• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.11
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• pp.2945-2965
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• 2023

The laser inertial measurement unit is a precision device widely used in rocket navigation system and other equipment, and its quality is directly related to navigation accuracy. In the quality evaluation of laser inertial measurement unit, there is inevitably uncertainty in the index input information. First, the input numerical information is in interval form. Second, the index input grade and the quality evaluation result grade are given according to different national standards. So, it is a key step to transform the interval information input by the index into the data form consistent with the evaluation result grade. In the case of uncertain input, this paper puts forward a method based on probability distribution to solve the problem of asymmetry between the reference grade given by the index and the evaluation result grade when evaluating the quality of laser inertial measurement unit. By mapping the numerical relationship between the designated reference level and the evaluation reference level of the index information under different distributions, the index evidence symmetrical with the evaluation reference level is given. After the uncertain input information is transformed into evidence of interval degree distribution by this method, the information fusion of interval degree distribution evidence is carried out by interval evidential reasoning algorithm, and the evaluation result is obtained by projection covariance matrix adaptive evolution strategy optimization. Taking a five-meter redundant laser inertial measurement unit as an example, the applicability and effectiveness of this method are verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.453-460
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• 2014

We analyze fault detection algorithm of ephemeris included in navigation message, which is one of the GNSS risk factors. This algorithm uses carrier-phase measurement and baseline vector of two reference stations and is alternative method for uncertainty condition of previous ephemeris. Even though same ephemeris fault is occurred, the geometry condition, between baseline vector of reference stations and satellites, effects on performance of algorithm. Also, we introduce the suitable geometry of reference stations, threshold and performance index (MDE : Minimum Detectable Error) in jeju international airport.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.93-100
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• 2006

In this paper, a new-type Extended Kalman Filter (EKF) is proposed as a robust nonlinear filter for a stochastic nonlinear system. The original EKF is widely used for various nonlinear system applications. But it is fragile to its estimation errors because they give rise to linearization errors that affect the system mode1 as the modeling errors. The linearization errors are nonlinear functions of the estimation errors therefore it is very difficult to obtain the accurate error covariance of the EKF using the linear form. The inaccurately estimated error covariance hinders the EKF from being a sub-optimal estimator. The proposed filter tries to obtain the upper bound of the error covariance tolerating the uncertainty of the error covariance instead of trying to obtain the accurate one. It treats the linearization errors as uncertain modeling errors that can be handled by the robust linear filtering. In order to be more robust to the estimation errors than the original EKF, the proposed filter minimizes the upper bound like the robust linear filter that is applied to the linear model with uncertainty. The in-flight alignment problem of the inertial navigation system with GPS position measurements is a good example that the proposed robust filter is applicable to. The simulation results show the efficiency of the proposed filter in the robustness to initial estimation errors of the filter.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.903-909
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• 2007

Mobile Robots are increasingly being used to perform tasks in unknown environment. The potential of robots to undertake such tasks lies in their ability to intelligently and efficiently search in an environment. To achieve autonomous mobile robot navigation, efficient path planner and accurate localization technique are the fundamental issues that should be addressed. This paper presents mobile robot localization using IRID(InfraRed IDentification) as artificial landmarks. IRID has highly deterministic characteristics, different from RFID. By putting several IRID emitters on the ceiling, the floor is divided into many different sectors and each sector is set to have a unique identification. Dead-reckoning provides the estimated robot configuration but the error becomes accumulated as the robot travels. IRID information tells the sector the robot is in, but the size of the uncertainty is too large if only the IRID information is used. This paper presents an algorithm which combines both the encoder and the IRID information so that the size of the uncertainty becomes smaller. It also introduces a framework which can be used with other types of the artificial landmarks. The characteristics of the developed IRID and the proposed algorithm are verified from the simulation results and experiments.

• Journal of Korean Port Research
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• v.11 no.2
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• pp.191-202
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• 1997

As the suitability of berth allocation will ultimately have a significant influence on the performance of a berth, a great deal of attention should be given to berth allocation. Generally, a berth allocation problem has conflicting factors between servers and users. In addition, there is uncertainty in great extent caused by various factors such as departure delay, inclement weather on route, poor handling equipment, a lack of storage space, and other factors contribute to the uncertainty of arrival and berthing time. Thus, it is necessary to establish berth allocation planning which reflects the positions of interested parties and the ambiguity of parameters. For this, a berth allocation problem is formulated by fuzzy 0-1 integer programming introducing the concept of maximum Position Shift(MPS). But, the above approach has limitations in terms of computational time and computer memory when the size of problem is increased. It also has limitations with respect to the integration of other sub-systems such as ship planning system and yard planning system. For solving such problem, this paper focuses particularly on developing an efficient heuristic algorithm as a new technique of getting an effective solution. And also the suggested algorithm is verified through the illustrative examples and empirical appalicaton to BCTOC.

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.191-201
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• 2023

The provision of onboard Internet services is recognized as one of the measures to enhance the appeal of seafarers and improve seafarer welfare. This study aims to investigate the influence of seafarers' leisure activities using the Internet on shipboard culture. Shipboard culture was examined using Hofstede's cultural dimensions theory. An empirical analysis was conducted on crewmembers regarding their Internet-based leisure activities and the shipboard culture. As a result, it was observed that sociability activities through the Internet while onboard significantly influenced power distance, uncertainty avoidance, and long-term orientation. The investigation of shipboard culture revealed uncertainty avoidance, masculinity, and long-term orientation, along with low power distance and individualism cultures. In addition, an analysis of shipboard culture according to seafarers' characteristics showed significant differences in certain shipboard cultures based on seafarers' attributes.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.913-924
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• 2011

This study purpose to find out how the relationship characteristics between travel agencies and airlines affect the conflict. As a result of analysis, competition, specialty, uncertainty of environment, frequency of contact and cooperation from the airline's answers have an effect on conflict while variability of environment, similarity, frequency of contact and specialty from the travel agency's answers are affected. In terms of relationship characteristics and conflict between airlines and travel agencies, competition, similarity, frequency of contact and difference of perception and communication difficulty are affected. The relationship characteristics from the result of this study makes a contribution in reducing conflict and improving positive relationship between airlines and travel agencies.

• Journal of Navigation and Port Research
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• v.34 no.7
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• pp.587-594
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• 2010

The positive and negative opinion to cargo demand of Incheon's SAMT in the near future remains cloudy. Considering port and shipping environmental changes and the logistics situation of China which explains the lack of facilities in Chinese airports, the creating of SAMT cargoes of the Incheon region could catches a favorable opportunity to be a logistics hub in the North-East Asia. On the other hand, as open-sky policy and direct-call service has been carried out between China and N.A.(North America), Incheon could cause a loss of competitiveness in SAMT because the enhancement in the aspect of the connectivity of Chinese airlines and shipping lines makes customer sent to last destination their cargoes whenever they want. In the same context, this paper analyses on conditions of domestic and international SAMT and proposes in this uncertainty future forecasting of SAMT of Incheon by scenario planning according to changes in integrated SAMT, measuring the likelihood of final scenario. This study shows the Sea & Air multi-transport volume will have either slight increase or decrease from the current condition. Consequently, RFS expansion and system & service improvement through strong ties with major cities in China will be required in a short run aspect. Nonetheless, we also need to take domestic & international transportation environment into account in the long run.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2017.11a
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• pp.124-127
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• 2017

선박에서 배출되는 환경오염 물질 및 온실가스에 대한 규제가 강화됨에 따라, 환경오염 물질 및 온실가스의 배출과 직접적으로 관련있는 연료 소모량을 줄이려는 다양한 연구가 진행되고 있다. 연료 소모량을 줄이기 위한 방안 중 하나는 환경 및 기상 예보를 이용하여 연료가 가장 적게 소모되는 항로를 찾는 것이다. 기존 연구에서는 연료 소모량을 주된 목적함수로 최소화 하되, 도착 시간에 대한 조건을 평가하기 위해 도착 시간의 기댓값을 계산하고 추가적인 목적함수로 고려하는 경우가 많았다. 그러나 선박 운항 예측 시 적용되는 환경 외란 정보는 상당한 불확실성을 포함하고, 이로 인해 발생하는 운항 속도 및 도착 시간에 대한 불확실성도 상당히 클 수 있기 때문에, 도착 시간의 기댓값뿐만 아니라 도착 시간에 대한 불확실성을 기반으로 제한 시간 내에 선박이 도착할 확률을 정량적으로 평가하는 것이 필요하다. 본 연구에서는 다목적 최적화 기법을 이용해 도착 시간의 기댓값과 연료 소모량에 대한 Pareto set을 구하되, 환경 외란으로부터 발생하는 도착 시간의 불확실성을 계산하여, 제한 시간 내에 선박이 도착할 확률을 계산하고 이를 항로 최적화 시 적용한다. 제안하는 방법의 유용성을 검증하기 위해 실제 환경에 가까운 맵을 기반으로 부산-도쿄 간의 항로를 최적화하고, 그 결과에 대해 논의한다.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.468-473
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• 2014

This paper describes the in-flight alignment of SDINS (Strapdown Inertial Navigation Systems) using an EKF (Extended Kalman Filter) and a UKF (Unscented Kalam Filter), which allow large initial attitude error uncertainty. Regardless of the inertial sensors, there are nonlinear error dynamics of SDINS in cases of large initial attitude errors. A UKF that is one of the nonlinear filtering approaches for IFA (In-Flight Alignment) are used to estimate the attitude errors. Even though the EKF linearized model makes velocity errors when predicting incorrectly in case of large attitude errors, a UKF can represent correctly the velocity errors variations of attitude errors with nonlinear attitude error components. Simulation results and analyses show that a UKF works well to handle large initial attitude errors of SDINS and the alignment error attitude estimation performance are quite improved.