A UAV telemetry method and system based on multifunctional laser radar

Abstract

The present invention provides a UAV telemetry method and system based on a multifunctional laser radar, the method comprising: the optical signal emitted by the laser is branched to the main interferometer and the auxiliary interferometer through the first fiber coupler; the optical signal is respectively passed through the signal arm and the reference arm and is combined into a light signal by a third fiber coupler included in the main interferometer, and the combined light signal is divided into a horizontal polarized light signal and a vertical polarized light signal through a polarization beam splitter; the optical signal is converted into electrical signal data by a photoelectric detector; the electrical signal data is sent to the operation control unit to realize strain sensing monitoring, temperature sensing monitoring and remote ranging monitoring of the UAV surface. The present invention can realize the functions of strain sensing, temperature sensing and fiber laser radar ranging based on the sensing optical fiber arranged on the UAV wing and the photoelectric sensing module on the UAV belly to form a multifunctional laser radar.

Description

Technical Field

[0001] The present invention relates to the field of UAV remote sensing detection technology, and in particular to a UAV telemetry method and system based on a multifunctional laser radar. Background Art

[0002] The UAV remote sensing system is a high-tech technology that integrates UAV, remote sensing, GPS positioning and IMU attitude determination. It has the advantages of flexibility, safety and easy operation. Compared with satellite remote sensing, UAV remote sensing has higher temporal resolution and can avoid the influence of clouds; compared with airborne remote sensing, it is cheaper and safer. Therefore, when collecting remote sensing images for a large area, UAVs are often used as remote sensing platforms to carry different sensors for efficient and rapid ground situation monitoring, which plays an important role in dynamic monitoring of land use, mineral resource exploration, geological environment and disaster investigation, marine resource and environmental monitoring, etc. As a flexible aerial platform, UAVs can also carry laser radar equipment to achieve high-precision remote sensing of the ground or buildings, especially for high-precision DEM data acquisition in some difficult mapping areas, such as vegetation coverage areas, coastal areas, island reef areas, desert areas, etc. The advantages of this technology are more obvious.

[0003] Due to the continuous advancement of science and technology, drones equipped with LiDAR modules are gradually being used in various industries such as geological exploration and power transmission line operation and maintenance. Therefore, higher requirements are placed on the long-term reliability and safety of drones. During the operation of drones equipped with LiDAR modules, accidents such as drone failure and wing damage frequently occur due to factors such as strong winds, lightning strikes, structural deformation and aging. Drones usually fly at high altitudes and the operating environment temperature is relatively low, resulting in low conversion efficiency of drone batteries. Drones are prone to operating under "false power" conditions, which poses a risk of "false power crashes".

[0004] To this end, how to provide a remote sensing detection system for the status of a drone, including but not limited to remotely detecting abnormal stress or deformation of the drone's wings, and temperature changes of the drone's wings. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a UAV telemetry method and system based on a multifunctional laser radar to eliminate or improve one or more defects existing in the prior art.

[0006] One aspect of the present invention provides a remote sensing monitoring method for an unmanned aerial vehicle based on a multifunctional laser radar. The method is implemented based on a telemetry system of an unmanned aerial vehicle based on a multifunctional laser radar. The system comprises an optical frequency domain reflection system, a sensing optical fiber, an optical fiber radar probe system and an operation control unit. The optical frequency domain reflection system comprises a laser, a first optical fiber coupler, a main interferometer, an auxiliary interferometer and a polarization beam splitter. The main body of the sensing optical fiber is distributed on the surface of the unmanned aerial vehicle. One end of the sensing optical fiber is connected to a circulator included in the main interferometer, and the other end is wrapped around the bottom of the unmanned aerial vehicle and connected to the optical fiber radar probe system. The method comprises the following steps: the optical signal emitted by the laser is branched to the main interferometer and the auxiliary interferometer through the first optical fiber coupler, and the second optical fiber coupler included in the main interferometer further branches the branched optical signal to a signal arm including a circulator and a reference arm including a polarization controller; the optical signal is respectively branched to the signal arm and the reference arm on the trunk The third optical fiber coupler included in the interferometer generates beat frequency to merge into one optical signal, and the merged optical signal is divided into a horizontally polarized light signal and a vertically polarized light signal through a polarization beam splitter; the horizontally polarized light signal is converted into a first electrical signal data by a first photodetector, the vertically polarized light signal is converted into a second electrical signal data by a second photodetector, and the optical signal passing through the auxiliary interferometer is converted into a third electrical signal data by a third photodetector; the fourth electrical signal data for laser pulse ranging is collected by a fiber optic radar probe system; the first electrical signal data, the second electrical signal data, the third electrical signal data and the fourth electrical signal data are sent to the operation control unit, and the operation control unit performs strain sensing monitoring and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone, and the operation control unit performs remote ranging monitoring of the drone based on the fourth electrical signal data.

[0007] In some embodiments of the present invention, for the optical signal branched to the signal arm, the method also includes: the optical signal enters the sensing optical fiber through a circulator, and returns along the sensing optical fiber an optical signal carrying physical information used for sensing monitoring and temperature sensing monitoring; for the optical signal branched to the reference arm, the method also includes: using the polarization controller to adjust the polarization state of the optical signal.

[0008] In some embodiments of the present invention, the auxiliary interferometer includes a fourth fiber coupler and a fifth fiber coupler. For the optical signal branched to the auxiliary interferometer, the method includes: the fourth fiber coupler further branches the branched optical signal into one ordinary optical fiber and one delay optical fiber, and the two optical signals passing through the ordinary optical fiber and the delay optical fiber respectively are merged into one optical signal in the fifth fiber coupler.

[0009] In some embodiments of the present invention, the type of the first fiber optic coupler is a 10:90 fiber optic coupler, the type of the second fiber optic coupler is a 1:99 fiber optic coupler, the type of the third fiber optic coupler is a 50:50 fiber optic coupler, the type of the fourth fiber optic coupler is a 50:50 fiber optic coupler, and the type of the fifth fiber optic coupler is a 50:50 fiber optic coupler.

[0010] In some embodiments of the present invention, the sensing optical fiber is arranged in a "Z" shape along the extension direction of the UAV wing; or the sensing optical fiber first extends to the far end of the UAV wing on the UAV wing, and is arranged in a "Z" shape perpendicular to the extension direction of the UAV wing.

[0011] In some embodiments of the present invention, the operation control unit performs the steps of strain sensing monitoring and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of sensing optical fiber on the surface of the drone, including: the operation control unit calculates the strain sensing parameters and the position of the strain occurring at the sensing optical fiber based on the wavelength offset principle of back Rayleigh scattering, and determines the position where the strain occurs in the drone combined with the distribution of the sensing optical fiber on the surface of the drone; the operation control unit calculates the temperature sensing parameters based on the wavelength offset principle of back Rayleigh scattering, thereby monitoring the temperature of the drone surface in real time.

[0012] In some embodiments of the present invention, the radar probe system includes an optical switch and a probe unit composed of multiple optical fibers and lenses. The probe unit is installed at the bottom of the drone and faces different directions. For the optical signal entering the fiber optic radar probe system, the method includes: the optical signal is switched between the multiple probe units through the optical switch, the optical signal in the optical fiber is irradiated on objects around the drone through the probe unit and spatial light, and the light reflection after the object is irradiated is received by the fourth photodetector and converted into the fourth electrical signal data.

[0013] In some embodiments of the present invention, after obtaining the fourth electrical signal data, the method further includes: performing laser pulse ranging based on the fourth electrical signal data to obtain the physical distance between the drones in different directions, thereby determining the altitude information of the drone.

[0014] In some embodiments of the present invention, the method further includes: setting safety temperature thresholds at different altitudes, combining temperature perception monitoring of the surface of the drone and the determined altitude information of the drone, and when the temperature perception monitoring exceeds the preset safety temperature threshold, a temperature warning message is issued through the operation control unit.

[0015] Corresponding to the above method, the present invention also provides a UAV telemetry system based on a multifunctional laser radar, which includes an optical frequency domain reflection system, a sensing optical fiber, a fiber radar probe system and an operation control unit; the optical frequency domain reflection system includes a laser, a first fiber coupler, a main interferometer, an auxiliary interferometer and a polarization beam splitter; the main body of the sensing optical fiber is distributed on the surface of the UAV, one end of the sensing optical fiber is connected to the circulator included in the main interferometer, and the other end is wrapped around the bottom of the UAV and connected to the fiber radar probe system; the laser is used to emit an optical signal; the first fiber coupler is used to branch the optical signal to the main interferometer and the auxiliary interferometer; the main interferometer is used to further branch the branched optical signal to a signal arm including a circulator and a reference arm including a polarization controller based on the second fiber coupler it includes; the main interferometer is also used to beat the optical signal passing through the signal arm and the reference arm respectively based on the third fiber coupler it includes The two optical signals are merged into one optical signal, and the merged optical signal is divided into a horizontally polarized light signal and a vertically polarized light signal through a polarization beam splitter; the operation control unit is used to receive the first electrical signal data, the second electrical signal data, the third electrical signal data and the fourth electrical signal data, and based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone, the strain sensing monitoring and temperature sensing monitoring of the drone surface are performed, and the operation control unit performs remote ranging monitoring of the drone based on the fourth electrical signal data; the system also includes a first photodetector, a second photodetector and a third photodetector, the first photodetector is used to convert the horizontally polarized light signal into the first electrical signal data, the second photodetector is used to convert the vertically polarized light signal into the second electrical signal data, and the third photodetector is used to convert the optical signal passing through the auxiliary interferometer into the third electrical signal data; the optical fiber radar probe system is used to collect the fourth electrical signal data for laser pulse ranging.

[0016] The UAV remote sensing monitoring method based on multifunctional laser radar proposed in the present invention can form a multifunctional laser radar based on the sensing optical fiber arranged on the wing of the UAV and the photoelectric sensing module on the belly of the UAV, detect deformation and temperature by measuring the backscattered light signal of the optical fiber, and perform radar ranging by the light transmitted back from the laser after illuminating the external object, thereby realizing the functions of strain perception, temperature perception and fiber laser radar ranging.

[0017] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically indicated in the specification and the accompanying drawings.

[0018] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention. The components in the drawings are not drawn to scale, but are only for illustrating the principles of the present invention. In order to facilitate the illustration and description of some parts of the present invention, the corresponding parts in the drawings may be enlarged, that is, they may become larger relative to other components in the exemplary device actually manufactured according to the present invention. In the drawings:

[0020] Figure 1 The present invention is a flowchart of a UAV telemetry method based on a multifunctional laser radar in one embodiment of the present invention.

[0021] Figure 2 Schematic diagram of the structure of a UAV telemetry system in one embodiment of the present invention.

[0022] Figure 3 1 is a block diagram of an optical frequency domain reflectometry system included in a UAV telemetry system according to an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the structure of a telemetry system for a quad-rotor UAV equipped with a multifunctional laser radar in one embodiment of the present invention.

[0024] Figure 5 This is a schematic structural diagram of a telemetry system for a quad-rotor UAV equipped with a multifunctional laser radar in another embodiment of the present invention.

[0025] Figure 6 The figure is a structural block diagram of a fiber optic radar probe system fixed to the bottom of a drone in one embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0027] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0028] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0029] It should also be noted that, unless otherwise specified, the term “connection” herein may refer not only to a direct connection but also to an indirect connection involving an intermediate.

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0031] In order to overcome the problems existing in the prior art, the present invention proposes a UAV telemetry method and system based on a multifunctional laser radar, which can use optical frequency domain reflectometry (OFDR) technology to monitor abnormal stress or deformation (such as bending, torsion, shear, etc.) of various points on the UAV wing; can use optical fiber distributed temperature measurement technology to monitor the temperature changes of various points on the UAV wing; can form a multifunctional laser radar based on the sensing optical fiber arranged on the UAV wing and the optoelectronic sensing module on the belly of the UAV to realize the functions of strain sensing, temperature sensing and laser ranging.

[0032] Figure 1 This is a flow chart of a UAV telemetry method based on a multifunctional laser radar in one embodiment of the present invention. The method comprises the following steps:

[0033] Step S110: The optical signal emitted by the laser is branched to the main interferometer and the auxiliary interferometer through the first optical fiber coupler, and the second optical fiber coupler included in the main interferometer further branches the branched optical signal to a signal arm including a circulator and a reference arm including a polarization controller.

[0034] In the specific implementation process, the role of the photoelectric detector is to convert optical information data into electrical signal data.

[0035] Step S120: The optical signals passing through the signal arm and the reference arm are combined into one optical signal by beat frequency in the third optical fiber coupler included in the main interferometer, and the combined optical signal is divided into a horizontally polarized light signal and a vertically polarized light signal by a polarization beam splitter.

[0036] Step S130: Use the first photodetector to convert the horizontally polarized light signal into the first electrical signal data, use the second photodetector to convert the vertically polarized light signal into the second electrical signal data, use the third photodetector to convert the light signal passing through the auxiliary interferometer into the third electrical signal data; use the fiber optic radar probe system to collect the fourth electrical signal data for laser pulse ranging.

[0037] Step S140: The first electrical signal data, the second electrical signal data, the third electrical signal data and the fourth electrical signal data are sent to the operation control unit, which performs strain sensing monitoring and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of sensing optical fiber on the surface of the drone, and performs remote ranging monitoring of the drone based on the fourth electrical signal data.

[0038] Figure 2 The structure diagram of the UAV telemetry system in one embodiment of the present invention. In the UAV telemetry system 200 based on the multifunctional laser radar, the UAV includes an optical frequency domain reflection system 210, a sensing optical fiber 220 is distributed on the wings of the UAV, and a fiber optic radar probe system 230 is installed at the bottom of the UAV. The UAV telemetry system 200 includes an optical frequency domain reflection system 210, a sensing optical fiber 220, a fiber optic radar probe system 230 and an operation control unit. The optical frequency domain reflection system 210 includes a laser, a first fiber coupler, a main interferometer, an auxiliary interferometer and a polarization beam splitter. The main body of the sensing optical fiber 220 is distributed on the surface of the UAV. One end of the sensing optical fiber 220 is connected to the circulator included in the main interferometer, and the other end is connected to the fiber optic radar probe system 230 around the bottom of the UAV.

[0039] By adopting the embodiment of the invention, a multifunctional laser radar can be formed based on the sensing optical fiber arranged on the wing of the drone and the optoelectronic sensing module on the belly of the drone. The deformation and temperature can be detected by measuring the backscattered light signal of the optical fiber. The radar ranging is performed by the light emitted from the laser and then transmitted back to the external object, which can realize the functions of strain perception, temperature perception and fiber-optic laser radar ranging.

[0040] In some embodiments of the present invention, for the optical signal branched to the signal arm, the method further includes: the optical signal enters the sensing optical fiber through a circulator, and returns along the sensing optical fiber an optical signal carrying physical information for sensing monitoring and temperature sensing monitoring.

[0041] By adopting this embodiment of the invention, the sensing optical fiber used for strain sensing and temperature sensing can be extended from the circulator inside the drone and fixed on the upper surface of the four wings of the aircraft in a "Z"-shaped distribution manner, so as to realize distributed measurement and sensing of the strain and temperature of the drone wings based on the sensing optical fiber and the optical frequency domain reflection system.

[0042] In some embodiments of the present invention, for the optical signal branched to the reference arm, the method further includes: adjusting the polarization state of the optical signal by using the polarization controller.

[0043] By adopting this embodiment of the invention, the polarization state of the optical signal can be adjusted based on the polarization controller as the reference arm.

[0044] In some embodiments of the present invention, the auxiliary interferometer includes a fourth fiber coupler and a fifth fiber coupler. For the optical signal branched to the auxiliary interferometer, the method includes: the fourth fiber coupler further branches the branched optical signal into one ordinary optical fiber and one delay optical fiber, and the two optical signals passing through the ordinary optical fiber and the delay optical fiber respectively are merged into one optical signal in the fifth fiber coupler.

[0045] By adopting this embodiment of the invention, an external sampling clock signal which is caused by the nonlinear effect of a light source can be eliminated by using an auxiliary interferometer.

[0046] Optionally, in some embodiments of the present invention, the type of the first fiber optic coupler is a 10:90 fiber optic coupler, the type of the second fiber optic coupler is a 1:99 fiber optic coupler, the type of the third fiber optic coupler is a 50:50 fiber optic coupler, the type of the fourth fiber optic coupler is a 50:50 fiber optic coupler, and the type of the fifth fiber optic coupler is a 50:50 fiber optic coupler.

[0047] In some embodiments of the present invention, the layout of the sensing optical fiber may be: the sensing optical fiber is arranged in a "Z" shape along the extension direction of the drone wing. Or (2) the sensing optical fiber first extends to the far end of the drone wing on the drone wing, and is arranged in a "Z" shape perpendicular to the extension direction of the drone wing. The present invention is not limited to this, and the above two arrangements are only examples, but in the subsequent process of visualizing the deformation, it is necessary to know which position of the drone wing corresponds to the different length positions of the optical fiber.

[0048] The advantages of the Z-shaped arrangement of the embodiment of the invention are that it is convenient to fix to the wing of the drone, can achieve full coverage of the wing, and is also convenient to build a wing force model. Furthermore, based on the combination of the sensing optical fiber arranged on the wing of the drone and the optical frequency domain reflection system, the strain of the drone wing can be monitored.

[0049] In some embodiments of the present invention, the operation control unit performs strain sensing and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone, including:

[0050] (1) The operation control unit calculates the strain sensing parameter and the position of the strain occurrence position on the sensing optical fiber based on the wavelength offset principle of the back Rayleigh scattering, and determines the position where the strain occurs on the drone in combination with the distribution of the sensing optical fiber on the surface of the drone. (2) The operation control unit calculates the temperature sensing parameter based on the wavelength offset principle of the back Rayleigh scattering, thereby monitoring the temperature of the drone surface in real time.

[0051] Among them, in the specific implementation process, when deformation occurs somewhere on the four wings, the strain perception process is as follows: the optical fiber at the deformed point will transmit the received information back to the wireless communication module inside the drone, and then transmit it back to the mobile phone of the aircraft operator through communication methods such as wifi / 4G. The transmitted data is processed by the data processing software built into the mobile phone, and finally presented in the mobile phone in the form of a graphic, showing the location of the abnormal deformation.

[0052] Among them, in the specific implementation process, when the ambient temperature of the aircraft changes instantly, the temperature perception process is: the entire optical fiber will transmit the received information back to the wireless communication module inside the drone, and then transmit it back to the mobile phone of the drone operator through communication methods such as wifi / 4G. The transmitted data is processed by the data processing software built into the mobile phone, and finally the temperature information is displayed.

[0053] In the above embodiments of the present invention, all information is processed by transmitting it back to the wireless communication module that maintains communication connection with the drone through the wireless communication module for data processing. The wireless communication module can be hardware with computing and control capabilities such as a mobile phone.

[0054] In a specific implementation process, the operation control unit may be a mobile phone, which can present the location where strain or abnormal deformation occurs in the form of graphics.

[0055] By adopting the embodiment of the invention, the status of the drone is monitored through the operation control module based on the electrical signal data collected and converted by the sensor optical fiber, and presented in real time in the form of graphics.

[0056] In some embodiments of the present invention, the radar probe system includes an optical switch and a probe unit composed of multiple optical fibers and lenses. The probe unit is installed at the bottom of the drone and faces different directions. For the optical signal entering the fiber optic radar probe system, the method includes: the optical signal is switched between the multiple probe units through the optical switch, the optical signal in the optical fiber is irradiated on the objects around the drone through the probe unit and the spatial light, and the light reflection after the object is irradiated is received by the fourth photodetector and converted into the fourth electrical signal data.

[0057] In the specific implementation process, the four lenses can be fixed at 90 degrees at the four directions of the front, back, left and right of the bottom of the drone. The light transmitted by the sensing optical fiber is transmitted to the optical switch. Four optical fibers are fixed behind the optical switch. The optical switch switches among the four optical fibers. The light in the optical fiber is irradiated to the four lenses fixed at the bottom of the drone through the spatial light. After the spatial light is irradiated to the objects around the drone flying through the four lenses, the light is reflected back and received by the photoelectric detector 4 fixed at the bottom of the drone. The optical information data is converted into an electrical signal and input into the wireless communication module. The location data of the drone's environment is transmitted back to the mobile phone of the aircraft operator through wireless communication methods such as wifi / 4G. The transmitted data is processed by the data processing software built into the mobile phone to realize the remote ranging function of the drone. Among them, the sensing optical fiber is connected to the multi-channel probe unit through the optical switch. Each probe unit corresponds to an orientation. The photoelectric detector fixed at the bottom of the drone receives the optical information data reflected back by the light.

[0058] By adopting the embodiment of the invention, the fiber optic radar ranging function can be realized, thereby determining the altitude of the drone, surrounding obstacles and other information.

[0059] In some embodiments of the present invention, after obtaining the fourth electrical signal data, the method further includes: performing laser pulse ranging based on the fourth electrical signal data to obtain the physical distance between the drones in different directions, thereby determining the altitude information of the drone.

[0060] In some embodiments of the present invention, the method further includes: setting safety temperature thresholds at different altitudes, combining temperature perception monitoring of the surface of the drone and the determined altitude information of the drone, and when the temperature perception monitoring exceeds the preset safety temperature threshold, a temperature warning message is issued through the operation control unit.

[0061] By adopting this embodiment of the invention, the results of temperature sensing monitoring and altitude information can be integrated, combined with the preset safety temperature thresholds under different altitudes, the temperature of the drone surface can be flexibly monitored and warned, thereby better ensuring safety.

[0062] Figure 3 1 is a block diagram of an optical frequency domain reflectometry system included in a UAV telemetry system according to an embodiment of the present invention. Figure 3 The optical frequency domain reflection system shown in the figure includes a laser, a main interferometer, an auxiliary interferometer, a photodetector, and a UAV wireless communication module. After the laser emits the laser, the transmission process in the optical frequency domain reflection system is as follows:

[0063] (1) The linear swept laser emitted by the laser is divided into two paths through a 10:90 fiber coupler, one entering the main interferometer and the other entering the auxiliary interferometer.

[0064] Among them, the fiber coupler is used to realize the distribution or combination of optical signal power between different optical fibers, and to realize the branching or combining of optical signals. Linear swept light refers to an optical signal whose frequency changes linearly with time. In a unit of time, the frequency of the optical signal increases or decreases at a constant rate. This frequency change is linear, so it is called linear swept light.

[0065] (2) In the main interferometer, the laser passes through the 1:99 fiber coupler 1 and is divided into two paths. One path passes through the polarization controller, and the other passes through the circulator. The two paths are then merged into one signal through the 50:50 fiber coupler 1. The one passing through the polarization controller is the reference arm, and the one passing through the circulator is the signal arm. After the optical signal in the signal arm passes through the circulator and enters the sensor fiber to be measured, the backscattered Rayleigh light signal carrying physical information such as strain and temperature is returned to the circulator.

[0066] (3) In the auxiliary interferometer, the laser is divided into two paths through the 50:50 fiber coupler 2. After the two signals pass through optical fibers of unequal length, they are merged into one signal through the 50:50 fiber coupler 3. The optical signal in the reference arm is mainly used for beat frequency. Beat frequency refers to the periodic change in amplitude of the waveform after superposition of two simple harmonic waves with similar frequencies. The frequency of this change is called beat frequency.

[0067] Among them, the function of the auxiliary interferometer is: based on the electrical signal data collected by the auxiliary interferometer, to ensure equal-frequency sampling, eliminate the error caused by the nonlinear effect of the laser, or in other words, eliminate the external sampling clock signal of the nonlinear effect of the light source.

[0068] In a specific embodiment of the present invention, both the main interferometer and the auxiliary interferometer are implemented based on Mach-Zehnder interferometer.

[0069] In principle, the laser included in the optical frequency domain reflectometry system emits linear frequency-sweeping light, and there is an optical path difference between the signal arm and the reference arm, which results in different frequencies of the two output lights. The two light beams will coherently produce a beat frequency, which is eventually converted into an electrical signal on the photodetector, and the data is collected and processed. Based on the wavelength offset of the backscattered Rayleigh scattering, the magnitude of physical quantities such as strain and temperature can be calculated, thereby realizing functions such as strain sensing and temperature sensing.

[0070] Figure 4 The schematic diagram of the structure of a telemetry system of a quad-rotor drone equipped with a multifunctional laser radar in one embodiment of the present invention is shown in FIG. The sensing optical fiber is arranged in a "Z" shape along the extension direction of the drone's wings. Figure 5The schematic diagram of the structure of a telemetry system of a quad-rotor drone equipped with a multifunctional laser radar in another embodiment of the present invention is shown in FIG. Among them, the sensing optical fiber first extends to the far end of the drone wing on the drone wing and is arranged in a "Z" shape perpendicular to the extension direction of the drone wing.

[0071] Figure 4-5 The drone in the figure is a quad-rotor drone. The middle part of a quad-rotor drone is difficult to deform during flight, and the main deformation area is the four-way wings. Figure 3 The laser, fiber coupler, circulator, time-delay fiber, polarization controller, polarization beam splitter, photodetector and wireless communication module included in the drone are all built into the drone. The sensing fiber for strain and temperature sensing extending from the circulator inside the drone is connected along the following path: Figure 4 or Figure 5 The optical fiber is fixed on the upper surface of the four wings of the aircraft in a "Z" shape. Figure 4 or Figure 5 After being fixed in a "Z" shape, it goes along the surface of the drone to the bottom of the drone and is connected to the fiber optic radar probe system. The function of the polarization beam splitter is to separate the horizontal polarization and vertical polarization of a beam of light.

[0072] Figure 6 FIG. 1 is a structural block diagram of a fiber optic radar probe system fixed to the bottom of a drone in one embodiment of the present invention. Figure 6 In the embodiment of the invention shown, the optical switch is a 1-to-4 optical switch, and the light transmitted in the sensing optical fiber is transmitted to the 1-to-4 optical switch. The optical switch can switch among the four optical fibers at a frequency of 4 Hz. Four optical fibers are fixed behind the optical switch, and the light in the optical fiber is irradiated to the four lenses fixed at the bottom of the drone through spatial light. The four lenses are fixed at 90 degrees to the four directions of the front, back, left, and right of the bottom of the drone. After the spatial light is irradiated to the objects around the drone through the four lenses, the light is reflected back and received by the photoelectric detector 4 fixed at the bottom of the drone, and the optical information data is converted into an electrical signal and input into the wireless communication module. The location data of the drone's environment is transmitted back to the mobile phone of the aircraft operator through wireless communication methods such as wifi / 4G. The transmitted data is processed by the data processing software built into the mobile phone to realize the remote ranging function of the drone.

[0073] Corresponding to the above method, the present invention also provides a UAV telemetry system based on a multifunctional laser radar, which includes an optical frequency domain reflection system, a sensing optical fiber, a fiber radar probe system, and an operation control unit; the optical frequency domain reflection system includes a laser, a first fiber coupler, a main interferometer, an auxiliary interferometer, and a polarization beam splitter; the main body of the sensing optical fiber is distributed on the surface of the UAV, one end of the sensing optical fiber is connected to the circulator included in the main interferometer, and the other end is connected to the bottom of the UAV and connected to the fiber radar probe system. Among them, the various parts of the system are composed of:

[0074] (1) A laser is used to emit an optical signal; the first optical fiber coupler is used to split the optical signal to the main interferometer and the auxiliary interferometer; the main interferometer is used to further split the split optical signal to a signal arm including a circulator and a reference arm including a polarization controller based on the second optical fiber coupler it contains; the main interferometer is also used to combine the optical signals passing through the signal arm and the reference arm into one optical signal based on the third optical fiber coupler it contains, and the combined optical signal is divided into a horizontally polarized light signal and a vertically polarized light signal through a polarization beam splitter.

[0075] (2) The operation control unit is used to receive the first electrical signal data, the second electrical signal data, the third electrical signal data and the fourth electrical signal data, and perform strain sensing monitoring and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone. The operation control unit performs remote ranging monitoring of the drone based on the fourth electrical signal data.

[0076] (3) The system also includes a first photodetector, a second photodetector and a third photodetector. The first photodetector is used to convert a horizontally polarized light signal into a first electrical signal data. The second photodetector is used to convert a vertically polarized light signal into a second electrical signal data. The third photodetector is used to convert a light signal passing through an auxiliary interferometer into a third electrical signal data. The optical fiber radar probe system is used to collect fourth electrical signal data for laser pulse ranging.

[0077] As described above, the UAV remote sensing monitoring method and system based on the multifunctional laser radar proposed in the present invention can form a multifunctional laser radar based on the sensing optical fiber arranged on the wing of the UAV and the photoelectric sensing module on the belly of the UAV, detect deformation and temperature by measuring the backscattered light signal of the optical fiber, and perform radar ranging by the light transmitted back from the laser after illuminating the external object, so as to realize the functions of strain perception, temperature perception and fiber laser radar ranging.

[0078] The key points and advantages of the method proposed by the present invention are:

[0079] (1) The optical frequency domain reflectometry system can be used to monitor abnormal stress or deformation at various points on the UAV wing.

[0080] (2) The fiber optic distributed temperature measurement system can be used to monitor the temperature changes at various points on the wings of the drone.

[0081] (3) The sensing optical fiber for strain sensing and temperature sensing can be extended from the circulator inside the drone and fixed on the upper surface of the four wings of the aircraft in a "Z" shape distribution. Based on the sensing optical fiber and the optical frequency domain reflection system, the strain and temperature of the drone wings can be measured and sensed in a distributed manner. This solution is easy to implement. It only requires placing the optical frequency domain reflection system inside the drone and leading out the optical fiber, which is fixed on the aircraft wing in a Z shape. The advantage of the Z-shaped arrangement is that it is easy to fix to the drone wing and can achieve full coverage of the wing. It is also convenient to build a wing force model.

[0082] (4) The optical fiber led out from the optical frequency domain reflection system placed inside the drone can be used to lead the sensing optical fiber fixed on the wing of the drone to the fiber optic radar probe system at the bottom of the drone, thereby realizing the fiber optic radar ranging function.

[0083] It should be understood by those skilled in the art that the exemplary components, systems and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0084] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

[0085] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A UAV remote sensing monitoring method based on multifunctional laser radar, characterized in that: The method is implemented based on a UAV telemetry system of a multifunctional laser radar, the system comprises an optical frequency domain reflection system, a sensing optical fiber, a fiber radar probe system and an operation control unit, the optical frequency domain reflection system comprises a laser, a first fiber coupler, a main interferometer, an auxiliary interferometer and a polarization beam splitter, the main body of the sensing optical fiber is distributed on the surface of the UAV, one end of the sensing optical fiber is connected to a circulator included in the main interferometer, and the other end is wound around the bottom of the UAV to connect to the fiber radar probe system, the method comprises the following steps: The optical signal emitted by the laser is split to the main interferometer and the auxiliary interferometer through the first optical fiber coupler, and the second optical fiber coupler included in the main interferometer further splits the split optical signal to a signal arm including a circulator and a reference arm including a polarization controller; The optical signals passing through the signal arm and the reference arm are respectively combined into one optical signal by a beat frequency in a third optical fiber coupler included in the main interferometer, and the combined optical signal is divided into a horizontally polarized light signal and a vertically polarized light signal by a polarization beam splitter; The horizontally polarized light signal is converted into the first electrical signal data by using the first photodetector, the vertically polarized light signal is converted into the second electrical signal data by using the second photodetector, and the light signal passing through the auxiliary interferometer is converted into the third electrical signal data by using the third photodetector; the fourth electrical signal data for laser pulse ranging is collected by using the optical fiber radar probe system; The first electrical signal data, the second electrical signal data, the third electrical signal data and the fourth electrical signal data are sent to the operation control unit, and the operation control unit performs strain sensing monitoring and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone, and the operation control unit performs remote ranging monitoring of the drone based on the fourth electrical signal data; For the optical signal branched to the signal arm, the method further includes: the optical signal enters the sensing optical fiber through the circulator, and returns the optical signal carrying physical information for sensing monitoring and temperature sensing monitoring along the sensing optical fiber; for the optical signal branched to the reference arm, the method further includes: adjusting the polarization state of the optical signal by using the polarization controller; The operation control unit performs strain sensing and temperature sensing monitoring on the surface of the drone based on the wavelength offset principle of back Rayleigh scattering combined with the distribution of the sensing optical fiber on the surface of the drone, including: the operation control unit calculates the strain sensing parameter and the position of the strain occurring at the sensing optical fiber based on the wavelength offset principle of back Rayleigh scattering, and determines the position where the strain occurs in the drone combined with the distribution of the sensing optical fiber on the surface of the drone; the operation control unit calculates the temperature sensing parameter based on the wavelength offset principle of back Rayleigh scattering, so as to monitor the temperature of the drone surface in real time; The radar probe system includes an optical switch and a probe unit composed of multiple optical fibers and lenses. The probe unit is installed at the bottom of the drone and faces different directions. For the optical signal entering the fiber optic radar probe system, the method includes: the optical signal is switched between the multiple probe units through the optical switch, the optical signal in the optical fiber is irradiated on the objects around the drone through the probe unit and spatial light, the light reflection after the object is irradiated is received by the fourth photodetector and converted into the fourth electrical signal data, after obtaining the fourth electrical signal data, laser pulse ranging is performed based on the fourth electrical signal data to obtain the physical distance between the drones in different directions, thereby determining the altitude information of the drone.

2. The method according to claim 1, characterized in that: The auxiliary interferometer comprises a fourth optical fiber coupler and a fifth optical fiber coupler. For the optical signal branched to the auxiliary interferometer, the method comprises: The fourth optical fiber coupler further splits the split optical signal into one common optical fiber and one time-delay optical fiber, and the two optical signals passing through the common optical fiber and the time-delay optical fiber respectively are combined into one optical signal in the fifth optical fiber coupler.

3. The method according to claim 2, characterized in that The type of the first fiber optic coupler is a 10:90 fiber optic coupler, the type of the second fiber optic coupler is a 1:99 fiber optic coupler, the type of the third fiber optic coupler is a 50:50 fiber optic coupler, the type of the fourth fiber optic coupler is a 50:50 fiber optic coupler, and the type of the fifth fiber optic coupler is a 50:50 fiber optic coupler.

4. The method according to claim 1, characterized in that: The sensing optical fibers are arranged in a "Z" shape along the extension direction of the drone wing; or The sensing optical fiber first extends to the far end of the drone wing on the drone wing, and is arranged in a "Z" shape perpendicular to the extension direction of the drone wing.

5. The method according to claim 1, characterized in that The method also includes: setting safety temperature thresholds at different altitudes, combining temperature sensing monitoring of the surface of the drone and the determined altitude information of the drone, and when the temperature sensing monitoring exceeds the preset safety temperature threshold, issuing a temperature warning message through the operation control unit.

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