Aircraft Mast Moment Detection

Abstract

A mast moment sensor system for a rotary wing aircraft comprising a rotor shaft bearing strain sensor is described in one embodiment of this specification. In some embodiments, the mast moment sensor system is configured to calculate the mast moment of the rotor using rotor shaft bearing strain information. In one embodiment of this specification, the rotor shaft bearing strain sensor comprises an optical fiber strain sensor.

Description

Technical Field

[0001] The field of the present invention is aircraft monitoring.

Background Art

[0002] Monitoring the mast moment is important in rotary-wing aircraft with rigid rotors because large mast moments can cause sudden changes in aircraft attitude. The mast moment information of the rotor can warn of dangerous conditions and characterize the attitude of the aircraft.

[0003] Conventional mast moment sensors are complex and may have low reliability. Many conventional mast moment detection systems use complex optical systems that occupy a large space. Such systems are often packaged inside a complex power train assembly, making it difficult to maintain or replace the mast moment detection system.

Summary of the Invention

[0004] In one aspect of the present specification, the mast moment is monitored using an optical fiber strain sensor configured to measure strain around a propeller shaft bearing.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

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DETAILED DESCRIPTION OF THE INVENTION

[0006] The problem in one aspect of this specification is solved by using an optical fiber strain sensor configured to measure strain around a propeller shaft bearing. The optical fiber strain sensors as implemented in some embodiments of this specification would be robust and simple. The embodiment of FIG. 2 includes a mast moment detection system without moving parts.

[0007] In FIG. 1, a tiltrotor aircraft 300 with a mast moment detection system 108 is shown. The aircraft 300 of FIG. 1 includes an electric vertical takeoff and landing (eVTOL) tiltrotor aircraft. However, other embodiments of the mast moment detection system may be configured for use with any other type of aircraft.

[0008] Figure 2 shows a propeller propulsion system 100 with an embodiment of a mast moment detection system. The propeller propulsion system 100 includes a propeller shaft 101 that connects a propeller hub 110 to hub shaft bearings 103a and 103b. A nacelle structure 104 is shown. Bearing sleeves 105a and 105b are disposed between the main hub shaft bearings 103a, 103b and the nacelle structure 104. The bearing sleeves 105a and 105b include grooves 106a, 106b, 106c, and 106d configured to receive optical fiber strain sensor cables 107a, 107b, 107c, and 107d. The optical fiber strain sensing cables 107a and 107b are configured to measure the strain of the bearing sleeve 105a. The optical fiber strain sensing cables 107c and 107d are configured to measure the strain on the bearing sleeve 105b. The optical fiber strain sensing cables 107a and 107b are wound around the bearing sleeve 105a. The optical fiber strain sensing cables 107c and 107d are wound around the bearing sleeve 105b.

[0009] The embodiments of the mast moment detection system described herein have certain effects when incorporated with the embodiments of the propulsion system described in PCT / US22 / 13272, filed January 21, 2022, and U.S. Provisional Application No. 63 / 140,515, filed January 22, 2021, which are hereby incorporated by reference in their entirety.

[0010] Figure 3 shows a detailed view of an aspect of the propeller propulsion system of Figure 2. The optical fiber strain sensing cables 107a and 107b are shown. The hub shaft bearing 103a and the bearing sleeve 105a are also shown.

[0011] In the embodiment of Figure 2, the hub shaft bearing sleeve 105a includes metal. The nacelle structure 102 includes a composite material. However, any suitable material can be used in other embodiments.

[0012] The mast moment detection system 108 shown in FIG. 5 includes optical fiber cables 107a, 107b, 107c, and 107d. The mast moment detection system 108 can measure the strain of the optical fiber strain detection cables 107a, 107b, 107c, and 107d. When the optical fiber strain detection cables 107a, 107b, 107c, and 107d are subjected to force, the measured strain changes as the bearing sleeves 105a and 105b deform. It should be recognized by those skilled in the art that the optical fiber strain detection signal can be interpreted as a strain measurement value.

[0013] FIG. 4A shows a view of the non-deformed bearing sleeve 105a. FIG. 4B shows the deformed bearing sleeve 105a. During a specific mast moment force, the force will deform the bearing 103a and the bearing sleeve 105a. The mast moment can be determined by measuring the strain.

[0014] The mass moment detection system 108 of FIG. 5 includes optical fiber strain detection sensors 107a, 107b, 107c, and 107d configured to measure the strain in the vicinity of each of the two main rotor shaft bearings 502a and 502b. The mast moment sensor system measures the strain transmitted through the two rotor shaft bearings, which is the main cause of mast moment transmission between the nacelle structure 104 and the rotor shaft 101.

[0015] Contrary to some conventional methods for measuring mast moment, which measure the deflection between a first part of the sensor system within the rotating frame and a second part of the sensor system that was within the rotating frame, the sensor system of FIG. 2 is within a non-rotating reference frame. Therefore, robustness and simplicity can be achieved.

[0016] In FIG. 5, fiber optic strain sensor cables 107a, 107b, 107c, and 107d are shown. FIG. 6 shows a method by which the mast moment module 602 determines the mast moment of the prop rotor 109. The fiber optic strain sensor module 601 receives a series of signals from the first set of fiber optic cables 107a. Next, the fiber optic strain sensor module 601 receives a series of fiber optic diffraction grating reflections from the fiber optic strain sensing cable 107a. The fiber optic strain sensor module 601 calculates the strain at the diffraction grating on 107a. The fiber optic strain sensor module 601 transmits the diffraction grating strain information to the mast moment module 602. This process is repeated for the fiber optic strain sensing cables 107b, 107c, and 107d. The mast moment module 602 determines the magnitude and direction of the mast moment by using the known diffraction grating strain information. In the embodiment of FIG. 5, the bearings 502a and 502b are installed within the gearbox 501.

[0017] In some embodiments of the mast moment detection system, the mast moment module may comprise a look-up table based on an empirical correlation between the mast moment and the bearing sleeve deformation information, and the look-up table can be used to calculate the mast moment. Higher resolution fiber optic strain sensors make it possible to generate a higher resolution bearing deformation map.

[0018] FIG. 7A shows a different embodiment of the bearing sleeve 801. In the embodiment of FIG. 7A, the outside of the bearing sleeve 801 is configured for a nacelle structure where the interface between the bearing sleeve and the nacelle structure is linear (non-tapered).

[0019] Figure 8 shows a bearing sleeve 801. An armored optical fiber cable section 803 is shown. The armor protects against environmental damage. The optical fiber cable includes grating groups 802 spaced approximately the length of the optical fiber cable. The embodiment of FIG. 8 includes optical fiber temperature sensors 803a and 803b for calibrating optical fiber strain measurements against current temperature and weather conditions.

[0020] FIG. 7B shows a cross-section of FIG. 7A. FIG. 8 shows an isometric view of the bearing sleeve 801. Thus, the bearing sleeve functions very well as a space for the optical fiber strain sensing cable, resulting in a very compact mast moment sensor package.

[0021] FIG. 9 shows an isometric view of an aspect of the same propeller propulsion system as shown in FIG. 1. The main propeller hub and propeller blades are not shown for clarity. As shown in FIG. 2, the first optical fiber strain sensing cable 107a and the second optical fiber strain sensing cable 107b are fixed 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 since wires can be connected to devices within the aircraft body without using devices such as slip rings.

[0022] The optical fiber strain sensor may include any suitable optical fiber strain sensor including, for example, a fiber Bragg grating (FBG) sensor, an optical time domain reflectometer sensor, etc. The mast moment sensor system provides good mast moment measurements. The fiber Bragg grating (FBG) sensors are sensitive and robust, allowing consistent and accurate measurements.

[0023] The mast moment module 602 can calculate the mast moment load acting on the hub shaft 101 by using the signal from the fiber optic strain sensor. Next, the mast moment can be determined by using the strain information.

[0024] It should be understood that the fiber optic strain sensor may measure strain by using the diffraction grating frequency or the local strain of the fiber optic material. Any language targeted at fiber optic strain sensor modules, mast moment modules, etc. should be read to include any suitable combination of computing devices including servers, interfaces, systems, databases, agents, peers, engines, controllers, or other types of computing devices operating individually or collectively. The computing device may comprise a processor configured to execute software instructions stored on a tangible non-transitory computer-readable storage medium (such as a hard drive, solid state drive, RAM, flash, ROM, etc.). Preferably, the software instructions configure the computing device to provide the roles, responsibilities, or other functionality as described above with respect to the disclosed apparatus. 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 key and private key exchange, web service APIs, known financial transaction protocols, or other methods of electronic information exchange. The data exchange is preferably performed over a packet-switched network, the Internet, a LAN, a WAN, a VPN, or other types of packet-switched networks.

[0025] For convenience, the term prop-rotor is used in this specification. As used in this specification, the term prop-rotor should be understood to include any similar devices such as rotors, prop-rotors, propellers, propulsars, fans, ducted fans, etc.

[0026] Those skilled in the art should recognize that the rotor shaft bearings can be of any suitable type, including bearings such as angular contact bearings, tapered roller bearings, bushings, etc. Further, any number of bearings can be provided.

[0027] While some embodiments of this specification are configured for electric vertical takeoff and landing (eVTOL) aircraft, embodiments of the mast moment sensing system will be equally applicable to any type of aircraft such as helicopters, turbine-driven tiltrotor aircraft, non-tiltrotor type VTOLs, turbine-driven helicopters, etc.

Claims

1. A VTOL aircraft comprising two or more optical fiber strain sensors configured to detect lateral loads on a prop rotor shaft.

2. The VTOL aircraft according to claim 1, wherein the VTOL aircraft comprises a prop rotor shaft bearing.

3. The VTOL aircraft according to claim 2, wherein the VTOL aircraft comprises a bearing sleeve disposed between the prop rotor shaft bearing and the aircraft structure.

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

5. A rotary wing aircraft mast moment sensor system comprising a first rotor shaft bearing optical fiber strain sensor and a second rotor shaft bearing optical fiber strain sensor.

6. The rotary wing aircraft mast moment sensor system according to claim 5, wherein the mast moment sensor system comprises a mast moment module configured to calculate mast moment information from the first rotor shaft bearing optical fiber strain sensor and the second rotor shaft bearing optical fiber strain sensor.

7. A mast moment detection module configured to receive optical fiber strain sensor information corresponding to rotor shaft bearing deformation and calculate the mast moment on the rotor shaft by using the received optical fiber strain sensor information.

8. The mast moment detection module according to claim 7, further configured to perform an additional step of receiving optical fiber strain sensor information from a second optical fiber strain sensor, the second optical fiber strain sensor being configured to detect deformation of a second rotor shaft bearing.

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