• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.3
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• pp.80-87
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• 1995

In this paper, we design the microcontroller-based optimal lead angle control system on the basis of the presented maximum average torque formula of the permanent-type stepping motor with respect to the inductance. We confirm that optimal lead angle enlarges the operating range twice as much and increases the torque over all of the operating range in the case of presented formula as well as experimental results.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.399-400
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• 2020

본 논문은 Sensored BLDC 모터의 제어방법을 설명하고, 효율적인 최적 제어를 하기위해 Lead Angle 제어를 하는 방법에 대하여 설명하였다. Lead Angle 값을 실시간 Auto Tuning 하는 기법을 설계 및 구현하였다. 실제 Microchip 사의 DSC를 사용하여 Software로 동작을 구현하였으며, PWM 스위칭 하기 위한 반도체 소자는 IGBT 모듈인 IPM을 사용하여 BLDC 모터의 구동회로인 인버터를 구성하였다. 실제 사용하는 400W급 BLDC 모터를 사용하여 Lead Angle 제어와 Auto Tuning 실험결과를 비교 검증하였다.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.280-288
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• 1997

In this paper, we will show that the torque ripple in closed-loop drives of permanent magnet stepping motors is reduced as properly selected lead angle control method. We propose an instantaneous torque equation, which is the function of lead angle, to estimate the influence on torque ripple. We design a closed-loop lead angle control system based on the proposed instantaneous torque equation and measure the instantaneous torque in various excitation modes. It is shown that torque ripple is greatly reduced, as seen from the experimental results as well as from the computer simulation results. For example, torque ripple reduced from 78.25% to 46.82% in the case of 50 PPS single-phase excitation mode operation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.120-130
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• 1999

In this paper, we show that the instantaneous phase current of the bifiler-wound hybrid stepping motor is dependent of lead angle and that the information of motor position is obtained from the instantaneous phase current at ${\pi}/2$ by the theoretical formular and its computer simulation results. From the facts, we design the microcontroller-based motor position sensorless controller of optimal lead angle, which generates the excitation pulses for the closed-loop drives. The controller is consist of microcontroller which has the function of A/D converter, programmable input/output timer, and the transfer table which has the values of optimal lead angle depending on motor velocity, and ROM which has the transfer table of the values of lead angle depending on velocity of motor and the values of instantaneous phase current at ${\pi}/2$. From the design of microcontroller-based controller, we minimize the external interface circuit and obtain flexibility by changing the contents of ROM transfer tables and the control software. We confirm that the designed controller drives the bifilar-wound hybrid stepping motor is the mode of optimal lead angle by comparing the instananeous phase current experimental results and computer simulation results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.26-34
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• 1998

In this paper, we confirm that the instanteneous phase current of the bifilar-wound hybrid stepping motor is dependent of lead angle by the experimental results. The variation of phase current with lead angle gives informations about the rotor position at the moment when phase winding coil is excited. We show that the rotor position of the bifilar-wound hybrid stepping motor for the closed-loop drives can be detected by using the instantaneous phase current measurement. We propose an instantaneous phase current equation as the function of electrical lead angle by the modeling of the bifilar-wound hybrid stepping motor. We also analyze the relationship between instantaneous phase current and rotor position by the computer simulation results. By the experimental results, we also confirm that the information about the rotor position can be obtained from the instantaneous phase current values at the instance of $\pi/2$ electrical angle of excitation pulse. pulse.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1991.10a
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• pp.84-88
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• 1991

The lead angle control of step motor for high speed drive is represented in this paper. It was designed position and speed information feedback system which was composed of step motor coupled with encoder, z-80, and hardware. The relationships between the lead angle and speed characteristics are established by experiments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.53-60
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• 2002

Recently, the development of aerospace and automobile industries brought new technological challenges, related to the growing complexity of products and new geometry models. High speed machining using 5-Axis milling machine is widely used for 3D sculptured surface parts. 5-axis milling of turbine blade generates the vibration, deflection and twisting caused from thin and cantilever shape. So, the surface roughness and the waviness of workpiece are not good. In this paper, The effects of cutter orientation and lead/tilt angle in 5-Axis high speed ball end-milling of turbine blade were investigated to improve the geometric accuracy and surface integrity. The experiments were performed at lead/tilt angle $15^{\circ}$ of workpiece with four cutter directions such as horizontal outward, horizontal inward, vertical outward, and vertical inward. Workpiece deflection, surface roughness and machined surface were measured with various cutter orientations such as cutting direction, and lead/tilt angle. The results show that when 5-axis machining of turbine blade, the best cutting strategy is horizontal inward direction with tilt angle. The results show that when 5-axis machining of turbine blade, the best cutting strategy is horizontal inward direction with tilt angle.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.6
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• pp.577-582
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• 2010

The squeak propensity in the gear box of an automotive seat system is investigated analytically. The mating parts in the gear box are the lead screw and the nut, where the friction stresses are exerted on the thread of the screw. The lead screw is modeled as a circular beam allowing the bending and torsional vibrations. In the system, the lead screw converts rotating to translating motion so that it moves the automotive seat slightly tilted on the floor. The tilting angle is considered one major parameter in this study. Therefore, the equations of motion associated with the non-conservative friction force are derived with the inclusion of the tilting angle. It is found that the squeak noise corresponds to the several bending modes of the lead screw and its propensity is increased by the tilting angle of the seat.

• Applied Microscopy
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• v.24 no.3
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• pp.87-93
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• 1994

In order to elucidate the machinability of lead brass, orthogonal machining experiment was conducted in SEM(Scanning Electron Microscope) equipped with a micro-machining device at a cutting speed of $7{\mu}m/s$ for brass containing 0.2 to 3wt% Pb. The microfactors (i.e., shear angle, contact length between chip and tool) were determined by in-situ observations. Machinability of brass containing lead is discussed in terms of the microfactors and the cutting resistant force tested by lathe cutting. The dynamic behavior of the chip formation of lead brass during the machining process was examined: The chips of lead brass form as a shear angle type. The shear angle increases with the content of lead in (6:4) brass. The pronounced effect of lead on the contact length between chip and tool was observed above 1% Pb. The cutting resistant force tested by lathe decreases remarkably with the lead content in brass. The observed microfactors are in close relation to the tested resistant force in macromachining.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.155-160
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• 2002

Recently, the development of aerospace and automobile industries has brought new technological challenges, rebated to the growing complexity of products and the new geometry of the models. High speed milling with a 5-Axis milling machine has been widely used fur 3D sculptured surface parts. When turbine blades are machined by a 5-axis milling, their thin and cantilever shape causes vibrations, deflections and twists. Therefore, the surface roughness and the waviness of the workpiece are not good. In this paper, the effects of cutter orientation and the lead/tilt angle used to machine turbine blades with a 5-axis high speed ball end-milling were investigated to improve geometric accuracy and surface integrity. The experiments were performed using a lead/tilt angle of 15$^{\circ}$ to the workpiece with four cutter directions such as horizontal outward, horizontal inward, vertical outward, and vortical inward directions. Workpiece deflection, surface roughness and the machined surface were all measured with various cutter orientations such as cutting directions, and lead/tilt angle. The results show that the best cutting strategy for machining turbine blades with a 5-axis milling is horizontal inward direction with a tilt angle.