An inspection method and device and offshore wind farm inspection system

Abstract

The present specification relates to the technical field of offshore wind power, and particularly relates to a method and device for inspection and an offshore wind farm inspection system. The offshore wind farm inspection system comprises an aircraft, a cable and a control cabinet. The cable comprises an optical fiber and a power transmission wire. The power transmission wire is used for power supply to the aircraft. One end of the cable is connected to the aircraft, and the other end is connected to a cable releasing and collecting mechanism of the control cabinet. The cable comprises a first cable section released outside the control cabinet and a second cable section collected in the control cabinet. The method for inspection comprises the following steps: transmitting a detection light signal to the aircraft through the optical fiber of the cable; receiving a reflected light signal returned by the aircraft according to the detection light signal; calculating a phase difference between the reflected light signal and the detection light signal; obtaining a first refractive index of the optical fiber in the first cable section and a second refractive index of the optical fiber in the second cable section; calculating a length of the first cable section according to the first refractive index, the second refractive index and the phase difference; and controlling the aircraft to perform inspection according to the length of the first cable section.

Description

Technical Field

[0001] The embodiments of this specification relate to the field of marine wind power technology, and specifically to an inspection method, device, and offshore wind farm inspection system. Background Art

[0002] Floating offshore wind power is one of the main development directions of offshore wind power. Floating offshore wind farms are usually located farther from the coast and in deeper waters. Compared to fixed offshore wind power, floating offshore wind turbines are generally in motion relative to the seabed, resulting in a longer operation and maintenance window, longer maintenance duration, and greater difficulty. Traditionally, visual inspections have been used to verify the integrity of wind turbine appearance. However, with the maturity of technology, drones have also been applied to wind turbine inspections. Currently, drones are widely used in the daily inspection of offshore wind turbines. Drone cameras can be used to inspect for surface contamination and cracks on wind turbine blades, as well as for contamination of wind turbine towers.

[0003] The main problems with existing drone-based offshore wind farm inspection technologies are the difficulty of drones staying in the air for long periods of time and the difficulty of accurately controlling the inspection range. Specifically, due to the limitations of the drone's battery capacity and the number of backup batteries, drones cannot stay in the air for long periods of time. The operation and maintenance window of floating offshore wind turbines is short, and they need to return to replace batteries after a period of maintenance. Flying and recovering drones and frequently replacing batteries will reduce inspection efficiency. The limitations of the offshore environment and drone positioning systems make it difficult to accurately control the scope of drone inspections, resulting in missed inspections or deviations from the offshore wind farm area, further reducing inspection efficiency. Whether it is the difficulty of drones staying in the air for long periods of time or the uncontrollable inspection range, it will occupy the already tight operation and maintenance window time, thereby causing the wind turbine to be shut down for a long time, resulting in loss of power generation.

[0004] Therefore, how to overcome the problems in existing offshore wind farm inspection methods, such as the difficulty of drones staying in the air for a long time and the inability to accurately control the inspection range, and conduct continuous, long-term and accurate inspections of offshore wind farms are key issues that need to be solved urgently. Summary of the Invention

[0005] The purpose of the embodiments of this specification is to provide an inspection method, device and offshore wind farm inspection system to overcome the problems existing in existing methods such as the difficulty of drones staying in the air for a long time and the inability to accurately control the inspection range.

[0006] In order to solve the above technical problems, the specific technical solutions of the embodiments of this specification are as follows:

[0007] In one aspect, embodiments of this specification provide an inspection method applied to an offshore wind farm inspection system; the offshore wind farm inspection system includes an aircraft, a cable, and a control cabinet; the cable includes an optical fiber and a power transmission wire; the power transmission wire is used to supply power to the aircraft; one end of the cable is connected to the aircraft, and the other end is connected to a cable release and retraction mechanism of the control cabinet; the cable includes a first cable segment released outside the control cabinet and a second cable segment retracted inside the control cabinet;

[0008] The inspection method includes:

[0009] transmitting the detection light signal to the aircraft through the optical fiber of the cable;

[0010] receiving a reflected light signal returned by the aircraft according to the detection light signal;

[0011] Calculate the phase difference between the reflected light signal and the detected light signal;

[0012] obtaining a first refractive index of an optical fiber in a first cable segment and a second refractive index of an optical fiber in a second cable segment;

[0013] calculating the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference;

[0014] The aircraft is controlled to perform inspection according to the length of the first cable segment.

[0015] Furthermore, the method further comprises:

[0016] Based on the laser phase method, the optical signal generated by the laser transmitter in the control cabinet is intensity modulated to obtain a modulated optical signal;

[0017] The generated modulated optical signal is used as a detection optical signal.

[0018] Furthermore, the calculating the phase difference between the reflected light signal and the detected light signal includes:

[0019] converting the detection light signal into a first electrical signal;

[0020] converting the reflected light signal into a second electrical signal;

[0021] extracting a baseband signal from the second electrical signal;

[0022] A phase difference between the baseband signal and the first electrical signal is calculated.

[0023] Furthermore, calculating the phase difference between the baseband signal and the first electrical signal includes:

[0024] The phase difference of the baseband signal relative to the first electrical signal is calculated using the following formula:

[0025] ;

[0026] Where, represents the angular frequency of the optical carrier, represents the angular frequency of the modulating signal, Indicates the fixed delay of optical signal transmission in optical fiber. Indicates the time it takes for an optical signal to travel through an optical fiber.

[0027] Furthermore, the method further comprises:

[0028] A linear variation model of the phase difference and the optical fiber length is constructed according to a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment.

[0029] Furthermore, calculating the length of the first cable segment according to the first refractive index, the second refractive index and the phase difference includes:

[0030] Obtaining the total length of the optical fibers in the cable;

[0031] The length of the optical fiber in the first cable segment is calculated using the linear variation model based on the first refractive index, the second refractive index, the phase difference, and the total length of the optical fiber in the cable.

[0032] Furthermore, the calculating the length of the optical fiber in the first cable segment using the linear variation model includes:

[0033] Calculate the length of the optical fiber in the first cable segment using the following formula:

[0034] ;

[0035] Where, It represents the phase difference between the fundamental frequency signal and the detection light signal after photoelectric conversion. represents the wavelength of the optical signal, represents the first refractive index, represents the second refractive index, Indicates the total length of optical fiber in the cable.

[0036] Furthermore, the method further comprises:

[0037] Obtaining the total length of the cable and the total length of the optical fibers in the cable;

[0038] If the length of the optical fiber in the first cable segment is equal to the total length of the cable, or the length of the optical fiber in the first cable segment is equal to the total length of the optical fiber in the cable, stopping releasing the cable;

[0039] If the length of the optical fiber in the second cable segment is equal to the total length of the cable, or the length of the optical fiber in the second cable segment is equal to the total length of the optical fiber in the cable, stop retracting the cable.

[0040] In yet another aspect, the embodiments of the present specification provide a method for inspecting a marine wind farm, the method comprising:

[0041] transmitting a probe light signal to the aircraft through the optical fiber of the cable;

[0042] receiving a reflected light signal returned by the aircraft according to the probe light signal;

[0043] calculating a phase difference between the reflected light signal and the probe light signal;

[0044] obtaining a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment;

[0045] calculating a length of the first cable segment according to the first refractive index, the second refractive index and the phase difference;

[0046] controlling the aircraft to perform inspection according to the length of the first cable segment.

[0047] In yet another aspect, a marine wind farm inspection system is provided, the marine wind farm inspection system comprising an aircraft, a cable and a control cabinet; the cable comprising an optical fiber and a power transmission conductor; the power transmission conductor being used to supply power to the aircraft; one end of the cable being connected to the aircraft, and the other end being connected to a cable paying and retracting mechanism of the control cabinet; the cable comprising a first cable segment released outside the control cabinet and a second cable segment retracted inside the control cabinet; the control cabinet being used to perform the above-mentioned inspection method.

[0048] As can be seen from the technical solutions provided in the embodiments of this specification, the inspection method provided in the embodiments of this specification for an offshore wind farm inspection system can transmit a detection light signal to an aircraft via the optical fiber of a cable; receive a reflected light signal returned by the aircraft based on the detection light signal; calculate the phase difference between the reflected light signal and the detection light signal; obtain a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment; calculate the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference; and control the aircraft to perform an inspection based on the length of the first cable segment. Compared with existing methods, the cable can simultaneously provide a power transmission channel for the control cabinet and the aircraft, as well as data feedback on the length of the optical fiber in the cable outside the control cabinet. On the one hand, the power transmission channel provided by the cable can completely eliminate the limitations of the aircraft's battery life, eliminating the need for frequent return trips to replace batteries, reducing round-trip time, and significantly increasing the proportion of effective operating time. This can significantly shorten the time wind turbines are shut down due to faults or waiting for inspection confirmation, maximizing the wind farm's power generation hours. On the other hand, the cable is released outside the control cabinet according to the cable releasing and retracting mechanism, and according to the different refractive indices of the optical fibers in different cable segments inside and outside the control cabinet, the length of the first cable segment outside the control cabinet can be accurately fed back, and then the inspection range of the aircraft can be accurately controlled according to the length of the first cable segment outside the control cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0050] Figure 1 This is a structural diagram of an offshore wind farm inspection system provided in an embodiment of this specification;

[0051] Figure 2 This is a structural diagram of a control cabinet in an offshore wind farm inspection system provided by an embodiment of this specification;

[0052] Figure 3 This is a schematic diagram of the structure of a cable in an offshore wind farm inspection system provided by an embodiment of this specification;

[0053] Figure 4 This is a schematic diagram of the structure of an aircraft in an offshore wind farm inspection system provided by an embodiment of this specification;

[0054] Figure 5 This is a flow chart of an inspection method provided in an embodiment of this specification;

[0055] Figure 6 This is a schematic diagram of the structural composition of an inspection device provided in an embodiment of this specification.

[0056] Reference numerals in the above drawings:

[0057] 1. a control cabinet;

[0058] 11. a first power supply;

[0059] 12. an energy storage component;

[0060] 13. a patrol data storage component;

[0061] 14. a first control component;

[0062] 15. a cable winding and unwinding mechanism;

[0063] 2. a cable;

[0064] 21. an optical fiber;

[0065] 22. a power transmission wire;

[0066] 23. a tether component;

[0067] 3. an aircraft,

[0068] 31. a second power supply;

[0069] 32. an energy storage component;

[0070] 33. a second control component;

[0071] 34. a collection component. DETAILED DESCRIPTION

[0072] The technical solutions in the embodiments of the present specification will be described clearly and completely in combination with the drawings in the embodiments of the present specification. Obviously, the described embodiments are only some of the embodiments of the present specification, but not all the embodiments. Based on the embodiments in the present specification, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present specification.

[0073] It should be noted that the terms "first", "second", and the like in the present specification and claims and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present specification described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, device, product or equipment including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or equipment.

[0074] Figure 1 This is a structural diagram of an offshore wind farm inspection system provided in this manual.

[0075] In some embodiments, the offshore wind farm inspection system may include an aircraft 3, a cable 2 and a control cabinet 1; the cable 2 includes an optical fiber 21 and a transmission wire 22; the transmission wire 22 is used to supply power to the aircraft 3; one end of the cable 2 is connected to the aircraft 3, and the other end is connected to the cable releasing and retracting mechanism 15 of the control cabinet 1; the cable 2 includes a first cable segment released outside the control cabinet 1 and a second cable segment retracted into the control cabinet 1.

[0076] Reference Figure 1 As shown, the control cabinet 1 can supply power to the aircraft 3 via the power transmission wire 22 integrated in the cable 2 , and at the same time receive inspection data transmitted back by the aircraft 3 via the optical fiber 21 .

[0077] The control cabinet 1 can also adjust the inspection range of the aircraft 3 through the cable release and retraction mechanism 15 according to inspection requirements, thereby achieving full coverage and accurate inspection of wind turbines in offshore wind farms.

[0078] The cable 2 is a composite cable and may include an optical fiber 21 and a power transmission wire 22 .

[0079] The cable 2 includes a first cable section released outside the control cabinet 1 and a second cable section retracted into the control cabinet 1 .

[0080] The optical fiber 21 integrated in the cable 2 can transmit images and data (such as equipment status and fault signals) collected by the aircraft 3 to the control cabinet 1 in real time to achieve remote monitoring.

[0081] The power transmission line 22 integrated in the cable 2 can continuously supply power to the aircraft 3 under the control of the control cabinet 1 .

[0082] Aircraft 3 can be equipped with inspection equipment (such as cameras and sensors) to inspect wind turbines, cables and other facilities.

[0083] When carrying out specific inspection work, the aircraft 3 first takes off from near the control cabinet 1. The cable release and retraction mechanism 15 releases the cable 2 synchronously according to the climb and flight path of the aircraft 3. The power transmission line 22 continuously transmits electricity from the control cabinet 1 to the aircraft 3, so that it does not need to rely on the onboard battery. The optical fiber 21 establishes a real-time and stable communication link between the aircraft 3 and the control cabinet 1: the control instructions are sent from the control cabinet 1 to the aircraft 3. The status information, high-definition video, sensor data, etc. of the aircraft 3 are transmitted back to the control cabinet 1 in real time. The aircraft 3 performs inspection tasks on the wind turbine blades, towers, nacelles, etc. within the range allowed by the length of the cable 2. After the task is completed, the aircraft 3 returns and lands, and the cable release and retraction mechanism 15 retracts the cable 2.

[0084] Continuous power supply via cable 2 completely eliminates the limitations of drone 3's battery life, limiting the duration of inspection missions only to drone 3's mechanical reliability and mission planning. This allows for: more detailed and extended inspections of a single wind turbine, or continuous inspections of multiple turbines without interruption; eliminating the need for frequent battery replacements, reducing round-trip time; significantly improving the proportion of effective operating time; eliminating the need for interruptions due to battery replacements, allowing inspections of more targets or more comprehensive inspections of the same target in a single flight; and completing tasks that previously required multiple battery replacements with a single deployment, reducing the number of deployments. When sudden faults require inspection, the system responds more quickly, enabling immediate takeoff and extended hovering for observation. Efficient and rapid inspections can more quickly identify potential turbine faults or damage, and more comprehensive inspection data facilitates the development of more precise maintenance plans. Overall, this significantly reduces the time wind turbines spend downtime due to faults or awaiting inspection confirmation, maximizing the wind farm's generating hours.

[0085] Fiber-optic communications also offer significant advantages over wireless links (such as radio, 4G / 5G), including high bandwidth, low latency, strong resistance to electromagnetic interference, immunity to adverse weather conditions (such as rain and fog), and excellent confidentiality. They ensure the stable transmission of large amounts of data, such as high-definition video and laser point clouds, as well as the real-time and reliable delivery of control commands, particularly in complex electromagnetic and meteorological environments at sea. Physical cable connections can provide a means of containment or recovery in extreme situations (such as loss of control due to strong winds). A continuous power supply eliminates the risk of forced landings due to low battery levels.

[0086] In some embodiments, the control cabinet 1 may include a first power supply 11 , an energy storage component 12 , an inspection data storage component 13 , a first control component 14 and a cable releasing and retracting mechanism 15 .

[0087] Please refer to Figure 2 The first power supply 11 can supply power to the control cabinet 1 around the clock, including supplying power to the inspection data storage component 13 , the first control component 14 and the cable releasing and retracting mechanism 15 .

[0088] The energy storage component 12 can supply power to the aircraft 3 via the cable when performing inspection work.

[0089] The inspection data storage component 13 can store the inspection data of each wind turbine generator set in the offshore wind farm acquired by the aircraft 3 during inspection.

[0090] The cable releasing / retracting mechanism 15 can control the length of the cable released / retracted during inspection work, thereby controlling the inspection range of the aircraft 3 .

[0091] The first control component 14 can control the energy storage component 12 , the inspection data storage component 13 and the cable releasing and retracting mechanism 15 .

[0092] The specific inspection work can be divided into the preparation stage, take-off and cruise stage, detailed inspection stage, return and landing stage, and data post-processing stage.

[0093] During the preparation phase: the first power supply 11 is turned on to supply power to the entire control cabinet 1; the first control component 14 starts a self-test to confirm that all subsystems are normal; the energy storage component 12 is fully charged by the first power supply 11; and the aircraft 3 is powered on for a self-test.

[0094] During the takeoff and cruise phases: the first control component 14 instructs the takeoff or the aircraft 3 automatically executes the takeoff procedure; the first control component 14 instructs the cable releasing and retracting mechanism 15 to release the cable synchronously; the energy storage component 12 provides the main driving power for the aircraft 3 through the cable transmission conductor 22; the aircraft 3 flies according to the planned path and collects data; the collected data stream is transmitted to the inspection data storage component 13 of the control cabinet 1 through the optical fiber 21; the first control component 14 continuously performs flight control (adjusting attitude and heading according to feedback), energy management (monitoring energy storage discharge, and adjusting flight strategy when necessary), cable management (accurately calculating release length and maintaining tension) and data monitoring.

[0095] During the detailed inspection phase: the aircraft 3 hovers or flies around at low speed at the target wind turbine location in the offshore wind farm; the cable release and retraction mechanism 15 performs fine adjustments to maintain appropriate tension and position; and the sensor performs high-precision data acquisition (such as high-definition photography and laser scanning).

[0096] During the return and landing phase: the mission is completed or an instruction is received, and the aircraft 3 returns; the first control component 14 instructs the cable releasing and retracting mechanism 15 to synchronously retract the cable to guide the aircraft 3 back.

[0097] In the data post-processing stage: the aircraft 3 lands and the system is on standby; the data stored in the inspection data storage component 13 is used to analyze, generate reports, and formulate maintenance plans.

[0098] The coordinated operation of the first power source 11 and the energy storage component 12 ensures the continuous operation of the aircraft 3. The first control component 14 integrates multiple functions, including flight control, energy management, cable control, data management, and safety monitoring, enabling highly automated and complex task execution. Furthermore, the dedicated inspection data storage component 13 ensures the lossless acquisition of inspection data.

[0099] In some embodiments, the cable 2 may include an optical fiber 21 , a power transmission conductor 22 , and a mooring member 23 wrapping the optical fiber 21 and the power transmission conductor 22 .

[0100] Please refer to Figure 3 The optical fiber 21 can be used to provide a transmission channel for the optical signal, and the length of the optical fiber 21 in the cable section released outside the control cabinet 1 / recovered inside the control cabinet 1 can be determined by the propagation of the optical signal.

[0101] The power transmission line 22 can serve as a channel for providing power supply to the aircraft 3 .

[0102] The optical fiber 21 can also transmit the signal generated by the aircraft 3 to the control cabinet 1 .

[0103] The optical fiber 21 can also transmit instructions from the control cabinet 1 to the aircraft 3 .

[0104] In some embodiments, the tethering component 23 may provide a physical connection between the aircraft 3 and the control cabinet 1 .

[0105] The tethering member 23 provides the primary mechanical strength between the aircraft 3 and the control cabinet 1, supporting the weight of the aircraft 3, wind loads, maneuvering overloads, and the weight and tension of the cable itself. The tethering member 23 encases and protects the optical fiber 21 and power transmission wire 22 within it, protecting them from damage such as stretching, squeezing, bending, abrasion, seawater erosion, and UV aging.

[0106] The mooring member 23 can be made from high-strength fibers such as Kevlar, ultra-high molecular weight polyethylene (Dyneema / Spectra), or carbon fiber. These materials offer an extremely high strength-to-weight ratio (lightweight yet strong), excellent tensile strength, and fatigue resistance. The outermost layer of the mooring member 23 can be coated with a wear-resistant, weather-resistant, salt spray-resistant, and UV-resistant polymer material (such as polyurethane, specialty nylon, or Hytrel) to minimize wind resistance and friction during deployment and retraction.

[0107] Cable 2 integrates four major functions: energy flow (power), information flow (fiber optic data), length feedback (fiber optic length measurement), and mechanical force flow (tethering), significantly simplifying system deployment and airside complexity. Specifically, it leverages the inherent properties of optical fiber 21 for real-time, high-precision, sensor-free length measurement, providing critical input for flight range determination. The wired fiber design significantly improves communication reliability. The high-strength design with tethering component 23 not only provides a physical connection between control cabinet 1 and aircraft 3, but also ensures sufficient strength, durability, and protection for fragile internal components in the harsh offshore environment and complex flight paths.

[0108] In some embodiments, the aircraft 3 may include a second power source 31 , a power storage component 32 , a second control component 33 and a collection component 34 .

[0109] Please refer to Figure 4 The energy storage component 12 in the control cabinet 1 can transmit electricity to the second power supply 31 through the power transmission wire 22 of the cable. The second power supply 31 can supply power to the storage component 32, the second control component 33 and the collection component 34.

[0110] The power storage component 32 can be used to provide a temporary power supply for the aircraft 3 when the cable breaks or the second power source 31 fails.

[0111] The second control component 33 can receive the flight control instructions from the first control component 14 and control the flight of the aircraft 3 according to the flight control instructions.

[0112] The collection component 34 can obtain inspection data of each wind turbine in the offshore wind farm during inspection work.

[0113] Through the optical fiber 21 in the cable 2, the second control unit 33 receives real-time flight control commands (such as waypoints, speed, altitude, and attitude) from the first control unit 14 in the control cabinet 1. Using pre-set sensors, the second control unit 33 accurately senses its own state and environment. Based on the received commands and its own sensed state, the second control unit 33 calculates and outputs control signals to the aircraft 3's motors (for speed regulation), servos, and other actuators, precisely controlling the aircraft's attitude, position, and speed. The second control unit 33 also continuously transmits key status information (such as position, altitude, speed, attitude, battery level, fault codes, and sensor status) back to the control cabinet 1 via the optical fiber 21 in real time. When the power storage unit 32 takes over, the second control unit 33 can execute pre-set emergency strategies (such as automatic return, hovering for assistance, and emergency landing).

[0114] The data collection component 34 can be equipped with a variety of sensors, including visible light cameras, infrared thermal imagers, lidar, acoustic sensors / ultrasonic detectors, and gas sensors, to enable comprehensive inspections of wind turbines in offshore wind farms. Specifically, visible light cameras can detect blade surface damage (cracks, corrosion, lightning strikes), tower rust, loose bolts, and oil leaks. Infrared thermal imagers can detect temperature field anomalies caused by overheating of electrical connections (junction boxes, transformers), abnormal temperature rise in gearboxes / bearings, and internal blade defects (debonding). Lidar can generate high-precision point clouds to measure blade deformation, detect tower verticality, and quantify blade leading edge erosion. Acoustic sensors / ultrasonic detectors can detect abnormal noise (bearing damage, gear wear, and abnormal blade aerodynamic noise). Gas sensors can detect specific gases produced by oil leaks.

[0115] The design of the second power supply 31 and the power storage component 32 ensures the unlimited endurance benefits of tethered power while effectively preventing potential tethering system risks—crashes caused by cable or power outages. Furthermore, the combination of a sophisticated second control component 33 and a diverse data collection component 34 enables long-term, high-quality, and safe inspections of wind turbines in harsh offshore environments.

[0116] Figure 5A flow chart of a method for inspection is provided for the embodiments of the present specification. In particular implementation, the following steps are included:

[0117] S501: transmitting the probe light signal to the aircraft through the optical fiber of the cable.

[0118] In some embodiments, the light signal generated by the laser emitter in the control cabinet is intensity-modulated based on the laser phase method to obtain a modulated light signal; and the generated modulated light signal is used as the probe light signal.

[0119] The laser emitter in the control cabinet 1 can generate a light signal, which can be intensity-modulated using a microwave signal and used as a probe light signal, and then the probe light signal can be transmitted to the aircraft 3 through the optical fiber 21 of the cable 2. Specifically, the first control component 14 in the control cabinet 1 can generate a stable and modulated coherent light signal through a specific optoelectronic conversion device (such as a laser diode or a light-emitting diode). Then a high-frequency electrical signal of GHz level can be generated by a microwave signal source, and a high-speed optical modulation device such as a Mach-Zehnder modulator or an electro-absorption modulator can be used to load the microwave signal onto the optical carrier to achieve intensity modulation. The light intensity of the modulated light signal linearly responds to the amplitude change of the microwave signal, thereby forming a probe light signal containing microwave characteristic information. After obtaining the probe light signal, the first control component 14 can transmit it to the second control component 33 in the aircraft 3 through the optical fiber 21 of the cable 2.

[0120] S502: receiving the reflected light signal returned by the aircraft according to the probe light signal.

[0121] In some embodiments, after receiving the probe light signal sent by the first control component 14, the second control component 33 in the aircraft 3 can generate a reflected light signal based on the probe light signal. The second control component 33 can transmit the reflected light signal to the first control component 14 through the optical fiber 21 in the cable 2. The first control component 14 can receive the reflected light signal transmitted by the second control component 33.

[0122] S503: calculating the phase difference between the reflected light signal and the probe light signal.

[0123] In some embodiments, the probe light signal is converted into a first electrical signal; the reflected light signal is converted into a second electrical signal; a fundamental frequency signal in the second electrical signal is extracted; and the phase difference of the fundamental frequency signal relative to the first electrical signal is calculated.

[0124] The reflected light signal can be optoelectronically converted, and a fundamental frequency signal in the optoelectronically converted reflected light signal can be extracted. The fundamental frequency signal can be shown in the following formula:

[0125] ;

[0126] Where, represents the optical carrier amplitude, represents the modulation intensity, represents the angular frequency of the optical carrier, represents the angular frequency of the modulating signal, Indicates the fixed delay of optical signal transmission in optical fiber. Indicates the time it takes for an optical signal to travel through an optical fiber.

[0127] The detection light signal can also be photoelectrically converted. The detection light signal after photoelectric conversion can be expressed as follows:

[0128] ;

[0129] Where, represents the optical carrier amplitude, represents the modulation intensity, represents the angular frequency of the optical carrier, Indicates the angular frequency of the modulating signal.

[0130] In some embodiments, the baseband signal and the detection light signal after photoelectric conversion can be input into a digital correlator or an orthogonal demodulation module, and the instantaneous phase difference can be obtained by calculating the inverse tangent function.

[0131] Specifically, when the baseband signal and the optically converted detection signal are input into a digital correlator, the system calculates the cross-correlation function of the two signals to determine the time delay, which is linearly related to the phase difference. The quadrature demodulation module (I / Q demodulation) multiplies the input signal by two orthogonal local carriers to produce an in-phase component (I channel) and a quadrature component (Q channel).

[0132] Taking I / Q demodulation as an example, for the baseband signal and the detection light signal after photoelectric conversion , then after orthogonal demodulation: I channel can output: , Q-path can output: .in is the gain coefficient of the quadrature demodulation module, 、 Baseband signal and the detection light signal after photoelectric conversion The amplitude of the inverse tangent function , the instantaneous phase difference between the two signals can be obtained The phase difference can be converted into a vector angle in a rectangular coordinate system through the inverse tangent function, avoiding the difficulty of directly measuring the phase of high-frequency signals. At the same time, digital signal processing technology can effectively suppress noise interference.

[0133] In some embodiments, a zero-crossing detection method may also be used, where a high-speed comparator records the time difference between the zero-crossing points of the baseband signal and the detection light signal after photoelectric conversion, and the difference is converted into a phase difference in combination with clock counting.

[0134] The baseband reference signal and the photoelectrically converted detection light signal can be connected to a high-speed comparator (such as the THS3091 chip, which has a rise time of less than 1ns). The comparator compares the signal level with the zero threshold in real time, converting the analog signal's zero crossing into a TTL-level pulse transition. For example, when a sine wave transitions from the negative half-cycle to the positive half-cycle, the comparator outputs a rising edge, and vice versa. These pulse edges precisely mark the signal's zero crossing moment.

[0135] In order to achieve quantitative calculation of phase difference, a high-frequency clock can be introduced as a time reference. Assuming the clock frequency is 1 GHz, when the zero-crossing time difference between the fundamental frequency signal and the detection light signal is recorded by the counter as When the phase difference is It is deduced that is the signal frequency. Taking a 100MHz baseband signal as an example, a 1ns time difference corresponds to a 0.036° phase change. This quantitative relationship means that the clock counting accuracy directly determines the phase measurement resolution.

[0136] In some embodiments, when calculating the phase difference, the phase drift of the optoelectronic device can be dynamically corrected through temperature sensor feedback.

[0137] In the aforementioned phase difference measurement system, temperature fluctuations can cause changes in the physical parameters of optoelectronic components (such as lasers, modulators, and detectors), which can introduce phase drift and affect measurement accuracy. By integrating a temperature sensor and establishing a dynamic correction model, this drift can be effectively suppressed. Specifically, a temperature sensor (such as a fiber Bragg grating or thermistor) can monitor the temperature changes of key components in real time and feed this temperature data back to the control unit. The control unit then uses a pre-established temperature-phase drift model to compensate for the measured phase difference in real time.

[0138] Taking the laser as an example, the change of its output wavelength with temperature will lead to the error of optical path difference calculation, thus causing phase deviation. Assuming that the temperature coefficient of the laser is 10pm / ℃, when the operating temperature fluctuates by 5℃, the wavelength changes by 50pm. For the 1550nm optical signal, according to the pre-built temperature-phase drift model, the corresponding phase drift can be obtained to be about 0.42rad / km. At this time, after the temperature sensor detects the temperature change, the control system will adjust the temperature according to the formula ( The phase correction amount is calculated based on the optical path length and is deducted from the measured phase difference.

[0139] S504: Obtain a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment.

[0140] In some embodiments, a first refractive index of an optical fiber in a first cable segment and a second refractive index of an optical fiber in a second cable segment may be obtained.

[0141] When cable 2 is dynamically released or retracted by cable release / retraction mechanism 15, the refractive index profile of the optical fibers within cable 2 changes due to mechanical stress and temperature gradients caused by the external environment. Therefore, obtaining the first refractive index of the optical fibers in the first cable segment released outside control cabinet 1 and the second refractive index of the optical fibers in the second cable segment retracted inside control cabinet 1 is crucial for accurately calculating the subsequent lengths of the optical fibers in the first and second cable segments.

[0142] It can be assumed that the initial refractive index of the optical fiber in cable 2 is .

[0143] The second cable segment is located inside the control cabinet 1. Therefore, it can be considered that it will not be affected by the corresponding mechanical stress when the cable release and retraction mechanism 15 dynamically releases or retracts the cable and the temperature gradient change caused by the external environment. That is, the second refractive index of the second cable segment is equal to the initial refractive index:

[0144] ;

[0145] As for the first cable segment, the axial strain and transverse strain generated by the mechanical stress when the cable releasing and retracting mechanism 15 dynamically releases or retracts the cable 2 can be determined by sensors external to the cable 2 .

[0146] In some embodiments, based on the photoelastic effect, the change in refractive index caused by mechanical stress can be calculated using the following formula:

[0147] ;

[0148] Where, 、 represents the photoelastic coefficient of the optical fiber material, It represents the axial strain of the optical fiber caused by mechanical stress. Indicates the transverse strain of the optical fiber caused by mechanical stress.

[0149] The photoelastic effect can be considered a direct coupling of fiber stress and optical properties, with its refractive index change linearly related to mechanical stress. Therefore, based on the photoelastic effect, the refractive index changes corresponding to the axial and transverse strains generated by mechanical stress can be accurately and quickly determined.

[0150] In an offshore environment, the temperature inside the control cabinet 1 can be considered constant. When the cable 2 is dynamically released or recovered by the cable releasing and retracting mechanism 15, the first cable segment outside the control cabinet 1 is exposed to the seawater / air environment, and the temperature difference between the inside and outside of the control cabinet 1 can be obtained.

[0151] In some embodiments, based on the thermo-optic effect, the change in refractive index caused by temperature difference can be calculated using the following formula:

[0152] ;

[0153] Where, represents the thermo-optical coefficient of the optical fiber, Indicates temperature difference.

[0154] The thermo-optic effect can be considered the physical coupling of fiber temperature and optical properties, with its refractive index changing linearly with fiber temperature. Therefore, based on the thermo-optic effect, the refractive index change caused by the temperature difference between the inside and outside of the control cabinet 1 can be accurately and quickly determined.

[0155] In some embodiments, based on the change in refractive index caused by mechanical stress and the change in refractive index caused by temperature difference, the following formula can be used to determine the first refractive index of the optical fiber in the first cable segment:

[0156] .

[0157] By considering the effects of mechanical stress and temperature gradient changes caused by the external environment on the refractive index of the optical fiber when the cable releasing and retracting mechanism 15 dynamically releases or retracts the cable 2, the first refractive index of the optical fiber in the first cable segment can be accurately calculated, laying a data foundation for the subsequent accurate calculation of the length of the optical fiber in the first cable segment.

[0158] Temperature sensors can be installed at regular intervals on the outer wall of cable 2. This allows the temperature difference at different axial locations within the first cable segment to be measured, thereby constructing a temperature difference distribution function along the axial direction of the first cable segment. This temperature difference distribution function more accurately reflects the temperature difference distribution of the entire first cable segment, allowing the change in refractive index caused by this temperature difference distribution to be more precisely calculated.

[0159] In some embodiments, a temperature difference distribution function along the axial direction of the first cable segment can be obtained. Based on the temperature distribution function, the change in refractive index caused by the temperature difference can be calculated using the following formula:

[0160] ;

[0161] Where, represents the thermo-optical coefficient of the optical fiber, represents the temperature difference distribution function along the axial direction of the first cable segment.

[0162] Based on the axial temperature difference distribution function of the first cable segment, the refractive index change caused by the temperature difference at each axial point of the first cable segment can be calculated more accurately. By combining the refractive index change at each axial point of the first cable end, the overall refractive index change of the first cable segment caused by the temperature difference distribution can be accurately calculated.

[0163] In some embodiments, the photoelastic effect and thermal expansion stress effect of the coupled optical fiber can be used to calculate the change in refractive index caused by mechanical stress using the following formula:

[0164] ;

[0165] Where, 、 represents the photoelastic coefficient of the optical fiber material, It represents the axial strain of the optical fiber caused by mechanical stress. It represents the transverse strain of the optical fiber caused by mechanical stress. represents the thermal expansion coefficient of the optical fiber, represents the temperature difference distribution function along the axial direction of the first cable segment.

[0166] By coupling the photoelastic effect and thermal expansion stress effect of the optical fiber, the refractive index change caused by mechanical stress can be further corrected based on the temperature difference change to obtain a more accurate refractive index change.

[0167] S505: Calculate the length of the first cable segment according to the first refractive index, the second refractive index and the phase difference.

[0168] In some embodiments, a linear variation model of the phase difference and the optical fiber length is constructed based on a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment.

[0169] Phase difference can be considered as the phase mapping of optical path difference. Specifically, the nature of light is electromagnetic wave, and its phase change is strictly linear with the propagation optical path. The light travels one optical path The vibration phase of the electric field or magnetic field will change The optical path can be the product of the physical length of light propagating in the medium and the refractive index of the medium. The optical path can reflect the phase accumulation effect of light propagating in the medium, because the phase change of light is proportional to the optical path of propagation. I will not go into details here. Therefore, when light propagates in different media, the optical path difference When It can be calculated by the following formula:

[0170] ;

[0171] That is, the phase difference can be considered to be the "number of cycles" of the optical path difference relative to the wavelength multiplied by , which can reflect the cumulative differences in light field vibrations in time and space.

[0172] When the cable 2 is dynamically released or recovered by the cable releasing and retracting mechanism 15, the cable 2 can be divided into a first cable segment outside the control cabinet 1 and a second cable segment inside the control cabinet 1. The total length of the optical fiber in the cable 2 can be set to , the length of the optical fiber 21 in the first cable segment is , then the length of the optical fiber in the second cable segment is .

[0173] Based on the length of the optical fiber in the first cable segment, the first refractive index of the optical fiber in the first cable segment, the length of the optical fiber in the second cable segment, and the first refractive index of the optical fiber in the second cable segment, the optical path difference generated when the detection light signal and the reflected light signal propagate in the optical fiber can be calculated using the following formula:

[0174] ;

[0175] The above optical path difference can be substituted into the phase difference formula to obtain a linear variation model of the phase difference and fiber length for optical fibers with different refractive indices:

[0176] .

[0177] In some embodiments, the total length of the optical fiber in the cable is obtained; and the length of the optical fiber in the first cable segment is calculated using the linear variation model based on the first refractive index, the second refractive index, the phase difference, and the total length of the optical fiber in the cable.

[0178] According to the above linear variation model of phase difference and fiber length, the calculation formula of how fiber length is affected by phase difference can be inverted, that is, the following can be obtained:

[0179] ;

[0180] The phase difference is expressed as In this case, we can further obtain:

[0181] ;

[0182] The total length of the optical fiber 21 in the cable 2 can be obtained , and then the phase difference can be , first refractive index and the second refractive index Use formulas accurately and quickly when informed Calculate the length of the optical fiber in the first cable segment.

[0183] By incorporating the refractive index changes of the optical fiber caused by deformation and temperature changes into the linear change model of phase difference and optical fiber length, the length of the optical fiber in the first cable segment can be accurately calculated in real time, laying a good foundation for the subsequent precise control of the inspection range of aircraft 3.

[0184] In some embodiments, the length of the first cable segment is determined based on the length of the optical fiber in the first cable segment. For each release cycle of the cable release / retraction mechanism 15, the length of the optical fiber in the first cable segment at the end of the release can be determined. The optical fiber has some curvature within the cable 2, so its actual length is slightly greater than the length of the mooring component in the first cable segment. The length of the first cable segment can be calculated based on the length of the optical fiber and the degree of curvature of the optical fiber within the first cable segment.

[0185] S506: Control the aircraft to perform inspection according to the length of the first cable segment.

[0186] In some embodiments, the coverage area of ​​each wind turbine in the offshore wind farm can be obtained; based on the length of the optical fiber in the first cable segment, the multiple wind turbines that can be inspected by the aircraft are determined; and based on the Z-shaped search algorithm, the inspection route of the multiple wind turbines that can be inspected by the aircraft is determined.

[0187] From a hardware perspective, the structural dimensions of the wind turbine itself, particularly the rotational diameter of the blades, directly determine the presence of a zone of airflow disturbance within a certain range around it. This area is inaccessible to aircraft 3, thus constituting a fundamental limitation on the coverage area. Therefore, a geographic information system (GIS) can be used, combined with the precise coordinate data of the wind turbines, to construct a three-dimensional spatial model, visually mapping the coverage area of ​​each wind turbine excluding the airflow disturbance zone. Furthermore, field test flights can be conducted to collect actual flight data from aircraft 3 under different meteorological conditions, allowing the coverage area of ​​each wind turbine to be revised and improved to ensure accuracy.

[0188] For each release process of the cable retracting mechanism 15, the length of the optical fiber in the first cable segment at the end of the release can be obtained. The optical fiber has a certain degree of curvature in the cable 2, so the actual length of the optical fiber is slightly greater than the length of the mooring component in the first cable segment. Based on the length of the optical fiber and the degree of curvature of the optical fiber in the first cable segment, the length of the mooring component in the first cable segment can be calculated. The length of the mooring component in the first cable segment can represent the maximum flight distance of the aircraft 3 after each release process. Based on the maximum flight distance of the aircraft 3 after each release process and the maximum flight distance of the aircraft 3 after the previous release process, the number of wind turbines that can be inspected by the aircraft 3 after each release process can be determined. Specifically, the maximum flight distance of the aircraft 3 after the previous release process can be used as the current minimum flight distance, and the maximum flight distance of the aircraft 3 after the current release process can be used as the current maximum flight distance. Based on the coverage area of ​​each wind turbine in the offshore wind farm, multiple wind turbines whose coverage areas are completely between the current minimum flight distance and the current maximum flight distance can be screened.

[0189] The key idea behind using a Z-shaped search algorithm to determine the inspection routes for multiple wind turbines that can be inspected by aircraft 3 is to inspect each wind turbine sequentially along a Z-shaped trajectory. This minimizes duplication of flight paths and improves inspection efficiency. In practice, the inspectable wind turbines are first numbered and arranged in rows and columns to form a matrix layout. Starting with the wind turbine in the top left corner of the matrix, the odd-numbered rows are inspected from left to right, while the even-numbered rows are inspected from right to left, until all inspectable wind turbines have been traversed.

[0190] In some embodiments, a heuristic algorithm may be used to adjust the generated inspection route based on the minimum turning radius of the aircraft.

[0191] When the aircraft 3 is performing an inspection mission, if the turning radius is too small, the fuselage will be subjected to excessive aerodynamic loads, which may not only damage the components of the aircraft 3 but also easily cause the risk of loss of control; if the turning radius is too large, it will increase the additional flight distance and time cost.

[0192] The minimum turning radius parameter of aircraft 3 can be obtained, and this value can be determined by the model, power system and aerodynamic design of aircraft 3. In the Z-shaped path, each turning node is a focus of optimization. For a straight path between adjacent wind turbines, the turning trajectory needs to be planned in advance before approaching the turning node. Taking two adjacent wind turbines A and B as an example, when aircraft 3 flies from A to B and is about to turn to the next target unit, it will draw an arc with B as the center and the minimum turning radius as the radius as the transition path, so that aircraft 3 can smoothly change the flight direction.

[0193] In addition, due to the possible irregularities in the layout of wind turbines in offshore wind farms, the space of some turning nodes is limited. Therefore, by introducing heuristic algorithms, such as genetic algorithms or simulated annealing algorithms, the inspection order of wind turbines can be dynamically adjusted while meeting the minimum turning radius. For example, in a certain local area, if turning is difficult according to the original Z-shaped path, the genetic algorithm can be used to try to exchange the inspection order of some units and regenerate the path. While ensuring that all target units are covered, it is ensured that each turn meets the minimum turning radius requirement. Through such optimization and adjustment, the safe flight of the aircraft 3 under complex paths can be guaranteed, and the energy loss caused by unreasonable turns can be effectively reduced, further improving the overall efficiency of offshore wind farm inspections.

[0194] In some embodiments, the aircraft is controlled to perform inspections based on the length of the first cable segment.

[0195] Aircraft 3 can be powered by power lines 22 of cable 2 and inspection commands can be sent via optical fibers 21 of cable 2, enabling aircraft 3 to inspect each wind turbine within its inspection range and acquire multimodal inspection data for each wind turbine. Specifically, the visible light camera of aircraft 3's acquisition component 34 can capture visible light images of each wind turbine to inspect for blade surface damage (cracks, corrosion, lightning strikes), tower corrosion, loose bolts, oil leaks, and more. The infrared thermal imager of aircraft 3's acquisition component 34 can capture infrared images of each wind turbine to detect temperature field anomalies caused by overheating of electrical connections (junction boxes, transformers), abnormal temperature rise in gearboxes / bearings, and internal blade defects (debonding). The lidar of aircraft 3's acquisition component 34 can capture point clouds of each wind turbine to measure blade deformation, detect tower verticality, and quantify blade leading edge corrosion. The acoustic sensor / ultrasonic detector of the acquisition component 34 of aircraft 3 can acquire acoustic wave data from each wind turbine to detect abnormal noise (such as bearing damage, gear wear, and abnormal blade aerodynamic noise). The gas sensor of the acquisition component 34 of aircraft 3 can also acquire gas monitoring data from each wind turbine to detect specific gases produced by oil leaks.

[0196] In some embodiments, based on a preset multimodal feature extraction model, feature vectors of inspection data of multiple modes corresponding to each wind turbine in an offshore wind farm can be extracted; based on a hierarchical fusion strategy, feature vectors of inspection data of each mode can be fused; based on a preset offshore wind turbine fault knowledge graph, fault reasoning can be performed on the fused feature vectors to obtain fault diagnosis results; and based on the fault diagnosis results, a detection report can be generated.

[0197] The pre-set multimodal feature extraction model can leverage deep learning models to extract features from data of different modalities. Specifically, for visible light images, a convolutional neural network (CNN) can be used to extract visual features such as blade surface texture and tower corrosion. For infrared images, a modified ResNet network can be used to capture thermal features of areas with abnormal temperatures. For lidar point cloud data, a PointNet++ network can be used to extract 3D geometric features. For acoustic wave data, Fourier transforms and LSTM networks can be used to extract frequency and time series features. For gas monitoring data, a fully connected neural network can be used to extract concentration change features.

[0198] A layered fusion strategy can be employed to concatenate feature vectors from different modalities at the feature level to form a fused feature vector. An attention mechanism can also be used to assign weights to features from different modalities, highlighting key features. For example, when detecting leaf damage, the weight of visible light image features can be increased; when detecting overheated electrical connections, the weight of infrared image features can be emphasized, achieving deep fusion of multimodal data.

[0199] A knowledge graph for offshore wind turbine faults can be constructed by integrating knowledge about equipment structure, operating principles, and historical failure cases. The fused feature vectors can be fed into a knowledge graph inference engine, where fault inference can be performed using a graph neural network (GNN). For example, a blade crack can be analyzed by combining the shape and size characteristics of the crack in visible light images with the temperature anomalies that may occur at the crack site in infrared images. The knowledge graph can then be used to search for relevant fault patterns and determine the fault type, severity, and development trend.

[0200] Based on the fault diagnosis results, natural language generation technology can be used to automatically generate an inspection report. This report can include basic wind turbine information, a summary of test data, the fault diagnosis conclusion, and a visualization of the fault location (combining visible light images and point cloud data). Furthermore, visual charts can be used to intuitively present the analysis results of multimodal data, such as infrared temperature distribution cloud maps and acoustic spectrum graphs, making the report more readable.

[0201] In some embodiments, based on reinforcement learning, a decision model can be constructed with at least parameters such as fault type, severity, and repair cost as constraints; and based on the fault diagnosis structure, the decision model is used to generate detection recommendations.

[0202] Fault types can be categorized across multiple dimensions, including mechanical, electrical, and corrosion failures. Each type of fault corresponds to a distinct maintenance strategy. Severity is quantitatively assessed using sensor-generated data such as vibration, temperature, and wear, and can be categorized as mild, moderate, or severe, directly influencing the urgency and complexity of the maintenance strategy. Repair costs encompass not only direct costs like component replacement and manual labor, but also indirect costs like production losses caused by downtime. These interrelated parameters create a complex constraint space within which reinforcement learning algorithms can be used to continuously explore. Through an iterative process of "state (fault type, severity, and repair cost, etc.) - action (maintenance strategy) - reward (minimizing total repair cost)," the optimal maintenance strategy is gradually formed.

[0203] By simulating the effectiveness of different maintenance strategies, the optimal maintenance plan can be learned. For example, for minor blade surface corrosion, on-site coating repair can be recommended; for severe bearing damage, downtime and component replacement can be recommended. The repair time window and required resource list are provided to form targeted inspection recommendations.

[0204] By combining multimodal data fusion, knowledge graphs, and reinforcement learning, we can achieve intelligent management of the entire process, from data collection to detection recommendations. Compared with traditional methods, this method can more comprehensively and accurately diagnose wind turbine faults, improve the timeliness and reliability of fault diagnosis, and provide strong support for the efficient operation and maintenance of offshore wind farms.

[0205] In some embodiments, the total length of the cable and the total length of the optical fiber in the cable can be obtained; if the length of the optical fiber in the first cable segment is equal to the total length of the cable, or the length of the optical fiber in the first cable segment is equal to the total length of the optical fiber in the cable, the cable is stopped from being released; if the length of the optical fiber in the second cable segment is equal to the total length of the cable, or the length of the optical fiber in the second cable segment is equal to the total length of the optical fiber in the cable, the cable is stopped from being retracted.

[0206] The cable retracting mechanism 15 can be equipped with a tension sensor and an angle sensor. The tension sensor, mounted on the fixed end of the cable, monitors the cable's stress in real time. An abnormally high tension may indicate cable jamming or overstretching. The angle sensor, mounted on the drum's rotating shaft, assists the encoder in more accurately determining the drum's rotation angle, avoiding counting errors caused by slippage.

[0207] Length calculations can be corrected using historical data comparison and trend analysis. The system stores the last 10 cable payout / retrieval lengths and corresponding operating conditions (such as weather, wind speed, and system load). A correction process is triggered when the current calculated length deviates by more than 10% from historical data under similar operating conditions. By analyzing the performance of each sensor in historical data, current measurement data is corrected to ensure accurate calculations.

[0208] Multiple warning thresholds can be set to provide alerts for cable release / retrieval length. A Level 1 warning is triggered when the cable reaches 80% of the set maximum length, with the system emitting audible and visual alerts. At 90%, a Level 2 warning is triggered, automatically reducing the cable release / retrieval speed. At 100% or any abnormal length change (such as a sudden shortening or elongation exceeding 5%), a Level 3 warning is triggered, immediately halting the cable release / retrieval operation and locking the system to prevent further damage.

[0209] By introducing historical data comparison and trend analysis to correct the length calculation results, and setting multi-level warning thresholds, the cable length of the cable releasing and retracting mechanism 15 can be accurately judged and controlled, effectively preventing the system from being damaged due to excessive releasing or retracting, and ensuring the stable operation of the offshore wind farm inspection system.

[0210] In some embodiments, the phase difference of the baseband signal relative to the first electrical signal may be calculated using the following formula: Where, represents the angular frequency of the optical carrier, represents the angular frequency of the modulating signal, Indicates the fixed delay of optical signal transmission in optical fiber. Indicates the time it takes for an optical signal to travel through an optical fiber.

[0211] The detection light signal after photoelectric conversion can be expressed as follows:

[0212] ;

[0213] Where, represents the optical carrier amplitude, represents the modulation intensity, represents the angular frequency of the optical carrier, Indicates the angular frequency of the modulating signal.

[0214] When light travels a certain distance in the optical fiber and then reflects back to the receiving end, its expression becomes:

[0215] ;

[0216] Where, represents the optical carrier amplitude, represents the modulation intensity, denotes the angular frequency of the optical carrier, denotes the angular frequency of the modulation signal, denotes the fixed time delay of the optical signal in the optical fiber, denotes the time of the optical signal in the optical fiber.

[0217] It can be assumed that The phase of the received optical signal (base frequency signal) at time t is:

[0218] ;

[0219] The phase of the reference light is:

[0220] ;

[0221] According to the phase of the received optical signal and the phase of the reference light, the phase difference can be obtained:

[0222] ;

[0223] Considering that is a constant term, so further can be obtained:

[0224] ;

[0225] For The phase difference at time t is , then The phase difference at time t can be expressed as:

[0226] ;

[0227] In the formula, denotes the angular frequency of the optical carrier, denotes the angular frequency of the modulation signal, denotes the fixed time delay of the optical signal in the optical fiber, denotes the time of the optical signal in the optical fiber.

[0228] Based on the formula , the phase difference of the base frequency signal relative to the photoelectric converted probe light signal can be determined in real time and accurately, which lays a data foundation for the subsequent length calculation of the optical fiber in the first cable segment.

[0229] As can be seen from the above, the inspection method for an offshore wind farm inspection system provided in the embodiments of this specification can transmit a detection light signal to an aircraft via the optical fiber of a cable; receive a reflected light signal returned by the aircraft based on the detection light signal; calculate the phase difference between the reflected light signal and the detection light signal; obtain the first refractive index of the optical fiber in the first cable segment and the second refractive index of the optical fiber in the second cable segment; calculate the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference; and control the aircraft to perform an inspection based on the length of the first cable segment. Compared with existing methods, the cable can simultaneously provide a power transmission channel for the control cabinet and the aircraft, as well as data feedback on the length of the optical fiber in the cable outside the control cabinet. On the one hand, the power transmission channel provided by the cable can completely eliminate the limitations of the aircraft's battery life, eliminating the need for frequent return trips to replace batteries, reducing round-trip time, and significantly increasing the proportion of effective operating time. This can significantly shorten the time wind turbines are shut down due to faults or waiting for inspection confirmation, maximizing the wind farm's power generation hours. On the other hand, the cable is released outside the control cabinet according to the cable releasing and retracting mechanism, and according to the different refractive indices of the optical fibers in different cable segments inside and outside the control cabinet, the length of the first cable segment outside the control cabinet can be accurately fed back, and then the inspection range of the aircraft can be accurately controlled according to the length of the first cable segment outside the control cabinet.

[0230] The following introduces a specific scenario example of the embodiment of this specification.

[0231] In some embodiments, a release instruction is transmitted to a cable releasing and retracting mechanism to release the cable; based on the detection light signal, a take-off instruction is transmitted to an aircraft through the optical fiber of the cable, so that the aircraft takes off as the cable is released; the offshore wind farm is divided into multiple detection areas; the minimum length of the first cable segment that the aircraft can inspect in each detection area is determined; if the length of the first cable segment is equal to the minimum length, a pause instruction is transmitted to the cable releasing and retracting mechanism to stop releasing the cable; based on the detection light signal, an inspection instruction is transmitted to the aircraft through the optical fiber of the cable, so that the aircraft stops taking off as the cable stops being released; an inspection route is set according to the detection area corresponding to the length of the first cable segment; according to the inspection route, the wind turbines in the detection area are inspected; the inspection data of the aircraft in the detection area is received; and the above steps are iteratively performed until the aircraft completes the inspection of all detection areas of the offshore wind farm.

[0232] By transmitting aircraft-related control commands via the detection optical signal, the system achieves functional multiplexing of aircraft control commands and first cable segment length detection. Furthermore, by transmitting cable release and inspection data via optical fiber at different times, time-division multiplexing of optical fiber transmission is achieved, significantly improving the control efficiency of the offshore wind farm inspection system and the scheduling efficiency of optical fiber resources.

[0233] The control cabinet can generate a release command and transmit it to the cable release and retraction mechanism to release the cable. Simultaneously, the control cabinet can generate a takeoff command and encode it into a detection light signal through modulation techniques. The control cabinet can transmit the detection light signal carrying the takeoff command to the aircraft via the cable's optical fiber. After receiving the detection light signal, the aircraft can use demodulation techniques to separate the takeoff command from the detection light signal. This allows the aircraft to control its ascent based on the takeoff command and generate a corresponding reflected light signal based on the detection light signal. Upon receiving the reflected light signal from the aircraft, the control cabinet can calculate the length of the first cable segment in real time.

[0234] Furthermore, based on the location of the offshore wind farm inspection system (e.g., coordinates X0, Y0, Z0) and the distribution of the wind turbine array in the offshore wind farm as shown in the GIS map, sector-shaped inspection areas with a maximum radius of R1 and a minimum radius of R2 can be pre-delineated, centered at the offshore wind farm inspection system location. The maximum radius R1 for each sector-shaped inspection area determines the minimum cable length required for an aircraft to inspect that area. When the control cabinet detects that the length of the first cable segment equals the minimum first cable segment length for a pre-defined inspection area, it generates a pause command and transmits it to the cable release and retraction mechanism, halting cable release to prevent excessive cable release and overlapping the aircraft's inspection area. Furthermore, the control cabinet generates an inspection command and transmits it to the aircraft via the cable's optical fiber. The command includes a list of wind turbine coordinates in the area (e.g., wind turbines No. 1-No. 5) and an inspection priority (blades > tower > electrical compartment). After receiving the inspection command, the aircraft can inspect the wind turbines in the preset inspection area according to the set inspection route, and transmit the inspection data to the control cabinet through the optical fiber of the cable.

[0235] The above steps may be iteratively performed until the aircraft completes the inspection of all detection areas of the offshore wind farm and the inspection data of all detection areas have been transmitted to the control cabinet.

[0236] In some embodiments, a retraction command is transmitted to the cable releasing and retracting mechanism to retract the cable; based on the detected light signal, a landing command is transmitted to the aircraft through the optical fiber of the cable, so that the aircraft lands as the cable is retracted; if the length of the second cable segment is equal to the total length of the cable, a pause command is transmitted to the cable releasing and retracting mechanism to stop retracting the cable; based on the detected light signal, a shutdown command is transmitted to the aircraft through the optical fiber of the cable, so that the aircraft stops landing as the cable stops retracting.

[0237] After receiving the inspection request, the aircraft can fly along a preset route to directly above the offshore wind farm inspection system. At this point, the offshore wind farm inspection system can transmit a retraction command to the cable retracting mechanism to retract the cable. Based on the detected light signal, a landing command is transmitted to the aircraft via the cable's optical fiber, causing the aircraft to land as the cable retracts. When the length of the second cable segment equals the total cable length, a pause command can be transmitted to the cable retracting mechanism to stop retracting the cable. Based on the detected light signal, a shutdown command can be transmitted to the aircraft via the cable's optical fiber to stop landing as the cable stops retracting.

[0238] In some embodiments, the detection light signal may be modulated according to the takeoff instruction / patrol instruction; and the takeoff instruction / patrol instruction may be demodulated from the received detection light signal.

[0239] The control cabinet can use the probe light signal as a carrier, modulating the optical pulse's amplitude, frequency, or phase through modulation techniques to encode takeoff instructions, inspection instructions, or other commands into the optical signal. The aircraft can then demodulate the corresponding commands from the received probe light signal using corresponding amplitude, frequency, or phase demodulation techniques.

[0240] For example, pulse position modulation (PPM) can be used, with different commands corresponding to different positions of the detection light signal on the time axis. For example, a 0.5ms interval represents "takeoff" and a 1ms interval represents "inspection." The aircraft can generate the corresponding reflected light signal and analyze the intervals in the detection light signal using its built-in demodulation module to obtain the corresponding command and perform the corresponding operation based on the takeoff / inspection command.

[0241] For example, optical frequency shift keying (OFSK) modulation can be used to vary the frequency (wavelength) of the probe optical signal to carry command information while maintaining the ability to monitor cable length. The control cabinet can incorporate a tunable laser that switches between three wavelengths: a base wavelength (e.g., 1550.12nm) for cable length monitoring, a first additional wavelength (e.g., 1549.32nm), and a second additional wavelength (e.g., 1550.92nm) for "takeoff" and "inspection" commands, respectively. The aircraft can use an integrated optical filter bank to identify signals at different wavelengths, receive the corresponding commands, and then perform operations based on the takeoff / inspection commands.

[0242] Based on the above inspection method, this specification also proposes an embodiment of the inspection device. Figure 6 As shown, the inspection device 600 may specifically include the following modules:

[0243] The transmission module 601 can be used to transmit the detection light signal to the aircraft through the optical fiber of the cable.

[0244] The receiving module 602 may be configured to receive a reflected light signal returned by the aircraft based on the detection light signal.

[0245] The first calculation module 603 can calculate the phase difference between the reflected light signal and the detected light signal.

[0246] The acquisition module 604 may be configured to acquire a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment.

[0247] The second calculation module 605 may be configured to calculate the length of the first cable segment according to the first refractive index, the second refractive index, and the phase difference.

[0248] The inspection module 606 may be configured to control the aircraft to perform inspections based on the length of the first cable segment.

[0249] In some embodiments, the transmission module 601 may be specifically used to:

[0250] Using the laser phase method, the laser transmitter in the control cabinet system transmits an optical signal, which is modulated by a microwave signal intensity modulation device to generate a specific modulated optical signal;

[0251] The generated modulated optical signal is used as a detection optical signal.

[0252] In some embodiments, the first calculation module 603 may be specifically used to:

[0253] converting the detection light signal into a first electrical signal;

[0254] converting the reflected light signal into a second electrical signal;

[0255] extracting a baseband signal from the second electrical signal;

[0256] A phase difference between the baseband signal and the first electrical signal is calculated.

[0257] In some embodiments, the first calculation module 603 may further be used to:

[0258] The phase difference of the baseband signal relative to the first electrical signal is calculated using the following formula:

[0259] ;

[0260] Where, represents the angular frequency of the optical carrier, represents the angular frequency of the modulating signal, Indicates the fixed delay of optical signal transmission in optical fiber. Indicates the time it takes for an optical signal to travel through an optical fiber.

[0261] In some embodiments, the second calculation module 605 may be specifically used to:

[0262] A linear variation model of the phase difference and the optical fiber length is constructed according to a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment.

[0263] In some embodiments, the second calculation module 605 may further be used to:

[0264] Obtaining the total length of the optical fibers in the cable;

[0265] The length of the optical fiber in the first cable segment is calculated using the linear variation model based on the first refractive index, the second refractive index, the phase difference, and the total length of the optical fiber in the cable.

[0266] In some embodiments, the second calculation module 605 may further be used to:

[0267] Calculate the length of the optical fiber in the first cable segment using the following formula:

[0268] ;

[0269] Where, It represents the phase difference between the fundamental frequency signal and the detection light signal after photoelectric conversion. represents the wavelength of the optical signal, represents the first refractive index, represents the second refractive index, Indicates the total length of optical fiber in the cable.

[0270] In some embodiments, the inspection module 606 may be used to:

[0271] Obtaining the total length of the cable and the total length of the optical fibers in the cable;

[0272] If the length of the optical fiber in the first cable segment is equal to the total length of the cable, or the length of the optical fiber in the first cable segment is equal to the total length of the optical fiber in the cable, stopping releasing the cable;

[0273] If the length of the optical fiber in the second cable segment is equal to the total length of the cable, or if the length of the optical fiber in the second cable segment is equal to the total length of the optical fiber in the cable, retracting the cable is stopped.

[0274] As can be seen from the above, the inspection device provided in the embodiments of this specification can transmit a probe light signal to an aircraft via the optical fiber of a cable; receive a reflected light signal returned by the aircraft based on the probe light signal; calculate the phase difference between the reflected light signal and the probe light signal; obtain the first refractive index of the optical fiber in the first cable segment and the second refractive index of the optical fiber in the second cable segment; calculate the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference; and control the aircraft to perform an inspection based on the length of the first cable segment. Compared to existing methods, the cable can simultaneously provide a power transmission channel for the control cabinet and the aircraft, as well as data feedback on the length of the optical fiber in the cable outside the control cabinet. On the one hand, the power transmission channel provided by the cable can completely eliminate the limitations of the aircraft's battery life, eliminating the need for frequent return trips to replace batteries, reducing round-trip time, and significantly increasing the proportion of effective operating time. This can significantly shorten the time wind turbines are shut down due to faults or waiting for inspection confirmation, maximizing the number of hours of power generation in the wind farm. On the other hand, the cable is released outside the control cabinet according to the cable releasing and retracting mechanism, and according to the different refractive indices of the optical fibers in different cable segments inside and outside the control cabinet, the length of the first cable segment outside the control cabinet can be accurately fed back, and then the inspection range of the aircraft can be accurately controlled according to the length of the first cable segment outside the control cabinet.

[0275] It should be noted that the units, devices or modules described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. For the convenience of description, the above devices are described in terms of functions and are divided into various modules and described separately. Of course, when implementing this specification, the functions of each module can be implemented in the same or multiple software and / or hardware, or the module that implements the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0276] In order to complete the above instructions more accurately, refer to Figure 1As shown, the embodiment of this specification provides a specific offshore wind farm inspection system, which may include an aircraft 3, a cable 2 and a control cabinet 1; the cable 2 includes an optical fiber 21 and a transmission wire 22; the transmission wire 22 is used to supply power to the aircraft 3; one end of the cable 2 is connected to the aircraft 3, and the other end is connected to the cable releasing and retracting mechanism 15 of the control cabinet 1; the cable 2 includes a first cable segment released outside the control cabinet 1 and a second cable segment retracted into the control cabinet 1; the control cabinet 1 is used to perform the above-mentioned inspection method.

[0277] The control cabinet 1 can be specifically used to transmit a detection light signal to an aircraft through the optical fiber of a cable; receive a reflected light signal returned by the aircraft based on the detection light signal; calculate the phase difference between the reflected light signal and the detection light signal; obtain a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment; calculate the length of the first cable segment based on the first refractive index, the second refractive index and the phase difference; and control the aircraft to perform an inspection based on the length of the first cable segment.

[0278] It should be understood that in the various embodiments of this specification, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this specification.

[0279] It should also be understood that in the embodiments of this specification, the term "and / or" is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this specification generally indicates that the associated objects are in an "or" relationship.

[0280] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0281] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0282] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0283] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational tasks are performed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The task of specifying the functions in one or more boxes.

[0284] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A patrol inspection method, characterized in that: Applicable to an offshore wind farm inspection system; the offshore wind farm inspection system includes an aircraft, a cable, and a control cabinet; the cable includes an optical fiber and a power transmission wire; the power transmission wire is used to supply power to the aircraft; one end of the cable is connected to the aircraft, and the other end is connected to a cable release and retraction mechanism of the control cabinet; the cable includes a first cable segment released outside the control cabinet and a second cable segment retracted inside the control cabinet; The inspection method includes: transmitting the detection light signal to the aircraft through the optical fiber of the cable; receiving a reflected light signal returned by the aircraft according to the detection light signal; Calculate the phase difference between the reflected light signal and the detected light signal; obtaining a first refractive index of an optical fiber in a first cable segment and a second refractive index of an optical fiber in a second cable segment; Calculating the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference, including: constructing a linear variation model of the phase difference and the length of the optical fiber based on the first refractive index of the optical fiber in the first cable segment and the second refractive index of the optical fiber in the second cable segment; obtaining the total length of the optical fiber in the cable; and calculating the length of the optical fiber in the first cable segment using the linear variation model based on the first refractive index, the second refractive index, the phase difference, and the total length of the optical fiber in the cable: Where, It represents the phase difference between the fundamental frequency signal and the detection light signal after photoelectric conversion. represents the wavelength of the optical signal, represents the first refractive index, represents the second refractive index, Indicates the total length of optical fiber in the cable; The aircraft is controlled to perform inspection according to the length of the first cable segment.

2. The method according to claim 1, characterized in that The method further comprises: Based on the laser phase method, the optical signal generated by the laser transmitter in the control cabinet is intensity modulated to obtain a modulated optical signal; The generated modulated optical signal is used as a detection optical signal.

3. The method according to claim 1, characterized in that The calculating the phase difference between the reflected light signal and the detected light signal includes: converting the detection light signal into a first electrical signal; converting the reflected light signal into a second electrical signal; extracting a baseband signal from the second electrical signal; A phase difference between the baseband signal and the first electrical signal is calculated.

4. The method according to claim 3, characterized in that Calculating the phase difference of the baseband signal relative to the first electrical signal includes: The phase difference of the baseband signal relative to the first electrical signal is calculated using the following formula: ； Where, represents the angular frequency of the optical carrier, represents the angular frequency of the modulating signal, Indicates the fixed delay of optical signal transmission in optical fiber. Indicates the time it takes for an optical signal to travel through an optical fiber.

5. The method according to claim 1, characterized in that: The method further comprises: Obtaining the total length of the cable and the total length of the optical fibers in the cable; If the length of the optical fiber in the first cable segment is equal to the total length of the cable, or the length of the optical fiber in the first cable segment is equal to the total length of the optical fiber in the cable, stopping releasing the cable; If the length of the optical fiber in the second cable segment is equal to the total length of the cable, or if the length of the optical fiber in the second cable segment is equal to the total length of the optical fiber in the cable, retracting the cable is stopped.

6. A patrol inspection device, characterized in that: The device comprises: a transmission module, for transmitting the detection light signal to the aircraft through the optical fiber of the cable; A receiving module, configured to receive a reflected light signal returned by the aircraft based on the detection light signal; A first calculation module is used to calculate the phase difference between the reflected light signal and the detected light signal; an acquisition module, configured to acquire a first refractive index of the optical fiber in the first cable segment and a second refractive index of the optical fiber in the second cable segment; The second calculation module is configured to calculate the length of the first cable segment based on the first refractive index, the second refractive index, and the phase difference, including: constructing a linear variation model of the phase difference and the length of the optical fiber based on the first refractive index of the optical fiber in the first cable segment and the second refractive index of the optical fiber in the second cable segment; obtaining the total length of the optical fiber in the cable; and calculating the length of the optical fiber in the first cable segment using the linear variation model based on the first refractive index, the second refractive index, the phase difference, and the total length of the optical fiber in the cable. Where, It represents the phase difference between the fundamental frequency signal and the detection light signal after photoelectric conversion. represents the wavelength of the optical signal, represents the first refractive index, represents the second refractive index, Indicates the total length of optical fiber in the cable; The inspection module is used to control the aircraft to perform inspection according to the length of the first cable segment.

7. An offshore wind farm inspection system, characterized in that: The offshore wind farm inspection system includes an aircraft, a cable and a control cabinet; the cable includes an optical fiber and a transmission wire; the transmission wire is used to supply power to the aircraft; one end of the cable is connected to the aircraft, and the other end is connected to the cable releasing and retracting mechanism of the control cabinet; the cable includes a first cable segment released outside the control cabinet and a second cable segment retracted into the control cabinet; the control cabinet is used to perform the method described in any one of claims 1 to 5.

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