Earticle

본 논문에서는 Latch-up 면역과 우수한 면적 효율성을 갖는 고전압용 ESD 보호회로를 제안한다. 제안된 회로는 기존의 SCR에 대하여 플로팅 영역 삽입과 세그먼트 레이아웃 기법을 적용함에 따라 매우 높은 홀딩 전압을 갖는다. 제안된 ESD 보호회로는 세그먼트 레이아웃 기법을 이용하여 높은 면적 효율을 지닌다. 제안된 소자는 일반적인 SCR의 3.39V의 홀딩 전압과 비교하여 21.67V의 높은 홀딩 전압을 가진다. 제안된 소자의 전기적 특성은 Synopsys사의 TCAD를 통해 검증하였으며, 0.18 BCD 공정을 이용한 실제 제작을 통해 증명하였다.

This paper proposed the ESD protection circuit for the high-voltage applications with latch-up immunity and high area efficiency. The proposed circuit has high holding voltage compared to the conventional SCR by inserting the floating regions and applying the segmentation layout. It has the area efficiency is more higher due to the segmentation layout. The proposed circuit has the higher holding voltage of the 21.67V than the 3.39V of the conventional SCR. The electrical characteristics of the proposed circuit was investigated by TCAD simulator, and was proved through the fabrication by using the 0.18 BCD process.

본 논문에서는 향상된 전기적 특성과 면적효율을 갖는 새로운 구조의 ESD 보호회로를 제안한다. 제안된 회로는 기존의 3-STACK LVTSCR과 비교하여 높은 홀딩전압과 낮은 트리거전압 특성, 향상된 Ron 저항 특성을 갖는다. 제안된 ESD 보호회로는 기존 보호회로 대비 35% 정도의 작은 면적, 35V의 트리거 전압과 8.5V의 홀딩전압을 갖는다. 또한 제안된 ESD 보호회로의 래치-업 면역특성을 향상시키기 위해 기생 바이폴라 트랜지스터들의 유효 베이스 길이를 설계변수로 설정하여 설계하였고 시놉시스사의 TCAD 시뮬레이션을 통하여 제안된 ESD 보호회로를 검증하고 전기적 분석을 실행하였다.

This paper presents the ESD protection circuit with improved electrical characteristic and area efficiency. The proposed ESD protection circuit has higher holding voltage and lower trigger voltage characteristics than the 3-Stacking LVTSCR. In addition, it has only two stages and has improved Ron characteristics due to short discharge path of ESD current. We analyzed the electrical characteristics of the proposed ESD protection circuit by TCAD simulator. The proposed ESD protection circuit has a small area of about 35% compared with 3-Stacking LVTSCR, The proposed circuit is designed to have improved latch-up immunity by setting the effective base length of two NPN parasitic bipolar transistors as a variable.

This study was performed to investigate the effects of inertial navigation system (INS) / global positioning system (GPS) sensor fusion for agricultural vehicle navigation. An extended Kalman filter algorithm was adopted for INS/GPS sensor fusion in an integrated mode, and the vehicle dynamic model was used instead of the navigation state error model. The INS/GPS system was consisted of a low-cost gyroscope, an odometer and a GPS receiver, and its performance was tested through computer simulations. When measurement noises of GPS receiver were 10, 1.0, 0.5, and 0.2 m ($1{\sigma}$), RMS position and heading errors of INS/GPS system at 5 m/s straight path were remarkably reduced with 10%, 35%, 40%, and 60% of those obtained from the GPS receiver, respectively. The decrease of position and heading errors by using INS/GPS rather than stand-alone GPS can provide more stable steering of agricultural equipments. Therefore, the low-cost INS/GPS system using the extended Kalman filter algorithm may enable the self-autonomous navigation to meet required performance like stable steering or more less position errors even in slow-speed operation.

This study was performed to design and construct a digital soil shear stress sensor in order to replace the conventional devices for measuring soil shear property. The developed digital shear stress measuring device can store measured data with GPS position information as a vector format into a computer. Based on the experiments at various field conditions, the measuring characteristic of the device was quite similar to that of a conventional device, SR-2 that has been a major tool to measure the soil shear property. It was concluded that the digital shear stress measuring device was an effective and comprehensive sensor for measuring soil shear property.

Based on the profiles of cone index with depth, physical properties of hardpan in selected rice fields were measured and analyzed in the study. An error correction algorithm removing a random measurement error from raw CI profile data was introduced in the study. The properties of hardpan included the shape, the thickness and the rice root growing layer. The analysis of physical properties of hardpan in the rice fields showed that the type of hardpan could be classified into 6 categories. The thickness of hardpan ranged from 6 cm up to 41 cm and the average hardness of hardpan was analyzed to be from 1.1 MPa through 3.2 MPa in Cone index.

In the study, the cone index, the cohesion and the internal friction angle of soil were measured before and after tillage in order to suggest relative improvement in soil properties by comparing the two measured values before and after tillage. The tillage methods tested in the study were five combinations of plowing and rotovating; one plow tillage operation, one plow followed by one rotary, one plow followed by two rotary, one rotary without plow and two rotary without plow. The experiments were performed in a soil bin in Sunggyunkwan Univ. and in four selected test fields in Yeoju, Seodun-Dong, Suwon (especially, two different fields) and Chungju. In general, the internal friction angle and cohesion of soil increased with the increase of soil compaction. After applying the tillage operations, the internal friction angle reduced by 14 degree and the cohesion decreased up to about $2.2N/cm^2$ on the soil bin in comparison with those before tillage. The two values, however, reduced by 9 degree and up to about $1.0N/cm^2$ on the tested fields. The CIs for all the tillage operations on the soil bin and on 4 different test fields were decreased by 800 kPa in comparison with those before tillage. The best combination of tillage operations for decreasing the CIs of soil was one plow operation followed by one rotary. The CIs for one plow operation followed by two rotary were slightly higher than that for one plow operation followed by one rotary because one plow operation followed by two rotary crushed down the soil excessively, so that the porosity of soil decreased.

A 5-row walking garlic harvester with pulling mechanism was developed in the study, based upon a kinematical analysis and related preliminary field tests on the conventional garlic harvesting method. The harvesting efficiency of the developed harvester was more than 98% in the garlic field irrigated before harvesting, 80-85% in the field without irrigation. The harvesting performance of the harvester was 660∼825㎡/hr at the forward speed of harvester of 0.3m/s in the irrigated field before garlic harvesting. For proper garlic drying and collection, the harvester discharged the harvested garlic on the ground uniformly at the angles of 135。∼150。 to its forward direction with the garlic bulb's placing toward the harvester. In the field tests, it was recommended that the forward speed of the harvester be approximately less than 0.2m/s, and that the spacing of planting garlic seeds should be standardized in the future fur increasing its harvesting efficiency.

Traction performance of off-road vehicles is estimated using slip-traction relationships Two zero condition accepted by ASAE have been used widely to obtain the slip-traction relationships of off-road vehicles. This study was carried out using the soil bin systems to investigate the characteristic of slip-traction curves obtained using two zero conditions defined by ASAE. which are driving and driven zero condition, and to present disadvantage of slip-traction relationship based on two zero conditions of ASAE. The results of this study are summarized as follows : 1. For the driving zero condition, the curve of slip-traction relationship shows some issues. The first question is that the slip is zero when the traction is zero. The second question is that the value of slip is smaller than that of corresponding real slip, as the rolling radius decreased f3r the setting zero condition with driving wheel. 2. For the driven zero condition. slip occurs when the traction is zero, which is more realistic results than driving zero condition. But when a zero condition is set, skid occurs and this result increased the rolling radius of tire and increased slip value f3r the specific traction value of whole slip range. This kind of trend was getting bigger as the soil is softer, or the tire inflation pressure is higher. 3. From the results of this study, it was found that slip-traction relationship obtained by two zero conditions of ASAE is not realistic in estimating the traction performance of off-road vehicles. And also slip-traction relationship obtained for the same experimental condition showed different result in accordance with chosen zero condition,

This study was conducted to develop the mathmatical model for predicting the side thrust which is generated by the shearing action on the vertical surfaces of the sides of the track. Experiments were conducted with the three different shear plates with grouser length of 1, 3 and 5 cm for two different soil condition using soil bin system. The measured side thrust were compared with the values predicted by the new model developed in this study and by Bekker's model respectively. The values of side thrust predicted by the new model were more close to the measured values than those of the side thrust predicted by Bekker's model . The total thrust measured were also compared with the values predicted by the conventional model which considers only bottom thrust effect and by the new model which contains not only bottom thurst but side thrust effect. The values of the thrust predicted by conventional modelwere lower than measured values for both of the soil conditions and the three levels of grouser length. The maximum errors of conventional model were increased with the increase of grouser length. but the values of the total thrust predicted by the model developed in this study were well matched to the measured ones for both of the soil conditions and the three levels of grouser lengths.

In this study, the physical properties of live garlic at the harvesting season were measured and analyzed as a fundamental study for developing a garlic harvester. A universal testing machine and a machine vision system were used to obtain mechanical and morphological properties of live garlic, respectively. The moisture content of live garlic at the harvesting season was 50% higher than that of dried garlic. The root of live garlic elongated greatly with respect to the applied tensile force. The relationship between the projected area and the weight of a bulb of live garlic was linear. Such a feature would be applied to develop an effective garlic harvester or garlic quality grader. Other useful physical properties of live garlic at the harvesting season were represented in the study.

This study was performed as a basic research for establishing an objective quality evaluation method on whole bulbs of garlic. The size of a whole bulb of garlic, the number and the uniformity of complete individual garlics, and the existence of bad individual garlics in the whole bulb of garlic were selected as quality grading factors. Quality discrimination algorithms with machine vision techniques were developed and verified for the four factors based on morphological and physical features of whole bulbs of garlic. Based on the results, the size discrimination by the projected area of a whole bulbs of garlic suggested four grading levels and the algorithm for predicting the number of complete individual garlics based on the peaks on its projected boundary showed ${\pm}$0.78 prediction error. In addition, the uniformity represented by coefficient of variation could be divided into four levels, but the algorithm for discriminating the existence of bad individual garlics in a whole bulb of garlic was not effective.

인발식 마늘 수확기의 기본개념은 마늘줄기가 인발 가이드를 따라 마늘줄기 인발부로 안내되어 지면 상방향으로 인발, 이송되는 방식으로서 인력에 의한 마늘수확 메카니즘과 유사하다. 그러나 수확기가 전진함에 따라 마늘이 연속적으로 인발되어 인력작업에 비해 매우 높은 수확능률을 갖는다. 또한 굴취식 수확기와 비교하여 연료가 절감되고 통마늘의 손상이 적은 장점이 있다. (중략)

현재까지 마늘 생산의 생력기계화 작업체계는 확립되어 있지 않으며, 특히 마늘의 수확은 많은 노동력을 필요로 하여 마늘 생산비에 수확비용이 차지하는 비중은 매우 높다. 따라서 마늘 수확의 생력화를 위해 마늘수확기 개발이 시급한 실정이다. 마늘수확기의 개발을 위해 분석, 구명되어야 할 중요한 인자는 수확기의 소모동력, 작업성능, 메커니즘의 간결성과 편리성, 수확효율 및 수확후 처리 등에 관계되는 모든 인자들이 포함된다. 나아가 마늘수확기에 고려되어야 할 주요 작동부는 동력발생부, 동력전달부, 마늘수확부 및 이송부, 마늘 수확을 위한 전처리부 및 후처리부, 마늘수확기 운행에 필요한 운전부 등으로 나눌 수 있다. (중략)

A dynamometer was designed and constructed to measure three directional forces and moments of pull type implement with eliminating the interference between the forces. The dynamometer consists of a linear motion bearing, self-aligning bearings, universal joints, and cantilevers where strain gages were attached. A data acuquisition system was developed to collect data and to analyze them. The data acuquisition system consists of the dynamometer, a potentiometer to measure the implement depth, strain amplifiers, a A/D converter, and an IBM-AT compatible microcomputer. Program, written in C language, was developed to read data from tranducers with given interval, to calculate forces and moments, to display them on screen, and to store them on disk. The calibration results showed that cantilevers had good linearity and there was no interference among directional forces. When applied loads were reduced with constant rate, hysteresis was appeared on the dynamometer. It might to be reduced by using ball bearings instead of self-aligning bearings.

This study was attempted to develop the electronic-hydraulic hitch control system for position control of tractor plow and investigate the control performance of the system through experiments. Experiments were carried out to investigate the responses of the system to the step and sinusoidal inputs in position control. The effects of control mode, hydraulic flow rate, reference deadband, and proportional constant on control performance of the system were investigated. The following conclusions were derived from the study; 1. For the position control system operated on on-off control mode, positions of implement were controlled within ${\pm}0.73^{\circ}{\sim}{\pm}1.46^{\circ}$ in rockshaft angle to the reference position when the hydraulic flow rates were 5~15 l/min. For the position control system operated on PWM control mode, positions of implement were controlled within ${\pm}0.73^{\circ}$ to the reference position regardless of hydraulic flow rates. It means that the implement could be positioned more accurately to the reference position on PWM control mode than on on-off control mode. 2. As results of the frequency responses of the position control systems, no clear difference in control performance between on-off control and PWM control modes was found. As the hydraulic flow rates increased, the corner frequencies of amplitude attenuation and phase-angle change increased. It means that the control performance of the system could be improved as the hydraulic flow rate increases.

The performance of a vertical type centrifugal distributor of granular materials was studied by means of mathematical models and experimental investigations. To develop the mathematical description of particle motion, some assumptions were made. The distribution process consisted of three stages: the entrance of a particle to the blade, the motion of the particle on the blade, and the motion of the particle in the air. The physical properties of fertilizer, which affected the particle motion, were investigated: bluk density, coefficient of friction, coefficient of restitution, and particle size distribution. The particle motion were simulated by using a computer. A prototype distributor was designed and constructed for experimental tests. The following conclusions were drawn from the computer simulation and experiment results. 1. The fertilizer may slide or roll at the point of contact when they impact on the blade and move along the blade. 2. The interaction among fertilizers may prevent them from bouncing. 3. When fertilizers roll on the blade, rolling resistance is one of the factors affecting the particle's motion. 4. The trajectory angle and position of fertilizers from a disc depend on the blade position and particle shape, but the rotating speed of the disc affected them only slightly.

This study was carried out to find a method which can be used to measure the soil moisture content of the soil bin exactly and quickly. And gypsum block is used as an instrument in measuring soil moisture content in the field of green house farming, etc.. However the characteristics of gypsum block, or the guide line of making gypsum block is not well introduced in Korea. So the information about gypsum block such as the density of gypsum, type of electrode, dimension of electrode, distance between electrodes, density of surrounding soil were included in this study and their effects on the relationship between soil moisture content and electrical resistance were investigated. The results of this study are as follows; 1. The grid type electrode was quicker in accessing the equilibrium condition and showed more sensitive response to the change of soil moisture content than the plate type electrode. 2. The longer the distance between the electrodes, the larger the electrical resistance, and the distance of 3 to 5 mm was recommended. 3. The larger the width of the electrode, the smaller the electrical resistance. However, there was no significance between the levels designed in this study. Considering the size of the gypsum block itself, the adaptible range of width may be 4 to 8 mm. 4. The higher the density of gypsum, the smaller the electrical resistance. And the block of lower density was broken down in the soil of higy moisture content. The optimum ratio of gypsum to water was 7:5. 5. The measuring system used in this study allowed simultaneous, multi-data acquisition. So this system using A/D converter can be applied to the measurement of soil moisture content of soil bin.

This study was carried out to determine the optimum size and number of farm machines for various sizes of land coverage of the cooperative farm machinery utilization systems in Korea-namely Saemaul Mechanized Farming Group (SMFG). Fifty-one SMFG were selected from 8 counties in Chonnam province, and ownership, operation and management of farm machinery were surveyed. Annual covered area, cost and the break-even-point area of farm machinery were analyzed on the bases of the surveyed data and the present governmental subsidy policy, and then the optimum level of farm machinery ownership was determined. The results are summarized as follows: 1. The break-even-point areas of the tractors of 22-23ps, 28ps and 47-50ps were estimated as 12.1ha, 15.3ha and 21.6ha, respectively. The optimum size of a tractor for land sizes of 10-20ha, 20-30ha, and 30-40ha were estimated as 22-23ps, 28ps, and 47-50ps, respectively. 2. The break-even-point area of a rice transplanter was estimated as 3.3ha. The optimum numbers of rice transplanter for land sizes of 10-20ha, 20-30ha, and 30-40ha were estimated as 2,3, and 4, respectively. 3. The break-even-point areas of a speed sprayer (attached on power tiller) and a power sprayer were estimated as 114.6ha and 15.3ha, respectively. The optimum numbers of power sprayer for land sizes of 10-20ha, 20-30ha, and 30-40ha were estimated as 2,3 and 4, respectively. A speed sprayer is desirable for an area of more than 30ha coverage. 4. The break-even-point area of a combine was estimated as 10.7ha. The optimum numbers of combine for land sizes of 10-20ha, 20-30ha, and 30-40ha were estimated as 1,2, and 3, respectively.