• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.356-361
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• 2008

The conventional drive system of SRM has a current sensor per each phase. The torque demand signal generated by the outer control loop is translated into individual current reference signal for each phase. The torque is controlled by regulating these currents. Using the SRM in a variable-speed control, the phase currents are generally regulated to achieve a square wave. The simplest form of current regulation uses fixed frequency delta modulation of the phase voltages. The aim of this paper is to regulate 3-phases current of SRM by only single current sensor using delta modulation with digital chip. In this paper, the asymmetric bridge converter which is able to control independently phases and be excited simultaneously is used as the driver system for 6/4 poles SRM. And the current sensor is replaced 3 sensors of each phase with only one on bus line of converter so as to detect current of every phase. The proposed delta modulation technique has been implemented in a simple digital logic circuit using EPLD(Electrically Programmable Logic Device). This method is verified through simulation and experiment results.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.38-43
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• 2008

The usage of electric forklift truck is gradually increasing due to the convenience at conveying and arranging the materials in the industrial field. In this study, the author designed and suggested the optimum driving system and load tester which both of them are the most important part of the forklift truck. The planetary gear is chose to driving system because it makes big power even though the motor size is small. The gear teeth of planetary gear were designed and the designed planetary gear was tested considering the yield strength and the abrasion of gear teeth. The B-Type electric brake which consists of multiple plates and operates with non-magnetic type was connected with a single shaft in the driving system. So, it can be applied at the sudden braking situation which has the torque increment. And it has the compact size and excellent durability Load tester can give the various levels of load to the planetary gear of driving system in the electric forklift truck and it can also measure the levels of the load which were applied. Therefore, we can measure the noise, torque and perform the durability, vibration tests using load tester. It will be economical because many kinds of test can be performed using reasonable priced load tester The driving system of electric forklift truck which has sufficient competitive can be manufactured using our designed planetary gear reducer with reasonable price. The designed load tester can use for checking the performance of other reducers, as well.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.19 no.1
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• pp.17-24
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• 1983

The authors carried out an experiment to find the optomotor response of killifish, Orizias latipes(TEMMINCK et SCHLEGEL) and Yellowtail, Seriola quinqueradiata (TEMMINCK et SCHLEGEL) according to the colors of the netting pattern on the visual screen and the revolving velocities of the visual screen. The experimental water tank was made of 0.5 cm thick transparent acryl in the cylindrical shape (100R$\times$42H cm). The water level in the tank was maintained 30cm high from the bottom. The colors of the netting pattern (mesh size: 19.1cm, width of netting twine: 1.5cm, hanging ratio: 84%) on the three visual screens were black, red and green respectively. The revolving velocities of the visual screen were controlled by pulley, bevel gear and variable speed motor in three steps; slow (15.0cm/sec), middle (37.4cm/sec) and high (62.9cm/sec). The fish was put into the water tank before each experiment and released in it for 30 minutes in order to acclimatize itself to the tank. The visual screen was revolved for 4 minutes per each experiment, at first the fish was released for 1 minute, and then the behavior of the fish was observed for 3 minutes. In the course of clockwise and counter clockwise experiments, 10 minutes-pause was given for the rest. The behavior of the fish was observed by video system, and rounding number and swimming speed of the fish were analysed. The results obtained are as follows: (1) Optomotor response rate of Killifish and yellowtail were 95% and 94% respectively. (2) Response of the fish according to the colors of the netting pattern on the three visual screens was best in black, and second in red and third in green. (3) Response of the fish according to the revolving velocities of the visual screen was best in high speed, and second in middle speed and third in slow speed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.455-464
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• 2019

The sensorless control based on the flux linkage of PM synchronous motors has excellent position estimation characteristics at low speeds. However, a limitation arises because the integrator of flux estimator is saturated by the DC offset generated during the analog to digital conversion(ADC) process of the measured current. In order to overcome this limitation, HPF with a low cutoff frequency is used. However, the estimation performance is deteriorated (Ed- the verb deteriorate already includes the meaning of 'problem') at high speed due to the low cutoff frequency, and increasing the cutoff frequency of the HPF induces further problems of phase leading and initial starting failure at low speeds. In this paper, the cutoff frequency of HPF was synchronized to the operation frequency of the motor: at low speeds the cutoff frequency was set to low in order to reduce the phase leading of the estimated flux, and at high speeds it was set to high to raise the DC offset removal performance. As a result, the operating range was increased by 200%. Furthermore, a phase compensation algorithm is proposed to reduce the phase leading of the HPF to less than 1.5 degrees over the full operating range. The proposed sensorless control algorithm was verified by experiment with a PM synchronous motor for a washing machine.

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.477-484
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• 2006

The purposes of this study were to compare the apical terminus width of simulated curved root canal prepared with three NiTi file systems used by undergraduates for evaluation the effects of flute angle and pitch or radial land on reducing screw-in effect and to determine more safe NiTi file system for inexperienced operators. Fifty inexperienced undergraduate students prepared 150 simulated curved root canals in resin blocks with three NiTi file systems ; ProFile$^{(R)}$, Hero Shaper$^{(R)}$, K3$^{TM}$. The electric motor set at a speed of 300 rpm and torque of 30 in a 16 : 1 reduction handpiece was used. The simulated root canal was prepared to ISO #25 sizes with each file system. The scanned images of pre- and post-instrumented canal of resin block were superimposed. To evaluate the screw-in effect of three NiTi file systems, apical terminus width of root canal was measured from superimposed images and statistical analysis was performed. There were significant differences in three NiTi flle systems. ProFile$^{(R)}$ had significantly smaller width than Hero Shaper$^{(R)}$ and K3$^{TM}$"" (P < 0.05), but no significant difference was observed between K3$^{TM}$ and Hero Shaper$^{(R)}$. Under the condition of this study, active file system (Hero SHaper$^{(R)}$, K3$^{TM}$) with variable pitch and helical angle had more screw-in effect than passive file system (ProFile$^{(R)}$) with constant pitch and helical angle. It seems that the radial lands play more important role in reducing screw-in effect.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.159-164
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• 2001

An extensive range of pumping facilities are employed in the regional water supply system in metropolitan areas, and optimization and the systematic combination of the pump facilities have direct bearing on the stability and economy of the water supply system concerned. These systems must be able to guarantee stability, efficiency and offer high reliability. Preparation of metropolitan area regional water supply system construction project must include a basic plan which takes into account the suitability of pumping facilities to be used, the environment in which facilities will be installed, man-power requirements and basic operational and management policies. This paper contains over-all analysis of the management of metropolitan area regional water supply systems and highlights the cause of Inefficiency and energy waste and puts forward a remedial plan of action. In addition, pump/motor specification programs were developed using Visual Basic to assist selection of the same.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.26-33
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• 2017

We propose a variable frame structure connected with telescopic mast-shaped shaft for a robot displaying outstanding ability to cross obstacles, and for effective traction control. The wireless control system was built to extend and contract a deployable mechanism, which is shaped into a hoberman sphere assembled with frame structures. In order to develop important parameters for efficient locomotion, we derived an Euler-Lagrange equation for the spherical robot. According to the equation, the DC motor was selected. A prototype mechanism was tested and a Finite-Element Analysis (FEA) was conducted in parallel. Using these data, we constructed a deployable spherical robot with structural stability. The deployable robot moved at a speed of 0.85 m/s from 520 mm to 650 mm.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.1
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• pp.1-9
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• 2019

In electric agricultural machine the gearbox is used to increase torque and lower the output speed of the motor shaft. The gearbox consists of several shafts, helical gears and spur gears works in series. Optimization plays an important role in gear design as reducing the weight or volume of a gear set will increase its service life and improve the bearing capacity. In this paper the basic design parameters for gear like shaft diameter and face width are considered as the input variables. The bending stress and material volume is considered as the objective function. ANSYS was used to investigate the bending stress when the variable was changed. Artificial Neural Network (ANN) was used to obtain the mathematical model of the system based on the bending stress behaviour. The ANN was used since the output system is nonlinear. The Genetic Algorithm (GA)　technique of optimization is used to obtain the optimized values of shaft diameter and face width on the pinion based on the ANN mathematical model and the results are compared as that obtained using the traditional method. The ANN and GA were performed using MATLAB. The simulation results were shown that the proposed algorithm was successfully calculated the value of shaft diameter and face width to obtain the minimal bending stress and material volume of the gearbox.

• Journal of Animal Environmental Science
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• v.8 no.1
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• pp.9-16
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• 2002

This study was conducted to develope the new solid separating system which can be efficiently and economically removed the solid parts in high pollutants concentration of pig slurry. The pollutants concentration, BOD$_{5}$ , COD and SS of the slurry used in this study was 15,990($\pm$2,389)mg/l, 20,004($\pm$5,512)mg/l and 26,486($\pm$5,935)mg/l, respectively. After removal of solid part in slurry, the pollutants concentration, BOD$_{5}$, COD and SS was change into 5,617($\pm$690)mg/l, 5,553($\pm$633)mg/land 1,456($\pm$341)mg/l, respectively in the Fixed biological membrane tank. The reduction of the pollutants concentration of suspend liquid through membrane will be allowed to greatly improve the water purification by an Activated sludge method. This separating system consisted of a temporary storage, a circulating tank and a Fixed Biological membrane tank. A temporary storage which has a draining system of screw type and an aeration device played a tremendous role in draining the solid by filled an aeration of 0.3 l/min. A Fixed Biological membrane tank of which a styrofoam filled in a 2/3 volume as a Biological media was fixed by a stainless steel net (pore size : 0.5mm) to separate the liquid layer of influx in them. The separating system efficiency factors were the speed of screw motor, cycle number of slurries in a circulating tank and moisture contents of solid effluent through the screw path. Although the pollutants concentration was very variable in temporary storage, the final concentration of $BOD_5$ and SS, except COD of the suspended liquid in a Fixed biological membrane were not different regardless of cycle number of a circulating tank. Moisture contents of effluent from temporary storage was 73% under the speed 1 ppm of screw motor and 62% under the 1/4rpm of it.

• Korean Journal of Construction Engineering and Management
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• v.16 no.4
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• pp.41-49
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• 2015

The amount of energy consumed in air ventilation systems of public facilities accounts for 40% of their total energy consumption. To reduce their energy consumption, applying variable speed operation controlled by an inverter with a high-efficiency motor is suggested. Since these methods require higher initial investment costs compared to the existing systems, economic evaluation should be conducted from a long-term perspective. While LCCA(Life Cycle Cost Analysis) model is useful to estimate net savings of alternatives that differs with respect to initial costs and operating costs, the environmental burdens are not considered. On the contrary LCA(Life Cycle Assesment) model is suitable to assess environmental impacts associated with the stages of a product's life but it does not consider costs. In this study, the high-efficient motors are introduced into the air ventilation system of a subway station and a comprehensive analysis on the economic and environmental impacts of the proposed method is conducted by using LCCA and LCA model.