Cable laying method

Abstract

The purpose of the present disclosure is to provide a cable laying method capable of applying, using a plurality of drones, a horizontal tension capable of securing a sufficient ground height to a cable while stably flying each drone.　The cable laying method according to the present disclosure is for laying a cable 300 between utility poles 200 by using a plurality of drones 100. The method includes: causing each drone 100 to grip the cable 300; and causing each drone 100 to apply horizontal tension to the cable 300 so that the cable 300 secures a predetermined ground height while each drone 100 satisfies a predetermined pitch angle.

Description

Cable laying method

[0001] The present disclosure relates to a cable laying method using a drone.

[0002] Conventionally, when a cable is laid alone above an overhead structure such as a utility pole, the cable is manually laid on the ground along the route from the start point to the end point, and then tensioned at the installation point on the overhead structure. This method can be dangerous when the ground is on a busy road or when the overhead structure is located in a mountain valley with a difference in elevation. In particular, when working on a road, the cable being laid poses a danger to vehicles and people passing by.

[0003] A commonly known method to avoid this is to lay cables overhead between the spans of an aerial structure using rocket launchers or drones. However, due to the limitations of the drone's payload capacity, this requires a round-trip operation to replace cables with higher linear mass densities (for example, from a tow cord to a tow rope to a cable) with lower linear mass densities.

[0004] For example, Non-Patent Document 1 discloses a method of using a general winch to lay a lightweight rope, a towing rope, and a cable in that order. When using this method, the span length that can be laid is limited by the pulling tension of the machine that tensions the cable. In other words, when laying a cable using a single drone, the span length that can be laid is limited by the weight of the cable, etc.

[0005] NTT Technical Journal, July 2014, pp. 55-58

[0006] On the other hand, while it is possible to use multiple drones to lay cables, it was unclear what conditions each drone needed to meet in order to ensure stable flight while applying horizontal tension to the cable to ensure sufficient ground clearance.

[0007] Therefore, the present disclosure aims to provide a cable laying method that uses multiple drones to apply horizontal tension to the cable that ensures sufficient ground clearance while allowing each drone to fly stably.

[0008] To achieve the above objective, the cable laying method of the present disclosure employs a technique in which multiple drones are used, with each drone applying horizontal tension to the cable so that the cable maintains a predetermined height above ground while satisfying a predetermined pitch angle.

[0009] Specifically, the cable laying method is a cable laying method for laying a cable between aerial structures using a plurality of drones, and includes: having each of the drones hold the cable; and each of the drones applying horizontal tension to the cable so that the cable maintains a predetermined height above ground while satisfying a predetermined pitch angle.

[0010] This allows the drone to fly stably while ensuring ground clearance during and after laying, allowing long-span cable to be laid without having to travel back and forth between spans.

[0011] The cable laying method may also include having each drone hold the cable at a predetermined interval, and each drone applying the horizontal tension to the cable so that slack between adjacent drones is constant between each drone.

[0012] The cable laying method may also include applying a vertical load to each of the drones.

[0013] The cable laying method may also include: having each drone hold the cable at a suspension position of the aerial structure located at a starting point; flying each drone horizontally from the suspension position of the aerial structure located at the starting point toward the suspension position of the aerial structure located at an end point; applying the horizontal tension to the cable until each drone stops at a predetermined position; having each drone hold the cable at the suspension position of the aerial structure located at the end point after stopping at the predetermined position; and having each drone release the cable after holding the cable at the suspension position of the aerial structure located at the end point.

[0014] The above disclosures can be combined as much as possible.

[0015] According to the cable laying method of the present disclosure, multiple drones can be used to apply horizontal tension to the cable that ensures sufficient ground clearance while allowing each drone to fly stably.

[0016] 1 is a diagram explaining the pulling force and buoyancy at a pitch angle of 30 degrees when the drone's payload limit is 200 N. This diagram explains the forces applied when laying a cable using a drone, and the relationship between the laying height, sag, and ground clearance. This diagram explains that the cable forms a catenary curve during and after laying. This diagram explains the pitch angle, sag, or span length under specified conditions. This diagram explains the relationship between the sag and span length of each span during towing and the sag and span length at completion of laying when N drones are towing the cable. This diagram explains cable towing by a first drone and a second drone. This is a table explaining the number of drones, the spacing between drones, etc. when multiple drones are used to tow a cable while maintaining constant sag. This diagram explains the relationship between the sag and span length of each span during towing and the sag and span length at completion of laying. This diagram explains cable towing by a first drone and a second drone when adjustment is made using weights. This is a table explaining the number of drones, the spacing between drones, etc. when adjustment is made using weights. 1 is a diagram illustrating the relationship between the sag and span length of each span during towing and the sag and span length at the completion of laying when there is adjustment by weights. 2 is a diagram illustrating an example in which the required number of towing drones fly at high altitude. 3 is a diagram illustrating an example in which all drones fly at high altitude.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0018] First Embodiment A cable laying method according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 8 . The first embodiment provides a cable laying method using multiple general drones 100 to tow a cable 300 into the sky and lay it between utility poles 200. When operating multiple drones 100, a method is adopted in which the drones 100 cooperate to ensure maximum horizontal tension T while satisfying the pitch angle, which is a condition for stable flight of each drone 100. In other words, in this embodiment, the multiple drones 100 fly stably, and apply a horizontal tension T to the cable 300 that ensures the cable 300's height above ground after laying. Utility poles 200 are an example of an "aerial structure."

[0019] Specifically, the cable laying method of the present disclosure is a cable laying method for laying a cable 300 between utility poles 200 using multiple drones 100, and includes having each drone 100 grasp the cable 300, and each drone 100 applying horizontal tension to the cable 300 so that the cable 300 maintains a predetermined height above ground while satisfying a predetermined pitch angle.

[0020] [Laying a cable using a single drone] As a premise, consider laying a cable using a single drone 100. Due to limitations in flight mechanics, a typical drone has a pitch angle limit of approximately 30 degrees. In this disclosure, pitch angle is defined as the angle at which the payload component is tilted relative to the vertical direction, as shown in FIG. 1 . In other words, the payload is the sum of the buoyancy (vertical direction) of the drone 100 and the tractive force (horizontal direction), so pitch angle is defined as arctan (buoyancy / tractive force).

[0021] If the pitch angle exceeds approximately 30 degrees, the drone 100 will not be able to maintain stable buoyancy, and will crash without being able to support its own weight. For this reason, as shown in Figure 1, even when using a drone with a payload limit of approximately 200 N (approximately 20 kg), which is commonly used for applications such as pesticide spraying, the horizontal traction force will be 100 N at the upper limit of a pitch angle of 30 degrees. At this time, the buoyancy (vertical direction) generated at the same time will be 170 N.

[0022] 2, the relationship between the force applied when using the drone 100 to lay the cable 300 on an aerial structure such as a utility pole 200, and the laying height, sag, and height above ground is as follows: It is assumed that the drone 100 moves at a constant speed and that the wind pressure load on the cable 300 is sufficiently small. Laying height H [m] = height above ground [m] + sag D [m] Traction force [N] = horizontal tension T [N] Buoyancy [N] = cable load V [N] Payload [N] = resultant force F [N] Pitch angle = arctan (buoyancy / traction force) = arctan (cable load / horizontal tension)

[0023] It is also known that the cable 300 forms a catenary curve during and after installation, as shown in Figure 3. The shape (catenary curve) of the cable 300 during and after installation, the sag D, and the actual length L of the cable are expressed on the xy plane by the following equations: Here, a is the value obtained by dividing the horizontal tension T by the linear mass density W [N / m] of the cable 300, that is, a=T / W.

[0024] In the present disclosure, the following approximate formula obtained from the above formula is used for calculations using the slack D, horizontal tension T, and actual length L when the drone 100 pulls the cable 300. Specifically, assuming that the slack D is sufficiently small, the slack D, horizontal tension T, and actual length L can be approximated as follows by Maclaurin expansion:

[0025] Based on the above relationship, the following describes the issues that arise when a single drone 100 pulls a cable 300 with a linear mass density W = 3 [N / m] (approximately 45CR suspension wire) with reference to Figure 4. Figure 4 is a diagram illustrating the pitch angle, sag, and span length under specified conditions. Here, when pulling the cable 300 to ensure ground clearance, the horizontal pulling force tends to be greater than the cable load that should be supported by vertical buoyancy.

[0026] For example, as shown in Figure 4(A), consider laying a cable in a normal configuration, that is, with a span length S of 30 m and a sag D of 0.2 m. In this case, as shown below, the horizontal tension T required for a cable load V of 90 N is 1688 N. The pitch angle in this case is 86.95 degrees. This is beyond the performance limits of the drone 100 and is therefore not feasible.

[0027] In contrast, as shown in Figure 4(B), consider laying a cable 300 with a linear mass density W of 3 N / m while ensuring a span length S of 30 m under the condition of a pitch angle of 30 degrees or less. In this case, as shown below, it is necessary to set the sag D to 6 m. Therefore, when laying the cable 300 at a position 10 m above the ground, the ground clearance becomes 4 m, which makes it impossible to ensure the required ground clearance (5 m) above roadways, etc., as specified in the Enforcement Regulations of the Wired Telecommunications Equipment Ordinance.

[0028] Therefore, as shown in Figure 4(C), consider laying a cable 300 with a linear mass density W = 3 N / m, while satisfying the condition of a pitch angle of 30 degrees or less and ensuring the required ground clearance (= 5 m) under the ministerial ordinance. In this case, as shown below, it is not possible to handle span lengths S greater than 25 m. Therefore, if a single drone 100 is used, it is not possible to lay the cable 300 between utility poles with span lengths of approximately 30 to 50 m in urban areas. Furthermore, while special sections, such as mountainous areas, have span lengths of approximately 250 m, a single drone 100 cannot handle such long span lengths.

[0029] [Laying Work from Start Point to End Point] Here, we will explain the laying work of the cable 300 using multiple drones 100. For the cable laying work, first, a length of cable 300 to be laid at the start point is secured in advance. Then, one end of the cable 300 is grasped at a straddling position on the utility pole 200 located at the start point, and the towing drone 100 with the other end of the cable 300 attached is flown horizontally from the start point side to the end point side.

[0030] Once the cable for the planned span has been let out, the cable 300 is fixed to the next drone 100, and it flies in conjunction with the previous drone 100. This process is repeated until the required cable length is prepared from the starting point to the end point, and multiple drones 100 are placed in the air. During this placement stage up to the end point, it is only necessary to be concerned about whether the cable 300 being pulled has the required height above ground, so there is no need to strictly control the horizontal tension for pulling the cable 300.

[0031] After the cable 300 and multiple drones 100 are positioned to their end points, horizontal tension must be applied to the cable 300 toward its final form. To accomplish this, each drone 100 is positioned at a pre-programmed location, and each drone 100 is made to pull the cable at a pitch angle of 30 degrees or less. Once all drones 100 have stopped at their designated locations, the cable 300 is gripped at a position where it is strung on the utility pole 200 located at the end point. Since the actual length of the completed form remains unchanged once the cable 300 is gripped and fixed at both ends, all drones 100 are then required to release the fixed cable 300. Regarding the release method, each drone 100 may be equipped with an arm that can be opened and closed remotely, as with commercially available drones. A pitch angle of 30 degrees is an example of a "predetermined pitch angle."

[0032] When releasing, each drone 100 is lowered by a vertical distance equivalent to the expected slack at each drone's position, and the horizontal tension applied to the cable 300 by the release is gradually applied, thereby stabilizing each drone 100 and completing the laying of the cable. The method of outputting instructions to the multiple drones 100 is arbitrary, and instructions may be issued collectively to the multiple drones 100 by a control device that collectively manages the multiple drones 100, or a control device may be provided for each of the multiple drones 100.

[0033] [Removal Work] The cable 300 laid by the above-described method can be removed by following the reverse procedure of the laying procedure.

[0034] As described above, the cable laying method of the present disclosure includes: having each drone hold the cable 300 at a suspension position on the utility pole 200 located at the starting point; flying each drone horizontally from the suspension position on the utility pole 200 located at the starting point towards the suspension position on the utility pole 200 located at the end point; applying horizontal tension to the cable until each drone stops at a predetermined position; having each drone hold the cable 300 at a suspension position on the utility pole 200 located at the end point after stopping at the predetermined position; and having each drone release the cable 300 after holding the cable 300 at the suspension position on the utility pole 200 located at the end point.

[0035] [Cable Laying Method Using Multiple Drones] A cable laying method using multiple drones will now be described in more detail with reference to FIGS. 5 to 8. FIG. 5 illustrates the relationship between the slack and span length of each span during towing and the slack and span length upon completion of laying when N drones are towing the cable. As described above, the cable 300 after laying must be towed so that it has a target slack. Therefore, multiple drones 100 tow the cable 300 so that the cable 300 after laying has the target slack. For example, roughly speaking, to lay the cable 300 with a target span length S of 250 m and slack D of 10 m as the final completed form, approximately 20 drones would need to be used, controlling each drone 100 so that the slack d in each span is 0.5 m.

[0036] Specifically, the cable laying method of the present disclosure includes having each drone grasp the cable 300 at a predetermined interval, and each drone applying horizontal tension to the cable 300 so that the slack between adjacent drones is constant between each drone.

[0037] In this embodiment, as shown in FIG. 5(A), a plurality of drones 100 arranged at different spans are used to pull the cable 300 and lay it between utility poles 200. The different spans are an example of a "predetermined interval." FIG. 5 is a diagram illustrating the relationship between the slack and span length of each span during towing and the slack and span length upon completion of laying when N drones are towing the cable 300. In this embodiment, tension is applied to the cable 300 in order from the first drone located at the rightmost position in the diagram to the Nth drone located at the leftmost position. The slack between the nth drone and the n+1th drone is defined as d ｎ Let the actual length be l ｎ and the span length is s ｎ In addition, the sag between the Nth drone and the utility pole 200 is d Ｎ Let the actual length be l Ｎ and the span length is s Ｎ Let's say.

[0038] The final span length S is the span length s between the drones. ｎ The actual length L is the sum of the actual lengths l between the drones. ｎ Therefore, the span length S and the actual length L are expressed as follows: S=s (Equation 6) １ +s ２ +...+s Ｎ ...(6-1) L = l １ +l ２ +...+l Ｎ …(6-2)

[0039] Sag d between nth spans ｎ , actual length l ｎ and span length s ｎ The relationship is expressed as follows from the approximate formula (2-3):

[0040] From the equations (7-1), (7-2), and (8), the actual length L is expressed as follows: Furthermore, from the approximation formula (2-3) and formula (7), the following relationship holds:

[0041] Therefore, the relationship of the slack D at the time of completion shown in FIG. 5(B) can be expressed as follows:

[0042] Next, referring to FIG. 6, the sag d between the drones is calculated while satisfying the condition of a pitch angle of 30 degrees. ｎ When the cable 300 is pulled while ensuring a horizontal tension T of 0.5 m, the horizontal tension T, the cable load V, and the span length s are ｎ FIG. 6 is a diagram illustrating the pulling of the cable by the first drone and the second drone.

[0043] As shown in FIG. 6A, when the first drone at the front pulls the cable 300, the slack d ｎ is set to a common value of 0.5 m for each drone, the horizontal tension T and cable load V that result in a pitch angle of 30 degrees are 1.7 N and 2.9 N, respectively, when the linear mass density W = 3 N / m.

[0044] As shown in FIG. 6B, the second drone and subsequent drones pull the cable 300 with the total horizontal tension obtained by adding the horizontal tension of the drone 100 before them to their own horizontal tension. ｎ When n is shared, the span length s between drones gradually increases (i.e., as n increases). ｎ Specifically, the horizontal tension T1 applied to the portion of the cable 300 of the rightmost span S1 is 1.7 N, while the horizontal tension T2 applied to the portion of the cable 300 of the second span S2 is 6.0 N. Here, the difference between the horizontal tensions T2 and T1 is the horizontal tension applied to the cable 300 by the second drone.

[0045] FIG. 7 shows the relationship between the drones and the slack d ｎ7 is a table explaining the distance between drones when the drones share a common cable 300. The linear mass density of the cable 300 is 3.0 N / m. The required horizontal tension increases as the drone number n increases. In contrast, in this embodiment, as described above, the cable 300 can be pulled by the total horizontal tension obtained by adding the horizontal tension of the drone 100 in front of it to the horizontal tension of the drone itself. This makes it possible to adequately handle cases where the horizontal tension increases as the drone number n increases. The table in FIG. 7 also shows how the total horizontal tension applied to the cable 300 increases as the drone number n increases. The cable load V applied to each drone also increases as the drone number n increases.

[0046] Figure 8 shows the relationship between the sag and span length for each span during towing and the sag and span length at the end of laying. Figure 8(A) shows the relationship between the sag and span length for each span during laying, and Figure 8(B) shows the relationship between the sag and span length at the end of laying. During laying, the sag d between each drone is ｎ As explained so far, the sag is constant during installation, so the span length s ｎ increases as n increases.

[0047] According to this embodiment, multiple drones 100 are flown at the same altitude while maintaining the same slack, which simplifies operation. In addition, it is possible to ensure sufficient ground clearance.

[0048] (Second Embodiment) A cable laying method according to a third embodiment of the present disclosure will be described with reference to FIGS. 9 to 11 . FIG. 9 is a diagram illustrating the pulling of a cable by a first drone and a second drone when adjustment is performed using weights. In the third embodiment, in order to generate as much horizontal tension as possible within the pitch angle limits, a vertical weight 400 is intentionally added to the drone 100 within the payload limit, thereby maximizing the horizontal tension applied to the cable 300. This makes it possible to reduce the number of drones required for a given span length S. Providing the weight 400 is an example of a method of applying a vertical load to each drone.

[0049] Specifically, the cable laying method of the present disclosure includes applying a vertical load to each drone.

[0050] Specifically, as shown in Figure 9(A), weights 400 are added to each drone. The horizontal tension that each drone 100 can pull while maintaining a pitch angle of 30 degrees relative to the cable load is as described above. In contrast, by adding and adjusting a weight or the like as a vertical load, it is possible to increase the horizontal tension applied to the cable while maintaining a pitch angle of 30 degrees.

[0051] In this embodiment, the cable 300 can also be pulled by a total horizontal tension obtained by adding the horizontal tension of the drone 100 in front of it to the horizontal tension of the drone itself. Specifically, as shown in FIG. 9B , the horizontal tension T1 applied to the portion of the cable 300 in the rightmost span S1 is 100.0 N, while the horizontal tension T2 applied to the portion of the cable 300 in the second span S2 is 200.0 N. Here, the difference between horizontal tension T2 and T1 is the horizontal tension applied to the cable 300 by the second drone. As the horizontal tension required for each drone differs in this way, the weight of the weight 400 may be different for each drone. Specifically, in this embodiment, the horizontal tension of the drone 100 in front of it can be utilized, so the weight of the weight 400 is reduced as the drone number n increases.

[0052] FIG. 10 is a table illustrating the number of drones, the spacing between drones, and other factors when weight adjustment is used. As described above, by adding weights or other factors as a vertical load and adjusting the pitch angle, it is possible to increase the horizontal tension applied to the cable 300 while maintaining a pitch angle of 30 degrees. The table in FIG. 10 also shows how the total horizontal tension applied to the cable 300 increases as the drone number n increases. This, as shown in FIG. 10 , makes it possible to reduce the number of drones 100 required compared to the case described in the second embodiment. Note that the cable load V applied to each drone also increases as the drone number n increases.

[0053] Figure 11 shows the relationship between the sag and span length for each span during towing and the sag and span length at the end of laying. Figure 11(A) shows the relationship between the sag and span length for each span during laying, and Figure 11(B) shows the relationship between the sag and span length after laying. During laying, the sag d between each drone is ｎ As explained so far, the sag is constant during installation, so the span length s ｎ increases as n increases. Similarly, the horizontal tension also increases in the following order: horizontal tension T1 of the first drone, horizontal tension T2 of the second drone, horizontal tension T3 of the third drone, horizontal tension T4 of the fourth drone, horizontal tension T5 of the fifth drone, and horizontal tension T6 of the sixth drone.

[0054] According to this embodiment, multiple drones 100 are flown at the same altitude while maintaining the same slack, which simplifies operation. It is also possible to ensure sufficient ground clearance. Furthermore, as described above, the number of drones 100 required can be reduced.

[0055] It should be noted that load adjustment can be achieved by changing the length of the cable 300 attached to the drone 100, rather than by using weights. However, this would result in a longer required length of cable 300, resulting in waste. Furthermore, in order to tow the drone while ensuring sufficient ground clearance, a certain drone must fly higher than the other drones by the increased length, which would cause problems with contact with high-voltage lines and stable flight under high wind pressure. For this reason, load adjustment can be achieved solely by using weights or the like.

[0056] (Third Embodiment) A cable laying method according to a fourth embodiment of the present disclosure will be described with reference to Fig. 12. Fig. 12 is a diagram illustrating how a required number of drones 100 fly at a high altitude. In the above embodiment, the description is given on the assumption that multiple drones 100 fly at the same altitude. However, the scope of the present disclosure is not limited to this, and only a required number of tow drones may fly at a high altitude.

[0057] As an example, Figure 12(A) shows a state in which one towing drone is flying at high altitude. This method allows the cable 300 to be towed with simple operation.

[0058] 12(B) shows an example in which multiple tow drones fly at high altitude. This method allows for more efficient towing of the cable 300 than a single tow drone flying at high altitude.

[0059] (Fourth embodiment) A cable laying method according to a fifth embodiment of the present disclosure will be described with reference to Fig. 13. Fig. 13 is a diagram illustrating how all drones 100 fly at a high altitude. As shown in Fig. 13, the cable 300 may be towed by having all drones 100 fly at a high altitude. This allows the cable 300 to be towed suitably and simplifies operation.

[0060] (Other Examples) In each of the above embodiments, the span length S is set to approximately 250 m to 300 m as an example, but by increasing the number of drones, it is possible to lay an aerial cable without restrictions on the span length S, within the range allowed by the tensile strength of the aerial structure and the towing cable 300.

[0061] (Effects) According to each embodiment of the present disclosure, overhead cable installation work, which conventionally required work on the ground, can be performed while the cable is held in the air, thereby enabling safe installation work to be performed regardless of the conditions on the ground from the start point to the end point of the cable installation route.

[0062] Furthermore, according to each embodiment of the present disclosure, there is no need for back-and-forth work between spans, as in a construction method in which a single drone is used to pull a towing line between spans, and then the towing equipment is gradually made thicker, such as a towing cord and a towing rope, and finally the desired cable is towed and laid.

[0063] 100: Drone 200: Telephone pole 300: Cable 400: Weight

Claims

1. A cable laying method for laying a cable between aerial structures using multiple drones, the cable laying method comprising: causing each of the drones to grasp the cable; and applying horizontal tension to the cable by each of the drones so that the cable maintains a predetermined height above ground while satisfying a predetermined pitch angle.

2. The cable laying method of claim 1, comprising: having each of the drones grasp the cable at a predetermined interval; and each of the drones applying the horizontal tension to the cable so that slack between adjacent drones is constant between each of the drones.

3. The cable laying method according to claim 2, further comprising: applying a vertical load to each of the drones.

4. The cable laying method of claim 1, comprising: holding the cable at a suspension position of the aerial structure located at a starting point; flying each of the drones horizontally from the suspension position of the aerial structure located at the starting point toward the suspension position of the aerial structure located at an end point; applying the horizontal tension to the cable until each of the drones stops at a predetermined position; holding the cable at the suspension position of the aerial structure located at the end point after each of the drones has stopped at the predetermined position; and releasing the cable by each of the drones after holding the cable at the suspension position of the aerial structure located at the end point.

Images