Unmanned aerial vehicle autonomous inspection method and system based on distribution line electromagnetic characteristic driving

Abstract

The invention provides an unmanned aerial vehicle autonomous inspection method and system based on distribution line electromagnetic characteristic driving, an electromagnetic sensor array is carried on an unmanned aerial vehicle, three electromagnetic sensors are adopted to form a triangular arrangement, the two electromagnetic sensors are arranged along the flight direction of the unmanned aerial vehicle, and the connecting line points to the direction of the head of the unmanned aerial vehicle. The relative attitude of the unmanned aerial vehicle and the distribution line is judged; the third electromagnetic sensor is arranged on the other side of the triangle formed by the third electromagnetic sensor and the connecting line and is used for estimating the transverse distance between the unmanned aerial vehicle and the distribution line; the flight height of the unmanned aerial vehicle is obtained by an airborne barometer, and the flight height of the unmanned aerial vehicle is set according to the height of the distribution line in the area. The unmanned aerial vehicle has the advantages that the electromagnetic sensor array is used for collecting electromagnetic signals of the distribution line, the relative position relation between the unmanned aerial vehicle and the distribution line is estimated according to the electromagnetic field distribution condition, autonomous navigation flight of the unmanned aerial vehicle is achieved, GNSS dependence is reduced, and effective routing inspection is conducted in GNSS signal attenuation or interruption zones.

Description

Technical Field

[0001] The present invention belongs to the field of unmanned aerial vehicle (UAV) flight control, and relates to a flight attitude control technology for UAVs inspecting power distribution lines. Background Art

[0002] With the continuous expansion of power systems and the continued advancement of smart grid construction, distribution line inspections are becoming increasingly important. Traditional manual inspection methods are not only labor-intensive and inefficient, but also pose significant safety risks at high altitudes, in complex terrain, or in extreme weather conditions. In recent years, thanks to the development of drone technology, drone-based distribution line inspections have gradually become an efficient and intelligent emerging method. However, current drone inspection systems rely heavily on GNSS (Global Navigation Satellite System) navigation, which presents numerous challenges in practical application.

[0003] On the one hand, power distribution lines are sometimes located in mountainous and forested areas with complex terrain. Satellite signals in these areas are easily affected by factors such as mountain obstruction, vegetation cover, and undulating terrain. This can cause GNSS signal attenuation or interruption, making it difficult for drones to obtain stable and reliable location information, leading to positioning drift. On the other hand, high-voltage distribution lines generate strong power-frequency electromagnetic fields during operation. This electromagnetic environment can significantly interfere with sensitive sensors such as magnetometers on drones, causing the drones to misjudge their heading and abnormal attitude control, making it difficult for them to fly autonomously using GNSS signals.

[0004] Therefore, a method for autonomous drone navigation is needed that is independent of external positioning systems and adapts to the complex electromagnetic environment of distribution lines. During high-voltage power transmission, distribution lines generate a stable electromagnetic field distribution with predictable and regular spatial patterns. If electromagnetic sensors can be used to sense the electromagnetic field intensity in real time and estimate the relative position of the drone and the distribution line based on the sensing results, electromagnetic sensing navigation of the distribution line can be achieved, thereby guiding the drone to fly along the line at a fixed safe distance without the need for GNSS. Summary of the Invention

[0005] In response to the shortcomings of current technologies, the present invention proposes an autonomous inspection method of UAVs driven by electromagnetic characteristics of distribution lines, and also proposes a corresponding system.

[0006] The technical solution of the present invention is: an autonomous inspection method for drones driven by the electromagnetic characteristics of distribution lines, in which an electromagnetic sensor array is carried on a rotor-type drone, and three electromagnetic sensors are arranged in an equilateral triangle. Among them, the first electromagnetic sensor and the second electromagnetic sensor are arranged along the flight direction of the drone, and the connecting line thereof is parallel to the direction of the nose, and are used to judge the relative posture of the drone and the distribution line; the third electromagnetic sensor is arranged on one side of the connecting line formed by the first electromagnetic sensor and the second electromagnetic sensor, and is used to estimate the lateral distance between the drone and the distribution line; the flight altitude of the drone is obtained by an onboard barometer, and the flight altitude of the drone is set according to the height of the distribution line in the area.

[0007] Furthermore, the three electromagnetic sensors are arranged in an equilateral triangle array with connecting lines, and the geometric center of gravity of the equilateral triangle coincides with the center of mass of the UAV.

[0008] For three-phase distribution lines, if the field strength measured by the first electromagnetic sensor is greater than the field strength measured by the second electromagnetic sensor, the nose of the drone will be rotated away from the distribution line. Otherwise, it needs to be rotated toward the side close to the distribution line. At the same time, according to the lateral distance estimated by the electromagnetic sensor array, the drone is controlled to move left and right to ensure that it is always within the set safe flight range.

[0009] An autonomous inspection system for drones driven by electromagnetic characteristics of power distribution lines is used to implement the above method. The system comprises three electromagnetic sensors arranged on a rotor-type drone, wherein the first electromagnetic sensor and the second electromagnetic sensor are arranged along the flight direction of the drone, and the connection line thereof is parallel to the direction of the nose of the drone, and the third electromagnetic sensor is arranged on one side of the connection line formed by the first electromagnetic sensor and the second electromagnetic sensor. A signal collector is arranged on the drone, and the signal collector is provided with a signal receiving port of the electromagnetic sensor. The drone has a built-in processor, which is connected to the signal collector. The processor is provided with an electromagnetic signal processing unit, and the electromagnetic signal processing unit processes the field strength signals of the three electromagnetic sensors. When the first electromagnetic sensor is detected, the signal receiving port is detected. When the field strength measured by the sensor is greater than the field strength measured by the second electromagnetic sensor, the electromagnetic signal processing unit will output a control signal after judgment to control the steering module of the drone to rotate the nose toward the side away from the distribution line. When the field strength measured by the first electromagnetic sensor is less than the field strength measured by the second electromagnetic sensor, the electromagnetic signal processing unit will output a control signal after judgment to control the steering module of the drone to rotate the nose toward the side close to the distribution line. The electromagnetic signal processing unit uses the field strength signal of the third electromagnetic sensor to estimate the lateral distance between the drone and the distribution line. Based on the estimated lateral distance, it outputs a control signal to control the drone to move left and right, so that the drone is always within the set safe flight range.

[0010] Furthermore, the three electromagnetic sensors are arranged in an equilateral triangle array, and the geometric center of gravity of the equilateral triangle coincides with the center of mass of the drone. The formula for the lateral distance is: ,in, d ' is the lateral distance between the UAV and the distribution line, E m is the electric field strength measured by the first electromagnetic sensor, E n is the electric field strength measured by the third electromagnetic sensor, d is the distance between the first electromagnetic sensor and the third electromagnetic sensor.

[0011] Preferably, when the difference between the field strength measured by the first electromagnetic sensor and the field strength measured by the second electromagnetic sensor is within 5 V / m, the handpiece does not adjust its direction.

[0012] The beneficial effects of the invention are as follows: This technology uses the electromagnetic sensor array carried by the drone to collect electromagnetic signals from the distribution line, and estimates the relative position relationship between the drone and the distribution line based on the electromagnetic field distribution, so that the drone can autonomously navigate along the distribution line at a fixed safe distance, reducing GNSS dependence and realizing effective drone inspections in areas where GNSS signals are attenuated or interrupted. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is the electric field strength-distance measured curve and the inverse proportional fitting curve of the embodiment; Figure 2 This is a schematic diagram of the positional relationship between the drone and the power distribution line. DETAILED DESCRIPTION

[0014] The present invention proposes an autonomous inspection method for power distribution lines using a drone driven by electromagnetic characteristics. The specific steps are as follows: Step 1: The single-phase distribution line can be considered as having a length of l , a uniformly charged straight wire with a total charge of q. Assume that the linear charge density is l , the vacuum dielectric constant is The field strength in the direction parallel to the conductor and the field strength in the direction perpendicular to the conductor generated by the distribution line at a point P outside the conductor can be obtained: , , where m is the vertical distance from point P to the wire, i 1 and i 2 are the angles between point P and the two ends of the line.

[0015] Step 2: The relationship between the field strength E at point P is E x 2 + E y 2 = E2 Since the size of the electromagnetic sensor array itself is much smaller than the length of the distribution line, the distribution line can be approximately regarded as an infinitely long wire. i 1 is 0 and i 2 is π, and the field strength at point P is obtained .

[0016] If the linear charge density of a section of distribution line is equal, then the electric field strength at a point outside the conductor is only related to the distance from the electromagnetic sensor to the distribution line.

[0017] To ensure the drone's flight direction remains parallel to the power distribution lines during flight, two electromagnetic sensors can be installed on the front and rear sides of the drone's nose, with the connection line parallel to the drone's flight direction. When the electric field strengths measured by these two electromagnetic sensors are equal, the drone's current attitude is positively parallel to the power distribution lines. At this point, the drone simply maintains its current attitude and flies in the direction of its nose to achieve parallel tracking with the power distribution lines.

[0018] To ensure flight safety, it is also necessary to maintain the distance between the UAV and the power distribution line within a reasonable and safe range in real time. l It cannot be directly obtained, and a single electromagnetic sensor cannot uniquely determine the absolute distance between the drone and the line. However, since the electric field strength is inversely proportional to the distance, if two electromagnetic sensors are installed on the left and right sides of the drone body (left and right from the perspective of the drone's flight direction) and the connecting line is set perpendicular to the drone's flight direction, the difference in electric field strength measured by the two electromagnetic sensors and the known distance between them can be used to determine the absolute distance between the two electromagnetic sensors. d , calculate the lateral distance between the drone and the distribution line d '.

[0019] and , ,in, d 1. d 2 is the distance between the electromagnetic sensors on the left and right sides and the distribution line, E 1. E 2 is the electric field strength measured by the electromagnetic sensors on the left and right sides, d is the distance between the two electromagnetic sensors.

[0020] Therefore, the electromagnetic navigation solution to achieve attitude adjustment and distance control of the drone requires at least three electromagnetic sensors (the drone must have electromagnetic sensors in the front, back, left and right. Of the electromagnetic sensors arranged in the front and back, one can be used as an electromagnetic sensor on the left and right, and another electromagnetic sensor can be added. That is, three electromagnetic sensors can meet the requirements).

[0021] Step 3: When the electromagnetic sensor array is mounted on the rotor UAV, the three electromagnetic sensors are arranged in a triangle, preferably in an equilateral triangle arrangement. Figure 2 As shown, the first electromagnetic sensor 1 and the second electromagnetic sensor 2 are arranged along the flight direction of the UAV, and the connecting line is parallel to the direction of the nose, which is used to judge the relative posture of the UAV and the distribution line 4; the third electromagnetic sensor 3 is set on the other side of an equilateral triangle formed with the connecting line, which is used to estimate the lateral distance between the UAV and the distribution line 4.

[0022] To ensure the weight balance and attitude stability of the UAV during flight, the geometric center of gravity of the equilateral triangle array is designed to coincide with the center of mass of the UAV. d ' can be expressed as , E m is the electric field strength measured by the first electromagnetic sensor 1, E n is the electric field strength measured by the third electromagnetic sensor 3, d is the distance between the first electromagnetic sensor 1 and the third electromagnetic sensor 3; Step 4: In real-world applications, power distribution lines typically use a three-phase system. Due to the phase difference between the three-phase voltages, the direction and amplitude of the electric field in space vary with time, forming an electric field distribution with a rotating characteristic. When the drone is close to the distribution line, the field strength is no longer monotonically inversely proportional to distance due to the spatial superposition effect of the three-phase electric field. However, at greater distances, the influence of the phase difference and arrangement of the distribution lines on the electric field distribution gradually weakens. At this point, the complex structure of the three-phase conductors in space can be viewed as a linearly uniformly distributed charge system, and the field strength is approximately inversely proportional to distance.

[0023] The experiment was conducted using an unused 20kV three-phase distribution line, arranged horizontally at a height of 10m above the ground, with a 0.4m spacing between phases. The flight test platform was a quadrotor drone equipped with an inertial measurement unit, a GNSS module, a barometer, and a three-electromagnetic sensor array.

[0024] The drone's initial position is on the right side of the power distribution line. The barometer is used to set the flight altitude to 10m, and the GNSS module is used to set the array center to 2m away from the power distribution line. The drone moves away from the power distribution line at a constant speed of 0.5m / s in the vertical direction, records the electric field strength measured by the electromagnetic sensor, and plots the electric field strength-distance measured curve and the inverse proportional fitting curve, as shown in Figure 2. Figure 1 .

[0025] Use goodness of fit to evaluate the curve fitting effect: ,in,R is the goodness of fit value, y i is the measured data, For inverse proportional fitting data, is the average value, n is the number of test points. R 2 =0.994, indicating that when the UAV is far away from the three-phase distribution line, the relationship between the electric field strength and the distance in the UAV flight area is equivalent to an inversely proportional relationship, and the electric field strength distribution law in this area can be regarded as the same as that of the single-phase transmission line.

[0026] Step 5: This method can still be used to electromagnetically navigate the drone for three-phase power distribution lines. If the field strength measured by the forward electromagnetic sensor is greater than that measured by the rear, the drone's nose is rotated away from the power line; otherwise, it is rotated toward the power line until the difference between the two is less than a set threshold (ΔE < 5V / m). Simultaneously, the drone is controlled to move left and right based on the lateral distance estimated by the electromagnetic sensor array to ensure it remains within the set safe flight range. The flight altitude is determined by an onboard barometer and is set based on the height of the power distribution lines in the area.

[0027] The drone was initially positioned to the right of the power distribution line. A barometer was used to set the flight altitude to 10 meters, and the GNSS module was used to set the array center distance to 5 meters from the transmission line. The current lateral distance was inferred using data from the three electromagnetic sensor arrays. This was then compared with the set value to perform a left-right translation, allowing the drone to fly 60 meters along the line at a distance of 5 meters. The GNSS module was also used to calculate lateral deviations to assess control accuracy.

[0028] Table 1 Lateral deviation between drone and distribution line

[0029] Data analysis reveals relatively large lateral deviations during the initial flight phase (0–15 m), with an average deviation of 0.17 m and a maximum deviation of 0.25 m. The fluctuations are significant (standard deviation 0.083 m). This phenomenon is due to the fact that, immediately after takeoff, the drone is still near one end of the power distribution line. At this point, the electric field distribution of the three-phase power distribution line in space is significantly affected by the end-edge effect. The assumption in step 2 that the conductor is an infinitely long straight conductor no longer holds, leading to systematic errors when inferring lateral distance using electric field strength. Because the relationship between electric field and distance in the perception model is no longer a strictly monotonic function, the accuracy of the inference algorithm is limited in the early stages.

[0030] As the flight continues, as the drone gradually moves away from the edge of the distribution line, the distribution line can be better approximated as an infinitely long conductor within its sensing range, and the inverse relationship between electric field strength and lateral distance once again holds true. At this point, the lateral distance estimated by the electromagnetic array and the value measured by the GNSS module are significantly more consistent, allowing the control system to stably maintain the drone's flight at the set distance.

[0031] According to the above technology, an autonomous inspection system for UAVs driven by the electromagnetic characteristics of power distribution lines is proposed. The system contains three electromagnetic sensors arranged on a rotor-type UAV, wherein the first electromagnetic sensor 1 and the second electromagnetic sensor 2 are arranged along the flight direction of the UAV, and the connection line thereof is parallel to the direction of the nose. The third electromagnetic sensor 3 is arranged on one side of the connection line formed by the first electromagnetic sensor 1 and the second electromagnetic sensor 2. A signal collector is arranged on the UAV, and the signal collector is provided with a signal receiving port of the electromagnetic sensor. The UAV has a built-in processor, and the processor is connected to the signal collector. The processor is provided with an electromagnetic signal processing unit, and the electromagnetic signal processing unit processes the field strength signals of the three electromagnetic sensors. When the first electromagnetic sensor 1 is detected, the electromagnetic signal processing unit is detected. When the field strength measured by sensor 1 is greater than the field strength measured by the second electromagnetic sensor 2, the electromagnetic signal processing unit outputs a control signal after judgment to control the steering module of the drone to rotate the nose toward the side away from the distribution line 4. When the field strength measured by the first electromagnetic sensor 1 is less than the field strength measured by the second electromagnetic sensor 2, the electromagnetic signal processing unit outputs a control signal after judgment to control the steering module of the drone to rotate the nose toward the side close to the distribution line 4. The electromagnetic signal processing unit uses the field strength signal of the third electromagnetic sensor 3 to estimate the lateral distance between the drone and the distribution line. Based on the estimated lateral distance, the control signal is output to control the drone to move left and right, so that the drone is always within the set safe flight range.

Claims

1. A method for autonomous inspection of power distribution lines by drones based on electromagnetic characteristics, characterized in that an electromagnetic sensor array is mounted on a rotor-type drone, with three electromagnetic sensors arranged in a triangle, wherein: The first electromagnetic sensor (1) and the second electromagnetic sensor (2) are arranged along the flight direction of the UAV, with the connecting line thereof being parallel to the direction of the UAV's nose, and are used to judge the relative posture of the UAV and the power distribution line; the third electromagnetic sensor (3) is arranged on one side of the connecting line formed by the first electromagnetic sensor (1) and the second electromagnetic sensor (2), and is used to estimate the lateral distance between the UAV and the power distribution line; the flight altitude of the UAV is obtained by an onboard barometer, and the flight altitude of the UAV is set according to the height of the power distribution line in the area.

2. The autonomous inspection method of a UAV based on electromagnetic characteristics of distribution lines according to claim 1 is characterized by: The three electromagnetic sensors are arranged in an equilateral triangle array with connecting lines, and the geometric center of gravity of the equilateral triangle coincides with the center of mass of the drone.

3. The autonomous inspection method of a UAV based on electromagnetic characteristics of distribution lines according to claim 1 is characterized by: For a three-phase power distribution line, if the field strength measured by the first electromagnetic sensor (1) is greater than the field strength measured by the second electromagnetic sensor (2), the drone head is rotated toward the side away from the power distribution line (4); otherwise, the drone head is rotated toward the side close to the power distribution line (4). At the same time, the drone is controlled to move left and right based on the lateral distance estimated by the electromagnetic sensor array to ensure that it is always within the set safe flight range.

4. An autonomous inspection system of UAVs driven by electromagnetic characteristics of power distribution lines, characterized by The method for implementing any one of claims 1 to 3 comprises three electromagnetic sensors arranged on a rotary-wing UAV, wherein the first electromagnetic sensor (1) and the second electromagnetic sensor (2) are arranged along the flight direction of the UAV, and the connection line thereof is parallel to the direction of the nose of the UAV, and the third electromagnetic sensor (3) is arranged on one side of the connection line formed by the first electromagnetic sensor (1) and the second electromagnetic sensor (2), a signal collector is arranged on the UAV, and the signal collector is provided with a signal receiving port of the electromagnetic sensor, the UAV has a built-in processor, the processor is connected to the signal collector, and an electromagnetic signal processing unit is provided in the processor, and the electromagnetic signal processing unit processes the field strength signals of the three electromagnetic sensors, and when the field strength measured by the first electromagnetic sensor (1) is When the field strength measured by the first electromagnetic sensor (1) is greater than the field strength measured by the second electromagnetic sensor (2), the electromagnetic signal processing unit outputs a control signal after determining the difference, and controls the steering module of the drone to rotate the nose toward the side away from the power distribution line (4). When the field strength measured by the first electromagnetic sensor (1) is less than the field strength measured by the second electromagnetic sensor (2), the electromagnetic signal processing unit outputs a control signal after determining the difference, and controls the steering module of the drone to rotate the nose toward the side close to the power distribution line (4). The electromagnetic signal processing unit uses the field strength signal of the third electromagnetic sensor (3) to estimate the lateral distance between the drone and the power distribution line, and outputs a control signal based on the estimated lateral distance to control the drone to move in the left and right directions, so that the drone is always within the set safe flight range.

5. The autonomous inspection system of UAV based on electromagnetic characteristics of power distribution lines according to claim 4 is characterized by: The three electromagnetic sensors are arranged in an equilateral triangle array. The geometric center of gravity of the equilateral triangle coincides with the center of mass of the drone. The formula for the lateral distance is: ,in, d ' is the lateral distance between the UAV and the distribution line, E m is the electric field strength measured by the first electromagnetic sensor (1), E n is the electric field strength measured by the third electromagnetic sensor (3), d is the distance between the first electromagnetic sensor (1) and the third electromagnetic sensor (3).

6. The autonomous inspection system of UAV based on electromagnetic characteristics of power distribution lines according to claim 4 is characterized by: The difference between the field strength measured by the first electromagnetic sensor (1) and the field strength measured by the second electromagnetic sensor (2) is within 5V / m, and the direction of the machine head is not adjusted.

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