• Smart Structures and Systems
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• v.23 no.6
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• pp.521-536
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• 2019

Using magnetorheological (MR) dampers in multiswitch open-loop control mode has been shown to be cost-effective for cable vibration mitigation. In this paper, a method for analyzing the damping performance of taut cables incorporating MR dampers in open-loop control mode is developed considering the effects of damping coefficient, damper stiffness, damper mass, and stiffness of the damper support. Making use of a three-element model of MR dampers and complex modal analysis, both numerical and asymptotic solutions are obtained. An analytical expression is obtained from the asymptotic solution to evaluate the equivalent damping ratio of the cable-damper system in the open-loop control mode. The individual and combined effects of the damping coefficient, damper stiffness, damper mass and stiffness of damper support on vibration control effectiveness are investigated in detail. The main thrust of the present study is to derive a general formula explicitly relating the normalized system damping ratio and the normalized damper parameters in consideration of all concerned effects, which can be easily used for the design of MR dampers to achieve optimal open-loop vibration control of taut cables.

• Earthquakes and Structures
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• v.20 no.3
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• pp.353-364
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• 2021

Natural hazards like earthquakes, high winds, and tsunami are a threat all the time for multi-story structures. The environmental forces cannot be clogged but the structures can be prevented from these natural hazards by using protective systems. The structural control can be achieved by using protective systems like the passive, active, semi-active, and hybrid protective systems; but the semi-active protective system has gained importance because of its adaptability to the active systems and reliability of the passive systems. Therefore, a semi-active protective system for the earthquake forces has been adopted in this work. Magneto-Rheological (MR) damper is used in the structure as a semi-active protective system; which is connected to the current driver and proposed controller. The Proportional Integral Derivative (PID) controller and reliable PID controller are two proposed controllers, which will actuate the MR damper and the desired force is generated to mitigate the vibration of the structural response subjected to the earthquake. PID controller and reliable PID controller are designed and tuned using Ziegler-Nichols tuning technique along with the MR damper simulated in Simulink toolbox and MATLAB to obtain the reduced vibration in a three-story benchmark structure. The earthquake is considered to be uncertain; where the proposed control algorithm works well during the presence of earthquake; this paper considers robustness to provide satisfactory resilience against this uncertainty. In this work, two different earthquakes are considered like El-Centro and Northridge earthquakes for simulation with different controllers. In this paper performances of the structure with and without two controllers are compared and results are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.513-518
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• 1998

In this paper, a robust fault-tolerant control scheme for robot manipulators overcoming actuator failures is presented. The joint(or actuator) fault considered in this paper is the free-swinging joint failure and causes the loss of torque on a joint. The presented fault-tolerant control framework includes a normal control with normal(non-failed) operation, a fault detection and a fault-tolerant control to achieve task completion. For both no uncertainty case and uncertainty case, a stable normal con-troller and an on-line fault detection scheme are presented. After the detection and identification of joint failures, the robot manipulator becomes the underactuated robot system with failed actuators. A robust adaptive control scheme of robot manipulators with the detected failed-actuators using the brakes equipped at the failed(passive) joints is proposed in the presence of parametric uncertainty and external disturbances. To illustrate the feasibility and validity of the proposed fault-tolerant control scheme, simulation results for a three-link planar robot arm with a failed joint are presented.

• Smart Structures and Systems
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• v.23 no.6
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• pp.627-639
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• 2019

Passive control may not provide enough damping for a stay cable since the control devices are often restricted to a low location level. In order to enhance control performance of conventional passive dampers, a new type of damper integrated with a rotary electromagnetic damper providing variable damping force and a flywheel serving as an inertial mass, called the rotary electromagnetic inertial mass damper (REIMD), is presented for suppressing the cable vibrations in this paper. The mechanical model of the REIMD is theoretically derived according to generation mechanisms of the damping force and the inertial force, and further validated by performance tests. General dynamic characteristics of an idealized taut cable with a REIMD installed close to the cable end are theoretically investigated, and parametric analysis are then conducted to investigate the effects of inertial mass and damping coefficient on vibration control performance. Finally, vibration control tests on a scaled cable model with a REIMD are performed to further verify mitigation performance through the first two modal additional damping ratios of the cable. Both the theoretical and experimental results show that control performance of the cable with the REIMD are much better than those of conventional passive viscous dampers, which mainly attributes to the increment of the damper displacement due to the inertial mass induced negative stiffness effects of the REIMD. Moreover, it is concluded that both inertial mass and damping coefficient of an optimum REIMD will decrease with the increase of the mode order of the cable, and oversize inertial mass may lead to negative effect on the control performance.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.829-834
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• 2003

Many types of omnidirectional wheels with passive rollers have gaps between rollers. Since these gaps cause a wheel to make discontinuous contact with the ground, they lead to vertical and/or horizontal vibrations during wheel operation. In addition, the radii of passive rollers are related to the height of a bump an omnidirectional wheel can surmount. In this research a new design of the alternate wheel is proposed. Because this wheel makes continuous contact with the ground and has alternating large and small rollers around the wheel, it is termed a continuous alternate wheel (CAW). In this paper a design procedure is also presented to determine the optimum number of rollers, the radii of rollers and the inside inclination angle of an outer roller for given design specifications. The CAW based on this design is compared to the existing alternate wheels in terms of design. Finally, an actual continuous alternate wheel is constructed to verify validity of the design guidelines.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.514-519
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• 1997

The MRX is an integral type ship reactor with 100 MWt power, which is designed by Japan Atomic Energy Research Institute. It is characterized by integral type PWR, in-vessel type control roe drive mechanism, water-filled containment vessel and passive decay heat removal system. Marine reactor should have high passive safety. Therefore, in this study, we simulated the loss of flow accident to verify the passive decay heat removal by natural circulation using RETRAN-03 code. auxiliary feed water systems are used for decay heat removal mechanism and results are compared with the loss of flow accident analysis using emergency decay heat removal system by JAERI. Results are very similar to case of EDRS 1 loop operation in JAERI analysis and decay heat is successfully removed by natural circulation.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.56-63
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• 2014

This study proposes a new control approach for efficient vibration suppression of two identical adjacent structures. The conventional control approach of two adjacent structures is to interconnect the two structures with passive, semi-active or active control devices. However, when the two adjacent structures are identical to each other, their dynamical behaviors such as frequency and damping properties are also the same. In this case, the interconnected control devices cannot exhibit the dissipative control forces on the both structures as expected since the relative displacements and velocities of the devices become close to zero. In other words, the interconnection method does not work for the twin structures as enough as expected. In order to solve this problem, we propose several new control approaches to effectively and efficiently reduce the identically-fluctuating responses of the adjacent structures with minimum control efforts. In order to demonstrate the proposed control systems, the proposed several control systems are optimally designed and their control performances are compared with that of the conventional optimal control system where each TMD(tuned mass damper) is installed in each structure for independent control purpose. The simulated results show that one of the proposed control systems(System 04) is able to guarantee enhanced control performance compared with the conventional system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.4
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• pp.189-197
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• 2003

The problem of designing a parallel feedforward compensator (PFC) is considered for a class of non-square linear systems such that the closed-loop system is strictly passive. If a given square system has (vector) relative degree one and is weakly minimum phase, the system can be rendered passive by a state feedback. However, when the system states are not always measurable and the given output is considered, passivation (i.e. rendering passive) of a non-minimum phase system or a system with high relative degree cannot be achieved by any other methodologies except by using a PFC. To passivate a non-square system we first determine a squaring gain matrix and design a PFC such that the composite system has relative degree one and is minimum phase. Then the system is rendered strictly passvie by a static output feedback law. Necessary and sufficient conditions for the existence of the PFC and the squaring gain matrix are given by the static output feedback formulation, which enables to utilize linear matrix inequality (LMI). As an application of the scheme, an alternative way of replacing the role of velocity measurements is provided for the PD-control law of a convey-crane system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.191-194
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• 1997

Passive, semi-active and active dampers have been used to dissipate energy in mechanical systems. Semi-active dampers have higher performance than passive dampers and require lower power to operate than active dampers. Its damping characteristics can be changed appropriately for varying conditions. In this paper, we developed a semi-active damper based on Magnetorheological(MR) fluid. MR fluid has a variable damping characteristics proportional for the magnetic field intensity. It has several advantages such as high strength, low viscosity, robustness in impurities and wide temperature range of operational stability. We designed a constrained rotary MR damper base on valve mode which can dissipate more energy per unit volume. The system with Bingham characteristics is obtained and proved by the experiment.

• Architectural research
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• v.22 no.2
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• pp.41-52
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• 2020

Laboratory buildings with specialized equipment and ventilation systems pose challenges in terms of efficient energy use and initial construction costs. Additionally, lab spaces should have flexible and efficient layouts and provide a comfortable indoor research environment. Therefore, this study aims to identify the correlation between the facade of a building and its interior layout from case studies of energy-efficient research labs and to propose passive energy design strategies for the establishment of an optimal research environment. The case studies in this paper were selected from the American Institute of Architects Committee on the Environment Top Ten Projects and Leadership in Energy and Environmental Design (LEED) certified research lab projects. In this paper, the passive design strategies of space zoning, façade design devices to control heating and cooling loads were analyzed. Additionally, the relationships between these strategies and the interior lab layouts, lab support spaces, offices, and circulation areas were examined. The following four conclusions were drawn from the analysis of various cases: 1) space zoning for grouping areas with similar energy requirements is performed to concentrate similar heating and cooling demands to simplify the HVAC loads. 2) Public areas such as corridor, atrium, or courtyard can serve as buffer zones that employ passive solar design to minimize the mechanical energy load. 3) A balanced window-to-wall ratio (WWR), exterior shading devices, and natural ventilation systems are applied according to the space programming energy requirements to minimize the dependence on mechanical service. 4) Lastly, typical laboratory space zoning categories can be revised, reversed, and even reconfigured to minimize the energy load and adjust to the site context. This study can provide deep insights into various design strategies employed for construction of green laboratories along with intuitive arrangement of various building components such as laboratory spaces, lab support spaces, office spaces, and common public areas. The key findings of this study can contribute towards creating improved designs of laboratory facilities with reduced carbon footprint and greenhouse emissions.