Trim augmentation system for a rotary wing aircraft

• US 6,648,269 B2
• Filed: 12/10/2001
• Issued: 11/18/2003
• Est. Priority Date: 12/10/2001
• Status: Active Grant

• Current Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation), The Boeing Co.
• Original Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Inventors: Brewer, Roy, Gold, Phillip Jeremy, Dryfoos, James B.
• Primary Examiner(s): Barefoot, Galen L.
• Application Number:
  US10/016,520
• Publication Number:
  US 20030106958A1
• Time in Patent Office: 708 Days
• Field of Search: 244/17.11, 244/17.13, 244/17.25, 244/177, 244/181, 244/182, 244/194, 244/195, 701/3-16
• US Class Current: 244/17.13
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

The flight control system includes a trim augmentation algorithm which advantageously provides two primary functions: direct augmentation of the rotor trim via on-axis stick input; and automatic cross-axis trim transfer as a function of the commanded yaw rate. In a first function of the present invention, when the aircraft is lagging the pilots commanded maneuver state the stick command is multiplied by a gain to direct the actual vehicle response toward said pilot commanded rate signal and improve the model following control laws. In a second function of the present invention, a cross-axis trim transfer function of the trim augmentation algorithm uses the commanded yaw rate to anticipate the trim change when the aircraft is rotating in winds. When a yaw maneuver is performed, the cross-axis trim transfer function automatically “stirs” the cyclic as the aircraft rotates about the yaw axis.

Claims

1. A method of augmenting a flight control system for a rotary wing aircraft comprising the steps of:

(1) identifying a direction of a rate error feedback signal for a first vehicle axis;

(2) identifying a direction of a pilot commanded rate signal in said first vehicle axis;

(3) determining whether said direction of said rate error feedback signal is equivalent to said direction of said pilot commanded rate signal; and

(4) augmenting said pilot commanded rate signal by a gain in response to said step (3) to direct an actual vehicle response in said first vehicle axis toward said pilot commanded rate signal.

2. A method as recited in claim 1, wherein said gain is one (1) if said rate error feedback signal of said step 1 is zero.

3. A method as recited in claim 1, wherein said first vehicle axis is pitch.

4. A method as recited in claim 1, wherein said first vehicle axis is roll.

5. A method as recited in claim 1, furthering including magnitude limiting said pilot commanded rate signal after said step (4).

6. A method as recited in claim 1, wherein said gain is in inches per second per percent of said pilot commanded rate signal.

7. A method as recited in claim 1, furthering including:

(5) summing said augmented pilot commanded rate signal from said step (4) with a limited Automatic Flight Control System trim rate signal.

8. A method as recited in claim 7, furthering including:

(6) integrating said signal from said step (5) wit a Primary Flight Control System trim integrator.

9. A method as recited in claim 8, furthering including feeding said signal from said step (6) to a Primary Flight Control System trim integrator.

10. A method as recited in claim 1, wherein said Step (4) further comprises:

augmenting said pilot commanded rate signal in response to a lag between the pilot commanded rate signal and the vehicle response.

11. A method as recited in claim 1, wherein said Step (4) further comprises:

augmenting said pilot commanded rate signal by a gain in response to said direction of said rate error feedback signal being equivalent to said direction of said pilot commanded rate signal of said step (3).

12. A method as recited in claim 1, wherein said Step (4) further comprises:

augmenting said pilot commanded rate signal in response to a lag between the pilot commanded rate signal and the vehicle response.

13. A method as recited in claim 1, wherein said Step (4) further comprises:

trimming said vehicle in said first vehicle axis to direct an actual vehicle response in said first vehicle axis.

14. A method of augmenting a flight control system for a rotary wing aircraft comprising the steps of:

(1) identifying a trim error signal; and

(2) precessing said current trim error signal in response to a commanded yaw rate.

15. A method as recited in claim 14, wherein said step 1 furthering includes:

(1a) identifying a current trim signal; and

(1b) subtracting said current trim signal from a nominal hover trim signal to determine said trim error signal.

16. A method as recited in claim 15, wherein said nominal hover trim signal is a predetermined value.

17. A method as recited in claim 14, wherein said step 2 furthering includes:

(2a) multiplying said current trim error signal by said commanded yaw rate.

18. A method as recited in claim 14, wherein said step 2 furthering includes precessing said current trim error signal in a direction opposite said commanded yaw rate direction.

19. A method of augmenting a flight control system for a rotary wing aircraft comprising the steps of:

(1) identifying a current pitch trim signal;

(2) subtracting said current pitch trim signal from a nominal hover pitch trim signal to determine a pitch trim error signal;

(3) identifying a current roll trim signal;

(4) subtracting said current roll trim signal from a nominal hover roll trim signal to determine a roll trim error signal;

(5) multiplying said pitch trim error signal and said roll trim error signal by a commanded yaw rate;

(6) cross feeding said pitch trim error signal to a roll trim signal; and

(7) cross feeding said roll trim error signal to a pitch trim signal.

20. A method as recited in claim 19, furthering including multiplying said pitch trim, error signal by a first gain and said roll trim error signal by a second gain prior to said step 5.

21. A method as recited in claim 20, wherein said first gain scales said pitch trim error signal to be proportional to a ratio of total available pitch and roll control.

22. A method as recited in claim 21, wherein said second gain scales said roll trim error signal to be proportional to a ratio of total available pitch and roll control.

23. A method as recited in claim 22, wherein said second gain is the negative inverse of said first gain.

24. A method as recited in claim 19, furthering including:

(8) summing said roll trim signal from said step (6) with a limited Automatic Flight Control System roll trim rate signal; and

(9) summing said pitch trim signal from said stop (7) with a limited Automatic Flight Control System pitch trim rate signal.

25. A method as recited in claim 24, furthering including:

(10) integrating said signal from said step (8) with a Primary Flight Control System roll trim integrator; and

(11) integrating said signal from said step (9) with a Primary Flight Control System pitch trim integrator.

26. A method as recited in claim 25, furthering including feeding said signals from said steps (10) and (11) to a rotary wing aircraft control surface.

27. A method as recited in claim 19, furthering including:

(8) summing said roll trim signal from said step (6) with an augmented pilot commanded roll rate signal; and

(9) summing said pitch trim signal from said step (7) with an augmented pilot commanded pitch rate signal.