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입사각 180˚이상을 갖는 탄성웨지에 의한 Rayleigh파 산란
박경조 여수대학교 2002 論文集 Vol.17 No.-
The steady-state problem of scattering of a incident Rayleigh wave by and elastic wedge whose angle is greater than 180 degrees is considered. The problem is reduced to the numerical solution of a pair of Fredholm integral equations of the second kind whose kernels consist of elementary functions. Numerical results are given for the amplitude and phase of the Rayleigh waves transmitted and reflected by the corner.
박경조,김정엽 여수대학교 산업기술지역개발연구소 2000 産業基術硏究所 論文集 Vol.9 No.-
A novel position control strategy for flexible robot arms based on wave propagation and absorption techniques is presented. The arm is modeled by a lumped-parameter mass-spring system with an actuator at one end and a load mass at the other. The actuator is required to position the remote load and, simultaneously, to provide active vibration damping. It does so by propagating mechanical waves through the system and absorbing reflected waves. Only the first two masses and springs needs to be characterized and observed to determine the required actuator movement. The control algorithm is robust and compares very favorably with the time-optimal performance of bang-bang control. It is also inherently adaptive.
음향방출기법을 이용한 경동, 대형회전체 안전진단 기술개발
박경조 여수대학교 2002 論文集 Vol.17 No.-
A method is presented for diagnosing a large-scale, tilting machine by using acoustic emissions. First of all, the flaking mechanism causing the large-scale bearing for furnace to defect is investigated and verified by Finite Element method. The dagnosis logic is proposed for detecting the flaw of a non-continuous rotating machine. It is proved that the acoustic emission energy can be used as a representative parameter for an acoustic event. Applyig the method to the tilting bearings for steel mill in operation, the effectiveness of this logic is evaluated. From the results, it is shown that AE signal is generated only when the bearing is tilting, and the trend analysis can be focused upon this process.
충돌회피 및 잔류진동 감소를 위한 여유자유도, 탄성 로봇 매니퓨레이터 경로설계
박경조 여수대학교 1998 論文集 Vol.13 No.2
A method is presented for generating the path which significantly reduces residual vibration of the redundant, flexible robot manipulator in the presence of obstacles. The desired path is optimally designed so that the system completes the required move with minimum residual vibration, avoiding obstacles. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinates, called VLCS, to represent the link flexibility. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of desidgn variables. A three-link manipulator is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate path, in the presence of obstacles.
박경조 麗水大學校 産業基術硏究所 1999 産業基術硏究所 論文集 Vol.8 No.-
This paper reviews and summarizes the methods and techniques regarding to the recent developments in marine control system. Especially, this paper is focused upon auto-pilot system which controls the stem's angle to reduce the lateral rolling oscillation.
OHV형 캠-밸브기구의 동적 모델링 및 엔진 성능 개선을 위한 캠형상 설계
박경조 麗水水産大學校産業技術硏究所 1997 産業基術硏究所 論文集 Vol.6 No.-
In this work, a numerical and experimental study was done to get an optimum cam profile considering dynamic characteristics of a cam-valve system. First of all, a four d.o.f. dynamic model was set up for an OHV type cam-valve system. The optimum process was performed with the model into the direction of minimizing the valve acceleration while not modifying original cam shape greatly. Also another optimization which aims to enlarge the valve displacement area while reducing the peak valve acceleration, was tried. The optimization profile was tested experimentally and found that the measured valve displacement and pushrod force show only very small error from the analytically predicted model simulation results.
박경조 여수대학교 1997 論文集 Vol.11 No.2
The dynamic motion analysis of redundant robot manipulators based on flexible arm models are considered. Dynamic equations and actuator torques required for a flexible arm to make a point-to -point motion are formulated and computed by special moving coordinate systems, called virtual rigid link coordinates. Dynamic deformations of the flexible arm can be represented in a simple and compact form with use of the virtual coordinate systems. This method is applied to a three link arm, redundant manipulator in plane motion only.
단일 센서와 모드해석을 이용한 박판 음향방출의 위치 표정
박경조 한국동력기계공학회 2019 동력시스템공학회지 Vol.23 No.6
이 논문에서는 음향방출 신호의 모드 특성을 이용하여 위치표정에 사용되는 센서의 개수를 감소시키는 방법에 대해 조사한다. 이를 위해 첩릿변환과 모달 음향방출의 이론을 평판의 탄성파 전파에 적용한다. 분산선도를 이용하여 첫 번째 도착 모드를 분리하고 이를 이용하여 모드들의 도달 시간 및 음원과 센서 사이의 직선거리를 추정한다. 그리고 해석적 모델을 이용하여 나중에 도착하는 신호들을 계산하고 이를 이용하여 시험 결과와 해석 결과와의 상관관계를 규명하여 음향방출 음원의 위치표정을 수행한다. 제안된 방법의 타당성을 검증하기 위해 강판에 연심파단(pencil lead break, PLB) 시험을 수행하여 음향방출을 모사하고, 측정된 음향방출 신호에 제안된 방법을 적용하여 유용성을 입증한다.
박경조,김정엽 여수대학교 2001 論文集 Vol.16 No.-
This paper describes a new approach for non-destructive evaluation and the structural health monitoring with a high frequency impedance-based technique and wave propagation measurement. This new technique utilizes the direct and the converse electro-mechanical properties of piezoceramic(PZT) patches which are used as actuator-sensors to provide a low-power driven constant voltage dynamic excitation, and to record the modulated current flow through the structure. Elastic waves can be generated in structure by using PZT transducers. Therefore, it relies on tracking the electrical point impedance to identify incipient level damage. The wave may be used to obtain fundamental properties of the structural or to locate flaws.