• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.4
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• pp.26-31
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• 2008

This paper deals with the issue of position tracking control of a clamp-cylinder for injection moulding machine with electric-hydrostatic drives. A fixed displacement pump is utilized in combination with AC motor in order to directly control a clamp-cylinder. A clamp-cylinder may be required to operate under a variety of operating conditions. Therefore, robust control performance is important in position tracking control applications. In order to accommodate mismatches between the real plant and the model used for controller design, discrete-time sliding mode control is developed by combining a velocity feedforward loop. From tracking control experiments, it is shown that significant reduction in position tracking error is achieved through the use of sliding mode control.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.645-650
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• 2006

This paper presents the results of a study to verify the sufficient control performance of semiactive tuned mass damper and to identify suitable control methods for semiactive tuned mass damper in structural vibration control. In this study, four control algorithms are considered: on-off displacement based groundhook, on-off velocity based groundhook, clipped optimal and maximum energy dissipation algorithm. For semiactive tuned mass damper, MR damper is considered as a controllable damping device and the command voltage is calculated by the control algorithms. Each of the control theory is applied to the three story shear building excited by three earthquakes. The performance of each algorithm is compared with that of conventional tuned mass damper system using evaluation criteria. The simulation results indicate that semiactive tuned mass damper has control efficiency. Among the control algorithms, on-off displacement based control theory shows the best efficacy and robustness.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.413-434
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• 2012

This paper presents a displacement-based seismic design method with damage control, in which the targets for the considered performance level are set as displacements and a damage distribution is proposed by the designer. The method is based on concepts of basic structural dynamics and of a reference single degree of freedom system associated to the fundamental mode with a bilinear behaviour. Based on the characteristics of this behaviour curve and on the requirements of modal spectral analysis, the stiffness and strength of the structural elements of the structure satisfying the target design displacement are calculated. The formulation of this method is presented together with the formulations of two other existing methods currently considered of practical interest. To illustrate the application of the proposed method, 5 reinforced concrete plane frames: 8, 17 and 25 storey regular, and 8 and 12 storey irregular in elevation. All frames are designed for a seismic demand defined by single earthquake record in order to compare the performances and damage distributions used as design targets with the corresponding results of the nonlinear step by step analyses of the designed structures subjected to the same seismic demand. The performances and damage distributions calculated with these analyses show a good agreement with those postulated as targets.

• Korean Journal of Oriental Medicine
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• v.14 no.3
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• pp.113-119
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• 2008

In pulse diagnosis, the indentation pressure is one of the most important factors as well as the change of pulse shape and the distribution of pressure via time. But, on the oriental medical doctor's indentation pressure control, the understandings of the neurophysiological meanings and mechanisms have been lacked. So, in this paper, we considered on these issues and then proposed a proper system which can imitate the OMD's indentation pressure control mechanisms. As a result, both tactile information and kinesthetic information were found to be essential to the indentation pressure control so that a system, which can measure both the physical indent pressure and the displacement of an indentation arm, has been proposed. With this proposed system, while the indentation was being controlled through the moving step number of the step motor, the physical indentation pres sure and displacement of the indentation arm were measured. From these measured data, the relationships between the moving step number and both physical indentation pressure and displacement were revealed to have linear characteristics in early phase and to have nonlinear characteristics in latter phase. Additionally, three types of graph were generated whose X axis means the moving step number, the physical indentation pressure and the displacement respectively and Y axis means the pulse pressure. By comparing these graphs, we come to conclude that different concepts on indentation pressure control cause different diagnostic results on floating/sinking degrees for the same subject. Consequently, an indentation system for the pulse diagnosis should be able to provide both the tactile information and kinesthetic information, that is, the physical indentation pressure and the displacement of the indentation arm. In future, the proposed system should be optimized to the pulse diagnosis environment and how to combine the both information for more reliable diagnosis should be studied.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.1
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• pp.126-133
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• 2021

Axial displacement of an implant-supported prosthesis is frequently reported in clinical and laboratory studies. However, limited information is available about the behavior of the axial displacement of implant-supported prostheses functioning in intraoral situations. The present case report evaluated the three-dimensional displacement of posterior single implant-supported prostheses in 2 different patients. Internal connection type implants were placed, and screw and cement-retained prosthesis (SCRP) type prosthesis were delivered after an appropriate healing period. Intraoral digital scans were performed using an intraoral scanner (Cerec Omnicam, Dentsply Sirona, USA) on the day of crown delivery and one week, one month, and one year after delivery. The amount of 3-dimensional displacement of the prosthesis was evaluated by using a digital inspection software (Geomagic Control X, 3D systems, USA). The axial displacement of implant-supported prosthesis occurred in both patients. Furthermore, the amount of displacement increased over time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1462-1469
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• 1997

This study presents a genetic algorithm-based method for optimizing control parameters in fluid power systems. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics. A genetic algorithm seeks control parameters maximizing a measure that evaluates system performance. Five control gains of the PID-PD cascade controller fr an electrohydraulic speed control system with a variable displacement hydraulic motor are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that optimization of the five gains by manual tuning should be a task of great difficulty and that a genetic algorithm is an efficient scheme giving economy of time and in labor in optimizing control parameters of fluid power systems.

• Journal of KSNVE
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• v.7 no.6
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• pp.1007-1013
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• 1997

This paper presents active vibration control scheme of multi-mode forced vibration using piezocetamic sensors and actuators. The control scheme adopted is the Positive Position Feedback (PPF) control. Among various vibration control techniques. PPF control technique makes use of generalized displacement measurements to accomplish the vibration suppression. Two independent controllers are implemented to control the first and the second modes of the beam under external excitation. Experimental results for various damping ratios and feedback gains of the PPF controllers are compared with respect to the contorl efficiency. The results indicate that steady state vibration under wide band excitation can be controlled effectively when multiple sets of PZT sensors and actuators were used with PPF control technique.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.52-59
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• 2004

In this paper, the efficacy of the MR damper-based control systems for vibration suppression of stay cables has been experimentally investigated. The performance of the several control strategies for the semiactive control system, such as the clipped-optimal control, the Lyapunov stability theory-based control, the maximum energy dissipation and the modulated homogeneous friction, has been compared with that of the passive-type control systems employing MR dampers. To do this, the full-scale stay cable, which is the same as used for the in-service cable-stayed bridge in Korea, is considered. The acceleration and the displacement of the stay cable as well as the damping force of the MR damper are measured. The velocity of the cable at the damper location, which is needed for some control algorithms, is obtained by differentiating the measured displacement. The damping ratios of the cable system employing the MR damper, which can be estimated by the Hilbert transform-based method, shows effectiveness of each control strategy considered.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1605-1617
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• 1994

Air-spring is widely used in vibration isolation to reduce the table vibration. When a disturbance is applied to a table, however, it starts virbrating with a low frequency, but has a large displacement due to the reacting force of air-spring. In this study, to solve the table vibration problem, an active vibration control device based on state feedback control using air-spring and proportional control valves was designed. This device can suppress the displacement of the isolation table within allowable range, even any kind of disturbances are applied to the table. Firstly, theoretical analysis of an air-spring isolator was done. Secondly, characteristics of the isolator was investigated via computer simulation and experiment. Finally, active control of air-spring isolator was tested using optimal(LQG) and fuzzy control algorithms was performed to show the effectiveness of the control schems.

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.122-131
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• 2004

A constraint equation-based control law design for large angle attitude maneuvers of flexible spacecraft is addressed in this paper The tip displacement of the flexible spacecraft model is prescribed in the form of a constraint equation. The controller design is attempted in the way that the constraint equation is satisfied throughout the maneuver. The constraint equation leads to a two-point boundary value problem which needs backward and forward solution techniques to satisfy terminal constraints. An observer-based tracking control law takes the constraint equation as the input to the dynamic observer. The observer state is used in conjunction with the state feedback control law to have the actual system follow the observer dynamics. The observer-based tracking control law eventually turns into a stabilized system with inherent nature of robustness and disturbance rejection in LQR type control laws.