• Journal of Welding and Joining
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• v.31 no.3
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• pp.39-43
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• 2013

It is difficult to feed welding wire stably, when the distance between welding wire feeder and welding torch is far enough. In order to solve this problem, arranging a extension wire feeder between them could be one of useful methods. However, the welding wire could be twisted up in the extension cable between extension and terminal wire feeders in the case that RPM of extension wire feeding motor is higher than that of terminal motor. In this study, feeding problem of normal push-pull wire feeding system occurred at low welding current range less than 250A. In order to solve the problem, two new wire feeding systems of push-pull type were introduced. Welding wire feeding tests were preformed in the range of 150A to 400A with the developed push-pull feeding system. In addition, weldability test was performed at the welding current of 200A, 300A, and 400A. The welding wire twisting problem that was observed in the normal feeding system did not occur in the new push-pull wire feeding system.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.1-8
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• 2011

This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2334-2340
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• 2010

Sun position computed by Michalsky shows maximum $1.5^{\circ}$, $0.88^{\circ}$ and 2 minutes differences in azimuth, altitude, and sunrise and sunset times respectively compared with Korean Almanac. The 2-axis solar tracking system, which consist control panel with ATmega128 CPU, BLDC motor-cylinder actuator and 2-axis link mechanism, was developed. Computed azimuth and altitude of sun for a current time, and latitude and longitude of tracker position built are controlled in real time by BLDC motor-cylinder actuators comparing with the position feed-backed by Hall sensor. The use of BLDC motor is free in maintenance. Implementation of a home-return function by Hall sensor is to minimize the cumulative error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1054-1058
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• 1995

There have been many research works for the indirect cutting force measurement in machining process, which deal with the case of one-axis cutting process. In multi-axis cutting process, the main difficulties to estimate the cutting forces occur when the feed direction is reversed. This paper presents the indirect cutting force measurement method in contour NC milling processes by using current signals of servo motors. An artificial neural network (ANN) system are suggested. An artificial neural network(ANN) system is also implemented with a training set of experimental cutting data to measure cutting force indirectly. The input variables of the ANN system are the motor currents and the feedrates of x and y-axis servo motors, and output variable is the cutting force of each axis. A series of experimental works on the circular interpolated contour milling process with the path of a complete circle has been performed. It is concluded that by comparing the ANN system with a dynamometer measuring cutting force directil, the ANN system has a good performance.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.27-34
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• 2018

In this study, the generating of torque regarding the Control Moment Gyro (CMG) is proportional to the angular velocity of gimbal. This is the case because gimbal affects the attitude control of the satellite directly, and it is necessary to reduce the incidence of torque ripple of gimbal. In this paper, the cause of the torque ripple of gimbal is reviewed and mathematically modeled by assuming the friction imbalance of bearing, the magnetic field and the phase current imbalance of the motor. We are able to confidently estimate the modeling parameters of gimbal disturbance using a constant speed test, and then analyze the influence of applying feedforward control to our modeling. Additionally, the simulation results show that the torque ripple and angular velocity fluctuations are reduced when apply this modeling to the identified study parameters. Finally, we present the disturbance reduction technique using our disturbance modeling.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.553-562
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• 2012

Computational Fluid Dynamics (CFD) analysis has been performed to estimate the air temperature inside an Auxiliary Feed Water (AFW) Motor-Driven (MD) pump room for the case where there is loss of Heating, Ventilation, and Air-Conditioning (HVAC). A transient calculation for the closed pump room without cooling by any HVAC system shows that the volume-averaged air temperature reaches around $60^{\circ}C$ for a transient period of 8.0 h. From previous studies, the external air and surface boundary temperatures are assumed to increase slowly starting from an initial temperature of $35^{\circ}C$. For the cases where the door is opened at 2, 4, and 6 h after the initiation of HVAC failure, the average air temperature promptly drops by about $4^{\circ}C$ when the door is opened and then slowly increases. The current calculations based on the CFD technique predict the rate of increase of air temperature to be lower than that determined by previous conservative calculations on the basis of a lumped model.