• Journal of the Korean Society for Precision Engineering
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• v.33 no.1
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• pp.31-35
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• 2016

For reaction injection molding (RIM) polyurethane was mixed in the mixing head by impingement mixing, injected into the mold, and cured quickly, as soon as the mold is filled. The shape of the nozzle in the mixing head is critical to improve the quality of polyurethane. To achieve homogeneous mixing, an intensive turbulence energy in the mixing nozzle is essential. In this study, a mixing nozzle for RIM was designed, and mixing efficiency was investigated based on experiment. Experiments were conducted with different combinations of nozzle tips and exit diameter to measure the mixing efficiency by measuring jet force and investigating mixing image with high speed camera. Jet force increased gradually and reaches steady state conditions. The jet force depended on shape of nozzle tip and outlet sizes. These results suggest that optimized nozzle configurations are necessary for high efficiency mixing with RIM.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.1
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• pp.9-16
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• 2015

The machining-chatter stands for a sudden relative vibration appeared between a material and a tool while processing with a machine. This chatter is key factor that seriously affects the quality of processed materials as well as being a factor which causes serious damages to the tool and the machine. This study is related to the monitoring and smart control of chatter problem that can compensate machining-chatter faster and produce processed goods with more precision by autonomous compensation. The above-mentioned machining-chatter compensator includes the chatter vibration sensor and the chatter compensator that estimates the compensation value according to the sensor detecting the chatter vibration of machine-tool and the chatter vibration detected from the sensor while having a feature of being organized by interlocking with the machine-tool controller.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.97-103
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• 2013

This paper describes the characteristics of Electronic Throttle Controller (ETC) module in BLDC motor without the hall sensor for detecting a rotor position. The proposed ETC control system, which is mainly consisted of a BLDC motor, a throttle plate, a return spring and reduction gear, has a position sensor with an analogue voltage output on the throttle valve instead of BLDC motor for detecting the rotor position. So the additional commutation information is necessarily needed to control the ETC module. For this, the estimation method is applied. In order to improve and obtain the high resolution for the position control, it is generally needed to change the gear ratio of the module or the electrical switching method etc. In this paper, the 3-phase switching between successive commutations is adapted instead of the 2-phase switching that is conventionally used. In addition, the position control with a variable PI gain is applied to improve a dynamic response during a transient period and reduce vibration at a stop in case of matching position reference. The mentioned method can be used to estimate the commutation state and operate the high-precision position control for the ETC module and the high response characteristics. The validity of the proposed method is examined through the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.185-189
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• 2009

It is very important to control the vibration transmitted from external utilities and the transient response due to the internal sources for the precision equipment, which is very sensitive to the vibration environment. The anti-vibration tables that use air springs have been widely used due to their excellent isolation performance, but the systems with high flexibility have the critical problem of large transient response by the impulsive force of the moving mass in operation of the equipment. In this paper, the hybrid vibration control system is proposed, which is combined the air springs with the semi-active MR dampers in order to satisfy the performances of isolation and vibration reduction simutaneously.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2535-2539
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• 2003

The haptic system becomes an essential device in the area of tele-operation, video entertainment and medical operation. To control a haptic device, impedance control method is widely used, but force sensor costs so much that open-loop control method is usually preferred for commercial purpose. In this case, modeled/un-modeled dynamics affects the performance of device. In this paper, we present a new 3DOF five-link type haptic device that we can reduce the effect of device dynamics and compensate its dynamics. We also evaluate its performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.38-45
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• 2006

This paper presents load torque observer that is used to deadbeat control method in the induction motor(IM) precision position control system. The proposed algorithm shows robustness on induction servo motor system. All of the gain has been obtained on discrete domain analysis. The simulation has been obtained by the simulink. The results show that proposed system has good effectiveness for the disturbance of the induction servo motor system using DS1102 board.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1961-1965
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• 1991

This paper deals with an automatic and precision alignment technique for proximity printing in x-ray lithography, using two pairs of moire gratings, with moire signals from each pair being 180.deg. out of phase with each other. We constructed an automatic and precision alignment experimental system which could measure both transmitted moire signals and reflected moire signals at the same time. The automatic alignment was achieved using transmitted moire signals and also reflected moire signals as a control signal for a stage driver. The alignment position of the system was monitored not only by a control signal but also by a non-control signal. The effect of transmitted and reflected moire signals upon alignment accuracy was discussed. We concluded that the technique using diffracted moire signals is a viable automatic and precision alignment technique.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.231-236
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• 1993

To disign and build a ultra-precision laboratory which has been required for high technology in many areas, the environmental parameters such as temperature, humidity,vibration and nosic are controlled precisely. To absorb the outside vibration, particular concrete blocks were designed and set under the laboratory. The inside room temperature were controlled in local area within .+-. 0.3 .deg. c. It was efficient to induce laminar flow in air conditioning system for the control of room temperature, humidity etc. The control conditions should be determined according to their specific purposes. Also, the control method will be different for their respective environmental conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1784-1787
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• 2005

In this paper, proportional modulator which controls the second pressure of the pneumatic system was studied and proportional operating of modulator was gotten by two digital valves that have a fast dynamic characteristics and were controlled by PWM operating method. In order to more precision pressure control, this modulator consist of not only high speed two digital valves but also pressure sensor, measurement equipment and controller having a microprocessing function. In this study, for the development of the new proportional modulator, various research such as PWM control method, test equipment manufacturing, testing and evaluation were accomplished.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.43-53
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• 2002

Polishing a die that has free-form surfaces is a time-consuming and tedious job, and requires a considerable amount of high-precision skill. In order to reduce the polishing time and cope with the shortage of skilled workers, a user-friendly automatic polishing system was developed. The polishing system is composed of two subsystems, a three-axis machining center and a two-axis polishing robot. The system has five degrees of freedom and is able to keep the polishing tool in a position normal to the die surface during operation. A sliding mode control algorithm with velocity compensation was proposed to reduce tracking errors. Trajectory tracking experiments showed that the tracking error can be reduced prominently by the proposed sliding mode control compared to a PD (proportional derivative) control. To evaluate the polishing performance of the polishing system and to and the optimal polishing conditions, the polishing experiments were conducted.