• Journal of Korean Society for Quality Management
• /
• v.20 no.2
• /
• pp.137-142
• /
• 1992

MODAPTS has been widely used for establishing the standard time of manual works because of easy application of the system. However this system was developed based on MTM, winch was one of the low task standard. Also in this system, it usually becomes a cause of error in accuracy that all the simultaneous motions(SIMO) should be analyzed in the sequent motions of two hands. In order to improve the weak points of MODAPTS, the structure of time unit and SIMO of MODAPTS was researched, and HITMAP was developed on the basis of Work Factor System which was one of the high task standard. HITMAP is composed of 26 standard elements and it's time unit is MD(1MD=0.1 second) and MGSRMPS is the motion pattern of HITMAP. In this study HITMAP shows more than 95% of accuracy to WF. Therefor, it is expected that HITMAP can be used for the improvement of productivity and incentive systems.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.3
• /
• pp.685-699
• /
• 2014

In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-${\beta}$ method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.9
• /
• pp.88-95
• /
• 2009

Input shaping has been a very effective control method for reducing payload swing in industrial bridge and gantry cranes. However, conventional input shapers often degrade performance when applied to tower cranes because of the nonlinear coupled dynamics between rotational and radial motions in tower cranes. To alleviate this problem, a new input shaper for tower cranes is developed by means of dynamic modeling, analysis and optimization. This work investigates the tower crane dynamics along with parameters of the tower crane varied. A performance index for input shaper design is proposed so as to reduce the coupled residual vibration of a tower crane using only rotational motion of tower crane. The proposed new input shaper is verified to be effective through simulations and experiments.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.711-722
• /
• 2020

An optimization framework using genetic algorithms has been developed towards an automated parametric optimization of the Octabuoy semi-submersible design. Compared with deep draft production units, the design of the shallow draught Octabuoy semi-submersible provides a floating system with improved motion characteristics, being less susceptible to vortex induced motions in loop currents. The relatively large water plane area results in a decreased natural heave period, which locates the floater in the wave period range with more wave energy. Considering this, the hull design of Octabuoy semi-submersible has been optimized to improve the floater's motion performance. The optimization has been conducted with optimized parameters of the pontoon's rectangular cross section area, the cone shaped section's height and diameter. Through numerical evaluations of both the 1st-order and 2nd-order hydrodynamics, the optimization through genetic algorithms has been proven to provide improved hydrodynamic performance, in terms of heave and pitch motions. This work presents a meaningful framework as a reference in the process of floating system's design.

• Journal of the Korea Safety Management & Science
• /
• v.13 no.4
• /
• pp.25-33
• /
• 2011

Workers in logistics centers also are exposed to serious musculoskeletal disorders the same as workers in general manufacturing due to operating forklifts and other labor duties. The frequency of these work related injuries decreases, workers' job satisfaction In addition, it causes many employees questioning a job change, which is regarded as the primary factor which drops the productivity. In this paper, we conducted a survey ti perceive the correlation between work related injuries in the fields of distribution centers and job satisfaction. Furthermore we made statistical analysis with our findings. The results of our analysis showed that the frequency of work related injuries due to workers' repetitive loading and unloading work is the primary factor which lowers job satisfaction. In order to improve aforementioned problem we propose first of all loading and unloading on pallet basis, second of all automation and computerization of logistics systems, and third of all ensurinf sufficient break time.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10b
• /
• pp.382-387
• /
• 1992

In order to obtain desired arc welding performance, we already developed an arc welding robot system that enabled coordinated motions of dual arm robots. In this system one robot arm holds a welding target as a positioning device, and the other robot moves the welding torch. Concerning to such a dual arm robot system, the positioning accuracy of robots is one important problem, since nowadays conventional industrial robots unfortunately don't have enough absolute accuracy in position. In order to cope with this problem, our robot system employed teaching playback method, where absolute error are compensated by the operator's visual feedback. Due to this system, an ideal arc welding considering the posture of the welding target and the directions of the gravity has become possible. Another problem still remains, while we developed an original teaching method of the dual arm robots with coordinated motions. The problem is that manual teaching tasks are still tedious since they need fine movements with intensive attentions. Therefore, we developed a 3-dimensional vision guided robot control method for our welding robot system with coordinated motions. In this paper we show our 3-dimensional vision sensor to guide our arc welding robot system with coordinated motions. A sensing device is compactly designed and is mounted on the tip of the arc welding robot. The sensor detects the 3-dimensional shape of groove on the target work which needs to be weld. And the welding robot is controlled to trace the grooves with accuracy. The principle of the 3-dimensional measurement is depend on the slit-ray projection method. In order to realize a slit-ray projection method, two laser slit-ray projectors and one CCD TV camera are compactly mounted. Tactful image processing enabled 3-dimensional data processing without suffering from disturbance lights. The 3-dimensional information of the target groove is combined with the rough teaching data they are given by the operator in advance. Therefore, the teaching tasks are simplified

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.1197-1205
• /
• 1988

An analytical method to predict qualitative performance characteristics of the Stirling Engines in the preliminary design stages is investigated. Both the expansion and the compression cylinder are treated as adiabatic and piston motions are approximated as saw-toothed waves. Basic equations which were originally proposed by Finkelstein consist of mass conservation and energy balances for each adiabatic cylinder. The approximation on piston motions and physical conditions make it possible to divide an engine cycle into four fundamental processes. In each process, first, pressure can be expressed as a function of the crank angle by solving a nonlinear first order ordinary differential equation and other thermodynamic variables are determined in turn. Application of the cyclic steady condition to the whole processes can complete a cycle. Also, further analysis results in analytic expressions for cyclic work and heat transfer in terms of the engine parameters and thermodynamic variables at boundary points. The results are expected useful as a quick reference for the engine performances. Finally, the present method can be applied to the other adiabatic analyses on the Stirling Engines with piece wise linear piston motions, if mass variations are predictable.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.1
• /
• pp.22-37
• /
• 1995

Industrial robot has played a central role in the production automation such as welding, assembling, and painting. There has been, however, little effort to the application of robots in machining work(grinding, cutting, milling, etc.) which is typical 3D work. The machining automation requires a high stiffness robot arm to reduce deformation and vibration. Conventional articulated robots have serially connecting links from the base to the gripper. So, they have very weak structure for he machining work. Stewart Platform is a typical parallel robotic mechanism with a very high stiffness but it has a small work space and a large installation space. This research proposes a new machining robot arm with a double parallel mechanism. It is composed of two platforms and a central axis. The central axis will connect the motions between the first and the second platforms. Therefore, the robot has a large range of work space as well as a high stiffness. This paper will introduce the machining work using the robot and design the proposed robot arm.

• IE interfaces
• /
• v.14 no.1
• /
• pp.95-105
• /
• 2001

Previous work measurement methods need much time and effort of time study analysts because they have to measure required time through direct observations. In this study, we propose a method which efficiently measures standard times without involvement of human analysts using digital image processing techniques. This method consists of two main steps: motion representation step and cycle segmentation step. In motion representation step, we first detect the motion of any object distinct from its background by differencing two consecutive images separated by a constant time interval. The images thus obtained then pass through an edge detector filter. Finally, the mean values of coordinates of significant pixels of the edge image are obtained. Through these processes, the motions of the observed worker are represented by two time series data of worker location in horizontal and vertical axes. In the second step, called the cycle segmentation step, we extract the frames which have maximum or minimum coordinates in one cycle and store them in a stack, and calculate each cycle time using these frames. In this step we also consider methods on how to detect work delays due to unexpected events such as operator's escapement from the work area, or interruptions. To condude, the experimental results show that the proposed method is very cost-effective and useful for measuring time standards for various work environment.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.32 no.10
• /
• pp.1571-1583
• /
• 2008

The study aimed to investigate the actual condition of working clothes in the Changwon National Industrial Complex and to analyze the industrial workers' satisfaction with and preference to the working clothes in terms of the clothing performance and work motion factors. 1 major companies in machinery, automotive, industrial engineering, shipbuilding and rolling stock industries located in the industrial complex were selected as the subject firms. Approximately 900 workers responded to the questionnaire designed for the research and the results derived from the research were as follows. (1) The subject employees were divided into 4 work groups, i.e. the $1^{st}$ work group: managerial, general affairs, sales, production planning; the $2^{nd}$ group: quality assurance, material planning and distribution, product inspection; the $3^{rd}$ group: electric, facilities, machinery, vehicles; and the $4^{th}$ group: cutting, pressing, rolling, welding and coating. (2) The significant work environmental factors considered by all work groups were air ventilation, noise and dust factors and in particular, the most dissatisfied factors evaluated by manufacture workers were insulation, noise, dust and vibration. (3) According to the employees' work motion evaluation, the work motion diversity and frequency increased in proportion to the degree of work intensity. Besides, manufacture workers more frequently wore the working clothes even during the off-duty hours comparing to the evaluation of the other work groups. (4) The most important clothing performance factors considered by manufacture work groups were perspiration absorption, stretch, air permeability, tactile sense softness, soil proof in order.