• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.9-17
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• 2001

GPS is an efficient system in surveying and car navigation. but it is difficult to catch minimum number of satellite when it is hindered by obstacle such as city area. GLONASS system doesn't have perfect constellation yet, but it has many similarities with GPS system in principle of point positioning and signal system. so, it is expected to be much efficient when it is used with GPS system. For the purpose of this, the coordinates of GPS and GLONASS system, the quality of time and frequency was investigated, and the algorithm of point positioning was made. also, the efficiency of GPS/GLONASS combination was presented by analysing the precision of 3D point positioning using C/A code and Yuma satellite orbit information.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.315-318
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• 1996

In this paper a new positioning method for cylindrical work pieces on rotating supports is studied. A work piece on a rotating axis is positioned by an impact drive mechanism (IDM) whose driving parameters are steadily updated by observing the object movement. The application of this actuator and the use of a multi-functional PC board for all necessary input and output operations such as e.g. data acquisition or wave form generation allow an alignment with a precision of less than 1.mu.m in a relatively short time and at low cost compared to conventional methods.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.3
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• pp.478-490
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• 2007

A technology of ultrasonic biotelemetry for tracking fish behavior is investigated. The ultrasonic biotelemetry system is constituted by a transmitter and a receiving system. Because a pinger was mainly used for the transmitter, the capability for pinger to possess was investigated and the efficient usage for pinger was examined. A source pressure level and a frequency were synthetically examined so that pinger could realize small size, a light weight, and a long life time. The receiving system is divided roughly into directional hydrophone systems and acoustic positioning systems by the receiving method. The directional hydrophone system is divided into single beam and multiple beam with the number of hydrophone, and the acoustic positioning systems is divided into LBL (Long Base Line), SBL (Short Base Line), and SSBL (Super Short Base Line) on the basis of base line. The present situation, the merits and demerits, and the principle of each receiving method were investigated in detail, and the efficient usage for each receiving method were examined.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.10
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• pp.996-1001
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• 2006

This paper proposes an ultrasonic location system based on the spread spectrum principle. Though there are several conventional ultrasonic systems, the proposed system is the first one that combines spread spectrum and amplitude modulation principles. The proposed ultrasonic location system is advantageous in that it can improve positioning accuracy and detection sensitivity by the spread spectrum principle, it simplifies transmitter and receiver circuits, and it is easy to upgrade its performance by modifying only the software functionalities. By several real data experiments, the advantage and performance of the proposed location system is demonstrated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.63-66
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• 2006

This paper proposes an ultrasonic location system based on the spread spectrum principle. Compared with the existing ultrasonic location systems, the proposed system combines the spread spectrum and amplitude modulation principles. As a result, the proposed ultrasonic location system is advantageous in that it can improve positioning accuracy and detection sensitivity by the spread spectrum principle, it simplifies transmitter and receiver circuits by the amplitude modulation, and it is easy to upgrade its performance by the software functionalities. The advantages and performance of the proposed location system are demonstrated by experiments.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.83-88
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• 2006

Many applications in the area of location-based services and personal navigation require nowadays the location determination of a user not only in outdoor environment but also indoor. To locate a person or object in a building, systems that use either infrared, ultrasonic or radio signals, and visible light for optical tracking have been developed. The use of WiFi for location determination has the advantage that no transmitters or receivers have to be installed in the building like in the case of infrared and ultrasonic based location systems. WiFi positioning technology adopts IEEE802.11x standard, by observing the radio signals from access points installed inside a building. These access points can be found nowadays in our daily environment, e.g. in many office buildings, public spaces and in urban areas. The principle of operation of location determination using WiFi signals is based on the measurement of the signal strengths to the surrounding available access points at a mobile terminal (e.g. PDA, notebook PC). An estimate of the location of the terminal is then obtained on the basis of these measurements and a signal propagation model inside the building. The signal propagation model can be obtained using simulations or with prior calibration measurements at known locations in an offline phase. The most common location determination approach is based on signal propagation patterns, namely WiFi fingerprinting. In this paper the underlying technology is briefly reviewed followed by an investigation of two WiFi positioning systems. Testing of the system is performed in two localization test beds, one at the Vienna University of Technology and the second at the Hong Kong Polytechnic University. First test showed that the trajectory of a moving user could be obtained with a standard deviation of about ${\pm}$ 3 m.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.70-74
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• 2007

This paper describes the development of a nano-positioning system for nanoscale science and engineering. Conventional positioning systems, which can be expensive and complicated, require the use of laser interferometers or capacitive transducers to measure nanoscale displacements of the stage. In this study, a new self-displacement sensing (SDS) nano-stage was developed using mechanical magnification of its displacement signal. The SDS nano-stage measured the displacement of its movement using a position-sensitive photodiode (PSPD), a laser source, and a hinge-connected rotating mirror plate. A beam from a laser diode was focused onto the middle of the plate with the rotating mirror. The position variation of the reflected beam from the mirror rotation was then monitored by the PSPD. Finally, the PSPD measured the amplified displacement as opposed to the actual movement of the stage via an optical lever mechanism, providing the ability to more precisely control the nanoscale stage. The displacement amplification process was modeled by structural analysis. The simulation results of the amplification ratio showed that the distance variation between the PSPD and the mirror plate as well as the length L of the mirror plate could be used as the basic design parameters for a SDS nano-stage. The PSPD was originally designed for a total travel range of 30 to 60 mm, and the SDS nano-stage amplified that range by a factor of 15 to 25. Based on these results, a SDS nano-stage was fabricated using principle of displacement amplification.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.127-132
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• 2006

The Global Positioning System (GPS), Inertial Navigation System (INS) and Pseudolite (PL) technologies all play very important roles in navigation systems. As an independent navigation system, GPS can provide high precision positioning results which are independent of time. However, the performance will become unreliable when the system experiences high dynamics, or when the receiver is exposed to jamming or RF interference. In comparison to GPS, though INS is autonomous and provides good short-term accuracy, its use as a standalone navigation system is limited due to the time-dependent growth of the inertial sensor errors. PLs are ground-based transmitters that can transmit GPS-like signals. They have some advantages in that their positions can be determined precisely, and the Signal-to-Noise Ratios (SNR) are relatively high. Because their combined performance, in principle, overcomes the shortcomings of the individual systems, the integration of GPS, INS and PL is increasingly receiving attention from researchers. Depending on the desired performance vs complexity, system integration can be carried out at different levels, namely loose, tight and ultra-tight coupling. Compared with loose and tight integration, although it is more complex in terms of system design, ultra-tight integration will be the basis of the next generation of reliable and robust navigation systems. Its main advantages include improved performance under exposure to high dynamics, and jamming and RF interference mitigation. This paper presents an overview of the ultra-tight integration developments and discusses some of the challenging issues.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.371-375
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• 2001

The concept of a new linear motor that uses piezo-stack actuator is demonstrated. The working principle is far different from the conventional inchworm motor. This motor is based on the self-moving cell concept. The linear motor has three cells and each cell is constructed with one piezo-stack actuator and a shell structure. A cell train is constructed by connecting these cells and the cell train is fitted into a guide way with a proper interference. The cell train moves along the guide way, by activating each cell in succession. The moving motion of the motor is tested. Since this linear motor uses piezo-stack actuator with unified clamping cell, it can produce fast speed, high resolution and large push force.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.708-717
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• 2003

With the development of precision manufacturing technologies, the importance of precision positioning devices is increasing. Conventional actuators, dual stage or mechanically contacting type, have limitation in coping with performance demands. As a possible solution, magnetic suspension technology was studied. Such a contact-free system has advantages in terms of high accuracy, low production cost and easy adaptability to high precision manufacturing processes. This paper deals with magnetically suspended multi-degrees of freedom actuator which can realize large linear motion. In this paper, the operating principle is explained with the magnetic force analysis, and the equations of motion are derived. Experimental results of the implemented system are also given.