Blade pitch control

• US 8,262,352 B2
• Filed: 09/08/2009
• Issued: 09/11/2012
• Est. Priority Date: 09/12/2008
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Gainford, David Michael, Holt, Jonathan Edmund, Garner, Stephen Granville
• Primary Examiner(s): LOOK, EDWARD K
• Assistant Examiner(s): Grigos, William
• Application Number:
  US12/555,457
• Publication Number:
  US 20100068056A1
• Time in Patent Office: 1,099 Days
• Field of Search: 416/26, 416/27, 416/30, 416/31, 416/35, 416/43, 416/1, 416/147, 416/151, 416/155, 416/162, 416/168.A
• US Class Current: 416/1
• CPC Class Codes: B64C 11/306 specially adapted for contrarotating propellers
• CPC Class Codes: B64C 11/44 electric
• CPC Class Codes: B64C 11/48 Units of two or more coaxial propellers
• CPC Class Codes: B64D 2027/005 Aircraft with an unducted turbofan comprising contra-rotating rotors, e.g. contra-rotating open rotors [CROR]
• CPC Class Codes: F01D 7/00 Rotors with blades adjustable in operation; Control thereof for reversing F01D1/30
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A method of controlling blade pitch angle, including comparing demanded and measured blade pitch angle and calculating any difference therebetween, in a primary electrical control system, where there is a difference, applying torque to a blade pitch regulator to reduce the magnitude of the difference to zero, and in a secondary electrical control system, where the difference is greater than a pre-determined threshold, applying torque to a blade pitch regulator to reduce the magnitude of the difference to the threshold. Also an electrical system of blade pitch angle control for a set of blades including primary and secondary electrical control systems, means for comparing demanded and measured blade pitch angle and calculating any difference therebetween, a look-up function having the difference as its input and outputting a required torque, and a torque regulator to apply the required torque to the set of blades.

Claims

1. A method of controlling blade pitch angle using a primary and a secondary electrical control system, the method comprising the steps of:

a. Comparing a demanded and a measured blade pitch angle and calculating any difference therebetween,

b. in the primary electrical control system, where there is a difference, applying a torque to a blade pitch regulator to reduce the magnitude of the difference to zero, and

c. in the secondary electrical control system, where the difference is greater than a pre-determined threshold, applying a further torque to a blade pitch regulator to reduce the magnitude of the difference to the pre-determined threshold.

2. A method as claimed in claim 1 wherein step 1a is performed independently for each of the primary and secondary electrical control systems.

3. A method as claimed in claim 1 wherein the difference is positive when the measured blade pitch angle is more coarse than the demanded blade pitch angle.

4. A method as claimed in claim 3 wherein the torque and the further torque are applied to change the blade pitch angle to be finer than its measured blade pitch angle.

5. A method as claimed in claim 1 wherein the torque and the further torque applied are proportional to the difference.

6. A method as claimed in claim 1 wherein above the threshold both the primary and secondary electrical control systems apply torque to the blade pitch regulator.

7. A method as claimed in claim 1 wherein, in the event of a failure of at least one of the primary and secondary electrical control systems, the method further comprises the step of applying a failsafe torque control to the blade pitch angle to achieve a failsafe condition.

8. An electrical system of blade pitch angle control for a set of blades, the system comprising:

a. a primary electrical control system comprising a primary look-up function,

b. a secondary electrical control system comprising a secondary look-up function,

c. means for comparing a demanded and a measured blade pitch angle and calculating any difference therebetween, the means coupled to the primary and secondary electrical control systems,

d. the primary look-up function having the difference as its input and outputting a required torque,

e. the secondary look-up function having the difference as its input and outputting a further required torque, the output being zero below an input threshold, and

f. a torque regulator coupled to the primary and secondary electrical control systems to apply the required torque and the further required torque to the set of blades.

9. A system as claimed in claim 8 wherein each of the primary and secondary electrical control systems comprises means for calculating the any difference and a torque regulator.

10. A system as claimed in claim 8 wherein the required torque and the further required torque is proportional to the difference.

11. A system as claimed in claim 8 wherein the system further comprises trip logic that triggers when at least one of the primary and secondary electrical control systems fails.

12. A system as claimed in claim 11 wherein, when one of the primary and secondary electrical control systems fails, the trip logic triggers that electrical control system to trip.

13. A system as claimed in claim 11 wherein, when one of the primary and secondary electrical control systems fails, the trip logic triggers both electrical control systems to trip.

14. A system as claimed in claim 11 wherein the trip logic triggers a mechanical response.