The research work on helicopter rotor dynamics and control has led to its most recent results in the framework of a very fruitful, interdisciplinary cooperation with the Rotorcraft Center of Excellence at the University of Maryland (USA) on Higher Harmonic Control (HHC) and Individual Blade Control (IBC). The main results obtained in this research can be summarized as follows:

·         First study of the effect of periodic zeros in rotorcraft aeromechanics: the zeros of a dynamic system play a key role in determining its closed-loop behavior. The rotorcraft dynamics community had been able to mostly neglect the issue because rotor systems were not actively controlled. As rotor active controls become technologically feasible and desirable, the calculation and study of zeros must become a routine step of rotor design.

·         First study of the effects of closed-loop HHC/IBC on the aeroelastic stability of a helicopter rotor: despite over three decades of research in HHC/IBC, no information was available on how an HHC/IBC system would affect, e.g., the in-plane damping of a helicopter rotor. No results showing the effects of HHC/IBC on Floquet characteristic exponents for rotor and/or fuselage modes had ever been presented. This is clearly a vital piece of information for the future use of active rotor controls in configurations with inherently low in-plane damping such as hingeless and bearingless rotors.

·         First study of the effects of closed-loop HHC/IBC on the aeroelastic stability of a helicopter, considered as a discrete system: a typical model of a helicopter with HHC or IBC contains continuous portions (e.g., rotor and fuselage dynamics) and discrete portions (e.g., harmonic analysis to extract vibratory components, HHC inputs updated once per revolution, etc.). We have modeled the entire system as a discrete multirate one and developed the first rigorous solution of the aeroelastic stability problem.

As far as the identification of helicopter dynamics is concerned, both time domain and frequency domain methods have been applied to the derivation of black box models of rotor response to control inputs in the case of hover (time invariant models). For the general case of periodic and generally time varying conditions, algorithms for the identification of periodic and Linear Parametrically varying (LPV) models have been worked out.
  Current work, in cooperation with AgustaWestland,  is dealing with combined time and frequency domain system identification problems for helicopter flight mechanics and with the direct identification of rotor dynamics from wind tunnel experiments.