• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.353-362
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• 1993

The purpose of this study is to develop a crop-row detector which can be applied to an automatic row following control for cultivators or thinning machines. In this report, a possibility of new crop-row detecting method was discussed. This detecting method consists of two principal means. One is the hardware means to convert the two dimensional crop-row vision to the compacted one dimensional information. The conversion is achieved by a color line sensor and a rotating mirror. In order to extract crop-row , R and G signals of RGB color system are used. The locations of two different points on the target row are detected by this means. Another is the software means to estimate the offset value and the heading angle between the detector and the target row which can be assumed as a straight line. As a result of discussion, it was concluded that this detecting method would be accurate enough for practical use.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.99-100
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• 2002

Radial, tilting-pad proceeding bearings are applied in high speed rotating machines operating at stable small and mean loads and the peripheral speeds of proceeding reaching 150 m/s. The operation of bearing can be determined by static characteristics including the oil film pressure, temperature and viscosity distributions, minimum oil film thickness, load capacity, power loss, oil flow. The operation of 5-lobe tilted-pad proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions habe received by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss. oil flow, maximum oil film pressure, maximum temperature were computed for different sets of bearing geometric parameters as: bearing length to diameter ratio, pad angular length and width as well as pad relative clearance.

• Progress in Superconductivity and Cryogenics
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• v.10 no.2
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• pp.1-11
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• 2008

The application of bulk superconducting materials to electrical power systems is very attractive because bulk high temperature superconductors offer excellent electromagnetic properties. In recent years there has been significant progresses in the research and fabrication of superconducting bulk materials. Numerous efforts have been made worldwide to make bulk YBCO as a replacement of the conventional magnets to produce larger magnetic field and hence to improve the device performance in electrical power applications. This paper gives a comprehensive review of different applications of bulk HTS materials, concentrating in three areas including superconducting bearing, superconducting motors and high field magnets. The advantages of applying superconducting material into each application are analysed. The status of current research in each section is summarized and examples are given to demonstrate how YBCO bulk materials can benefit the design of electrical devices. Several numerical models which calculate the electromagnetic properties of bulk superconductors are introduced and finally the article concludes with a review on the studies of the demagnetisation effect in superconducting bulk magnets which is extremely relevant to applying superconducting technology to rotating machines.

• Journal of the Korean Institute of Gas
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• v.28 no.2
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• pp.93-104
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• 2024

Facility diagnosis is essential for the smooth operation and life extension of rotating equipment used in industrial sites. Compared to other diagnostic methods, vibration diagnosis can find most of the initial defects, such as unbalance, alignment failure, bearing defects and resonance, compared to other diagnostic methods. Therefore, vibration analysis is the most commonly used facility diagnosis method in industrial sites, and is usefully used as a predictive preservation (PdM) technology to manage the condition of the facility. However, since the vibration diagnosis method is performed based on experience based on the standard, it is carried out by experts. Therefore, it is intended to contribute to the reliability of the facility by establishing a system that anyone can easily judge defects by establishing a vibration diagnosis method performed based on experience as a knowledgeable code system. An algorithm was developed based on the ISO-20816 standard for vibration measurement, and the reliability was verified by comparing the results of vibration measurement at various demonstration sites such as petrochemical plant compressors, hydrogen charging stations, and industrial machinery with the results of analysis using a development system. The developed algorithm can contribute to predictive maintenance (PdM) technology that anyone can diagnose the condition of the rotating machine at industrial sites and identify defects early to replace parts at the exact time of replacement. Furthermore, it is expected that it will contribute to reducing maintenance costs and downtime due to the failure of rotating machines when applied to various industrial sites such as oil refining facilities, transportation, production facilities, and aviation facilities.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.433-445
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• 2014

Single phase voltage source converter (VSC) is an important power electronic converter (PEC), including single-phase voltage source inverter (VSI), single-phase voltage source rectifier (VSR), single-phase active power filter (APF) and single-phase grid-connection inverter (GCI). As the fundamental part of large scale PECs, single-phase VSC has a wide range of applications. In the paper, as first, on the basis of the concept of the discontinuous pulse-width modulation (DPWM) for three-phase VSC, a new DPWM of single-phase VSR is presented by means of zero-sequence component injection. Then, the transformation from stationary frame (abc) to rotating frame (dq) is designed after reconstructing the other orthogonal current by means of one order all-pass filter. Finally, the presented DPWM based single-phase VSR is established analyzed and simulated by means of MATLAB/SIMULINK. In addition, the DPWMs presented by D. Grahame Holmes and Thomas Lipo are discussed and simulated in brief. Obviously, the presented DPWM can also be used for single-phase VSI, GCI and APF. The simulation results show the validation of the above modulation algorithm, and the DPWM based single-phase VSR has reduced power loss and increased efficiency.

• Journal of Biosystems Engineering
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• v.35 no.3
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• pp.163-168
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• 2010

With income growth and "well-being" trends, sales of corn has been increased recently. Corns are processed at processing facilities on the main production site. Corn processing steps include removing bract, steaming, vacuum packing, and storing. To replace manual corn bract removing, some bract removing machines were imported and used. However, the machines were abandoned shortly, because of high damaging ratio of corns. In this research, factors of successful bract removing was studied with rotating rollers and air-injection nozzles to develop corn bract removing system. The test device was composed of a cylindrical roller, an air spray nozzle, a regulator, and a motor. Designing factors were roller type, diameter of air spraying nozzle, spraying angle, and spraying pressure. The measured factors were bract removing rate and damaging rate. It was found that optimum cylindrical roller surface shape was cylindrical roller and linear grove roller. This roller shape produced lowest damaging rate. Test results of the efficacy of preprocessing showed that the air spraying after preprocessing produced highest performance. The rotational speed and inclination of the roller didn't affect the bract removing performance. Optimum injection angle of the air jet nozzle was $70^{\circ}$. To increase bract removing rate and to reduce corn damage, required injection pressure and injection nozzle diameter were decided to less than 0.4 MPa and 2.5 mm, respectively. More than 3 times of nozzle passing produced good bract removing performance and there were no significant difference between the number of passing times.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.285-291
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• 2011

The error motion of a machine tool spindle directly affects the surface errors of machined parts. The error motions of the spindle are not desired errors in the three linear direction motions and two rotating motions. Those are usually due to the imperfect of bearings, stiffness of spindle, assembly errors, external force or unbalance of rotors. The error motions of the spindle have been needed to be decreased to desired goal of spindle's performance. The level of error motion is needed to be estimated during the design and assembly process of the spindle. In this paper, the estimation method for the five degree of freedom (5 D.O.F) error motions of the spindle is suggested. To estimate the error motions of the spindle, waviness of shaft and bearings, external force model was used as input data. And, the estimation models are considering geometric relationship and force equilibrium of the five degree of the freedom. To calculate error motions of the spindle, not only imperfection of the shaft, bearings, such as rolling element bearing, hydrostatic bearing, and aerostatic bearing, but also driving elements such as worm, pulley, and direct driving motor systems, were considered.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.199-206
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• 2006

Automatic grease lubricator is equipment that provides adequate amount of fresh grease constantly to the shaft and the bearings of machines. It minimizes the friction heat and reduces the friction loss of machines to the least. This research is to develop automatic grease lubricator by gear driven mechanism with controlled operation time. The ultimate design of this equipment is to lubricate an adequate amount of grease by a simple switch clicking according to the advanced set cycle. The backlash of the gear was minimized to increase the output power. To increase the power of gear mechanism, the binding frequency and the thickness of the coil were changed. To control the rotating cycles of the main shaft according to its set numbers, different resistance and chips were used to design the circuit to controls electrical signals with pulse. The body of the lubricator was analyzed by stress analysis with different constructed angle. The stress analysis for differing loading pressures applied to the exterior body of grease lubricator due to the setup angle, was found that the maximum stress was distributed over the outlet part where the grease lubricator suddenly narrowed contracts. Digital mock-up was analyzed and the rapid prototyping(RP) trial products were tested with PCB circuit and grease. The evaluation of the outlet capacity for RP trial products was conducted, because the friction caused by the outlet on the wall surface was an important factor in the operation of the equipment. Finally, the finishing process was applied to decrease the roughness of the surface to a comparable level and was able to test the performance examination for the product.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1009-1017
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• 2010

As rotating machines play an important role in industrial applications such as aeronautical, naval and automotive industries, many researchers have developed various condition monitoring system and fault diagnosis system by applying various techniques such as signal processing and pattern recognition. Recently, fault diagnosis systems using artificial neural network have been proposed. For effective fault diagnosis, this paper used MLP(multi-layer perceptron) network which is widely used in pattern classification. Since using obtained signals without preprocessing as inputs of neural network can decrease performance of fault classification, it is very important to extract significant features of captured signals and to apply suitable features into diagnosis system according to the kinds of obtained signals. Therefore, this paper proposes the decision method of the proper feature vectors about each fault signal for neural-network-based fault diagnosis system. We applied LPC coefficients, maximum magnitudes of each spectral section in FFT and RMS(root mean square) and variance of wavelet coefficients as feature vectors and selected appropriate feature vectors as comparing error ratios of fault diagnosis for sound, vibration and current fault signals. From experiment results, LPC coefficients and maximum magnitudes of each spectral section showed 100 % diagnosis ratios for each fault and the method using wavelet coefficients had noise-robust characteristic.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.346-353
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• 2022

Recently, studies on the integrity of rotating machines, such as gantry cranes, which are used in the shipbuilding industry, have been actively conducted. Gantry cranes are driven at relatively low revolutions per minute (RPM), are frequently operated and stopped, and are impacted by external environmental factors, such as shock and noise in the measurement data. The purpose of this study was to construct a replica of a gantry crane hoist used in indoor shipbuilding and analyze the acquired data for errors caused by the shift in operating conditions (RPM) and the change in the position of the data acquisition sensor. Consequently, we observed that the error caused by differences in sensor positions did not occur significantly under low operating conditions but occurred significantly under relatively high operating conditions. Thus, we determined that both the operating condition and position of the acquisition sensor affected the data acquired by the rotary machine.