• 한국CDE학회논문집
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• 제14권1호
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• pp.18-24
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• 2009

This paper proposes an analytical method of evaluating the maximum error by modeling the exact tool path for the tool traverse singular region in five-axis machining. It is known that the NC data from the inverse kinematics transformation of 5-axis machining can generate singular positions where incoherent movements of the rotary axes can appear. These lead to unexpected errors and abrupt operations, resulting in scoring on the machined surface. To resolve this problem, previous methods have calculated several tool positions during a singular operation, using inverse kinematics equations to predict tool trajectory and approximate the maximum error. This type of numerical approach, configuring the tool trajectory, requires much computation time to obtain a sufficient number of tool positions in a region. We have derived an analytical equation for the tool trajectory in a singular area by modeling the tool operation into a linear and a nonlinear part that is a general form of the tool trajectory in the singular area and that is suitable for all types of five-axis machine tools. In addition, we have evaluated the maximum tool-path error exactly, using our analytical model. Our algorithm can be used to modify NC data, making the operation smoother and bringing any errors to within tolerance.

• Journal of Astronomy and Space Sciences
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• 제40권4호
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• pp.217-224
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• 2023

The Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, successfully entered its mission orbit on December 27, 2022 (UTC), and is currently performing its mission smoothly. To mitigate potential contingencies during the flight and to navigate the spacecraft into the desired lunar orbit, the KPLO flight dynamics (FD) team analyzed major trajectory-related contingencies that could lead to the violation of mission requirements and prepared operational procedures from the perspective of trajectory and FD. This paper presents the process of preparing contingency trajectory operations for the KPLO, including the identification of trajectory contingencies, prioritization results, and the development of recovery plans and operational procedures. The prepared plans were successfully applied to address minor contingencies encountered during actual operations. The results of this study will provide valuable insights to FD engineers preparing for space exploration mission operations.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.411-413
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• 2009

본 논문은 초음속 추진을 이용한 미사일 시스템에 대한 궤적최적화에 대한 연구를 소개한다. 초음속 추진 시스템은 외부비행조건과 내부 연소 환경에 따른 복잡하고 비선형성이 강한 추력특성을 가진다. 이러한 이유로 초음속 비행체의 운용에 있어 많은 구속조건을 가지며 일반 비행체보다 좁은 비행영역안에서 운용되어야 한다. 본 논문에서는 이러한 특성을 가지는 초음속 비행체의 궤적최적화를 수행하고 보다 효율적인 운용에 대한 비전을 제시하고자 한다. 궤적최적화는 일반적인 초음속 추진에 관련한 구속조건들을 고려하며 수행되었고, 궤적최적화 결과를 통해 얻어진 효율적 연료공급 및 노즐 목 면적 제어에 대한 일반적인 운용 및 응용방안에 대해서 고찰하고자 한다.

• 한국항행학회논문지
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• 제22권5호
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• pp.367-374
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• 2018

차세대 통신링크를 활용한 항공로 교통 관리를 위해 궤적 기반의 관제 지원 스케줄링 시스템을 제안하였다. 차세대 ATS (air traffic services) 데이터링크인 Baseline 2를 사용하는 4DTRAD (4-dimensional trajectory data link) 서비스 내용을 기반으로 항공로 상을 비행 중인 항공기를 대상으로 하는 궤적기반운용 수행 절차를 수립하고 기술하였다. 이러한 절차를 바탕으로, 다양하고 복잡한 데이터 활용으로 인한 관제사의 업무 부담을 완화하기 위해 지상 시스템이 수신한 항공기 데이터를 처리하여 궤적을 예측하고 관제 조언 정보를 제공하는 스케줄링 시스템의 프로토타입을 개발하였다. 또한, 궤적 기반 항행을 위한 시뮬레이션 환경을 구성하여 개발 시스템에 대한 스케줄링 기능을 확인하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.147-148
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• 2022

최근 선박 접안 시 사고가 다수 발생함에 따라, 항만 내 선박운항에 대한 안전조치에 대한 필요성이 강조되고 있다. 본 연구는 부산신항만 내 안전조치에 대한 내용을 정량적으로 분석하고자 선박 항적 데이터를 수집하고, 이를 바탕으로 해사인공지능 알고리즘을 적용여 항적패턴을 분석하였다. 그 결과, 부산신항 입출항선박의 변침 지점을 도출하고, 선속·침로의 운용패턴을 제안하였다.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5128-5134
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• 2011

본 논문에서는 HEV용 영구자석 매립형 동기전동기의 단위전류 당 최대토크 운전을 위한 dq 전류 궤적에 대하여 고찰하였다. 전동기 상수로부터의 단위전류 당 최대토크 운전을 위한 dq 전류를 해석하고, 이를 바탕으로 영구자석의 자속 및 dq 인덕턴스 등의 전동기 상수가 변할 경우 단위전류 당 최대토크 운전점의 변화를 고찰하였다. 또한 단위전류 당 최대토크 제어를 위한 dq 전류의 궤적을 실험을 통하여 검증하였다.

• 수산해양기술연구
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• 제57권4호
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• pp.334-341
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• 2021

The fishery compensation by marine spatial planning such as routeing of ships and offshore wind farms is required objective data on whether fishing vessels are engaged in a target area. There has still been no research that calculated the number of fishing operation days scientifically. This study proposes a novel method for calculating the number of fishing operation days using the fishing trajectory data when investigating fishery compensation in marine spatial planning areas. It was calculated by multiplying the average reporting interval of trajectory data, the number of collected data, the status weighting factor, and the weighting factor for fishery compensation according to the location of each fishing vessel. In particular, the number of fishing operation days for the compensation of driftnet fishery was considered the daily average number of large vessels from the port and the fishery loss hours for avoiding collisions with them. The target area for applying the proposed method is the routeing area of ships of Jeju outer port. The yearly average fishing operation days were calculated from three years of data from 2017 to 2019. As a result of the study, the yearly average fishing operation days for the compensation of each fishing village fraternity varied from 0.0 to 39.0 days. The proposed method can be used for fishery compensation as an objective indicator in various marine spatial planning areas.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.742-748
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• 2004

In this paper are presented TSTO system analysis including some controlled variables on the engine operation such as a fuel flow rate and a pressure ratio of compressor, as well as variables on the trajectory. TSTO studied here is accelerated up to Mach 6 by a fly-back booster powered by air breathing engines. Three different types of engine cycle were treated for propulsion system of the booster, such as a turbo ramjet, a precooled turbojet and an EXpander cycle Air Turbo Ramjet (ATREX). The history of the controlled variables on the engine operation was optimized by Sequential Quadratic Programming (SQP) to accomplish the minimum fuel consumption. The trajectory was also optimized simultaneously. The results showed that the turbo ramjet gave the best fuel consumption. The optimal trajectory was almost the same except in the transonic range and just before reaching to Mach 6. The history of the pressure ratio of compressor considerably depended on the engine type. It is concluded that simultaneous optimization for engine control and trajectory is effective especially for a high-speed airplane propelled by turbojets like the TSTO booster.

• 한국군사과학기술학회지
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• 제20권6호
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• pp.774-780
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• 2017

The techniques for driving trajectory calculation and driving trajectory distribution calculation are proposed to analyze the durability of ground vehicles effectively. To achieve this aim, the driving trajectory of a vehicle and the driving trajectory distribution of that are needed, in addition to road profile. The road profiles can be measured by a profilometer but a driving trajectory of a vehicle cannot be acquired effectively due to a large position error from a conventional GPS sensor. Therefore two techniques are proposed to reduce the position error of a vehicle and achieve the distribution of driving trajectory of that. The driving trajectory calculation technique produces relative positions by using the velocity, time and heading of a vehicle. The driving trajectory distribution calculation technique produces distributions of the driving trajectory by using axis transformation, estimating reference line, dividing sectors and plotting a histogram of the sectors. As a results of this study, we can achieve the considerably accurate driving trajectory and driving trajectory distribution of a vehicle.

• International Journal of Aeronautical and Space Sciences
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• 제10권1호
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• pp.112-121
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• 2009

This paper deals with supersonic air-breathing missile system. A supersonic air-breathing missile system has very complicated and incoherent thrust characteristics with respect to outer and inner environment during operation. For this reason, the missile system has many maneuver constraints and is allowed to operate within narrow flight envelope. In this paper, trajectory optimization of the missile is accomplished. The trajectory optimization problem is formulated as a discrete parameter optimization problem. For this formulation, Legendre Pseudo-Spectral method is introduced. This method is based on calculating the state and control variables on Legendre-Gauss-Lobatto (LGL) points. This approach helps to find approximated derivative and integration quantities simply. It is shown that, for this trajectory optimization, trend analysis is performed from thrust characteristics on various conditions so that the trajectory optimization is accomplished with fine initial guess with these results.