• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.1014-1017
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• 1988

Direct-drive robots have excellent features including no backlash, small friction, and high mechanical stiffness. However, dynamic coupling among joints as well as nonlinear effects become more prominent than traditional robots with reducers. Another critical issue is that the robot becomes more sensitive to the change of load. In this paper, we develop a simple current feedback scheme for reducing the influence of dynamic coupling and load sensitivity on the direct-drive robots. The method is implemented on a 2 d.o.f. planar direct-drive robot. Then the validity of the method is demonstrated through experiments.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1789-1794
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• 2004

The present study investigates flow characteristics in an optical disc drive. Detailed knowledge of the flow characteristics is essential to analyze flow-induced noise and vibration, forced convection and flow friction loss. The ODD used in the personal computer is used for the experiment and rotating velocity of disc is under the 4500 rpm. Time-resolved velocity components and velocity spectrum are obtained using the laser Doppler anemometry (LDA). The results show that the front holes reduce now-induced noise and the position of pickup body affects flow near the window. In addition, il is possible for cooling of heat sources in an optical disc drive through measuring the flow fields under the tray.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1384-1389
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• 2004

In these days, wear resistance is an essential condition because the relative movement between machine parts is being accelerated and those connected with the drive parts transmit power and force. Also wear resistance is closely related to reliability and life of products, therefore the study on friction and wear is very important in many fields. In this paper, wear test was conducted to know properties about friction and wear of manganese phosphate being used widely. Test type is 1 ball on disk and we compared manganese phosphate thin film with non-coated material. Through this study, we could know the effect of this surface treatment method, and then it is assumed that the reliability of parts will be secure.

• Tribology and Lubricants
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• v.29 no.1
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• pp.1-6
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• 2013

Hydraulic transmission is the main component delivering power to the drive wheels of an excavator during forward and backward movement, and it has low speed, high torque and high speed, low torque gear change ratios as a forward/backward two-speed main function. It also has additional function of ensuring that the excavator is stably fixed on the ground with the built-in parking brake during excavation operations. In this study, optimal design specifications are determined by modeling and simulating about the multi-disc-type friction clutch, which is the main component improving the reliability of the hydraulic transmission for a 14-ton wheel excavator, and the friction properties of the transmission clutch are analyzed by performing sample tests.

• Journal of Drive and Control
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• v.9 no.1
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• pp.18-24
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• 2012

The paper deals with the design of a new low-friction seal for a pneumatic cylinder with high speed actuation. The seal performance with variation of the cross sections in piston seals with elastomeric material was investigated to minimize the friction forces using ABAQUS. The contact stress and strain distributions and frictional forces of the piston seals were investigated with variation of interference fits, supply pressures and friction coefficients. To develop adequate and productive procedures, the finite element models of the piston seals were created and nonlinear analysis of a seal design was conducted in order to build further knowledge and understanding of the seal's performance characteristics.

• Journal of Drive and Control
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• v.9 no.4
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• pp.26-31
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• 2012

Friction reduction between sliding hydraulic machine components is required to improve efficiency and reliability of hydraulic machineries. It is recently reported that surface texturing on sliding bearing surfaces can reduce the friction force highly. In this paper, numerical analysis is carried out to investigate the effect of dimple numbers and inlet boundary pressures on the lubrication characteristics of a parallel sliding bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. The results show that the pressure distribution, load capacity, dimensionless friction force and leakage with dimple number and their locations, and inlet pressures. The overall lubrication characteristics are highly affected by dimple numbers and boundary pressure. The numerical method adopted and results can be used in design of efficient hydraulic machine components.

• Journal of the Korea Computer Industry Society
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• v.7 no.3
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• pp.155-162
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• 2006

Because of their lower cost, higher speed, and longer travel, a belt drive system are quite desirable over screw driven system. However, a belt drive system are inherently difficult to control due to belt flexibility, friction, vibration, backlash and other non-linearities. This thesis presents servo control algorithm and the designing method of controller appliable to a belt drive system. In this paper, a LQ servo controller for a belt drive system is proposed to accomplish an optimal design of improved control system. In this scheme a mathematical model for the control system is obtained in state space form. Finally, the effectiveness of the proposed servo controller was verified through the computer simulation results.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.4
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• Transactions of the Society of Information Storage Systems
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• v.5 no.2
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• pp.96-101
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• 2009

In recent years, the demand for portable digital devices such as cellular phone, digital camera, and MP3 player has been largely increased. To meet the requirements of such portable applications the information storage devices with smaller size, higher capacity, and lower power consumption are needed. A small form factor (SFF) HDD using a load/unload (L/UL) system is one of the appropriate alternatives to satisfy these requirements. Due to complexity of L/UL process and mechanism, it is required to investigate for better understanding the effects of design parameters. Among the various design parameters, flexible cable and friction force on the L/UL ramp become important to the dynamic characteristics of L/UL process as the system is miniaturized. The program for L/UL simulation which considers the effect of flexible cable and L/UL ramp is needed. Unfortunately, there is hardly any commercial program for the L/UL simulation except the Computer Mechanics Laboratory (CML) air bearing design program and the CML L/UL simulation code. Furthermore, the design parameters such as flexible cable and the L/UL ramp are not considered in the CML L/UL simulation code. So we embody the L/UL simulation considering flexible cable and an L/UL ramp by using the ANSYS/LS-DYNA. In this thesis, the effects of flexible cable and friction force on the dynamic characteristics and the performances of the L/UL process are studied. Numerical simulation and related experiments are carried out and compared each other.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.199-206
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• 2016

Linear motion (LM) ball guides with rolling contact are core units of feed-drive systems. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, the friction force induced from LM ball guides generates heat, which deteriorates positioning accuracy and incurs changes of stiffness and preload. To accurately analyze the effects and apply the results to precision machine design, mathematical modeling of the friction force is required. In this paper, accurate formulation of the friction force due to rolling, viscous, and slip frictions is conducted for LM ball guides. To verify the reliability of the developed friction model, experiments are performed under various assembly, load and velocity conditions. Effects of frictional components are analyzed through the formulated friction model.