• Journal of the Korean Society for Precision Engineering
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• v.30 no.2
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• pp.177-184
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• 2013

This paper proposes an enhanced Simultaneous Localization and Mapping (SLAM) algorithm based on matching laser image and Extended Kalman Filter (EKF). In general, laser information is one of the most efficient data for localization of mobile robots and is more accurate than encoder data. For localization of a mobile robot, moving distance information of a robot is often obtained by encoders and distance information from the robot to landmarks is estimated by various sensors. Though encoder has high resolution, it is difficult to estimate current position of a robot precisely because of encoder error caused by slip and backlash of wheels. In this paper, the position and angle of the robot are estimated by comparing laser images obtained from laser scanner with high accuracy. In addition, Speeded Up Robust Features (SURF) is used for extracting feature points at previous laser image and current laser image by comparing feature points. As a result, the moving distance and heading angle are obtained based on information of available points. The experimental results using the proposed laser slam algorithm show effectiveness for the SLAM of robot.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.134-141
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• 2014

Mobile robots use various sensors for navigation such as wheel encoder, vision sensor, sonar, and laser sensors. Dead reckoning is used with wheel encoder, resulting in the accumulation of positioning errors. For that reason wheel encoder can not be used alone. Too much information of vision sensors leads to an increase in the number of features and complexity of perception scheme. Also Sonar sensor is not suitable for positioning because of its poor accuracy. On the other hand, laser sensor provides accurate distance information relatively. In this paper we propose to extract the angular information from the distance information of laser range finder and use the Kalman filter that match the heading and distance of the laser range finder and those of wheel encoder. For laser scanner with one feature point error may increase much when the feature point is variant or jumping to a new feature point. To solve the problem, we propose to use two feature points and show that the positioning error can be reduced much.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.103-104
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• 2006

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1936-1938
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• 2002

A tunable fiber laser and the Quadrature Sampling technique are used to construct highly sensitive fiber-optic distributive Bragg grating strain sensor system. By using a wavelength-modulated fiber laser, the variations of strain-dependent Bragg wavelengths are transformed into the variations of time-domain reflection profiles. The locations of profile peaks that correspond to the applied strains are demodulated using a precise wavelength encoder that uses a fiber-optic Mach-Zehnder interferometer and Quadrature Sampling technique. With the extremely high sensitive optical encoder, we could obtain not only high sensitivity, but also very linear responses that was impossible with the conventional techniques. This paper is attempted to report the theoretical and experimental results.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.130-135
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• 1999

The main scale of linear encoder greatly effects on the precision of displacement measurement. Especially when needing the long range measurement the length of main scale should be increased accordingly. In this paper we propose a linear encoder that uses laser interference pattern as main scale for long range measurement. The linear encoder is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase difference of 0. $\pi$/4, $\pi$/2, 3$\pi$/4 are arranged on the panel. The experimental results show that signals of quadratic photo diode A, B, {{{{ {-}atop {A } }}}} and {{{{ {- } atop {B } }}}} are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1179-1184
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• 2003

The technique for measuring the rotational speed of tappet in direct acting type valve train system has been developed. The optic signal monitoring system with laser and optic fiber was designed to follow the signal of tappet rotation. The system was based on ON/OFF signal generation from the additional encoder teeth under the tappet with optic fibers attached photo transistor. The data showed that tappet rotation was affected by offset, oil temperature and cam shaft operating speed. Also it was found that tappet rotation increases with oil temperature. Tappet spin was delayed 10∼s20$^{\circ}$ cam angle after valve opening. The instantaneous rotational speed of tappet was reciprocal to cam shaft speed and the tappet and the cam angle ratio was located in the range of 0.1∼0.3.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.145-148
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• 2000

Position-determining capacity is a very important condition in equipments for manufacturing semi-conductor or various instruments to measure physical displacement quantities of a moving object in submicron such as a distance of movement, direction, etc. and the accuracy of total system is influenced by detecting accuracy of these equipments. Therefore in this paper we have optically made up laser linear encoder based on optical diffraction principle to measure these displacement quantities and have processed optical signal using hardware-setup. In consequence we had acquired displacement for movement of scale using a diffraction grating by the accuracy of 0.5${\mu}{\textrm}{m}$ and had digitalized moving quantities of scale.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.19-25
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• 1995

Presently, along with the advance of high-technology, the precise measurement of linear displacement has become a staple requirement, and consequently the high resolution with submicron order has also been required in precise positioning and carriaging. In this paper, we advance a propose on a new type of laser encoder based on the principle of phase analysis of the moire fringes from superimposed two gratings. The phase angle as an information of displacement can be accurately calculated by detecting the change in brighness at four points of the fringes. The actual application of four point method to the moire fringes is performed thru microcomputer for general purpose, and the measuring procedure is also studied in this research. As an experimental result, in the case of using 20 .mu. m-pitch gratings, it is validated that this method has the resolution of 0.01 .mu. m and the accuracy of .+-. 0.15 .mu. m over the setting range of 100mm.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.320-321
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• 2005

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.117-124
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• 2004

Recently, nano-methodology is increasingly important as the ruler for measuring nano-technology, and we applied the linear encoder to nano-methodology. The quadrature output in the linear encoder has an effect on increasing the resolution in some techniques. Already, various interpolation techniques based on the quadrature signal have applied to the precision servo system. In this paper, we propose a new interpolation algorithm for ultra-precision positioning in the low speed with simulation by MATLAB SIMULINK. This method modified previous methods and was properly designed for some given control system. To verify, we first fulfilled the encoder signal test to find main parameters fer the signal transformation, then we proved the proposed interpolation algorithm by experiments, which show that the result of the interpolation algorithm corresponds with the measurement of the laser interferometer in 100 nm unit approximately. In addition, we can get more precise measurement by more accurate and noise-free signal. So we need to compensate imperfections in the encoder signal. After that, we will apply this algorithm to nano positioning system.