Sikorsky have been granted patent number 8,548,648 for “Fly-by-wire flight control system with electronic lead/lag damper algorithm”. Two particular sections of interest from the official US Patent & Trademark Office website posting are listed below
Background of the Invention
The present invention relates to a fly-by-wire flight control system, and more particularly to an electronic lag damper algorithm implemented as part of the fly-by-wire flight control system which augments a mechanical lead/lag damper for a rotor system of a rotary wing aircraft.
Rotary-wing aircraft include lead/lag dampers to increase rotor blade lead/lag mode damping characteristics. The damper assembly reacts against lead/lag motions of each rotor blade assembly of the rotor system to dampen vibration. Typically, the dampers are sized for a variety of considerations including the need to stabilize ground resonance of the rotary-wing aircraft.
Although effective, current dampers operate under high pressures and may require relatively comprehensive maintenance attention. Furthermore, as each rotor blade requires a lead/lag damper, the dampers increase the overall structural envelope and weight of the rotor system such that aircraft weight is concomitantly increased.
Accordingly, it is desirable to provide a flight control system which provides an electronic lead/lag damper algorithm to minimize or eliminate mechanical lead/lag dampers within a rotor system of a rotary wing aircraft to thereby decrease the overall structural envelope and weight of the rotor system.
Summary of the Invention
The flight control system according to the present invention includes an electronic lag damper algorithm implemented as part of the fly-by-wire flight control system to minimize or eliminate mechanical lead/lag dampers for an articulated rotor system of a rotary wing aircraft.
The electronic lead/lag damper algorithm utilizes a cross-feed control methodology that band-pass filters pitch and roll rates then feeds back a signal to the lateral and longitudinal cyclic inputs to add electronic stability to rotor lag modes. The rotor lag modes typically interact with the landing gear frequency during startup/shutdown to produce a phenomenon called ground resonance which this invention reduces during on-ground and other interactive modes. The stabilization added by the electronic lag damper allows the mechanical dampers on the rotor system to be reduced in size, by providing equivalent (or more than equivalent) electronic lag damping.
The electronic lead/lag damper algorithm is implemented with a very high degree of reliability as part of a fly-by-wire control system.
The present invention therefore provides an electronic lead/lag damper algorithm to minimize or eliminate mechanical lead/lag dampers within a rotor system of a rotary wing aircraft to thereby decrease the overall structural envelope and weight of the rotor system.
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