• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.4
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• pp.61-68
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• 2012

In this paper, a closed-loop sensorless stroke control system for a linear compressor has been designed. In order to estimate the piston position accurately, motor parameters are identified as a function of the piston position and the motor current. These parameters are stored in ROM table and used later for the accurate estimation of piston position. The identified motor parameters are approximated to the several surface functions in order to decrease memory size. They can also be divided into 2 or 4 subsections to decrease identification errors. The effect of the order of surface functions and division of subsections on identification errors and computation time is analyzed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.3
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• pp.150-157
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• 2002

This paper presents preliminarily an implementation of digital high-performance motion control system of Reluctance Synchronous Motor (RSM) drives with direct torque control (DTC). The system consist of stator flux observer, torque estimator, two hysteresis band controllers, an optimal switching look-up table, IGBT voltage source inverter, and TMS320F240 DSP controller made by Texas Instruments. The stator fluff observer is based on the combined voltage and current model with stator flux feedback adaptive control, and the input of the observer are the stator voltage and current of motor terminal for wide speed range. The rotor position and speed sensor used 6000 pulse/rev encoder. In order to prove rightness of the suggested control algorithm, we have some simulation and actual experimental system at $\pm$20 and $\pm$2000 rpm. The developed digitally high-performance motion control system+ are shown a good response characteristic of control results and high performance features using 1.0kW RSM which has 2.57 Ld/Lq salient ratio.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1235-1238
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• 2004

Thresholding has been used to reduce the number of gray values in images. Typically, a single threshold value has been used, resulting in two gray level images. Image reduction of one single threshold value, however, may lose too much of the high-frequency edge information. Thus, dynamic thresholding that uses a different threshold for each pixel is preferred instead of using a single threshold value. Dynamic thresholding can preserve high frequency details as well as reduce the size of images. Since it takes long time to perform existing software dynamic thresholding in an embedded system, this paper proposes and implements a circuit by using a FPGA in order to perform a real-time dynamic thresholding,. The proposed circuit consists of two counters, and threshold look-up table, and control unit. The values of two counters determine each pixel position, the threshold look-up table converts each pixel value into other value, and the control unit generates necessary control signals. On arriving from a camera to the proposed circuit, each pixel is compared with its threshold value and is converted into other gray value. An image processing system by using the proposed circuit will be implemented and some experiments will be performed.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.91-97
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• 2007

The purpose of this study was to investigate the changes of various balls velocity under the different surface conditions after impact. For this study, four different balls were used which are golf ball, tang-tang ball, table tennis ball, and iron ball. And two different types of ground conditions were used which are artificial grass green and glass green. Movements of putter head and ball were recorded with 2 HD video cameras(60 Hz, 1/500s shutter speed). Small size control object($18.5cm{\times}18.5cm{\times}78.5cm$) was used in this study. To transfer the same amount of kinetic energy to the ball, pendulum putting machine was used. Analyzing the process of impact and the ball movement, a putter was digitized the whole movement but the ball was digizited within the 50cm movement. Velocities were calculated by the first central difference method(Hamill & Knutzen, 1995). Putter head velocities were about 112.2cm/s-116.2cm/s at impact. Maximum ball velocities were appeared 0.08s-0.10s after impact no matter what the ground conditions are. Table tennis ball recorded higher ball velocities than the other ball velocities and iron ball recorded the lowest ball velocity in this group. But Table tennis ball was influenced with the frictional force and immediately was decreased at the artificial grass green condition. If an object is received the kinetic energy under the static condition(v=0cm/s), the object recorded the maximum velocity shortly after the impact and then decreased the velocity because of the frictional force. The ball distance from the start position to the peak velocity position is about 6cm-10cm under the 112.2cm/s-116.2cm/s putting velocity with putter. 0.25 seconds later after impact balls were placed 40cm distance from the original position except iron ball. In this study, ball moving distances were too short therefore it was not possible to investigate the reactions after the translational force is disappeared. Rotational force would play a major role at the end of the ball movement. Future study must accept two things. One is long distance movement of ball and the other is balanced ground. Three-piece ball is a good item to investigate the golf ball movement on the different surface conditions.

• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.85-94
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• 2008

Automated Guided Vehicles (AGVs) are important equipment in automated container terminals. To utilize AGVs for transporting containers from a position to another, the deadlock is a serious problem that must be solved before they are deployed to real operations. This study assumes that traveling area for AGVs are divided into a large number of grid-blocks and, as a method of traffic control, grid-blocks are reserved in advance during the travel of AGVs. The purposes of the reservation are to make the room between AGVs and to prevent deadlocks. Because the size of an AGV is much larger than the size of a grid-block on guide paths, this study assumes an AGV may occupy more than one grid-block at the same time. This study suggests a method for constructing a table of reservation schedules by using a simulation. A sensitivity analysis was conducted to evaluate the performance of the reservation method in this study.

• ETRI Journal
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• v.36 no.6
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• pp.905-912
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• 2014

In this paper, a new architecture is proposed to achieve complexity efficiency in implementing variable pulse position modulation (VPPM). VPPM, specified in IEEE 802.15.7, can support wireless communication and dimming control simultaneously using visible light. The proposed architecture is based on the VPPM signal property in which the transition point of the modulated output is obtained by counting the sample index and comparing it to both the assigned dimming factor and the transmitting data. Therefore, the proposed architecture can be composed of simple logics, including a counter, a comparator, and an inverter, all of which are insensitive to the dimming resolution in contrast to a conventional codeword-table method. This paper describes the verification of the proposed algorithm through a register-transfer level implementation of the codeword and proposed architectures. In comparison with the codeword-table method, the proposed method gains a nine-fold complexity reduction at a 1% dimming-step resolution.

• Radiation Oncology Journal
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• v.12 no.1
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• pp.117-121
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• 1994

In spite of remarkable improvement of surgical skills and anesthesia, local failure still occurred in 36-45$ \% $ of locally advanced colorectal cancer after curative resection with or without pre-or post-operative irradiation. Intraoperative radiation therapy(IORT) is the ideal modality which resectable lesions are removed surgically 3nd the remaining cancer nests are sterilized by irradiation during a surgical procedure. Therefore, the excellent local control without the damage of the adjacent normal tissues can be achieved. In IORT, judicious set up of the treatment cone on the treatment surface of the patient is required for accurate and homogenous dose distribution within treatment field, especially on the slopping surface of sacrum and pelvic sidewall which are the common sites of the local recurrence in rectal cancer. For this purpose, adequate co-ordination of gantry rotation and table tilting are essential. Adjusting gantry rotation is not difficult but tilting of the table is impossible inconventional treatment couch. Department of Therapeutic Radiology in Yeungnam University Medical Center developed the IORT table for colorectal cancer which is easy to set up and detach on the Linac treatment couch within 5 minutes. The range of tilting with head-up and head-down is about 30 degree which is efficient and easy-to-use, not only for IORT but also for colorectal surgery. So far, authors performed IORT with newly developed treatment table in 2 patients with rectal cancer and we found that this newly developed table could contribute in improving the dose distribution of IORT and surgical procedure for colorectal cancer.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 2008.03a
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• pp.164-164
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• 2008

The beach-chair traction position is designed to allow the use of traction while allowing the surgeon to orient the shoulder in an upright position and convert to an open procedure, if necessary. The patient is placed in the beach-chair position under general anesthesia. A three-point shoulder holder (Arthrex, Naples, Florida) is attached to the rail of the operating table on the same side as the surgeon, whereas it is placed on the side opposite the surgeon in the lateral decubitus position. A shoulder traction and rotation sleeve (Arthrex) are affixed to the arm following the manufacturer's instructions. Positioning the thumb toward the closed side of the sleeve ensures a field for the anterior portion of the rotator cuff and prevents the tendency of the suspension apparatus to place the arm in internal rotation. The arm is maintained in 30 to 40 degree abduction and 30 to 40 degree flexion by controlling the length and height of the bar and the location of the universal clamp. The universal clamp allows multiple planes of adjustment to control abduction and forward movement of the arm. The sleeve is attached to the longitudinal traction cable using a sterile hook, and a lateral strap is secured around the proximal portion of the sleeve to the overhead traction cable to ensure a field for glenohumeral reconstruction. The use of a lateral strap permits ideal shoulder positioning for improved access to the anterior and inferior glenohumeral joint. The lateral strap can be released or removed to widen the subacromial space during subacromial decompression or rotator cuff repair. A 10-lb weight is attached to the longitudinal traction cable for an average-sized person.

• Journal of radiological science and technology
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• v.34 no.4
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• pp.277-285
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• 2011

To determine the quality control of UGIS, we acquired 105 patients sampling image at 21 general screening centers. The results of image quality evaluation table containing two countries's UGIS showed that the mean of image qualified education table of our country was 73.3 and the standard error was 4.49; In addition, 19 organizations of 21 general screening centers were given appropriate judgement. The average of image qualified education table of Japan was 58 and the standard error was 4.45. Only 8 organizations were given appropriate judgement. Although we made the image quality evaluation tables with same images, there were many differences in the result of two tables. We figured out the problem about the description of whole stomach and photograph skills. Furthermore, we analysed the situation of the UGIS at each general screening center with the acquired images. The biggest problem of the UGIS of our country was that the procedures were performed without clear medical methods. Methods of UGIS were different at every 21 general screening centers, and most of them did not take exam of anterior surface of stomach of the UGIS. In addition, some general screening centers did not include mucosal relief method or esophagography which is required to include in the image qualified education table of our country. Because polisography is used in the same body position, the problem occured about indiscreet exposure dose of patients. Therefore we have to make an effort to get X-ray images which have enough diagnosis information by the quality control of UGIS.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.120-130
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• 1999

In this paper, we show that the instantaneous phase current of the bifiler-wound hybrid stepping motor is dependent of lead angle and that the information of motor position is obtained from the instantaneous phase current at ${\pi}/2$ by the theoretical formular and its computer simulation results. From the facts, we design the microcontroller-based motor position sensorless controller of optimal lead angle, which generates the excitation pulses for the closed-loop drives. The controller is consist of microcontroller which has the function of A/D converter, programmable input/output timer, and the transfer table which has the values of optimal lead angle depending on motor velocity, and ROM which has the transfer table of the values of lead angle depending on velocity of motor and the values of instantaneous phase current at ${\pi}/2$. From the design of microcontroller-based controller, we minimize the external interface circuit and obtain flexibility by changing the contents of ROM transfer tables and the control software. We confirm that the designed controller drives the bifilar-wound hybrid stepping motor is the mode of optimal lead angle by comparing the instananeous phase current experimental results and computer simulation results.