• The Journal of Korea Robotics Society
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• v.8 no.1
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• pp.29-36
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• 2013

This paper presents a sensitivity optimization of a MEMS (microelectromechanical systems) gyroscope for a magnet-gyro system. The magnet-gyro system, which is a guidance system for a AGV (automatic or automated guided vehicle), uses a magnet positioning system and a yaw gyroscope. The magnet positioning system measures magnetism of a cylindrical magnet embedded on the floor, and AGV is guided by the motion direction angle calculated with the measured magnetism. If the magnet positioning system does not measure the magnetism, the AGV is guided by using angular velocity measured with the gyroscope. The gyroscope used for the magnet-gyro system is usually MEMS type. Because the MEMS gyroscope is made from the process technology in semiconductor device fabrication, it has small size, low-power and low price. However, the MEMS gyroscope has drift phenomenon caused by noise and calculation error. Precision ADC (analog to digital converter) and accurate sensitivity are needed to minimize the drift phenomenon. Therefore, this paper proposes the method of the sensitivity optimization of the MEMS gyroscope using DEAS (dynamic encoding algorithm for searches). For experiment, we used the AGV mounted with a laser navigation system which is able to measure accurate position of the AGV and compared result by the sensitivity value calculated by the proposed method with result by the sensitivity in specification of the MEMS gyroscope. In experimental results, we verified that the sensitivity value through the proposed method can calculate more accurate motion direction angle of the AGV.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.58-63
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• 2014

Most of light duty AGVs(AGCs) using tape of magnetic for the guide path have digital guidance magnetic sensor. Digital guidance magnetic sensor using magnet-tape is on/off type and has positioning error of magnet-tape as 10~50 mm. AGC using this sensor doesn't induce accurate position of magnet-line which is magnet-tape because of magnetic field which motor in AGC creates, outer magnetic field, earth's magnetic field, etc. AGC when driving wobbles due to this error and this error can cause path deviation. In this paper, we propose fuzzy inference system for improvement of bipolar analog magnetic guidance sensor performance. Fuzzy is suitable in term of fault tolerance, uncertainty tolerance, real-time operation, and Nonlinearity as compared with other algorithms. In previous research, we produced bipolar magnetic guidance sensor and we set the threshold in order to calculate digital values of magnet position. Fuzzy inference system is designed using outputs of Analog hall sensors. Magnet position calculated by digital method is improved by outputs of this system. In result, proposed method was verified by improving performance of magnetic guidance sensor.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.2
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• pp.140-144
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• 2003

A navigation sensor system for outdoor AGV(Automatic Guided Vehicle) using AMR(Anisotropic Magnetoresitive) sensors is described. We derive a formula of the position of AMR sensor using the measured magnetic field intensity due to permanent magnet with constant distance. The system consists of sensor board. sensor control board and position processing board. The sensor board measures magnetic field intensity, the sensor control board controls the measurement of six sensors sequentially, and the position processing board computes the accurate position of the permanent magnet using Least Square Method. We arranged six sensors at intervals of 30cm and measured the position of the permanent magnet moving at intervals of 30cm. Experimental results showed that we can get standard deviation of 2mm and error of &\pm&4.5mm at a height of 20cm from the permanent magnet.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.367-372
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• 2012

This paper presents a development of an analog type magnetic positioning system and its positioning accuracy improvement using fuzzy inference system. As the magnetic positioning system used on a magnet-gyro guidance system for AGV(automatic guided vehicle), it measures a position of magnet embedded in floor of the work place. The existing product of the magnetic positioning system is very expensive in Korea because it is being sold in a foreign country exclusively. Moreover, the positioning accuracy of the product is low because it uses digital type unipolar hall sensors. Hence, we developed the magnetic positioning system by ourselves and improved the positioning accuracy of the developed magnetic positioning system using fuzzy inference system. For experiment, we used the analog type magnetic positioning system which we have developed, and compared the performance of the proposed method with the performance of the existing positioning method for the magnetic positioning system. In experimental results, we verified that the proposed method improved the positioning accuracy of the magnetic positioning system.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1067-1074
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• 1994

This paper deals with the combined levitation and guidance EDS(Electrodynamic Suspension) Maglev system. Levitation and guidance forces generated in figured-of-eight coil are examined. End effect of Superconducting magnets is considered in that the air gap flux has been calculated using the finite number of magnets. Induced emfs and currents of ground coils are given as results. Eletromagnetic forces vary according to the built-in position of magnets. Levitation forces of the first magnet pair are the smellest and those of the second one are the largest. This result shows that the end effect of SCMs should be considered in a concentrated magnet system.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.11a
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• pp.12-16
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• 1991

The advantage of the controlled permanent magnet system for magnetic levitation is the considerable improvement in levitation force to weight ratio and the reduced rating of the on-board power supply. A combined support and guidance technique with selfstable guide behaviour reduce the expense of control and power electronics. An important feature of this system is the simplified mechanical construction of track and the vehicle does not embrace the guide way. Therefore surface mounted as well as elevated tracks are possible. The magnet was designed to provide a lift force of 750kg for a 3 ton prototype vehicle with 4 magnets by KERI and built by Dae-Bo Magnetic Co., LTD. The paper also describes the assembling technology for permanent magnets, the experimental setup and test results for lift force, guidance force and flux distribution.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.54-59
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• 2010

This paper present to study the guidance system as localization technique using sensor fusion and line tracking technique using virtual line for AGV(autonomous guided vehicle). An existing AGV could drive on decided line only. And representative guidance systems of such guidance system are magnet-gyro guidance and wired guidance. However, those have had the high cost of installation and maintenance, and the difficulty of system change according to variation of working environment. To solve such problems, we make the localization system which is fused with a laser navigation and gyro, encoder. The system is robust against noise, and flexible according to working environment through sensor fusion. For line tracking of laser navigation without wire guidance, we set the virtual line in program, and design the driving controller based on difference of angle and distance between AGV's position and decided virtual line. To experiment, we use the AGV which is made by ourselves, and experiment the line tracking repeatedly on same experimental environment. In result, maximum distance error between decided virtual line and AGV's position was less than 49.93mm, and we verified that the proposed system is efficient for line tracking of actual AGV.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.106-109
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• 1991

A magnet is designed and analysed using a finite element method program (FLUX2D), which will be employed to the 2-module MAGLEV test vehicle for developing of DAE JEON EXPO '93 Magnetic Levitation System. Levitation force. guidance force and thermal characteristics are examined according to the variation of parameters of the magnet ie. pole width, window area, rail configuration, input current and so on. An optimal geometry of the magnet are provided.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.18-23
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• 1992

Magnet core and rail of a magnetically levitated vehicle are usually made of highly conductive materials. Accordingly, eddy currents are induced in those members. Eddy currents often lead to a decrement of levitation and guidance force. This paper has calculated the decrement of both forces due to eddy current generated by magnet's vertical and lateral motion. U-shaped electromagnet and rail were chosen as amodel of 2D finite element analysis. Calculated results proved that both forces dropped significantly at high speed. Consequently, effects of eddy current should be considered in designing the magnet and control system.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.142-145
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• 1989

The electromagnetic suspension system, which is a kind of magnetic levitation, can be categorized into two groups; separate lift & guidance system and combined lift & guidance system. This paper deals with the latter system, in which lift and guidance forces are generated by a pair of staggered magnets with the inverted U- shaped rail. In this work, a rigid body bogie-truck and a twist response type of bogie-truck, which are constructed by two magnetic wheels consist of two staggered magnet pairs, are modeled, and curvature running characteristics of both types obtained by simulation are presented. Simulation result showed that curvature running characteristics of twist response type of bogie-truck is better than that of rigid body bogie-truck.