• Title/Summary/Keyword: Position Problem

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Design and Implementation of an Absolute Position Sensor Based on Laser Speckle with Reduced Database

  • Tak, Yoon-Oh;Bandoy, Joseph Vermont B.;Eom, Joo Beom;Kwon, Hyuk-Sang
    • Current Optics and Photonics
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    • v.5 no.4
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    • pp.362-369
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    • 2021
  • Absolute position sensors are widely used in machine tools and precision measuring instruments because measurement errors are not accumulated, and position measurements can be performed without initialization. The laser speckle-based absolute position sensor, in particular, has advantages in terms of simple system configuration and high measurement accuracy. Unlike traditional absolute position sensors, it does not require an expensive physical length scale; instead, it uses a laser speckle image database to measure a moving surface position. However, there is a problem that a huge database is required to store information in all positions on the surface. Conversely, reducing the size of the database also decreases the accuracy of position measurements. Therefore, in this paper, we propose a new method to measure the surface position with high precision while reducing the size of the database. We use image stitching and approximation methods to reduce database size and speed up measurements. The absolute position error of the proposed method was about 0.27 ± 0.18 ㎛, and the average measurement time was 25 ms.

Nonlinear control of an autonomous mobile robot using nonlinear obserbers

  • Ishikawa, Masato;Sampei, Mitsuji
    • 제어로봇시스템학회:학술대회논문집
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    • 1994.10a
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    • pp.400-404
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    • 1994
  • In this paper, we will investigate the position estimation problem for autonomous mobile robots. Formulating this as a state estimation problem for nonlinear SISO system, then we will apply several types of nonlinear observers. Simulation results of observer-based navigation control will be also provided.

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Two-Agent Single-Machine Scheduling with Linear Job-Dependent Position-Based Learning Effects (작업 종속 및 위치기반 선형학습효과를 갖는 2-에이전트 단일기계 스케줄링)

  • Choi, Jin Young
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.38 no.3
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    • pp.169-180
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    • 2015
  • Recently, scheduling problems with position-dependent processing times have received considerable attention in the literature, where the processing times of jobs are dependent on the processing sequences. However, they did not consider cases in which each processed job has different learning or aging ratios. This means that the actual processing time for a job can be determined not only by the processing sequence, but also by the learning/aging ratio, which can reflect the degree of processing difficulties in subsequent jobs. Motivated by these remarks, in this paper, we consider a two-agent single-machine scheduling problem with linear job-dependent position-based learning effects, where two agents compete to use a common single machine and each job has a different learning ratio. Specifically, we take into account two different objective functions for two agents: one agent minimizes the total weighted completion time, and the other restricts the makespan to less than an upper bound. After formally defining the problem by developing a mixed integer non-linear programming formulation, we devise a branch-and-bound (B&B) algorithm to give optimal solutions by developing four dominance properties based on a pairwise interchange comparison and four properties regarding the feasibility of a considered sequence. We suggest a lower bound to speed up the search procedure in the B&B algorithm by fathoming any non-prominent nodes. As this problem is at least NP-hard, we suggest efficient genetic algorithms using different methods to generate the initial population and two crossover operations. Computational results show that the proposed algorithms are efficient to obtain near-optimal solutions.

An Efficient Routing Algorithm for Solving the Lost Link Problem of Vehicular Ad-hoc Networks (차량 애드혹 네트워크의 링크 단절 문제 해결을 위한 효율적인 라우팅 알고리즘)

  • Lim, Wan-Seon;Kim, Sok-Hyong;Suh, Young-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12B
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    • pp.1075-1082
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    • 2008
  • A greedy forwarding algorithm is one of the most suitable solutions for routing in vehicular ad-hoc networks. Compared to conventional routing protocols for mobile ad-hoc networks, greedy forwarding based routing protocols maintain only local information of neighbors instead of per-destination routing entries, and thus they show better performance in highly-mobile vehicular ad-hoc networks. With greedy forwarding, each node learns its geographical position and periodically broadcasts a beacon message including its position information. Based on the position information, each node selects a neighbor node located closest to the destination node as the next forwarder. One of the most serious problems in greedy forwarding is the lost link problem due to the mobility of nodes. In this paper, we propose a new algorithm to reduce the lost link problem. The proposed algorithm aims to find an efficient and stable routing path by taking account of the position of neighbors and the last beacon reception time. Our simulation results show that the proposed algorithm outperforms the legacy greedy algorithm and its variants.

Analysis of Waterproof Time by Number of Twists between Ordinary Fire Hose and Anti-twist Fire Hose (일반 소방호스와 꼬임방지 소방호스의 꼬임 횟수에 따른 방수시간 분석)

  • Hong, Suk-Hwan;Kim, Seo-Young;Kong, Ha-Sung
    • Journal of the Korea Safety Management & Science
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    • v.23 no.4
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    • pp.55-60
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    • 2021
  • This study is to check waterproof by number of twists of fire hose and measure the first waterproof time to analyze the relationship between twists of fire hose and first waterproof time and waterproof by position of twists so as to suggest the efficient plan to prevent twists of fire hose. Ordinary fire hose did not make waterproof in case that position of twists was near the nozzle with twists 5 times or more, while anti-twist fire hose had no problem for waterproof only with delayed time. Like ordinary fire hose, anti-twist fire hose also showed the tendency to increase the waterproof time in proportion to the number of twists. In case that the position of twists was near waterproof port even with 10 times of twists in anti-twist fire hose, the first waterproof time was increase by 0.63 seconds on average without any problem for waterproof, which was somewhat faster than that in ordinary fire hose. With respect to the position of twists, waterproof of anti-twist fire hose was affected more as the number of twists was increased more near the nozzle rather than near the waterproof port, like ordinary fire hose. In summary, anti-twist fire hose equipped with anti-twist tool at the middle connection port and the nozzle showed a good waterproof performance with delayed waterproof time regardless of number of twists, as a solution for the twist problem of ordinary fire hose.

A Study on the Methods for Finding Initial Equilibrium Position of a Lifting Block for the Safe Erection (블록의 탑재 안전성을 위한 초기 평형 자세 탐색 방법 연구)

  • Chun, Do-Hyun;Roh, Myung-Il;Ham, Seung-Ho;Lee, Hye-Won
    • Journal of the Society of Naval Architects of Korea
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    • v.55 no.4
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    • pp.297-305
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    • 2018
  • In a shipyard, block lifting is an important process in the production of ships and offshore structures. Block lifting is a sensitive process because lifting blocks have to be erected with exact positions and orientations. If we use a numerical method for the process, it is important to find tensions of wires and positions of equalizers to maintain the initial equilibrium position of the block. At this time, equations of motion of the block should be solved to calculate the initial equilibrium position of the block. Because the solving technique changes according to the number of equalizers, a suitable equation for the corresponding problem is required. In this study, three types of equations are proposed to find the initial equilibrium position of the block according to the number of equalizers. The Newton-Raphson's method is used to solve nonlinear simultaneous equations and the optimization method is used to determine the appropriate solution to the undetermined problem. To evaluate the applicability of the proposed methods, the dynamic simulations are performed using the tensions calculated from the proposed methods, and the results are discussed. The results show that the proposed methods can be effectively used to determine initial equilibrium position of the block for the block lifting.

A Study on the Sensor Calibration of Motion Capture System using PSD Sensor to Improve the Accuracy (PSD 센서를 이용한 모션캡쳐센서의 정밀도 향상을 위한 보정에 관한 연구)

  • Choi, Hun-Il;Jo, Yong-Jun;Ryu, Young-Kee
    • Proceedings of the KIEE Conference
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    • 2004.11c
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    • pp.583-585
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    • 2004
  • In this paper we will deal with a calibration method for low cost motion capture system using psd(position sensitive detection) optical sensor. To measure the incident direction of the light from LED emitted marker, the PSD is used the output current ratio on the electrode of PSD is proportional with the incident position of the light focused by lens. In order to defect the direction of the light, the current output is converted into digital voltage value by opamp circuits peak detector and AD converter with the digital value the incident position is measured. Unfortunately, due to the non-linearly problem of the circuit poor position accuracy is shown. To overcome such problems, we compensated the non-linearly by using least-square fitting method. After compensated the non-linearly in the circuit, the system showed more enhanced position accuracy.

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A Study on the Position Control of DC servo Motor Usign a Fuzzy Neural Network (퍼지신경망을 이용한 직류서보 모터의 위치 제어에 관한 연구)

  • 설재훈;임영도
    • Journal of the Korean Institute of Intelligent Systems
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    • v.7 no.5
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    • pp.51-59
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    • 1997
  • In this paper, we perform the position control of a DC servo motor using fuzzy neural controller. We use the Fuzzy controller for the position control, because the Fuzzy controller is designed simpler than other intelligent controller, but it is difficult to design for the triangle membership function format. Therefore we solve the problem using the BP learning method of neural network. The proposed Fuzzy neural network controller has been applied to the position control of various virtual plants. And the DC servo motor position control using the fuzzy neural network controller is performed as a real time experiment.

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The Computation of the Voronoi Diagram of a Circle Set Using the Voronoi Diagram of a Point Set: II. Geometry (점 집합의 보로노이 다이어그램을 이용한 원 집합의 보로노이 다이어그램의 계산: II.기하학적 측면)

  • ;;;Kokichi Sugihara
    • Korean Journal of Computational Design and Engineering
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    • v.6 no.1
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    • pp.31-39
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    • 2001
  • Presented in this paper are algorithms to compute the positions of vertices and equations of edges of the Voronoi diagram of a circle set. The circles are located in a Euclidean plane, the radii of the circles are not necessarily equal and the circles are not necessarily disjoint. The algorithms correctly and efficiently work when the correct topology of the Voronoi diagram was given. Given three circle generators, the position of the Voronoi vertex is computed by treating the plane as a complex plane, the Z-plane, and transforming it into another complex plane, the W-plane, via the Mobius transformation. Then, the problem is formulated as a simple point location problem in regions defined by two lines and two circles in the W-plane. And the center of the inverse-transformed circle in Z-plane from the line in the W-plane becomes the position of the Voronoi vertex. After the correct topology is constructed with the geometry of the vertices, the equations of edge are computed in a rational quadratic Bezier curve farm.

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Initialization Problem of Service Robots with Artificial Stars

  • Park, Young-Chul;Im, Jae-Myung;Kim, Jin-Oh
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.2042-2047
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    • 2005
  • Many service robots which is interacting with human at home and in buildings have been developed. Few of them are shown in of the United States and of Japan. These robots are supposed to have a powerful indoor navigation performance in places where human beings live and work. The overall capability of service robots to move around in this environment is called environment correspondence, in which localization problem to find the accurate position and orientation is the most critical problem. While users set up a proper or a best environment for industrial robots, but for services robots at home and in buildings, it is very difficult to change the environment for robots. The expanded workspace due to mobility is difficult to be covered by means of those used for industrial robots because the cost increases and human beings do not want their environment to be changed for robots. This fact has made many researchers study efficient and effective environment correspondence problems. Among these problems, localization is the most difficult. Goal of localization study includes (1) Accurate detection of position and orientation (2) Minimum cost of the additional devices (3) Minimum change of human environment. In this study, as a solution of the above, we propose "Artificial Stars" which are attached on room ceiling as landmarks. In addition, we solve an adoption problem raised when a robot is delivered to a customer site and before it can perform its full navigation capability. We call this as "Initialization Problem" of service robots. We solve the initialization problem for both cases of environment with the map and without map. The proposed system is experimented and has shown how well it handles the initialization problem.

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