• Safety and Health at Work
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• v.6 no.4
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• pp.279-288
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• 2015

Background: In this study, the measurement of job stress of electric overhead traveling crane operators and quantification of the effects of operator and workplace characteristics on job stress were assessed. Methods: Job stress was measured on five subscales: employee empowerment, role overload, role ambiguity, rule violation, and job hazard. The characteristics of the operators that were studied were age, experience, body weight, and body height. The workplace characteristics considered were hours of exposure, cabin type, cabin feature, and crane height. The proposed methodology included administration of a questionnaire survey to 76 electric overhead traveling crane operators followed by analysis using analysis of variance and a classification and regression tree. Results: The key findings were: (1) the five subscales can be used to measure job stress; (2) employee empowerment was the most significant factor followed by the role overload; (3) workplace characteristics contributed more towards job stress than operator's characteristics; and (4) of the workplace characteristics, crane height was the major contributor. Conclusion: The issues related to crane height and cabin feature can be fixed by providing engineering or foolproof solutions than relying on interventions related to the demographic factors.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1428-1431
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• 1996

This paper proposes an anti-swing control law for a 2 degrees of freedom overhead crane. The dynamic model of a 2 degrees of freedom crane is highly nonlinear and coupled. The model is linearized and decoupled for each degree of freedom of the crane for small motions of the load about the vertical. Then a decoupled anti-swing control law is designed for each degree of freedom of the crane based on the linearized model. The control law consists of a position control loop and an swing angle control loop. The position loop,. is designed based on the loop shaping method and the swing angle loop is designed via the root locus method. Finally, the proposed anti-swing control law is implemented and evaluated on a 2 degrees of freedom prototype crane.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2240-2245
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• 2003

In this paper, the controller design by coefficient diagram method (CDM) for controlling the trolley position, load-swing angle and hoisting rope length of the overhead crane system simultaneously is proposed. The overhead crane system is a MIMO system consisting of two inputs and three outputs. Its mathematical model is nonlinear with coupling characteristics. This nonlinear model can be approximated to obtain a linear model where the first input mainly affects the trolley position and the load-swing angle while the second input mainly affects the hoisting rope length. In order to utilize the CDM concept for assigning the controllers, namely PID, PD and PI controllers separately, the model is approximated to be three transfer functions in accordance with trolley position, the load-swing angle and the hoisting rope length controls respectively. The satisfied performances of the overhead crane system controlled by the these controllers and fast rejection of the disturbance effect occurred at the trolley position are shown by simulation and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.225-225
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• 2000

We propose the hybrid robust controller for TDC(Time Delay Control) and SMC(Sliding Mode Control) method. TDC and SMC deal with the time-varying system parameters, unknown dynamics and unexpected disturbance. This controller is applied to follow the desired reference model for the uncertain time-varying overhead crane. The control performance is evaluated through simulation. The theoretical results indicate That the proposed controller shows excellent performance to an overhead crane with the uncertain time-varying parameters and disturbance.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.181-188
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• 2000

Input shaping is a method fur reducing residual vibration. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with the desired system command. It has been applied to robot with a flexible manipulator. But it can be applied to the reduction of residual vibration far overhead crane. In this paper, input shaping shows good performance for anti-sway of overhead crane. In the z-domain, we designed an input shaper and calculated the sensitivity of it. If sensitivity is calculated in the z-domain, the shapes of sensitivity curves are expected easily. Accordingly, it is easy to design an input shaper in the z-domain. We compared the response of a system with shaper to it without that. Also, we compared El shaper to ZV shaper in view of robustness.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.160-167
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• 2004

The correlation between the object function and the design parameter is shown on this paper by using the characteristic function for the mixed result of the structural analysis, the buckling analysis and the table of orthogonal array according to the original overhead crane's dimensional change. About the above two functions, the effectiveness of design change according to the change of design parameters could be estimated. Also, the overhead crane's weight is reduced up to 10.55 percent maintaining the structural stability according to the thickness of plate.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.12-17
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• 2006

This study uses a characteristic function to explain correlations between the objective function and design variables. For the use, structural analysis and buckling analysis are carried out. the dimensional change of an original overhead crane is made based on the table of orthogonal array. For two functions or more, the effectiveness of design change can be evaluated in accordance with change in design parameters. Also, the overhead crane's weight is reduced by up to 10.55 percent while its structural stability maintained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1468-1474
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• 2001

In this paper, a new fuzzy-logic anti-swing control scheme is proposed for a three-dimensional overhead crane. The proposed control consists of a position servo control and a fuzzy-logic control. The position servo control is used to control the trolley position and rope length, and the fuzzy-logic control is used to suppress load swing. The proposed control guarantees not only prompt suppression of load swing but also accurate control of trolley position and rope length for the simultaneous travel, traverse, and hoisting motions of the crane. The effectiveness of the proposed control is shown by experiments with a prototype three-dimensional overhead crane.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.9-16
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• 2010

This paper presents supervisor control methods at a matrix converter controlled overhead crane system based on a controller area network (CAN). Four induction motors are used to drive the gantry, trolley, and hoist at he crane and each motor is controlled by the matrix converter with direct torque control (DTC). Both the position control algorithm and the supervisor control system using CAN are introduced. Simulation and experimental results are carried out to verify the performance of position control at the matrix converter controlled crane system.