Flight control system for a hybrid aircraft in the yaw axis

• US 6,478,262 B1
• Filed: 07/17/2001
• Issued: 11/12/2002
• Est. Priority Date: 07/17/2001
• Status: Expired due to Term

• 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): Poon, Peter M.
• Assistant Examiner(s): Collins, Timothy D
• Application Number:
  US09/907,068
• Time in Patent Office: 483 Days
• Field of Search: 244/195, 244/185, 244/23.B, 244/6, 244/182, 244/76.B, 244/225, 244/17.13, 244/190, 701/301.4, 701/7, 701/10, 340/967, 340/969, 340/970
• US Class Current: 244/195
• CPC Class Codes: B64C 27/20 Rotorcraft characterised by having shrouded rotors, e.g. flying platforms
• CPC Class Codes: B64C 39/024 of the remote controlled vehicle type, i.e. RPV
• CPC Class Codes: B64U 10/13 Flying platforms
• CPC Class Codes: B64U 2201/10 autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
• CPC Class Codes: B64U 30/10 Wings
• CPC Class Codes: B64U 30/20 Rotors; Rotor supports
• CPC Class Codes: B64U 30/26 Ducted or shrouded rotors
• CPC Class Codes: B64U 50/13 using external fans or propellers
• CPC Class Codes: B64U 50/14 ducted or shrouded
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

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 yaw axis. Gain schedules for both differential collective and rudder 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 yaw 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 yaw axis;

a movable second control surface on a rotor system operable to direct the aircraft about said yaw 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 yaw 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 yaw 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 is a rudder.

4. The flight control system as recited in claim 3, wherein said rudder is mounted within a shroud.

5. The flight control system as recited in claim 1, wherein said second control surface includes a coaxial counter rotating rotor system having differential collective pitch.

6. The flight control system as recited in claim 5, wherein said coaxial counter rotating rotor system is 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 first axis comprising the steps of:

(1) providing a control command for a first 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 first vehicle 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 first vehicle 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 yaw moment about the yaw axis independent of the hybrid aircraft flight regime.

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

(1) providing a control command for a yaw 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 yaw axis; and

(8) communicating said second scaled control command to a aileron for control of the UAV about the yaw axis.

16. A method as recited in claim 15, wherein said step (1) includes a proportional 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 yaw moment about the yaw 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.