Han-Lim Choi

Prof. Han-Lim Choi

Department of Aerospace Engineering & KI for Robotics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
orcid

Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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7 February 2018 in IEEE Transactions on Aerospace and Electronic Systems
Verified
Journal Article
Open access
MTMin-Jea Tahk
Min-Jea Tahk
SSSang-Wook Shim
Sang-Wook Shim
SHSeong-Min Hong
Seong-Min Hong
HCHan-Lim Choi
Han-Lim Choi
CLChang-Hun Lee
Chang-Hun Lee
This paper proposes a novel approach for guidance law design to satisfy the impact-time constraints for a certain class of homing missiles. The proposed guidance law provides proper lateral acceleration commands that make the impact time error converge to zero by the time of impact. This scheme can be applied to any existing guidance law for which a formula of predicted time to go is available. Convergence of time-to-go errors is supported by Lyapunov stability. The optimal guidance law (OGL) and the impact angle control guidance (IACG) law are extended by the proposed method for impact-timecontrol guidance (ITCG) and impact-time-and-angle-control guidance (ITACG), respectively. The performance of the extended guidance laws is demonstrated by numerical simulation

8 June 2012 in IEEE Journal on Selected Areas in Communications
Verified
Journal Article
Closed access
SPSameera S. Ponda
Sameera S. Ponda
LJLuke B. Johnson
Luke B. Johnson
AKAndrew N. Kopeikin
Andrew N. Kopeikin
HCHan-Lim Choi
Han-Lim Choi
JHJonathan P. How
Jonathan P. How
This paper presents a cooperative distributed planning algorithm that ensures network connectivity for a team of heterogeneous agents operating in dynamic and communication-limited environments. The algorithm, named CBBA with Relays, builds on the Consensus-Based Bundle Algorithm (CBBA), a distributed task allocation framework developed previously by the authors and their colleagues. Information available through existing consensus phases of CBBA is leveraged to predict the network topology and to propose relay tasks to repair connectivity violations. The algorithm ensures network connectivity during task execution while preserving the distributed and polynomial-time guarantees of CBBA. By employing under-utilized agents as communication relays, CBBA with Relays improves the range of the team without limiting the scope of the active agents, thus improving mission performance. The algorithm is validated through simulation trials and through experimental indoor and outdoor field tests, demonstrating the real-time applicability of the approach.

23 August 2019 in International Journal of Aeronautical and Space Sciences
Verified
Journal Article
Closed access
PDF file
KKKeum-Seong Kim
Keum-Seong Kim
HKHo-Yeon Kim
Ho-Yeon Kim
HCHan-Lim Choi
Han-Lim Choi

13 December 2019 in Applied Sciences
Verified
Journal Article
Open access
PDF file
HAHyojung Ahn
Hyojung Ahn
HCHan-Lim Choi
Han-Lim Choi
MKMinguk Kang
Minguk Kang
SMSungTae Moon
SungTae Moon
This paper addresses anomaly detection and monitoring for swarm drone flights. While the current practice of swarm flight typically relies on the operator’s naked eyes to monitor health of the multiple vehicles, this work proposes a machine learning-based framework to enable detection of abnormal behavior of a large number of flying drones on the fly. The method works in two steps: a sequence of two unsupervised learning procedures reduces the dimensionality of the real flight test data and labels them as normal and abnormal cases; then, a deep neural network classifier with one-dimensional convolution layers followed by fully connected multi-layer perceptron extracts the associated features and distinguishes the anomaly from normal conditions. The proposed anomaly detection scheme is validated on the real flight test data, highlighting its capability of online implementation.

2 April 2020 in Sensors
Verified
Journal Article
Open access
PDF file
HAHyojung Ahn
Hyojung Ahn
DJDawoon Jung
Dawoon Jung
HCHan-Lim Choi
Han-Lim Choi
A spacecraft attitude control system provides mechanical and electrical control to achieve the required functions under various mission scenarios. Although generally designed to be highly reliable, mission failure can occur if anomalies occur and the attitude control system fails to properly orient and stabilize the spacecraft. Because accessing spacecraft to directly repair such problems is usually infeasible, developing a continuous condition monitoring model is necessary to detect anomalies and respond accordingly. In this study, a method for detecting anomalies and characterizing failures for spacecraft attitude control systems is proposed. Herein, features are extracted from multidimensional time-series data of a simulation of the attitude control system. Then, the artificial neural network learning algorithms based on two types of generation models are applied. A Bayesian optimization algorithm with a Gaussian process is used to optimize the hyperparameters for the neural network to improve the performance. The performance is evaluated based on the reconstruction error through the algorithm using the newly generated data not used for learning as input data. Results show that the detection performance depends on the operating characteristics of each submode in the operation scenarios and type of generation model. The diagnostic results are monitored to detect anomalies in operation modes and scenarios.

4 July 2019 in International Journal of Control, Automation, and Systems
Verified
Journal Article
Closed access
PDF file
SKSang-Hyeon Kim
Sang-Hyeon Kim
HCHan-Lim Choi
Han-Lim Choi