• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.615-616
• /
• 2008

Generally, distance between sensor nodes is measured using received signal strength indicator (RSSI) in wireless sensor network (WSN). Since RSSI is not absolutely accurate and stable in indoor environment, the performance of position estimation largely depends on estimation methods. In this paper, performance evaluation is presented to compare trilateration based positioning technique and collaborative ranging (CR) technique. From evaluation results, CR method is shown to be better than trilateration based method in terms of accuracy and precision.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.5
• /
• pp.566-572
• /
• 2014

Recently, indoor navigation has been applied in large convention centers by using wireless sensor networks (WSNs), which provide not only a user's path to be traveled but also orientation and shopping information to increase user's convenience. This paper presents the localization system for estimating relative coordinates without pre-deployment of the reference node based on ultra wide band (UWB) ranging system, which is relatively suitable for indoor localization compared to other wireless communications, and azimuth sensor. The proposed localization system which consists of an azimuth sensor and a mobile node composed of three nodes estimates relative coordinates of the reference node without applying any recursive and time consumption algorithms. Also, in the process of estimating relative coordinates of the reference node, ranging errors are minimized through the proposed technique and the number of nodes can be reduced. Experimental results show the feasibility and validity of the proposed system.

• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.4
• /
• pp.309-314
• /
• 2015

In this study, an embedded ranging system based on a laser structured light image is developed. The distance measurement by the structured light image processing has efficient computation because the burdensome correspondence problem is avoidable. In order to achieve robustness against environmental illumination noise and real-time laser structured light image processing, a bandpass optical filter is adopted in this study. The proposed ranging system has an embedded image processor performing the whole image processing and distance measurement, and so reduces the computational burden in the main control system. A system calibration algorithm is presented to compensate for the lens distortion.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.12
• /
• pp.122-130
• /
• 2010

This paper presents an active ranging system based on laser structured-light image. The structured-light image processing is computationally efficient in comparison with the conventional stereo image processing, since the burdensome correspondence problem is avoidable. In order to achieve robustness against environmental illumination noise, an efficient image processing algorithm, i.e., integration of difference images with structured-light modulation is proposed. Distance equation from the measured structured light pixel distance and system parameter calibration are addressed in this paper. Experiments and analysis are carried out to verify performance of the proposed ranging system.

• Journal of Engineering Education Research
• /
• v.13 no.5
• /
• pp.76-80
• /
• 2010

In this paper, the Location Compensation Mechanism using equivalent distance rate ($LCM_{edr}$) for localization system based on SDS-TWR (Symmetric Double-Sided Two-Way Ranging) in wireless sensor network is proposed. The performance of the mechanism is experimented in terms of two types of the localization tracking scenarios of indoor and outdoor environments in university campus. From the experimentations, the compensation ratio in the $LCM_{edr}$ is better than that in SDS-TWR about 90% in indoor/outdoor environments in scenario 1 but also is better than that of SDS-TWR about 91.7% in indoor environment and about 100% in outdoor environment in scenario 2 respectively.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.38 no.12
• /
• pp.971-982
• /
• 1989

An integrating position estimation algorithm has been developed for the navigation system of a free-ranging AGV system. The navigation system focused in this research work consists of redundant wheel encoders for the relative position measurement and a vision sensor for the absolute position measurement. A maximum likelihood method and an extended Kalman filter are implemented for enhancing the performance of the position estimator. The maximum likelihood estimator processes noisy, redundant wheel encoder measurements and yields efficient estimates for the AGV motion between each sampling interval. The extended Kalman filter fuses inharmonious positional data from the deadreckoner and the vision sensor and computes the optimal position estimate. The simulation results show that the proposed position estimator solves a generalized estimation problem for locating the vehicle accurately in space.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.327-328
• /
• 2007

This paper is to develop the path-tracking of free-ranging AGV(Autonomous Guided Vehicle). Encorders are used to trace the location of the AGV. A gyroscope is used to complement encorders that have the error accumulation problem by increasing the distance covered. A sensor fusion technique is applied to correct the error. The path of the AGV is controlled by kinematics and PID which is obtained the data from the sensor fusion. Experimental results are presented to verify the efficiency of proposed method.

• Korean Journal of Materials Research
• /
• v.12 no.2
• /
• pp.103-111
• /
• 2002

The thermally insulated underground pipelines have been used for district heating system. The sensor wire embedded in the insulation was used for monitoring the insulating resistance between the sensor wire and the pipe. The resistance measurement system detects corrosion of steel pipe under insulation. The corrosion and stress corrosion cracking(SCC) characteristics of sensor wire in synthetic ground water were investigated using the electrochemical methods and constant load SCC tests. The polarization tests were used to study the electrochemical behavior of sensor wire. The sensor wire was passivated at temperatures ranging from 25 to $95^{\circ}C$. However, the applied sensing current larger than passive current resulted in breakdown of passive film. The constant load SCC tests were performed to investigate the effects of applied current and load on the fracture behavior. Stress-corrosion cracks initiated at pits that were produced by sensing current. The growth of the pit involves a tunnelling mechanism, which leads to ductile fracture.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.4
• /
• pp.1248-1253
• /
• 2010

In this paper, the compensation algorithm for localization using the concept of equivalent distance rate(AEDR) in order to compensate ranging error in the SDS-TWR(Symmetric Double-Sided Two-Way Ranging) is proposed and the performance of the proposed algorithm is analyzed by the localization experiments. The ranging error of the SDS-TWR in the distance between mobile node and beacon node is measured to average 1m~8m by ranging experiments. But it is confirmed that the performance of the localization by the AEDR is better than that of the SDS-TWR 4 times in university auditorium and corridor, and the localization error of above 3~10m is reduced to average 2m and that of below 3m is reduced to average 1m respectively. It is concluded that the AEDR is superior to the NLOS(Non Line Of Sight) than LOS(Line Of Sight) in performance of ranging compensation for localization, and the AEDR is more helpful to localization systems practically considering the environment of sensor networks is under NLOS.

• Journal of Korea Society of Industrial Information Systems
• /
• v.18 no.6
• /
• pp.17-24
• /
• 2013

The localization accuracy in wireless sensor networks using ranging-based localization algorithms is greatly influenced by the ranging accuracy. Software implementation of HAL(Hardware Abstraction Layer) and MAC(Medium Access Layer) should seamlessly deliver the raw performance of ranging-based localization provided by hardware capability fully to the applications without degrading the raw performance. This paper presents the design and implementation of the software stack for IEEE 802.15.4a which supports normal ranging mode of the Nanotron's NA5TR1 RF chip. The experiment results shows that average ranging error rate with our implementation is 24.5% for the normal mode of the SDS-TWR ranging scheme.