• Journal of Korea Foundry Society
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• v.25 no.1
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• pp.16-22
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• 2005

This study aims to investigate the effects of the microstructures and nodule type on the fatigue characteristics of cast iron. Fatigue tests were carried out in tension-tension mode using a servo-hydraulic testing machine with load control mode operating at a frequency of 15 Hz. The tests were conducted at stress ratio R=Kmin/Kmax, of 0.1. Initial crack ${\Dalta}K$ values were highly performed with increase in tensile strength of DCI fatigue specimens. ${\Dalta}K_{th}$ region, fatigue crack propagation was primarily advanced through cell boundary and in periphery of near nodule. Fatigue crack propagation rate of D2 consisted with 2Phase(Ferrite+Pearlite) was slow due to crack closure enhanced by crack deflection and occurred crack branching. The generation of crack branch was occurred due to interaction of crack-nodule. At Threshold and Paris zone, the fractographs of the fatigue fracture surface for DCI show typical striations of a ductile fracture and isolated cleavage planes near graphite. The effect of microstructure on fatigue crack propagation of GC strongly depends on the type of flake. The generation of crack branch occurred due to interaction of crack-nodule. The fractographs of the fatigue fracture surface for GC show cleavage plane along the flake graphite.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.381-386
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• 2014

In order to investigate the effect of contact load, which is one of the fretting corrosion factors affecting the electric connector, a coupled fretting corrosion specimens were prepared using a tin-plated brass coupon with a thickness of $3{\mu}m$. Electric resistance of the contact was measured during the fretting corrosion test period. There was increase in resistance with fretting cycles. The change in resistance can be classified by 3 stages. The first stage exhibited low and stable resistance. Second stage showed steady increment of the resistance and third stage showed very high and intermittent resistance. The relationship between the failure cycle (Nf) and contact force (P) can be drawn as; It is possible to draw the prediction equation for the failure cycle of the electric connector corresponding to the very high and intermittent resistance under various environment conditions through the fretting tests under various conditions such as load, displacement, temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1249-1255
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• 2010

An ultra high- pressure system generally consists of a hydraulic power unit, an oil supply unit, an electrical power supply device, and an electrical control device. The hydraulic power unit supplies the hydraulic power to the intensifier to create generate ultra high pressure. The intensifier amplifies increases the pressure using the oil supplied from by the hydraulic power unit. The electrical supply devices and control devices maintain are provided for the electric motors, valves, and sensors. In this study, instead of a flow-control device, a pressure-control type device was mounted on a manifold block in the hydraulic power unit instead of the flow-control type. A servo valve was fitted in the intensifier, and the performance characteristics of the intensifier varied according to the variations of in the pressure cycle and with the temperature of the operating oil in the hydraulic power unit.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.427-436
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• 2002

This paper presents an implementation of high-dynamic performance of position sensorless motion control system of Reluctance Synchronous Motor(RSM) drives for an industrial servo system with direct torque control(DTC). The problems of high-dynamic performance and maximum efficiency RSM drives controlled by DTC are saturation of stator linkage flux and nonlinear inductance characteristics with various load currents. The accurate estimation of the stator flux and torque are obtained using stator flux observer of which a saturated inductance $L_d$ and $L_q$ can be compensated by adapting from measurable the modulus of the stator current and rotor position. To obtain fast torque response and maximum torque/current with varying load current, the reference command flux is ensured by imposing $I_{ds} = I_{qs}$. This control strategy is proposed to achieve fast response and optimal efficiency for RSM drive. In order to prove rightness of the suggested control algorithm, the actual experiment carried out at $\pm$20 and $\pm$1500 rpm. The developed digitally high-performance motion control system shown good response characteristic of control results and high performance features using 1.0kW RSM which has 2.57 Ld/Lq salient ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.166-174
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• 2014

Fuel injection pressure has steadily increased in diesel engines for the purpose of improving fuel efficiency and cleaning exhaust gas, but it has now reached a point, where the cost for higher pressure does not warrant additional gains. Common rail systems on modern diesel engines have fuel pumps that are mechanically driven by crankshaft. The pumps actually house two pumping module inside: a low pressure pump component and a high pressure pump component. Part of the fuel compressed by the low pressure component returns to the tank in the process of maintaining the pressure in the common rail. Since the returning fuel represents pumping loss, fuel economy improves if the returned fuel can be eliminated by using a properly controled electrical fuel pump. As the first step in developing an electrical fuel pump the fuel supply system on a 6 liter diesel engine was modeled with AMESim to analyze the workload and the fuel feed rate of the injection pump, and the results served as basis for selecting a suitable servo motor and a reducer to drive the pump. A motor controller was built using a DSP and a program which controls the common rail pressure using a proportional control method based on the target fuel pressure information from the engine ECU. A test rig to evaluate performance of the fuel pump is implemented and used to show that the newly developed electrically driven fuel pump can satisfy the fuel flow demand of the engine under various operating conditions when the rotational speed of the pump is adequately controlled.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1077-1084
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• 2017

Camshaft engines designed for constant engine loads have been applied to existing marine diesel engines. However, due to environmental regulations, electro-hydraulic servo mechanisms, which have a loaddependent cylinder liner jacket water cooling system (LDCL-JWCS), have been recently developed to individually control the temperature of the cylinders depending on the engine load. In this system, the 3-way valve, which prevents low temperature corrosion by reducing the temperature difference between the upper and lower parts of the cylinder, has been employed, but the outlet mass flow of the existing valve is low. In this study, the design of the internal shape of the 3-way valve was performed by analyzing the effects of the design parameters of the valve shape on the performance (i.e., the outlet mass flow rate and temperature). The proposed model was verified by comparing its performance to that of existing marine diesel engine valves.

• Journal of Animal Environmental Science
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• v.6 no.2
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• pp.105-112
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• 2000

The objective of this study was to determine the teat locations and to develop a teat cup handling system operated by a robot. The results of this study were summarized as follows: 1. The teat cup attaching and detaching operation system developed in this study consists of a control computer, a five-dimensional robot(PERFORMER-MK2), a DC servo gripper, a robot controller, two CCD-cameras (WV-vp410), an image grabber board(DT3153), a model cow, and a teat cup unit. 2. The coordinates of teat locations were measured by a stereo image processing unit. The error ranges of teats coordinates measured were (x, y, z) = (0.83, 1.95, 0.81) mm. When those were transferred into the Robot Coordinate System(RCS) coordinate, the total error ranges measured were x = 0.9 mm, y = 2.0 mm, z = 0.9 mm. 3. The rates of success of teat cup attaching and detaching operation by a robot system were 91.5% on average; the operation time needed were 27.8 sec. Total working hours for the teat cup handling including image processing were 86.1 sec.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1171-1179
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• 2012

In this study, we consider a dynamic positioning system (DPS) design problem that can be extended to many application fields. Toward this end, tracking and positioning control problems are discussed. In particular, we design a tracking control system that incorporates an observer based on the 2-DOF servo system design approach in order to obtain the desired state information. In the case of observer design, a weighted $H_{\infty}$ error bound approach for a state estimator is considered. Based on an algebraic Riccati equation (inequality) approach, a necessary and sufficient condition for the existence of a full-order estimator that satisfies the weighted $H_{\infty}$ error bound is introduced. The condition for the existence of the estimator is denoted by a linear matrix inequality (LMI) that yields an optimized solution and the observer gain.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.74-80
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• 2006

This paper deals with the control and fault monitoring of a DDV hydraulic actuation system. A hydraulic servo system has a nonlinear dynamics of an orifice flow through a valve spool. A full nonlinear model for a DDV actuation system is driven, and linearized to a simple model which is convenient for a control loop and fault monitor design. A top level requirement on the performance and safety for the actuation system is introduced. A control system and fault monitoring structure which can meet these requirements are discussed. A simulation package for a DDV actuation system which has a triplex redundant structure is developed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.71-80
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• 2002

According to the rapid growth of high speed and precise industry, the application of synchronous motor has been increased. In the application fields, these fast dynamic response is of prime importance. In particular, since the PMLSM(Permanent Magnet Linear Synchronous Motor) has characteristics of high speed, high thrust, it has been used in high-performance servo drive. From these reasons, it is recently used for high precise position control, and machine tool. In this paper, a study of the sliding mode with VSS (Variable Structure System) design for a PMLSM is presented. For fast and precise motion control of PMLSM, the compensation of disturbance and parameter variation is necessary. Hence we eliminate the reaching phase use of VSS that is changed to switching function and vector control using the state observer. And we proposed to sliding mode control algorithm so that realize fast response without overshoot, disturbance and parameter variation.