• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.387-393
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• 2021

This paper proposes a system to synchronize the time of computers over an unmanned aerial vehicle (UAV) network. With the proposed system, the UAVs can perform missions that require precise relative time. Also, data collected by UAVs can be fused precisely with synchronized time. In the system, to synchronize the time of all computers over the UAV network, two-step synchronization is performed. In the first step, the mission computers of the UAVs are synchronized through the server of the system. After the first step, the mission computers measure time offset between the time of the mission computers and the flight computers. The offset values are delivered to the server. In the second step, virtual time is determined by the server from the collected time offset. The measured offset is compensated by moving the synchronized time of mission computers to the reasonable virtual time. Since only the time of mission computers are controlled, any flight computers that use micro air vehicle link (MAVLink) protocol can be synchronized in the proposed system.

• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.11-16
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• 2020

In this paper, system that includes multiple unmanned aerial vehicles (UAVs) are considered. The vehicles are equipped with a mission computer for a specific mission and equipment. The mission equipment operates based on the time of mission computer. Also, data collected by flight computer and mission computer is saved with the time of each operating system. Generally, time offset between multiple computers always exists, though the computers are connected to the Internet. When the data collected by multiple computers is combined, the time offset causes damage on reliability of the combined data. Computers that connected to the Internet are synchronized by network time protocol (NTP). This paper proposes a system that the time of multiple mission computers are synchronized by the same NTP server to minimize the time offset. In the results of the measurement, the system time offset of multiple mission computer is maintained within 10ms from the system time of the server computer.

• Journal of Korean Institute of Industrial Engineers
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• v.3 no.2
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• pp.73-81
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• 1977

Mission effectiveness, which is the probability of successfully completing the assigned mission, is introduced as an appropriate measure of effectiveness for a military system. The model of mission effectiveness is developed for a system which is required to carry out various types of a mission. Each mission type is characterized by the maximum allowable time that determines the success of a given mission type. A given type of a mission is successful if and only if (i) the system is available at the start of a mission and (ii) the system completes its mission within the maximum allowable duration of time that this given mission type specifies without any failure during this period. Both analytic and simulation approaches are employed. Difficulties involved in the anayticl approach are discussed. The model is proposed as a useful tool for consistent system evaluation and optimum test design.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.1-7
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• 2014

In this paper, it is suggested a method of mission planning and management for robots based on the unit mission. In order to make robots execute given missions continuously as time goes by, a new concept for planning the mission which is composed of one or more unit missions and an automatic mission management scheme are developed. For managing robot's missions in real time, six management methods are devised as well in order to cope with the mismatches, which occur frequently during the mission execution, as to the initial plan. Without the operator's involvement, any mismatch can be adjusted automatically by applying one of the mission management methods. The suggested concept of mission planning and mission management methods based on the unit mission are partially realized in the Dog-Horse robot system and it is checked that it can be a viable one for developing effective robot operation systems.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.2
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• pp.54-60
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• 2018

This paper contains the multi-mission scheduling optimization of UAV within a given operating time. Mission scheduling optimization problem is one of combinatorial optimization, and it has been shown to be NP-hard(non-deterministic polynomial-time hardness). In this problem, as the size of the problem increases, the computation time increases dramatically. So, we applied the genetic algorithm to this problem. For the application, we set the mission scenario, objective function, and constraints, and then, performed simulation with MATLAB. After 1000 case simulation, we evaluate the optimality and computing time in comparison with global optimum from MILP(Mixed Integer Linear Programming).

• Journal of the Korean Data and Information Science Society
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• v.17 no.3
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• pp.861-869
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• 2006

Burn-in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, the problem of determining optimal burn-in time for a system which performs given mission is considered. It is assumed that the given mission time is not a fixed constant but a random variable which follows an exponential distribution. Assuming that the underlying lifetime distribution of a system has an eventually increasing failure rate function, an upper bound for the optimal burn-in time which maximizes the probability of performing given mission is derived. The obtained result is also applied to an illustrative example.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.2
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• pp.180-187
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• 2010

In this paper, a global path generation method is suggested using multiple grid maps connected with the mission type of unmanned combat vehicle(UCV). In order to carry out a mission for UCV, it is essential to find a global path which is coincident with the characteristics of the mission. This can be done by considering various combat circumstances represented as grid maps such as velocity map, threat map and communication map. Cost functions of multiple grid maps are linearly combined and normalized to them simultaneously for the path generation. The proposed method is realized using $A^*$, a well known search algorithm, and cost functions are normalized in the ratio of the traverse time which is one of critical information should be provided with the operators using the velocity map. By the experiments, it is checked found global paths match with the mission type by reflecting input data of grid maps properly and the computation time is short enough to regenerate paths in real time as combat circumstances change.

• Journal of the military operations research society of Korea
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• v.22 no.1
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• pp.97-113
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• 1996

Mission effectiveness may be defined as a probability that a system can successfully meet an intended mission demand within a given time when operated under specified conditions. This study deals with the Mission effectiveness of a replenishment ships that is performing several types of missions. The essential attributes and their related factors affecting the replenishment missions are established, and then, a mathematical mission effectiveness model is constructed with a replenishment mission characteristics for a basis. Mission effectiveness for a mission is determined by finding the joint probability measure of the following three attributes : operational readiness of the replenishment ships at the start of a mission ; mission reliability of the replenishment ships ; capability of successfully accomplishing intended objectives given an environmental condition. The model is solved analytically. Operational readiness of the replenishment ships in found by the assumed data. Mission reliability and capability are calculated based on the assumed probability distributions. The model would be a useful tool to evaluate mission effectiveness as it is very a replenishment ships.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.575-584
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• 2021

This study contains the process of developing a Mission Planning System (MPS) of an USV that can be applied in real situations and verifying them through HILS. In this study, we set the scenario of a single USV with limited operating time. Since the USV may not perform some missions due to the limited operating time, an objective function was defined to maximize the Mission Achievement Rate (MAR). We used a genetic algorithm to solve the problem model, and proposed a method using a 3-D population. The simulation showed that the probability of deriving the global optimal solution of the mission planning algorithm was 96.6% and the computation time was 1.6 s. Furthermore, USV showed it performs the mission according to the results of the MPS. We expect that the MPS developed in this study can be applied to the real environment where USV performs missions with limited time conditions.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.1
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• pp.71-78
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• 1993

A Baysian approach is proposed is estimating the mission failure rates by criticalities. A mission failure which occurs according to a Poisson process with unknown rate is assumed to be classified as one of the criticality levels with an unknown probability. We employ the Gamma prior for the mission failure rate and the Dirichlet prior for the criticality probabilities. Posterior distributions of the mission rates by criticalities and predictive distributions of the time to failure are derived.