• Smart Structures and Systems
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• v.19 no.1
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• pp.21-31
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• 2017

To control the stochastic vibration of a vibration-sensitive instrument supported on a beam, the beam is designed as a sandwich structure with magneto-rheological visco-elastomer (MRVE) core. The MRVE has dynamic properties such as stiffness and damping adjustable by applied magnetic fields. To achieve better vibration control effectiveness, the optimal bounded parametric control for the MRVE sandwich beam with supported mass under stochastic and deterministic support motion excitations is proposed, and the stochastic and shock vibration suppression capability of the optimally controlled beam with multi-mode coupling is studied. The dynamic behavior of MRVE core is described by the visco-elastic Kelvin-Voigt model with a controllable parameter dependent on applied magnetic fields, and the parameter is considered as an active bounded control. The partial differential equations for horizontal and vertical coupling motions of the sandwich beam are obtained and converted into the multi-mode coupling vibration equations with the bounded nonlinear parametric control according to the Galerkin method. The vibration equations and corresponding performance index construct the optimal bounded parametric control problem. Then the dynamical programming equation for the control problem is derived based on the dynamical programming principle. The optimal bounded parametric control law is obtained by solving the programming equation with the bounded control constraint. The controlled vibration responses of the MRVE sandwich beam under stochastic and shock excitations are obtained by substituting the optimal bounded control into the vibration equations and solving them. The further remarkable vibration suppression capability of the optimal bounded control compared with the passive control and the influence of the control parameters on the stochastic vibration suppression effectiveness are illustrated with numerical results. The proposed optimal bounded parametric control strategy is applicable to smart visco-elastic composite structures under deterministic and stochastic excitations for improving vibration control effectiveness.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.864-871
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• 2015

Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.163-167
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• 2009

In this study, the acoustic properties of ceramic sound absorbing materials with different thickness and bulk density were investigated in terms of characteristic impedance, propagation constant, and absorption coefficient. The well-known two-cavity method was used for evaluating those acoustic parameter values. Also, in order to validate the experimentally measured values, the results were compared with the results obtained from Chung and Blaser's transfer function method and SWR method. The experimentally measured values of normal absorption coefficients were generally agreed well with the corresponding values from the transfer function method and the SWR method. Based on the experimental results, the following conclusions could be made. The magnitude of the absorption coefficient and the frequency range of the maximum absorption coefficient were controllable by changing the thickness and bulk density of the sound absorbing materials.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.860-864
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• 2008

In modern society, people tend to spend their time on various types of chairs. However, it is not easy for a designer to design a comfortable chair, because satisfaction with the chair depends not only on the quantitative elements such as size, but also on the qualitative element such as the user's feeling. To deal with these problems, there have been many studies on designing an ergonomics chair. In this paper, the hapticaided design (HAD) system was adopted to design the ergonomics chair. Based on the HAD system, the designer can experience whether the chair is comfortable or not through the haptic device, and also can modify the design parameters instantaneously. The haptic chair capable of controlling the design parameters in real time was proposed as a haptic simulator. The controllable parameters such as the seat height, reclining angle, stiffness of the backrest, and so on were selected based on the previous researches related to ergonomics chairs. It will reduce the development cost and time by replacing the process of making the real mock-up and prototype with the haptic chair.

• KIEAE Journal
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• v.17 no.3
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• pp.99-106
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• 2017

Purpose: Most modern office buildings adopt the curtain wall system in order to provide occupants with the sense of openness and high-technology, which requires large window area. As a result, the amount of solar radiation increases, negatively affecting cooling load during the summer and increasing energy costs. However, the performance of window itself is not sufficiently controllable parameter to control thermal comfort and solar radiation. Therefore, a shading device such as venetian blind is required to control them and thus a variety of studies have been performed thus far. So, the purpose of this study is to improve the performance of blind through the development of blind control algorithm. Method: Among various input variables for the control of venetian blinds, the vertical solar radiation has been selected in this study as the primary input variable and the optimal control algorithm for venetian blinds were developed for each window orientation. Result: The developed optimal control algorithm has a positive effect on building energy savings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1341-1346
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• 2001

In this study, the acoustic properties of steel-wire sound absorbing materials with different thickness and bulk density were investigated in terms of characteristic impedance, propagation constant, and absorption coefficient. The well-known two-cavity method was used for evaluating those acoustic parameter values in experiments. Also, in order to validate the experimentally measured values, the results were compared with the results obtained from Chung and Blaser's transfer function method and SWR method. The experimentally measured values of normal absorption coefficients were generally agreed well with the corresponding values from the transfer function method and the SWR method. Based on the experimental results, the following conclusions could be made. The magnitude of the absorption coefficient and the frequency range of the maximum absorption coefficient were controllable by changing the thickness and bulk density of the sound absorbing materials. Also, the magnitude of the absorption coefficient depended on the characteristic impedance and the propagation constant. As large as the air cavity depth at the rear side of the steel-wire sound absorbing materials, the maximum magnitude of the absorption coefficient occurred at the lower frequency ranges.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1967-1974
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• 1991

When the functional electrical stimulation is employed to recover mobility to the plegic, it is very important to understand functions of the selected muscles. I have investigated how a muscle acts to accelerate the body segments, since the body segements are connected by joints so that contraction of a muscle not only rotates the segments to which it is attached but also causes other segments to rotate by creation a reaction force at every joint, which is called the inertial coupling. I found that a single-joint muscle always acts to accelerate the spanned joint in the same direction as the joint torque produced by the muscle. However, a double-joint muscle can act to accelerate the spanned joint in the opposite direction to the joint torque produced by the muscle depending on (1) the body position, (2) the body-segmental parameters, and (3) the type of the movement. Investigating the condition number of the inertia matrix of the body-segmental model gave us some insights into how controllable the body-segmental system is for different values of the factors mentioned above. The results suggested that the upright position is the most undesirable position to independently control the three segments(trunk, thigh and shank) and that the controllability is the most sensitive to variation of the shank length and the trunk mass, which implies that accuracy is required particularly when we estimate these two body-segmental parameters before the paralyzed muscles are innervated by using electrical stimulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.192-200
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions for passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed, which is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper that offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-off becomes smooth when the fixed orifice size increases, which means that the blow-off slope is controllable using the fixed orifice size. The damping force variance is wide and continuous, and is controlled by the spool opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.65-70
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• 2012

In this paper, a compact UWB (Ultra Wideband) BPF(Band-Pass Filter) with dual notched bands is proposed using a hybrid Composited Right-Left Handed (CRLH) and Defected Ground Structure (DGS). To avoid the interferences such as Wireless LAN (Center frequency: 2.4GHz and 5.8GHz), the CRLH is employed to obtain the dual notched bands and the DGS is used to obtain the wide stop-band above the pass-band. The fabricated filter has good performance and has more than 30dB rejection at the center frequency of 2.4 GHz and 5.8GHz. The dual notched bands are easily movable by changing the CRLH parameter. Also the insertion loss is less than 0.4dB in the lower pass-band and 0.7dB in the upper pass-band, and it has small group delay variation less than 0.6ns. The size of the fabricated filter is very compact (17mm*17mm).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.1
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• pp.40-49
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• 2008

Interior permanent magnet synchronous motor(IPMSM) has become a popular choice in electric vehicle applications and so of due to their excellent power to weight ratio. To obtain maximum efficiency in these applications, this paper proposes the neural network control method. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the error back propagation algorithm(EBPA) of neural network. The minimization of loss is possible to realize eHciency optimization control for the IPMSM drive. This paper proposes high performance and robust control through a real time calculation of parameter variation such as variation of back emf constant, armature resistance and d-axis inductance about the motor operation. Proposed algorithm is applied IPMSM drive system, prove validity through analysis operating characteristics con011ed by efficiency optimization control.