• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.375-380
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• 2011

Loading/unloading at sea is necessitated as larger container ships are being used. It is also unavoidable to load/unload at sea during military operations. An experimental cable array robot system, which can be used for loading/unloading at sea, consisting of four cables operated by four motors is designed and built. Even though it has simple structure, it has a large pay-load/robot-weight ratio, flexibility and wide workspace and can be easily built at low cost. In order to plan and control the paths of end-effector, two interpolation methods are introduced and compared. Since the robot is entirely based on cable tension, an analysis of tension is also presented for monitoring and planning purpose.

• Structural Monitoring and Maintenance
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• v.11 no.2
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• pp.127-148
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• 2024

Estimating cable tension is important in the maintenance of cable structures, such as cable-stayed bridges. In practice, the higher-order vibration method based on natural frequencies is used. In recent years, dampers have been installed onto cables to suppress aerodynamic vibration. Because the higher-order vibration method is suitable to cables without a damper, the damper must be removed before using this method. Because damper removal is time-consuming and labor-intensive, a previous study proposed a tension estimation method for a cable with a damper based on the natural frequencies, which does not require the damper's removal. However, the previous method relies on the modeling accuracy of the damper's complex stiffness. The damper design formula, while intended for design purposes, does not consistently reflect the damper's actual complex stiffness. Therefore, the estimation accuracy deteriorates when the damper's actual complex stiffness deviates from the damper design formula. With this background, this paper introduces a novel tension estimation method based on mode shapes, which circumvents damper modeling errors since mode shapes are independent of the damper's complex stiffness. In the numerical verification using 90 models, the proposed method estimated tension accurately with an estimation error within 0.59%. In the experimental verification, the proposed method estimated tension accurately with an estimation error within 4.17% except for one case, while the previous method had an estimation error of 44% when the damper design formula was used. The proposed method was found to be superior to the previous method in terms of accuracy and practicality by numerical simulation and experiment.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.455-457
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• 2007

The objective of this study is development of a installed working robot for a troy cable with mobile and tension system. In this paper, an approach to designing controllers for dynamic hybrid Tension/Mobile control of a installed robot for a troy wire cable is presented. Mobile control system of robot is designed based on equation of dc motor and motion for moving robot and tension control system is designed based on equation of ac servomotor for generating torque and dynamic equation of a wire cable. The control parameters is determined by simulation in independence operation of two system.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.982-996
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• 2016

In this paper, new tethered aerial robots including roaming tethered aerial robots (RTARs) for radioactive material sampling and stationary tethered aerial robots (STARs) for environment monitoring are proposed to meet extremely-long-endurance missions of nuclear power plants. The flight of the proposed tethered aerial robots may last for a few days or even a few months as long as the tethered cable provides continuous power. A high voltage AC or DC power system was newly adopted to reduce the mass of the tethered cable. The RTAR uses a tethered cable spooled from the aerial robot and an aerial tension control system. The aerial tension control system provides the appropriate tension to the tethered cable, which is accordingly laid down on the ground as the RTAR roams. The STAR includes a tethered cable spooled from the ground and a ground tension control system, which enables the STAR to reach high altitudes. Prototypes of the RTAR and STAR were designed and successfully demonstrated in outdoor environments, where the load power, power type, operating frequency, and flight attitude of the RTAR and STAR were: 180 W, AC 100 kHz, and 20 m; and 300 W, AC or DC 100 kHz, and 80 m, respectively.

• Journal of the Institute of Convergence Signal Processing
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• v.1 no.2
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• pp.153-159
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• 2000

The cable installed will have catenary's type that is nonlinear and variable time system. Because it has a close relation to the catenary's type to determine command value of tension for the tension control of this cable, we need to study it. The purpose of this study is automated the installation equipment (or a catenary's cable. This study shows control system that the tension of a catenary's cable is keep constant. 'rho control method is adopted the fuzzy control that is robust because the model of a control object is nonlinear and variable time system and feed-forward control to suppress overshoot as a shift begins to move. On the basis of the dynamic modeling of a catenary's cable we compose the control system with adopting fuzzy and feed-forward control has recognized the effectiveness in simulation results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.255-266
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• 2012

Main cable of a suspension bridge is the important member which shows the overall structure integrity at bridge completion. Configuration of main cable is a free hanging state at cable erection completion and is different from that at bridge completion supporting the dead loads such as hanger, girder, and so on. Accordingly, the configuration control under cable erection is considerably significant because the configuration at cable erection completion has direct influence on that at bridge completion. That is performed by sag adjustments at center, side span and tension adjustments at anchor span. The former needs the sag sensitivity which represents the control quantity of strand length corresponding to that of sag. The latter requires the tension sensitivity which shows the change of strand tension according to that of strand temperature. In this study, the fundamental equations of cable were derived with the assumption of either catenary or parabola shape, the differential-related equations using chain rule on horizontal tension were drawn from those and finally the estimation methods of the sag / tension sensitivity were proposed from both those. The nonlinear numerical analysis flow charts of sag sensitivity based on the catenary equations were proposed and the sag sensitivities grounded on the differential-related equations were compared with the results using them for various parameters of sag change. Also, considering the combinations of sag change parameters, the calculation method of the final variation for the cable sag was suggested. For the real suspension bridge under construction with PPWS method, the sag/tension sensitivity were estimated considering the construction conditions like the change of PPWS length, PPWS temperature, bridge span, etc.. We hope that this study will be a systematic guideline for the configuration control under main cable erection and improved highly by field verification in the real bridge site.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.161-166
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• 2002

Low-tension cables have been increasingly used in recent years due to deep-sea developments and the advent of synthetic cables. In the case of low-tension cables, large displacements may happen due to relatively small restoring forces of tension and thus the effects of fluid and geometric non-linearities become predominant. In this study, three-dimensional (3-D) dynamic behavior of a towed low-tension cable with non-uniform characteristics is numerically analyzed by considering fluid and geometric non-linearities and bending stiffness. A Fortran program is developed by employing a finite difference method. In the algorithm, an implicit time integration and Newton-Raphson iteration are adopted. For the calculation of huge size of matrices, block tri-diagonal matrix method is applied, which is much faster than the well-known Gauss-Jordan method in two point boundary value problems. Some case studies are carried out and the results of numerical simulations are compared with a in-house program of WHOI Cable with good agreements.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.353-358
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• 1999

Tabulated results by Pode are used for computing the cable shape and cable tension in static equilibrium. This paper describes a technique using the integral form by Pode to give a simplified calculation of the cable functions at any desired value because in most practical cased the points of interest on the cable are not the points of reference on which the tables are based. Solving the nondimentional tension, $\tau$, defined by Pode in closed form reduces the integral in cable functions to a single integral. The technique using the integral form enables us to calculate the cable functionsin at any critical angle and at any point in case of a towing cable or certain cable-buoy systems.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.727-736
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• 2005

This study presents a method of determining the optimum cable tension forces for the proper initial equilibrium state of a cable-stayed bridge using the least square method. The proposed method minimizes the errors, i.e., the differences, such as the deflection and the moments of the girder and the tower, between the target values from a continuous beam by considering the cable anchor point as supports of the girder and the responses obtained from the analysis of the entire cable-stayed bridge system. Especially, the proposed method can selectively control the adjustment of the tower moment, the girder moment, and the deflections by introducing the weighing matrix. Through numerical analysis and comparisons with existing studies, the usefulness and validity of the proposed method was verified.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.609-616
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• 2008

Recently, many ocean bridges that connect land to island or island to island have been constructed along with the improvement of the nation's economy. Long-span bridges can be categorized as suspension bridge, cable-stayed bridge, arch bridge and truss bridge. In this study, correction with respect to construction error can be presented on site through the monitoring of the cable tension change of real structure for four major construction stages so that construction accuracy, including the management of profiles, can be improved. A vibration method, the so-called indirect method that uses the cable's natural frequency changes from the acceleration sensor installed on the cable, is applied in measuring cable tension. In this study, the estimation formula for the effective length of cable with damper is presented by comparing and analyzing between actual measurement and analysis result for the change of the cable's effective length. By the way, it is known that the reliability of estimating cable tension by applying the former method that uses the net distance from damper to anchorage is low. Therefore, for future reference of the maintenance stage, the presented formula for estimating the effective length of cable can be used as a reference for the rational decision-making, such as the re-tensioning and replacement of cable.