Cable installation system

Abstract

The present invention addresses the problem of providing a cable installation system and a method therefor, which make it possible to shorten a time until work is started in a spanning cable drawing work using a flight vehicle.　A cable installation system according to the present invention bridges a cable 50 between two columns 10, the installation system comprising: a flight vehicle that grips one end of the cable 50 and moves from one column 10 to the other; and a calculation device 40 that calculates a flight path of the flight vehicle from a distance D between the input columns 10, a flight start position 31 of the flight vehicle, a flight end position 33 of the flight vehicle, and a minimum ground height a of the cable 50, wherein the flight path is composed of a takeoff flight section d1 that linearly connects the flight start position 31 to a switching point 32 and a stable flight section d2 that linearly connects the switching point 32 to the flight end position 33, and the calculation device 40 calculates the flight path so that the switching point 32 is the position of the flight vehicle at which the lowest point 51 of the cable 50 becomes the lowest ground height a.

Description

Cable Installation System

[0001] The present disclosure relates to a system and method for pulling a cable between spans using an air vehicle.

[0002] When pulling a cable between utility poles 10 and another utility pole 10, as shown in Figure 1, a towing rope or the like called a pulling string 51 must be connected to the tip of cable 50, and a worker 20 must pull the pulling string 51 using a pulley 11 or the like. As the span distance increases, the pulling force and work time for cable pulling work also increase, and workers 20 must be stationed not only on the pulling side but also on the cable payout side.

[0003] NTT e-drone website, "Omakase e-drone," retrieved April 14, 2023 (https: / / www.nttedt.co.jp / omakase-cable)

[0004] 2 is a diagram illustrating the operation of pulling a cable between spans using an aircraft such as that described in Non-Patent Document 1. In this operation, a cable 50 is grasped by a drone 30 having a cable grasping mechanism, and the drone 30 is flown from one utility pole 10 to another utility pole 10, thereby making it possible to pull the cable regardless of obstacles between the spans.

[0005] However, when attempting to carry out work such as that shown in Figure 2, there were difficulties in that drone flight required complex calculations using various parameters, and accurate measurement of the distance between utility poles (span distance) was impossible without going to the construction site. In other words, when attempting to carry out work such as that shown in Figure 2, complex calculations had to be performed after measuring the span distance, making it difficult to shorten the time until work could begin.

[0006] Therefore, in order to solve the above problems, an object of the present invention is to provide a cable installation system and method that can shorten the time until the start of work in span cable installation work using an aircraft.

[0007] In order to achieve the above object, the cable installation system according to the present invention is capable of calculating the flight path of an aircraft by inputting only four parameters.

[0008] Specifically, the cable erection system of the present invention is an erection system that spans a cable between two pillars, and comprises: an aircraft that holds one end of the cable and moves from one pillar to the other; and a calculation device that calculates the flight path of the aircraft from the input distance between the pillars, the aircraft's flight start position, the aircraft's flight end position, and the cable's minimum ground clearance, wherein the flight path consists of a takeoff flight section that connects the flight start position to a switching point in a straight line, and a stable flight section that connects the switching point to the flight end position in a straight line, and the calculation device calculates the flight path so that the switching point is the position of the aircraft where the lowest point of the cable is at the minimum ground clearance.

[0009] Furthermore, a cable installation method according to the present invention is a method for suspending a cable between two pillars, which comprises: holding one end of the cable with an aircraft and moving it from one of the pillars to the other; and calculating a flight path of the aircraft from the input distance between the pillars, the flight start position of the aircraft, the flight end position of the aircraft, and the minimum ground clearance of the cable; wherein the flight path consists of a takeoff flight section connecting the flight start position to a switching point in a straight line, and a stable flight section connecting the switching point to the flight end position in a straight line; and wherein when calculating the flight path, the position of the aircraft where the lowest point of the cable is at the minimum ground clearance is taken as the switching point.

[0010] This cable installation system and method can calculate the flight path of the aircraft by inputting only four parameters, allowing for a quick determination of whether construction is possible. Therefore, the present invention can provide a cable installation system and method that can shorten the time until work begins in span cable installation work using an aircraft.

[0011] The calculation device of the cable erection system of the present invention is characterized in that it calculates the slack and actual cable length from the optimal tension set for the cable stretched between the pillars, the weight per unit length of the cable, and the span distance.

[0012] The computing device of the cable erection system according to the present invention is characterized in that it calculates the flight attitude and flight speed of the flying object from the flight path and external forces from the natural world.

[0013] The computing device of the cable installation system according to the present invention is characterized in that it calculates the maximum horizontal tension generated when the cable is installed based on the payload of the aircraft and the flight path.

[0014] The arithmetic device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0015] The above inventions can be combined as much as possible.

[0016] The present invention can provide a cable installation system and method that can shorten the time until the start of work in span cable installation work using an aircraft.

[0017] FIG. 1 is a diagram illustrating a conventional cable installation method. FIG. 2 is a diagram illustrating a cable installation method using an aircraft. FIG. 3 is a diagram illustrating a cable installation system according to the present invention. FIG. 4 is a diagram illustrating a cable installation system according to the present invention. FIG. 5 is a diagram illustrating a computing device of the cable installation system according to the present invention. FIG. 6 is a diagram illustrating a cable installation method according to the present invention. FIG. 7 is a diagram illustrating calculations performed by the computing device of the cable installation system according to the present invention. FIG. 8 is a diagram illustrating calculations performed by the computing device of the cable installation system according to the present invention. FIG. 9 is a diagram illustrating calculations performed by the computing device of the cable installation system according to the present invention. FIG. 10 is a diagram illustrating calculations performed by the computing device of the cable installation system according to the present invention. FIG. 11 is a diagram illustrating calculations performed by the computing device of the cable installation system according to the present invention.

[0018] The following description of the preferred embodiments of the present invention will be given with reference to the accompanying drawings. The preferred embodiments described below are examples of the present invention, and the present invention is not limited to the preferred embodiments. In this specification and the drawings, components having the same reference numerals are intended to represent the same components.

[0019] 3 is a diagram illustrating the cable installation system of this embodiment. This cable installation system is an installation system that suspends a cable 50 between two poles 10, and includes a flying object that holds one end of the cable 50 and moves from one pole 10 to the other, and a distance D between the poles 10 that is input, a flight start position 31 of the flying object, a flight end position 33 of the flying object, and a minimum ground height h of the cable 50. ｕ and a calculation device 40 that calculates a flight path 35 of the aircraft from the above, wherein the flight path 35 is comprised of a takeoff flight section d1 that connects a flight start position 31 to a switching point 32 in a straight line, and a stable flight section d2 that connects a switching point 32 to a flight end position 33 in a straight line, and the calculation device 40 ... ｕ The flight path 35 is calculated so that the position of the aircraft where the switching point 32 satisfies the condition (above) is the position of the aircraft where the switching point 32 satisfies the condition (above). In this embodiment, the aircraft will be described as a drone 30.

[0020] This cable erection system is configured by the distance D between utility poles, the flight start position 31, the flight end position 33, and the minimum ground height h of the cable. ｕ Based on this, the optimal speed and flight path of the drone 30 is calculated. Here, the flight start position 31 is the ground near the utility pole 10 to which the cable reel-out device 12 is attached. The flight end position 33 refers to the cable receiving bracket of the cable receiving device 13, the position above the cable receiving bracket, or the position below the cable receiving bracket. The calculation by the calculation device 40 is based on the assumptions shown in FIG. 4 and the following assumptions. [Assumptions] (1) The drone 30 starts flying near the utility pole 10 to which the cable reel-out device 12 is attached, and an arbitrary distance from the utility pole is set as the "takeoff flight section d1" of the drone 30 (see drone 30(i)). (2) When the drone 30 leaves the "takeoff flight section d1", the lowest point of the cable 50 is at the minimum ground clearance h ｕThat's all (see drone 30(ii) and lowest point 53(ii)). (3) The flight trajectory of drone 30 is changed at the boundary between the "takeoff flight section d1" and the "stable flight section d2" (switching point 32). (4) The flight of drone 30 is made to be a natural trajectory without sudden ascents / descents (a natural flight trajectory is, for example, a straight line). (5) The speed of drone 30 is kept constant during takeoff flight. (6) It is acceptable for cable 50 to be on the ground in the "takeoff flight section d1".

[0021] 5 is a diagram illustrating the calculation device 40. The calculation device 40 includes an input unit 41 and a calculation unit 42. The input unit 41 receives inputs from the outside, such as the distance between the pillars D, the flight start position 31, the flight end position 33, and the minimum ground clearance h ｕ are input. For example, these may be input by an operator. The input information is passed to the calculation unit 42. The calculation unit 42 calculates the flight attitude and optimal route of the drone 30 from this information.

[0022] 6 is a diagram illustrating the calculation performed by the calculation unit 42. The calculation unit 42 calculates an optimal tension based on the type of cable to be laid between the utility poles 10 and the distance between the utility poles (span distance D) (step S01). Specifically, the calculation unit 42 measures the distance S between the utility poles 10 (a design value may be input), and calculates an optimal tension T based on the type of cable 50 to be laid between the utility poles 10 (cable weight W per unit length) and the distance S between the utility poles 10. Here, the optimal tension T is a tension that is equal to or less than the breaking strength of the cable at the expected maximum wind speed and that increases the minimum ground clearance of the cable above a predetermined height.

[0023] Next, the calculation unit 42 calculates the slack from the tension and cable weight, and confirms that the slack does not fall below the minimum ground clearance. The calculation unit 42 then calculates the actual cable length and confirms the cable length to be used for pulling (step S02). Specifically, the calculation unit 42 uses equation (1) to calculate the slack D from the tension T calculated in step S01 and the weight W per unit length of the cable 50. The calculation unit 42 calculates the minimum ground clearance h ｕThen, the calculation unit 42 calculates the length L of the cable 50 used for pulling (actual cable length) using the formula (2). After step S12, by pulling out the required actual length of cable 50 from cable drum 52 in advance, it is possible to reduce errors between the various values ​​(including the flight path) calculated by the calculation device 40 and the values ​​(including the flight path) during the pulling work.

[0024] Next, calculation unit 42 calculates flight path 35 of drone 30 from flight start position 31 and flight end position 33 of drone 30 (step S03). The tip of cable 50 pulled out from cable drum 52 may be passed through cable reel-out device 12 in advance and then lowered to the ground, and the tip of cable 50 placed on the ground may be gripped by a cable gripping unit of drone 30. Alternatively, the tip of cable 50 may be gripped by a cable gripping unit of drone 30 near cable reel-out device 12. In other words, flight start position 31 may be on the ground near utility pole 10 on which cable reel-out device 12 is installed, or may be in the air above it (near cable reel-out device 12).

[0025] 3, the flight path 35 is composed of a takeoff flight section d1 that connects the flight start position 31 to the switching point 32 in a straight line, and a stable flight section d2 that connects the switching point 32 to the flight end position 33 in a straight line. ｕ The flight path 35 is calculated so that the position of the drone 30 where

[0026] Next, in addition to the above calculation results, the drone's flight attitude and speed can be calculated by taking into account external forces such as wind speed around the work environment.

[0027] Next, from the maximum weight (payload M) that the drone can carry and the flight path 35 calculated above, the maximum horizontal tension F when pulling through is calculated. ｆｍａｘ In a static state, the cable 50 having a catenary curve shape is subjected to a horizontal tension T expressed by the following equation: ０ occurs.

[0028] FIG. 14 shows the relationship between payload M and horizontal tension F ｆ The payload M is the weight that can be transported vertically downward. On the other hand, the horizontal tension F ｆ is the tension applied to the drone 30 in the flight direction, and is the horizontal tension T ０ and wind pressure load T from the side of the cable ｗ (See Supplementary Note 4) In order to perform the pulling work, the payload M must be pulled with a horizontal tension F ｆ [Equation 2b] M>F ｆ tan θ = (T ０ +T ｗ ) tan θ, where θ is the flight angle of the drone 30 as shown in FIG. 14 (the angle between the horizontal and the straight line connecting the flight start position and the current position of the drone 30). From equation (2b), the horizontal tension F ｆ The maximum value of F ｆｍａｘ can be calculated.

[0029] The above makes it possible to calculate the payload capacity and flight path required for the drone when flying.

[0030] [Supplementary Note 1] A specific method for calculating the flight path 35 is described below. Here, the case where the flight start position 31 is the ground near the utility pole 10 is described. Supplementary Notes 1 to 4 relate to the flight path 35 of the takeoff flight section d1. The conditions for the takeoff flight section d1 are as follows: (1) The drone must maintain a minimum ground clearance when it leaves the "takeoff flight section d1." In other words, the switching point 32 is the position of the drone 30 where the lowest point of the cable (i.e., the minimum ground clearance) becomes the first time after takeoff. (2) The flight path 35 must be changed at the switching point 32 (from the takeoff flight section d1 to the stable flight section d2). (3) The flight path 35 must be as natural as possible (a natural flight path is a path connecting the start point and end point in a straight line). (4) The cable 50 must not be paid out from the cable payout device 12 during the takeoff flight section d1. (5) The speed of the drone 30 must be constant (user-input value) during the takeoff flight section d1. (6) The cable 50 may be in contact with the ground during the takeoff flight section d1.

[0031] First, the initial cable length L ０ Set the initial cable length L ０ The initial cable length L is the length from the cable payout device 12 installed on the utility pole 10 to the tip of the cable held by the drone 30 before the drone flies. ０ does not change until the drone 30 reaches the switching point 32.

[0032] FIG. 7 is a diagram illustrating the calculation for deriving the switching point 32. When the drone 30 starts flying, the tip of the cable 50 is lifted, and when the drone 30 reaches a certain altitude, the lowest point 53 of the cable 50 leaves the ground. The position of the drone 30 at this time is called the lift-off point. More precisely, the lift-off point is a point on the takeoff flight trajectory (the straight line connecting the flight start position 31 and the switching point 32) and also a point on a catenary curve where the lowest point 53 touches the ground. Once the lift-off point has passed, the shape of the cable 50 can be approximated by a catenary curve.

[0033] The switching point 32 is a point on the boundary between the takeoff flight section d1 and the stable flight section d2, and the lowest point 53 is at the minimum ground clearance h ｕ The point on the catenary curve that passes through the cable and is tangent to a plane parallel to the ground. The cable length at that time is the initial cable length L ０ If the lowest point 53 is taken as the origin, the catenary curve can be expressed by the following equation. The x-axis is horizontal and the y-axis is vertical. ｕ is a preset value. The cable start point P(-m, H) is the position of the cable payout device 12 and is known. Since the cable start point P is on a catenary curve, H can be expressed by the following equation. Moreover, since the switching point 32 (coordinates are (S-m, h)) is also on the catenary curve, h can be expressed by the following equation. Since the catenary curve is symmetrical about the Y axis, the sign of m can be either.

[0034] Initial cable length L ０ is the sum of the length of the catenary curve on the cable start point P side and the length on the switching point 32 side, and can be expressed by the following equation: Under the condition of equation (6), a group of coordinate points of the switching point 32 can be obtained from equations (4) and (5). That is, the switching point 32 can be obtained according to the position of the lowest point 53 (since the lowest point 53 is the origin in the equation, the cable start point P is varied as a parameter). From the many obtained switching points 32, it is sufficient to select one that allows cable installation work. Note that when the bottom of the utility pole 10 is the origin, m is set in the x direction and the minimum ground clearance h is set in the y direction. ｕ Just translate it by the amount of .

[0035] The flight trajectory 35 of the drone 30 in the takeoff flight section d1 is determined based on the flight start position 31 (X １ , Y １ ) and switching point 32 (X ２ , Y ２ ) (See Figure 8. The coordinate system is different from that in Figure 7.) Taking into consideration that the flight path may be a vertical line or a horizontal line, the line equation is set to ax + by + c = 0. Because this line passes through the flight start position 31 and the switching point 32, any point on the line is equal to the slope of the section between the flight start position 31 and the switching point 32, and therefore satisfies the following equation. Rearranging equation (7), Then, a = Y ２ -Y １ , b=X １ -X ２ , c=X ２ Y １ -X １ Y ２ By substituting the coordinates of the flight start position 31 given as parameters and the coordinates of the switching point 32 described in FIG. 7, the flight trajectory 35 of the drone 30 in the takeoff flight section d1 can be obtained.

[0036] Similarly, the flight trajectory 35 of the drone 30 in the stable flight section d2 is also a straight line equation that includes two points, the flight end position 33 and the switching point 32, specified by the user.

[0037] [Supplementary Note 2] A method for calculating the current point of the drone 30 will be described using Figure 9. The current point R is on the flight trajectory 35 of the takeoff flight section d1, and is a point a certain time t after the flight start position 31. If the speed of the drone 30 in the takeoff flight section d1 is V, and if an arbitrary origin is O, the position (cable start point) of the cable payout device 12 is P, and the switching point 32 is Q, the movement velocity vector is expressed by the following equation. The position vector of the current point R is expressed by the following equation. Note that the increment of t (the amount of change per movement) needs to be adjusted depending on whether the unit of the slider is span length or movement time.

[0038] [Supplementary Note 3] Figure 10 is a diagram for explaining the method for calculating the cable curve equation. ０ -m, Y ０ ) is given, the cable 50 will be a catenary curve passing through the cable start point P and the current point R. The cable length at that time is the initial cable length L specified by the user. ０ When the ground height of the flight start position 31 is set to y=0, the catenary curve described by the cable 50 is given by the following equation. The cable start point P and the current point R are on a catenary curve, and the catenary curve is symmetrical with respect to the Y axis, so the sign of m is arbitrary. In addition, the cable length can be expressed as follows: The catenary curve of the cable 50 can be obtained by solving "a" and "b" from equations (12) and (13) and substituting them into equation (11).

[0039] [Supplementary Note 4] Here, we will explain how to calculate the tension T generated in the cable. In the catenary curve formula (11), the coefficient a is the horizontal tension T ｈ (N), the weight per unit of the cable W (kg / m), and the gravitational acceleration g can be expressed as follows: Therefore, the horizontal tension is T ｈ = aWg. Also, the vertical tension T ｖ (N) depends on the weight of the cable, so by substituting equation (14) into equation (13) for the cable length, In addition, the wind pressure load from the side of the cable is Tｗ (N), the resultant tension T(N) is given by the following equation.

[0040] In addition, the wind pressure load T ｗ is derived as shown in Figure 11. When considering wind blowing directly sideways against the cable 50, the force of the wind (wind pressure) affects the cable weight as a wind pressure load. According to the Ministry of Economy, Trade and Industry's "Interpretation of Technical Standards for Electrical Equipment (Reference Material 1)," the Class A wind pressure load on an overhead wire is 980 Pa (assuming a wind speed of 40 m / s), and the cable outer diameter is D (mm) and the gravitational acceleration is g (m / s ２ ) and the wind pressure load P per meter calculated using the same coefficient ４０ (kg / m) is calculated by the following formula: P ４０ = 980 ÷ g × D × 10 －３ [kg / m] If this value is based on an assumed wind speed of 40 m / s, wind pressure is proportional to the square of the wind speed (Reference Material 2), so the wind pressure load Pc (kg / m) at any wind speed V (m / s) is calculated using the following formula: Pc = 980 ÷ g × D × 10 －３ × (V / 40) ２ In other words, the conditions for considering the effect of wind on a cable are as follows: - Only consider the wind component blowing directly beside the cable installation direction. - The wind pressure acting on the cable is based on the Class A wind load value of "980 Pa at a wind speed of 40 m / s." - The drag coefficient when calculating wind load does not change depending on the wind speed, and the wind load is proportional to the square of the wind speed. - The parameters are "wind speed from directly beside (m / s)" and "cable outer diameter (mm)." [References] Reference 1: https: / / www.meti.go.jp / policy / safety_security / industrial_safety / law / files / dengikaishaku.pdf Reference 2: https: / / journal.ntt.co.jp / policy / safety_security / industrial_safety / law / files / dengikaishaku.pdf jp / backnumber2 / 0709 / files / jn200709104. pdf

[0041] Based on this Pc, the wind pressure load on the drone is half of the wind pressure load on the entire cable, so if we change the unit to [N], we can calculate it as follows.

[0042] [Supplementary Note 5] Supplementary Notes 5 to 7 relate to the flight path 35 in the stable flight section d2 (see Figure 12). The conditions in the stable flight section d2 are as follows: (1) In the stable flight section d2, the cable 50 must be paid out at a constant speed from the cable payout device 12. Payout of the cable 50 must not be stopped. (2) In the stable flight section d2, the lowest point of the cable must be at the minimum ground clearance. (3) The movement speed of the drone 30 must be variable so as to satisfy the above conditions (1) and (2).

[0043] [Supplementary Note 6] Figure 13 is a diagram explaining a method for calculating the cable curve formula. When the drone 30 flies in the stable flight section d2, the catenary curve passes through the cable start point P and the current point R, and is ｕ The cable length L at this time is the cable length L designated by the user. ０ The cable length is the length obtained by adding the length of the cable 50 paid out from the cable payout device 12 to the length of the cable 50 paid out from the cable payout device 12. The cable payout speed of the cable payout device 12 is V ｌ Then, the cable length L at the elapsed time t is: L = L ０ +V ｌ It becomes t.

[0044] In a coordinate system with the origin at the bottom of the utility pole 10 where the cable start point P is located, if the flight path (straight line) in the stable flight section d2 is [Equation 18] Ax + By + C = 0, then in the coordinate system of Figure 13, the horizontal movement in the X direction is expressed as the following equation. [Equation 19] A(x - m １ ) + By + C = 0 Since the cable start point P and the current point R are on the catenary curve, The cable length is expressed by the following formula: Since the current point R is on the line of equation (18), [Equation 22] A (m ２ +m １ ) + Bh + C = 0. Here, equations (19) to (21) are １ , m ２ , h, the coordinates of the current point R (m ２ , h) can be derived. If the bottom of the starting pole is regarded as the origin, m １ It is necessary to translate it just parallel.

[0045] [Appendix 7] Here, we will explain how to calculate the drone movement speed. The current point R (a function of t) can be calculated from Appendix 6. Therefore, the drone movement speed is calculated by numerical differentiation. (1) Two-point approximation: Set Δt to a small value, calculate the current point at time t and the point immediately after Δt, and take the average. (2) Central Difference Approximation: Δt is set small, and the points immediately before time t - Δt and immediately after time t + Δt are calculated, and the average is taken. The value of Δt and the method to be selected are determined by actually carrying out a simulation and taking into consideration the processing speed, the amount of fluctuation in the speed, and the like.

[0046] 10: Utility pole 11: Pulley 12: Cable payout device 13: Cable receiving device 20: Worker 30: Drone (air vehicle) 31: Flight start position 32: Switching point 33: Flight end position 35: Flight path 40: Computing device 41: Input unit 42: Calculation unit 50: Cable 51: Towing string 52: Cable drum 53: Lowest point

Claims

1. An installation system for spanning a cable between two pillars, comprising: an aircraft that holds one end of the cable and moves from one pillar to the other; and a calculation device that calculates the flight path of the aircraft from the input distance between the pillars, the flight start position of the aircraft, the flight end position of the aircraft, and the minimum ground clearance of the cable, wherein the flight path consists of a takeoff flight section that connects in a straight line from the flight start position to a switching point, and a stable flight section that connects in a straight line from the switching point to the flight end position, and wherein the calculation device calculates the flight path so that the switching point is the position of the aircraft where the lowest point of the cable is at the minimum ground clearance.

2. The erection system according to claim 1, characterized in that the computing device calculates the sag and actual cable length from the optimal tension set for the cable stretched between the pillars, the weight per unit length of the cable, and the span distance.

3. The installation system according to claim 1, characterized in that the computing device calculates the flight attitude and flight speed of the flying object from the flight path and external forces from the natural world.

4. The installation system according to claim 1, wherein the computing device calculates the maximum horizontal tension generated when the cable is stretched based on the payload of the aircraft and the flight path.

5. An installation method for spanning a cable between two pillars, comprising: holding one end of the cable with an aircraft and moving it from one of the pillars to the other; and calculating the flight path of the aircraft from the input distance between the pillars, the flight start position of the aircraft, the flight end position of the aircraft, and the minimum ground clearance of the cable, wherein the flight path consists of a takeoff flight section connecting in a straight line from the flight start position to a switching point, and a stable flight section connecting in a straight line from the switching point to the flight end position, and wherein when calculating the flight path, the position of the aircraft where the lowest point of the cable is at the minimum ground clearance is taken as the switching point.

6. The method of erection according to claim 5, characterized in that the sag and actual cable length are calculated from the optimum tension set for the cable stretched between the pillars, the weight per unit length of the cable, and the span distance.

7. The installation method according to claim 5, characterized in that the flight attitude and flight speed of the flying object are calculated from the flight path and external forces from the natural world.

8. The installation method according to claim 5, further comprising calculating a maximum horizontal tension generated when the cable is stretched from the payload of the flying object and the flight path.

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