Hollow inspection system, hollow inspection method, and hollow inspection program

Abstract

By determining the precise location of multiple unmanned aerial vehicles (UAVs), it is possible to control these UAVs and acquire accurate three-dimensional data of the object being inspected. [Solution] The system comprises a plurality of first devices installed on and around the object to be inspected, capable of acquiring their own position information, and a plurality of second devices installed on unmanned aircraft for inspecting the object to be inspected, and includes distance calculation means for calculating the distance between each of the plurality of first devices 1 and the second device 2 based on the bidirectional transmission and reception times of information or signals between each of the plurality of first devices 1 and the second device 2, and position identification means for identifying the position of the second device 2 based on the distance between each of the plurality of first devices 1 and the second device 2 calculated by the distance calculation means, and the position information of each of the first devices 1.

Description

Technical Field

[0001] The present invention relates to a hollow inspection system, a hollow inspection method, and a hollow inspection program that can be used for inspecting an inspection target at a high place or an inaccessible place.

Background Art

[0002] Inspection work on inspection targets (such as bridges, wind power generation facilities, iron towers, chimneys, high-rise buildings, etc.) at high places or inaccessible places is highly risky in terms of safety and requires a lot of labor and time. Therefore, a method of using an unmanned aircraft (drone) to acquire three-dimensional data of an inspection target at a high place or an inaccessible place and perform inspections is effective (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in order to operate a plurality of unmanned aircraft to collect three-dimensional data, it is necessary to be able to control the plurality of unmanned aircraft without time and space errors. However, the position information by GPS always has an error of about several meters due to the time error of GPS satellites, the error of satellite orbit information, atmospheric delay, reflection from buildings and mountains, the clock error on the receiver side, etc. For this reason, it is difficult to accurately identify the position of each drone, and as a result, it is difficult to collect accurate three-dimensional data of the inspection target.

[0005] This invention has been made in view of the above circumstances, and its main objective is to provide a hollow inspection system, a hollow inspection method, and a hollow inspection program that can control multiple unmanned aerial vehicles to acquire accurate three-dimensional data of an object to be inspected by knowing the precise position of each of the multiple unmanned aerial vehicles. [Means for solving the problem]

[0006] To achieve the above objectives, the aerial inspection system according to the present invention is an aerial inspection system that uses a plurality of first devices installed on and around the object to be inspected and capable of acquiring its own positional information, and a plurality of second devices installed on unmanned aircraft for inspecting the object to be inspected, to perform aerial inspection of the object to be inspected, Distance calculation means for calculating the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A position identification means that identifies the position of the second device based on the distance between each of the first and second devices calculated by the distance calculation means, and the position information of each of the first devices. It is characterized by having [this feature].

[0007] Here, the first device from which its own location information can be obtained includes not only cases where the location information of the first device has been obtained and identified in advance, but also cases where it has been obtained and identified retrospectively by some means. Furthermore, the identified location information of the first device may be stored in a readable format in its own memory, or it may be stored in a database on another storage device. The position information of the first device is three-dimensional position information, and may be determined using either a geocentric Cartesian coordinate system or a geodetic coordinate system. Furthermore, the installation method of the first device is not particularly limited. It may be installed on the surface of the object to be inspected (bridges, wind power generation facilities, transmission towers, chimneys, high-rise buildings, etc.) or surrounding structures (fixed objects such as utility poles, transmission towers, road equipment, and buildings), or it may be embedded in the object to be inspected or surrounding structures.

[0008] Installing the second device on an unmanned aerial vehicle includes not only fixing it to the surface of the unmanned aerial vehicle, but also embedding it in the unmanned aerial vehicle, housing it in a compartment provided on the unmanned aerial vehicle, or fixing it to equipment that flies integrally with the unmanned aerial vehicle. Furthermore, the second device may be substituted for a control device mounted on an unmanned aerial vehicle by installing the application of this system on that control device.

[0009] Here, it is desirable to intentionally make the height positions on which the first device is installed different, and by managing the height position of the first device, it becomes possible to more accurately determine the three-dimensional position information of the second device.

[0010] Therefore, the distance calculation means calculates the distance between each of the multiple first devices and the second device installed on the unmanned aerial vehicle, and the position determination means makes it possible to determine the position of the second device, i.e., the position of each unmanned aerial vehicle, based on the distance between each of the multiple first devices and the second device, and the position information of the first devices.

[0011] Furthermore, in order to collect three-dimensional data of an object to be inspected by accumulating image data of the object from multiple directions taken by multiple unmanned aerial vehicles, it is necessary to synchronize the timestamps of the images taken by multiple unmanned aerial vehicles, assign the same timestamp, and then accumulate these images. Therefore, a time difference calculation means calculates the time difference between the clock of the first device and the clock of the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device. Based on the time difference calculated by this time difference calculation means, a device time synchronization means synchronizes the time of the second device with the time of the first device which is synchronized with the reference time, It is preferable to further include a three-dimensional data acquisition means for collecting three-dimensional data of the object to be inspected based on data captured by the time-synchronized imaging devices of the multiple unmanned aircraft. This makes it possible to collect accurate three-dimensional data of the object being inspected using multiple unmanned aerial vehicles, enabling more precise inspections of the object.

[0012] Here, the distance calculation means is: The difference between the time on the first device's clock when it transmits information or a signal and the time on the second device's clock when it receives the information or signal transmitted from the first device, The difference between the time on the second device's clock when it transmits information or a signal and the time on the first device's clock when it receives the information or signal transmitted from the second device, The propagation time of the information or signal between the first device and the second device may be calculated based on this propagation time, and the distance between the first device and the second device may be calculated based on this propagation time. In this configuration, the distance between the first and second devices can be accurately calculated even if time synchronization is not maintained between the first and second devices, by calculating the distance between the first and second devices based on the transmission and reception times of information or signals in both directions between the first and second devices.

[0013] Furthermore, the device time synchronization means is The difference between the time on the first device's clock when it transmits information or a signal and the time on the second device's clock when it receives the information or signal transmitted from the first device, The difference between the time on the second device's clock when it transmits information or a signal and the time on the first device's clock when it receives the information or signal transmitted from the second device, Based on this, it is preferable to calculate the time difference between the clock of the first device 1 and the clock of the second device 2, and then synchronize the time of the clock of the second device with the time of the clock of the first device based on this time difference. By using such a synchronization method, even when time synchronization using GPS or the Internet is not possible, it becomes possible to synchronize the clock of the second device with the clock of the first device. As a result, accurate three-dimensional data collection by a plurality of unmanned aerial vehicles is ensured.

Advantages of the Invention

[0014] As described above, according to the hollow inspection system, the hollow inspection method, and the hollow inspection program according to the present invention, based on the transmission and reception times of information or signals in both directions between each of a plurality of first devices and a second device, the distance between each of the plurality of first devices and the second device is calculated. From the calculated distances between each of the plurality of first devices and the second device and the position information of each first device, the positions of the unmanned aerial vehicles on which the second device is installed are specified. Therefore, it becomes possible to accurately grasp and control the positions of a plurality of unmanned aerial vehicles, and it becomes possible to collect accurate three-dimensional data of the inspection target.

Brief Description of the Drawings

[0015] [Figure 1] It is a diagram showing an installation example of the first device and the second device of the hollow inspection system according to the present invention, showing an example in which the second device is installed on a plurality of unmanned aerial vehicles (drones). (a) shows an example in which the first device is installed on a steel tower and fixed objects around it, (b) shows an example in which the first device is installed on a wind power generation facility and fixed objects around it, (c) shows an example in which the first device is installed on a bridge and fixed objects around it, and (d) shows an example in which the first device is installed on a high-rise building and fixed objects around it. [Figure 2] It is a diagram showing a configuration example of the hollow inspection system according to the present invention. [Figure 3] It is a block diagram showing a configuration example of the first device. [Figure 4] It is a block diagram showing a configuration example of the second device. [Figure 5] It is a block diagram showing the configuration of the server device. [Figure 6] It is a flowchart showing the distance calculation process. [Figure 7]It is a flowchart showing position-specific processing. [Figure 8] It is a flowchart showing an example of a process of collecting three-dimensional data of an inspection target using a plurality of unmanned aerial vehicles.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.

[0017] In FIG. 1, examples of inspection targets for performing aerial inspection are shown, such as inspection targets located at high places or hard-to-access locations. This aerial inspection system S photographs inspection targets at high places or hard-to-access locations with a photographing device mounted on a plurality of unmanned aerial vehicles (drones), collects accurate three-dimensional data of the inspected locations based on the photographed data, and inspects the presence or absence of abnormalities in the inspected locations by analyzing the data. The example shown in FIG. 1(a) is an example in which the upper part of a transmission tower X1 on which transmission lines are installed is taken as an inspection target. At a high place of the transmission tower X1, in order to inspect the presence or absence of damage or deterioration of equipment, that part is photographed by a photographing device mounted on a plurality of unmanned aerial vehicles (drones) D, and inspected based on the photographed data. The example shown in FIG. 1(b) is an example in which the blades, hub, nacelle, etc. at the upper part of a wind power generation facility X2 are taken as inspection targets. In order to inspect those parts, that part is photographed by a photographing device mounted on a plurality of unmanned aerial vehicles D, and the presence or absence of damage is inspected based on the photographed data. The example shown in FIG. 1(c) is an example in which the girders, cables (diagonal members), bridge towers, obstacle devices, lighting equipment, etc. of a bridge X3 are taken as inspection targets. In order to inspect those parts, that part is photographed by a photographing device mounted on a plurality of unmanned aerial vehicles D, and inspected based on the photographed data. The example shown in FIG. 1(d) is an example in which a high-rise building is taken as an inspection target. In order to inspect damage, cracks, deterioration, etc. on the surface of the building, the inspection target location is photographed with a photographing device mounted on a plurality of unmanned aerial vehicles, and the presence or absence of damage is inspected based on the photographed data.

[0018] In these examples, the hollow inspection system S, as shown in Figure 2, comprises a first device 1 installed at intervals around or near the inspection site, a second device 2 installed on an unmanned aerial vehicle (drone) D, and a server device 3. The first device 1 is installed at any mounting location that is at a height suitable for transmitting and receiving radio waves. In the case of transmission tower X1, the lights are installed at intervals on the tower itself, as well as on nearby fixed structures such as control panels, transformers, surveillance cameras, fences, utility poles, streetlights, roadside equipment, signs, substations, management buildings, and dedicated mounting poles. In the example of wind power generation facility X2, the sensors are installed at intervals on the support structures and nacelles where the wind turbines are mounted, as well as on fixed structures in the surrounding area such as substations, control buildings, transformers, surveillance cameras and sensors, utility poles, streetlights, road equipment, signs, and dedicated mounting poles. In the example of bridge X3, the sensors are installed at intervals on bridge piers, guardrails and protective fences, as well as on fixed structures such as lighting equipment, surveillance cameras and sensors, road signs and information boards, and management offices. In the example of high-rise building X4, the lights are installed at intervals on the building's rooftop and exterior walls, as well as on fixed structures in the surrounding area such as parking facilities, utility poles, streetlights, signs and information boards, and nearby buildings.

[0019] This first device 1 may be fixed to the surface of these fixed objects by appropriate means such as screws, adhesives, or brackets, or it may be installed by being housed (embedded) inside the fixed objects. Furthermore, each of the first devices 1 has its own three-dimensional position information acquired by some means.

[0020] The three-dimensional position information of the first device 1 may be acquired in advance and stored in a readable format inside the first device, or it may be acquired retrospectively by some means after the system has been started. Furthermore, the three-dimensional position information of the first device 1 may be compiled into a database and stored in the storage unit (storage unit 33, described later) of the server device 3. Here, the three-dimensional position information may be represented, for example, by latitude, longitude, and ellipsoidal height in the WGS84 coordinate system, or by a unique three-dimensional coordinate system set up for each area indoors.

[0021] The first device 1 and the second device 2 can communicate directly with each other. Furthermore, the first device 1 can be connected to the server device 3 via the communication network 4, and the second device 2 can also be connected to the server device 3 via the communication network 4.

[0022] Each of the first device 1 and second device 2 has a built-in clock, which can be synchronized to a reference time using a method described later. By synchronizing them, it is possible to obtain accurate positional information of multiple second devices at the same time.

[0023] Furthermore, the first device 1 can also function as the first device 1 for multiple second devices 2, and when multiple second devices 2 exist, each of these second devices 2 may be configured to function as the first device for multiple other second devices. In other words, if the precise location of a second device can be determined, the distance between that second device and other second devices can be calculated and used to determine the location of the other second devices. In this embodiment, we will describe a case where only the first device is used to locate the second device.

[0024] (Regarding the first device) As shown in Figure 3, the first device 1 comprises a control unit 11, an RF chip 12, and an oscillator 13, each connected by a bus. It also includes a RAM 14 and a storage unit 15, each connected to the control unit 11 by a bus.

[0025] The control unit 11 consists of a CPU and ROM, and executes programs stored in ROM to control the first device 1. The RF chip 12 is equipped with at least a clock 16, but may also be equipped with a phase detector. The RF chip 12 also has the function of processing the transmission and reception of wireless signals, and the data received by the RF chip 12 is subject to calculation processing by the control unit 11. The RAM 14 is the work area of ​​the control unit 11, and the storage unit 15 is a storage area for saving programs, data, etc.

[0026] The oscillator 13 oscillates at a predetermined frequency and outputs a signal to provide the operating timing for each part of the device. A crystal oscillator or an atomic oscillator can be used as the oscillator 13. The clock 16 keeps time using the output signal of the oscillator 13 as the source oscillation and outputs the time. The time kept by the clock 16 is controlled by the control unit 11 to be transmitted to the second device 2 via the RF chip 12. If a phase detector is also provided, it detects the phase of the carrier wave that constitutes the information received from the second device 2, and also detects the phase of the signal transmitted by the oscillator 13 of the first device 1.

[0027] The RF chip 12 is capable of sending and receiving data with other computer devices. Data received by the RF chip 12 is stored in the RAM 14 or storage unit 15 and is subject to calculation processing by the control unit 11. When the 3D position information of the first device 1 is received via the RF chip 12, it is stored in the RAM 14 or storage unit 15 and controlled by the control unit 11 to be transmitted to the second device 2 via the RF chip 12.

[0028] In this hollow inspection system S, the installation location of the first device 1 is not particularly limited, but since it is used to determine the current position of unmanned aerial vehicles D flying over high places or difficult-to-access locations, it is preferable to install it in the aforementioned location that has good visibility from as many unmanned aerial vehicles as possible, and the location should be appropriately selected according to the infrastructure conditions of the place where the hollow inspection system S is used.

[0029] To obtain three-dimensional positional information of the unmanned aerial vehicle D, the first device 1 does not need to be installed on the same plane; rather, it is preferable that adjacent first devices 1 be installed at different heights. For example, even when the first device 1 is attached to a nearby fixed object, it is preferable to make the mounting height of the first device different for each fixed object. Furthermore, it is desirable that the first device 1 be installed comprehensively around the inspection site and its surroundings.

[0030] Furthermore, the location information of the installation site of the first device 1 may be stored in its own storage unit 15, associated with identification information that can identify the first device 1, or stored in the storage unit 33 of the server device 3, or it may be made available via the communication network 4 from another management server that manages location information.

[0031] (Regarding the second device) Next, the second device 2 will be described. This second device 2 is to be installed on all unmanned aerial vehicles (drones) D that are to be flown. It may be attached directly to the aircraft body D, or embedded inside the aircraft body. If the aircraft body is provided with a storage compartment, it may be stored in that compartment. Furthermore, it may be fixed to cameras, sensors, GPS modules, communication equipment, material handling devices, etc. that fly integrally with the aircraft body (attached to the aircraft body). Alternatively, the application of this system may be installed on the flight controller of the unmanned aerial vehicle, and the flight controller may be used as a substitute.

[0032] As shown in Figure 4, the second device 2 comprises a control unit 21, an RF chip 22, and an oscillator 23, each connected by a bus. It also includes a RAM 24 and a storage unit 25, each connected to the control unit 21 by a bus.

[0033] The RF chip 22 includes at least a clock 26, but may also include a phase detector if necessary.

[0034] The control unit 21 is configured with a CPU and ROM, and executes programs stored in the storage unit 25 to control the second device 2. The RAM 24 is the work area of ​​the control unit 21, and the storage unit 25 is a storage area for saving programs and data. The control unit 21 performs calculation processing based on programs and data read from the RAM 24 and the storage unit 25, as well as data input from an input unit (not shown).

[0035] The RF chip 22 is capable of sending and receiving data with other computer devices. The data received by the RF chip 22 is loaded into the RAM 24 and subjected to calculation processing by the control unit 21.

[0036] The oscillator 23 oscillates at a predetermined frequency and outputs a signal to provide the operating timing for each part of the device. A crystal oscillator or an atomic oscillator can be used as the oscillator 23. The clock 26 keeps time using the output signal of the oscillator 23 as the source oscillation and outputs the time. The time kept by the clock is controlled by the control unit 21 to be transmitted to the first device 1 via the RF chip 22. If a phase detector is also present, it detects the phase of the carrier wave that constitutes the information received from the first device 1, and also detects the phase of the signal oscillated by the oscillator 23 of the second device 2.

[0037] (Regarding server equipment) Next, the server device 3 of the present invention will be described. The server device 3 can acquire location information from the second device 2.

[0038] The acquired location information is stored in server device 3 as the location information of the unmanned aerial vehicle (second device 2). The location information of the unmanned aerial vehicle (second device 2) is transmitted from second device 2 to server device 3, for example, by associating identification information that can identify second device 2 with the time the location information was determined. Server device 3 may also enable communication between first device 1 and second device 2 via smart meters installed in houses or electrical equipment.

[0039] Figure 5 is a block diagram showing the configuration of a server device 3 according to an embodiment of the present invention. The server device 3 comprises at least a control unit 31, a RAM 32, a storage unit 33, and a communication interface 34, each connected by an internal bus. It also includes a database 35 for storing information received from the first device 1 and the second device 2. The location information of the first device 1 may also be stored in this database 35 after being compiled into the database.

[0040] The control unit 31 consists of a CPU, ROM, etc., and executes programs stored in the storage unit 33 to control the server device 3. The control unit 31 also has an internal timer for measuring time. The RAM 32 is the work area of ​​the control unit 31. The storage unit 33 is a storage area for saving programs and data. The control unit 31 reads programs and data from the storage unit 33 and RAM 32, and, based on information received from the first device 1 or the second device 2, executes various control processes in the control unit according to the program.

[0041] (Distance calculation process) Using the above configuration, the process for calculating the distance between the first device 1 and the second device 2 will now be described.

[0042] This distance calculation process calculates the distance between each of the first devices 1 and the second device 2, based on the propagation time Tp of the information or signal between each of the first devices 1 and the second device 2, provided that the first devices 1 and the second device 2 are within a distance range that allows them to mutually send and receive information or signals.

[0043] The distance calculation process is performed at predetermined time intervals (for example, every minute) or whenever predetermined conditions are met, and the process is carried out in steps S1 to S16 as shown in Figure 6. For convenience, here we will explain the case of calculating the distance between one first device 1 and one second device 2.

[0044] First, information or a signal is transmitted from the first device 1 to the second device 2 (step S1). The information or signal transmitted from the first device 1 to the second device 2 is not particularly limited.

[0045] In the first device 1, the time (T11) when information or a signal is transmitted in step S1 is recorded (step S2), and this recorded time is stored in the memory or storage unit 15 within the control unit 11 (step S3).

[0046] Subsequently, the second device 2 receives the information or signal from the first device 1 (step S4). The second device 2 records the time (T21) when the information or signal was received in step S4 (step S5). The recorded time (including the measured phase, if one is measured) is then stored in the memory or storage unit 25 of the control unit 21 (step S6).

[0047] Next, the second device 2 transmits information or a signal to the first device 1 (step S7). The information or signal transmitted from the second device 2 to the first device 1 is not particularly limited. The second device 2 records the time (T22) when the information or signal was transmitted in step S7 (step S8). Then, the recorded time is stored in the memory or storage unit 25 of the control unit 21 (step S9).

[0048] The first device 1 receives the information or signal transmitted in step S7 (step S10). The first device 1 records the time (T12) when it received the information or signal in step S10 (step S11). The recorded time (including the measured phase if the phase is measured) is then stored in the memory or storage unit 15 of the control unit 11 (step S12).

[0049] Subsequently, the first device 1 transmits to the second device 2 via its RF chip 12 the information stored in step S3 regarding the time (T11) when the signal was transmitted in step S1, and the information stored in step S12 regarding the time (T12) when the signal was received in step S10 (step S13). At this time, the position information of the first device 1 is also transmitted to the second device 2.

[0050] Then, in step S1, the second device 2 receives information regarding the time (T11) when the first device 1 transmitted information or a signal, and information regarding the time (T12) when the first device received information or a signal in step S10 (step S14).

[0051] Next, the second device 2 calculates the distance between the first device 1 and the second device 2 (step S15). This distance is calculated in the following manner.

[0052] Information regarding the time of the first device's clock (T11) is transmitted to the second device 2 via radio waves. The difference between this time and the time of the second device 2's clock (T21) when the second device 2 receives this information is recorded as ΔTa on the second device 2 side. In other words, if we define the time of the first device's clock when it transmits information or a signal from the first device 1 to the second device 2 as T11, and the time of the second device's clock when it receives the information or signal transmitted from the first device 1 and sets time as T21, and the difference between them as ΔTa, then this ΔTa (the difference in transmission and reception times when information or a signal is transmitted from the first device 1 to the second device 2) is the difference between the time of the first device 1's clock and the second device 2's clock (time difference: T20-T10) plus the propagation time (propagation delay) Tp, resulting in the relationship shown in Equation 1. This time difference (T20-T10) would be zero if the clocks of the first device 1 and the second device 2 were synchronized, but here we assume that a time difference (T20-T10) exists (they are not synchronized). [Formula 1] ΔTa=T21-T11=(T20-T10)+Tp

[0053] To determine this propagation time Tp, the second device 2 also sends information about the time of this clock (T22) to the first device 1, and the difference between this time and the time of the first device 1's clock (T12) when the first device 1 receives it is recorded as ΔTb on the first device side. That is, if we define the time of the second device's clock when the second device 2 transmits information or a signal to the first device 1 as T22, and the time of the first device 1's clock when it receives the information or signal transmitted from the second device 2 as T12, and the difference between them as ΔTb, then this ΔTb (the difference in transmission and reception times when the second device 2 transmits information or a signal to the first device 1) is the difference between the time of the first device 1's clock and the second device 2's clock (time difference: T10-T20) plus the propagation time (propagation delay) Tp, resulting in the relationship shown in Equation 2. Here, the time difference (T10-T20) would be zero if the clocks of the first device 1 and the second device 2 were synchronized, but here we assume that a time difference (T10-T20) exists (they are not synchronized). [Formula 2] ΔTb=T12−T22=(T10−T20)+Tp

[0054] The time differences between the two clocks, (T20-T10) and (T10-T20), are added when transmitting from the first device to the second device, and the same amount of time difference is subtracted when transmitting from the second device to the first device. Therefore, to find the propagation time Tp, we add equations 1 and 2, which cancels out the terms for the time differences (T20-T10) and (T10-T20), resulting in the relationship in equation 3. [Formula 3] Tp=(ΔTa+ΔTb) / 2 =((T21-T11)+(T12-T22)) / 2

[0055] Therefore, the propagation time Tp can be calculated based only on the time read by the clock of the first device 1 and the time read by the clock of the second device 2.

[0056] Incidentally, the time difference (T10-T20) between the clock of the first device 1 and the clock of the second device 2 is given by the relationship in Equation 4, obtained by [Equation 1] - [Equation 2]. [Formula 4] (T10-T20)=(ΔTa−ΔTb) / 2

[0057] Subsequently, the distance between the first device 1 and the second device 2 is calculated by multiplying the propagation time calculated using Equation 3 by the propagation speed of the information or signal (e.g., high speed) (step S15).

[0058] Then, the distance between the first device 1 and the second device 2 calculated in step S15 is stored in the memory or storage unit 25 of the control unit 21 and transmitted to the server device 3 (step S16). By executing step S16, the distance calculation process is completed.

[0059] Therefore, since equation (3) for calculating the propagation time Tp does not include a term for the time difference (time difference: T20-T10) between the clocks of the first device 1 and the second device 2, the propagation time for information or signals to propagate between the first device 1 and the second device 2 can be calculated regardless of whether there is a time difference between the clocks of the first device 1 and the second device 2 (independent of the time difference (time difference: T10-T20) between the clocks of the first device 1 and the second device 2).

[0060] [Location identification process] Next, we will explain the process of determining the position of the person to whom the second device 2 is attached. This position determination process determines the position of the second device 2 based on the distances between each of the multiple first devices 1 and the second device 2, which were calculated in the distance calculation process. Since the second device 2 is installed on an unmanned aerial vehicle, this can be said to be a process of determining the position of the unmanned aerial vehicle.

[0061] This positioning process should preferably be performed immediately after the distance calculation process is completed. Furthermore, in order to determine the position of the second device 2, it is assumed that the distance calculation device has calculated the distance to each of the multiple first devices 1 for each of the second devices 2.

[0062] In other words, when obtaining three-dimensional positional information of an unmanned aerial vehicle (to obtain x, y, and z coordinates), the position of the second device 2 can be determined by using a well-known multi-point surveying calculation method, based on the distance between one second device 2 and at least four first devices 1, and the positional information of each of the four first devices 1 used to calculate this distance. Therefore, this system can determine the three-dimensional position of the second device 2 if four or more distance data points are available between the first device 1 and the second device 2. Thus, even if the second device 2 (unmanned aerial vehicle D) moves, it is advisable to appropriately distribute the first devices 1 so that the second device 2 can send and receive information or signals with at least four first devices 1. In particular, in locations where positional accuracy is required, it is necessary to pre-adjust the number and three-dimensional position of the first device 1 to achieve the required accuracy.

[0063] Figure 7 shows a flowchart of the location identification process according to an embodiment of the present invention. This location identification process can be performed on either the first device 1, the second device 2, or the server device 3. When the location identification process is performed on the first device 1 or the server device 3, the distance between each of the multiple first devices 1 and the second device 2, as well as the location information of the first device 1, can be associated with the identification information of the second device 2, transmitted to the first device 1 or the server device 3, and used. Here, an example of performing the location identification process on the server device will be described.

[0064] First, the position determination process requires that distance information for at least four different first devices 1 and second devices 2 be obtained at the same time or close together. Here, "close together" means that the time at which the distances between the four first devices 1 and second devices 2 used to determine the position of second device 2 are calculated is within a range that does not hinder the capture of the movement of the second device. If the distances are not calculated at the same time or close together (for example, if the time at which the propagation time of information or signals between each of the multiple first devices 1 and second device 2 is measured is the same time or close together), it becomes difficult to accurately determine the position of second device 2 (unmanned aerial vehicle) assuming that it is moving.

[0065] Therefore, first, it is determined whether four or more data points of the distance between the first device 1 and the second device 2 have been acquired within a predetermined time range (step S21).

[0066] If four or more distance data points between the first device 1 and the second device 2 are not acquired within a predetermined time range, accurate three-dimensional positional information cannot be obtained using this positioning method. Therefore, the system waits until four or more distance data points are obtained within the predetermined time range. In contrast, if four or more distance data points between the first device 1 and the second device 2 can be acquired within a predetermined time range, accurate three-dimensional position information can be obtained using this position determination method utilizing wireless bidirectional time comparison. Then, the current position of the second device 2 is determined using the multi-point surveying calculation method described above (step S22), and display processing is performed such as displaying the current position of the unmanned aerial vehicle (second device 2) on a display screen (not shown) of the server device 3 (step 23). At the same time, it is preferable to store the position information of the second device 2 along with the time it was calculated in the storage unit 33 of the server device 3 for use in subsequent processing.

[0067] Therefore, if there are four or more first devices 1 that can transmit and receive signals from the second device 2 installed on the unmanned aerial vehicle within a predetermined time range, the three-dimensional position of the second device 2 is determined by a position determination process based on the distance between each first device 1 and the second device 2 calculated by the distance calculation process, and the position information of each first device 1 used in this distance calculation. As the unmanned aerial vehicle D moves, the four first devices 1 from which distance calculation is possible are switched sequentially, making it possible to continuously track the position of the second device 2. Thus, if there are four or more first devices 1 capable of calculating distance, it becomes possible to determine the three-dimensional position of the second device 2. By adjusting the objects to which the first devices are attached and their mounting heights to ensure they are appropriately scattered, it becomes possible to track the position of the displaced second device (unmanned aerial vehicle D) in real time.

[0068] By performing the above processing on all flying unmanned aircraft D (unmanned aircraft equipped with the second device 2), accurate three-dimensional positional information of the unmanned aircraft flying around the object under inspection can be obtained. By controlling the flight of each unmanned aircraft D based on this positional information, it becomes possible to accurately inspect (collect data from) the desired areas without making mistakes, even for objects under inspection that are at high altitudes or difficult to access.

[0069] Conventional distance measurement systems calculate propagation time based on the difference between the transmission time of a transmitter (corresponding to the first device) and the reception time of a receiver (corresponding to the second device), and then calculate distance based on this time. However, in this method, unless the transmitter and receiver are time-synchronized, if there is a time difference between the two devices, the calculated propagation time will differ from the actual propagation time. In other words, if the receiver is different, the calculated propagation time may differ. In contrast, this system calculates the propagation time based on the transmission and reception times in both directions between the first device 1 and the second device 2, and then calculates the distance between the first device 1 and the second device 2. Therefore, even if there is a time difference between the first device 1 and the second device 2, there is no inconvenience in that the calculated propagation time will differ.

[0070] Furthermore, if the second device 2 installed on the unmanned aerial vehicle is not time-synchronized, the position information of each unmanned aerial vehicle at a certain time recorded on the server will become inaccurate (a discrepancy will occur between the position known on the server at a certain time and the actual position at that time). When attempting to collect three-dimensional data of the inspection area using multiple unmanned aerial vehicles, the data recorded with the same timestamp will be collected from different locations by each unmanned aerial vehicle, making it impossible to collect accurate three-dimensional data of the inspection area. For this reason, in order to collect accurate three-dimensional data, all first devices 1 and second devices 2 must be time-synchronized with the server device 3.

[0071] Therefore, by synchronizing the time of the second device 2 with the time of the first device based on the time difference in equation (4), and synchronizing multiple first devices together with the server device 3 at a predetermined timing, it becomes possible to synchronize the time of all second devices 2 with the first device 1 and the server device 3. As a result, it becomes possible to accurately collect simultaneous photographic information of all flying unmanned aircraft D, making it possible to collect accurate three-dimensional data of the inspection area and to accurately inspect the object being inspected.

[0072] (Examples of using this system) To collect three-dimensional data of the object being inspected using the hollow inspection system S described above, the processing shown in Figure 8 is possible. First, the position of each unmanned aircraft (second device 2) is calculated using the method described above, and the position of each unmanned aircraft is determined (step S31). Subsequently, the system refers to the inspection target database 40, which stores the three-dimensional location information and target items of each inspection target in association with each other, and sets the inspection target to be inspected (step S32).

[0073] Then, it is determined whether the flying unmanned aircraft D are distributed around the designated object to be inspected in a position where they can collect three-dimensional data of the object to be inspected (step S33). This determination is made based on criteria such as whether the objects being inspected are spatially distributed without bias at a distance suitable for collecting three-dimensional data of the object being inspected, by referring to the distance to the object, the spacing and positional relationship with nearby unmanned aerial vehicles, etc.

[0074] Then, if it is determined that the multiple unmanned aircraft D are not distributed in positions where three-dimensional data of the object under inspection can be collected, a command is issued to each unmanned aircraft D to distribute their flight positions to positions suitable for collecting three-dimensional data of the object under inspection (step S34). As a result, when each unmanned aerial vehicle is dispersed and positioned in a location suitable for collecting three-dimensional data of the object under inspection, the imaging is started, and the imaging data is read from each unmanned aerial vehicle to collect three-dimensional data of the object under inspection (step S35).

[0075] Therefore, with the above system, the precise positional information of the unmanned aircraft D flying around the object under inspection is captured in real time, and each unmanned aircraft is distributed and positioned in a location suitable for collecting three-dimensional data of the object under inspection, so that the inspection area is photographed, thereby enabling the collection of accurate three-dimensional data. [Explanation of symbols]

[0076] 1 1st device 2 Second device 3 Server equipment S Hollow Inspection System D Unmanned aerial vehicle

Claims

1. Using a plurality of first devices installed on and around the object to be inspected, capable of acquiring their own position information, and a second device installed on a plurality of unmanned aircraft for inspecting the object to be inspected, An aerial inspection system for performing aerial inspection of the object to be inspected, Distance calculation means for calculating the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A position determination means that determines the position of the second device based on the distance between each of the first and second devices calculated by the distance calculation means, and the position information of each of the first devices, A hollow inspection system characterized by having the following features.

2. A time difference calculation means calculates the time difference between the clock of the first device and the clock of the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, Based on the aforementioned time difference, the device time synchronization means synchronizes the time of the second device with the time of the first device which is synchronized with the reference time, The system further comprises a three-dimensional data acquisition means for collecting three-dimensional data of the object to be inspected based on data captured by the time-synchronized imaging devices of the plurality of unmanned aerial vehicles. The hollow inspection system according to claim 1.

3. The distance calculation means is The difference between the time on the first device's clock when it transmits information or a signal and the time on the second device's clock when it receives the information or signal transmitted from the first device, The difference between the time on the second device's clock when it transmits information or a signal and the time on the first device's clock when it receives the information or signal transmitted from the second device, The hollow inspection system according to claim 1, characterized in that it calculates the propagation time of the information or signal between the first device and the second device based on this propagation time, and calculates the distance between the first device and the second device based on this propagation time.

4. The aforementioned device time synchronization means is The difference between the time on the first device's clock when it transmits information or a signal and the time on the second device's clock when it receives the information or signal transmitted from the first device, The difference between the time on the second device's clock when it transmits information or a signal and the time on the first device's clock when it receives the information or signal transmitted from the second device, The hollow inspection system according to claim 2, characterized in that, based on this, the time difference between the clock of the first device 1 and the clock of the second device 2 is calculated, and the time of the clock of the second device is synchronized with the time of the clock of the first device based on this time difference.

5. Using a plurality of first devices installed on and around the object to be inspected, capable of acquiring their own position information, and a second device installed on a plurality of unmanned aircraft for inspecting the object to be inspected, An aerial inspection method for inspecting the object to be inspected, A distance calculation step that calculates the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A position determination step in which the position of the second device is determined based on the distance between each of the first and second devices calculated in the distance calculation step, and the position information of each of the first devices, A hollow inspection method characterized by having the following features.

6. A time difference calculation step that calculates the time difference between the clock of the first device and the clock of the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A device time synchronization step is performed to synchronize the time of the second device with the time of the first device which is synchronized to a reference time, based on the aforementioned time difference. The system further comprises a three-dimensional data acquisition step of collecting three-dimensional data of the object to be inspected based on data captured by the time-synchronized imaging devices of the multiple unmanned aerial vehicles. The hollow inspection method according to claim 5, characterized by its features.

7. A hollow inspection program for causing a computer to perform each step of the hollow inspection method according to claim 5 or 6.

Images