Flight control system for a hybrid aircraft in the pitch axis

• US 6,474,603 B1
• Filed: 09/25/2001
• Issued: 11/05/2002
• Est. Priority Date: 09/25/2001
• Status: Active Grant

• Current Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Original Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Inventors: Scott, Mark W., Kinkead, W. Douglas
• Primary Examiner(s): Swiatek, Robert P.
• Assistant Examiner(s): Collins, Timothy D.
• Application Number:
  US09/962,038
• Time in Patent Office: 406 Days
• Field of Search: 244/195, 244/185, 244/23.B, 244/6, 244/182, 244/76.B, 244/225, 244/17.13, 701/301.4, 701/7, 701/10, 340/967, 340/969, 340/970
• US Class Current: 244/195
• CPC Class Codes: G05D 1/0825 using mathematical models

Abstract

A flight control system includes a blending algorithm which evaluates the current flight regime and determines the effectiveness of the flight controls to effect the rotational moment of a hybrid vehicle about the pitch axis. Gain schedules for both pitch cyclic and elevator control provide a quantitative measure of control effectiveness. Based on the respective gain schedules, the algorithm determines how much of the control commands should be sent to each control surface. The result is that for a given control command, the same amount of pitch moment will be generated regardless of flight regime. This simplifies the underlying flight control law since the commands it generates are correct regardless of flight regime.

Claims

1. A flight control system for a hybrid aircraft comprising:

a movable first control surface not operably connected to a rotor system operable to direct an aircraft about a pitch axis;

a movable second control surface on a rotor system operable to direct the aircraft about said pitch axis;

a storage device having a blending algorithm, said blending algorithm determining a first gain for said first control surface according to a first gain schedule, and determining a second gain for said second control surface according to a second gain schedule in response to a control input for said pitch axis; and

a controller in communication with said first control surface, said second control surface, and said storage device, said controller operable to receive a control command for said pitch axis and actuate said first control surface according to said first gain and said second control surface according to said second gain.

2. The flight control system as recited in claim 1, wherein said first gain schedule and said second gain schedule relate control surface deflection to vehicle airspeed.

3. The flight control system as recited in claim 1, wherein said first control surface includes an elevator.

4. The flight control system as recited in claim 3, wherein said first control surface includes a flaperon.

5. The flight control system as recited in claim 1, wherein said second control surface includes a swashplate to effect a pitch cyclic change in a rotor system.

6. The flight control system as recited in claim 5, wherein said rotor system includes a coaxial counter rotating rotor system mounted within a duct.

7. The flight control system as recited in claim 1, wherein said hybrid aircraft is an unmanned aerial vehicle.

8. A method of controlling a hybrid aircraft about a pitch axis comprising the steps of:

(1) providing a control command for a pitch vehicle axis;

(2) splitting said control command to provide a first control command and a second control command;

(3) multiplying said first control command by a first gain according to a first gain schedule to provide a first scaled control command;

(4) multiplying said second control command by a second gain according to a second gain schedule to provide a second scaled control command;

(5) communicating said first scaled control command to a first movable control surface not operably connected to a rotor system for control of the hybrid aircraft about the pitch axis; and

(6) communicating said second scaled control command to a second movable control surface on a rotor system for control of the hybrid aircraft about the pitch axis.

9. A method as recited in claim 8, wherein said step (1) includes a proportional plus integral control command.

10. A method as recited in claim 9, further including limiting said integral control command.

11. A method as recited in claim 9, further including limiting said second scaled control command.

12. A method as recited in claim 11, further including:

identifying when the limit of said second scaled control command is reached; and

holding an integral control command of said second control command in a limited direction in response to said identifying step.

13. A method as recited in claim 11, further including:

identifying when the limit of said second control command is reached; and

adding in said first control command to assist said second control command.

14. A method as recited in claim 8, wherein said first and second scaled control command provide the same amount of aircraft pitch moment about the pitch axis independent of the hybrid aircraft flight regime.

15. A method of controlling a hybrid unmanned aerial vehicle (UAV) about a pitch axis within a transition flight region comprising the steps of:

(1) providing a control command for a pitch axis;

(2) splitting said control command to provide a first control command and a second control command;

(4) multiplying said first control command by a first gain according to a first gain schedule to provide a first scaled control command;

(4) multiplying said second control command by a second gain according to a second gain schedule to provide a second scaled control command;

(7) communicating said first scaled control command to a rotor system for control of the UAV about the pitch axis; and

(8) communicating said second scaled control command to an elevator for control of the UAV about the pitch axis.

16. A method as recited in claim 15, wherein said step (1) includes aproportional plus integral control command.

17. A method as recited in claim 15, wherein said first and second scaled control command provide the same amount of pitch moment about the pitch axis independent of the UAV flight regime.

18. A method as recited in claim 15, further including limiting said second scaled control command.

19. A method as recited in claim 18, further including:

identifying when the limit of said second control command is reached; and

adding in said first control command to assist said second control command.