• 전자공학회논문지SC
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• 제44권6호
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• pp.21-28
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• 2007

Mutiresolution proportional-integral-derivative(MRPID) 제어기는 웨이브렛 기반의 다해상도 응답을 이용해서 에러 신호에 포함되어 있는 잡음과 외란을 제거하는 필터 역할을 해준다. 다해상도 응답의 특징상 샘플링 주파수가 높을 경우 상대적으로 고주파성분이 남아있음으로 인해 응답속도가 떨어지는 대신에 오버슈트가 제거되고, 낮을 경우 신호 성분이 제거되므로 인해 응답속도가 향상되지만 오버슈트가 증가 되는 결과를 보였다. 본 논문에서는 proportional-integral-derivative(PID) 제어기와 MRPID 제어기의 응답을 이용한 샘플링 주파수를 설정하는 기법과, MRPID 제어기의 특성을 고려한 파라미터 설정기법을 제안한다. 모의실험을 통해서 제안된 기법의 타당성을 검증하였다.

• 전기학회논문지P
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• 제59권2호
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• pp.173-178
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• 2010

Frequency is an important operating parameter of a power system. Due to the sudden change in generation and loads or faults in power system, the frequency is supposed to deviate from its nominal value. It is essential that the frequency of a power system be maintained very close to its nominal frequency. And monitoring and an accurate estimation of the power frequency by timing synchronized signal provided by FDR is essential to optimum operation and prevention for wide area blackout. As most conventional frequency estimation schemes are based on DFT filter, it has been pointed out that the gain error by change in magnitude could cause the defects when the power frequency is deviated from nominal value. In this paper, an advanced frequency estimation scheme using gain compensation for fault disturbance recorders (FDR) is presented. The proposed scheme can reduce the gain error caused when the power frequency is deviated from nominal value. Various simulation using both the data from EMTP package and user's defined arbitrary signals are performed to demonstrate the effectiveness of the proposed scheme. The simulation results show that the proposed scheme can provide better accuracy and higher robustness to harmonics and noise under both steady state tests and dynamic conditions.

• 한국정밀공학회지
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• 제22권1호
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• pp.53-60
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• 2005

The wire rope of container crane is a important component to container transfer system and is used in a myriad of various applications such as elevator, mine hoist, construction machinery, and so on. If it happen wire rope failures in operating, it may lead to the safety accident and economic loss, which is productivity decline, competitive decline of container terminal, etc. To solve this problem, we developed the active and portable wire rope fault detecting system. The developed system consists of three parts that are the fault detecting, signal processing, and remote monitoring part. All detected signal has external noise or disturbance according to circumstances. Therefore we applied to discrete wavelet transform to extract a signal from noisy data that was used filter. As experimental result, we can reduce the expense for container terminal because of extension of exchange period of wire rope for container crane and this system is possible to apply in several fields to use wire rope.

• International Journal of Automotive Technology
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• 제8권6호
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• pp.753-760
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• 2007

In this paper, a roll and pitch estimation algorithm using a set of accelerometers and wireless sensor networks(S/N) is presented for use in a passenger vehicle. While an inertial measurement unit(IMU) is generally used for roll/pitch estimation, performance may be degraded in the presence of longitudinal acceleration and yaw motion. To compensate for this performance degradation, a new roll and pitch estimation algorithm is proposed that uses an accelerometer array, global positioning system(GPS) and in-vehicle networks to get information from yaw rate and roll rate sensors. Angular acceleration and roll and pitch approximation are first calculated based on vehicle kinematics. A discrete Kalman filter is then applied to estimate both roll and pitch more precisely by reducing noise from the running engine and from road disturbance. Finally, the feasibility of the proposed algorithm is shown by comparing its performance experimentally with that of an IMU in the framework of an indoor test platform as well as a test vehicle.

• 로봇학회논문지
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• 제10권1호
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• pp.1-8
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• 2015

This paper proposes a study for accurate surface localization system using DWT(Discrete Wavelet Transform) and GPS/INS fusion algorithm. Because the propagation in the underwater is not passed by characteristics of the medium unlike the ground, the sonar system like DVL is used instead of GPS. But since these systems are installed on the seafloor and operated, a long time is required for installation and navigation systems are limited outside of the range area. And it is difficult to estimate position in a three-dimensional considering the depth in actual marine environment. In this paper, before the development of underwater localization system, precisely estimated position system is proposed in a two-dimensional by developing surface localization system using removing noise and disturbance with DWT and relatively inexpensive GPS and INS sensor.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.359-365
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• 2008

As housing supply ratio has become over 100%, the strategic vision of government's policies has been changed from new construction to maintenance and regeneration of old architectural-structures. This fact has brought a light on the reconstruction and remodeling industries and a need for retrofit and rehabilitation techniques of existing foundation. Various methods of foundation for architectural-structures do exist. Among them, micropiling technologies are increasingly applied in foundation rehabilitation and seismic retrofitting projects. Micropiling techniques provide environmental-friendly methods for minimizing disturbance to adjacent structures, ground, and the environment. The installation is possible in restrictive area and general ground conditions. The fact that the installation procedures cause minimal vibration and noise and require very low ceiling height makes the micropiling methods to be commonly used for underpin existing structures. Specialized drilling equipment is often required to install the micropiles for existing basement facilities. This paper presents a case study in which micropiles were constructed to support a superstructure for vertical extension of existing elevator core and provide accessibility to underground parking lot. It is intended to become useful reference for the similar remodeling project.

• 한국군사과학기술학회지
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• 제12권4호
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• pp.540-547
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• 2009

In the near future, military robots are likely to be substituted for military personnel in the field of battle. The power system of a legged robot is considerably more complex than the one used for a land vehicle because of the coordination and stability issues due to the large number of degree of freedom. In this paper, a servovalve-piston combination system for a straight-line motion of robot leg is modeled as three degree of freedom based on double inputs and single output transfer function. The output is the displacement of piston from neutral. The inputs are valve displacement from neutral and arbitrary load force in this system. LQR(Linear Quadratic Regulator) technique is applied in order to achieve robust stability and fast responses of the system. The Kalman filter loop, rejection of disturbance and noise, riccati equation, filter gain matrix, and frequency domain equality are analyzed and designed.

• 제어로봇시스템학회논문지
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• 제19권9호
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• pp.839-845
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• 2013

A CSTR (Continuous Stirred Tank Reactor) is a highly nonlinear process with varying parameters during operation. Therefore, tuning of the controller and determining the transition policy of controller parameters are required to guarantee the best performance of the CSTR for overall operating regions. In this paper, a methodology employing the 2DOF (Two-Degree-of-Freedom) PID controller, the anti-windup technique and a fuzzy gain scheduler is presented for the temperature control of the CSTR. First, both a local model and an EA (Evolutionary Algorithm) are used to tune the optimal controller parameters at each operating region by minimizing the IAE (Integral of Absolute Error). Then, a set of controller parameters are expressed as functions of the gain scheduling variable. Those functions are implemented using a set of "if-then" fuzzy rules, which is of Sugeno's form. Simulation works for reference tracking, disturbance rejecting and noise rejecting performances show the feasibility of using the proposed method.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.42-54
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• 2016

A hybrid color and grayscale images encryption scheme based on the quaternion Hartley transform (QHT), the two-dimensional (2D) logistic map, the double random phase encoding (DRPE) in gyrator transform (GT) domain and the three-step phase-shifting interferometry (PSI) is presented. First, we propose a new color image processing tool termed as the quaternion Hartley transform, and we develop an efficient method to calculate the QHT of a quaternion matrix. In the presented encryption scheme, the original color and grayscale images are represented by quaternion algebra and processed holistically in a vector manner using QHT. To enhance the security level, a 2D logistic map-based scrambling technique is designed to permute the complex amplitude, which is formed by the components of the QHT-transformed original images. Subsequently, the scrambled data is encoded by the GT-based DRPE system. For the convenience of storage and transmission, the resulting encrypted signal is recorded as the real-valued interferograms using three-step PSI. The parameters of the scrambling method, the GT orders and the two random phase masks form the keys for decryption of the secret images. Simulation results demonstrate that the proposed scheme has high security level and certain robustness against data loss, noise disturbance and some attacks such as chosen plaintext attack.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.93-102
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• 2017

Wireless MEMS sensors have common features such as wireless communication, data measurement, embedded processing, battery-based self-power, and low cost, and increased measurement effectiveness. Wireless MEMS sensors enable efficient SHM without interfering with location because there is no requirement for triboelectric noise and cumbersome cables. However, there is little research on the communication distance with sensors and data. For instance, existing researches have limited communication distance experiments in civil engineering bridges. It is also necessary to investigate the characteristics of dynamic behavior and the communication distance of architectural structures with different wireless transmission/reception environments. Therefore, in a building structure with walls and slabs instead of open spaces, MEMS sensors and data loggers were used as distance experiments where communication disturbance between the vertical slab and the horizontal wall could actually be communicated.