Fly-by-wire flight control system with electronic lead/lag damper algorithm
An electronic lead/lag damper algorithm implemented as part of the fly-by-wire flight control system to minimize or eliminate mechanical lead/lag dampers of a rotary wing aircraft. The electronic lead/lag damper algorithm uses a cross-feed control methodology that band-pass filters pitch and roll rates and feeds back a signal to the lateral and longitudinal cyclic inputs to provide electronic stability to rotor lag modes.
1. A rotary-wing aircraft comprising:
a rotor hub having at least one rotor blade assembly;
a lead/lag damper mounted to said rotor hub and said at least one rotor blade assembly, said lead/lag damper provides a first damping value, said first damping value less than a required damping value of said at least one rotor blade assembly; and
a fly-by-wire flight control system having an electronic lead/lag damper algorithm which provides a damping value which defines at least the difference between said first damping value and said required damping value.
2. The aircraft as recited in claim 1 , wherein said rotor hub includes a main rotor hub.
3. The aircraft as recited in claim 2 , wherein said main rotor hub forms a part of an articulated rotor system of a rotary wing aircraft.
4. The aircraft as recited in claim 1 , wherein said fly-by-wire type flight control system includes a model following control system.
5. The aircraft as recited in claim 1 , wherein said electronic lead/lag damper algorithm provides a cross-feed control methodology that band-pass filters a pitch rate and a roll rate then feeds back these filtered signals to both a lateral cyclic input and a longitudinal cyclic input to said fly-by-wire type flight control system.
6. The aircraft as recited in claim 5 , wherein said cross-feed control methodology band-pass filters said pitch rate and said roll rate in response to a rotor speed.
7. A fly-by-wire flight control system comprising:
a memory storing instructions operable to cause said fly-by-wire flight control system to perform an electronic lead/lag damper method with a cross-feed control methodology that band-pass filters a pitch rate and a roll rate then feeds back the respective signals to a lateral cyclic input and a longitudinal cyclic input of said fly-by-wire type flight control system.
8. The system as recited in claim 7 , wherein said cross-feed control methodology is filtered in response to a calculated frequency.
9. The system as recited in claim 8 , wherein said cross-feed control methodology band-pass filters said pitch rate and said roll rate in response to a rotor speed.
10. A fly-by-wire flight control system implemented method of lead/lag damping for a rotary-wing aircraft rotor system comprising the steps of:
(A) band pass filtering a pitch rate and a roll rate;
(B) cross-feeding the pitch rate and the roll rate from said step (A);
(C) feeding back the cross-feed signals from said step (B) to a lateral cyclic input and a longitudinal cyclic input of a fly-by-wire type flight control system.
11. A method as recited in claim 10 , wherein said step (A) further comprises:
(a) varying the band-pass filter in response to rotor speed.
12. A method as recited in claim 10 , wherein said step (A) further comprises:
(b) varying the band-pass filter center frequency in response to a calculated frequency.
13. A method as recited in claim 10 , further comprising the steps of:
(D) directly feeding a pitch rate and a roll rate to the lateral cyclic input and the longitudinal cyclic input of the fly-by-wire type flight control system.
14. The aircraft as recited in claim 1 , wherein said lead/lag damper reacts in-plane edgewise motion of said at least one rotor blade assembly to dampen vibration.
15. The system as recited in claim 7 , wherein said electronic lead/lag damper method supplements a lead/lag damper mounted to a rotor hub and at least one rotor blade assembly, the lead/lag damper provides a first damping value less than a required damping value of said at least one rotor blade assembly.
16. The system as recited in claim 15 , wherein said electronic lead/lag damper method provides a damping value which defines at least the difference between the first damping value and a required damping value.
17. The system as recited in claim 16 , wherein feeding back the cross-feed signals from said step (B) to the lateral cyclic input and the longitudinal cyclic input of the fly-by-wire type flight control system supplements a lead/lag damper mounted to a rotor hub and at least one rotor blade assembly, the lead/lag damper provides a first damping value less than a required damping value of the at least one rotor blade assembly.
18. The system as recited in claim 16 , wherein feeding back the cross-feed signals from said step (B) provides a damping value which defines at least the difference between the first damping value and a required damping value.