Helicopter blade response and aeromechanical stability with a magnetorheological fluid based lag damper

This paper explores the feasibility of using Magnetorheological (MR) fluid- based dampers for lag damping augmentation in helicopters. An MR damper mod el is integrated with a rotor aeromechanical model. Two different control s chemes are presented-namely the On-Off scheme and the Feedback Linearizatio n scheme. In the On-Off scheme, two criteria are used to obtain equivalent linear damping for the nonlinear MR damper as a function of the size of per turbation and the applied field. The Feedback Linearization scheme uses a f eedback controller to linearize the force output of the MR damper. The two control schemes are compared for lag transient response in ground resonance and their ability to reduce periodic damper loads in forward flight. It is shown that an MR damper of a size comparable to an elastomeric damper can provide sufficient damping for ground resonance stabilization and can signi ficantly reduce periodic damper loads with a judicious choice of operation scheme.