Flight Control System Having a Three Control Loop Design

• US 20080097658A1
• Filed: 11/08/2005
• Published: 04/24/2008
• Est. Priority Date: 11/08/2004
• Status: Active Grant

• Current Assignee: Textron Innovations Incorporated (Textron Inc)
• Original Assignee: Textron Innovations Incorporated (Textron Inc)
• Inventors: Schillings, John, Shue, Shyhpyng
• Granted Patent: US 8,473,124 B2
• Time in Patent Office: Days
• US Class Current: 701/8
• CPC Class Codes: G05D 1/101 specially adapted for aircraft

Abstract

A flight control system is configured for controlling the flight of an aircraft utilizing a three control loop design to robustly increase system performance. An inner loop comprises an improved linear quadratic regulator (LQR) search method, and an outer loop comprises a classic feedback summary gain design. A third loop comprises a steady state trim search method.

Claims

1. A flight control system for controlling the flight of an aircraft, the system comprising:

a first feedback loop using a linear quadratic regulator search method;

a second feedback loop using classic feedback control laws; and

a third feedback loop comprising a steady state trim search method.

2. The flight control system of claim 1, wherein the first feedback loop is an inner loop.

3. The flight control system of claim 1, wherein the first feedback loop achieves stabilization through use of an optimal phase margin and gain margin.

4. The flight control system of claim 1, wherein the first feedback loop achieves stabilization through use of an optimal phase margin and gain margin and wherein the first feedback loop utilizes an algorithm based on eigenvalue, eigenvector, and dampening ratio from time to determine the optimal phase margin and gain margin.

5. The flight control system of claim 1, wherein the first feedback loop utilizes at least one of full model decoupling, separation of control laws and gain scheduling.

6. The flight control system of claim 1, wherein the first feedback loop utilizes at least one of full model decoupling, the full model decoupling comprising decoupling a full aircraft model into longitudinal and lateral motions.

7. The flight control system of claim 1, wherein the second feedback loop is an outer loop.

8. The flight control system of claim 1, wherein the second feedback loop utilizes summary gain.

9. The flight control system of claim 1, wherein the second feedback loop automatically holds lateral path guidance in a heading select mode.

10. The flight control system of claim 1, wherein the third feedback loop automatically searches for an optimal trim condition at any flight conditions.

11. The flight control system of claim 10, wherein the third feedback loop searches for the optimal trim condition based on altitude rate.

12. The flight control system of claim 10, wherein the third feedback loop searches for the optimal trim condition based on roll rate.

13. The flight control system of claim 10, wherein the third feedback loop searches for the optimal trim condition based on yaw rate.

14. The flight control system of claim 10, wherein the third feedback loop utilizes a linear quadratic regulator method with a command generator to determine the optimal trim condition.

15. The flight control system of claim 10, wherein the third feedback loop utilizes a linear quadratic regulator method with a command generator to determine the optimal trim condition, the command generator comprising a steady state trim value with an initial trim condition.

16. The flight control system of claim 10, wherein the third feedback loop utilizes a linear quadratic regulator method with a command generator to determine the optimal trim condition, the command generator comprising a steady state trim value with an initial trim condition;

and

wherein a difference between a current flight state, the steady state trim value, and the initial trim condition is set as a tracking error.

17. The flight control system of claim 1, wherein a lateral heading is automatically engaged when a landing approach is missed.

18. The flight control system of claim 1, wherein the first, second, and third feedback loops are pre-programmed.

19. A method for controlling the flight of an aircraft, the method comprising:

stabilizing open loop systems utilizing a linear quadratic regulator search method;

guiding the aircraft utilizing classic feedback control laws; and

automatically determining optimal trim conditions utilizing steady state trim search control law.

20. A method for controlling the motion of a vehicle, the method comprising:

applying a linear quadratic regulator search method to a first set of inputs in a first feedback loop;

applying classic feedback control laws to a second set of inputs in a second feedback loop; and

applying steady state trim search control laws to determine optimal trim conditions.

21. A flight control system for controlling the flight of an aircraft, the system comprising:

an inner feedback loop, the inner feedback loop using one of a linear quadratic regulator search method or an H-infinity control;

an outer feedback loop, the outer feedback using one of a linear quadratic regulator search method, an H-infinity control, or classic feedback control laws; and

a third feedback loop comprising a steady state trim search method.