• Journal of Institute of Control, Robotics and Systems
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• v.20 no.7
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• pp.767-773
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• 2014

The carrier-to-noise power ratio is a key parameter for determining the reliability of PVT (Position, Velocity, and Time) solutions which are obtained by a GNSS (Global Navigation Satellite System) receiver. It is also used for locking a tracking loop, deciding the re-acquisition process, and processing advanced navigation in the receiver subsystem. The representative carrier-to-noise power ratio estimation schemes are the narrowband-wideband power ratio method (NW), the MM (Moment Method), and Beaulieu's method (BL). The NW scheme is the most classical one for commercial GNSS receivers. It is often used as an authoritative benchmark for assessing carrier-to-noise power estimation schemes. The MM scheme is the least biased solution among them, and the BL scheme is a simpler scheme than the MM scheme. This paper focuses on the less biased estimation with low complexity when the residual phase noise remains, then proposes a novel carrier-to-noise power ratio estimation scheme with low complexity for GNSS receivers. The asymptotic bias of the proposed scheme is derived and compared with others, and the simulation results demonstrate that the complexity of the proposed scheme is lowest among them, while the estimation performance of the proposed scheme is similar to those of the BL and MM schemes in normal and high gained reception environments.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.933-942
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• 2009

In this paper, the WAVE technology for IT based on Intelligent Transport System(ITS) which using by IEEE 802.11a PHY, IEEE 802.11p MAC(Medium Access Control) and IEEE P1609.3 was implemented. The WAVE system was designed that has maximum 0.5km communication range for RSU(Road Side Equipment) between vehicle, 12Mbps transfer speed when downlink at maximum 120km/h vehicle speed. To verify suitableness of the WAVE system for ITS, we measured several parameters on the real road: communication range when low and high speed, link establishment time, data transfer speed, PER (Percent Error Rate), and latency. From the experiment results, we demonstrated that WAVE is a suitable technology for IT based on ITS.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.62-63
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• 2009

A monitoring system of collision risk among multiple ships is newly-designed in order to reduce human error and make vessel traffic control more effective. By using AIS data as ships' navigational information, an estimation algorithm of collision risk among multiple ships is newly-designed. To consider ships' course of now and future, collision risks of multiple ships can be calculated by using fuzzy algorithm. To test the performance of new algorithm, replay simulations are carried out on actual AIS data collected from VTS center of Ulsan harbor in Korea. The AIS data include 25 ships' information for two hours. In this paper, the features of newly-designed estimation algorithm of collision risk and the results of replay simulation are discussed.

• ETRI Journal
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• v.42 no.1
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• pp.26-35
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• 2020

Herein, we consider uplink multiuser massive multiple-input multiple-output systems when multiple users transmit information symbols to a base station (BS) by applying simple space-time block coding (STBC). At the BS receiver, two detection filters for each user are used to detect the STBC information symbols. One of these filters is for odd-indexed symbols and the other for even-indexed symbols. Using constrained output variance metric minimization, we first derive a special relation between the closed-form optimal solutions for the two detection filters. Then, using the derived special relation, we propose a new blind adaptive algorithm for implementing the minimum output variance-based optimal filters. In the proposed adaptive algorithm, filter weight vectors are updated only in the region satisfying the special relation. Through a theoretical analysis of the convergence speed and a computer simulation, we demonstrate that the proposed scheme exhibits faster convergence speed and lower steady-state bit error rate than the conventional scheme.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1771-1776
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• 2003

In mobile robot navigation, one of the key problems is the pose estimation of the mobile robot. Although the odometry can be used to describe the motions of the mobile robots quite simple and accurately, the validities of the models are limited by a number of error sources contaminating the encoder outputs so that applying the conventional extended Kalman filter to these nominal model does not yield the satisfactory performance. As a remedy for this problem, we consider the uncertain nonlinear kinematic model of the mobile robot that contains the norm bounded uncertainties and also propose a new robust extended Kalman filter based on the Krein space approach. The proposed robust filter has the same recursive structure as the conventional extended Kalman filter and can hence be readily designed to effectively account for the uncertainties. The computer simulations will be given to verify the robustness against the parameter variation as well as the reliable performance of the proposed robust filter.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.314-317
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• 1993

In this paper, the IPE(Iterative Parameter Estimation) methods for the nonlinear measurements are proposed. The IPE methods convert the problems of the parameter estimation for the nonlinear measurements to that of the solution of the nonlinear equations approximately and use several iterative numerical solutions, such as fixed points theory, Newton's methods, quasi-Newton's methods and steepest descent techniques. the IPE methods for the nonlinear measurements-in the case of the error estimation for the inertial navigation systems are simulated, and it is found that the estimation errors for the nonlinear measurements decrease rapidly and converge to almost that of the linear LSE(Least Squares Estimation) when the IPE methods are applied.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.930-937
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• 1994

Straodown intertial navigation system(SDINS) is a navigational instrument necessary to guide and control a free vehicle. Dynamically Tuned Gyroscope(DTG) which is widely applied to SDINS convers a wide dynamic range and is simple and small. In study, the analysis of mechanical parts or sensor parts and research of balancing is performed for manufacturing a DTG. In error analysis the criterion considered during designing and manufacturing is established by quantitatively anayzing the effect of DTG performance by tolerance. And the theory of dynamic balancing is derived and unbalance is reduced through experiment. And the stiffness of flexure is verified by tuning experiment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5219-5226
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• 2014

This paper proposes an improved scheme of pedestrian position information system using neural network theory in a GPS-disabled area. Through a learning/obtaining gait pattern and step distance about walk, run, duck walk, crab walk and crawl, the position estimation error could be minimized by rejecting the inertial navigation drift. A portable hardware module was implemented to evaluate the performance of the proposed system. The performance and effectiveness of the suggested algorithm was verified by experiments indoors.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2503-2506
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• 2002

본 논문에서는 청소로봇의 주행에 관해 연구되어지고 있는 이론적인 제어알고리즘이 갖는 주행오차저감방법에 관해 연구하였다. 청소로봇의 양 바퀴의 속도에 따라 그려지는 이상적인 회전반경과 실제 실험을 통해 그려지는 회전반경은 다르다. 이는 청소로봇이 주행 시 나타나는 오차가 원인이다. 많은 이론적인 제어알고리즘이 청소로봇의 주행에 잘 적용되기 위해 주행 시 나타나는 오차를 수정하거나 보상해야 한다. 본 연구에서는 이상적인 회전반경과 실험을 통해 얻은 회전반경의 비교를 통해 오차와 회전반경을 구하고 이를 주행에 적용하고자 한다.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.117-120
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• 2000

본 논문은 이동로봇이 주행 중 발생하는 heading 오차를 지자기센서를 이용하여 보정하고 주행을 정확히 제어하는 것에 관한 것이다. 일반적으로 이동로봇의 주행제어는 여러 원인에 의한 부정확성을 내포하고 있다. 예를 들어 바퀴의 부정확한 기계적 정렬, 기어의 헐거워짐, 센서 신호의 잡음과 오차, 바퀴의 미끄러짐, 평탄하지 않는 표면에 의한 제도변동 등이다. 따라서, 이동명령어 수행 시 이동로봇의 heading이 의도된 대로 유지되는지를 측정하는 오차 검출이 필요하며 이를 위한 센서 본 논문에서는 지자기센서를 이용하여 오차를 보정하였다. 실험은 무선 원격 제어되는 이동로봇에 지자기 센서를 부착하여 자계의 영향이 비교적 적은 평탄한 옥외에서 수행하였고, 실험 결과를 통해 지자기 센서를 이용한 이동로봇의 heading 오차 보정과 주행제어효과를 보여주었다.