• 대한간호학회지
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• 제49권3호
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• pp.274-285
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• 2019

Purpose: This study aimed to examine the effects of a mobile navigation program on uncertainty, resilience, and growth through uncertainty in colorectal cancer patients. Methods: To verify the effectiveness of the mobile navigation program, 61 participants diagnosed with colorectal cancer undergoing surgery were selected. A nonequivalent control group nonsynchronized design was used to evaluate the program. Uncertainty was measured using the Korean version of the Uncertainty in Illness Scale, resilience was measured using the Korean version of the Connor-Davidson Resilience Scale, and growth through uncertainty was measured using the Growth through Uncertainty Scale. Results: Compared with the control group, patients in the mobile navigation program group showed significant differences in scores for uncertainty (F=7.22, p=.009) and resilience (F=4.31, p=.042), but not for growth through uncertainty (F=2.76, p=.102). Conclusion: These results suggest that the mobile navigation program has positive effects on decreasing uncertainty and increasing resilience among colorectal cancer patients. The mobile navigation program could play a significant role in assisting colorectal cancer patients in regard to the continuity and usability of the program.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.51-58
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• 2023

Geofencing supports unmanned aerial vehicle (UAV) operation by defining stay-in and stay-out regions. National Aeronautics and Space Administration (NASA) has developed a prototype of the geofencing function, SAFEGUARD, which prevents stayout region violation by utilizing position estimates. Thus, SAFEGUARD depends on navigation system performance, and the safety risk associated with the navigation system uncertainty should be considered. This study presents a methodology to compute the safety risk assessment-based along-track position error bound under nominal and Global Navigation Satellite Systems (GNSS) failure conditions. A Kalman filter system using pseudorange measurements as well as pseudorange rate measurements is considered for determining the position uncertainty induced by velocity uncertainty. The worst case pseudorange and pseudorange rate fault-based position error bound under the GNSS failure condition are derived by applying a Receiver Autonomous Integrity Monitor (RAIM). Position error bound simulations are also conducted for different GNSS fault hypotheses and constellation conditions with a GNSS/INS integrated navigation system. The results show that the proposed along-track position error bounds depend on satellite geometries caused by UAV attitude change and are reduced to about 40% of those of the single constellation case when using the dual constellation.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권2호
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• pp.81-86
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• 2005

In this paper we consider an optimal configuration problem for redundant inertial sensors which have uncertainty such as misalignment, scale factor error. The optimal configuration problem is treated from the viewpoint of navigation accuracy. We propose a necessary and sufficient condition for the optimal configuration of redundant sensors with no uncertainty, and a sufficient condition for the optimal configuration of redundant sensors with uncertainty. Finally we propose a condition for the optimal configuration based both navigation performance and FDI(fault detection and isolation).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.26-26
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• 2000

We study on the velocity matching algorithm for transfer alignment of inertial navigation system(INS) using robust H$_2$ filter. We suggest an uncertainty model for INS and apply the suggested discrete robust H$_2$ filter to the uncertainty model compared with kalman filter, the discrete robust H$_2$ filter is shown by simulation to have good performance of alignment time and accuracy.

• 로봇학회논문지
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• 제4권3호
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• pp.169-176
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• 2009

Low-cost sensors have been widely used for mobile robot navigation in recent years. However, navigation performance based on low-cost sensors is not good enough to be practically used. Among many navigation techniques, building of an accurate map is a fundamental task for service robots, and mapping with low-cost IR sensors was investigated in this research. The robot's orientation uncertainty was considered for mapping by modifying the Bayesian update formula. Then, the data association scheme was investigated to improve the quality of a built map when the robot's pose uncertainty was large. Six low-cost IR sensors mounted on the robot could not give rich data enough to align the range data by the scan matching method, so a new sample-based method was proposed for data association. The real experiments indicated that the mapping method proposed in this research was able to generate a useful map for navigation.

• 한국항해항만학회지
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• 제43권6호
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• pp.462-468
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• 2019

해양석유 생산은 예기치 못한 유가 하락과 글로벌 석유물류의 변화로 인한 여러 가지 어려움에 직면하고 있다. 이 연구는 불확실성하의 해양석유생산 최적화를 위한 추계적 모형을 제시한다. 제시된 추계적 모형은 강인한 최적화 모형과 리코스 제한 최적화 모형을 사용하고 리코스 이익 변동의 척도로 하위부분평균을 사용한다. 제안된 모형을 바탕으로 불확실성 하의 원유의 가격과 수요에 관한 시나리오 기반의 자료를 사용하여 수행한 계산실험 및 결과를 검토하여 보고하였다. 이 연구는 불학실성 하에서 위험을 고려한 해양석유생산 문제에 대한 의사결정에 유의하게 적용될 수 있을 것이다.

• 한국항행학회논문지
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• 제23권6호
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• pp.577-583
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• 2019

음이 아닌 입력에 대하여 음이 아닌 초기상태에서 출발한 모든 상태변수 값들이 시간에 대하여 항상 음이 아닌 값을 유지하는 시스템은 양의 시스템으로 정의된다. 본 논문에서는 상태변수에 시변 지연시간과 비구조화된 불확실성이 함께 존재하는 양의 시변 선형 이산 구간 시스템의 안정조건을 새롭게 제안한다. 시변 지연시간은 변동가능한 최소와 최대 지연시간 범위 내에서 변하는 것으로 고려되며, 불확실성은 비선형성을 포함하여 그 최대 크기만을 알 수 있는 것으로 고려한다. 제안된 안정조건은 이전의 결과들이 시불변시스템에만 적용되었거나 불확실성에 대한 고려가 없었던 것을 개선한 것으로 매우 간단한 부등식의 형태로 표현된다. 안정조건은 리아프노프 안정이론을 이용하여 유도되며, 리아프노프 방정식의 상한 해 한계(upper solution bound)를 이용한 기존 결과에 비하여 많은 장점을 갖는다. 제안된 안정조건은 기존의 결과들을 포함하는 효과적인 것으로 수치예제를 통하여 이를 검증한다.

• 한국항행학회논문지
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• 제22권6호
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• pp.630-635
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• 2018

본 논문에서는 시변 지연이 있는 선형 이산 시스템에 비구조화된 불확실성이 존재하는 경우에 대하여 시스템의 안정성을 다룬다. 고려된 시스템은 지연 없는 상태변수와 지연 상태 변수에 대한 시스템 행렬들은 시불변이나 지연시간이 구간범위에서 시변으로 변동하고, 크기에 대한 정보만을 얻을 수 있는 비구조화된 비선형 불확실성이 있는 시스템이다. 기존의 많은 결과들은 시변지연과 비구조화된 불확실성을 동시에 고려하지 못하고 한 가지 요소만 고려하여 연구되었다. 본 논문에서는 이 두 가지 요소를 모두 고려하여 새로운 안정조건을 도출하였고, 한 가지 요소만 고려한 기존 연구 결과와 비교하였다. 새로운 안정조건은 기존의 결과를 포함하는 매우 효과적인 수식으로 제안되며, 이는 복잡한 선형행렬부등식 혹은 리아프노프 방정식 등과 같은 복잡한 수치계산을 요구하지 않는 간단한 부등식이다. 수치예제를 통하여 제안된 안정조건이 기존의 결과들을 포함할 수 있음을 보이고 확장성과 효용성이 우수함을 확인한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1450-1455
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• 2005

This paper describes a DR construction for land navigation and the sigma point based receding horizon Kalman FIR (SPRHKF) filter for DR/GPS hybrid navigation system. A simple DR construction is adopted to improve the performance both of the pure land DR navigation and the DR/GSP hybrid navigation system. In order to overcome the flaws of the EKF, the SPKF is merged with the receding horizon strategy. This filter has several advantages over the EKF, the SPKF, and the RHKF filter. The advantages include the robustness to the system model uncertainty, the initial estimation error, temporary unknown bias, and etc. The computational burden is reduced. Especially, the proposed filter works well even in the case of exiting the unmodeled random walk of the inertial sensors, which can be occurred in the MEMS inertial sensors by temperature variation. Therefore, the SPRHKF filter can provide the navigation information with good quality in the DR/GPS hybrid navigation system for land navigation seamlessly.

• Ocean Systems Engineering
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• 제6권2호
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• pp.191-201
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• 2016

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.