• 상하수도학회지
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• 제18권2호
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• pp.215-221
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• 2004

Effluent of wastewater treatment plant is to be disinfected to protect drinking water sources. DOF (Dissolved Ozone Flotation) was developed to meet this purpose. DOF was developed by combining DAF system with ozone. DAF system has good floating power with numerous microbubbles, and ozone has strong oxidation capability. And DOF system has good floating power and strong oxidation capability simultaneously. When DOF was applied to secondary wastewater effluent, color of 11CU in raw water which was secondary effluent was reduced to 1CU by the DOF system. Removal rate of other water quality parameters treated by DOF were also higher than that by DAF, which were proved the strength of oxidation capability of ozone. When ozone concentration of 3.3mg/l were applied in DOF system, general aerobic bacteria were reduced to 5CFU/ml from TNTC (Too many Numbers To Count). With the same ozone concentration, total coliform were not detected at all. These figures are under the numbers of drinking water regulation. These microbes were the target parameters of DOF. It was proved that DOF was very effective in disinfection of wastewater treatment plant effluent as well as in removal of color, turbidity, and T-P.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.449-454
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• 1994

The Stewart Platform is one example of a motion simulator which generater 6DOF motion in space by six actuators in parallel. The presented control methrol of 6DOF motion simulator is generally classified into two types, one is SISO and the other is MIMO control type. The SISO control can't compensate for external load variation and different dynamic behavior of 6DOF motion, trerefore this type don's control motion precisely. On the other hand, the MIMO control compensates for a interference of 6DOF motion because MIMO controller is designed with 6DOF motion simulator synamics. But MIMO control of motion simulator has a complexity of 6DOF displacement feedback, because in oder to obtain feedback value we must solve the forward kinematics using measurement of cylinder length or design a state estimator, unless measurement of 6DOF displacement is possible. In this paper, a multivariable controller using H .inf. optimal control theory is designed to consider a interference of 6DOF motion and to obtain robust,precise control of system. Also in order to solve the mentioned problem of MIMO control, this paper presents a modified MIMO control model which control 6DOF motion by using feedback of measurement od cylinder length.

• Journal of Power Electronics
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• 제4권4호
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• pp.217-227
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• 2004

A robust controller that combines the merits of the feed-back, feed-forward and model-following control for induction motor drives utilizing field orientation control is designed in this paper. The proposed controller is a two-degrees-of­freedom (2DOF) integral plus proportional & rate feedback (I-PD) speed controller combined with a model-following (2DOF I-PD MFC) speed controller. A systematic mathematical procedure is derived to find the parameters of the 2DOF I-PD MFC speed controller according to certain specifications for the drive system. Initially, we start with the I-PD feed­back controller design, then we add the feed-forward controller. These two controllers combine to form the 2DOF I-PD speed controller. To realize high dynamic performance for disturbance rejection and set point tracking characterisitics, a MFC controller is designed and added to the 2DOF I-PD controller. This combination is called a 2DOF I-PD MFC speed controller. We then study the effect of the 2DOF I-PD MFC speed controller on the performance of the drive system under different operating conditions. A computer simulation is also run to demonstrate the effectiveness of the proposed controller. The results verify that the proposed 2DOF I-PD MFC controller is more accurate and more reliable in the presence of load disturbance and motor parameter variations than a 2DOF I-PD controller without a MFC. Also, the proposed controller grants rapid and accurate responses to the reference model, regardless of whether a load disturbance is imposed or the induction machine parameters vary.

• 상하수도학회지
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• 제19권6호
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• pp.767-774
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• 2005

The DOF (Dissolved Ozone Flotation) system was used to treat the effluent of the secondary wastewater treatment plant. The DOF system uses ozone instead of air, while DAF (Dissolved Air Flotation) uses air. Moreover, since the solubility of ozone is higher than air, the DOF system produces larger volume of micro-bubbles than the DAF system does. Thus, the DOF system performs better than the DAF system in floating ability. The DOF system could remove 70% of turbidity to an average of 0.59NTU in effluent from 2.31NTU in influent. The removal efficiency of absorbance measured with UV-254 in the effluent of the DOF system was 63%, while only 19% was removed by the DAF system. the DOF system removed 84% of the color from 25~26CU to 4CU, while DAF system removed 42% of the color to 15 CU. The CODMn removal efficiency of the DOF system was 34%, 6.8mg/l of effluent $COD_{Mn}$ concentratin, while it was 20%, 8.3mg/L of effluent $COD_{Mn}$ concentratin, to use the DAF system. Microbial bacteria such as coliform bacteria, and heterotrophic bacteria were removed over 99% by the DOF system, and 42~45% by the DAF system. That is, Microbial bacteria were almost completely destroyed by the DOF system. To sum up with, the DOF system was found to be very effective to treat effluent of the wastewater treatment plant.

• Structural Engineering and Mechanics
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• 제21권6호
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• pp.713-735
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• 2005

Due to the complexity of mathematical expressions, the literature concerning the free vibration analysis of plates carrying multiple three-degree-of-freedom (dof) spring-mass systems is rare. In this paper, the three degrees of freedom (dof's) for a spring-mass system refer to the translational motion of its lumped mass in the vertical ($\bar{z}$) direction and the two pitching motions of its lumped mass about the two horizontal ($\bar{x}$ and $\bar{y}$) axes. The basic concept of this paper is to replace each three-dof spring-mass system by a set of equivalent springs, so that the free vibration characteristics of a rectangular plate carrying any number of three-dof spring-mass systems can be obtained from those of the same plate supported by the same number of sets of equivalent springs. Since the three dof's of the lumped mass for each three-dof spring-mass system are eliminated to yield a set of equivalent springs, the total dof of the entire vibrating system is not affected by the total number of the spring-mass systems attached to the rectangular plate. However, this is not true in the conventional finite element method (FEM), where the total dof of the entire vibrating system increases three if one more three-dof spring-mass system is attached to the rectangular plate. Hence, the computer storage memory required by using the presented equivalent spring method (ESM) is less than that required by the conventional FEM, and the more the total number of the three-dof spring-mass systems attached to the plate, the more the advantage of the ESM. In addition, since manufacturing a spring with the specified stiffness is much easier than making a three-dof spring-mass system with the specified spring constants and mass magnitude, the presented theory of replacing a three-dof spring-mass system by a set of equivalent springs will be also significant from this viewpoint.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.95-103
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• 2001

The purpose of Introducing a combined cycle with gas turbine in power plants is to reduce losses of energy, by effectively using exhaust gases from the gas turbine to produce additional electricity or process. The efficiency of a combined power plant with the gas turbine increases, exceeding 50%, while the efficiency of traditional steam turbine plants is approximately 35% to 40%. Up to the present time, the PID controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain without any experience, since the gain of the PID controller has to be manually tuned by trial and error procedures. This paper focuses on the neural network tuning of the 2-DOF PID controller with a combined 2-DOF parameter (NN-Tuning 2-DOF PID controller), for optimal control of the Gun-san gas turbine generating plant in Seoul, Korea. In order to attain optimal control, transfer function and operating data from start-up, running, and stop procedures of the Gun-san gas turbine have been acquired and a designed controller has been applied to this system. The results of the NN-Tuning 2-DOF PID are compared with the PID controller and the conventional 2-DOF PID controller tuned by the Ziegler-Nichols method through experimentation. The experimental results of the NN-Tuning 2-DOF PID controller represent a more satisfactory response than those of the previously-mentioned two controllers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.302-307
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• 2005

Recently, lots of parallel mechanisms for spatial 3-DOF and 6-DOF were investigated. However, research on 4-DOF and 5-DOF parallel mechanisms has been very few. In this paper, we propose a 4-DOF parallel mechanism that consists of 3-rotational and 1-translational motions. The kinematic characteristics of this mechanism are analyzed in terms of an isotropic index and maximum force transmission ratio, and its kinematic optimization is being conducted to ensure enhanced kinematic performances

• 디지털융복합연구
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• 제13권1호
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• pp.331-339
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• 2015

사이버나이프치료에서 삽입된 금표지자의 삽입 개수 및 인식의 제한으로 인하여 3D DOF로 치료하는 경우 척추구조물 정렬을 가능하게 하는 Xsight spine tracking system으로 회전방향의 위치오차를 보정함으로서 표적위치오차를 개선하고, 치료방법의 대안을 제시하고자 한다. 실험결과 6D DOF에서 표적위치오차는 $0.214{\pm}0.058mm$, 종양내부에 삽입된 2개 금표지자를 이용한 3D DOF에서 $0.673{\pm}0.142mm$, 종양외부에 삽입된 2개 금표지자를 이용한 3D DOF에서 $1.126{\pm}0.253mm$, Xsight spine tracking system의 적용 한 3D DOF에서 $0.542{\pm}0.103mm$로 나타났다. 실험결과 척추 구조물로 회전방향에 대한 보정을 시행하였을 때 표적위치에 대한 정확성이 약 48% 향상되었다. 또한, 선량분포의 일치성도 약 3%가 향상되어 일치하는 것을 확인할 수 있었다. 따라서 척추구조물 정렬을 병용한 Xsight spine tracking system의 회전방향에 대한 보정은 유용한 것으로 평가 되었다.

• 한국정밀공학회지
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• 제27권4호
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• pp.53-62
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• 2010

This study introduces about development of multi-DOF ultrasonic motor that are composed of a bar-shaped stator and a spherical rotor. The ultrasonic motor is a motor which is operated by vibrations over frequency of 20kHz. The multi-DOF ultrasonic motor will be developed by expanding the basic theory of existing 1-DOF ultrasonic motor. It can generate 3-DOF rotation of the rotor around perpendicular axes using 3 vibration modes of stator. By using finite element methods, the optimal dimension of stator is decided and made the components of stator. When we apply the multi-DOF ultrasonic motor composed of rotor and stator to the driving test system, it will be checked whether the motor can be driven at the direction of 3-DOF or not. And it is proposed how the simulation of square bar shaped multi-DOF ultrasonic motor is accomplished.

• 전기학회논문지
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• 제57권8호
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• pp.1362-1370
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• 2008

This paper describes the design and characteristic analysis of a novel 3-DOF(Degree of Freedom) spherical motor. For multi DOF actuating, several numbers of motors have been used. By the using of normal motors they connected each other in single joint, is necessary to a several type of complex power transmission devices. The 3-DOF spherical motor can drive roll, pitch, and yaw motion in only one unit and it is not necessary to use additional gears and links parts. Therefore the using of 3-DOF spherical motor can eliminate; combined effects of inertia, backlash, non-linear friction, and elastic deformation of gears. In this paper, we propose the novel structured 3-DOF spherical motor and derive its principles of operation. Firstly, we designed concept model of novel structured 3-DOF spherical motor. Next, we derive the control method by calculating the currents. Also, to have intuitive driving control, we express the rotor position in equivalent angle-axis system and determine the exciting period of currents from the calculation result of the currents. To verify the control method, we calculated the currents by the position of rotor. and then we analyzed the characteristics by 3D Finite Element Method when the calculated currents are excited.