• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.1919-1925
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• 2001

Overhead cranes consist of trolley, girder, rope, objects, trolley motor, girder motor, and hoist motor. If objects are regarded as mass point, and the acceleration of hoisting motion for objects is neglected, analytical model of overhead cranes becomes a nonlinear model because the length of a rope changes. Equations of motion this model is derived of simultaneous differential equations fur motors and object. Positions of the model are controlled by optimal inputs which obtain from a nonlinear optimal control method. From the results of computer simulation, even if initial states of objects suing, it is founded that position of overhead cranes is controlled, and that swing of objects is suppressed.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.90-97
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• 2017

Overhead cranes are the most widely used and have been identified as one of the main causes of fatal accidents. Although structural, mechanical and electrical safety standards for overhead cranes have been established to some extent, ergonomic standards related to crane controllers are rarely established. As a result, many crane accidents are reported to be caused by operator's error. To investigate the actual use of crane controllers in the industrial field, we surveyed 82 overhead cranes in 15 workplace and interviewed workers operating them. This study has presented the ergonomic problems related to the crane controllers in the field. As a result of investigation, it was found that the direction control signs, the sign language, and the button layout on the pendant switches and remote controllers are not standardized, which can cause a human error. To reduce human errors in overhead crane operation, ergonomic standards for controllers should be reflected on the government legislation or standards.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.75-83
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• 2015

Objective: The aim of this study is to suggest the standard of the direction sign on the pendant switch of overhead cranes which can reduce human errors in control. Background: A great number of crane accidents occur in industries. One of the major causes of the accidents is the mistake in the control of cranes by confusing the orientation of crane movements. Nevertheless, three different direction sign styles, 'East, West, South, North (EWSN)', 'Forward, Backward, Left, Right (FBLR)', and arrows for four directions are used without standardization. Method: An overhead crane simulator was installed for a laboratory experiment. It could move along six directions by the control of a pendant switch. 90 participants were evenly assigned to the three different conditions of direction sign styles. The participants were asked to control the pendant switch according to the continuously appearing 16 direction signs on a monitor ahead. The participants were allowed to refer an orientation sign board on the ceiling representing correct movement directions of the overhead crane simulator. Results: The direction sign style, 'EWSN', showed statistically significant better performance in task completion time and number of errors than the other sign styles. The direction sign style, 'EWSN', adopting the cardinal direction system, made the participants clear in direction controls after customizing to the crane movements. However, the direction sign styles, 'FBLR' and the arrows adopting the relative direction system made conflicts in direction controls due to the egocentric view of human. Conclusion: The direction sign style, 'EWSN', is the most appropriate for the standardization of the direction sign on the pendant switch of overhead cranes. Application: The results of this study can be applied to the standardization of direction sign in the legal notification on the safety certifications of crane manufacturing.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.1
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• pp.71-85
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• 1994

Overhead cranes which carry heavy items in construction or production areas consist of structure and electric modules. More than 80% of breakdowns bring out of the electric module. As operators do not know all about cranes, it sometimes takes much time to repair the cranes. In order to resolve this problem, the expert system which can diagnose causes of faults and give instructions for repair to operators, has been developed. The scope of the paper is limited to the electric module. First of all, analyzing symptoms and causes, we have developed a rule base with the expert system shell, EXSYS. Furthermore, for the facility maintenance including repair instructions against the causes, the instruction data base was developed with FOXPRO. On the other hand, for the help of user's understanding the fault causes, the graphic animation module which shows malfunctioning component ports or motions in 3D was developed with the graphic software, TOPAS VGA.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.1
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• pp.110-125
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• 2007

Various different types of yard cranes are used in container terminals. Examples are rubber tired gantry cranes,rail mounted gantry cranes, overhead bridge cranes, dual rail-mounted gantry cranes, and automated stacking cranes. The kinematics and handling characteristics of these yard cranes are different from each other. Ttiis study analyses charactehstics of generic types of yard cranes which represent various yard cranes m practice Demg used in several types of block layouts, Considering specifications of yard cranes and block layouts, expected cycle times and variances of the cycle time are estimated for different handling activities.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3160-3172
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• 1996

A search algorithm for the collision free, time optimal transport path of overhead cranes has been proposed in this paper. The map for the working environment of overhead cranes was constructed in the form of three dimensional grid. The obstacle occupied region and unoccupied region of the map has been represented using the octree model. The best-first search method with a suitable estimation function was applied to select the knot points on the collision free transport path to the octree model. The optimization technique, minimizing the travel time required for transporting objects to the goal while subjected to the dynamic constraints of the crane system, was developed to find the smooth time optimal path in the form of cubic spline functions which interpolate the selected knot points. Several simulation results showed that the selected estimation function worked effectively insearching the knot points on the collision free transport path and that the resulting transport path was time optimal path while satisfying the dynamic constraints of the crane system.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1032-1039
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• 2011

This paper presents results of input shaping to industrial cranes. A brief theoretical background for input shaping is described. Several examples of input shaping application to sway regulation for industrial cranes are presented. The presented results show that input shaping is very useful for industrial cranes.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.582-590
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• 2007

Nonlinear adaptive control of overhead cranes is investigated for anti-sway trajectory tracking with high-speed hoisting motion. The sway dynamics of two dimensional underactuated overhead cranes is heavily coupled with the trolley acceleration, hoisting rope length, and the hoisting velocity which is an obstacle in the design of decoupling control based anti-sway trajectory tracking control law To cope with this obstacle. we propose a fuzzy nonlinear adaptive anti-sway trajectory tracking control law guaranteeing the uniform ultimate boundedness of the sway dynamics even in the presence of uncertainties in such a way that it cancels the effect of the trolley acceleration and hoisting velocity on the sway dynamics. In particular. system uncertainties, including system parameter uncertainty unmodelled dynamics, and external disturbances, are compensated in an adaptive manner by utilizing fuzzy uncertainty observers. Accordingly, the ultimate bound of the tracking errors and the sway angle decrease to zero when the fuzzy approximation errors decrease to zero. Finally, numerical simulations are performed to confirm the effectiveness of the proposed scheme.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1391-1401
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• 1995

This paper addresses design procedure and testing results of a closed-loop motion control of the cranes. When the object is stopped at the desired position, swinging occurs, and such swinging deteriorates the safety and efficiency of the operation of the crane. Therefore, in this paper, the cascade anti-swing and trolley position feedback controller are designed. Anti-swing controller rapidly eliminates swinging of object and position feedback controller reduces the trolley position error. The performance of this controller is investigated through the computer simulation and experiment. From the results of a series of computer simulations and experiments it can be concluded that proposed controller effectively reduces swinging of the object and trolley position error, which shows this controller can be used as an effective tool for the precise control of overhead cranes.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.717-724
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• 2013

Industrial cranes are indispensable equipment in heavy industry. However, unwanted vibrations in cranes often cause accidents. Input shaping is widely accepted as a useful tool for removing residual vibration in cranes. A unity magnitude zero vibration (UMZV) input shaper is often used for cranes driven by on-off-type motors. However, although a UMZV input shaper minimizes residual vibration, the input shaper cannot prevent the crane from moving slightly further than expected from the original command. This paper describes an improved method of input shaping that can compensate for position inaccuracies, as well as remove the residual vibration of cranes. Experiments were performed to validate the proposed input-shaping method, illustrated through numerical simulations.