• 대한기계학회논문집A
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• 제23권11호
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• pp.1940-1951
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• 1999

In this paper, the equations of motion of a Bernoulli-Euler cantilever beam fixed on a moving cart and carrying a lumped mass concentrated at an arbitrary position along the beam is derived. The motion of the beam-mass-cart system is analyzed through unconstrained modal analysis, and a unified characteristic equation for calculating the natural frequencies of the system is obtained. The changes of natural frequencies and the corresponding mode shapes with respect to the changes in mass ratios of the system and to the concentrated position of the lumped mass are investigated with the frequency equation, which can be generally applied to this kind of systems. The exact and assumed-mode solutions including the dynamics of the base cart are obtained, and the open-loop responses of the system by arbitrarily designed forcing function are given by numerical simulations. The results match well with physical phenomena even at the extreme cases where the concentrated mass is attached to the bottom and to the top of the beam.

• 한국멀티미디어학회논문지
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• 제19권4호
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• pp.747-755
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• 2016

Automated guided vehicles have been used for a long time to increase work efficiency in the logistics field, but it is difficult to apply to a variety of logistics sites due to either the restricted movement mechanism or expensive devices. In this paper, we present a flexible software architecture that is hardware-independent for a mobile power cart of the follow mode and implement it using a ROS software platform. Through the SCV analysis for the system functionalities, we design a package to track a user movement and a package to control a new hardware platform. It has an advantage to use a variety of movement algorithms and hardware platforms by applying the strategy pattern and the template method pattern for the design of a software architecture. Through the performance evaluation, we show that the proposed design is maintainable in terms of a software complexity and it detects a user's movement by obtaining a user skeleton information so that it can control a hardware platform to move at a certain distance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.318-322
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• 1996

This paper presents a technique to control a robot which has a flexible manipulator moving in a vertical plane. The flexible manipulator is modeled as an Euler-Bernoulli beam. Elastic deformation is represented using the assumed modes method. A comparison function which satisfies all geometric and natural boundary conditions of a cantilever beam with an end mass is used as an assumed mode shape. Lagrange's equation is utilized for the development of a discretized model. A control algorithm is developed using a simple PID control technique. The proportional, integral and derivative control gains are determined based on the dominant pole placement method and tuned to show no overshoot and having a short settling time. The effectiveness of the developed control scheme is showed experimentally. In the position control experiment, three different end masses are used. The experimental results shows little overshoot, no steady state error, and less than 2.5 second settling time in case of having an end mass which is equivalent to 45% of the total system weight. Also the residual vibration of the end point is effectively controlled.

• 한국소음진동공학회논문집
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• 제19권1호
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• pp.76-84
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• 2009

The vibration and stability of thin, flexible corotating disks in an enclosed compressible fluid is investigated analytically and compared with the results of a single rotating disk. The discretized dynamical system of the corotating disks is derived in the compact form of a classical gyroscopic system similar with a single disk. For the undamped system, coupled structure-acoustic traveling waves destabilize through mode coalescence leading to flutter instability. However, it is found that the flutter regions of the corotating disks are wider than those of a single disk. A detailed investigation of the effects of dissipation arising from acoustic or disk damping is also performed. Finally, in the presence of both acoustic and disk dampings, the instability regions are found and compared with those of a single disk. Although this study does not allow a radial clearance between the disk and the enclosure, the computational frame work of the problem can be expanded to the system having the radial clearance in an enclosure.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1024-1040
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• 2014

The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.

• 한국정보통신학회논문지
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• 제21권6호
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• pp.1203-1211
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• 2017

본 논문은 유연관절로봇의 추종성능과 정합과 비정합 외란 모두에 대한 강인성을 향상시키기 위한 강인한 제어기를 제안한다. 제안된 제어기는 백스테핑 외란관측기(DOB), 수동성기반 제어기(PBC)와 적분슬라이딩모드 제어기(ISMC)가 백스테핑기법 형태로 구성되어 있다. 백스테핑 DOB는 링크측의 비정합 외란을 고려하는데 사용되며 모터측의 기준입력을 제공하는 역할을 한다. IDA-PBC는 모터측의 추종제어를 수행하며 적분슬라이딩모드제어와 결합될 때 공칭제어기의 역할을 하며 전체 공칭제어시스템의 안정도를 보장받도록 한다. 반면에 적분슬라이딩모드제어는 정합조건을 만족시키는 모터측의 외란의 영향을 제거하는데 사용된다. 링크측의 제어기를 설계하는데 있어서는 PD타입의 임피던스제어기와 DOB가 결합됨으로써 강인한 제어특성과 함께 모터측의 기준입력에 적합한 연속적인 입력의 제공이 가능하도록 하였다.

• 한국항행학회논문지
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• 제18권2호
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• pp.158-164
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• 2014

고품질 초고속 광 신호 전송을 위해서는 그룹 속도 분산과 비선형 현상에 의한 왜곡을 억제하거나 줄여주는 기술이 필요하다. 가장 대표적인 기술로 분산 제어 (DM; dispersion management), 광 위상 공액 기술과 이 둘을 결합한 기술이 있다. 하지만 이러한 기술들에서 현재 사용되고 있는 단일 모드 광섬유의 고정 길이와 중계 구간 당 잉여 분산 (RDPS; residual dispersion per span)의 고정값은 유연한 링크 구성을 제한하고 있다. 본 연구의 목적은 광전송 링크를 구성하는 모든 중계 구간의 SMF 길이와 RDPS의 인위적 분포와 랜덤 분포를 통한 초고속 장거리 광전송 시스템의 유연한 구성 가능성을 살펴보는 것이다. 전송 링크 전체의 평균 RDPS와 입사 전력과 같은 링크 파라미터에 의존하지만 제안한 링크 구조들이 유연한 광전송 시스템 구성에 유용하다는 것을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.169-172
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• 2000

This paper describes design of cryptographic processor which can execute SEED, DES, and triple DES encryption algorithm. To satisfy flexible architecture and area-efficient structure, the processor has I unrolled loop structure with hardware sharing and can support four standard mode, such as ECB, CBC, CFB, and OFB modes. To reduce overhead of key computation, the precomputation technique is used. Also to eliminate increase of processing time due to data input and output time, background I/O technique is used which data input and output operation execute in parallel with encryption operation of cryptographic processor. The cryptographic processor is designed using 2.5V 0.25 $\mu\textrm{m}$ CMOS technology and consists of about 34.8K gates. Its peak performances is about 250 Mbps under 100 Mhz ECB SEED mode and 125 Mbps under 100 Mhz triple DES mode.

• International Journal of Automotive Technology
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• 제3권4호
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• pp.129-135
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• 2002

Durability estimation of a prototype vehicle has traditionally relied heavily on accelerated durability tests using predefined proving grounds or rig tests using a road simulator. By use of those tests, it is very difficult to predict durability failures in actual service environments. This motivated the development of an integrated CAE (Computer Aided Engineering) methodology for the durability estimation of a prototype vehicle in actual service environments. Since expensive computational costs such as computation time and hardware resources are required for a full vehicle simulation in those environments with a very long span of event time, the conventional CAE methodologies have little feasibility. An efficient computational methodology for durability estimations is applied with theoretical developments. The effectiveness of the proposed methodology is shown by the comparison of results of the typical actual service environment such as the city mode with those of the typical accelerated durability test over the Belgian road.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2000년도 춘계학술발표논문집
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• pp.117-120
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• 2000

This paper describe VLSL design of crytographic processor which can execute triple DES and DES encryption algorithm. To satisfy flexible architecture and area-efficient structure, the processor has 1 unrolled loop structure without pipeline and can support four standard mode, such as ECB, CBC, CFB, and OFB modes. To reduce overhead of key computation , the key precomputation technique is used. Also to eliminate increase of processing time due to data input and output time, background I/O techniques is used which data input and output operation execute in parallel with encryption operation of cryptographic processor. The cryptographic processor is implemented using Altera EPF10K40RC208-4 devices and has peak performance of about 75 Mbps under 20 Mhz ECB DES mode and 25 Mbps uder 20 Mhz triple DES mode.