• Smart Structures and Systems
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• v.5 no.3
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• pp.261-277
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• 2009

A fuzzy-sliding mode controller is presented to control the dynamics of semi-active suspension systems of vehicles using magneto-rheological (MR) fluid dampers. A full car model is used to design and evaluate the performance of the proposed semi-active controlled suspension system. Four mixed mode MR dampers are designed, manufactured, and integrated with four independent sliding mode controllers. The siding mode controller is designed to decrease the energy consumption and maintain robustness. In order to overcome the chattering of the sliding mode controllers, a fuzzy logic control strategy is merged into the sliding mode controller. The proposed fuzzy-sliding mode controller is designed and fabricated. The performance of the semi-active suspensions is evaluated in both the time and frequency domains. The obtained results demonstrate that the proposed fuzzy-sliding mode controller can effectively suppress the vibration of vehicles and improve their ride comfort and handling stability. Furthermore, it is shown that the "chattering" of the sliding mode controller is smoothed when it is integrated with a fuzzy logic control strategy. Although the cost function of the fuzzy-sliding mode control is a slightly higher than that of a classical LQR controller, the control effectiveness and robustness are enhanced considerably.

• Smart Structures and Systems
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• v.32 no.1
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• pp.1-7
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• 2023

In modal analysis, the mode shape reflects the vibration characteristics of the structure, and thus it is widely performed for finite element model updating and structural health monitoring. Generally, the acceleration-based mode shape is suitable to express the characteristics of structures for the translational vibration; however, it is difficult to represent the rotational mode at boundary conditions. A tilt sensor and gyroscope capable of measuring rotational mode are used to analyze the overall behavior of the structure, but extracting its mode shape is the major challenge under the small vibration always. Herein, we conducted a feasibility study on a multi-mode shape estimating approach utilizing a single physical quantity signal. The basic concept of the proposed method is to receive multi-metric dynamic responses from two sensors and obtain mode shapes through bridge loading test with relatively large deformation. In addition, the linear transformation matrix for estimating two mode shapes is derived, and the mode shape based on the gyro sensor data is obtained by acceleration response using ambient vibration. Because the structure's behavior with respect to translational and rotational mode can be confirmed, the proposed method can obtain the total response of the structure considering boundary conditions. To verify the feasibility of the proposed method, we pre-measured dynamic data acquired from five accelerometers and five gyro sensors in a lab-scale test considering bridge structures, and obtained a linear transformation matrix for estimating the multi-mode shapes. In addition, the mode shapes for two physical quantities could be extracted by using only the acceleration data. Finally, the mode shapes estimated by the proposed method were compared with the mode shapes obtained from the two sensors. This study confirmed the applicability of the multi-mode shape estimation approach for accurate damage assessment using multi-dimensional mode shapes of bridge structures, and can be used to evaluate the behavior of structures under ambient vibration.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.86-90
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• 2017

In this study, a novel third-order bandpass filter, which is based on a rectangular closed loop resonator, is presented. By adding a series resonator to the conventional loop resonator, the resonator's even resonant mode is split into two modes, while the odd resonant mode is not affected. Therefore, by varying the values of the series resonator elements, the resonant frequencies of two even modes can be determined independent of the odd-mode resonant frequency. In the proposed triple-mode filter design, instead of using a lumped series resonator, a T-shaped transmission line is coupled to the resonator via a small gap. To verify the design method, a filter is designed at 2.4 GHz with a bandwidth of 100 MHz. The improved performances of the proposed triple-mode filter are compared with those of the conventional dual mode filter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1199-1203
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• 2012

H.264 adopted many compression tools to increase image data compression efficiency such as B frame bi-directional predictions, the direct mode coding and so on. Despite its high compression efficiency, H.264 can suffer from its long coding time due to the complicated tools of H.264. To realize a high performance H.264, several fast algorithms were proposed. One of them is adaptive fast direct mode decision algorithm using mode and Lagrangian cost prediction for B frame in H.264/AVC (MLP) algorithm which can determine the direct coding mode for macroblocks without a complex mode decision process. However, in this algorithm, macroblocks not satisfying the conditions of the MLP algorithm are required to process the complex mode decision calculation, yet suffering a long coding time. To overcome the problem, this paper proposes a fast direct mode prediction algorithm. Simulation results show that the proposed algorithm can determine the direct mode coding without a complex mode decision process for 42% more macroblocks and, this algorithm can reduce coding time by up to 23%, compared with Jin's algorithm. This enables to encode B frames fast with a less quality degradation.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.57-65
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• 2016

In this paper, based on the mode analysis of four-conductor lines, the extended mixed-mode chain-parameters and S-parameters of four-conductor lines are estimated using current division factors. The extended mixed-mode chain-parameters of cascaded four-conductor lines are then obtained with mode conversion. And, the extended mixed-mode S-parameters of cascaded four-conductor lines can be predicted from the transformation of the extended chain-parameters. Compared to the extended mixed-mode S-parameters of four-conductor lines, the cross-mode S-parameters are induced in the extended mixed-mode S-parameters of cascaded four-conductor lines, due to the imbalanced current division factors of cascaded two sections. The generated cross-mode S-parameters make the equivalent different- and common-mode conductors not independent from each other again. In addition, a new mode conversion, which applies the imbalanced current division factors, between the extended mixed-mode S-parameters and standard S-parameters is also proposed in this paper. Finally, the validity of the proposed extended mixed-mode S-parameters and mode conversion is confirmed by a comparison of the simulated and estimated results of shielded cable.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.18-20
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• 2008

An electrical balance of plant(EBOP) of a 600kW molten carbonate fuelcell (MCFC) has to transit from grid-connected(GC) mode to grid-independent(GI) mode when a grid is in a fault conditions. A minimum transition time is limited by four cycle for a 600kW MCFC to ride through a grid fault. In this paper, we propose a control algorithm of a 600kW EBOP for a MCFC system. The EBOP has three operation modes, i.e., GC mode, GI mode, and grid-synchronized(GS) mode. The EBOP controls output currents in a GC mode and regulates output voltages in GI or GS mode. GS mode is defined as an interface between GC mode and GI mode to make a mode transition smooth, i.e., limitation of inrush currents, regulation of output voltages within ANSI standard. Simulations and experiments carried out to verify the effectiveness of the proposed control algorithm.

• Smart Structures and Systems
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• v.23 no.2
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• pp.195-205
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• 2019

An accurate non-model-based method for delamination identification of laminated composite plates is proposed in this work. A weighted mode shape damage index is formulated using squared weighted difference between a measured mode shape of a composite plate with delamination and one from a polynomial that fits the measured mode shape of the composite plate with a proper order. Weighted mode shape damage indices associated with at least two measured mode shapes of the same mode are synthesized to formulate a synthetic mode shape damage index to exclude some false positive identification results due to measurement noise and error. An auxiliary mode shape damage index is proposed to further assist delamination identification, by which some false negative identification results can be excluded and edges of a delamination area can be accurately and completely identified. Both numerical and experimental examples are presented to investigate effectiveness of the proposed method, and it is shown that edges of a delamination area in composite plates can be accurately and completely identified when measured mode shapes are contaminated by measurement noise and error. In the experimental example, identification results of a composite plate with delamination from the proposed method are validated by its C-scan image.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.241-245
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• 1995

This paper shows that the proposed fuzzy-sliding mode for SCARA robot control could reduce chattering problemed in sliding mode control and is robust against parameter uncertainties. It was very small quantities of chattering in the fuzzy-sliding mode control conpared with that in sliding mode control with two dead-band. In here, the sliding mode control with two dead-band is the method to reduce some chattering by changing into a continuous variable lower control input gain when a state value in pahase palne converged sithin two dead-band. But, the fuzzy-sliding mode control for more reducing chattering is the method to change control input by slicing mode into that by fuzzy rule within two dead-band. Simulations show that the effect of reducing chattering by the fuzzy-sliding mode is superior to sliding mode control with two dead-band.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.7
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• pp.374-379
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• 2006

The switch mode power supply is a source of EMI with other equipment as well as with its own proper operation because of rapid changes in voltages and currents within a switching converter. The EMI is transmitted in two forms: radiated and conducted. Conducted noise consists of two categories known as the differential mode and the common mode. Common mode noise current is a major source of EMI in the switch mode Power supply. Recently, a current balancing technique has been studied to reduce the common mode noise. This paper investigates the reduction of common mode noise according to a node expansion of the switch mode power supply which is based on a current balancing technique. In this paper, seven PCB patterns of the forward converter are manufactured and experimented.

• Structural Engineering and Mechanics
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• v.36 no.6
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• pp.697-714
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• 2010

This paper presents an improved version of the Hilbert-Huang transform (HHT) for the modal evaluation of structural systems or signals. In this improved HHT, a well-designed bandpass filter is used as preprocessing to separate and determine each mode of the signal for solving the inherent modemixing problem in HHT (i.e., empirical mode decomposition, EMD, associated with the Hilbert transform). A screening process is then applied to remove undesired intrinsic mode functions (IMFs) derived from the EMD of the signal's mode. A "best" IMF is selected in each screening process that utilizes the orthogonalization coefficient between the signal's mode and its IMFs. Through mode-by-mode signal filtering, parameters such as the modal frequency can be evaluated accurately when compared to the theoretical value. Time history of the identified modal frequency is available. Numerical results prove the efficiency of the proposed approach, showing relative errors 1.40%, 2.06%, and 1.46%, respectively, for the test cases of a benchmark structure in the lab, a simulated time-varying structural system, and of a linear superimposed cosine waves.