• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.437-442
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• 2000

An alternative inverse feedback structure for adaptive active control of periodic noise is introduced for systems with nonminimum phase cancellation path. To obtain the inverse model of the nonminimum phase cancellation path, the cancellation path model can be factorized into a minimum phase term and a maximum phase term. The maximum phase term containing unstable zeros makes the inverse model unstable. To avoid the instability, we alter the inverse model of the maximum phase system into an anti-causal FIR one. An LMS predictor estimates the future samples of the noise, which are necessary for causality of both anti-causal FIR approximation for the stable inverse of the maximum phase system and time-delay existing in the cancellation path. The proposed method has a faster convergence behavior and a better transient response than the conventional FX-LMS algorithms with the same internal model control structure since a filtered reference signal is not required. We compare the proposed methods with the conventional methods through simulation studies.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.1
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• pp.58-62
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• 1999

This paper shows that is possible to identify the system's input-output dynamics exactly in the presence of unknown periodic disturbances for the Active Engine Mount Control Application .The disturbance frequencies and waveforms can be completely unknown and arbitrary. Only measurements of a control excitation signal and the disturbance-contaminated response are used for identification. Examples are given to illustrate the method, including the identification and vibration control of active engine mount for automobile.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.1050-1056
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• 1994

When a vibration data for a rotating machine such as a pump or a compressor is concerned, the frequency fluctuation of the energy contents at an instant time may provide useful information on understanding the vibration characteristics of the rotating machinery, rather than the averaged energy distribution along the frequency axis. Especially, when a periodic signal has different spectral contents, the approach to use the averaged frequency distribution, called the normal frequency analysis, may not be appropriate to extract vibration source characteristics of the structure. This paper introduces a way to analyze the signal based on an instant time. In order to evaluate the performance of the various approach, the investigatation compares three different algorithms which are frequently implemented in the instantaneous frequency analysis. Also for the noise effect embodied in the true signal, various cases for different SN ratio have been examined. The result shows that the noise level is crucial to evalute the instantaneous frequency analysis. In order to implement the instantaneous frequency analysis, the extraction of the relevant information from the measured signal should have the high S/N ratio, i, e., 40 dB or above.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.1004-1011
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• 2016

In this paper, we suggested the methodology of analyzing and reconstructing of measured electromagnetic emanations from the Micro Controller Unit(MCU) chip of Universal Serial Bus(USB) keyboard. By analyzing electromagnetic emanations, entered information is found at keystroke and furthermore, information security problems such as personal information leakage and eavesdropping can be arisen. USB keyboards make the radiated signal according to the signal transmission mechanism. Electromagnetic emanations were measured by log periodic antenna and wideband receiver and were analyzed by signal processing algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.162-168
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• 2008

In this paper, the RCF(Resistive Companion Form) analysis method is applied to analyze small signal stability of power systems including thyristor controlled FACTS(Flexible AC Transmission System) equipments such as TCSC(Thyristor Controlled Series Capacitor). The eigenvalue sensitivity analysis algorithm in discrete systems based on the RCF analysis method is presented and applied to the power system including TCSC. As a result of simulation, the RCF analysis method is very useful to precisely calculate the variations of eigenvalues or newly generated unstable oscillation modes after periodic switching operations of TCSC. Also the eigenvalue sensitivity analysis method based on the RCF analysis method enabled to precisely calculate eigenvalue sensitivity coefficients of controller parameters about the dominant oscillation mode after periodic switching operations in discrete systems. These simulation results are different from those of the conventional continuous system analysis method such as the state space equation and showed that the RCF analysis method is very useful to analyze the discrete power systems including periodically operated switching equipments such as TCSC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.6
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• pp.303-309
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• 2014

Chaos communication system can improve a system security due to characteristics of non-periodic, non-predictability, broadband signal and easy implementation. Also, chaos signal is sensitive to initial conditions of chaos map. By these reasons, security of chaos communication system is superior to digital communication system. BER performance of COOK modulation system is better than other chaos modulation systems, even if COOK modulation system uses an asynchronous receiver. However, security and safety of COOK modulated signal are worse than other chaos modulation systems, because information bits can be easily predicted from COOK modulated signal. In this paper, for security improvement of COOK modulated signal, we propose a novel Scrambling COOK modulation system by applying the scrambling method. Conventional COOK modulated signal can be predicted, because chaos signal is generated when data is only 1. However, proposed system cannot be predicted, because chaos signal is generated when data is 0 or 1. Therefore, security and safety of transmitted signal in scrambling COOK modulation system is superior to conventional COOK modulation system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1035-1042
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• 1988

The acoustic emission(AE) signal is monitored in milling operation in order to investigate the relationship between the progressive tool wear and the AE signals. A signal processing technique so called time domain averaging(TDA) is presented for the elimination of the influences of the noise imbedded in the periodic signals. The relationship between the progressive tool wear and the AE signals is investigated by varying the cutting speed, feed, depth of cut and the number of insert. From the measured data, it is observed that the averaged level of the AE signal increases at first with the increase of flank wear to a certain critical value, and then stays almost constant or fluctuates with further increase of the flank wear.

• International Journal of Advanced Culture Technology
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• v.7 no.3
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• pp.46-51
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• 2019

This study suggests ways to strengthen the expertise by analyzing the problems caused by the lack of expertise of the qualification management body managing the Korean qualifications in the realm of firefighting from the perspective of external signal dependency of capture theory. As a method to prevent the dependency of external signals in capture theory, it is suggested to strengthen the expertise of regulators and strengthening roles and functions of regulator institutions by supplementing education and professional manpower. On this basis, analyzing the problems of qualifications management to the external signal dependency tendency, the researchers in qualification management at the Human Resources Development Service of Korea have a variety of different majors, so understanding and application can be limited if they are working in an unfamiliar area of work. Therefore, in making decisions regarding topics such as policies and roles, suitable alternatives should be found based on external signals. In order to improve this, it is necessary to select firefighting majors in the Korean qualification management of the firefighting realm, to reorganize the job scope to a similar job field of the researcher in charge. It is also necessary to strengthen the expertise of the researcher through various programs, such as mandatory periodic maintenance education in order to understand the work of the researcher.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.313-316
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• 1997

Two different issues, design of reduced-order robust model predictive control and input signal design for identification of a MIMO system, are addressed and design techniques based on singular value decomposition(SVD) of the pulse response circulant matrix(PRCM) are proposed. For this, we investigate the properties of the PRCM, which is a periodic approximation of a linear discrete-time system, and show its SVD represents the directional as well as the frequency decomposition of the system. Usefulness of the PRCM and effectiveness of the proposed design techniques are demonstrated through numerical examples.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.112-118
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• 2000

A modified repetitive control is formulated and analyzed in the discrete-time domain. Sufficient conditions for the stability of a class of repetitive controllers are given by means of the regeneration spectrum method. When a periodic signal input is drived into the two-mass-spring plant, the performance of the proposed controller which comprises a low-pass filter and two feed-forward compensators, turns out highly accurate by comparing the tracking result from the conventional LQ controller.