Wind turbine generator blade lightning protection intelligent detection system and method based on unmanned aerial vehicle

Abstract

The invention discloses a wind turbine generator blade lightning protection intelligent detection system and method based on an unmanned aerial vehicle. The system comprises an unmanned aerial vehicle platform, a force and position hybrid control assembly, an electrical measurement unit and a ground data processing unit. The unmanned aerial vehicle carries the detection mechanism to fly to the position of the blade lightning arrester, stable contact is achieved through force sensing feedback, a constant current source applies a test current, the on resistance is measured, and data is returned in real time. And the ground unit filters, compensates and judges the multi-point measurement result to generate a conduction state report. The system can automatically complete lightning protection channel detection under an unattended condition, has the advantages of high detection precision, strong environmental adaptability, good safety, high efficiency and the like, and is suitable for rapid inspection and state evaluation of onshore and offshore wind turbine generators.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric power, in particular to a wind turbine blade lightning protection intelligent detection system and method based on a UAV. BACKGROUND

[0002] With the continuous increase of global wind power installed capacity, wind turbine has become one of the main forms of renewable energy power generation. Wind turbine blades are usually large composite structures, with a length generally exceeding 60 meters, and an internal conductive lightning protection channel is integrated for guiding the current to the tower foundation grounding system when lightning occurs, thereby protecting the blade and the entire machine equipment.

[0003] In actual operating environment, wind turbines are often in complex climatic conditions such as high altitude, strong wind, high humidity or salt spray, and the blade lightning protection system is easily affected by lightning, electric corrosion, fatigue vibration or corrosion aging, etc., resulting in poor conduction, excessive contact resistance or even open circuit of the lightning protection channel. Once the lightning protection channel fails, the lightning current may not be effectively discharged to the ground net, thereby causing serious consequences such as blade structure ablation, electrical equipment damage, shutdown accidents, etc. Therefore, regular detection and evaluation of the conduction performance of the blade lightning protection channel is an important link for safe operation and life maintenance of wind turbines.

[0004] The existing blade lightning protection detection methods mainly include two types of manual contact detection and ground test method.

[0005] Manual contact detection usually requires maintenance personnel to carry portable resistance measuring instruments through aerial work vehicles or suspension devices to conduct conduction tests between the blade front end lightning arrester and the tower foundation grounding end. Although this method is simple in principle, it has the following disadvantages: High safety risk: the detection personnel need to operate at a height of hundreds of meters, which is easily affected by strong winds and lightning weather, and there is a great safety hazard; High labor intensity and low efficiency: electrical connection and measurement need to be completed manually for each blade detection, and the detection time of a single wind turbine is relatively long, which is not suitable for large-scale wind farm centralized detection; Poor measurement stability: manual contact pressure and position are inconsistent, which easily causes contact resistance fluctuation and large measurement error; Poor environmental adaptability: in complex environments such as mountains, seas or low temperatures, manual detection is difficult to implement, and the detection period is often forced to be extended.

[0006] The ground test method mainly uses tower base port signal collection to calculate the lightning protection channel resistance value by applying current inside the tower and monitoring the response voltage change. This method avoids climbing operation, but the measurement result is easily disturbed by the tower grounding resistance and other electrical branches, and it is difficult to accurately reflect the conduction state of each branch channel of the blade. At the same time, this method cannot identify the local poor contact or broken wire position in the blade, and it is difficult to achieve accurate positioning.

[0007] In recent years, some researches have attempted to apply UAV technology to wind power equipment inspection, such as blade surface defect detection, infrared imaging temperature monitoring, and appearance crack identification. However, most of the current UAV inspection systems are limited to visual detection or surface image recognition, and have not realized electrical contact or conduction performance detection with the blade lightning protection system. The existing UAV measurement platform generally has the following technical bottlenecks: It is impossible to achieve stable mechanical contact and electrical connection on the surface of the blade; There is a lack of force-position hybrid control algorithm, and vibration or slip is easy to occur during the contact process; The electrical measurement device has insufficient precision, and cannot realize the air-ground closed measurement loop; There is interference risk between the data transmission and flight control system, affecting flight safety.

[0008] In summary, there is still a lack of a system and method that can automatically complete the lightning protection channel conduction detection of the blade in the prior art. How to use the UAV platform to realize accurate contact and conduction measurement of the blade lightning arrester in a complex aerodynamic environment, and how to ensure detection accuracy and system stability under the condition of limited load and energy consumption, have become technical problems to be solved in the field of intelligent detection of wind power equipment. SUMMARY

[0009] To solve the above technical problems, the present application provides a wind turbine blade lightning protection intelligent detection system and method based on a UAV.

[0010] The present application is realized by the following technical solutions: A wind turbine blade lightning protection intelligent detection system based on a UAV, comprising: A UAV platform for autonomous flight and hovering positioning around the wind turbine blade, the UAV platform comprising a positioning module and a flight control module for realizing attitude holding and accurate positioning of the UAV at a predetermined position; An airborne contact end installed on the UAV platform for forming electrical contact with the lightning arrester of the wind turbine blade; a force sensor and a displacement sensor are provided on the airborne contact end, the force sensor is used to detect the contact pressure, and the displacement sensor is used to detect the contact position; the UAV platform performs force-position hybrid control according to the sensor signals to maintain stable contact; An electrical measurement unit is installed at the bottom of the UAV platform and electrically connected with the airborne contact terminal, used to form a measurement loop between the airborne contact terminal and the grounding terminal of the wind turbine and measure the conduction resistance of the lightning protection channel of the blade; the electrical measurement unit is electrically connected with the ground terminal tester through a test flexible cable; A data processing unit is arranged on the ground and communicatively connected with the electrical measurement unit, used to perform contact resistance compensation, filtering and judgment processing on the measurement results and output the conduction performance results of the lightning protection channel; A ground grounding connection device is arranged at the tower base of the wind turbine, used to form a temporary electrical connection with the grounding grid of the wind turbine during detection and electrically connected with the grounding terminal of the ground terminal tester through a lead wire, thereby forming a complete conduction detection loop; The system realizes the automatic contact of the blade lightning arrester through the precise positioning and force-position hybrid control of the UAV platform, and realizes the high-precision detection of the conduction performance of the lightning protection channel of the blade of the wind turbine through the high-precision measurement of the electrical measurement unit and the compensation algorithm of the data processing unit.

[0011] The system realizes the intelligent detection of the lightning protection conduction performance of the blade of the wind turbine based on the UAV platform, and is a comprehensive detection equipment integrating flight control, contact measurement, electrical testing and data processing. The traditional lightning protection detection method of the wind turbine relies on manual climbing or basket operation, which not only has safety risks, but also has low detection efficiency and cannot work stably under high wind speed or complex terrain conditions. The lightning protection detection work can be carried out in a fully automatic or semi-automatic state through the self-positioning and precise hovering function of the UAV, which greatly improves the detection safety and precision.

[0012] The UAV platform is the core execution unit of the system, and its positioning module adopts the fusion technology of global navigation satellite system (GNSS) and inertial navigation unit (IMU) to realize centimeter-level position accuracy. In the environment where the airflow disturbance around the blade of the wind turbine is significant, it is difficult to maintain a stable attitude simply by relying on GNSS, therefore, the system also introduces a visual positioning and ultrasonic ranging auxiliary module to perform position fine-tuning and hovering correction in a close-range environment, thereby ensuring the precise control of the airborne contact terminal near the surface of the blade.

[0013] The airborne contact end is an important component for electrical contact and physical measurement. It needs to consider both lightweight and rigidity in design, ensuring reliable electrical conductivity and avoiding damage to the blade surface. The force sensor is set to monitor the contact pressure in real time to prevent excessive contact force from damaging the surface coating of the blade lightning arrester. The displacement sensor detects the pose and extension changes of the contact end, assisting the UAV control system in force and position hybrid control. The so-called "force and position hybrid control" is a feedback control that combines contact pressure signals and spatial displacement signals, allowing the UAV to dynamically adjust the propulsion force to maintain constant contact pressure while maintaining stable hovering. This control method is essentially a closed-loop control system based on multi-sensor fusion.

[0014] The electrical measurement unit is the core for detecting the conduction performance. Its working principle is similar to the four-wire micro-resistance test technology, which establishes a current path between the blade lightning arrester and the wind turbine grounding end and measures the voltage drop to calculate the equivalent resistance of the lightning protection channel. Due to the weight and power consumption limitations of the electrical measurement unit on the UAV platform, the internal circuit uses a low-power precision current source and a high-sensitivity differential amplifier circuit, with a measurement accuracy of milliohm. To avoid the influence of electromagnetic interference from the UAV motor on the test signal, the measurement unit and the flight control system are electrically isolated through a shielded cable and an isolation module.

[0015] The data processing unit is located on the ground end, which not only receives and processes measurement results, but also is responsible for error compensation and statistical analysis of data. Contact resistance compensation is to eliminate the additional resistance caused by surface oxidation or contact area difference between the airborne contact end and the lightning arrester; filter processing is used to remove the interference of electrical signals during the UAV vibration, wind noise, and communication process; and the judgment processing is based on national or industry standards (such as IEC61400-24) to compare and analyze the conduction resistance of the lightning protection channel, thereby outputting quantitative conduction performance results. The final results are transmitted back to the ground workstation wirelessly, realizing the closed loop of the detection task.

[0016] The ground grounding connection device is used to ensure the complete closure of the measurement loop, which is one of the key links for accurate measurement. Setting a temporary grounding connection at the base of the wind turbine tower not only facilitates the connection to the tower grounding net, but also ensures the equipotential connection of the entire detection loop, preventing measurement errors caused by poor grounding. The device uses a conductive soft cable made of multiple thin copper strands, which ensures electrical conductivity and facilitates slight cable swing during UAV flight.

[0017] The technical innovation point of the whole system is to realize the automatic contact of the blade lightning receptor and the high-precision electrical conduction test through the spatial accurate positioning and force-position hybrid control of the unmanned aerial vehicle. Through the scheme, the rapid detection can be carried out without stopping the operation of the fan, and the batch automatic inspection of multiple fans in the wind power plant can be realized. Compared with the traditional manual detection method, the system not only significantly reduces the operation risk and labor cost, but also realizes the standardization and intelligentization of the detection results through the data processing algorithm, and provides a reliable basis for the regular maintenance of the lightning protection system of the wind turbine generator.

[0018] Further, the above-mentioned airborne contact end comprises a mounting seat, an adjustable cantilever assembly and a contact head assembly; The above-mentioned mounting seat is fixedly arranged at the bottom center position of the unmanned aerial vehicle platform; The above-mentioned adjustable cantilever assembly is hingedly connected to the mounting seat at one end and connected to the contact head assembly at the other end; The above-mentioned adjustable cantilever assembly comprises a coaxially arranged outer sleeve and an inner extension rod; the inner extension rod can slide in the axial direction in the outer sleeve and is limited by a locking pin; the adjustable cantilever assembly and the mounting seat can be fixed at a certain relative position; The above-mentioned contact head assembly comprises a conductive base, a conductive gasket and an insulating support body; The above-mentioned conductive base is fixedly connected to the front end of the adjustable cantilever assembly by a threaded connection; The above-mentioned conductive gasket is arranged on the front end surface of the conductive base, the shape of the conductive gasket is disc-shaped, and the diameter of the conductive gasket is less than two-thirds of the diameter of the conductive base; The above-mentioned insulating support body is sleeved on the outer circumferential surface of the conductive base, and the conductive base and the insulating support body are positioned by an annular clamping groove; The conductive base of the above-mentioned contact head assembly is provided with a sensor mounting cavity inside, the central axis of the mounting cavity coincides with the normal direction of the conductive gasket, at least three force sensors distributed in the circumferential direction are embedded in the mounting cavity, the sensing surface of the force sensor faces the back surface of the conductive gasket and tightly adheres to it, and the force sensor is electrically connected to the electrical measurement unit through a lead wire; A rubber damping sleeve is sleeved on the outer wall of the inner extension rod of the above-mentioned adjustable cantilever assembly, a plurality of evenly distributed annular grooves are arranged on the rubber damping sleeve in the axial direction, the inner wall of the outer sleeve is in clearance fit with the rubber damping sleeve, an air damping cavity is formed between the rubber damping sleeve and the inner wall of the outer sleeve during the extension and retraction of the inner extension rod, and the air damping cavity is communicated with the outside through a micro hole; The contact head assembly and the adjustable cantilever assembly are provided with an electrical isolation layer, the electrical isolation layer comprises a two-layer structure, the inner layer is a polyimide film layer, and the outer layer is an epoxy resin coating layer; the electrical isolation layer covers the non-contact part of the conductive base in the axial direction of the contact head assembly, and the thickness of the electrical isolation layer ranges from 0.3mm to 1.0mm; The ground grounding connection device comprises a grounding clamp, a conductive flexible cable and a grounding terminal; The grounding clamp is used to form a detachable electrical connection with the exposed grounding copper bar or grounding bolt of the wind turbine tower foundation; One end of the conductive flexible cable is electrically connected with the grounding clamp, and the other end is connected with the input end of the ground terminal tester through the grounding terminal, so that the airborne contact end, the lightning protection channel of the blade, the tower foundation grounding net and the ground terminal tester form a closed conduction detection loop; The outer layer of the conductive flexible cable is covered with a wear-resistant insulating sheath, the length of the conductive flexible cable is 5-15 meters, and the conductive flexible cable is laid through a winding disc or a support during use; The grounding clamp and the conductive flexible cable are fixed by crimping or threaded connection, and the contact part is plated with tin to prevent corrosion; The grounding terminal is made of copper alloy material, and a locking structure is arranged at the end of the grounding terminal to ensure stable connection; The test flexible cable is laid along the flight path of the unmanned aerial vehicle and can be stretched and contracted, and is used to maintain the electrical path between the airborne contact end and the ground grounding connection device during detection.

[0019] The airborne contact end is the actuator for realizing electrical connection and signal acquisition of the whole system, and the core of the design is to realize stable, controllable and adjustable contact action, while ensuring the electrical reliability and mechanical safety. The working environment of the unmanned aerial vehicle near the blade surface is complex, and is significantly affected by wind disturbance and airflow vibration, so the airborne contact end needs to have high sensitive buffering and adaptive capacity.

[0020] The mounting seat is the main connection base body between the contact end and the unmanned aerial vehicle platform, and is made of lightweight high-strength metal material (such as 7075 aluminum alloy or titanium alloy), which meets the requirements of structural strength and weight reduction. The mounting seat is fixed at the center position of the bottom of the unmanned aerial vehicle, so as to ensure that the contact force is transmitted along the gravity axis of the unmanned aerial vehicle, thereby avoiding the attitude deviation of the unmanned aerial vehicle body caused by unbalanced torque.

[0021] The design concept of the adjustable cantilever assembly is to realize a telescopic and angle-adjustable mechanical connection, so that the contact end can maintain a suitable contact direction under different blade attitudes and inclination angles. The coaxial structure composed of the outer sleeve and the inner extension rod can realize telescopic adjustment in a limited space. The locking pin structure is used for mechanical limiting at different extension lengths to prevent accidental sliding under flight vibration or external force. This structure makes the system have reconfigurability and adaptability, and different sizes of blades or contact positions can be adjusted to achieve the best geometric matching.

[0022] The conductive base is the core component of the contact head assembly, which undertakes the dual tasks of conduction and sensing. Its threaded connection method is convenient for maintenance and replacement, and the conduction performance is stable. The disc-shaped design of the conductive pad is determined based on the current density distribution principle, and its smaller diameter can concentrate the contact current to ensure measurement accuracy, while avoiding surface unevenness or uneven contact caused by excessive contact area. The conductive pad material is selected from silver-plated copper alloy or tungsten-copper composite material to obtain low contact resistance and high wear resistance.

[0023] The insulating support is set to prevent current leakage along the outer surface of the contact end and ensure the accuracy of electrical measurement. It is positioned between the conductive base through the annular clamping groove, which can maintain stable cooperation under thermal expansion and contraction or vibration conditions. The insulating material is generally selected from polytetrafluoroethylene (PTFE) or PEEK engineering plastic, which has high temperature resistance and voltage resistance characteristics.

[0024] The sensor mounting cavity inside the conductive base provides a fixed position for the force sensor. The design of at least three force sensors arranged in a ring can realize spatial uniform detection of contact force, so as to calculate the direction of resultant force and the position of pressure center through algorithm. This structure effectively avoids the influence of single-point measurement error on the feedback of the control system, so that the unmanned aerial vehicle can realize self-balancing contact control through force feedback.

[0025] The combination of the rubber damping sleeve and the air damping cavity forms a passive damping system. When the telescopic rod moves, air flows through the micro-holes to produce damping effect, thereby reducing the impact force. This design can absorb part of the impact energy when the unmanned aerial vehicle contacts the blade, prevent mechanical vibration from affecting the accuracy of the sensor, and prolong the service life of the mechanical parts. The air damping characteristics can also be optimized and adjusted by adjusting the size of the micro-holes and the hardness of the rubber to adapt to different operating environments.

[0026] The electrical isolation layer further enhances the safety of the system. The polyimide film layer has good heat resistance and dielectric strength, and the outer layer of epoxy resin coating provides additional moisture resistance and wear resistance. The double-layer isolation structure not only prevents the interference of contact current on other electronic modules of the unmanned aerial vehicle, but also protects against accidental short circuits. The thickness of the isolation layer is controlled between 0.3mm and 1.0mm, which is the result of a compromise between electrical breakdown strength and mechanical flexibility, ensuring insulation performance without affecting the heat dissipation and mechanical support capability of the conductive base.

[0027] The design of the ground grounding connection device fully considers the high humidity, strong corrosion and complex wiring problems of the wind farm environment. The grounding clamp adopts a high-strength spring-loaded structure, which can quickly clamp the tower foundation grounding copper bar and maintain stable contact pressure. The conductive soft cable is covered with a wear-resistant sheath, which not only prevents mechanical wear, but also effectively resists ultraviolet aging. Its length is designed to be in the range of 5-15 meters, which is an empirical parameter obtained by considering the operation radius of the unmanned aerial vehicle and the height of the tower, which can ensure sufficient space for movement and will not produce excessive overhang to interfere with the flight of the unmanned aerial vehicle.

[0028] The innovation of this technical solution lies in that through the modular adjustable structure and multi-layer buffer design, the airborne contact end not only has high flexibility and controllability, but also maintains high-precision electrical performance, ensuring stable contact and accurate measurement under complex conditions such as strong wind, vibration and attitude change.

[0029] Further, the above-mentioned airborne contact end is connected to the mounting platform at the lower part of the unmanned aerial vehicle body through a mounting bracket, The mounting bracket includes a support arm in an inverted U-shaped structure and a transverse reinforcing beam; Both ends of the support arm are connected to the load-bearing frame arranged below the unmanned aerial vehicle body through bolts; The reinforcing beam is fixedly arranged between the support arms and is arranged perpendicular to the longitudinal axis of the unmanned aerial vehicle. The mounting seat is fixedly arranged at the lower center position of the reinforcing beam through screws; Rubber damping pads are arranged at both ends of the support arm of the mounting bracket. The damping pads are connected to the load-bearing frame of the unmanned aerial vehicle through screws. The thickness of the damping pads is 5-15mm, and a plurality of through holes extending in the vertical direction are embedded in the damping pads to form air buffer cavities. The number of air buffer cavities is 3-6, which are evenly distributed along the length direction of the support arm.

[0030] The mounting bracket, as an intermediate structure between the unmanned aerial vehicle platform and the airborne detection device, aims to achieve high stability, vibration resistance and easy installation. The combination of the inverted U-shaped support arm and the reinforcing beam is a typical lightweight load-bearing design, which can effectively disperse the load and maintain central symmetry, thereby reducing attitude deviation during flight.

[0031] The support arms are connected to the bearing frame of the UAV body through bolts at both ends, and this detachable structure facilitates the rapid installation and maintenance of the system. The bearing frame of the UAV is a carbon fiber composite structure or an aluminum-magnesium alloy frame, and the bolt connection not only provides sufficient mechanical strength, but also enables the on-board detection module to be quickly replaced when necessary to perform different tasks.

[0032] The reinforcing beam plays a role in stabilizing the lateral stiffness of the entire structure. Its perpendicular arrangement to the longitudinal axis of the UAV can suppress the lateral torque caused by the deflection of the propeller, keeping the contact end in a stable attitude in the vertical direction. The mounting seat is located at the center below the reinforcing beam, ensuring that the force axis of the contact end is aligned with the center of gravity of the UAV, thereby avoiding the generation of lateral torque during contact.

[0033] The design of the damping pad embodies the air-elastic damping principle. It is made of high-elastic rubber material and has multiple vertical through-holes inside to form air buffer cavities. During vibration, air is compressed and released in the cavities, forming a damping effect similar to an "air spring". The thickness of 5-15 mm provides sufficient buffer stroke without excessively reducing the structural rigidity. The number of through-holes is 3-6, which ensures the uniformity of damping performance and effectively absorbs high-frequency disturbances from the vibration of the UAV blades and airflow impact. Through this structure, the mechanical vibration noise of the entire on-board detection device in flight state can be reduced by more than 30%, significantly improving the measurement stability.

[0034] In addition, the modular design of the mounting bracket makes it compatible with different models of UAV platforms. By changing the length of the support arm or the width of the reinforcing beam, it can adapt to different sizes of UAV chassis structures, thereby having good system expandability and universality.

[0035] Further, the above-mentioned electrical measurement unit is fixedly connected to the bottom of the UAV platform, including an upper layer arranged signal acquisition cabin and a lower layer arranged conduction test cabin; The above-mentioned signal acquisition cabin is provided with a printed circuit board, and the above-mentioned printed circuit board is fixedly installed with an analog-to-digital conversion chip, a signal filter unit and a microprocessor chip; The above-mentioned lower layer conduction test cabin is provided with a test wiring terminal and a relay switching component, and the above-mentioned signal acquisition cabin and the conduction test cabin are separated by a sealed partition, and the above-mentioned partition is embedded with a waterproof sealing ring and a threading hole, and an insulating bushing is installed in the threading hole; The above-mentioned signal filter unit includes a group of parallel inductance elements and capacitance elements, the above-mentioned inductance elements are arranged in series along the signal input path, and the above-mentioned capacitance elements are connected between the signal input end and the common ground end, the number of turns of the above-mentioned inductance elements is 50-150 turns, the capacitance of the above-mentioned capacitance elements is 100nF-470nF, the above-mentioned filter unit is welded on the inner conductor of the multilayer circuit board, and the above-mentioned circuit board adopts a four-layer structure, and the inner layer is provided with independent signal layer and ground layer; The printed circuit board in the signal acquisition cabin is provided with a temperature compensation circuit, which comprises a temperature sensing element, a voltage reference source and an operational amplification unit; The temperature sensing element is installed at the edge of the printed circuit board, and its temperature sensing surface is arranged towards the direction of the on-off test cabin. The temperature sensing element is connected with the operational amplification unit through a wire, and the voltage reference source is connected with the analog input end of the microprocessor chip.

[0036] The electrical measurement unit is an independent module at the lower part of the unmanned aerial vehicle platform, and integrates multiple functions such as signal acquisition, filtering, on-off test and preliminary data processing, and is a key part of the system to realize high-precision resistance measurement. The upper and lower layered structure design isolates the electrical part from the mechanical part, facilitating waterproofing, dustproofing and electromagnetic shielding.

[0037] The printed circuit board in the upper signal acquisition cabin is the core electronic platform of the entire measurement system. The analog-to-digital conversion chip (ADC) is responsible for converting voltage and current signals into digital signals for subsequent microprocessor operation and analysis. The inductance-capacitance network of the signal filtering unit is used to suppress high-frequency noise and ensure the purity of the measurement signal. The design of parallel LC filter can attenuate interference signals in a wide frequency band, so that the system can still maintain stable precision under the high-frequency pulse interference of the unmanned aerial vehicle motor. The selection of inductance turns and capacitance value is optimized through electromagnetic simulation to achieve the best signal-to-noise ratio in the range of 10Hz-1kHz.

[0038] The lower on-off test cabin is mainly used to complete the tasks of current injection and signal switching. The test wiring terminal connects the on-board contact end and the test soft cable, and the relay switching component is used to switch between different measurement loops or perform system self-checking. The waterproof sealing ring and the insulating bushing on the sealing partition prevent external moisture or rain from entering the electronic cabin, improve the system protection level, and can reach IP65 or above.

[0039] The setting of the temperature compensation circuit can significantly improve the measurement stability. Since the unmanned aerial vehicle operates in different altitudes and temperature environments, resistance measurement is easily affected by temperature drift. The temperature sensing element collects the ambient temperature in real time, and the operational amplification unit corrects the measurement value according to the measured temperature, thereby eliminating the thermal drift error. The voltage reference source provides a stable reference voltage to ensure that the ADC sampling accuracy is not affected by the battery voltage fluctuation. The entire signal acquisition cabin realizes electromagnetic isolation between the signal layer and the ground layer through a multi-layer PCB structure, effectively reducing the cross-coupling noise.

[0040] The comprehensive performance index of the unit can reach a measurement error of ±0.5% or less, which can meet the requirements of high precision and high stability for detecting the conduction resistance of the lightning protection channel of the wind turbine. Through the wireless communication module and the ground data processing unit, the system can upload the measurement data in real time during flight and perform preliminary analysis, realizing rapid detection and remote monitoring.

[0041] An unmanned aerial vehicle-based intelligent lightning protection detection method for wind turbine blade according to the above system, comprising the following steps: Task preparation and system verification: self-checking and calibration of the unmanned aerial vehicle platform, the airborne contact end, the electrical measurement unit and the ground grounding connection device are performed to ensure that the system communication and measurement state are normal; Positioning and attitude adjustment: control the unmanned aerial vehicle platform to fly to the vicinity of the lightning receptor of the wind turbine blade, obtain the position information of the unmanned aerial vehicle through the positioning module, and adjust the attitude of the unmanned aerial vehicle to the predetermined detection position based on visual recognition or sensor feedback; Contact and measurement: drive the airborne contact end to make electrical contact with the lightning receptor, and control the contact pressure and contact position to be stable through the feedback of the force sensor and the displacement sensor; then establish a measurement loop between the airborne contact end and the ground grounding connection device, and collect the conduction resistance data; Data processing and compensation: the measured conduction resistance data is compensated for contact resistance, filtered and averaged multiple times to obtain the actual conduction resistance value of the lightning protection channel of the blade; then the actual conduction resistance value is compared with the preset standard threshold to determine whether the lightning protection channel meets the conduction requirements, and a detection result report is generated.

[0042] The unmanned aerial vehicle-based intelligent lightning protection detection method for wind turbine blade is an automatic detection scheme that deeply integrates aviation platforms and electrical measurement technology. The entire detection process is completed through five main stages of task planning, flight control, force control contact, electrical measurement and data intelligent processing. This method not only solves the problems of traditional manual detection such as operation danger, low efficiency and subjective data, but also realizes fast and standardized detection of the lightning protection channel of the blade.

[0043] The task preparation stage is the premise of the entire detection operation. The unmanned aerial vehicle needs to complete system self-checking and calibration before taking off to ensure that all sensors, communication links and electrical measurement modules are working properly. The self-checking content includes attitude sensor (gyroscope, accelerometer) calibration of the flight control system, zero point adjustment of the electrical measurement unit and resistance verification of the ground grounding connection device. Through the automatic calibration process, potential system errors can be eliminated in advance to ensure the reliability of subsequent measurements.

[0044] The positioning and attitude adjustment phase mainly relies on the navigation module and visual recognition system of the unmanned aerial vehicle. The unmanned aerial vehicle determines the approximate spatial position through GNSS and IMU data fusion, and then identifies the surface feature points of the blade using an on-board camera or laser range finder to achieve high-precision positioning. The attitude adjustment algorithm combines extended Kalman filtering and PID closed-loop control to enable the unmanned aerial vehicle to maintain stable hovering under wind speed interference. The system uses multi-source data fusion technology (Multi-Sensor Fusion) to correct positioning deviations in real time, enabling positioning accuracy to be controlled within ±3 centimeters.

[0045] The contact and measurement phase is the core of the entire method. When the unmanned aerial vehicle approaches the blade surface, the sensors on the contact end begin to work, and the system dynamically adjusts the output of the thruster through a force-position hybrid control algorithm to achieve compliant contact. After contact, the electrical measurement unit establishes a current path between the blade lightning arrester and the tower base grounding net, outputs a fixed current through a constant current source, and measures the voltage drop to calculate the conduction resistance of the blade lightning protection channel. Since the measured current is small (10-50 mA), it will not cause any damage to the blade material or lightning arrester.

[0046] The data processing and compensation phase is completed on the ground side. The system performs multiple filtering and abnormality rejection on the received raw resistance data. The combination of weighted average and median filtering can effectively suppress noise interference. At the same time, resistance compensation is performed according to the contact pressure and temperature parameters to eliminate errors caused by contact surface oxidation or temperature drift. Finally, the data processing unit determines whether the lightning protection channel is well-conducted according to the standard threshold and outputs a detection result report. The entire process realizes unattended, high-precision, and intelligent detection operations.

[0047] Further, in the task preparation and system verification step, the above unmanned aerial vehicle establishes a three-dimensional coordinate model according to the spatial attitude parameters of the wind turbine blade before takeoff, the three-dimensional coordinate model takes the center of the wind turbine tower as the origin, takes the blade axis direction as the X axis, takes the blade normal direction as the Y axis, and takes the tower axial direction as the Z axis, the unmanned aerial vehicle determines its spatial coordinates through the fusion positioning of the global navigation satellite system and the visual recognition system, and matches them with the three-dimensional coordinate model to generate a flight reference path.

[0048] The establishment of the three-dimensional coordinate model by the unmanned aerial vehicle before takeoff is an important step to achieve precise positioning and path planning. The wind turbine blades are distributed in a propeller shape in space, with obvious spatial curvature and inclination. By establishing a three-dimensional coordinate model with the tower center as the origin, a unified reference coordinate system can be provided for the unmanned aerial vehicle flight.

[0049] The three-dimensional model can be established based on the blade CAD data provided by the fan manufacturer, or the actual geometric information can be obtained through laser radar (LiDAR) or stereo vision scanning. In the model, the blade axis direction is defined as the X axis, the blade normal direction is defined as the Y axis, and the tower cylinder vertical direction is defined as the Z axis. The unmanned aerial vehicle acquires its own spatial coordinates in real time through the fusion positioning of GNSS and visual recognition system, and matches with the model to generate a flight reference path.

[0050] The fusion positioning system adopts a "loose coupling GNSS + IMU + visual SLAM" architecture. GNSS provides global coordinate reference, IMU is used for high-frequency attitude update, and visual SLAM uses blade surface texture or lightning arrester identifier for local position correction. The fusion algorithm dynamically optimizes the pose estimation through extended Kalman filtering or particle filtering, thereby realizing centimeter-level relative positioning. This process ensures that the unmanned aerial vehicle can still move accurately along the blade surface under complex airflow conditions, avoiding collision and yaw.

[0051] The generated flight reference path includes not only spatial position points, but also dynamic parameters such as speed, attitude, and approach angle. The system can automatically optimize the path according to wind speed, blade angle, and unmanned aerial vehicle power redundancy, so that the unmanned aerial vehicle is always in a safe area when performing detection tasks.

[0052] Further, in the step of positioning and attitude adjustment, the attitude of the unmanned aerial vehicle is adjusted by the flight control module when moving along the above-mentioned flight reference path; The flight control module collects three-axis gyroscope signals and accelerometer signals, and corrects the attitude angle error in real time through the extended Kalman filtering algorithm, so that the spatial attitude of the on-board contact end of the unmanned aerial vehicle keeps the deviation angle with the normal direction of the blade surface not more than 3°.

[0053] When the unmanned aerial vehicle moves along the flight reference path, its attitude adjustment is performed in real time by the flight control module. The flight control system detects angular velocity through a three-axis gyroscope, detects gravity direction changes through a three-axis accelerometer, and calculates a heading angle combined with magnetometer data, to realize three-dimensional attitude estimation.

[0054] In a complex airflow environment, conventional PID control is difficult to cope with transient disturbances, so the system introduces an extended Kalman filter algorithm (EKF) to dynamically correct the attitude angle error. EKF can estimate the attitude deviation of the unmanned aerial vehicle in real time by fusing the outputs of the gyroscope, accelerometer, and visual sensor through the prediction-update mechanism, and can eliminate random drift and noise interference.

[0055] Through the above algorithm, the attitude of the unmanned aerial vehicle on-board contact end can keep the deviation angle with the normal direction of the blade surface not more than 3°, that is, the contact direction is almost perpendicular to the blade surface. This precise attitude control not only ensures the uniform distribution of contact pressure, but also reduces the transverse shear force, preventing scratches or deformation of the blade surface. At the same time, the flight control system will also dynamically adjust the propeller speed according to the wind speed sensor data to offset the external disturbance moment, so as to realize the stable hovering of the contact end.

[0056] Further, in the step of contact and measurement, the unmanned aerial vehicle approaches the blade in a stepwise deceleration manner to control the descent speed, and the descent process is divided into three stages: The first stage descent speed is 1.0-1.5 m / s; The second stage descent speed is 0.3-0.5 m / s; The third stage descent speed is not more than 0.1 m / s, In the third stage, the on-board contact end stops descending and hovers when the distance from the blade surface is detected by the proximity sensor to be less than 50 mm.

[0057] The stepwise deceleration control of the unmanned aerial vehicle approaching the blade surface is a safe and efficient approach strategy. Due to the existence of airflow disturbance layer on the surface of wind turbine blade, if the unmanned aerial vehicle descends at a constant speed, it is easy to cause position oscillation or even contact out of control due to airflow rebound. By controlling the descent speed in stages, the inertial impact can be gradually reduced and the control accuracy can be improved.

[0058] The first stage (1.0-1.5 m / s) is mainly used for fast approaching the target area from a long distance, at this time the unmanned aerial vehicle is in automatic navigation mode, the flight height is high, and the wind field disturbance is small.

[0059] The second stage (0.3-0.5 m / s) enters the airflow transition zone around the blade, and the system dynamically corrects the attitude through laser ranging and visual recognition to ensure the normal approach.

[0060] The third stage (≤0.1 m / s) is the fine control stage, the unmanned aerial vehicle enters the hovering control state, and relies on the proximity sensor (infrared or ultrasonic) to detect the distance change from the blade. When the distance is less than 50 mm, it automatically stops descending and hovers to avoid mechanical collision.

[0061] This multi-stage descent control combines aerodynamic characteristics and sensor feedback mechanism, which can significantly improve the attitude stability and operation safety of the unmanned aerial vehicle in the blade near field.

[0062] Further, after the unmanned aerial vehicle hovers in the step of contact and measurement, the adjustable suspension arm assembly of the on-board contact end is stretched in the longitudinal axis direction of the unmanned aerial vehicle to make the conductive pad of the contact head assembly form mechanical contact with the blade lightning arrester; The contact is maintained for 2-3 seconds, during which the force sensor in the contact end detects the contact pressure value. When the contact pressure is within the range of 5-10 N, the system determines that the contact is valid and enters the conduction test phase. In the conduction test phase, the conduction test cabin outputs a constant current signal, the amplitude of the constant current is 10-50 mA, and the test duration is 3-5 seconds. The signal acquisition cabin synchronously records the voltage drop data and calculates the resistance value from the blade lightning receptor to the tower bottom grounding net. The test results are transmitted in real time to the data processing unit through the wireless communication module. The data processing unit is set on the ground. After the conduction test is completed, the unmanned aerial vehicle automatically rises by 0.5 meters and retreats by 0.3 meters, and then moves to the next preset contact point position to repeat the test steps. The number of test points for each blade is 3-5, and each test point is uniformly distributed along the length of the blade.

[0063] After the unmanned aerial vehicle hovers, the onboard contact end realizes flexible contact with the blade lightning receptor through micro-stretch control. The adjustable cantilever assembly is driven by the flight control system command during micro-stretch, and sub-millimeter level stretch control is realized through a stepping motor or a servo actuator.

[0064] During the contact process, the force sensor detects the contact pressure in real time, and when the pressure value is stable within the range of 5-10 N, the system considers the contact to be valid. This pressure range is determined based on the strength of the blade surface material and the characteristics of the lightning receptor coating, which can ensure good conductive contact without causing structural damage. If the pressure exceeds the set upper limit, the system will immediately perform a retreat action to prevent overloading due to the superposition of the unmanned aerial vehicle's thrust.

[0065] In the conduction test phase, the electrical measurement unit outputs a constant current of 10-50 mA, and the voltage drop is recorded by a high-precision voltage acquisition module. The test lasts for 3-5 seconds, providing enough sampling points to eliminate random errors. The measured data is transmitted in real time to the ground data processing unit through the wireless module, which performs resistance calculation and determination.

[0066] After the unmanned aerial vehicle completes single-point testing, it automatically performs three actions: "retreat - rise - reposition". First, it rises by 0.5 meters to prevent the contact end from interfering with the blade; then it retreats by 0.3 meters to escape the airflow backflow area; finally, it flies to the next preset test point for further testing. Each blade is provided with 3-5 test points, distributed at the root, middle, and end of the blade, to comprehensively evaluate the continuity and conduction state of the lightning protection channel.

[0067] Further, in the data processing and compensation step, the data processing unit performs average calculation on the received multiple sets of resistance value data, and eliminates abnormal data with a deviation of more than 20% from the average value. Finally, the effective value of the blade conduction resistance is calculated, and when the effective value is greater than 0.24 ohms, the system automatically marks the blade as an abnormal conduction state. In the calculation, the data processing unit compares the detection results with the historical detection data, and when the difference exceeds 10%, a trend analysis report is automatically generated, which includes the blade number, detection time, measurement position coordinates and on-resistance change curve, and is stored in the ground database; After the data processing and compensation steps, the unmanned aerial vehicle that has completed the detection automatically returns to the take-off point according to the geographical coordinates of the wind turbine tower, and during the return process, it transmits all the unuploaded detection data through the wireless communication link. After landing, the system automatically generates a complete detection task record file, which includes the flight path, flight time, resistance values at each test point and environmental temperature and humidity parameters, providing a complete archive for wind farm operation and maintenance. During the entire detection process, the flight control system and the lightning detection system of the unmanned aerial vehicle use hierarchical permission management. The attitude adjustment signal of the flight control system and the current output signal of the detection system do not interfere with each other. The two systems are connected through an isolated communication bus, which includes a CAN bus main line and an optical isolation module, to ensure the independent operation of the flight control system and the detection system.

[0068] The data processing unit statistically analyzes multiple sets of on-resistance data to ensure that the detection results are scientific and reliable. The system first removes outliers with a deviation of more than 20% of the average value from the collected raw data to eliminate errors caused by transient instability or interference noise. Then, the effective average value is calculated to obtain the equivalent on-resistance of the blade lightning protection channel.

[0069] According to industry standards, when the on-resistance value is greater than 0.24Ω, it means that the blade lightning protection on-resistance performance may be abnormal, such as loose connection of the lightning arrester, internal wire breakage or poor grounding. The system will automatically mark the blade number and generate an alarm prompt after determining the abnormality.

[0070] Further, the system compares and analyzes the current detection data with the historical detection records. If the difference exceeds 10%, a trend analysis report is generated. The report contains the blade number, detection time, spatial coordinates and on-resistance change curve, which can be used by operation and maintenance personnel to determine the degradation trend of lightning protection performance. The trend analysis function can realize predictive maintenance, helping wind farms to discover potential hazards in advance and avoid lightning damage.

[0071] After the detection is completed, the unmanned aerial vehicle automatically returns to the take-off point according to the geographical coordinates of the tower. During the return process, the system automatically transmits the unuploaded data to ensure data integrity. After landing, the detection task record file is automatically generated, including flight path, test point resistance value, flight time, environmental temperature and humidity, etc., providing a complete archive for wind farm operation and maintenance.

[0072] The hierarchical authority management structure between the flight control system and the lightning detection system is the key to ensure safety and stability. The two systems communicate through the optoelectronic isolated CAN bus, realize command interaction but do not interfere with each other. The flight control system has higher priority than the detection system, and any abnormality can immediately interrupt the detection and execute emergency avoidance or return. This design ensures that the detection system operates independently under the safety framework of the unmanned aerial vehicle, avoiding flight accidents caused by interference of the current test signal with the flight control system.

[0073] The beneficial effects of the present application are: The automatic detection of the blade lightning protection channel is realized. The system can complete the conduction performance detection of the blade lightning protection channel without manual intervention through the self-flight, positioning and attitude control of the unmanned aerial vehicle, which greatly reduces the risk of manual climbing operation.

[0074] The detection accuracy and repeatability are improved. The force-position hybrid control mechanism and multi-point pressure sensing feedback are adopted to make the airborne contact end and the lightning arrester contact stable and consistent. Combined with the constant current source measurement and contact resistance compensation algorithm, the measurement accuracy and data repeatability are significantly improved.

[0075] The system has excellent environmental adaptability. The system structure is lightweight, and the control algorithm is adaptive, so it can work stably in complex wind field environments such as mountains, seas and plateaus, and is suitable for multiple types of wind turbines.

[0076] The detection efficiency is significantly improved. A single unmanned aerial vehicle can complete the detection task of three blades of a wind turbine in a few minutes, and the detection efficiency is several times higher than that of the traditional manual method, which is suitable for batch inspection and rapid review of wind farms.

[0077] The data processing is intelligent. The ground data processing unit can automatically perform multi-point data fusion, abnormality rejection and trend analysis to generate a visual detection report, realizing intelligent diagnosis and long-term trend tracking of lightning protection performance.

[0078] The system runs safely and reliably. The flight control system and the electrical detection system use isolated communication design and do not interfere with each other. Combined with multiple safety mechanisms such as rubber damping, air damping and temperature compensation, the stability of the unmanned aerial vehicle in high-altitude environment and the electrical safety of the measurement system are ensured.

[0079] The maintenance cost is reduced, and the intelligent degree of operation and maintenance is improved. Through regular automatic inspection of unmanned aerial vehicles, wind power operation and maintenance personnel can real-time master the health status of the blade lightning protection channel, reduce the probability of failure downtime and maintenance cost, and promote the digital operation and maintenance upgrade of the wind farm. BRIEF DESCRIPTION OF DRAWINGS

[0080] Figure 1 The three-dimensional structure schematic diagram of the present application; Figure 2 The three-dimensional structure schematic diagram of the airborne contact end and the mounting bracket of the present application; Figure 3 : working state schematic diagram of the present application; Figure 4 : working state side view of the present application; Figure 5 : component connection relationship schematic diagram of the present application; In the figure: 1- unmanned aerial vehicle platform, 2- airborne contact end, 3- mounting bracket, 4- electrical measurement unit, 5- test soft cable, 6- data processing unit, 7- ground end tester, 11- force bearing frame, 21- mounting seat, 22- adjustable cantilever assembly, 23- contact head assembly, 231- conductive base, 232- conductive gasket, 233- insulating support body, 31- support arm, 32- transverse reinforcing beam, 33- rubber damping pad. DETAILED DESCRIPTION

[0081] The present application will be further described below in conjunction with the drawings and specific embodiments: Embodiment: as shown, the present application provides a wind turbine blade lightning protection intelligent detection system based on unmanned aerial vehicle and a detection method thereof, aiming to solve the problems of low detection efficiency, high artificial risk coefficient and insufficient detection precision in the prior art. Figures 1-5

[0082] The system as a whole is composed of an unmanned aerial vehicle platform 1, an airborne contact end 2, an electrical measurement unit 4, a ground data processing unit 6 and a ground grounding connection device, etc. Each part works cooperatively through electrical and wireless communication methods to form an intelligent detection platform that can work autonomously in the air.

[0083] The unmanned aerial vehicle platform 1 is the flight and positioning carrier of the system, and is provided with a flight control module and a positioning module in its structure. The flight control module includes a propulsion motor, a gyroscope, an accelerometer, a barometer and a control circuit board, which are used to complete the flight attitude stabilization and trajectory control of the unmanned aerial vehicle. The positioning module can adopt a fusion positioning method of GNSS (Global Navigation Satellite System), IMU (Inertial Measurement Unit) and visual recognition module to realize high-precision hovering and autonomous positioning of the unmanned aerial vehicle around the wind turbine blade. The unmanned aerial vehicle platform 1 is in the form of four-rotor or six-rotor to improve the wind resistance performance and load capacity.

[0084] ​The airborne contact end 2 is installed below the unmanned aerial vehicle platform 1, and is an execution unit for electrical contact and signal acquisition of the system and the lightning receptor of the wind turbine blade. The airborne contact end 2 comprises a mounting seat 21, an adjustable cantilever assembly 22 and a contact head assembly 23. The mounting seat 21 is fixedly connected with the bottom of the unmanned aerial vehicle body through a mounting bracket 3; the adjustable cantilever assembly 22 is composed of an outer sleeve and an inner extension rod, can be extended and retracted along the axial direction, and the extension length is adjusted through a locking pin; the contact head assembly 23 is composed of a conductive base 231, a conductive gasket 232 and an insulating support 233, the conductive gasket 232 is located at the front end for contacting with the lightning receptor of the blade, and the conductive base 231 is internally provided with a sensor installation cavity, in which at least three force sensors and one displacement sensor are embedded, for detecting the contact pressure and displacement change in real time.

[0085] A rubber damping sleeve and an air damping cavity are arranged between the inner extension rod and the outer sleeve of the adjustable cantilever assembly 22 to form a passive buffering structure, which can effectively absorb the impact energy generated by the unmanned aerial vehicle in the contact moment, and prevent contact overload. The conductive base 231 is coated with an electrical isolation layer outside, and the isolation layer comprises a polyimide film layer and an epoxy resin coating layer, which is used to prevent current leakage and improve insulation safety.

[0086] The electrical measurement unit 4 is fixedly installed at the bottom of the unmanned aerial vehicle platform 1, and the shell thereof adopts a layered sealing structure, comprising an upper layer signal acquisition cabin and a lower layer conduction test cabin. The upper layer cabin is provided with a printed circuit board, which integrates an analog-to-digital conversion chip, a signal filtering circuit, a microprocessor and a temperature compensation module; the lower layer cabin is provided with a constant current source, a test terminal and a relay switching assembly, which are used to output a measurement current and acquire a voltage signal. A waterproof partition plate and an insulating bushing are arranged between the two cabins, and the overall protection level reaches IP65 or above. The electrical measurement unit 4 is electrically connected with the ground terminal tester 7 through a test flexible cable 5, so as to establish a measurement loop between the unmanned aerial vehicle and the ground.

[0087] The ground data processing unit 6 is usually a portable industrial computer or a tablet terminal, which runs data processing and judgment algorithms inside, and is mainly used for compensating, filtering, averaging and removing abnormal values of the conduction resistance data, and judging the conduction performance of the lightning protection channel of the blade based on threshold standards. The ground data processing unit 6 also has a wireless communication module, and keeps real-time data interaction with the unmanned aerial vehicle platform 1.

[0088] The ground grounding connection device is arranged at the tower base of the wind turbine, and comprises a grounding clamp, a conductive flexible cable and a grounding terminal. The grounding clamp is used to form reliable electrical connection with the tower grounding copper bar or grounding bolt, and the conductive flexible cable connects the grounding clamp and the grounding end of the ground terminal tester 7 to form a complete conduction detection loop. The outer layer of the flexible cable is provided with a wear-resistant insulating sheath, and can be wound and unwound through a winding disc.

[0089] Through the above structure, the system can complete the conduction performance detection of the lightning protection channel of the wind turbine blade under the condition of unattended, and has the characteristics of high automation, high measurement accuracy and strong adaptability.

[0090] In order to ensure that the unmanned aerial vehicle is safe and reliable in the process of performing the detection task and the electrical measurement equipment on the ground, the test flexible cable 5 adopts a light and flexible conductive structure, the core wire of which is twisted by a plurality of superfine silver-plated copper wires, the outer layer is covered with a double-layer insulating sheath, the inner layer is a polyurethane soft protective layer, and the outer layer is a high polymer wear-resistant layer. The overall diameter is less than 5mm, and the unit length mass is not more than 50g / m.

[0091] One end of the test flexible cable 5 is connected to the electrical measurement unit 4 at the bottom of the unmanned aerial vehicle through a quick plug-in interface, and the other end is connected to the ground test instrument 7.

[0092] The electrical measurement unit 4 collects voltage and current of the conduction loop between the contact end 2 of the unmanned aerial vehicle and the grounding end of the wind turbine, and obtains original measurement data; the original measurement data is transmitted to the data processing unit 6 on the ground through a wireless communication link. The ground test instrument 7 only serves as a ground interface module of the electrical measurement loop and is electrically connected to the electrical measurement unit 4 through the test flexible cable 5, providing a conduction path and overcurrent protection function, and does not participate in data processing. The data processing unit 6 performs compensation calculation, filtering and judgment processing on the received original data, outputs the detection result according to the preset conduction resistance threshold or trend analysis algorithm, and generates a detection report file.

[0093] That is, in the system architecture of the present application, the communication between the data processing unit 6 and the electrical measurement unit 4 is wireless communication, and there is no direct cable connection between them; the ground test instrument 7 is only responsible for providing a stable grounding interface and safety protection function, and does not participate in signal acquisition and data calculation. This structure effectively isolates the high-current measurement loop and the low-voltage data processing system, improving the safety and anti-interference performance of the system.

[0094] In order to reduce the influence of the test flexible cable 5 on the flight attitude of the unmanned aerial vehicle platform 1, the flexible cable is dynamically managed by the automatic winding and unwinding mechanism arranged on the ground. The winding mechanism includes an adjustable tension spring, a guide pulley and a speed feedback module, which can automatically adjust the winding and unwinding speed according to the lifting speed of the unmanned aerial vehicle, so that the test flexible cable 5 always maintains a slightly tight state without swinging during flight.

[0095] During the take-off, landing and hovering of the unmanned aerial vehicle, the controller of the winding mechanism automatically adjusts the length of the unwinding line according to the height information of the unmanned aerial vehicle (obtained through wireless height signal or tension sensor feedback), so as to avoid the test flexible cable 5 from winding or dragging the ground objects. The maximum effective length of the test flexible cable 5 is 15 meters, which can cover the common wind turbine blade detection height range.

[0096] In order to prevent the test flexible cable 5 from being interfered by electromagnetic wave during the detection of current transmission, a shielding layer is arranged inside the flexible cable, the shielding layer adopts a tinned copper braid and is reliably connected with the ground layer of the unmanned aerial vehicle electrical measurement unit 4; meanwhile, an ultraviolet resistant coating is arranged on the outer surface of the flexible cable, so as to improve the weather resistance of long-term outdoor use.

[0097] In use, the tension of the test flexible cable 5 is not more than 2N, when the tension exceeds the preset value, the winding mechanism automatically stops the unmanned aerial vehicle from descending and sends an alarm signal. The design ensures the electrical continuity, mechanical safety and signal stability of the test flexible cable 5 during the detection of the unmanned aerial vehicle in the autonomous flight.

[0098] The detection results (including resistance value, trend curve and determination conclusion) of the application are calculated and generated by the data processing unit 6 on the ground and are output, which can be provided to the operation and maintenance management system through a display terminal, a report or a wireless transmission mode. Therefore, the conduction resistance measurement results of the application are output by the data processing unit 6 on the ground, and the ground tester 7 only exists as an electrical connection and protection device.

[0099] In order to further improve the connection reliability during flight, the interface between the test flexible cable 5 and the electrical measurement unit 4 adopts a magnetic attraction type anti-dropping structure. The interface is composed of a female metal seat and a male pin, the magnetic attraction force is about 3N, and the contact can be automatically maintained when the unmanned aerial vehicle has a small pose change. A waterproof sealing ring is arranged in the interface, and the protection level reaches IP65.

[0100] When the unmanned aerial vehicle returns to the take-off point, the operator can directly pull out the test flexible cable 5 for maintenance without additional tools.

[0101] In order to ensure the contact stability of the airborne contact end 2 and the wind power blade lightning arrester, the system adopts a hierarchical distributed closed-loop control architecture.

[0102] Wherein: The position control closed loop is executed by the flight control module of the unmanned aerial vehicle platform 1, and the attitude of the unmanned aerial vehicle and the spatial position are adjusted in real time through an attitude sensor (including a three-axis gyroscope, an accelerometer and a visual positioning unit); The force control closed loop is executed by the local controller of the airborne contact end 2, and the controller is integrated on a microprocessor chip in the electrical measurement unit 4.

[0103] The data interaction between the two closed loops is realized through an isolation communication bus (CAN bus + optoelectronic isolation module), and the loose coupling cooperative control is realized.

[0104] Specifically, the flight control module maintains the UAV at a predetermined position near the lightning receptor according to the positioning information, while the force control loop adjusts the micro-extension amount of the adjustable cantilever assembly 22 according to the real-time signals of the force sensor and the displacement sensor, so that the contact pressure is kept within the target value (5N-10N) range.

[0105] During the control process, when the force sensor detects that the contact force fluctuation exceeds ±1N, the local controller sends a fine-tuning instruction to the flight control module through the communication bus to correct the UAV attitude angle or position error, so as to maintain stable contact. This structure makes the flight attitude adjustment and contact force control independent of each other, ensuring the stability and data consistency of the detection process.

[0106] In the present application, in order to prevent the on-board contact end 2 from causing leakage, flashover or interference under high voltage or static conditions, the electrical isolation layer is used to comprehensively insulate the non-contact area of the conductive base 231.

[0107] Specifically, the electrical isolation layer covers the non-contact area of the conductive base 231 in the axial direction of the contact head assembly 23, that is, the remaining conductive base 231 surface except the conductive gasket 232 is covered.

[0108] The coating layer adopts a double-layer structure: the inner layer is a polyimide film layer with a thickness of 0.3mm-0.6mm, which is used to provide basic insulation performance; the outer layer is an epoxy resin coating layer with a thickness of 0.3mm-0.4mm, which is used to enhance mechanical strength and weather resistance. The two layers are combined into a whole through a hot pressing composite process, and the surface is smooth without bubbles.

[0109] Through testing, the insulation layer has a withstand voltage performance of not less than 5MΩ under 500VDC, which can effectively prevent the parasitic current or static discharge phenomenon caused by the approach of the non-working surface of the conductive base 231 to the blade surface.

[0110] In addition, in order to prevent the electric field from concentrating at the edge of the conductive gasket 232, the isolation layer adopts a round corner transition structure (round corner radius 0.5-1.0mm) at the edge of the conductive gasket 232 and the base connection, so as to smooth the electric field distribution and improve the withstand voltage safety.

[0111] In order to ensure the long-term stable operation of the system in outdoor high-humidity environment, the signal acquisition cabin and the conduction test cabin of the electrical measurement unit 4 are separated by an integrated sealing partition.

[0112] The partition adopts an aluminum alloy plate with a thickness of 2mm, and a silicone rubber waterproof ring is embedded around it, with a sealing level of IP54.

[0113] The partition is provided with a threading hole, and a polytetrafluoroethylene (PTFE) insulating bushing is installed in the hole, which not only plays an electrical isolation role, but also prevents liquid from seeping in.

[0114] All the connector surfaces are treated with nickel plating anti-corrosion process.

[0115] To ensure the accuracy of the measurement data, the electrical measurement unit 4 uses a multi-layer shielding and filtering structure in the signal acquisition channel: The printed circuit board is a four-layer structure, containing independent signal and ground layers, with signal lines and power lines laid separately; The signal filtering unit is composed of series inductance and parallel capacitance, with 50-150 turns of inductance and 100nF-470nF of capacitance, the specific values being determined according to the test current spectrum (DC to 5kHz); An RC anti-aliasing filter network is added to the input end of the analog-to-digital conversion chip to prevent high-frequency noise from introducing errors; The inner surface of the electrical measurement unit 4 shell is sprayed with a conductive plating layer and grounded, forming a whole electromagnetic shielding cavity.

[0116] Through the above structural design, the signal can still remain stable in a strong electromagnetic interference environment, with a measurement error of not more than ±0.01Ω.

[0117] A pressure balance valve is also provided at the bottom of the conduction test cabin shell, which uses a waterproof air permeable membrane structure to balance the internal and external pressure difference while keeping the inside dry, thereby preventing structural deformation of the airtight cabin body at high altitudes or when the air pressure changes.

[0118] The wind turbine blade lightning protection intelligent detection method based on the unmanned aerial vehicle includes the following main steps: Task preparation and system verification: Before detection, the operator sets the wind turbine number and blade parameters at the ground end and inputs the spatial coordinates and attitude parameters of the wind turbine into the ground station system. After the unmanned aerial vehicle platform 1 is powered on, the flight control system, sensor module, electrical measurement unit 4 and communication link are sequentially self-checked. After the self-checking is passed, the system automatically performs zero point calibration and signal stability test. If any module is abnormal, the system will automatically alarm and prohibit take-off.

[0119] Three-dimensional coordinate model establishment: A three-dimensional coordinate model is established according to the geometric data of the wind turbine tower and the blade. The model takes the center of the tower as the origin, the blade axis direction as the X axis, the blade normal direction as the Y axis, and the tower vertical direction as the Z axis, forming a spatial reference coordinate system. The unmanned aerial vehicle determines its position through the GNSS and visual SLAM fusion algorithm, and matches it with the three-dimensional model, thereby generating the optimal flight reference path.

[0120] Unmanned aerial vehicle positioning and attitude adjustment: After the UAV takes off, it flies along the preset path to the vicinity of the target blade. The flight control module collects three-axis gyroscope and accelerometer data, and the attitude angle error is corrected by the extended Kalman filter algorithm, so that the normal direction of the contact end deviates from the normal direction of the blade surface within 3°. In this stage, the UAV maintains a stable hovering attitude to prepare for contact operation.

[0121] Stage speed reduction approach and contact action: The UAV gradually approaches the blade surface at a preset stage descent speed: The first stage quickly descends at a speed of 1.0-1.5 m / s above the target; The second stage slowly approaches the blade at a speed of 0.3-0.5 m / s; The third stage fine approaches at a speed not exceeding 0.1 m / s, and when the proximity sensor detects a distance less than 50 mm, it automatically stops descending and hovers.

[0122] After hovering, the adjustable cantilever assembly 22 of the airborne contact end 2 is slightly stretched in the axial direction of the UAV, so that the conductive pad 232 forms a slight contact with the surface of the lightning arrester.

[0123] Force-position hybrid control and effective contact determination: During contact, the system collects force sensor and displacement sensor signals in real time, and adjusts the thrust and extension amount of the adjustable cantilever assembly 22 through the flight control closed-loop algorithm. When the contact pressure stabilizes in the range of 5N-10N, the system determines that the contact is effective. If overpressure or unstable contact is detected, the control system will automatically retreat and re-adjust.

[0124] Conductance measurement: After the contact is effective, the electrical measurement unit 4 starts a constant current source to establish a conduction loop between the blade lightning arrester and the ground grounding device. The constant current source outputs a stable current of 10-50 mA, and the test lasts for 3-5 seconds, while the voltage drop signal is collected and the conductance value is calculated. The signal sampling rate is not less than 100 Hz to ensure the smoothness and accuracy of the data.

[0125] Data processing and conduction determination: After the measurement is completed, the collected multiple sets of data are transmitted to the ground data processing unit 6 through the wireless link. The ground end performs multiple sampling averaging, outlier rejection and temperature compensation calculation on the data to obtain the effective conductance of the blade lightning protection channel. If the calculation result is greater than 0.24Ω, the system automatically marks the blade as "abnormal conduction"; if the result is less than or equal to the threshold, it is determined to be "normal conduction".

[0126] Trend analysis and report generation: The system compares the current detection data with the historical database, and automatically generates a trend analysis report when the conduction resistance changes by more than 10%. The report includes the blade number, test time, measurement location coordinates, and conduction resistance change curve, and is stored in the ground database for subsequent operation and maintenance.

[0127] Task completion and return record: After all the detection points are completed, the unmanned aerial vehicle platform 1 exits the blade area in turn according to the task path and returns to the take-off point. During the return process, the system automatically supplements the unuploaded data. After landing, the ground end generates a complete detection task file, records the flight path, detection point resistance value, flight time, environmental temperature and humidity, etc., and realizes task archival management.

[0128] The detection method can complete the automatic detection of the lightning protection channel of the wind power blade without manual climbing, and significantly improves the safety and efficiency of the lightning protection maintenance of the wind power plant.

[0129] The system of the present application takes the unmanned aerial vehicle platform 1 as the core, combines force-position hybrid control, electrical conduction measurement and data compensation algorithm, and realizes automatic detection of the conduction performance of the lightning protection channel of the wind turbine blade. Its working principle can be explained from four aspects of mechanical control principle, electrical measurement principle, data processing principle and system coordination mechanism.

[0130] (1) Mechanical control and attitude stabilization principle The unmanned aerial vehicle platform 1 realizes closed-loop control of attitude and position through the flight control module. The flight control module contains a three-axis gyroscope, a three-axis accelerometer, a barometer and a magnetometer module, which are used to collect the angular velocity, acceleration and height data of the unmanned aerial vehicle in real time. The system uses extended Kalman filter algorithm (EKF) to fuse and estimate the multi-sensor data, so as to obtain high-precision attitude angle and position information.

[0131] During the detection operation, the unmanned aerial vehicle needs to hover near the surface of the wind power blade for a long time, so the control algorithm adds a force feedback link based on the traditional PID control to realize force-position hybrid control. The force sensor measures the pressure value when the airborne contact end 2 contacts the blade, and the system compares this value with the target pressure (5-10N) and automatically adjusts the output power of the propulsion motor and the attitude angle according to the deviation, so that the unmanned aerial vehicle can maintain a stable force state. In this way, it can prevent the unmanned aerial vehicle from losing stable contact due to air flow disturbance or attitude drift.

[0132] When the UAV approaches the blade, its descent process adopts hierarchical speed control. The principle of this control mode is to use the speed curve in different stages to achieve contact buffering: the first stage quickly approaches the target point to save time, the second stage gradually slows down to reduce inertial impact, and the third stage approaches at ultra-low speed to ensure precise contact. In the approach stage, the ultrasonic ranging module and the visual recognition system work together to measure the distance between the UAV and the blade surface in real time. When the distance is less than 50 mm, the system automatically triggers the "hover mode" to stop descending and keep the attitude locked.

[0133] The adjustable cantilever assembly 22 plays a role in micro-displacement compensation during the contact stage. The rubber damping sleeve inside it and the air damping cavity form a passive buffer, which absorbs contact energy by air compression and rubber elasticity to achieve compliant contact. Since the air damping cavity is connected to the outside through micro-holes, it can slowly release air at the moment of contact, achieving the effect of fluid damping shock absorption, avoiding excessive compression of the blade surface by the conductive pad 232.

[0134] (2) Electrical conduction measurement principle The basic principle of the electrical measurement unit 4 is to measure the conduction resistance based on the constant current method. The system applies a stable current (10-50 mA) between the blade lightning arrester and the tower cylinder grounding end through a constant current source, and simultaneously collects the voltage drop signal. According to Ohm's law R=U / I, the total resistance of the lightning protection channel is calculated.

[0135] The test cable 5 between the electrical measurement unit 4 and the ground end tester 7 adopts a shielding structure, and the internal wires are tin-plated to reduce contact oxidation. Through a wireless communication link, measurement data are transmitted in real time to the ground data processing unit 6, realizing synchronization of measurement and analysis.

[0136] (3) Data processing and intelligent judgment principle The core task of the ground data processing unit 6 is to comprehensively analyze the collected multiple sets of conduction resistance data to determine whether the blade lightning protection channel is in a normal state.

[0137] The data processing process includes the following steps: The original resistance data of each test point are subjected to sliding average and median filtering to eliminate incidental noise; All test point data are subjected to outlier rejection, and if the deviation of a certain set of data from the average value exceeds 20%, the system automatically rejects it; The average value of the valid data is calculated to obtain the overall conduction resistance of the blade; When the value exceeds 0.24Ω, it is determined to be "abnormal conduction"; if it is less than or equal to 0.24Ω, it is determined to be "normal conduction".

[0138] In addition, the system is built-in trend analysis module for monitoring long-term conduction changes. When the test results change more than 10% compared with historical data, the system automatically generates a trend analysis report. The report contains the test time, blade number, test location coordinates and conduction resistance change curve, which can provide early warning of lightning protection performance degradation for operation and maintenance personnel.

[0139] (4) System coordination and security mechanism The UAV platform 1 and the detection system are connected through an isolated communication bus to ensure that the flight control signal and the current output signal do not interfere with each other. The isolated bus is composed of a CAN main line and an optical isolation module to prevent high-voltage current feedback from interfering with the flight control system. The flight control system has the highest priority control authority. When the detection system is abnormal (such as current anomaly, force sensor alarm, etc.), the UAV automatically enters a safe mode and leaves the blade area.

[0140] The entire system is a single closed loop circuit, and the test current rises from the ground grounding end to the UAV platform 1 through the test soft cable 5, and then enters the blade lightning arrester, lightning protection channel and tower grounding net through the airborne contact end 2, and returns to the ground. This closed loop design ensures that the measurement path is complete and the signal is continuous, avoiding errors caused by floating ground or interference current.

[0141] In typical applications, the system of the present application can perform detection operations under the condition that the wind speed is less than 8 m / s. The operator only needs to set the UAV take-off point on the ground, input the wind turbine number and detection task parameters, and the system can automatically plan the path and execute the detection task. Three blades of each wind turbine can complete the conduction detection within 10 minutes, and the detection efficiency is more than 3 times higher than that of manual methods.

[0142] When the UAV approaches the wind turbine blade, its flight attitude is greatly affected by wind field disturbance. The present application realizes dynamic stable hovering through attitude closed-loop control and force feedback adjustment, which can maintain constant contact pressure even in the case of sudden wind speed changes or blade micro-vibration. The rubber damping and air damping structure further improves the mechanical cushioning performance, effectively preventing damage between the conductive gasket 232 and the blade surface.

[0143] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made shall be included in the protection scope of the present application.

Claims

1. An unmanned aerial vehicle (UAV)-based lightning protection intelligent detection system for a wind turbine blade, characterized in that, The system comprises: an unmanned aerial vehicle platform for autonomous flight and hovering positioning around a wind turbine blade, the unmanned aerial vehicle platform comprising a positioning module and a flight control module for realizing attitude holding and precise positioning of the unmanned aerial vehicle at a predetermined position; an on-board contact terminal mounted on the unmanned aerial vehicle platform for forming electrical contact with a lightning receptor of the wind turbine blade, the on-board contact terminal being provided with a force sensor and a displacement sensor, the force sensor being used for detecting contact pressure, and the displacement sensor being used for detecting contact position; the unmanned aerial vehicle platform performs force and displacement hybrid control according to sensor signals to maintain stable contact; an electrical measurement unit mounted at the bottom of the unmanned aerial vehicle platform and electrically connected with the on-board contact terminal, for forming a measurement loop between the on-board contact terminal and a grounding terminal of the wind turbine and measuring the conduction resistance of a lightning protection channel of the blade; the electrical measurement unit is electrically connected with a ground terminal tester through a test flexible cable; a data processing unit arranged at the ground and communicatively connected with the electrical measurement unit, for performing contact resistance compensation, filtering and judgment processing on the measurement results and outputting the conduction performance results of the lightning protection channel; a ground grounding connection device arranged at the tower base of the wind turbine, for forming temporary electrical connection with a grounding grid of the wind turbine during detection and being electrically connected with a grounding terminal of the ground terminal tester through a lead wire, thereby forming a complete conduction detection loop; wherein the system realizes automatic contact of the blade lightning receptor through precise positioning and force and displacement hybrid control of the unmanned aerial vehicle platform, and realizes high-precision detection of the conduction performance of the lightning protection channel of the wind turbine blade in combination with high-precision measurement of the electrical measurement unit and compensation algorithms of the data processing unit.

2. The system of claim 1, wherein, The on-board contact terminal comprises a mounting seat, an adjustable cantilever assembly and a contact head assembly. The mounting seat is fixedly arranged at the bottom center of the unmanned aerial vehicle platform. One end of the adjustable cantilever assembly is hingedly connected with the mounting seat, and the other end is connected with the contact head assembly. The adjustable cantilever assembly comprises a coaxially arranged outer sleeve and an inner extension rod; the inner extension rod can slide along the axial direction in the outer sleeve and is limited by a locking pin; the adjustable cantilever assembly and the mounting seat can be fixed at a certain relative position. The contact head assembly comprises a conductive base, a conductive gasket and an insulating support. The conductive base is fixedly connected with the front end of the adjustable cantilever assembly through a threaded connection mode. The conductive gasket is arranged on the front end surface of the conductive base, and the conductive gasket has a disc shape with a diameter less than two-thirds of the diameter of the conductive base. The insulating support is sleeved on the outer peripheral surface of the conductive base, and the conductive base and the insulating support are positioned by an annular clamping groove. The conductive base of the contact head assembly is provided with a sensor mounting cavity, the central axis of the mounting cavity coincides with the normal direction of the conductive gasket, and at least three force sensors distributed in the circumferential direction are embedded in the mounting cavity, the sensing surface of the force sensor faces the back surface of the conductive gasket and tightly abuts against the back surface, and the force sensor is electrically connected with the electrical measurement unit through a lead wire. The inner extension rod of the adjustable cantilever assembly is sleeved with a rubber damping sleeve, the damping sleeve is provided with a plurality of uniformly distributed annular grooves in the axial direction, the inner wall of the outer sleeve is in clearance fit with the rubber damping sleeve, and an air damping cavity is formed between the rubber damping sleeve and the inner wall of the outer sleeve during the extension and retraction of the inner extension rod, and the air damping cavity is communicated with the outside through a micro hole; An electrical isolation layer is arranged between the contact head assembly and the adjustable cantilever assembly, the electrical isolation layer comprises a two-layer structure, the inner layer is a polyimide film layer, and the outer layer is an epoxy resin coating layer; the electrical isolation layer covers the non-contact part of the conductive base along the axial direction of the contact head assembly, and the thickness of the electrical isolation layer ranges from 0.3 mm to 1.0 mm; The ground grounding connection device comprises a grounding clamp, a conductive flexible cable and a grounding terminal; The grounding clamp is used to form a detachable electrical connection with the exposed grounding copper bar or grounding bolt of the wind turbine tower base; One end of the conductive flexible cable is electrically connected with the grounding clamp, and the other end is connected with the input end of the ground terminal tester through the grounding terminal, so that the airborne contact end, the lightning protection channel of the blade, the grounding net of the tower base and the ground terminal tester form a closed conduction detection loop; The outer layer of the conductive flexible cable is covered with a wear-resistant insulating sheath, the length of the conductive flexible cable is 5-15 meters, and the conductive flexible cable is arranged through a winding disc or a support during use; The grounding clamp and the conductive flexible cable are fixed by crimping or threaded connection, and the contact part is plated with tin to prevent corrosion; The grounding terminal is made of copper alloy material, and a locking structure is arranged at the end of the grounding terminal to ensure stable connection; The test flexible cable is arranged along the flight path of the unmanned aerial vehicle and can be extended and retracted, and is used to maintain the electrical path between the airborne contact end and the ground grounding connection device during detection.

3. The system of claim 2, wherein, The airborne contact end is connected with the mounting platform at the lower part of the unmanned aerial vehicle body through a mounting bracket, The mounting bracket comprises a support arm in inverted U-shaped structure and a transverse reinforcing beam; The two ends of the support arm are connected with the force bearing frame arranged below the unmanned aerial vehicle body through bolts respectively; The reinforcing beam is fixedly arranged between the support arms and is arranged perpendicular to the longitudinal axis of the unmanned aerial vehicle; the mounting seat is fixedly arranged at the lower center position of the reinforcing beam through screws; Rubber damping pads are arranged at the two ends of the support arm of the mounting bracket respectively, the damping pads are connected with the force bearing frame of the unmanned aerial vehicle through screws, the thickness of the damping pads is 5-15 mm, and a plurality of through holes extending in the vertical direction are embedded in the damping pads to form air buffer cavities, the number of the air buffer cavities is 3-6, and the air buffer cavities are uniformly distributed along the length direction of the support arm.

4. The system of claim 2, wherein, The electrical measurement unit is fixedly connected at the bottom of the unmanned aerial vehicle platform and comprises a signal acquisition cabin arranged at the upper layer and a conduction test cabin arranged at the lower layer; A printed circuit board is arranged in the signal acquisition cabin, and an analog-to-digital conversion chip, a signal filtering unit and a microprocessor chip are fixedly installed on the printed circuit board; A test connection terminal and a relay switching assembly are arranged in the lower conduction test cabin, the signal acquisition cabin and the conduction test cabin are separated by a sealed partition plate, a waterproof sealing ring and a threading hole are embedded on the partition plate, and an insulating bushing is installed in the threading hole; The signal filtering unit comprises a set of parallel inductive elements and capacitive elements, the inductive elements are arranged in series along the signal input path, the capacitive elements are connected between the signal input end and the common ground end respectively, the number of turns of the inductive elements is 50-150 turns, the capacitance of the capacitive elements is 100 nF-470 nF, the whole filtering unit is welded on the inner layer conductor of the multilayer circuit board, the circuit board adopts a four-layer structure, and the inner layer is provided with independent signal layers and ground layers. A temperature compensation circuit is arranged on the printed circuit board in the signal acquisition cabin, and the temperature compensation circuit comprises a temperature sensing element, a voltage reference source and an operational amplifier unit. The temperature sensing element is installed at the edge position of the printed circuit board, and the temperature sensing surface thereof is arranged towards the direction of the on-off test cabin, the temperature sensing element and the operational amplifier unit are connected through wires, and the voltage reference source is connected with the analog input end of the microprocessor chip.

5. An unmanned aerial vehicle (UAV)-based lightning detection method for wind turbine blades according to the system of any one of claims 1-4, characterized in that, The method comprises the following steps: Task preparation and system verification: self-checking and calibration of the unmanned aerial vehicle platform, the airborne contact end, the electrical measurement unit and the ground grounding device are performed to ensure that the system communication and measurement state are normal; Positioning and attitude adjustment: the unmanned aerial vehicle platform is controlled to fly to the vicinity of the lightning receptor of the wind turbine blade, the position information of the unmanned aerial vehicle is obtained through the positioning module, and the attitude of the unmanned aerial vehicle is adjusted to the predetermined detection position based on visual recognition or sensing feedback; Contact and measurement: the airborne contact end is driven to make electrical contact with the lightning receptor, and the contact pressure and contact position are stably controlled through the feedback of the force sensor and the displacement sensor; then a measurement loop is established between the airborne contact end and the ground grounding device, and the on-off resistance data is collected; Data processing and compensation: the measured on-off resistance data is subjected to contact resistance compensation, filtering and multiple sampling averaging to obtain the actual on-off resistance value of the lightning protection channel of the blade; Then the actual on-off resistance value is compared with the preset standard threshold value to determine whether the lightning protection channel meets the on-off requirement, and a detection result report is generated.

6. The method of claim 5, wherein, In the task preparation and system verification step, a three-dimensional coordinate model is established according to the spatial attitude parameters of the wind turbine blade before the unmanned aerial vehicle takes off, the three-dimensional coordinate model takes the center of the wind turbine tower as the origin, takes the blade axis direction as the X axis, takes the blade normal direction as the Y axis, and takes the tower axial direction as the Z axis, the unmanned aerial vehicle determines its spatial coordinates through the fusion positioning of the global navigation satellite system and the visual recognition system, and matches them with the three-dimensional coordinate model to generate a flight reference path.

7. The method of claim 6, wherein, In the positioning and attitude adjustment step, the attitude of the unmanned aerial vehicle is adjusted by the flight control module when the unmanned aerial vehicle moves along the flight reference path; The flight control module collects three-axis gyroscope signals and accelerometer signals respectively, and corrects the attitude angle error in real time through the extended Kalman filtering algorithm, so that the spatial attitude of the airborne contact end of the unmanned aerial vehicle keeps the deviation angle with the normal direction of the blade surface within 3°.

8. The method of claim 6, wherein, In the contact and measurement step, the descent speed is controlled in a stepwise deceleration manner when the unmanned aerial vehicle approaches the blade, and the descent process is divided into three stages: The descent speed in the first stage is 1.0-1.5 m / s; The descent speed in the second stage is 0.3-0.5 m / s; The descent speed in the third stage is 0.1-0.2 m / s. The third stage descending speed is not more than 0.1 m / s, In the third stage, the airborne contact end stops descending and keeps hovering when the proximity sensor detects that the distance to the blade surface is less than 50 mm.

9. The method of claim 5, wherein, In the contact and measurement step, after the UAV keeps hovering, the adjustable cantilever assembly of the airborne contact end is slightly stretched along the longitudinal axis direction of the UAV to make the conductive pad of the contact head assembly form mechanical contact with the blade lightning arrester; After the contact is completed, the static time is 2-3 seconds, during which the force sensor in the airborne contact end detects the contact pressure value, and when the contact pressure is in the range of 5-10 N, the system determines that the contact is effective and enters the conduction test stage; In the conduction test stage, the conduction test cabin outputs a constant current signal, the amplitude of the constant current is 10-50 mA, the test duration is 3-5 seconds, the voltage drop data is recorded synchronously by the signal acquisition cabin, and the resistance value from the blade lightning arrester to the tower bottom grounding net is calculated, and the test result is transmitted in real time to the data processing unit through the wireless communication module; the data processing unit is set on the ground; After the conduction test is completed, the UAV automatically rises 0.5 m and retreats 0.3 m, and then the UAV moves to the next preset contact point position to repeat the test steps, the number of test points for each blade is 3-5, and each test point is uniformly distributed along the length direction of the blade.

10. The method of claim 5, wherein, In the data processing and compensation step, the data processing unit averages the received multiple sets of resistance value data, and eliminates abnormal data deviating from the average value by more than 20%, and finally calculates the effective value of the blade conduction resistance, when the effective value is greater than 0.24 ohm, the system automatically marks the blade as conduction abnormal state; In the calculation, the data processing unit compares the detection result with the historical detection data, when the difference exceeds 10%, a trend analysis report is automatically generated, which includes blade number, detection time, measurement position coordinates and conduction resistance change curve, and is stored in the ground database; After the data processing and compensation step, the UAV that has completed the detection returns to the take-off point according to the geographical coordinates of the wind turbine tower, and during the return process, all unuploaded detection data is supplemented through the wireless communication link, after landing, the system automatically generates a complete detection task record file, which includes flight path, flight time, resistance value of each test point and environmental temperature and humidity parameters; In the whole detection process, the flight control system and the lightning protection detection system of the UAV adopt hierarchical permission management, the attitude adjustment signal of the flight control system and the current output signal of the detection system do not interfere with each other, the two systems are connected through an isolation communication bus, which includes a CAN bus main line and an optical isolation module, to ensure the independent operation of the flight control system and the detection system.

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