Mast torque sensing for aircraft

Abstract

One embodiment described herein is a mast torque sensor system for a rotorcraft that includes a rotor shaft bearing strain sensor. In some embodiments, a mast torque sensor system is configured to calculate a rotor mast torque using rotor shaft bearing strain information. In one embodiment herein, the rotor shaft bearing strain sensor includes a fiber optic strain sensor.

Description

[0001] priority

[0002] This application claims priority to U.S. Provisional Application No. 63 / 390,999, filed on July 21, 2010. These and all other exogenous materials discussed herein are incorporated herein by reference in their entirety. In the event that a definition or use of a term in an incorporated reference is inconsistent or conflicts with the definition of that term provided herein, the definition of that term provided herein applies, and the definition of that term in the reference does not apply. Technical Field

[0003] The field of the invention is aircraft monitoring. Background Art

[0004] In rotorcraft with rigid rotors, monitoring mast moments is important because large mast moments can cause sudden changes in the aircraft's attitude. Rotor mast moment information can warn of hazardous conditions as well as characterize the aircraft's attitude.

[0005] Conventional mast moment sensors can be complex and unreliable. Many conventional mast moment sensing systems use complex optical systems that take up a lot of space. These systems are often packaged within complex powertrain components, making the mast moment sensing system difficult to maintain or replace. Summary of the invention

[0006] In one aspect herein, mast moments are monitored using fiber optic strain sensors configured to measure strain around a propeller rotor shaft bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 An aircraft including an embodiment of a mast moment sensing system is illustrated.

[0008] Figure 2 A cross-sectional view of a propulsion system including an embodiment of a mast moment sensing system is illustrated.

[0009] Figure 3 Pictured Figure 2 A detailed view of multiple aspects of the propulsion system.

[0010] Figure 4A A view of the bearing sleeve in an unstrained state is illustrated.

[0011] Figure 4B A view of a bearing sleeve in a strained state is illustrated.

[0012] Figure 5 Various embodiments of a mast moment sensing system implemented in a rotor system including a gearbox are illustrated.

[0013] Figure 6 A method for determining the mast moment of a propulsion system is illustrated.

[0014] Fig. 7A Various embodiments of aspects of bearing sleeves and fiber optic strain sensors are illustrated.

[0015] Figure 7B Pictured Figure 7B Cross-section of multiple aspects of the bearing sleeve and the optical fiber strain sensor.

[0016] Figure 8 Pictured Fig. 7A Isometric views of multiple aspects of the same bearing sleeve and fiber optic strain sensor.

[0017] Fig. 9 The diagram shows Figure 2 An isometric view of various aspects of an embodiment of the same propulsion system. DETAILED DESCRIPTION

[0018] In one aspect herein, this problem is addressed using a fiber optic strain sensor configured to measure strain around a propulsion rotor shaft bearing.

[0019] Fiber optic strain sensors as implemented in some embodiments herein can be robust and simple. Figure 2 Embodiments include a mast torque sensing system without any moving parts.

[0020] Figure 1 A tiltrotor aircraft 300 is illustrated including a mast moment sensing system 108 . Figure 1 The aircraft 300 comprises an electric vertical take-off and landing (eVTOL) tilt-rotor aircraft. However, other embodiments of the mast moment sensing system may be configured for use in any other type of aircraft.

[0021] Figure 2A pusher rotor propulsion system 100 including an embodiment of a mast moment sensing system is shown. The pusher rotor propulsion system 100 includes a pusher rotor shaft 101 that connects a pusher rotor hub 110 to hub shaft bearings 103a and 103b. A nacelle structure 104 is shown. Bearing sleeves 105a and 105b are interposed between the nacelle structure 104 and the main hub shaft bearings 103a and 103b. The bearing sleeves 105a and 105b include grooves 106a, 106b, 106c, and 106d that are configured to accommodate fiber optic strain sensor cables 107a, 107b, 107c, and 107d. The fiber optic strain sensor cables 107a and 107b are configured to measure strain of the bearing sleeve 105a. The optical fiber strain sensor cables 107c and 107d are configured to measure the strain on the bearing sleeve 105b. The optical fiber strain sensor cables 107a and 107b are wound around the bearing sleeve 105a. The optical fiber strain sensor cables 107c and 107d are wound around the bearing sleeve 105b.

[0022] When combined with embodiments of the propulsion systems described in PCT / US22 / 13272 filed on January 21, 2022 and U.S. Provisional Application No. 63 / 140,515 filed on January 22, 2021 (which applications are incorporated herein by reference in their entirety), the presently described embodiments of the mast moment sensing system can have certain advantages.

[0023] Figure 3 Pictured Figure 2 Detailed view of various aspects of a pusher rotor propulsion system. Fiber optic strain sensor cables 107a and 107b are shown. Hub shaft bearing 103a and bearing sleeve 105a are also shown.

[0024] exist Figure 2 In the embodiment of the present invention, the hub shaft bearing sleeve 105a comprises metal. The nacelle structure 102 comprises a composite material. However, in other embodiments, any suitable material may be used.

[0025] Figure 5 The mast moment sensing system 108 shown in FIG. 1 includes fiber optic cables 107a, 107b, 107c, and 107d. The mast moment sensing system 108 can measure the strain of the fiber optic strain sensing cables 107a, 107b, 107c, and 107d. When the fiber optic strain sensing cables 107a, 107b, 107c, and 107d are subjected to force, the measured strain will change as the bearing sleeves 105a and 105b deform. It should be appreciated that those skilled in the art can interpret the fiber optic strain sensing signal into a strain reading.

[0026] Figure 4AA view of the bearing sleeve 105a in an unstrained state is illustrated. Figure 4B The bearing sleeve 105a is shown in a strained state. During a certain mast moment, the force will cause the bearing 103a and the bearing sleeve 105a to deform. By measuring the strain, the mast moment can be determined.

[0027] Figure 5 The mast moment sensing system 108 includes fiber optic strain sensing sensors 107a, 107b, 107c and 107d configured to measure strain near each of the two main rotor shaft bearings 502a and 502b. The mast moment sensor system measures strain transmitted through the two rotor shaft bearings, which are the main source of mast moment transmission between the nacelle structure 104 and the rotor shaft 101.

[0028] In contrast to some conventional methods for measuring mast moments, which measure the offset between a first part of a sensor system in a rotating frame and a second part of a sensor system in a rotating frame, Figure 2 The sensor system is in a non-rotating reference frame. This allows for robustness and simplicity.

[0029] Figure 5 Fiber optic strain sensor cables 107a, 107b, 107c and 107d are shown. Figure 6 A method for the mast moment module 602 to determine the mast moment of the pusher rotor 109 is shown. The fiber optic strain sensor module 601 receives a set of signals from the first set of fiber optic cables 107a. The fiber optic strain sensor module 601 then receives a set of grating reflections from the fiber optic strain sensing cables 107a. The fiber optic strain sensor module 601 calculates the strain at the grating on 107a. The fiber optic strain sensor module 601 sends the grating strain information to the mast moment module 602. The process is repeated for the fiber optic strain sensing cables 107b, 107c, and 107d. The mast moment module 602 uses the determined grating strain information to determine the magnitude and direction of the mast moment. Figure 5 In the embodiment of FIG. 5 , bearings 502 a and 502 b are located in the gearbox 501 .

[0030] In some embodiments of the mast moment sensing system, the mast moment module may include a lookup table of empirically correlated mast moment and bearing sleeve deformation information that may be used to calculate the mast moment. Higher resolution fiber optic strain sensors enable generation of higher resolution bearing deformation maps.

[0031] Fig. 7A Different embodiments of the bearing sleeve 801 are shown. Fig. 7AIn the embodiment of FIG. 8 , the outside of the bearing sleeve 801 is configured for a nacelle structure that is straight (non-tapered) at the bearing sleeve to nacelle structure interface.

[0032] Figure 8 A bearing sleeve 801 is illustrated. An armored fiber optic cable portion 803 is illustrated. The armor protects from environmental damage. The fiber optic cable includes a set of gratings 802 spaced around the length of the fiber optic cable. Figure 8 The embodiment includes fiber optic temperature sensors 803a and 803b for calibrating the fiber optic strain readings based on current temperature and weather conditions.

[0033] Figure 7B Pictured Fig. 7A cross section. Figure 8 An isometric view of the bearing sleeve 801 is shown. The bearing sleeve therefore serves very well as a space for the optical fibre strain sensing cable - resulting in a very compact mast moment sensor package.

[0034] Fig. 9 The diagram shows Figure 1 An isometric view of aspects of the same pusher rotor propulsion system shown. For clarity, the main pusher rotor hub and pusher rotor blades are not shown.

[0035] like Figure 2 As shown, the first and second optical fiber strain sensing cables 107a and 107b are fixed relative to the bearing sleeves 105a and 105b. That is, the optical fiber strain sensors 107a and 107b are in the non-rotating part of the propulsion system assembly. This facilitates integration because the wires can be connected to the device in the fuselage without the use of slip rings or similar devices.

[0036] The optical fiber strain sensor may include any suitable optical fiber strain sensor, including: a fiber Bragg grating (FBG) sensor; an optical time domain reflectometer sensor; or any other suitable sensor.

[0037] The Mast Torque Sensor System produces good mast torque readings. The Fiber Bragg Grating (FBG) sensor is both sensitive and robust - enabling consistent and accurate measurements.

[0038] The mast moment module 602 may use the signals from the fiber optic strain sensors to calculate the mast moment load acting on the hub shaft 101. The strain information may then be used to determine the mast moment.

[0039] It should be understood that the fiber optic strain sensor may measure strain using either grating frequency or local fiber material strain.

[0040] It should be noted that any statement involving a fiber optic strain sensor module, a mast moment module, or a similar module should be interpreted as including any suitable combination of computing devices, including servers, interfaces, systems, databases, agents, peer nodes, engines, controllers, or other types of computing devices operating individually or collectively. These computing devices may include a processor configured to execute software instructions stored on a tangible, non-temporary computer-readable storage medium (e.g., a hard drive, a solid-state drive, RAM, flash memory, ROM, etc.). These software instructions preferably configure the computing device to provide roles, responsibilities, or other functions discussed with respect to the above-disclosed devices. In some embodiments, various servers, systems, databases, or interfaces may exchange data using standardized protocols or algorithms, which may be based on HTTP, HTTPS, AES, public-private key exchange, network service APIs, known financial transaction protocols, or other electronic information exchange methods. Data exchange is preferably performed over a packet switching network, the Internet, a LAN, a WAN, a VPN, or other types of packet switching networks.

[0041] For convenience, the term pusher rotor is used herein. As used herein, the term pusher rotor should be understood to include a rotor, a pusher rotor, a propeller thruster, a fan, a ducted fan or any other similar device.

[0042] Those skilled in the art will appreciate that the rotor shaft bearings may be of any suitable type, including angular contact bearings, tapered roller bearings, bushings, or any other suitable type of bearing. In addition, there may be any number of bearings.

[0043] Although some embodiments herein are configured for use with electric vertical take-off and landing (eVTOL) aircraft, embodiments of the mast torque sensing system may be equally applicable to other types of aircraft, including helicopters, turbine-powered tilt-rotor aircraft, non-tilt-rotor vertical take-off and landing aircraft, turbine-powered helicopters, or any other type of aircraft.

Claims

1. A VTOL aircraft comprising two or more fiber optic strain sensors configured to sense side loads on a pusher rotor shaft.

2. The VTOL aircraft according to claim 1, wherein: The VTOL aircraft includes a pusher rotor shaft bearing.

3. The VTOL aircraft according to claim 2, wherein: The VTOL vehicle includes a bearing sleeve interposed between the pusher rotor shaft bearing and the vehicle structure.

4. The VTOL aircraft according to claim 3, wherein: The bearing sleeve is configured to accommodate a fiber optic strain sensor around the circumference of the bearing sleeve.

5. A rotorcraft mast torque sensor system, comprising a first rotor shaft bearing optical fiber strain sensor and a second rotor shaft bearing optical fiber strain sensor.

6. The rotorcraft mast torque sensor system according to claim 5, wherein: The mast moment sensor system includes a mast moment module configured to calculate mast moment information from the first rotor shaft bearing fiber optic strain sensor and the second rotor shaft bearing fiber optic strain sensor.

7. A mast moment sensing module, the mast moment sensing module being configured as follows: receiving optical fiber strain sensor information corresponding to rotor shaft bearing deformation; The received fiber optic strain sensor information is used to calculate the mast moment on the rotor shaft.

8. The mast torque sensing module according to claim 7, wherein: The mast moment sensing module is additionally configured to perform the additional step of receiving fiber optic strain sensor information from a second fiber optic strain sensor, wherein the second fiber optic strain sensor is configured to detect deformation of a second rotor shaft bearing.

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