Browsing by Author "Lee, Seokwon"
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Item Open Access Analysis of guidance laws with non-monotonic line-of-sight rate convergence(IEEE, 2021-09-20) Lee, Seokwon; Cho, Namhoon; Shin, Hyo-SangThis study presents analyses of guidance laws that involve non-monotonic convergence in heading error from a new perspective based on an advanced stability concept. Pure proportional navigation with range-varying navigation gain is considered, and the gain condition to guarantee asymptotic convergence to the collision course is investigated while allowing the heading error to exhibit patterns that involve intermediate diversion. The extended stability criterion considered in this study allows local increase of the function in some finite intervals, which is less conservative than the standard stability theorem. The existing guidance laws involving intentional modulation of the heading error as well as the design of the navigation gain are discussed with respect to the new stability criterion.Item Open Access Analysis of rendezvous guidance laws for autonomous aerial refueling for non-maneuvering and identical speed targets(Elsevier, 2022-01-14) Lee, Seokwon; Kim, MinguThis study analyzes rendezvous guidance schemes for UAVs refueling. Assuming the target is non-maneuvering with identical speed, a necessary condition is investigated for the UAV to approach the rendezvous point. Three types of guidance laws are considered to analyze the performance under the condition. A reachable region is analytically obtained using the closed-form solution of the deviated pursuit and pure proportional navigation. Numerical simulation demonstrates the analyzed result for the rendezvous mission.Item Open Access Analytic approach to impact time guidance with look angle constraint using exact time-to-go solution(American Society of Civil Engineers, 2023-12-12) Lee, Seokwon; Kim, Jinrae; Kim, Youdan; Cho, NamhoonThis paper proposes an analytic approach for impact time control guidance laws against stationary targets using biased proportional navigation. The proposed guidance scheme realizes the impact time control in two different ways: the first approach directly uses the exact time-to-go error to satisfy both the impact time control and the field-of-view constraint, while the second approach adopts a look angle tracking law to indirectly control the impact time, with the reference profile of the look angle generated using the exact time-to-go solution. The stability properties of the proposed guidance laws are discussed, and numerical simulations are carried out to evaluate their performance in terms of accuracy and efficiency.Item Open Access Impact analysis of time synchronization error in airborne target tracking using a heterogeneous sensor network(MDPI, 2024-04-23) Lee, Seokwon; Yuan, Zongjian; Petrunin, Ivan; Shin, HyosangThis paper investigates the influence of time synchronization on sensor fusion and target tracking. As a benchmark, we design a target tracking system based on track-to-track fusion architecture. Heterogeneous sensors detect targets and transmit measurements through a communication network, while local tracking and track fusion are performed in the fusion center to integrate measurements from these sensors into a fused track. The time synchronization error is mathematically modeled, and local time is biased from the reference clock during the holdover phase. The influence of the time synchronization error on target tracking system components such as local association, filtering, and track fusion is discussed. The results demonstrate that an increase in the time synchronization error leads to deteriorating association and filtering performance. In addition, the results of the simulation study validate the impact of the time synchronization error on the sensor network.Item Open Access Intent-informed state estimation for tracking guided targets(Elsevier, 2023-11-16) Lee, Seokwon; Shin, Hyo-Sang; Tsourdos, AntoniosThis paper proposes a state estimation and prediction for tracking guided targets using intent information. A conditionally Markov process is used to describe the destination-oriented target motion, and the collision intent is incorporated through the zero-effort-miss guidance information. The expected arrival time necessary for the conditionally Markov model is determined through the collision geometry and destination motion. Finally, the Kalman filter technique is used to estimate and predict the target state. Numerical simulations demonstrate that the proposed approach can improve state estimation accuracy in both static and dynamic destination cases.Item Open Access Inverse optimality of pure proportional navigation guidance for stationary targets(American Institute of Aeronautics and Astronautics, 2021-07-21) Lee, Seokwon; Cho, NamhoonThe main contribution of this study is the optimality analysis of the PPNG performed in full generality. The new theoretical findings can explain the result of the former analysis in which the PPNG is derived as the minimum effort solution [5] and also describe a comprehensive design framework including the observability-enhanced guidance laws developed for the dual homing guidance problem. Furthermore, this study provides several examples illustrating how the PPNG with various navigation gain functions can be understood as optimal control solutions.Item Open Access Look-angle-constrained control of arrival time with exact knowledge of time-to-go(AIAA, 2021-05-26) Cho, Namhoon; Lee, SeokwonThe capability to control the time of arrival at a goal position as desired endows a single vehicle or a coalition of many of them with the strategic advantage to perform time-critical missions. Arrival time coordination can be used as an element to solve multi-agent, multidepot routing and task planning problems in cooperative unmanned aerial robots. The tactic known as Salvo, which either designates or synchronizes the impact times across multiple missiles to enhance their collective survivability as well as attack effectiveness, strongly depends on control of arrival time. In principle, control of arrival time is essentially adjustment of the arc length of the vehicle’s flight path through manipulation of the curvature, provided that most vehicles flying in the atmosphere often prefer not to change their speeds excessively. On the other hand, the capability to take measurements of the target with onboard sensors provides a higher degree of autonomy to the vehicle and hence allows a more intelligent behavior. Modern autonomous vehicles acquire information about the designated destination or the surrounding environment with imaging sensors, in particular. An onboard sensor that collects emission or reflection from the target is usually not likely to be omni-directional yet possesses only a finite field-of-regard. The requirement to ensure continuous acquisition of target-originated signals necessitates a measure to keep the information source inside the sensor’s field of view that spans over a solid angle of limited range. That is, a box constraint is imposed on the look angle.Item Open Access Three-dimensional biased proportional navigation guidance based on spatial rotation of predicted final velocity(IEEE, 2022-08-17) Cho, Namhoon; Lee, Seokwon; Shin, Hyo-Sang; Kim, Tae-HunThis study presents the design of three-dimensional biased proportional navigation guidance laws for arrival at a stationary target along a desired direction based on spatial rotation of predicted final velocity vector. The focus is on full constructive derivation using vector-form expressions without introducing local representation of rotation such as Euler angles or quaternions. The proposed approach synthesises the bias command in the form of an angular velocity vector through realisation of the predictive control design philosophy, the direction which has been unexplored in a three-dimensional setting. The proposed approach avoids heuristic choices and approximations in the design process and hence overcomes the limitation of earlier studies. The vector-form design approach provides theoretical and practical advantages including rigour in derivation, clear geometric understandings about the problem provided by identification of the most effective direction for rotation of final velocity, independence from selection of a fixed coordinate system, avoidance of singularities in local representations, more direct trajectory shaping, and simple implementation.