• Journal of Advanced Marine Engineering and Technology
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• v.23 no.1
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• pp.69-78
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• 1999

In this study a new pattern of pressure control of hydraulic cylinder using high speed On-Off solenoid valve in the electro-hydraulic system has been suggested. The control valve is 3-way high speed On-Off solenoid valve which is operated by PWM(Pulse Width Modulation)control signal. The high speed On-Off solenoid valve has a tendency to induce severe pressure fluctuation in the hydraulic actuator so it has not been used for the purpose of closed loop control with direct pres-sure feedback. In this study closed loop control with direct pressure feedback is enabled by using a digital filter which has linear minimum mean square filter algorithm. Through some experiments it is confirmed that stable pressure control can be realized by the proposed control technique.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.93-98
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• 2001

This paper studies on the design of an ILQ(Inverse Linear Quadratic optimal control) looper control system for hot strip mills. The looper which is placed between each stand plays an important role in controlling strip width by regulating strip tension variation generated from the velocity difference of main work rolls. The mathematical model for looper is firstly obtained by Taylor's linearization of nonlinear differential equations, where it is given as a linear and time invariant state-space equation. Secondly, a looper servo controller is designed by ILQ control algorithm, which is an inverse problem of LQ(Linear Quadratic optimal control) control. By tunning control gain arbitration parameters and time constants, it is shown that the ILQ looper servo controller has the performance that makes well to follow desired trajectories of both strip tension and looper angle.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.303-309
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• 2019

A hybrid control of a rectifier/regulator of wireless power transfer systems for electric vehicles is studied. A combined rectifier/regulator is used for charging control. The hybrid control comprises integral cycle control and pulse width modulation control to cope with the variations in the induced voltage due to clearance and alignment. The hybrid control has good control capability and does not cause severe switching loss. A 22 kW prototype of the Wireless Power Transfer class 4 charging system defined by the Society of Automotive Engineers is constructed and tested to verify the proposal.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.291-304
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• 1994

The purpose of this study was to analyze the facial asymmetry of the patients with the craniomandibular disorder. In this study, 50 patients, who have joint clicking and pain, mouth opening limitation, and 40 dental students, Chosun University, who did not posses any restoration and orthodontic treatment, joint clicking and pain, mouth opening limitation, were selected as the control group. Both the control group and the patient group were takened skull P-A, submento-vertex radiogram by standized methods. After that, the deviation and facial asymmetry were measured and analyzed. The results of the this study were as follows: 1. In the Skull P-A radiogram, the width difference of control group and patient group measured that the △ Cg-Go-Cl: control group were 3.35㎜, patient group were 4.51㎜ (P<0.05), the △Cg-Zy-Go: control group were 1.83㎜, patient group were 3.27㎜(P<0.001). 2. In the Skull P-A radiogram, the height difference of control group and patient group measured that the △ Cg-Go-Cl: control group were 131.85㎜, patient group were 188.45㎜(P<0.05), the △Cg-Zy-Go: control group were 1.58㎜, patient group were 2.68㎜(P<0.00l). 3. In the Skull P-A radiogram, the area difference of control group and patient group measured that the △ Cg-Go-Cl: control group were 120.76㎟, patient group were 185.49㎟(P<0.05), the △Cg-Zy-Go: control group were 2.29㎟, patient group were 3.37㎟(p<0.05). 4. In the submento-vertex radiogram, the width difference of control group and patient group measured that the △Mr-Cl-Ia: control group were 1.50㎜, patient group were 2.35㎜(P<0.05), the △Mr-Cm-Ia: control group were 1.75㎜, patient group were 3.17㎜(P<0.05), the △Mr-Go-Ia: control group were 1.96㎜, patient group were 3.24㎜(P<0.001), the △Mr-Cp-Co: control group were 1.74㎜, patient group were 2.73㎜(P<0.05). 5. In the submento-vertex radiogram, the height difference of control group and patient group measured that the △Mr-Cp-Ia: control group were 1.68㎜, patient group were 2.46㎜P<0.05), the △Mr-CI-Ia: control group were 2.38㎜, patient group were 3.74㎜(P<0.05), the △Mr-Co-Ia: control group were 1.63㎜, patient group were 2.80㎜(P<0.05), the △Mr-Cm-Ia: control group were 1.45㎜, patient group were 3.12㎜(P<0.001). 6. In the submento-vertex radiogram, the area difference of control group and patient group measured that the △ Mr-Cp-Ia: control group were 73.17㎟, patient group were 110.16㎟(P<0.05), the △Mr-Cl-Ia: control group were 105.09㎟, patient group were 180.87㎟(P<0.001), the △Mr-Co-Ia: control group were 103.31㎟, patient group were 148.48㎟(P<0.05), the △Mr-Cm-Ia: control group were 97.01㎟, patient group were 167.83㎟(P<0.05), the △Mr-Go-Ia: control group were 104.24㎟, patient group were 205.90㎟(P<0.05).

• Journal of Environmental Science International
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• v.20 no.5
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• pp.555-564
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• 2011

This study examines the potential restoration of abandoned channels of the Mangyeong River in South Korea. To analyze the morphological changes and equilibrium conditions, a flow duration analysis was performed to obtain the discharge of 255 m3/s with a recurrence interval of 1.5 year. It is a gravel-bed stream with a median bed diameter of 36 mm. The reach-averaged results using HEC-RAS showed that the top width is 244 m, the mean flow depth is 1.11 m, the width/depth ratio is very high at 277, the channel velocity is 1.18 m/s, and the Froude number is also high at 0.42. The hydraulic parameters vary in the vicinity of the three sills which control the bed elevation. The total sediment load is 6,500 tons per day and the equivalent sediment concentration is 240 mg/l. The Engelund-Hansen method was closer to the field measurements than any other method. The bed material coarser than 33 mm will not move. The methods of Julien-Wargadalam and Lacey gave an equilibrium channel width of 83 m and 77 m respectively, which demonstrates that the Mangyeong River is currently very wide and shallow. The planform geometry for the Mangyeong River is definitely straight with a sinuosity as low as 1.03. The thalweg and mean bed elevation profiles were analyzed using field measurements in 1976, 1993 and 2009. The measured profiles indicated that the channel has degraded about 2 m since 1976. The coarse gravel material and large width-depth ratio increase the stability of the bed material in this reach.

• Korean Journal of Agricultural Science
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• v.45 no.2
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• pp.283-289
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• 2018

Agricultural gear reducers are used in a variety of agricultural machinery designs such as in agricultural tractors and transport cars, and even greenhouses. For greenhouses, a gear reducer is used to control windows on the side and the roof. Gear reducers for agricultural applications are designed using the empirical method because of the lack of a standard for experimentation. Simulation is necessary for the optimal design of an agricultural gear reducer. There are many advantages to this optimization such as low-cost maintenance, reduced size, and weight. In this study, bending and contact safety factor simulation for the gear reducer of a greenhouse was conducted by decreasing the face widths of helical gear shaft 2 and shaft 3 from 30.8 and 30 mm, respectively, at an interval of 4 mm. The bending and contact safety factors were calculated using AGMA standard. Simulation results showed that bending and contact safety factors decreased rapidly when the face width of the helical gear on shaft 2 was 30 mm and the face width of helical gear on shaft 3 decreased from 30.8 mm to 26.8 mm, suggesting that it would be safe to reduce the face width of the helical gear on shaft 3 to 26.8 mm. The reduction of the face width also reduced the weight of the agricultural gear. This study suggests that the agricultural gear reducer safety factor decreases as the face width decreases.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.173-181
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• 1994

A Cold spot temperature control system for the batch annealing furnace has been estabilished in order to reduce energy consumption to improve productivity and stabilize the propertics of products. Therefore we confirmed a relation between annealing cycle time and atmospheric gas, variation of coil cold spot temperature with time during heating and actual temperature measurements at mid-width of each coil during heating and actual temperature measurements at mid-width of each coil during soaking. The results of the tempaeature variation effect on the batch annealing are as follows. 1) Heating time is reduced to one half with increasing atmospheric gas flow rate and changing of atmospheric gas component from HNx to Ax gas, and annealing cycle time is reduced to 2.7 times. 2) In case of short time healing, the slowest heating part is the center of B coil, in case of long time heating, the low temperature point moves from the center of coil to inside coil. And the temperature in this part is higher than other parts when cooling. When finished heating, the cold spot is located 1/3 of coil inside in case of HNx atmospheric gas. But center of coil in case of Ax atmospheric gas. 3) The outside of top coil is the highest temperature point when heating, which becomes the lowest temperature point when cooling. So, this point becomes high temperature zone at heating and low temperature zone at cooling, It has relation according to atmospheric gas component and flow rate. 4) Soaking time at batch annealing cycle determination is made a decision by the input coil width, and soaking time for quality homogenization of 1214mm width coil must be 2.5 hours longer than that of 914mm width coil for the same ciol weight. 5) Annealing cycle time with Ax atmospheric gas is extended 1 hour in of slow cooling during 5 hours in order to avoid rapid cooling.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.109-120
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• 2011

This paper presents an experimental study results on the crack control of flexure-dominant reinforced concrete beams repaired with strain-hardening cement composite (SHCC). Five RC beams were fabricated and tested until failure. One unrepaired RC beam was a control specimen (CBN) and remaining four speciemens were repaired with SHCC materials. The test parameters included two types of SHCC matrix ductility and two types of repair method (patching and layering). Test results demonstrated that RC beams repaired with SHCC showed no concrete crushing or spalling until final failure, but numerous hair cracks were observed. The control specimen CBN failed due to crushing. It is important to note that SHCC matrix can improve crack-damage mitigation and flexural behavior of RC beams such as flexural strength, post peak ductility, and energy dissipation capacity. In the perspective of crack width, crack widths in RC beams repaired with SHCC had far smaller crack width than the control specimen CBN under the same deflection. Especially, the specimens repaired with SHCC of PVA0.75%+PE0.75% showed a high durability and ductility. The crack width indicates the residual capacity of the beam since SHCC matrix can delay residual capacity degradation of the RC beams.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.165-168
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• 2000

Improvement on the switching characteristic of IGBT by means of the uniform and local lifetime control is studied numerically using two-dimensional simulator, MEDICI. In the case of uniform lifetime control, the on-state and switching characteristics are simulated as a function of lifetime, and compared with the experimental results reported, which allows a relationship between dose of electron irradiation and controlled lifetime. In the case of local lifetime control, simulations are carried out by varying the position, width, and lifetime of the locally controlled region, and the results are compared with the characteristics for the case of the uniform lifetime control. The turn-off time of the device with an optimized locally controlled region is found to decrease from about $4.5\mus$ to 0.11$mutextrm{s}$ while the forward voltage drop increases from 1.37V to 2.61V in comparison with that for the uniform lifetime control.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.10
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• pp.1014-1021
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• 2008

This paper proposes an intelligent sliding mode control method for robotic systems with the unknown bound of model uncertainties. In our control structure, the unknown bound of model uncertainties is used as the gain of the sliding controller. Then, we employ the function approximation technique to estimate the unknown nonlinear function including the width of boundary layer and the uncertainty bound of robotic systems. The adaptation laws for all parameters of the self-recurrent wavelet neural network and those for the reconstruction error compensator are derived from the Lyapunov stability theorem, which are used for an on-line control of robotic systems with model uncertainties and external disturbances. Accordingly, the proposed method can not only overcome the chattering phenomenon in the control effort but also have the robustness regardless of model uncertainties and external disturbances. Finally, simulation results for the five-link biped robot are included to illustrate the effectiveness of the proposed method.