Tilting power multi-rotor unmanned aerial vehicle for routing inspection of steel cable cableway and routing inspection method

Abstract

The invention provides a tilting power multi-rotor unmanned aerial vehicle for routing inspection of a steel cable ropeway and a routing inspection method, and belongs to the technical field of unmanned aerial vehicle routing inspection and specialized robots. The tilting power multi-rotor unmanned aerial vehicle specifically comprises a vehicle body, a clamp mechanism, a magnetic detection load, a power unit and a tilting mechanism, the clamp mechanism is located below the vehicle body, and the clamp mechanism can be detachably connected with a steel cable; the machine body is kept above the steel cable, and the magnetic detection load is arranged on the clamp mechanism, can be coupled with the steel cable and is used for carrying out magnetic detection on the steel cable; the machine body can be indirectly connected with the steel cable through work of the clamp mechanism, then the power unit is turned over and moved through work of the tilting mechanism, the power output direction is changed, and therefore the machine body and the magnetic detection load move in the length direction of the steel cable; the device can be quickly separated from the steel cable and can be quickly connected with the steel cable in the next section after crossing the supporting tower, so that the detection efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of drone inspection and special robot technology, and particularly relates to a tilt-powered multi-rotor drone and inspection method for cableway inspection. Background Technology

[0002] As an important transportation tool that crosses complex terrains such as mountains and rivers, cableways are widely used in fields such as mining material transportation, scenic sightseeing, river crossing transportation, and special engineering. Its core load-bearing components—the load-bearing cable (main cable) and auxiliary steel cables such as traction cables and balance cables—are exposed to the outdoor environment for a long time, and are subjected to multiple stresses such as alternating loads, wind and rain erosion, temperature changes, and accidental impacts. If the steel cable fails, it may lead to a catastrophic accident. Therefore, regular inspection and condition assessment are key links to ensure the safe operation of cableways.

[0003] Traditional inspection methods mainly rely on manual climbing, ground observation, fixed sensors, or cable-walking robots. Manual inspection is inefficient and risky. If cable-walking robots are used to inspect steel cables, complex mechanisms such as wheels, clamping, and anti-slip are often required on the robots, resulting in bulky structures, difficulty in crossing support towers, and high deployment costs. Summary of the Invention

[0004] The purpose of this invention is to provide a tilt-powered multi-rotor drone and inspection method for cableway inspection, which can connect to the cable and maintain a statically stable attitude, quickly detach from the cable and cross the support tower, and repeat the inspection operation process, thereby improving the efficiency of the inspection operation.

[0005] To achieve the above objectives, in a first aspect of the present invention, a tilt-powered multi-rotor unmanned aerial vehicle (UAV) for cableway inspection is provided, comprising a fuselage, a clamping mechanism, a magnetic detection payload, a power unit, and a tilting mechanism. The power unit enables the fuselage to be positioned above the cableway. The clamping mechanism is connected to the fuselage and located below it, allowing for detachable connection between the clamping mechanism and the cableway, and maintaining the fuselage above the cableway. The magnetic detection payload is mounted on the clamping mechanism and coupled to the cableway for magnetic detection. The power unit provides power for the movement of the fuselage. The tilting mechanism is connected between the power unit and the fuselage, allowing the tilt angle of the power unit to be changed, thereby adjusting the power output direction.

[0006] Furthermore, the clamping mechanism includes two clamps that can move closer to or further apart from each other. Each clamp is provided with a mating groove. When the steel cable is clamped by the two clamps, the steel cable is located in the mating groove.

[0007] Furthermore, the magnetic detection load is coaxially arranged with the clamping mechanism, so that when the clamping mechanism moves along the length of the steel cable for inspection, the detection position of the magnetic detection load corresponds to the body posture.

[0008] Furthermore, the magnetic detection load is a magnetic flux leakage sensor array, a Hall sensor array, or a magnetoresistive sensor array.

[0009] Furthermore, the clamping mechanism also includes a magnetic attraction unit, which can provide normal attraction force to the steel cable.

[0010] Furthermore, a contact detection component is provided above the clamping mechanism. When the steel cable is coupled to the contact detection component, the clamping mechanism is activated.

[0011] Furthermore, the weight of the clamping mechanism is greater than the weight of the machine body. When the clamping mechanism is connected to the steel cable, the overall center of gravity is located below the steel cable.

[0012] A second aspect of the present invention provides a method for inspecting cableways, which utilizes a tilt-powered multi-rotor drone for inspecting steel cableways as described in the first aspect above. The method includes the following steps: S1. Position the aircraft above the designated section of the steel cable, align the steel cable with the aircraft's position, and adjust the aircraft's heading. S2. After the steel cable is aligned with the machine body, the machine body moves downward. When the steel cable is in the clamping area, the clamping mechanism is activated and connected to the steel cable through the clamping mechanism. S3. Adjust the attitude of the power unit so that the power unit can output thrust along the length of the steel cable, so that the body and the magnetic detection load can move along the length of the steel cable and the steel cable can be detected by the magnetic detection load. S4. After completing the inspection of the designated section of steel cable, tilt the power unit back to the vertical position, release the clamp lock and detach it from the steel cable, so that the machine body crosses the support tower, and repeat steps S1-S3 to complete the inspection of the subsequent sections of steel cable.

[0013] Furthermore, in step S1, when wind disturbance causes the conventional attitude control to require a large tilt, tilt vector control is activated, and the body is kept in a horizontal attitude by adjusting the tilt angle of the power unit.

[0014] Furthermore, in step S4, before the machine body crosses the support tower, the locking of the clamping mechanism is released at a preset safe distance in front of the support tower and the machine body is raised vertically to a safe height. Then, it crosses the support tower and performs alignment and locking actions above the next section of steel cable.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: when inspecting the steel cable, the power unit can move the machine body to a position above the steel cable. After aligning the machine body with the steel cable, the clamping mechanism can work to indirectly connect the machine body with the steel cable. Then, the tilting mechanism can work to make the power unit flip and move, changing the power output direction, so that the machine body moves along the length of the steel cable.

[0016] In the process of using this invention to inspect steel cables, it has the advantage of rapid deployment, can quickly reach the high-altitude steel cable area and complete close inspection, and can quickly separate from the steel cable after completing the inspection of the designated section of steel cable. Furthermore, after crossing the support tower, it can quickly connect with the next section of steel cable, thus improving inspection efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the attitude of the power unit during the vertical take-off and landing process of the present invention; Figure 3 This is a schematic diagram of the dynamic unit's attitude during the alignment / vector control process of the present invention; Figure 4 This is a schematic diagram of the attitude of the power unit during the cable-driven propulsion process of the present invention; Figure 5 This is a schematic diagram of the power unit's attitude during the return process of the present invention; Figure 6 This is a schematic diagram of the operation process of crossing the support tower according to the present invention; Figure 7 This is a flowchart of the steel cableway inspection method according to an embodiment of the present invention; Among them, 1-body, 2-motor, 3-propeller, 4-binocular vision, 5-laser ranging and positioning module, 6-supporting leg, 7-clamp, 8-tilting mechanism, 9-hanger, 10-top limit plate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] See Figure 1 As shown, a tilt-powered multi-rotor UAV for inspecting cableways includes a body 1 with at least four power units connected to it. Each power unit includes a motor 2 and a propeller 3. The propeller 3 is mounted on the output shaft of the motor 2. When the motor 2 is working, it enables the propeller 3 to rotate. The body 1 is wirelessly connected to a controller, which enables the power units to operate, thereby moving the body 1 above the cableway. A clamping mechanism is also provided on the body 1, located below it, and can be coupled to the cableway. A magnetic detection load is provided on the clamping mechanism. By moving the body 1 along the length of the cableway, the magnetic detection load can detect the cableway.

[0021] Before connecting the clamping mechanism to the cableway, the drone body 1 needs to be positioned directly above the cableway. Therefore, a positioning and alignment module is installed on the drone body 1. The positioning and alignment module obtains the spatial position and direction of the cableway and can output alignment information to the controller. Based on the alignment information output by the positioning and alignment module, the operator controls the drone to achieve position / heading alignment during the alignment phase. Then, by controlling the power unit, the drone body 1 is moved downward. The positioning and alignment module includes a binocular vision module 4 and a laser ranging and positioning module 5. The binocular vision module 4 is used to extract the cable segment, direction vector and image plane position; while the laser ranging and positioning module 5 is used to obtain the distance to the cable or the height information of the nearby structure. Combined with the IMU (Inertial Measurement Unit) and the pose calculation of the body 1, the spatial straight line parameters of the cable in the body 1 frame or the geographic frame are obtained.

[0022] In this technical solution, a tripod limiting mechanism is also provided. The tripod limiting mechanism is installed on the machine body 1 and located below the machine body 1. By setting the tripod limiting mechanism, a docking area is formed below the machine body 1, and the clamping mechanism is located in the docking area.

[0023] The tripod limiting mechanism includes two support tripods 6, both of which are tilted outwards from the body 1, making the longitudinal cross-section of the docking area funnel-shaped. During the downward movement of the body 1, the support tripods 6 also play a guiding role. That is, when the steel cable comes into contact with the support tripods 6, as the body 1 gradually moves downwards, the body 1 will also undergo a certain lateral displacement due to the tilt angle of the support tripods 6, eventually allowing the steel cable to enter the docking area between the two support tripods 6. At this time, the two support tripods 6 can achieve a certain degree of limitation, preventing the body 1 from moving laterally over a large range.

[0024] Furthermore, an adjustment component is provided on the body 1. The adjustment component is connected to the support legs 6. The support legs 6 can be opened and closed by the operation of the adjustment component. When the opening is tightened, it is convenient to limit the position between the steel cable and the body 1. Conversely, when the two support legs 6 are opened to the maximum angle, they are convenient to form support and prevent tipping.

[0025] In this technical solution, the clamping mechanism has magnetic attraction and locking functions for fixing the UAV after it comes into contact with the steel cable. Specifically, it includes two clamping seats 7, which are symmetrically arranged. Each clamping seat 7 can be provided with a mating groove. When the two clamping seats 7 approach each other and finally dock, they form a clamping platform. This clamping platform can hold the steel cable. Each clamping seat 7 is provided with a magnetic attraction unit, which is a permanent magnet, an electromagnet, or a composite structure of a permanent magnet and an electromagnet. The magnetic attraction unit can connect the two clamping seats 7, thereby docking the two clamping seats 7 to form the clamping platform.

[0026] In this technical solution, a hanger 9 is installed on the body 1, with the opening of the hanger 9 facing downwards. A clamp 7 is located at the opening of the hanger 9. The clamp 7 is connected to the hanger 9 via an electric push rod with a limit function. The operation of the electric push rod allows the two clamps 7 to move closer or further apart. A top limiting plate 10 is installed inside the hanger 9. The hanger 9, the top limiting plate 10, and the two clamps 7 enclose a clamping area, and a steel cable can enter the clamping area. A contact detection component is installed on the top limiting plate 10, including force sensing, IMU impact characteristics, visual distance threshold, or clamp position. Switches, etc., allow the contact detection component to be positioned above the steel cable. As the body 1 moves downward, the steel cable passes between the two clamps 7. When the steel cable contacts the top limit plate 10, the electric push rod moves the two clamps 7 closer together, thereby closing the clamping platform. After closing, it can adhere tightly to the steel cable. To ensure the stability of the clamping platform, a mechanical locking structure and a magnetic attraction unit can also be set, such as a flip-out port or a sliding lock block. The mechanical locking structure and the magnetic attraction unit work together to form a lock, which can keep the two clamps 7 in a docked state. At this time, the two clamps 7 cannot be moved away from each other.

[0027] In this technical solution, when connecting with the steel cable, the following process can be followed: First, visual recognition and distance measurement are performed to determine the position and distance between the machine body 1 and the steel cable. Then, the machine body 1 is lowered and aligned with the steel cable. After the machine body 1 is lowered until the steel cable passes between the two clamps 7 and contacts the contact detection component, the two clamps 7 are brought closer to each other to achieve the connection between the clamp mechanism and the steel cable.

[0028] Meanwhile, an unlocking actuator is also provided between the two clamps 7. When the two clamps 7 need to be moved away from each other, the unlocking actuator contacts the mechanical locking structure, and then the electric push rod works to increase the distance between the two clamps 7. At this time, the drive unit can be controlled to work to drive the body 1 to move upward, thereby separating it from the steel cable.

[0029] In this technical solution, a tilting mechanism 8 is also provided, which connects the body 1 to the power unit. A servo drive component is provided on the body 1. The servo drive component can control the operation of the tilting mechanism 8. Thus, the controller can output a working signal to the servo drive component, and then the tilting mechanism 8 will rotate and move, thereby driving the power unit to move. In the specific implementation process, please refer to Figures 1 to 5 As shown, initially, the power unit outputs vertical lift after starting work, thereby moving the aircraft 1 upwards and positioning it above the steel cable. When encountering crosswind interference, the tilting mechanism 8 adjusts the tilting direction and angle of the power unit to maintain a stable state for the aircraft 1, and then moves the aircraft 1 downwards. After the aircraft 1 is connected to the steel cable through the clamping mechanism, the controller adjusts the operation of the tilting mechanism 8 to cause the power unit to rotate and move. After the power unit starts working, it can output horizontal thrust, thereby causing the aircraft 1 to move along the length of the steel cableway. After completing the inspection of the steel cable, the tilting mechanism 8 adjusts the attitude of the power unit, and finally, it can return to its starting position.

[0030] The controller in this technical solution is equipped with a tilt vector control module. When external wind disturbances cause a large tilt angle of the body 1 to be required to maintain position, the tilt angle of the power unit is adjusted so that the UAV can maintain the horizontal attitude or preset attitude of the body 1 while achieving position / heading control.

[0031] To enable the inspection of steel cableways, a magnetic detection load is installed on the clamping platform of the clamping mechanism. The magnetic detection load can be a magnetic flux leakage (MFL) sensor array, a Hall sensor array, or a magnetoresistive sensor array. In this case, the load can be arranged coaxially / nearly to the clamping structure, so that the detection area is consistent with the clamping area or has a fixed geometric offset, which is convenient for calibration. Thus, defects such as broken wires and corrosion in the steel cable can be detected by the magnetic detection load. The tilting mechanism 8 used in this technical solution is an existing technology structure, such as including a tilting module. The tilting module is an integrated structural unit that houses transmission components and necessary sensors. The tilting module is connected to the body 1 via a rotating shaft and is connected to a servo drive assembly. When the servo drive assembly is activated, it generates a linear push / pull force, which is applied to the tilting module, causing the entire tilting module to rotate, ultimately achieving the purpose of adjusting the attitude of the power unit.

[0032] See Figure 7 As shown, in this technical solution, the following steps are generally adopted when using a tilt-powered multi-rotor UAV to inspect a steel cableway: S1. Position the aircraft body 1 above the designated section of the steel cable, align the position of the steel cable with the aircraft body 1, and adjust the heading of the aircraft body 1, wherein the designated section is the part of the steel cable to be tested; S2. Move the machine body 1 downwards. When the steel cable is in the clamping area, activate the clamping mechanism to connect with the steel cable. S3. Adjust the attitude of the power unit so that the power unit can output thrust along the length of the steel cable, so that the body 1 and the magnetic detection load can move along the length of the steel cable. S4. After completing the inspection of the specified section of steel cable, tilt the power unit back to the vertical position, release the clamp lock and detach it from the steel cable, so that the machine body 1 crosses the support tower, and repeat steps S1-S3 to complete the inspection of the subsequent sections of steel cable.

[0033] As an example, see Figure 6 and Figure 7 As shown, during the inspection of the cableway by this UAV, in the alignment phase, the controller sets the desired heading according to the cable direction vector and uses the projection error of the cable centerline in the horizontal plane of the aircraft as the position control error.

[0034] Under normal operating conditions, alignment can be achieved using multi-rotor control with an outer position-velocity loop and an inner attitude loop. If strong winds occur during alignment, causing the conventional multi-rotor to tilt at a large angle to maintain its position, tilt vector control can be activated: by changing the tilt angle of each power unit, the resultant force vector satisfies the horizontal component required for position / velocity control, while constraining the airframe attitude to a horizontal or near-specified attitude, thus decoupling "position / heading control" from "airframe attitude maintenance".

[0035] Once the position and heading are aligned above the steel cable, the cable is slowly lowered along the normal direction of the cable (usually vertically downwards). During this process, the cable passes between the two clamps 7. When the contact detection component detects contact with the cable, the electric push rod starts working, bringing the two clamps 7 closer together and eventually forming a connection. At this time, the magnetic attraction unit is activated and cooperates with the mechanical locking structure to form a lock. After the lock is completed, the power output can be stopped (motor 2 stops or maintains a very low safe speed).

[0036] Because the clamping mechanism is heavier than the fuselage, and combined with the landing gear limiting mechanism, the overall center of gravity is positioned below the contact point between the clamping mechanism and the steel cable. This ensures that any attitude deviation generates a gravitational restoring torque, resulting in static stability. This design allows the UAV to maintain a horizontal position or within a preset attitude range even without attitude control or power shutdown.

[0037] After the clamping mechanism is connected to the steel cable, the controller tilts the power unit to output thrust along the direction of the steel cable, and then starts the power to move at a set speed. During this process, the magnetic detection load moves along the length of the steel cableway, thereby realizing the inspection along the cable. The magnetic detection load collects data synchronously and records the location of defects in combination with mileage / time stamp.

[0038] When the inspection reaches the predetermined position in front of the support tower, the power unit can be tilted back to a vertical position, the lift force is activated to resist gravity, and the clamp lock is released at the same time. After the clamp mechanism is released from the steel cable, the machine body 1 continues to be lifted upward, thereby crossing the support tower and reaching the top of the next section of steel cable to repeat the alignment-locking-cable inspection operation process.

[0039] After completing the unidirectional full-line inspection, the power unit can tilt to the rear and return at an economical cruising speed. The tower crossing procedure is the same as the aforementioned process.

[0040] The following section compares the method of using this tilt-powered multi-rotor UAV to inspect steel cables with the method of using existing cable-walking robots to inspect steel cables. Dimension Cable-walking robot Tilting-powered multi-rotor drones Coverage It needs to be deployed in sections, and it is difficult to cross obstacles (supports, towers). It can quickly cross obstacles. Deployment efficiency It requires the pre-installation of tracks or traction devices, which is time-consuming and inflexible. It's ready to use immediately, requires no additional infrastructure, and can be deployed quickly. Terrain adaptability It has limited adaptability to steep slopes, long spans, or complex cables. It is unaffected by terrain limitations and is suitable for rugged environments such as deep valleys, rivers, and mountains. artificial intervention The installation requires personnel to climb the tower, which poses a high safety risk. The entire process is operated remotely, avoiding high-altitude operations and ensuring personnel safety. The above comparison shows that using this tilt-powered multi-rotor UAV to inspect steel cables can greatly improve the efficiency of the inspection operation, while also enhancing the safety of the inspection operation.

[0041] Finally, it should be noted that this technical solution is an improvement on the existing multi-rotor UAV structure. Therefore, the basic functions of the existing multi-rotor UAV are also present in this technical solution. However, this technical solution does not improve these functions. Therefore, this technical solution will not elaborate on the existing technologies such as the remote control system, power output and control system of the multi-rotor UAV.

[0042] In addition, it should be noted that the magnetic detection payload in this technical solution is not a single device; it also integrates a data acquisition and processing module, which can digitize the sensor signals for preliminary processing and storage.

[0043] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tilt-powered multi-rotor unmanned aerial vehicle (UAV) for inspecting steel cableways, characterized in that, include: The body (1) is positioned above the steel cable; The clamping mechanism is connected to the body (1) and can be detachably connected to the steel cable and keep the body (1) above the steel cable. A magnetic detection load, mounted on a clamping mechanism, is coupled to a steel cable and is used to perform magnetic detection on a designated section of the steel cable, wherein the designated section is the part of the steel cable to be detected. A power unit is used to provide power for the movement of the body (1); The tilting mechanism (8) is connected between the power unit and the body (1). It can change the tilting angle of the power unit and thus adjust the power output direction.

2. The tilt-powered multi-rotor UAV for cableway inspection according to claim 1, characterized in that, The clamping mechanism includes two clamps (7), which can move closer to or further away from each other. Each clamp (7) is provided with a mating groove. When the steel cable is clamped by the two clamps (7), the steel cable is located in the mating groove.

3. The tilt-powered multi-rotor UAV for cableway inspection according to claim 1 or 2, characterized in that, The magnetic detection load is coaxially arranged with the clamping mechanism. When the clamping mechanism moves along the length of the steel cable for inspection, the detection position of the magnetic detection load corresponds to the posture of the body (1).

4. The tilt-powered multi-rotor UAV for cableway inspection according to claim 3, characterized in that, The magnetic detection load is a magnetic flux leakage sensor array, a Hall sensor array, or a magnetoresistive sensor array.

5. The tilt-powered multi-rotor UAV for cableway inspection according to claim 2, characterized in that, The clamping mechanism also includes a magnetic attraction unit, which can provide a normal attraction force to the steel cable.

6. The tilt-powered multi-rotor UAV for cableway inspection according to claim 5, characterized in that, A contact detection component is provided above the clamping mechanism. When the steel cable is coupled to the contact detection component, the clamping mechanism is activated.

7. The tilt-powered multi-rotor UAV for cableway inspection according to claim 1, characterized in that, The weight of the clamping mechanism is greater than the weight of the machine body (1). When the clamping mechanism is connected to the steel cable, the overall center of gravity is located below the steel cable.

8. A method for inspecting cableways, utilizing the tilt-powered multi-rotor UAV for cableway inspection as described in any one of claims 1 to 7, characterized in that, The method includes the following steps: S1. Position the aircraft (1) above the designated section of the steel cable and align the position of the steel cable with that of the aircraft (1), while adjusting the heading of the aircraft (1); S2. After the steel cable is aligned with the machine body (1), the machine body (1) is moved downward. When the steel cable is in the clamping area (8), the clamping mechanism is activated and connected to the steel cable through the clamping mechanism. S3. Adjust the attitude of the power unit so that the power unit can output thrust along the length of the steel cable, so that the body (1) and the magnetic detection load can move along the length of the steel cable and the steel cable can be detected by the magnetic detection load. S4. After completing the inspection of the specified section of steel cable, tilt the power unit back to the vertical position, release the clamp lock and detach from the steel cable, so that the machine body (1) crosses the support tower, and repeat steps S1-S3 to complete the inspection of the subsequent section of steel cable.

9. The inspection method for steel cableways according to claim 8, characterized in that, In step S1, when wind disturbance causes the conventional attitude control to require a large angle of tilt, tilt vector control is activated, and the body (1) is kept in a horizontal attitude by adjusting the tilt angle of the power unit.

10. The inspection method for steel cableways according to claim 8, characterized in that, In step S4, before the machine body (1) crosses the support tower, the locking of the clamping mechanism is released at a preset safe distance in front of the support tower and the machine body (1) is raised vertically to a safe height. Then, it crosses the support tower and performs alignment and locking actions above the next section of steel cable.

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