• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.301-307
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• 2013

MRU(motor reduction unit) for KTX is a assembled complex structure that is equipped with a lot of parts at the express train KTX and that is the core power source operating variable speeds. This study is recorded the dynamic characteristics analysis results tested by EMA which is done through the parts and assembly test, transient analysis and stoped train test in order to design the online monitoring system for KTX MRU. And the mode shapes result from critical vibration frequency explain the relation with variable speeds of express train over 250 km/hr. Also these variable speeds make variable operational frequencies at pinion, axle gear mesh frequency and normal bearing fault frequencies. As the specified speed can make resonance with natural frequencies of the MRU, for the train operating stability, this study also presents the MRU's critical speeds calculated by the each train speed.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.305-314
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• 2012

The purpose of this study was to investigate the effects of joint kinetics and coordination on within-individual differences in maximum vertical jump. 10 male subjects aged 20 to 30 performed six trials in maximum vertical jump and with based on jump height the good(GP) and bad(BP) performances for each subject were compared on joint kinetics of lower extremity and coordination parameters such as joint reverse and relative phase. The results showed that maximum moment, power, and work done of hip joint and maximum moment of ankle joint in GP were significantly higher than that in the BP but no significant differences for the knee joint. We could observe a significant difference in joint reverse timing between both conditions. And also the relative phase on ankle-knee and ankle-hip in GP were significantly lower than that in the BP, which means that in GP joint movements were more in-phase synchronized mode. In conclusion, mechanical outputs of hip and ankle joints had an effect on within-individual differences in vertical jump and the inter-joint coordination and coordination including sequence and timing of joint motion also might be high influential factors on the performances within individual.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.869-874
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• 2010

Recently, a piezo actuator based linear motor has been actively studied because of its higher power density, compactness and quick response. However, the characteristic of small displacement makes the application of a piezo actuator limitative. In order to overcome this limitation, some actuation mechanisms using a piezo actuator are designed by bi-metal composite or more than two piezo actuators. Therefore, it enables to generate large displacement and have high resolution. In the proposed piezo motor, we have designed a bi-directional linear motor that can be operated by only one piezo actuator. In addition, it is activated with low frequency of the applied voltage, since, we utilize first mode shape of structure of motion generator to vibrate. Finally, moving direction can be simply controlled by changing the ratio of input frequency to natural frequency of structure of motion generator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1341-1350
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• 2017

In this paper, a high reliability 30W DC-DC converter is designed considering military standard (MIL-STD) for military applications such as guided weapon and aircraft. The performances and specifications of conventional military grade DC-DC converter are practically analyzed. The requirements for military grade DC-DC converter are established in consideration of MIL-STD and analysis results of conventional product. Two isolated DC-DC converter, forward and fly-back converter, are designed and compared to determine topology. From experimental results under various operating conditions, the forward topology satisfied performances and specifications of MIL-STD for military DC-DC converter.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.3
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• pp.351-359
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• 2010

Bi-fuel system in a spark ignition engine (SIE) is a rising phenomena in today's automobile technology. In a gasoline driven vehicle, alternatively adoption of compressed natural gas (CNG) could be used as a potential substitute to meet the energy requirement and this is possible by some minor changes in the hardware of the existing engine. Gasoline engine is widely used in the passenger cars, light, medium and heavy duty vehicles but the consumption status of the petroleum is decreasing worldwide and at the same time environmental pollution from automobiles is seriously establishes as a threat for every nation in respect to global warming and climate changes. Now-a-days most vehicles operate using CNG for its popularity stems, clean burning properties and cost effective solution compared to other alternative fuels. It refers as a good gaseous fuel because of its high octane number and self ignition temperature. Though the power output is slightly lesser than the gasoline fuel; its thermal efficiency is better than the gasoline for the same SIE. The research paper highlights the reduction of CO, reasonable outcomes of HC emissions with minor increase in $NO_x$ emissions compared with the gasoline fuel to bi-fuel mode in the SIE that meets the emission challenges.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.566-569
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• 2005

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications, due to their excellent power to weight ratio. The paper is proposed maximum torque control of IPMSM drive using artificial intelligent(AI) controller. The control method is applicable over the entire speed range and considered the limits of the inverter's current and voltage rated value. For each control mode, a condition that determines the optimal d-axis current $i_d$ for maximum torque operation is derived. This paper considers the design and implementation of novel technique of high performance speed control for IPMSM using AI controller. This paper is proposed speed control of IPMSM using learning mechanism fuzzy neural network(LM-FNN) and estimation of speed using artificial neural network(ANN) controller. The back propagation neural network technique is used to provide a real time adaptive estimation of the motor speed. The proposed control algorithm is applied to IPMSM drive system controlled LM-FNN and ANN controller, the operating characteristics controlled by maximum torque control are examined in detail. Also. this paper is proposed the experimental results to verify the effectiveness of AI controller.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.756-759
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• 2014

DC/DC converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. The converters can be applied in the regenerative braking of DC motors to return energy back to the supply, resulting in energy savings for the systems at periodic intervals. The fundamental converter studied here consists of an IGBT (Insulated Gate Bipolar mode Transistor), an inductor, a capacitor, a diode, a PWM-IC (Pulse Width Modulation Integrated Circuit) controller with oscillator, amplifier, and comparator. The PWM-IC is a core element and delivers the switching waveform to the gate of the IGBT in a stable manner. Display of the DC/DC converter output depends on the IGBT's changes in the threshold voltage and PWM-IC's pulse width. The simulation was conducted by PSIM software, and the hardware of the DC/DC converter was also implemented. It is necessary to study the fact that the output voltage depends on the duty rate of D, and to compare the output of experimental result with the theory and the simulation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.216-222
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• 2013

A solar power generator is usually installed outdoors and it is exposed to extreme environments such as heavy fall of snow and high speed wind. Therefore, the solar tracker structure should be designed to have sufficient static and dynamic stiffness against such environmental conditions. In this paper, eigenvalue analysis of the solar tracker is carried out by varying the pose of the solar panel and unsteady flow analysis around a single tracker or multi-trackers arranged in a line is performed by varying the parameters such as wind directions, wind speeds and the pose of the solar panel to evaluate whether there exists an instability of resonance due to vortex shedding. Finite element eigenvalue analysis shows that natural frequencies and modes are almost not influenced by the pose of the solar panel and the finite element flow analysis shows that there does not exist periodic vortex shedding due to the flow around single tracker or multiple solar trackers in a line.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.3
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• pp.323-332
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• 2014

Stepper motor is widely used in positioning applications due to its durability and high torque to inertia ratio as well as low cost and ability to be easily controlled with open-loop. Due to increased resolution of position control and improved stability of motion control, microstepping has drawn attention in industry since it was introduced in 1970s. With the increase in computational power and decrease in cost of embedded processors in recent years, drives and control systems for stepper motors have become more sophisticate than ever. Thus, closed-loop control methods have been developed to improve the performance of the stepper motors. In this paper, we review not only basic principles of conventional control methods used for stepper motors but also that of microstepping control. In addition, we surveyed recent development in nonlinear control methods applied to stepper motors. The nonlinear control methods are presented in the view of Lyapunov stability. Nonlinear torque disturbance observer, sliding mode control, and nonlinear phase compensation are also presented.