• 한국정보통신학회논문지
• /
• 제18권3호
• /
• pp.510-518
• /
• 2014

본 연구에서는 유체 속에서의 로봇의 방향전환 메커니즘의 성능을 개선하고 최적화하기 위하여 물 속 자연환경에 최적화되어 있는 물고기의 CST(CST:C-shape sharp turn) 패턴을 모방하여 물고기 로봇의 꼬리 관절 궤적을 신경회로망(neural network)을 사용하여 제안하였다. 물고기의 CST 패턴을 모방하기 위해 CST 패턴을 순차적으로 기록한 정보를 수치적으로 변환하여 좌표 데이터를 생성하고 함수화하였다. 함수화된 모션 함수를 물고기 로봇의 상대 관절각으로 변환하였으나, 구해진 상대 관절 궤적은 잉어의 순차적 기록에 의해 구해진 각도이므로 분해능이 떨어져 실제 물고기 로봇의 제어에 적용하기 어렵다. 그러므로 상대 관절 궤적을 일반화 기능이 뛰어난 신경회로망을 사용하여 보간하고 물고기 로봇에 적용하였다. 모의실험을 통하여 신경회로망을 이용한 상대 관절 궤적 함수가 고차의 다항식 궤적 함수에 비하여 물고기 로봇의 CST 모션에 더 좋은 성능을 나타냄을 확인하였다.

• Journal of Communications and Networks
• /
• 제7권4호
• /
• pp.429-437
• /
• 2005

Sensor localization has become an essential requirement for realistic applications over wireless sensor networks (WSN). In this paper we propose an ad hoc localization algorithm that is infrastructure-free, anchor-free, and computationally efficient with reduced communication. A novel combination of distance and direction estimation technique is introduced to detect and estimate ranges between neighbors. Using this information we construct unidirectional coordinate systems to avoid the reflection ambiguity. We then compute node positions using a transformation matrix [T], which reduces the computational complexity of the localization algorithm while computing positions relative to the fixed coordinate system. Simulation results have shown that at a node degree of 9 we get $90\%$ localization with $20\%$ average localization error without using any error refining schemes.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.63.3-63
• /
• 2001

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. In this paper, we propose a three dimensional volume reconstruction method, which is an iterative method and as uniform and simulated algebraic reconstruction technique (USART). In this method, two or more x-ray images projected from different views are needed, and also the geometry of the imaging system need to be a priori identified well. That is to say, the relative locations between the x-ray source, imaging plane and the object should be determined exactly by calibration. To achieve this, we propose a series of coordinate calibration methods of the x-ray imaging system using grid pattern images. Some experimental results of these calibrations is presented and discussed in detail ...

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1992년도 추계학술대회 논문집
• /
• pp.339-343
• /
• 1992

For the analysis of dynamic behavior of dynamic behavior of multibody systems by cartesian coordinate method, maximal sets of generalized coordinates and maximum numbers of differential equation and constraints must be considered. Therefore the inefficiency of the increase of CPU time is occurred. This paper is to analyze the dynamic system by using the relative coordinate method without violating the geometric condition of systems. The graph theory and system topology were used for this study. The dynamic systems could be analyzed by the automatic generation of the informations like equation of motion, constraints, and external forces etc. And the results were compared and verified with dynamic commercial package DADS.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
• /
• pp.641-646
• /
• 2000

A milling process with 45 degree chamfered inserts produces a perfect flat surface only in theory. It is due to many unwanted factors including thermal effect, dynamic effect, the problem of the controller used and the problem of accuracy of the machine tool. In this study, introduced is a method to improve the surface roughness by redesigning of the chamfer angle of the insert, which traditionally has been 45 degree. First, the relationship between the fixed machine coordinate and the relative coordinate on the insert is derived. This transfer matrix is used to determine the new insert angle to maximize the flatness of the machined surface. A newly designed insert is manufactured, and used to carry out the experiment. It is proved that the insert designed by the proposed method produced a much flatter surface than a traditional one.

• Journal of Advanced Marine Engineering and Technology
• /
• 제16권1호
• /
• pp.47-53
• /
• 1992

This paper is discussing the Optimum Structural Modification by the Sensitive Analysis Method. The mokificxation for the first Mouth Open Mode of the C type structure was done by using coordinate sensitivities and thickness sensitivities. The results obtained are as follows; 1. the vibration could be minimized by reducing multiples of mode components of impact point and response point. 2. the tooling precision of the Press machine could be minimized by reducing relative vibration amplititutes between the tool and the object to be tooled. 3. the mode componets of 2 points could be identified by using the coordinate sensitivites for the C type structure. 4. the mode components of 2 points could be iodentified by using the thickness sensitivities for the C type structure.

• 한국정밀공학회지
• /
• 제13권6호
• /
• pp.78-89
• /
• 1996

Every mechanical component is fabricated with the variations in its size and shape, and the allowable range of the variation is specified by the tolerance in the design stage. Geometric tolerances specify the size or the thickness of each shape entity itself or its relative position and orientation with respect to datums. Since the range of shape variation can be represented by the variation of the coordinate system attached to the shape, the transformation matrix of the coordinate system would mathematically express the range of shape variation if the interval numbers are inserted for the elements of the transformation matrix. For the shape entity specified by the geometric tolerance with reference to datums, its range of variation can be also derived by propagating the transformation matrices composed of interval numbers. The propagation depends upon the order of precedence of datums.

• Journal of Mechanical Science and Technology
• /
• 제15권6호
• /
• pp.693-698
• /
• 2001

The analysis of actuating forces (or torques) and joint reaction forces (or moments) are essential to determine the capacity of actuators, to control the system and to design the components. This paper presents an inverse dynamic analysis algorithm for flexible multibody systems with closed-loops in the relative joint coordinate space. The joint reaction forces are analyzed in Cartesian coordinate space using the inverse velocity transformation technique. The joint coordinates and the deformation modal coordinates are used as the generalized coordinates of a flexible multibody system. The algorithm is verified through the analysis of a slider-crank mechanism.

• Smart Structures and Systems
• /
• 제23권1호
• /
• pp.15-29
• /
• 2019

This paper addresses the problem of damage detection in suspension bridge hangers, with an emphasis on the modal flexibility method. It aims at evaluating the capability and the accuracy of the modal flexibility method to detect and locate single and multiple damages in suspension bridge hangers, with different level of severity and various locations. The study is conducted numerically and experimentally on a laboratory suspension bridge mock-up. First, the covariance-driven stochastic subspace identification is used to extract the modal parameters of the bridge from experimental data, using only output measurements data from ambient vibration. Then, the method is demonstrated for several damage scenarios and compared against other classical methods, such as: Coordinate Modal Assurance Criterion (COMAC), Enhanced Coordinate Modal Assurance Criterion (ECOMAC), Mode Shape Curvature (MSC) and Modal Strain Energy (MSE). The paper demonstrates the relative merits and shortcomings of these methods which play a significant role in the damage detection ofsuspension bridges.

• 한국정밀공학회지
• /
• 제19권8호
• /
• pp.47-54
• /
• 2002

A barrel cam is used as a very important part of an index drive unit. The index drive unit must have an intermittent-rotational motion. The barrel typed cam and roller gear mechanism has the advantages of high reliability to perform a prescribed motion of a follower. This paper proposes a new method for the shape design of the barrel cam and also a CAD program is developed by using the proposed method. As defined in this paper, the relative velocity method for the shape design calculates the relative velocity of the follower versus cam at a center of roller, and then determines a contact point by using the geometric relationships and the kinematic constraints, where the direction of the relative velocity must be parallel to a common tangential line at the contact point of two independent bodies, i.e. the cam and the follower Then, the shape of the cam is defined by the coordinate transformation of the trace of the contact points. This paper presents two examples for the shape design of the barrel cam in order to prove the accuracy of the proposed methods.