• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1222-1227
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• 1990

The problem of identification of continuous systems is considered when both the discrete input and output measurements are contaminated by white noises. Using a predesigned digital low-pass filter, a discrete-time estimation model is constructed easily without direct approximations of system signal derivatives from sampled data. If the pass-band of the filter is designed so that it includes the main frequencies of both the system input and output signals in some range, the noise effects are sufficiently reduced, accurate estimates can be obtained by least squares(LS) algorithm in the presence of low measurement noises. Two classes of filters(infinite impulse response(IIR) filter and finite impulse response(FIR) filter) are employed. The former requires less computational burden and memory than the latter while the latter is suitable for the bias compensated least squares(BCLS) method, which compensates the bias of the LS estimate by the estimates of the input-output noise variances and thus yields unbiased estimates in the presence of high noises.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.145-150
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• 2013

A novel AC to DC PWM converters with unity input power factor are proposed to overcome the above shortcoming. The main function of these converters is to shape the input line current to force it exactly in phase with the input AC voltage. Therefore, the input power factor can be improved to near unity and the input current harmonics can be eliminated. In this paper, half-bridge converter with two active switches and two diodes are utilized for low-cost type UPS configuration. By having only two semiconductors in the current path at any time, losses can be reduced over the conventional boost topology. Also, this converter provides controllable dc-link voltage, high power factor, and low cost type converter by simple power circuits. Simulation results show that the proposed half-bridge converter/inverter control technique can be applied to single-phase low-cost type UPS systems successfully.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.10
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• pp.3458-3478
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• 2022

Automatic modulation recognition is the core algorithm in the field of modulation classification in communication systems. Our investigations show that deep learning (DL) based modulation recognition techniques have achieved effective progress for multiple-input multiple-output (MIMO) systems. However, network complexity is always an additional burden for high-accuracy classifications, which makes it impractical. Therefore, in this paper, we propose a low-complexity dimensional interactive lightweight network (DilNet) for MIMO systems. Specifically, the signals received by different antennas are cooperatively input into the network, and the network calculation amount is reduced through the depth-wise separable convolution. A two-dimensional interactive attention (TDIA) module is designed to extract interactive information of different dimensions, and improve the effectiveness of the cooperation features. In addition, the TDIA module ensures low complexity through compressing the convolution dimension, and the computational burden after inserting TDIA is also acceptable. Finally, the network is trained with a penalized statistical entropy loss function. Simulation results show that compared to existing modulation recognition methods, the proposed DilNet dramatically reduces the model complexity. The dimensional interactive lightweight network trained by penalized statistical entropy also performs better for recognition accuracy in MIMO systems.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.114-119
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• 1991

An input estimation technique for tracking filter(CHP algorithm) suggested by Y.T. Chan et. al. has bad performance for low maneuvering targets. In this paper, two maneuver detection algorithms are applied to Singer's target model. First, an CHP input estimation technique is applied to 9 state target model. Second, we construct a maneuver detection and correction technique using pseudo acceleration measurements, which are derived directly from measurements. These two filters have good performance for even the low maneuvering targets.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.29-34
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• 2007

The input and output impedances in a low voltage distribution system is one of the most important matters for power line communication because from the viewpoint of communication, the attenuation characteristic of the high frequency signals is greatly caused by impedance mismatch during sending and receiving. The frequency range is from 1MHz to 30MHz. Therefore, this paper investigates the input and output impedances in order to understand the characteristic of high frequency signals in the low voltage distribution system between a pole transformer and an end user. For power line communication, the model of Korea's low voltage distribution system is proposed in a residential area and then the low voltage distribution system is set up in a laboratory. In the low voltage distribution system, S parameters are measured by using a network analyzer. Finally, input and output impedances are calculated using S parameters.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.8
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• pp.883-888
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• 1999

To obtain high positioning auccuracy for a long, flex bleman Ipulator, residual vibration must be removed from the tip motion. But it is difficult to control the vibration of low frequency. There are open-loop and closed loop methods in the elimination of the residual vibration. We inroduce input shaping technique has been used as a simple open-loop method of controlling the residual vibration of a flexible manipulator. Design of input shaper in the continuous time domain is complicated. This paper presents a new technique that designs input shaper in the z-domain and analyzes input shaping method in the z-domain. This technique is simple and easy to design input shaper.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.890-893
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• 2008

In this paper, we present a low complexity modified multi-level sphere decoder (SD) for multiple-input multiple-output (MIMO) systems employing quadrature amplitude modulation (QAM) signals. The proposed decoder, exploiting the multi-level structure of the QAM signal scheme, first decomposes the high-level constellation into low-level 4-QAM constellations, so-called sub-constellations. Then, it deploys SD in the sub-constellations in parallel. In addition, in the searching stage, it uses the optimal low-complexity sort method. Computer simulation results show that the proposed decoder can provide near optimal maximum-likelihood (ML) performance while it significantly reduces the computational load.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.1975-1987
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• 2005

An input time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via digital computers. In this paper a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed. The mathematical structure of the new discretization method is analyzed. On the basis of this structure the sampled-data representation of nonlinear systems with time-delayed multi-input is presented. The delayed multi-input general equation has been derived. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. Additionally, hybrid discretization schemes that result from a combination of the scaling and squaring technique (SST) with the Taylor series expansion are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method's parameters to meet CPU time and accuracy requirements, are examined as well. A performance of the proposed method is evaluated using a nonlinear system with time delay maneuvering an automobile.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.85-90
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• 2012

This paper presents a topology structure and control method for an input-parallel-output-series(IPOS) inverter system which is suitable for high input current, high output voltage, and high power applications. In order to ensure the normal operation of the IPOS inverter system, the control method should achieve input current sharing(ICS) and output voltage sharing(OVS) among constituent modules. Through the analysis in this paper, ICS is automatically achieved as long as OVS is controlled. The IPOS inverter system is controlled by a three-loop control system which is composed of an outer common-output voltage loop, inner current loops and voltage sharing loops. Simulation results show that this control strategy can achieve low total harmonic distortion(THD) in the system output voltage, fast dynamic response, and good output voltage sharing performance.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.161-162
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• 2008

In this paper we design an irregular low-density parity-check (LDPC) code for a multi-input multi-output (MIMO) system. The considered MIMO system is minimum mean square error soft-interference cancellation (MMSE-SIC) detector. The MMSE-SIC detector and the LDPC decoder exchange soft information and consist a turbo iterative detection and decoding receiver. Extrinsic information transfer (EXIT) charts are used to obtain the edge degree distribution of the irregular LDPC code which is optimized for the input-output transfer chart of the MMSE-SIC detector. It is shown that the performance of the designed LDPC code is much better than that of conventional LDPC code optimized for the AWGN channel.