• Geomechanics and Engineering
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• v.1 no.1
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• pp.17-34
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• 2009

There has been growing agreement that geotechnical reliability-based design (RBD) is necessary for establishing more advanced and integrated design system. In this study, resistance factors for LRFD pile design using CPT results were investigated for axially loaded driven piles. In order to address variability in design methodology, different CPT-based methods and load-settlement criteria, popular in practice, were selected and used for evaluation of resistance factors. A total of 32 data sets from 13 test sites were collected from the literature. In order to maintain the statistical consistency of the data sets, the characteristic pile load capacity was introduced in reliability analysis and evaluation of resistance factors. It was found that values of resistance factors considerably differ for different design methods, load-settlement criteria, and load capacity components. For the total resistance, resistance factors for LCPC method were higher than others, while those for Aoki-Velloso's and Philipponnat's methods were in similar ranges. In respect to load-settlement criteria, 0.1B and Chin's criteria produced higher resistance factors than DeBeer's and Davisson's criteria. Resistance factors for the base and shaft resistances were also presented and analyzed.

• 전자공학회논문지 IE
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• v.48 no.1
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• pp.1-6
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• 2011

In this study, it carried out Electromagnetic Field Analysis of Magnetic Bearing due to stator structure and it got the electrical characteristics of 3 structure types of AMB(Active magnetic bearing) systems to get optimal design criteria. The results of simulation in three types of AMB, using FEM method, type 1, 2, and 3 had many paths to move magnetic flux vectors from N pole to S pole and magnetic flux lines are transferred to rotor as a shaft. The paths help to rotate the rotors. So, their data of electrical properties carry out design of magnetic bearing system and the data help to make design criteria.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.4
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• pp.66-71
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• 2011

This article proposes a novel shift automation mechanism for an automated manual transmission (AMT). The development of an automated manual transmission is currently being paid considerable attention by vehicle manufacturers, with the prospects of combining the comfort of an automatic transmission and the high efficiency of a manual transmission. In order to automate the shift mechanism of a manual transmission, the proposed shift automation mechanism consists of two electric motors, cross shaped pinion gears, rack type shift rails, and a ball splined hollow shaft. First we describe the shift mechanism and operating principles of a manual transmission to investigate important design criteria for the shift automation device. And a new shift automation mechanism is described with its structure, elements, and operating principles in detail. Using a conventional manual transmission, we develop a full three-dimensional CAD model of an AMT which includes main components of the manual transmission and the designed shift automation mechanism. Finally we investigate the operating performances and feasibility of the designed AMT by a dynamic analysis.

• Journal of Power Electronics
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• v.11 no.5
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• pp.743-750
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• 2011

This article deals with the sensor-less control of a DC Motor via a SEPIC Converter-Full Bridge combination powered through solar panels. We simultaneously regulate, both, the output voltage of the SEPIC-converter to a value larger than the solar panel output voltage, and the shaft angular velocity, in any of the turning senses, so that it tracks a pre-specified constant reference. The main result of our proposed control scheme is an efficient linear controller obtained via Lyapunov. This controller is based on measurements of the converter currents and voltages, and the DC motor armature current. The control law is derived using an exact stabilization error dynamics model, from which a static linear passive feedback control law is derived. All values of the constant references are parameterized in terms of the equilibrium point of the multivariable system: the SEPIC converter desired output voltage, the solar panel output voltage at its Maximun Power Point (MPP), and the DC motor desired constant angular velocity. The switched control realization of the designed average continuous feedback control law is accomplished by means of a, discrete-valued, Pulse Width Modulation (PWM). Experimental results are presented demonstrating the viability of our proposal.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.210-215
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• 2004

The dynamic model of ac servo motor is influenced very much due to rotor resistance change and nonlinear characteristic. By using the sliding mode control the dynamic behavior of system can be made insensitive to plant parameter change and external disturbance. This paper describes the application of the sliding mode control for position control of ac servo motor. The control scheme is derived and designed. A design method based on external load parameters has been developed for the robust control of ac induction servo drive. The proposed control scheme are given based on the variable structure controller and slip frequency vector control. Simulated results are given to verify the proposed design method by adoption of sliding mode and show robust control for a change of shaft initial J, viscous friction B and torque disturbance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.556-561
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• 2009

The UAV(Unmanned Aerial Vehicle) that is remotely operating in various and long flight environments must have a very reliable propulsion system. Precise fault diagnosis of the turbo shaft engine for the Smart UAV that has the vertical take-off, landing and forward flight behaviors can promote reliability and availability. This work proposes a new diagnostic method that can identify the faulted components from engine measuring parameter changes using Fuzzy Logic and quantify its faults from the identified fault pattern using Neural Network Algorithms. The proposed diagnostic method can detect not only single fault but also multiple faults.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1643-1645
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• 2005

A newly-built inverter has to undergo a series of stress tests in the final stage of production line. This can be achieved by connecting it to a dynamometer consisting of a three-phase machine joined by a rigid shaft to a DC load machine. The latter is controlled to create some specific load characteristic needed for the test. In this paper a test method is proposed, in which no mechanical equipment is needed. The suggested test stand consists only of a inverter to be tested and a simulator converter. Both devices are connected back- to-back on the AC-side via smoothing reactors. The simulator operates in real-time as an equivalent load circuit, so that the device under test will only notice the behaviour of a three-phase machine under consideration of the load. In odor to wove rightness of the suggested test method, the simulation and actural experiment rallied out emulation for a 2.2kW induction motor.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.4
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• pp.26-30
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• 2005

A rotor run-up or run-down process provide more useful information for modal analysis than normal operation conditions. A traditional difficulty associated with rotor run-up or run-down analysis is the non-stationary nature of vibration data. This paper compares Short-Time Fourier Transform (STFT) and the wavelets analysis in these non-stationary signal analyses. An Adaptive Wavelet Analysis (AWT) is proposed to analyze these signals. Although simulations and experiments in a simple rotor-bearing system show that both STFT and AWT can be used to analyze non-stationary vibration signals in rotor dynamics, proposed AWT provides better results than STFT analysis. From the amplitude-frequency curve obtained by AWT, the modal frequency and damping ratio are calculated. This paper also analyzes the characteristics of signals when the shaft touches the outer hoop in a run-up process. The AWT can give a good result in this complex dynamic analysis of the touching process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.261-262
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• 2011

Conventional automatic transmission system includes a hydrodynamic torque converter to transfer engine torque from an engine crank shaft to a rotatable input members, which are of complex design permitting them to serve several functions. These are clutches or brakes which couple the rotatable input member to member of a planetary gear set. The annulus gear for an automatic transmission is a monolithic gear having a set of gear teeth formed on an inner surface which is coupling with a set of planetary gear. In this study, the flow forming method is applied to the manufacturing of the annulus gear. This cold forming is proper method in order to manufacture dimensionally precise and round hollow components such as annulus gear. By pre-calculated amount of wall thickness reduction, the seamless tube of SAE1026 is compressed above its yield strength, plastically deformed and made to flow in several roll passes. According to this study, the desired geometry of the annulus gear can be achieved when the outer diameter and the thickness of the tube are properly decreased by compressed roll passes and the available material volume is easily forced to flow longitudinally over the shape of mandrel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1126-1131
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• 2001

Excessive vibration in rotating machinery is a problem encountered in many different fields, causing such difficulties as fatigue of machinery components and failure of supporting bearings. Passive techniques, though sometimes limited in their capabilities, have been used in the past to attenuated vibrations. Recently active techniques have been developed to provide vibration control perform beyond that provided by their passive counters. Most often, the focus of active control methods has been to suppress rotating machinery displacements. In cases where vibration results in bearing failures, displacement suppression may not be the best choice of control approaches (it can, in fact, increase dynamic bearing loads which would be even more harmful to bearings). This paper presents two optimal control methods for attenuating steady state vibrations in rotating machinery. One method minimizes shaft displacements while the other minimizes dynamic bearing reaction forces. The two methods are applied to a model of a typical rotating machinery system and their results are compared. It is found that displacement minimization can increase bearing loads, while bearing load minimization, on the other hand, decreases bearing loads.