System and method for dynamically measuring blade position during flight of a rotary wing aircraft

Abstract

Systems and methods are provided for dynamically measuring blade positions during flight of a rotorcraft. In the context of a method, during flight of a rotorcraft (10), a blade (14) of the rotorcraft (10) is repeatedly illuminated (50) by a light source as the blade (14) rotates. The method also includes detecting radiation scattered from the blade (14) in response to the illumination (50) of the blade (14). The method further includes determining at least one of a blade pitch angle (Δθ P ), a blade flap angle (Δθ F ), a blade lead or a blade lag position based on the radiation scattered from the blade (14) and detected. A rotorcraft (10) is also provided, including a chip-scale light detection and ranging (LIDAR) sensor configured to illuminate (50) a plurality of blades (14) as the blades (14) rotate to allow for measurement of blade (14) positions or to illuminate terrain below the rotorcraft (10) to provide height measurements.

Description

TECHNICAL FIELD

[0001] A system and method for measuring blade position of a rotorcraft is provided, and more particularly, for dynamically measuring blade position during flight of a rotorcraft. BACKGROUND

[0002] Rotorcraft, such as helicopters, include a plurality of blades that rotate to provide lift during flight. In instances where the blades maintain their predetermined blade position, such as with respect to blade pitch angle, blade flap angle, and blade lead or trail position, the rotorcraft generally provides a relatively smooth flight. However, at times, the blade position can change from the desired blade position, such as by having a different blade pitch angle, a different blade flap angle, and / or being positioned in a lead or trail position, among others. In these instances, the flight of the rotorcraft generally becomes less smooth, thereby potentially reducing the flight experience of the crew and any passengers and / or potentially causing problems with cargo being carried by the rotorcraft.

[0003] In these instances where the blade position changes, the blades of the rotorcraft cannot be repositioned to at least again be in the predetermined blade position until the rotorcraft completes its flight. In some instances, even after the flight is completed, the blades of the rotorcraft cannot be repositioned, but must wait for the rotorcraft to return to a maintenance station or other facility where such repairs can be made. Thus, the potentially adverse flight conditions resulting from the change in blade position can not be quickly addressed as needed. SUMMARY

[0004] According to exemplary embodiments, a blade positioning system and method is provided to dynamically measure blade position during flight of a rotorcraft. Based on the dynamically changing blade position, the rotorcraft of exemplary embodiments can be configured to modify the position of the blades during flight of the rotorcraft. Thus, the dynamic measurement of blade position, and, in some embodiments, the in-flight modification of blade position, allows for a more rapid return to more smooth flight conditions, such as during the flight itself, without having to wait for the flight to be completed and / or the rotorcraft to return to a maintenance station or other repair facility. The blade positioning system and method of exemplary embodiments utilizes tracking sensors, such as chip-scale Light Detection and Ranging (LIDAR) sensors, carried by the fuselage of the rotorcraft, thereby not significantly increasing the size and weight of the rotorcraft. Although the chip-scale LIDAR sensors can be utilized to measure blade position, the rotorcraft of another exemplary embodiment can utilize the chip-scale LIDAR sensors as altimeters, for example, to facilitate landing of the rotorcraft, among others.

[0005] In an example embodiment, a method for dynamically measuring blade positions during flight of a rotorcraft is provided. The method includes repeatedly illuminating a blade of the rotorcraft with coherent light during flight of the rotorcraft as the blade rotates. The method also includes detecting radiation scattered from the blade in response to the illumination of the blade. The method further includes determining at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on the radiation scattered from the blade and detected.

[0006] The method of an example embodiment repeatedly illuminates a blade of a rotorcraft at a position closer to a distal end of the blade than to a rotor shaft, the blade rotating about a rotor axis. In an example embodiment, the method repeatedly illuminates the blade with a plurality of tracking sensors positioned at different locations on a fuselage of the rotorcraft.

[0007] In an example embodiment, the method determines a blade pitch angle by determining a distance to the blade based on the radiation scattered from the blade and detected and then determining the blade pitch angle based on a deviation of the distance to the blade from a distance to a reference blade position that is free of pitch. In this example embodiment, in which the blade is repeatedly illuminated by radiation produced by a laser source, the method determines the distance to the blade by determining a distance between the laser source and an edge of the blade.

[0008] In an example embodiment, the method determines a blade flap angle by determining a distance to the blade based on the radiation scattered from the blade and detected and then determining the blade flap angle based on a deviation of the distance to the blade from a distance to a reference blade position that is free of flap. In another example embodiment, the method determines a blade lead position or a blade lag position by detecting a presence of the blade at a predetermined position within a rotational path of the blade and determining a detection time at which the presence of the blade is detected. The method of this example embodiment then determines the blade position based on a relationship of the detection time to a predetermined time associated with a reference blade that is neither leading nor lagging. In this regard, the method determines the blade position by determining a blade lead position in instances in which the detection time precedes the predetermined time and determining a blade lag position in instances in which the detection time follows the predetermined time.

[0009] In another example embodiment, a blade positioning system for dynamically measuring blade position during flight of a rotorcraft is provided. The blade positioning system includes a tracking sensor mounted on the rotorcraft. The tracking sensor includes a laser source configured to repeatedly illuminate a blade of the rotorcraft with coherent light during flight of the rotorcraft as the blade rotates. The tracking sensor also includes at least one photodetector configured to detect radiation scattered from the blade in response to the illumination of the blade. The system of the present example embodiment also includes processing circuitry configured to determine at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on the radiation scattered from the blade and detected by the at least one photodetector in response to the tracking sensor.

[0010] The tracking sensor of the example embodiment is mounted on the rotorcraft such that the light source is configured to repeatedly illuminate the blade at a location closer to a distal end of the blade than to a rotational axis of the rotor. In the example embodiment, the blade positioning system also includes a plurality of tracking sensors mounted at different locations on the rotorcraft.

[0011] The processing circuitry of the example embodiment is configured to determine the blade pitch angle by being configured to determine a distance to the blade based on the radiation scattered from the blade and detected and determine the blade pitch angle based on a width of the blade and a deviation of the distance to the blade from a distance to a reference blade position that is free of pitch. The processing circuitry of the present example embodiment is configured to determine the distance by determining a distance between the laser source and an edge of the blade.

[0012] The processing circuitry of the example embodiment is configured to determine the blade flap angle by being configured to determine a distance to the blade based on the radiation scattered from the blade and detected and determine the blade flap angle based on a length of the blade and a deviation of the distance to the blade from a distance to a reference blade position that is free of flap. In another example embodiment, the tracking sensor is configured to detect a presence of the blade at a predetermined location within a rotational path of the blade and the processing circuitry is configured to determine a detection time at which the presence of the blade is detected. In the present example embodiment, the processing circuitry is configured to determine the blade position based on a relationship of the detection time to a predetermined time associated with a reference blade that is neither leading nor lagging. The processing circuitry of the present example embodiment is configured to determine the blade position by determining a blade lead position in instances in which the detection time is before the predetermined time and determining a blade lag position in instances in which the detection time is after the predetermined time.

[0013] In yet another example implementation, a rotorcraft is provided, comprising: a fuselage; a plurality of blades configured to rotate relative to the fuselage; and a chip-scale light detection and ranging (LIDAR) sensor carried by the fuselage. The chip-scale LIDAR sensor comprises: a laser source configured to provide illumination with coherent light during flight of the rotorcraft; and at least one photodetector configured to detect radiation scattered in response to the illumination provided by the laser source. The chip-scale LIDAR sensor is carried by the fuselage such that the laser source is configured to illuminate the plurality of blades as the blades rotate to allow measurement of blade position or to illuminate terrain below the rotorcraft to provide a height measurement.

[0014] The laser source of the example implementation comprises a frequency- modulated continuous wave laser diode. The at least one photodetector of the example implementation comprises a pair of dual balanced photodetectors. The chip-scale LIDAR sensor of the example implementation further comprises an optical splitter configured to split light generated by the laser source into a first portion and a second portion, and the first portion is directed to illuminate the plurality of blades or to illuminate terrain below the rotorcraft as the blades rotate. The chip-scale LIDAR sensor of the present example implementation further comprises: a waveguide configured to support propagation of the second portion of the light generated by the laser source; and a coupler configured to couple the second portion of the light propagating along the waveguide with the radiation scattered in response to the illumination provided by the laser source. The at least one photodetector of the example implementation is responsive to the coupler and is configured to receive the second portion of the light propagating along the waveguide and the radiation scattered in response to the illumination provided by the laser source.

[0015] The rotorcraft of the present example implementation further comprises processing circuitry configured to determine, responsive to the chip-scale LIDAR sensor, at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from a respective blade of the plurality of blades and detected by the at least one photodetector. The rotorcraft of the present implementation further comprises an actuator configured to alter, responsive to the processing circuitry, a position of the respective blade during flight based on at least one of the blade pitch angle, the blade flap angle, the blade lead position, or the blade lag position determined by the processing circuitry. BRIEF DESCRIPTION OF DRAWINGS

[0016] Having generally described certain embodiments of the present disclosure, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0017] Figure 1is an isometric view of a rotorcraft having tracking sensors such as chip-scale Light Detection and Ranging (LIDAR) sensors carried by a fuselage of the rotorcraft and configured to repeatedly illuminate blades of the rotorcraft during flight, in accordance with example implementations of the present disclosure;

[0018] Figure 2 is a schematic representation of a chip-scale LIDAR sensor, in accordance with example implementations of the present disclosure;

[0019] Figure 3 is a block diagram of a blade positioning system including tracking sensors such as chip-scale LIDAR sensors, in accordance with example implementations of the present disclosure;

[0020] Figure 4 is a flowchart showing operations performed by a blade positioning system such as Figure 3 in accordance with example implementations of the present disclosure;

[0021] Figure 5 is a top view of a plurality of blades of a rotorcraft and a rotational path of the blades relative to a plurality of tracking sensors carried by the rotorcraft, in accordance with example implementations of the present disclosure;

[0022] Figure 6 is a side view of a distal portion of a blade of a rotorcraft describing a relative position of a tracking sensor relative to the blade, in accordance with example implementations of the present disclosure;

[0023] Figure 7 is another side view of a portion of a blade along a transverse cross-section of line 7-7 in Figure 5 describing a determination of a blade pitch angle, in accordance with example implementations of the present disclosure;

[0024] Figure 8 is a flowchart showing operations performed to determine a blade pitch angle, in accordance with example implementations of the present disclosure;

[0025] Figure 9 is another side view of a blade along a longitudinal cross-section of line 9-9 in Figure 5 describing a determination of a blade flap angle, in accordance with example implementations of the present disclosure;

[0026] Figure 10 is a flowchart showing operations performed to determine a blade flap angle, in accordance with example implementations of the present disclosure;

[0027] Figure 11 is a flowchart showing operations performed to determine a blade position with respect to being ahead of or behind, in accordance with example implementations of the present disclosure; and

[0028] Figure 12 This is a perspective view of a rotorcraft according to another exemplary embodiment of the present disclosure, the rotorcraft having a chip-scale LIDAR sensor mounted to the lower surface of the fuselage to provide altitude measurement. Detailed Implementation

[0029] Some embodiments of the present disclosure will now be described more fully with reference to the accompanying drawings, which illustrate some, but not all, embodiments of the present disclosure. In fact, the present disclosure may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the present disclosure to meet practical legal requirements. Similar reference numerals always refer to similar elements. As used herein, the terms “data,” “content,” “information,” and similar terms are used interchangeably to refer to data that can be transmitted, received, and / or stored according to embodiments of the present disclosure. Therefore, the use of any such terms should not be construed as limiting the spirit and scope of the present disclosure.

[0030] According to an exemplary embodiment, a system and method are provided for dynamically measuring the blade position during flight of a rotorcraft. By measuring the blade position during flight, the rotorcraft of the exemplary embodiment can be configured to change the blade position during flight, thereby providing improved flight performance, such as smoother flight, without waiting for the flight to complete and / or for the rotorcraft to return to a maintenance station or be equipped with other facilities for repositioning the blades.

[0031] Various types of rotorcraft can benefit from dynamic measurements of blade position during flight. For example, but not limited to, Figure 1 A helicopter-type rotorcraft 10, referenced throughout, is described to illustrate a system and method for dynamically measuring blade position according to an exemplary embodiment. As shown, the rotorcraft 10 includes a fuselage 12 and a plurality of blades 14 configured to rotate relative to the fuselage. In this exemplary embodiment, the rotorcraft 10 includes a rotor shaft 16, the blades 14 being operatively connected to the rotor shaft 16 and configured to rotate about the rotor shaft 16. Figure 1 In the exemplary embodiment described, the rotorcraft 10 also includes a tracking sensor 20 mounted on the rotorcraft, and more specifically, on the upper surface 13 of the fuselage 12. In this respect, the tracking sensor 20 is mounted on this portion of the upper surface 13 of the fuselage 12, i.e., within the path of rotation of the blade 14, such that the blade passes over the tracking sensor during the rotation of the blade, such as during flight.

[0032] While the tracking sensor 20 can be configured in various ways, the tracking sensor of the example embodiment is a chip-scale Light Detection and Ranging (LIDAR) sensor. The chip-scale LIDAR sensor can be implemented through an integrated circuit package and, thus, can result in a slight increase in weight and size of the rotorcraft 10 in which the chip-scale LIDAR sensor is installed. While the chip-scale LIDAR sensor can be configured in various ways, as shown in FIG. 1, the chip-scale LIDAR sensor 21 of the example embodiment includes a laser source 22 configured to generate radiation (e.g., coherent light) that is directed to illuminate one or more blades 14 of the rotorcraft 10. In the example embodiment, the laser source 22 is a laser diode. The laser diode can be a single-spectral mode laser diode. In one embodiment, the laser diode is a Distributed Bragg Reflector (DBR) laser diode or a Distributed Feedback (DFB) laser diode heterogeneously integrated on a base substrate. In the example embodiment, the laser diode is a frequency-modulated continuous wave (FMCW) laser diode capable of FMCW LIDAR operation. Figure 2

[0033] Figure 2 The chip-scale LIDAR sensor 21 of the example embodiment further includes at least one photodetector and, in the example embodiment, a pair of photodetectors 26a, 26b (hereinafter referred to as photodetectors 26) in a dual-balanced configuration. Each of the one or more photodetectors 26 of the example embodiment is a (PIN) photodiode. In embodiments such as where the photodetector is a germanium-on-silicon (Ge-on-Si) photodiode, the photodetectors 26 can be monolithically integrated or heterogeneously integrated on two additional grating couplers that perpendicularly couple the photodetectors to the base waveguide. To illuminate the blades 14 of the rotorcraft 10 during flight, the chip-scale LIDAR sensor 21 of the illustrated embodiment includes an output coupler 28 (also referred to herein as an output coupler) such as a transmissive beam grating output coupler that receives the radiation generated by the laser source 22 and directs the light toward the blades 14 of the rotorcraft 10. The light directed by the output coupler 28 toward the blades 14 of the rotorcraft 10 can be collimated, such as through an off-chip collimating lens.

[0034] ​In the illustrated embodiment, not all of the radiation produced by the laser source 22 is used to illuminate the blades 14 of the rotorcraft 10. Rather, the chip-scale LIDAR sensor 21 includes a beamsplitter 30, such as a lx2 beamsplitter, configured to receive the radiation produced by the laser source 22 and split the radiation into a first portion 31a and a second portion 31b, the first portion 31a being directed and used to illuminate the blades 14 of the rotorcraft 10 via, for example, the output coupler 28, and the second portion 31b being directed toward the at least one photodetector 26a and / or 26b. While the beamsplitter 30 can be configured to split the radiation produced by the laser source 22 into the first portion 31a and the second portion 31b in various proportions, the beamsplitter of the example embodiment splits the radiation produced by the laser source such that the first portion illuminating the blades 14 is greater, such as in intensity, than the second portion directed toward the at least one photodetector 26. For example, the beamsplitter 30 can be configured such that the first portion 31a includes 75% to 95% of the radiation produced by the laser source 22 and, in one embodiment, 90% to 95% of the radiation produced by the laser source, and such that the second portion 31b includes the remaining portion of the radiation, such as 25% to 5% of the radiation produced by the laser source, and, in one embodiment, 10% to 5% of the radiation produced by the laser source. In the example embodiment, the beamsplitter 30 can be a directional coupler / beamsplitter or a multimode interference (MMI) coupler beamsplitter. The second portion 31b of the radiation can be used as a local oscillator (LO) beam.

[0035] In the illustrated embodiment, the chip-scale LIDAR sensor 21 also includes an input coupler 32, such as a receive-beam input coupler, also referred to herein as an input coupler. In operation, the input coupler 32 is configured to receive radiation scattered from the blades 14 in response to illumination by the light produced by the laser source 22 and then direct the received radiation to the at least one photodetector 26a and / or 26b. In the illustrated embodiment, the input coupler 32 directs the received radiation to each of the pair of dual balanced photodetectors 26a and / or 26b. In the illustrated embodiment, the chip-scale LIDAR sensor 21 also includes a coupler 34, such as a 2x2 coupler, i.e., a 50:50 2x2 coupler. In operation, the coupler 34 is configured to optically combine, e.g., mix, the radiation received by the input coupler 32, such as the radiation scattered from the blades 14, with the second portion 31b of the radiation produced by the laser source 22, i.e., the LO beam, and split the combination evenly to each of the photodetectors 26a and 26b. The coupler 34 of the example embodiment can be a directional or MMI coupler. In the illustrated embodiment, the coupler 34 provides the combined radiation to the pair of dual balanced photodetectors 26a and 26b.

[0036] As Figure 2 The various components of the chip-scale LIDAR sensor 21 can be connected by a network of waveguides 36, such as a network of integrated photonic waveguides, for example, silicon-based waveguides, as shown in FIG. 2. In the illustrated embodiment, the network of waveguides includes a first waveguide 36a configured to direct the radiation generated by the laser source 22 to the optical splitter 30, a second waveguide 36b configured to direct the second portion 31b of the radiation from the optical splitter to the coupler 34, and a third waveguide 36c configured to direct the first portion 31a of the radiation from the optical splitter to the output coupler 28. The network of waveguides of the illustrated embodiment can also include a fourth waveguide 36d configured to direct the received radiation from the input coupler 32 to the coupler 34, and fifth and sixth waveguides 36e and 36f configured to direct portions of the received radiation from the coupler to the pair of dual balanced photodetectors 26a and 26b, respectively. The waveguides 36 can be integrated with the substrate and exhibit relatively low losses, such as less than 4 dB / cm. In view of this, the light generated by the laser source 22 can be coupled to the first waveguide 26a by a spatial mode converter 24 that matches the larger optical spatial mode of the laser source 22 to the smaller mode of the first waveguide.

[0037] As Figure 3 As shown in the example embodiment described in FIG. 3, the tracking sensor 20, such as the chip-scale LIDAR sensor 21, is a component of a blade positioning system 40 that also includes a processing circuit 42. In operation, the blade positioning system 40 is configured to dynamically measure blade position during flight of the rotorcraft 10. In some embodiments, the blade positioning system 40 is also configured to reposition the blade 14 based on the dynamic measurement of blade position during flight of the rotorcraft 10.

[0038] The processing circuit 42 of the blade positioning system 40 is responsive to the tracking sensor 20, such as signals captured by at least one photodetector 26 of the chip-scale LIDAR sensor 21, to determine blade position and / or altitude of the rotorcraft 10. The processing circuit 42 can be implemented in a variety of different forms and can include, for example, one or more processing devices configured to execute independently. Additionally or alternatively, the processing circuit 42 can include one or more processors configured in tandem via a bus to enable independent execution of software instructions, pipelining, and / or multithreading. The use of the term “processor” or “processing circuit” should be understood to include a single core processor, a multi-core processor, multiple processors, remote or “cloud” processors, or any combination thereof.

[0039] In embodiments, processing circuitry 42 may include one or more dedicated processors, controllers, specially configured field-programmable gate arrays (FPGAs), or application-specific integrated circuits (ASICs) performing its corresponding functions. Alternatively, processing circuitry 42 may be implemented using a processor that executes software stored in a storage device. Thus, processing circuitry 42 can be implemented using dedicated components implemented purely through hardware design, or processing circuitry 42 can utilize hardware components that execute computer software designed to facilitate the execution of the functions of processing circuitry.

[0040] The processing circuitry 42 may also include or be associated with a storage device, and the processing circuitry of this embodiment may be configured to execute software instructions stored in the storage device or otherwise access the processing circuitry. In this embodiment, the storage device may be configured to store information, data, content, applications, software instructions, etc., that enable the processing circuitry 42 to perform various functions according to the embodiments contemplated herein. Alternatively or additionally, the processing circuitry 42 may be configured to perform hard-coded functions. Thus, whether configured by hardware or software methods, or by a combination of hardware and software, the processing circuitry 42 may represent an entity (e.g., physically implemented circuitry) capable of performing operations according to embodiments of this disclosure when thus configured. Alternatively, as another embodiment, when the processing circuitry 42 is implemented as an executor of software instructions, the software instructions may specifically configure the circuitry to perform the algorithms and / or operations described herein when executing the software instructions.

[0041] Figure 4 The description includes examples of embodiments of the invention, such as those described above. Figure 3 The blade positioning system 40 performs operations to dynamically measure the blade position during flight of the rotorcraft 10. For example... Figure 4 As shown in box 50, during the flight of the rotorcraft, the rotor blades 14 of the rotorcraft 10 are repeatedly irradiated as the blades rotate. Therefore, the laser source 22 of the tracking sensor 20 is configured to generate radiation, such as light, that repeatedly irradiates the rotating rotor blades 14 of the rotorcraft 10. Figure 1 As shown, for example, the tracking sensor 20 is preferably mounted on the upper surface 13 of the fuselage 12 of the rotorcraft, positioned below the path of rotation of the plurality of blades 14, such that the blades extend radially beyond the tracking sensor and pass over it during rotation. As illustrated by... Figure 1 As shown by the dashed line in the figure, the tracking sensor 20 of this exemplary embodiment is positioned such that the radiation generated by the laser source 22 is directed upward toward the plurality of blades 14, which pass over the tracking sensor as the blades rotate.

[0042] The tracking sensor 20, such as the laser source 22, can be configured to illuminate the blade 14 by reflecting radiation, such as periodically producing pulses of radiation (e.g., laser pulses), during rotation of the blade. Depending on the frequency of the pulses produced, the tracking sensor 20 can be configured to illuminate the blade 14 multiple times during a single pass of the blade through the tracking sensor. Alternatively, the tracking sensor 20 can be configured to illuminate the blade 14 during each revolution of the blade through the tracking sensor. In any instance, the tracking sensor 20 is configured to repeatedly illuminate the blade 14 as the blade 14 rotates.

[0043] As shown in block 52 in Figure 4 The radiation scattered from the blade 14 in response to illumination of the blade by the laser source 22 is detected by the at least one photodetector 26. As shown in Figure 6 Preferably, the radiation produced by the laser source 22 can illuminate the underside of the blade 14 facing the fuselage 12 of the rotorcraft 10. The radiation scattered from the blade 14 in response to the illumination is then detected by the at least one photodetector 26.

[0044] Although the blade positioning system 40 has been described as including a single tracking sensor 20, the blade positioning system of the example embodiment can include multiple tracking sensors 20a, 20b, and 20c, each of which is configured to individually illuminate the blade 14 and receive radiation scattered from the blade in response to the illumination. Although the multiple tracking sensors 20 can be mounted on the fuselage 12 of the rotorcraft 10 in various ways, in the example embodiment, Figure 5 A plurality of tracking sensors, including a first tracking sensor 20a depicted in solid lines, and a plurality of additional tracking sensors 20b and 20c depicted in dashed lines and angularly and / or radially offset from the first tracking sensor are described. By individually determining the blade position based on radiation scattered from the blade 14 and detected by the plurality of tracking sensors 20, the accuracy of determining the blade position can be improved based on a combination (e.g., averaging) of the blade positions determined by each of the plurality of tracking sensors. In addition, the integration of the plurality of tracking sensors 20 increases redundancy and, in turn, the reliability of the blade positioning system 40.

[0045] As shown in Figure 6 According to the example embodiment, the blade 14 is repeatedly illuminated at a location 19 closer to the distal end 18 of the blade than to the rotor shaft 16 as the blade rotates about the rotor shaft 16. In view of this, the tracking sensor 20 can be mounted on the fuselage 12 to be located below the path of rotation of the blade 14, but at a location closer to the periphery or circumference of the path of rotation than to the rotor shaft 16 (as depicted by the dashed line in Figure 5The position 19 at which the blade 14 is illuminated can be spaced apart from the distal end 18 of the blade by a distance dl and can be spaced apart from the rotor axis of rotation 16 by a distance d2. Because the position 19 at which the blade 14 is illuminated is closer to the distal end 18 of the blade than the rotor axis of rotation 16, the distance dl is less than the distance d2. By repeatedly illuminating the blade 14 at a position closer to the distal end 19 of the blade than the rotor axis of rotation 16, the method and the blade positioning system 40 of the example embodiment can more precisely and accurately determine the blade position because at least some of the variations in the blade position are more apparent closer to the distal end of the blade than closer to the rotor axis of rotation.

[0046] As Figure 4 As shown at block 54 in FIG. 54, at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position is determined, such as by the processing circuitry 42, based on radiation scattered from the blade 14 and detected, such as by the at least one photodetector 26 of the tracking sensor 20. As described below, the blade pitch angle and the blade flap angle are determined based at least in part on a distance to the blade 14. The distance to the blade 14 defines a distance between the chip-scale LIDAR sensor 21 and a portion of the blade 14 that is illuminated. In view of this, the distance can define a distance between the chip-scale LIDAR sensor 21 and the portion of the blade 14 that is illuminated or a round trip distance traveled by the radiation between the chip-scale LIDAR sensor 21 and the portion of the blade 14 that is illuminated. As described below, the blade lead position and the blade lag position are determined based at least in part on a distance to the blade 14 and a distance to a reference blade position that is not pitched. Figure 7 and Figure 8 As shown at block 60 in FIG. 60, the processing circuitry 42 is configured to determine a distance to the blade 14 based on radiation generated by the laser source 22 and scattered from the blade and then in turn detected by the at least one photodetector 26. For example, based on an optical frequency shift between transmission of the radiation generated by the FMCW laser source 22 and detection of the scattered radiation based thereon, the processing circuitry 42 is configured to determine the distance to the blade 14.

[0047] For the blade pitch angle, the processing circuitry 42 of the present example embodiment is further configured to determine the blade pitch angle based on a width W B of the blade 14 and a deviation of the distance to the blade from a distance to a reference blade position that is not pitched, such as Figure 7 The position of the blade that is laid along the horizontal axis 56 in the example embodiment of FIG. 54. See Figure 8width of the blade 14 can be predetermined, and in some embodiments, the distance from the non-pitching reference blade position can also be predetermined. However, in other embodiments, the distance from the non-pitching reference blade position can be defined by the distance from the blade 14 at the blade center axis 14a, i.e., the blade center axis 14a is an axis that extends radially outward from the rotor axis of rotation 16 to the distal end 18 of the blade and is located at the center of the blade in the width direction. Thus, the tracking sensor 20 of the example embodiment can be configured to repeatedly illuminate the blade 14, including illuminating the blade at the blade center axis 14a and illuminating the blade at another location that is laterally offset from the blade center axis. As Figure 7 As shown in the present example embodiment, the tracking sensor 20 can be configured to illuminate the blade 14 at the lateral edge 14b of the blade, such that the determination of the distance and thus the determination of the deviation of the distance can be based on the distance at the lateral edge of the blade.

[0048] In Figure 7 In the described example embodiment, the processing circuit 42 is configured to determine the blade pitch angle Δθ P based on the following relationship:

[0049]

[0050] where W B is the width of the blade 14, and ΔR P is the deviation of the distance from the blade relative to the distance from the non-pitching reference blade position (i.e., R P ).

[0051] In an example, the width of the blade 14 is 533 millimeters and the blade pitch angle is expected to change within a range of +6 degrees to -6 degrees from a position in which the blade is flat (within a total angular range of 12 degrees of potential blade pitch angle). In an embodiment in which the blade pitch angle resolution is 0.1 degrees for a total of 120 resolved blade pitch angle positions, the resolution of the determination of the distance deviation is 0.5 millimeters. In terms of the determination of the deviation of the distance ΔR P , this resolution in turn depends on the range of the optical frequency modulation Af and is defined as follows:

[0052]

[0053] where c is the speed of light. Thus, in the present example embodiment, the tracking sensor 20 is configured to provide an optical frequency modulation of at least about 300 GHz of the ramp waveform.

[0054] With regard to the determination of the blade pitch angle, reference is made to Figure 9 and Figure 10at block 70 in FIG. 6, the processing circuit 42 is configured to determine a distance to the blade 14 based on the radiation scattered from the blade and detected, such as described above in connection with the determination of the blade pitch angle. The processing circuit 42 of the present example embodiment is further configured to determine a blade flap angle based on a length of the blade 14 and a deviation of the distance to the blade from the distance to the reference blade position without flap, such as Figure 9 the position of the blade without flap along the horizontal axis 90 in the example embodiment of FIG. 7. Reference is made to Figure 10 block 72 in FIG. 6. In instances in which the blade position is confirmed to be without flap, the distance to the reference blade position without flap can be predetermined or can be determined by the tracking sensor 20 and the processing circuit 42. In the example embodiment, the processing circuit 42 is configured to determine the blade flap angle ΔΘ based on the equation F :

[0055]

[0056] where L B is the length of the blade 14, such as the length from the rotor shaft 16 to the distal end 18 of the blade, and ΔR F is the deviation of the distance to the blade from the distance to the reference blade position without pitch, i.e., R F . The length of the blade 14 can be predetermined.

[0057] In the example embodiment in which the length of the blade is 7468 millimeters, the blade flap angle is expected to change from +1 degree to -1 degree from the position in which the blade is flat (a total of 2 degrees of blade flap angle). In the present example embodiment, the blade positioning system 40 and method can be configured to determine the blade flap angle with a resolution of 0.1 degrees, such as for a total of 20 resolved blade flap angle positions. In the present example embodiment, the processing circuit 42 is configured to determine the distance to the blade 14 with a resolution of approximately 6.5 millimeters, such that the laser source 22 of the tracking sensor 20 of the present example embodiment provides a slope waveform with an optical frequency modulation of approximately 23 Hz.

[0058] In another example embodiment, the processing circuit 42 is configured to determine a blade position, such as a blade lead position or a blade lag position, by determining the presence of the blade 14 at a predetermined position, i.e., a predetermined angular position, within the rotational path of the blade and determining a detection time at which the presence of the blade is detected. Reference is made to Figure 11Boxes 80 and 82 are referenced. The blade lead position and blade lag position are relative to the blades 14 appropriately angularly positioned relative to the rotor shaft 16. A blade 14 in the blade lead position is angularly advanced in the rotational direction, while a blade in the blade lag position is angularly retarded in the rotational direction. In an example where the blades are spaced 120° apart, for a rotorcraft 10 with three blades 14, the blades can be appropriately angularly positioned. In this embodiment, in an example where the angle defined between a blade and the blade appropriately positioned in the forward direction of rotation is less than 120°, the blade 14 has a blade lead position. Conversely, in an example where the angle defined between a blade and the blade appropriately positioned in the rearward direction of rotation is less than 120°, the blade has a blade lag position.

[0059] Furthermore, the presence of the blades 14 is defined by the detection of radiation scattered by the blades by the chip-level LiDAR sensor 21. Accordingly, multiple blades 14 rotate above the chip-level LiDAR sensor 21. For each corresponding blade 14, the radiation generated by the chip-level LiDAR sensor 21 is generally not incident on the corresponding blade and is not scattered by the corresponding blade, since the corresponding blade is not positioned above the chip-level LiDAR sensor and is therefore not irradiated by the generated radiation. However, for a portion of the time required for a blade 14 to complete a single rotation around the rotor shaft 16, the corresponding blade will be positioned above the chip-level LiDAR sensor 21 and irradiated by the radiation generated by the chip-level LiDAR sensor, causing the radiation generated by the chip-level LiDAR sensor to be scattered. Once radiation scattered by the corresponding blade 14 is detected, the chip-level LiDAR sensor 21 will detect the presence of the corresponding blade. Therefore, the processing circuit 42 can be configured to identify the time at which the leading edge (or lagging edge) of the blade 14 is detected based on the scattered radiation detected by the tracking sensor 20, thereby determining the time for detecting the corresponding edge of the blade. For a properly positioned blade 14 that is neither leading nor lagging, the time for detecting the blade by the tracking sensor 20 can be predetermined, such as based on the blade's rotational speed and initial position.

[0060] In this exemplary embodiment, the processing circuit 42 is configured to determine the blade position based on the relationship between the detection time and a predetermined time, detecting a properly positioned blade that is neither ahead nor behind at the predetermined time. (See reference...) Figure 11Box 84 in the diagram. Therefore, in instances where the detection time is before a predetermined time, i.e., before the time the blade positioning system 40 expects to detect the presence of a properly positioned blade, the processing circuit 42 is configured to determine the blade position by determining that blade 14 is ahead. The processing circuit 42 of this exemplary embodiment is also configured to determine that blade 14 is lagging in instances where the detection time is after a predetermined time, such as in instances where the blade positioning system 40 detects the presence of a blade after a predetermined time, where the blade positioning system expects to detect the presence of a properly positioned blade at the predetermined time. Based on the difference between the detection time and the predetermined time, the blade positioning system 40 is not only configured to determine whether blade 14 is ahead or lagging, but also to determine the angle by which the blade is ahead or lagging based on the blade's rotational speed and the difference between the detection time and the predetermined time.

[0061] like Figure 3 As shown, the blade positioning system 40 of the exemplary embodiment also includes one or more actuators 44. In this exemplary embodiment, the one or more actuators respond to the processing circuit 42 and are configured to change the position of the blade 14 during flight based on a determined blade position. For example, the blade positioning system 40 may include a blade pitch actuator 44a configured to change the blade pitch based on a determined blade pitch angle, so that the blade 14 can return to a level position during flight. Similarly, the blade positioning system 40 may include a blade flap actuator 44b configured to change the blade flapping based on a determined blade flapping angle, so that the blade 14 can return to a level position during flight. Furthermore, the blade positioning system 40 may include a blade angle position actuator 44c configured to change the blade position, such as the blade angle position, based on a determination of whether the blade 14 is leading or lagging, so that the blade can return to a desired angle position that is neither leading nor lagging. Thus, the blade positioning system 40 (e.g., at least one actuator 44) is configured to controllably change the position of the blade 14 during flight to counteract any changes in the blade position and return the blade to the desired position, thereby improving flight conditions by making the flight smoother, without waiting for the flight to complete and / or for the rotorcraft to return to a maintenance station or other facilities where necessary repairs can be performed.

[0062] The blade 14 is irradiated by radiation generated by laser source 22 and has a limited residence time T. B The dwell time depends on the blade rotation speed υ R The position of the tracking sensor 20 relative to the axis of rotation of the blade, such as that defined with respect to the radius R from the axis of rotation of the blade to the tracking sensor, is defined as follows:

[0063]

[0064] where v R is the paddle rotational speed.

[0065] For embodiments of the paddle 14 having the above dimensions, in instances where the tracking sensor is positioned closer to the distal end 18 of the paddle than the rotor axis of rotation 16, for paddles having a rotational speed of 258 revolutions per minute (RPM), the minimum dwell time of the radiation produced by the tracking sensor 20 on the paddle 14 is approximately 5 milliseconds. In implementations where the beam size of the radiation produced by the laser source 22 of the tracking sensor 20 is approximately 3 millimeters, the spot size of the radiation on the paddle 14 spaced 3 meters from the tracking sensor is approximately 7 millimeters. In the present exemplary implementation, for each measurement, the single tracking sensor 20 produces approximately 78 measurement points across the width of the paddle 14 in a single rotation with a measurement time (or integration time) of approximately 64 milliseconds. Figure 5 Two of which are described in points 15). In view of this, the measurement time is the time during which the paddle 14 is illuminated by the radiation that is scattered from the paddle and is subsequently detected by the at least one photodetector 26 of the tracking sensor 20. In implementations where it is desirable to measure the distance with increased accuracy or resolution, the measurement time (i.e., integration time) is increased for each measurement point, thereby decreasing the number of measurement points across the width of the paddle 14. For example, if the measurement time (i.e., integration time) is increased to approximately 5 milliseconds, the tracking sensor 20 can be configured to produce 5 measurement points across the width of the paddle 14.

[0066] As described above, the chip-level LIDAR sensor 21 can be utilized to determine the paddle position, thereby allowing the paddle position to be altered in a controlled manner during flight. Alternatively, the chip-level LIDAR sensor 21 can be used as or in conjunction with an altimeter to determine the height of the rotorcraft 10 above the ground, such as during a landing of the rotorcraft. In the present exemplary implementation and as described in points 100, the altimeter 100 including the chip-level LIDAR sensor 21 can be mounted on the lower surface 102 of the fuselage 12 of the rotorcraft 10 and configured to illuminate the ground 104 below the rotorcraft, such as the terrain on which the rotorcraft plans to land, etc., as indicated by the downwardly diverging dashed lines. Based on the optical frequency shift between the radiation produced by the laser source 22 of the chip-level LIDAR sensor 21 and the radiation scattered by the terrain below that is detected by the at least one photodetector 26 in response to the illumination of the radiation, the distance to the terrain below, such as the height of the rotorcraft 10, etc., can be determined by, for example, the processing circuit 42. Accordingly, the rotorcraft 10 can be operated in a controlled manner with respect to the terrain below, such as by landing the rotorcraft on the terrain, etc. Figure 12 As described above, the chip-level LIDAR sensor 21 can be utilized to determine the paddle position, thereby allowing the paddle position to be altered in a controlled manner during flight. Alternatively, the chip-level LIDAR sensor 21 can be used as or in conjunction with an altimeter to determine the height of the rotorcraft 10 above the ground, such as during a landing of the rotorcraft. In the present exemplary implementation and as described in points 100, the altimeter 100 including the chip-level LIDAR sensor 21 can be mounted on the lower surface 102 of the fuselage 12 of the rotorcraft 10 and configured to illuminate the ground 104 below the rotorcraft, such as the terrain on which the rotorcraft plans to land, etc., as indicated by the downwardly diverging dashed lines. Based on the optical frequency shift between the radiation produced by the laser source 22 of the chip-level LIDAR sensor 21 and the radiation scattered by the terrain below that is detected by the at least one photodetector 26 in response to the illumination of the radiation, the distance to the terrain below, such as the height of the rotorcraft 10, etc., can be determined by, for example, the processing circuit 42. Accordingly, the rotorcraft 10 can be operated in a controlled manner with respect to the terrain below, such as by landing the rotorcraft on the terrain, etc.

[0067] Figure 4 、 Figure 8 、 Figure 10 、 and Figure 11 Flow diagrams illustrating the operations of apparatuses, methods, and computer program products, in accordance with embodiments of the disclosure, are shown. It should be understood that each block of the flow diagrams, and combinations of blocks in the flow diagrams, can be implemented by various means, such as hardware, firmware, circuitry, and / or other device associated with execution of software including one or more software instructions. For example, one or more of the operations described above can be implemented by software instructions. In this regard, the software instructions which embody the processes described above can be stored on a memory of the blade positioning system 40 employing embodiments of the present disclosure and executed by processing circuitry 42 of a computing device. As will be appreciated, any such software instructions can be loaded into a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus implements the functions specified in the flow diagrams. These software instructions can also be stored in a computer-readable memory that, when used by the computer or other programmable apparatus, causes the computer or other programmable apparatus to perform a series of operations to implement the functions specified in the flow diagrams. The software instructions can also be loaded into a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to implement a computer implemented process such that the software instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flow diagrams.

[0068] The flow diagrams support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will be understood that one or more of the blocks of the flow diagrams, and combinations of blocks in the flow diagrams, can be implemented by special purpose hardware-based computer systems which perform the specified functions or combinations of special purpose hardware and software instructions.

[0069] In some embodiments, some of the operations described above can be modified or further amplified. Furthermore, in some embodiments, additional optional operations can be included. Modifications, amplifications, or additions to the operations described above can be performed in any order and in any combination.

[0070] Further, the present disclosure includes implementations in accordance with the following items:

[0071] Item 1. A method for dynamically measuring blade position during flight of a rotorcraft, the method comprising:

[0072] irradiating a blade of the rotorcraft with coherent light repeatedly as the blade rotates;

[0073] detecting radiation scattered from the paddle in response to the illumination of the paddle; and

[0074] determining at least one of a paddle pitch angle, a paddle flap angle, a paddle lead position, or a paddle lag position based on the radiation scattered from the paddle and detected.

[0075] Item 2. The method of item 1, wherein repeatedly illuminating the paddle of the rotary-wing aircraft comprises repeatedly illuminating the paddle at a location closer to a distal end of the paddle than to an axis of rotation of the rotor, the paddle rotating about the axis of rotation of the rotor.

[0076] Item 3. The method of item 1, wherein repeatedly illuminating the paddle of the rotary-wing aircraft comprises repeatedly illuminating the paddle with a plurality of tracking sensors positioned at different locations on a fuselage of the rotary-wing aircraft.

[0077] Item 4. The method of item 1, wherein determining the paddle pitch angle comprises:

[0078] determining a distance to the paddle based on the radiation scattered from the paddle and detected; and

[0079] determining the paddle pitch angle based on a width of the paddle and a deviation of the distance to the paddle from a distance to a reference paddle position without pitch.

[0080] Item 5. The method of item 4, wherein repeatedly illuminating the paddle comprises repeatedly illuminating the paddle with radiation produced by a laser source, and wherein determining the distance comprises determining a distance between the laser source and an edge of the paddle.

[0081] Item 6. The method of item 1, wherein determining the paddle flap angle comprises:

[0082] determining a distance to the paddle based on the radiation scattered from the paddle and detected; and

[0083] determining the paddle flap angle based on a length of the paddle and a deviation of the distance to the paddle from a distance to a reference paddle position without flap.

[0084] Item 7. The method of item 1, wherein determining the paddle lead position or the paddle lag position comprises:

[0085] detecting a presence of the paddle at a predetermined location within a rotational path of the paddle;

[0086] determining a detection time at which the presence of the paddle is detected; and

[0087] determining the blade position based on a relationship of the detected time to a predetermined time associated with a reference blade that is neither leading nor lagging, wherein determining the blade position comprises: in instances in which the detected time is before the predetermined time, determining that the blade is leading, and in instances in which the detected time is after the predetermined time, determining that the blade is lagging.

[0088] Item 8. A blade positioning system for dynamically measuring blade position during flight of a rotorcraft, the blade positioning system comprising:

[0089] a tracking sensor mounted on the rotorcraft, the tracking sensor comprising:

[0090] a laser source configured to repeatedly illuminate a blade of the rotorcraft with coherent light as the blade rotates during flight of the rotorcraft; and

[0091] at least one photodetector configured to detect radiation scattered from the blade in response to the illumination of the blade; and

[0092] processing circuitry configured to determine at least one of a blade pitch angle, a blade flap angle, a blade leading position, or a blade lagging position based on the radiation scattered from the blade and detected by the at least one photodetector in response to the tracking sensor.

[0093] Item 9. The blade positioning system of item 8, wherein the tracking sensor is mounted on the rotorcraft such that the laser source is configured to repeatedly illuminate the blade at a location closer to a distal end of the blade than to a rotor shaft.

[0094] Item 10. The blade positioning system of item 8, further comprising a plurality of tracking sensors mounted on the rotorcraft at different locations.

[0095] 11. The blade positioning system of item 8, wherein the processing circuitry configured to determine the blade pitch angle comprises processing circuitry configured to determine:

[0096] a distance to the blade based on the radiation scattered from the blade and detected; and

[0097] the blade pitch angle based on a deviation of the distance to the blade from a distance to a reference blade position that is not pitched relative to the width of the blade.

[0098] Item 12. The blade positioning system of item 11, wherein the processing circuitry configured to determine the distance comprises processing circuitry configured to determine a distance between the laser source and an edge of the blade.

[0099] Item 13. The blade positioning system of item 8, wherein the processing circuitry configured to determine a blade flap angle comprises processing circuitry configured to determine:

[0100] a distance from the blade based on radiation scattered from the blade and detected; and

[0101] the blade flap angle based on a length of the blade and a deviation of the distance from the blade relative to a distance from a reference blade position without flap.

[0102] Item 14. The blade positioning system of item 8, wherein the tracking sensor is configured to detect a presence of the blade at a predetermined location within a rotational path of the blade, and wherein the processing circuitry configured to determine a blade lead position or a blade lag position comprises processing circuitry configured to determine:

[0103] a detection time at which the presence of the blade is detected; and

[0104] the blade position based on a relationship of the detection time to a predetermined time associated with a reference blade that is neither leading nor lagging, wherein the processing circuitry configured to determine the blade position comprises processing circuitry configured to determine a blade lead position in instances in which the detection time is prior to the predetermined time, and to determine a blade lag position in instances in which the detection time is subsequent to the predetermined time.

[0105] Item 15. A rotorcraft comprising:

[0106] a fuselage;

[0107] a plurality of blades configured to rotate relative to the fuselage; and

[0108] a chip-scale light detection and ranging (LIDAR) sensor carried by the fuselage and comprising:

[0109] a laser source configured to provide illumination with coherent light during flight of the rotorcraft; and

[0110] at least one photodetector configured to detect radiation scattered in response to the illumination provided by the laser source;

[0111] wherein the chip-scale LIDAR sensor is carried by the fuselage such that the laser source is configured to illuminate the plurality of blades as the blades rotate to allow measurement of blade position or to illuminate terrain below the rotorcraft to provide a height measurement.

[0112] Item 16. The rotorcraft of item 15, wherein the laser source comprises a frequency- modulated continuous wave laser diode.

[0113] Item 17. The rotorcraft of item 15, wherein the at least one photodiode comprises a pair of dual balanced photodetectors.

[0114] Item 18. The rotorcraft of item 15, wherein the chip-scale LIDAR sensor further comprises:

[0115] a light splitter configured to split light produced by the laser source into a first portion and a second portion, and the first portion is directed to illuminate the plurality of blades or a terrain below the rotorcraft as the blades rotate;

[0116] a waveguide configured to support propagation of the second portion of light produced by the laser source; and

[0117] a coupler configured to couple the second portion of light propagating along the waveguide with radiation scattered in response to illumination provided by the laser source;

[0118] wherein the at least one photodetector is responsive to the coupler and configured to receive from the coupler the second portion of light propagating along the waveguide and the radiation scattered in response to the illumination provided by the laser source.

[0119] 19. The rotorcraft of item 15, further comprising processing circuitry configured to determine, in response to the chip-scale LIDAR sensor, at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on radiation scattered from a respective blade of the plurality of blades and detected by the at least one photodetector.

[0120] Item 20. The rotorcraft of item 19, further comprising an actuator configured to alter, in response to the processing circuitry, a position of the respective blade during flight based on at least one of the blade pitch angle, the blade flap angle, the blade lead position, or the blade lag position determined by the processing circuitry.

[0121] Those skilled in the art having the benefit of the teachings of the present description and associated drawings presented herein below realize numerous modifications and other embodiments of the present description. Thus, it is intended that the scope of the present description disclosed herein not be limited by the particular disclosed embodiments described above but should be determined only by a fair reading of the claims that follow together with the full range of equivalents to which such claims are entitled. Further, while the above description has been made in the context of specific combinations of elements and / or functions, it is recognized that different combinations of elements and / or functions could be provided and would be evident to one of ordinary skill in the art having the benefit of the teachings of the present description. Therefore, it is intended that the scope of the present description be determined only by the appended claims and equivalents thereto. While the specification has been described in an exemplary embodiment, there are many alternatives that fall within the scope of the present description.

Claims

1. A method for dynamically measuring blade position during flight of a rotorcraft (10), the method comprising: repeatedly illuminating, by a tracking sensor mounted on the rotorcraft (10), the blades (14) of the rotorcraft (10) with coherent light as the blades (14) rotate, wherein the tracking sensor comprises: a laser source (22) configured to repeatedly illuminate the blades (14) of the rotorcraft (10) with coherent light as the blades rotate during flight of the rotorcraft (10); at least one photodetector configured to detect radiation scattered in response to the illumination provided by the laser source; a beamsplitter configured to split light produced by the laser source into a first portion and a second portion, the first portion being directed to illuminate the blades and the second portion being directed toward the at least one photodetector; and a coupler configured to couple the second portion of the light with the radiation scattered in response to the illumination provided by the laser source; detecting radiation scattered from the blades (14) in response to the illumination of the blades (14); determining at least one of a blade pitch angle, a blade flap angle, a blade lead position, or a blade lag position based on the radiation scattered from the blades (14) and detected; and altering the position of the blades during flight of the rotorcraft based on the determined at least one of the blade pitch angle, the blade flap angle, the blade lead position, or the blade lag position.

2. The method of claim 1, wherein, repeatedly illuminating the blades (14) of the rotorcraft (10) comprises repeatedly illuminating the blades (14) at a location closer to a distal end (18) of the blades (14) than to a rotor axis of rotation (16) about which the blades (14) rotate.

3. The method of claim 1, wherein, repeatedly illuminating the blades (14) of the rotorcraft (10) comprises repeatedly illuminating the blades with a plurality of the tracking sensors (20) positioned at different locations on a fuselage (12) of the rotorcraft (10).

4. The method of claim 1, wherein, determining the blade pitch angle comprises: determining a distance (60) from the blades (14) based on the radiation scattered from the blades (14) and detected; and based on the width (W B ) of the blade (14) and the deviation of the distance from the blade (14) from the distance to a non-pitched reference blade position, the blade pitch angle is determined.

5. The method of claim 4, wherein, repeatedly illuminating the blades (14) comprises repeatedly illuminating the blades (14) with radiation produced by a laser source, and wherein determining the distance comprises determining a distance between the laser source and an edge of the blade.

6. The method of claim 1, wherein, determining the blade flap angle comprises: determining a distance from the blades (14) based on the radiation scattered from the blades (14) and detected; and based on a length (L B ) of the blade (14) and a deviation of the distance from the blade (14) from a distance to a non-flapping reference blade position.

7. The method of claim 1, wherein, determining the blade lead position or the blade lag position comprises: detecting a presence of the blades (14) at a predetermined location within a rotational path of the blades (14); determining a detection time (82) at which the presence of the blades (14) is detected; and determining a detection time (82) at which the presence of the blades (14) is detected; and determining a blade position (84) based on a relationship of the detected time to a predetermined time associated with a reference blade that is neither ahead nor behind, wherein determining the blade position includes determining that the blade is ahead in instances in which the detected time is before the predetermined time, and determining that the blade is behind in instances in which the detected time is after the predetermined time.

8. A blade positioning system (40) for dynamically measuring a position of a blade (14) during flight of a rotary wing aircraft (10), the blade positioning system (40) comprising: a tracking sensor (20) mounted on the rotary wing aircraft (10), the tracking sensor comprising: a laser source (22) configured to repeatedly illuminate the blade (14) of the rotary wing aircraft (10) with coherent light as the blade (14) rotates during flight of the rotary wing aircraft (10); at least one photodetector (26) configured to detect radiation scattered from the blade (14) in response to the illumination of the blade (14); a beamsplitter configured to split light produced by the laser source into a first portion and a second portion, the first portion being directed to illuminate the blade and the second portion being directed toward the at least one photodetector; and a coupler configured to couple the second portion of the light with the radiation scattered in response to the illumination provided by the laser source; and processing circuitry (42) configured to determine at least one of a blade pitch angle, a blade flap angle, a blade ahead position, or a blade behind position based on radiation scattered from the blade (14) and detected by the at least one photodetector (26) in response to the tracking sensor (20), an actuator configured to alter the position of the blade during flight of the rotary wing aircraft based on at least one of the blade pitch angle, the blade flap angle, the blade ahead position, or the blade behind position determined by the processing circuitry in response to the processing circuitry.

9. The blade positioning system (40) according to claim 8, wherein, The tracking sensor (20) is mounted on the rotary wing aircraft (10) such that the laser source (22) is configured to repeatedly illuminate the blade (14) at a position closer to a distal end (18) of the blade (14) than to a rotor axis of rotation (16) about which the blade (14) rotates.

10. The blade positioning system (40) of claim 8, further comprising a plurality of tracking sensors mounted at different positions on the rotary wing aircraft (10).

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