• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.6
• /
• pp.525-532
• /
• 2017

The development of an inkjet-based manufacturing machine for the production of next-generation displays using organic and quantum-dot light emitting diodes at a low cost has been conducted. To employ inkjet printing in production lines of displays, the development of a high-speed inkjet-monitoring device to verify the reliable droplet jetting status from multiple nozzles is required. In this study, an inkjet monitoring device using a rotatable mirror with rotary and linear ultrasonic motors is developed in place of a conventional, linear reciprocating, motion-based inkjet monitoring device. Its performance is also demonstrated. The measurements of circular patterns with diameters of $10{\mu}m$, $30{\mu}m$, and $50{\mu}m$ are performed with the accuracies of $0.5{\pm}1.0{\mu}m$, $-1.2{\pm}0.3{\mu}m$, and $0.2{\pm}0.5{\mu}m$, respectively, within 17 sec. By optimizing the control program, the takt time can be reduced to as short as 8.6 sec.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.7
• /
• pp.1039-1046
• /
• 2017

Campus microgrid is designed and built by considering not only power generation but also power consumption management as connected microgrid type because the main goal of the campus microgrid is to save power consumption costs. There are many functions to achieve the goal and they are mainly to use generation-based functions such as islanding operation for peak management and for emergency events. In power distribution operation, Conservation Voltage Reduction (CVR) is applied in order to reduce power consumption. The CVR is defined as a function for load consumption reduction by voltage reduction in order to reduce peak demands and energy consumption. However, application of CVR to microgrid is difficult because the microgrid cannot control a tap of transformer in a substation and the microgrid normally is not designed with phase modifying equipment like a step-voltage-regulator which can control voltage in power distribution system operation. In addition, an impact of the CVR is depended on load characteristics such as a normal load, a rated power, and synchronous motors. Therefore, this paper proposes an application of CVR using linear voltage control based AVR in campus microgrid with power consumption reduction considering characteristics of load and component in the microgrid. The proposed system can be applied to each buildings by a configuration of power distribution cables; and the application results and CVR factor are presented in this paper.

• Smart Structures and Systems
• /
• v.13 no.2
• /
• pp.281-303
• /
• 2014

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

• Journal of The Korean Astronomical Society
• /
• v.51 no.6
• /
• pp.207-214
• /
• 2018

A coelostat is often used for solar observations, because it corrects the image rotation automatically by guiding sunlight into a fixed telescope with two plane mirrors. For the purposes of education and spectroscopic observation, the solar group at Seoul National University (SNU) plans to develop the SNU coelostat (SNUC) and install it in the SNU Astronomical Observatory (SAO). Requirements of the SNUC are < 1" positioning accuracy with 30 cm beam size on the entrance pupil in the compact dome. To allow for installation in the small dome, we design a compact slope type coelostat with a 45 cm primary plane mirror and a 39 cm secondary plane mirror. The motion of the SNUC is minimized by fixing the position of the slope frame. Numerical simulations of the available observational time of the designed coelostat shows that the sun can be observed ay all times from June to early August and at least three hours in other months. Since the high accuracy driving motors installed in the SNUC can be affected by external environment factors such as humidity and temperature variations, we design a prototype to test the significance of these effects. The prototype consists of a 20 cm primary plane mirror, a 1 m slope rail, a direct drive motor, a ballscrew, a linear motion guide, an AC servo motor, a reduction gear and a linear encoder. We plan to control and test the accuracy of the prototype with varying atmospheric conditions in early 2019. After testing the prototype, the SNUC will be manufactured and installed in SAO by 2020.

• Journal of Powder Materials
• /
• v.29 no.6
• /
• pp.459-467
• /
• 2022

Soft magnetic powder materials are used throughout industries such as motors and power converters. When manufacturing Fe-based soft magnetic composites, the size and shape of the soft magnetic powder and the microstructure in the powder are closely related to the magnetic properties. In this study, Fe-Si-Al-P alloy powders were manufactured using various manufacturing process parameter sets, and the process parameters of the vacuum induction melt gas atomization process were set as melt temperature, atomization gas pressure, and gas flow rate. Process variable data that records are converted into 6 types of data for each powder recovery section. Process variable data that recorded minute changes were converted into 6 types of data and used as input variables. As output variables, a total of 6 types were designated by measuring the particle size, flowability, apparent density, and sphericity of the manufactured powders according to the process variable conditions. The sensitivity of the input and output variables was analyzed through the Pearson correlation coefficient, and a total of 6 powder characteristics were analyzed by artificial neural network model. The prediction results were compared with the results through linear regression analysis and response surface methodology, respectively.

• Proceedings of the KIEE Conference
• /
• 2008.04a
• /
• pp.73-74
• /
• 2008

In this study, we developed a robotic gait trainer which induces the active gait training based on predefined continuous proper lower extremity joint movements. AC servo motors and linear actuators were used to control hip and knee joints of patients and the weight support system was used to support the patient's weight during the gait training. We also implemented a Gill program to set the gait training pattern with several training parameters and to confirm states of patients and the system through the visual feedback. The effectiveness of the gait training system will be determined by the long-term clinical experiments in the future. We expect that the developed robotic gait training system could be applied very practically to recover gait abilities for persons with gait disorder.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.3079-3085
• /
• 2011

Through Korean Urban Maglev Program started in 2006, an urban maglev train was developed and the demonstration line is under construction as of now in 2011. The target speed of the developed maglev train is 110km/h, and the core technologies for super speed maglev trains over 500km/h are being studied. The propulsion and levitation systems of the super speed maglev train under consideration consist of linear synchronous motors (LSM) and levitation electromagnets which also act as a mover of LSM. In addition, guidance electromagnets are used to ensure stable running on curved tracks during super speed operation. The levitation and guidance control is focused on in this paper. For experimental purpose, a small maglev train is being manufactured, and its levitation and guidance controller is studied. The main task of the controller is to maintain the gap between the corresponding electromagnet and the guideway constantly. In general, measurements of the gap, acceleration and current and so on are utilized, and the gap control is implemented independently for each electromagnet. In this paper, the levitation and guidance system is modelled considering mechanical interactions, and the levitation and guidance controller is proposed based on this model. The developed controller is verified by various simulations using MATLAB/Simulink.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.1832-1837
• /
• 2011

This paper presents the optimal permanent magnet shape on the rotor of an interior permanent magnet motor to reduce the core losses and improve the performance. As permanent magnet has conductivity inherently, it causes huge amount of eddy current losses by the slot harmonics with concentrated winding. This loss is roughly 100 times larger than that of distributed winding in high speed operation and it cannot be ignored, especially on traction motors. Each eddy current loss on permanent magnet has been investigated in detail by using FEM(Finite Element Method) instead of EMCNM(Equivalent Magnetic Circuit Network Method) in order to consider saturation and non-linear magnetic property. Simulation-based DOE(Design Of Experiment) is also applied to avoid large number of analyses according to each design parameter and consider expected interactions among parameters. Consequently, the optimal design to reduce the core loss on the permanent magnet while maintaining or improving motor performance is proposed by an optimization algorithm using regression equation derived and lastly, the core loss reduction on the proposed shape of the permanent magnet is verified by FEM.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1060-1065
• /
• 2003

This paper contributes to development of a new chip mounting head system for flip chip. Recently, the LDM(Linear DC Motor) has been widely used, because it has particular merits than the rotary type motors. In this paper, we proposed a macro/micro positioning system for force control of a chip mounting system. In the proposed macro/micro system, the macro actuator provide the system with a gross motion while the micro device yields fine tuned motion to reduce the harmful impact force that occurs between very small sized electronic parts and PCB surface. In order to prove the effectiveness of the proposed macro/micro chip mounting system, we compared the proposed chip mounting head with the conventional chip mounting head equipped with a macro actuator only. A series of experiments were executed under the mounting conditions of various access velocities and PCB stiffness. As a result of this study, a satisfactory voice coil actuator as the micro actuator has been developed, and its performance meet well the specifications desired for the design of the chip mounting head system and show good correspondence between theoretical analysis and experimental results.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.552-557
• /
• 2004

This paper presents a disturbance observer based on an $H_{\infty}$ controller synthesis for the trajectory control of a hydraulic excavator. Compared to conventional robot manipulators driven by electrical motors, the hydraulic excavator has more nonlinear and coupled dynamics. In particular, the interactions between an excavation tool and the materials being excavated are unstructured and complex. In addition, its operating modes depend on working conditions, which make it difficult to not only derive the exact mathematical model but also design a controller systematically. In this study, the approximated linear model obtained through off-line system identification is used as nominal plant model for a disturbance observer. A disturbance observer based tracking controller which considers the effect of disturbance and model uncertainty is synthesized in $H_{\infty}$ frameworks. Simulation results are used to demonstrate the applicability of the proposed control scheme.