• 제어로봇시스템학회논문지
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• 제5권3호
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• pp.314-323
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• 1999

This paper introduces a methodology of active calibration of a camera pose (orientation and position) using the images of cylindrical objects that are going to be manipulated. This active calibration method is different from the passive calibration where a specific pattern needs to be located at a certain position. In the active calibration, a camera attached on the robot captures images of objects that are going to be manipulated. That is, the prespecified position and orientation data of the cylindrical object are transformed into the camera pose through the two consecutive image frames. An ellipse can be extracted from each image frame, which is defined as a circular-feature matrix. Therefore, two circular-feature matrices and motion parameters between the two ellipses are enough for the active calibration process. This active calibration scheme is very effective for the precise control of a mobile/task robot that needs to be calibrated dynamically. To verify the effectiveness of active calibration, fundamental experiments are peformed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.734-739
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• 2003

A new method of estimating the pose of a mobile-task robot is developed based upon an active calibration scheme. The utility of a mobile-task robot is widely recognized, which is formed by the serial connection of a mobile robot and a task robot. For the control of the mobile robot, an absolute position sensor is necessary. This paper proposes an active calibration scheme to estimate the pose of a mobile robot that carries a task robot on the top. The active calibration scheme is to estimate a pose of the mobile robot using the relative position/orientation to a known object whose location, size, and shape are known a priori. Through the homogeneous transformation, the absolute position/orientation of the camera is calculated and that is propagated to getting the pose of a mobile robot. With the experiments in the corridor, the proposed active calibration scheme is verified experimentally.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1431-1442
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• 2003

A new method of estimating the pose of a mobile-task robot is developed based upon an active calibration scheme. The utility of a mobile-task robot is widely recognized, which is formed by the serial connection of a mobile robot and a task robot. To be an efficient and precise mobile-task robot, the control uncertainties in the mobile robot should be resolved. Unless the mobile robot provides an accurate and stable base, the task robot cannot perform various tasks. For the control of the mobile robot, an absolute position sensor is necessary. However, on account of rolling and slippage of wheels on the ground, there does not exist any reliable position sensor for the mobile robot. This paper proposes an active calibration scheme to estimate the pose of a mobile robot that carries a task robot on the top. The active calibration scheme is to estimate a pose of the mobile robot using the relative position/orientation to a known object whose location, size, and shape are known a priori. For this calibration, a camera is attached on the top of the task robot to capture the images of the objects. These images are used to estimate the pose of the camera itself with respect to the known objects. Through the homogeneous transformation, the absolute position/orientation of the camera is calculated and propagated to get the pose of a mobile robot. Two types of objects are used here as samples of work-pieces: a polygonal and a cylindrical object. With these two samples, the proposed active calibration scheme is verified experimentally.

• 한국정밀공학회지
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• 제12권8호
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• pp.73-85
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• 1995

The sensor system to measure the distance precisely from the center of the sensor system to the obstacle is needed to recognize the surrounding environments, and the sensor system is to be calibrated thoroughly to get the range information exactly. This study covers the calibration of the active range sensor which consists of camera and laser slit emitting device, and provides the equations to get the 3D range data. This can be possible by obtaining the extrinsic parameters of laser slit emitting device through image processing the slits measured during the constant distance intervals and the intrinsic parameters from the calibration of camera. The 3D range data equation derived from the simple geometric assumptions is proved to be applicable to the general cases using the calibration parameters. Also the exact 3D range data were obtained to the object from the real experiment.

• 한국ITS학회 논문지
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• 제21권5호
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• pp.162-170
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• 2022

본 논문에서는 256 능동위상배열 기반의 연직바람 관측장비(RWP)의 송수신 채널의 크기 및 위상을 보정하는 방법등이 논의된다. 별도의 모듈 추가 없이 송수신 전단기 및 송수신 전환기에 커플러 및 스위치를 사용하여 송신 및 수신 보정 경로를 확보하였고, Gain 및 Phase Detector를 사용하여 256 송수신 채널의 크기 및 위상을 독립적으로 보정하였다. 보정된 256 능동위상배열 안테나는 근접전계 시험을 통해 5개의 빔 (연직, 동, 서, 남, 북)의 빔폭 및 사이드 로브가 시뮬레이션 계산 값과 일치함을 확인하였다. 제안된 보정방법은 실외 환경에서 운용되는 능동위상배열 기반의 시스템에 용이하게 적용이 가능하다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.519-522
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• 2002

An active phased array antenna consists of many channels. Each channel has a different initial phase shift and gain because of the inequality in the active circuits themselves, interface between radiators and active circuits, and beam-forming circuits and other antenna system configurations. This raises an inherent problem in active phased array antennas. To compensate for this problem the initial phase and gain of each channel should be calibrated. This paper presents an efficient calibration method for an initial phase variation of each channel in active phased array antennas. We tested our method in an active phased array antenna, and obtained good results in the radiation pattern and beam direction of antenna.

• 천문학논총
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• 제12권1호
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• pp.1-21
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• 1997

We have obtained theoretical calibration curves to convert the amount of polarization into the strength of magnetic field, by a numerical calculation of radiation transfer for the polarized spectral line of FeI $6303{\AA}$. In our calculation, three kinds of atmospheric models (VAL-C, penumbra, umbra) have been used to make a proper calibration for an active region composed of quiet, penumbral and umbral areas. It was found that firstly, the results of our calculation depend highly on a kind of atmospheric model rather than on any other input parameters used in a model. Secondly, observed line profile showed m solar spectrum atlas proved to be very similar to the calculated profiles obtained by using a penumbra model. Finally, another method except this calibration curve should be developed to estimate correctly the distribution of magnetic field in solar active region from the observation of polarized spectral line.

• 한국군사과학기술학회지
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• 제6권3호
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• pp.15-21
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• 2003

This paper contains a precise calibration technique for the position of seabed acoustic target and theoretical error analysis of calibration results. The target is deployed on seabed as a standalone transponder. The purpose of target is performing accuracy test for active sonar as well as position calibration itself. For the position calibration, relative range between target and test vessel should be measured using target's transponder function. The relative range data combined with vessel position can be converted into a estimated position of target by the application of nonlinear LSE method. The error analysis of position calibration was divided into two stages. One is for relative range estimator and the other for target position estimator. Numerical simulations for position calibration showed good matching between results and developed CRLB.

• 로봇학회논문지
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• 제2권1호
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• pp.40-47
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• 2007

Recently, with the development of service robots and with the new concept of ubiquitous world, the position estimation of mobile objects has been raised to an important problem. As pre-liminary research results, some of the localization schemes are introduced, which provide the absolute location of the moving objects subjected to large errors. To implement a precise and convenient localization system, a new absolute position estimation method for a mobile robot in indoor environment is proposed in this paper. Design and implementation of the localization system comes from the usage of active beacon systems (based upon RFID technology). The active beacon system is composed of an RFID receiver and an ultra-sonic transmitter: 1. The RFID receiver gets the synchronization signal from the mobile robot and 2. The ultra-sonic transmitter sends out the traveling signal to be used for measuring the distance. Position of a mobile robot in a three dimensional space can be calculated basically from the distance information from three beacons and the absolute position information of the beacons themselves. Since it is not easy to install the beacons at a specific position precisely, there exists a large localization error and the installation time takes long. To overcome these problems, and provide a precise and convenient localization system, a new auto calibration algorithm is developed in this paper. Also the extended Kalman filter has been adopted for improving the localization accuracy during the mobile robot navigation. The localization accuracy improvement through the proposed auto calibration algorithm and the extended Kalman filter has been demonstrated by the real experiments.

• 한국정밀공학회지
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• 제21권5호
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• pp.83-83
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• 2004

The analysis of relative pose(position and rotation) between stereo cameras is very important to determine the solution that provides three-dimensional information for an arbitrary moving target with respect to robot-end. In the space of free camera-model, the rotational parameters act on non-linear factors acquiring a kinematical solution. In this paper the general solution of active stereo that gives a three-dimensional pose of moving object is presented. The focus is to achieve a derivation of linear equation between a robot′s end and active stereo cameras. The equation is consistently derived from the vector of quaternion space. The calibration of cameras is also derived in this space. Computer simulation and the results of error-sensitivity demonstrate the successful operation of the solution. The suggested solution can also be applied to the more complex real time tracking and quite general and are applicable in various stereo fields.