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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 39, Issue 12 - Dec 2015
Volume 39, Issue 11 - Nov 2015
Volume 39, Issue 10 - Oct 2015
Volume 39, Issue 9 - Sep 2015
Volume 39, Issue 8 - Aug 2015
Volume 39, Issue 7 - Jul 2015
Volume 39, Issue 6 - Jun 2015
Volume 39, Issue 5 - May 2015
Volume 39, Issue 4 - Apr 2015
Volume 39, Issue 3 - Mar 2015
Volume 39, Issue 2 - Feb 2015
Volume 39, Issue 1 - Jan 2015
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Measurement and Evaluation of Thermal Expansion Coefficients of Micrometer-Sized SiO
Particle-Reinforced Epoxy Composites
Jo, Hyu Sang ; Kang, Hee Yong ; Lee, Gyo Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 129~135
DOI : 10.3795/KSME-A.2015.39.2.129
In this experimental study, the thermal stability values of micrometer-sized silica particle-reinforced epoxy composite specimens were evaluated by measuring their thermal expansion coefficients and Young's moduli. For all specimens used in this study (from the baseline specimen to that containing 70 wt% silica filler), the thermal expansion coefficients and Young's moduli were gradually reduced down to 25% and increased up to 51%, respectively. The results of the experiment were compared with those of certain empirical models. The experimental results of the measurement of thermal expansion coefficients corresponded well with those of Kerner's model, which considers the bulk and shear moduli of the matrix and silica filler. However, the results of the measurement of Young's moduli using the empirical Mori-Tanaka model were observed to match better with those of the experiment. The comparison of the results of the experiment with those of the empirical models demonstrated that a reliable model for measuring the thermal expansion coefficients and Young's moduli of composite specimens needs to consider certain property variations in the composites in addition to volume fraction changes in the filler and matrix.
Stewart Platform-Based Master System for Tele-Operation of a Robot Arm
Lee, Sang-Duck ; Yu, Hong-Sun ; Ahn, Kuk-Hyun ; Song, Jae-Bok ; Kim, Jong-Won ; Ryu, Jae-Kwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 137~142
DOI : 10.3795/KSME-A.2015.39.2.137
Teleoperation of a robot arm working in hazardous environments has been studied in the field of defense and security. A master system is an essential part that plays an important role in the teleoperation. We developed a master system, which is an essential part in the teleoperation, so that it can operate the slave robot arm intuitively and has excellent mobility and portability compared to conventional master systems. The master system adopted a Stewart platform to minimize the size and weight, and the legs of the Stewart platform are composed of wires to improve the operation range of the system. The experimental validation of the developed master system is conducted with a commercial IMU, and the experimental results show that the proposed master system can perform reliable and dexterous teleoperation.
Analysis of Unsteady Propagation of Mode III Crack in Arbitrary Direction in Functionally Graded Materials
Lee, Kwang Ho ; Cho, Sang Bong ; Hawong, Jai Sug ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 143~156
DOI : 10.3795/KSME-A.2015.39.2.143
The stress and displacement fields at the crack tip were studied during the unsteady propagation of a mode III crack in a direction that was different from the property graduation direction in functionally graded materials (FGMs). The property graduation in FGMs was assumed based on the linearly varying shear modulus under a constant density and the exponentially varying shear modulus and density. To obtain the solution of the harmonic function, the general partial differential equation of the dynamic equilibrium equation was transformed into a Laplace equation. Based on the Laplace equation, the stress and displacement fields, which depended on the time rates of change in the crack tip speed and stress intensity factor, were obtained through an asymptotic analysis. Using the stress and displacement fields, the effects of the angled property variation on the stresses, displacements, and stress intensity factors are discussed.
Analysis of Zig-Zag Error in Gantry Type Machine
Lee, Eung Suk ; Lee, Seung Bum ; Kim, Gi Hwan ; Min, Deul Le ; Park, Jong Bum ; Park, Min Su ; Jin, E Lim ; Kim, Tae Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 157~162
DOI : 10.3795/KSME-A.2015.39.2.157
A large five-axis gantry-type machine performs cutting operations by moving the gantry, along with a bed. During operation, there are three sources of position (zig-zag) errors: 1) the position difference between two control motors on the X axis, 2) friction difference from the different column weights, and 3) torque of the rotating spindle. This study improved the performance of a gantry-type machine by analyzing these three error sources. We changed the mass of a column in the gantry structure and measured the effect on the friction result. We also studied the spindle torque influences on the movement performance of the gantry in relation to the spindle rotation.
Threshold Estimation of Generalized Pareto Distribution Based on Akaike Information Criterion for Accurate Reliability Analysis
Kang, Seunghoon ; Lim, Woochul ; Cho, Su-Gil ; Park, Sanghyun ; Lee, Minuk ; Choi, Jong-Su ; Hong, Sup ; Lee, Tae Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 163~168
DOI : 10.3795/KSME-A.2015.39.2.163
In order to perform estimations with high reliability, it is necessary to deal with the tail part of the cumulative distribution function (CDF) in greater detail compared to an overall CDF. The use of a generalized Pareto distribution (GPD) to model the tail part of a CDF is receiving more research attention with the goal of performing estimations with high reliability. Current studies on GPDs focus on ways to determine the appropriate number of sample points and their parameters. However, even if a proper estimation is made, it can be inaccurate as a result of an incorrect threshold value. Therefore, in this paper, a GPD based on the Akaike information criterion (AIC) is proposed to improve the accuracy of the tail model. The proposed method determines an accurate threshold value using the AIC with the overall samples before estimating the GPD over the threshold. To validate the accuracy of the method, its reliability is compared with that obtained using a general GPD model with an empirical CDF.
Optimal Design of Gerotor with Combined Profiles (Three-Ellipse and Ellipse-Involute-Ellipse) Using Rotation and Translation Algorithm
Bae, Jun Ho ; Lee, Ho Ryul ; Kim, Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 169~177
DOI : 10.3795/KSME-A.2015.39.2.169
Because technology of the sintering process is highly advanced, the gerotor used in the internal gear pumps of vehicles has advantages for manufacturing complex profiles and obtaining durability and minimization. However, it has been necessary to continuously improve the flow rate and noise of internal gear pumps for better fuel efficiency. The existing rotor was designed using a translation algorithm. This caused a discontinuity of the rotor profile, which had adverse effects on the performance. In this study, to improve the discontinuity of the profile, a new design program using a rotation and translation algorithm was developed, and two types of combined multiple profiles (three-ellipses and ellipse 1-involute-ellipse 2) were generated. Then, the performances (flow, flow rate, specific sliding, and pressure angle) of these profiles were calculated. On the basis of the calculation results for the performances, optimal designs of the two types were carried out and verified by comparing their performances with those of the existing rotor profiles.
Kalman Filter for Estimation of Sensor Acceleration Using Six-axis Inertial Sensor
Lee, Jung Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 179~185
DOI : 10.3795/KSME-A.2015.39.2.179
Although an accelerometer is a sensor that measures acceleration, it cannot be used by itself to measure the acceleration when the orientation of the sensor changes. This paper introduces a Kalman filter for the estimation of a sensor acceleration based on a six-axis inertial sensor (i.e., a three-axis accelerometer and three-axis gyroscope). The novelty of the proposed Kalman filter lies in the fact that its state vector includes not only the tilt angle variable but also the sensor acceleration. Thus, the filter can explicitly estimate the latter with a high accuracy. The accuracy of acceleration estimates were validated experimentally under three different dynamic conditions, using an optical motion capture system. It could be concluded that the performance of the proposed Kalman filter was comparable to that of the state-of-the-art estimation algorithm employed by the Xsens MTw. The proposed algorithm may be more suitable than inertial/magnetic sensor-based algorithms for various applications adopting six-axis inertial sensors.
Cause of and Solution for Damage to STS310S Tube in Heat Exchange Devices
Kim, Jin Wook ; Kim, Seon Hwa ; Jeong, Jin Hyuk ; Kim, Young Soo ; Nam, Ki Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 187~193
DOI : 10.3795/KSME-A.2015.39.2.187
The STS310S tube has excellent heat transfer ability and is widely used as the material for heat transfer tubes in heat exchange devices. Mixtures of gas and water flow inside the tube whereas hot flame flows outside it. In this environment, the material of the tube may undergo embrittlement, which can cause leakage. Cracks can propagate from the inside of the tube to its outside and result in brittle fracture. This study identified the cause of brittle fracture in the STS310S tube through experiments and discussion, and proposed solutions to prevent fracture.
Integrated Control Algorithm of Hydraulic Pump with Electric Motor to Improve Energy Efficiency of Electric Excavator
Lee, Jeeho ; Lee, Jihye ; Lee, Hyeongcheol ; Oh, Chang Eun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 195~201
DOI : 10.3795/KSME-A.2015.39.2.195
An electric excavator consumes battery energy to drive an electric motor attached to a hydraulic pump to generate hydraulic power. In a conventional hydraulic excavator, the hydraulic pump is controlled by regulators, which are used to optimize the diesel engine efficiency. Because of a lack of battery energy capacity, an electric excavator controller should consider not only the electric motor efficiency but also the hydraulic pump efficiency. Thus, electric motor and hydraulic pump efficiency maps were constructed. An optimal operating map (OOM) was created based on the most efficient operating points under each input condition. An integrated control algorithm controlled the speed of the electric motor and displacement of the hydraulic pump according to the OOM. To confirm the utility of this algorithm, a model-in-the-loop simulator for the algorithm with an electric excavator was established. The simulation results showed that the integrated control algorithm improved the energy efficiency of an electric excavator.
Development of Real-Time Simulator for a Heavy Duty Diesel Engine
Noh, Young Chang ; Park, Kyung Min ; Oh, Byoung Gul ; Ko, Min Seok ; Kim, Nag In ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 203~209
DOI : 10.3795/KSME-A.2015.39.2.203
Recently, the portion of electronic control in an engine system has been increasing with the aim of meeting the requirements of emissions and fuel efficiency of the engine system in the construction machinery industry. Correspondingly, the complexity of the engine management system (EMS) has increased. This study developed an engine HiLS system for reducing the cost and time required for function development for the EMS. The engine model for HiLS is composed of air, fuel, torque, and dynamometer models. Further, the mean value method is applied to the developed HiLS engine model. This model is validated by its application to a heavy-duty diesel engine equipped with an exhaust gas recirculation system and a turbocharger. Test results demonstrate that the model has accuracy greater than 90 and also verify the feasibility of the virtual calibration process.
Improving Fuel Efficiency of a Hybrid Excavator
Cho, Sungwoo ; Yoo, Seungjin ; Park, Cheol-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 211~217
DOI : 10.3795/KSME-A.2015.39.2.211
Emission gas regulations and constantly increasing fuel costs call for the worldwide use of environmentally friendly and energy-efficient machines in industry. To meet these requirements, a hybrid excavator prototype has been developed that incorporates an electric swing motor, engine assist motor, and ultra-capacitor module into a conventional hydraulic excavator of the 22-ton class. This paper mainly describes a few techniques to optimize its energy efficiency. These include 1) controlling the engine speed in proportion to the load torque, 2) controlling the pump displacement when driving the electric swing system, 3) managing the ultra-capacitor voltage to minimize the electrical energy loss, and 4) reducing the cooling fan speed to improve the energy efficiency of the system.
Study on Characteristics of Hydraulic Servo System for Force Control of Hydraulic Robots
Kim, Hyo-Gon ; Lee, Jong-Won ; Park, Sangdeok ; Han, Changsoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 219~225
DOI : 10.3795/KSME-A.2015.39.2.219
Because a hydraulic actuator has high power and force densities, this allows the weight of the robot's limbs to be reduced. This allows for good dynamic characteristics and high energy efficiency. Thus, hydraulic actuators are used in some exoskeleton robots and quadrupedal robots that require high torque. Force control is useful for robot compliance with a user or environment. However, force control of a hydraulic robot is difficult because a hydraulic servo system is highly nonlinear from a control perspective. In this study, a nonlinear model was used to develop a simulation program for a hydraulic servo system consisting of a servo valve, transmission lines, and a cylinder. The problems and considerations with regard to the force control performance for a hydraulic servo system were investigated. A force control method using the nonlinear model was proposed, and its effect was evaluated with the simulation program.
Test of Vision Stabilizer for Unmanned Vehicle Using Virtual Environment and 6 Axis Motion Simulator
Kim, Sunwoo ; Ki, Sun-Ock ; Kim, Sung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 227~233
DOI : 10.3795/KSME-A.2015.39.2.227
In this study, an indoor test environment was developed for studying the vision stabilizer of an unmanned vehicle, using a virtual environment and a 6-axis motion simulator. The real driving environment was replaced by a virtual environment based on the Aberdeen Proving Ground bump test course for military tank testing. The vehicle motion was reproduced by a 6-axis motion simulator. Virtual reality driving courses were displayed in front of the vision stabilizer, which was located on the top of the motion simulator. The performance of the stabilizer was investigated by checking the image of the camera, and the pitch and roll angles of the stabilizer captured by the IMU sensor of the camera.
Image Tracking Based Lane Departure Warning and Forward Collision Warning Methods for Commercial Automotive Vehicle
Kim, Kwang Soo ; Lee, Ju Hyoung ; Kim, Su Kwol ; Bae, Myung Won ; Lee, Deok Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 2, 2015, Pages 235~240
DOI : 10.3795/KSME-A.2015.39.2.235
Active Safety system is requested on the market of the medium and heavy duty commercial vehicle over 4.5ton beside the market of passenger car with advancement of the digital equipment proportionally. Unlike the passenger car, the mounting position of camera in case of the medium and heavy duty commercial vehicle is relatively high, it is disadvantaged conditions for lane recognition in contradiction to passenger car. In this work, we show the method of lane recognition through the Sobel edge, based on the spatial domain processing, Hough transform and color conversion correction. Also we suggest the low error method of front vehicles recognition in order to reduce the detection error through Haar-like, Adaboost, SVM and Template matching, etc., which are the object recognition methods by frontal camera vision. It is verified that the reliability over 98% on lane recognition is obtained through the vehicle test.