulation of the dynamics of com- prehensive complete helicopter configurations, particularly in application concerning analysis of rotorcraft-pilot coupling (RPC) phenomena, as well as synthesis control laws. Observing the inherently time-periodic nature of theoretical formulations describing rotor aeroelasticity, the state-space form identification method consists of a three-step process in which filtering of spectra of responses to small-perturbation harmonic inputs is followed by the rational form ap- proximation of the corresponding transfer functions. Considering a Bo-105-type helicopter, the numerical investigation is focused on: analysis of critical parameters for an accurate and effi- cient identification of transfer functions, interpretation of the additional states related to their rational approximation, validation of the state-space rotor aeroelastic representation, and ap- plication to RPC aeroelastic phenomenon. Further, the sensitivity of rotor aeroelastic operator and correspondingly RPC simulations to different aerodynamic load models is also investigated