Robust Approach for Ground Resonance Aeroservoelastic Stability of Helicopters

摘要

This paper discusses the use of robust analysis for the sizing of critical rotorcraft components likernlead-lag dampers taking into account several types of uncertainties in the vehicle model without unduernsimplifications. The problem is reformulated as a feedback loop, with the uncertain part of the systemrnis isolated in the return path. The so-called m-analysis is used to determine whether a prescribed set ofrnuncertain parameters, whose value is bounded, guarantees the stability of the system. The approach isrnapplied to a simplified ground-resonancemodel first, made of the main rotor cyclic lead-lag multibladerncoordinates and the airframe roll mode, and to a complete and detailed aeroservoelastic model of thernhelicopter. The feasible space of stiffness and damping characteristics of linear viscoelastic lead-lagrndampers applied to a certain model is computed first. Subsequently, using the m-analysis, the stabilityrnof the system for damper parameters within a design subspace of the feasible space is verified for arngiven range of uncertainty on other system parameters, including the modal parameters of the rollrnmode and some properties of a simplified stability and control augmentation system.