CERES :: Browsing by Author "Lee, Chang-Hun"

Browsing by Author "Lee, Chang-Hun"

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Open Access
Anomaly detection of aircraft engine in FDR (flight data recorder) data
(Institution of Engineering and Technology (IET), 2018-05-21) Lee, Chang-Hun; Shin, Hyosang; Tsourdos, Antonios; Skaf, Zakwan
This paper deals with detection of anomalous behaviour of aircraft engines in FDR (flight data recorder) data to improve airline maintenance operations. To this end, each FDR data that records different flight patterns is first sampled at a fixed time interval starting at the take-off phase, in order to map each FDR data into comparable data space. Next, the parameters related to the aircraft engine are only selected from the sampled FDR data. In this analysis, the feature points are chosen as the mean value of each parameter within the sampling interval. For each FDR data, the feature vector is then formed by arranging all feature points. The proposed method compares the feature vectors of all FDR data and detects an FDR data in which the abnormal behaviour of the aircraft engine is recorded. The clustering algorithm called DBSCAN (density-based spatial clustering of applications with noise) is applied for this purpose. In this paper, the proposed method is tested using realistic FDR data provided by NASA's open database. The results indicate that the proposed method can be used to automatically identify an FDR data in which the abnormal behaviour of the aircraft engine is recorded from a large amount of FDR data. Accordingly, it can be utilized for a high-level diagnosis of engine failure in airline maintenance operations.
Open Access
Collision-geometry-based optimal guidance for high-speed target
(Elsevier, 2021-04-30) Kim, Boseok; Kim, Young-Won; Cho, Namhoon; Lee, Chang-Hun
This paper proposes a new unified form of guidance law based on the collision geometry that can be applied to both head-on (HO) or head-pursuit (HP) engagements for intercepting a target faster than an interceptor. To this end, two possible collision courses for a high-speed target and corresponding nonlinear heading errors are first investigated. The proposed guidance is then determined in a way to specify the desired heading error dynamics that ensures an optimal decreasing pattern. The characteristics of the proposed method are also investigated compared to existing methods. The favorable features are that the engagement geometries between HO or HP can be flexibly selected, and the optimality of the guidance command can be addressed. Moreover, since the proposed guidance law is directly derived from nonlinear collision geometry, the working mechanism is clearly explained, and the nonlinear nature is preserved. Finally, numerical simulations are performed to support our findings.
Open Access
Cooperative control for multiple interceptors to maximize collateral damage
(Elsevier, 2019-08-29) Lee, Chang-Hun; Tsourdos, Antonios
In this paper, a cooperative control method to satisfy the relative interception angle constraints in multi-to-one engagement case is proposed. In this study, we consider the relative interception angle constraints of the multiple interceptors, which is intended to enhance the survivability of the multiple interceptors against a defense system of high value target as well as to maximize the collateral target damage. The proposed cooperation control can reduce the total control energy required while satisfying the given interception angle constraints. This characteristic allows to increase the change of mission in the multi-to-on engagement scenario. In this paper, the numerical simulations are conducted to verify the feasibility of proposed concept.
Open Access
Data analytics development of FDR (Flight Data Recorder) data for airline maintenance operations
(IEEE, 2017-12-11) Lee, Chang-Hun; Shin, Hyosang; Tsourdos, Antonios; Skaf, Zakwan
In this article, we propose a data analytics development to detect unusual patterns of flights from a vast amounts of FDR (flight data recorder) data for supporting airline maintenance operations. A fundamental rationale behind this development is that if there are potential issues on mechanical parts of an aircraft during a flight, evidences for these issues are most likely included in the FDR data. Therefore, the data analysis of FDR data enables us to detect the potential issues in the aircraft before they occur. To this end, in a data pre-processing step, a data filtering, a data sampling, and a data transformation are sequentially performed. And then, in this analysis, all time series data in the FDR are classified into three types: a continuous signal, a discrete signal, and a warning signal. For each type of signal, a high-dimensional vector by arranging the time series data is chosen as features. In the feature section process, a correlation analysis, a correlation relaxation, and a dimension reduction are sequentially conducted. Finally, a type of k-nearest neighbor approach is applied to automatically identify the FDR data in which the unusual flight patterns are recorded from a large amount of FDR data. The proposed method is tested with using a realistic FDR data from the NASA's open database.
Open Access
Energy-optimal waypoint-following guidance considering autopilot dynamics
(IEEE, 2019-11-28) He, Shaoming; Shin, Hyosang; Tsourdos, Antonios; Lee, Chang-Hun
This paper addresses the problem of energy-optimal waypoint-following guidance for an Unmanned Aerial Vehicle with the consideration of a general autopilot dynamics model. The proposed guidance law is derived as a solution of a linear quadratic optimal control problem in conjunction with a linearized kinematics model. The algorithm developed integrates path planning and following into a single step and is able to be applied to a general waypoint-following mission. Theoretical analysis reveals that previously suggested optimal point-to-point guidance laws are special cases of the proposed approach. Nonlinear numerical simulations clearly demonstrate the effectiveness of the proposed formulations.
Open Access
Generalized time-to-go inversion guidance with impact time and angle constraints
(AIAA, 2025-03) Wang, Pengyu; Lee, Chang-Hun; Cho, Namhoon; Wie, Bong
A major challenge in homing guidance is that accurately predicting the time to go for missiles is generally difficult, which limits the practical application of a certain class of guidance laws with impact-time constraints or cooperative capabilities. To address this issue, a generalized method referred to as the time-to-go inversion guidance is presented, where the time to go is first specified as an explicit function and then the corresponding guidance law is inversely derived. By employing this new method, a variety of guidance laws and their globally accurate time-to-go solutions can be developed, regardless of whether the impact-angle constraint is considered or not. Different from all existing studies, the proposed method addresses the problem of time-to-go estimation without relying on any linearizing approximations or numerical iterations. To enhance the practicality of the proposed method, it is augmented with bias commands to result in either the impact time control guidance law or the impact time and angle control guidance law. Numerical simulation results demonstrate the higher accuracy, larger feasible solution region, and lower computational demand of the proposed guidance laws even for the missiles with nonconstant speeds.
Open Access
Gravity-turn-assisted optimal guidance law
(AIAA, 2017-07-31) He, Shaoming; Lee, Chang-Hun
This paper proposes a new optimal guidance law that directly uses (instead of compensating for) gravity for accelerating missiles. The desired collision triangle that considers both gravity and the vehicle’s axial acceleration is analytically derived based on geometric conditions. The concept of instantaneous zero-effort-miss is introduced to allow for analytical guidance command derivation. By formulating a finite time instantaneous zero-effort-miss regulation problem, the proposed optimal guidance law is derived through Schwarz’s inequality approach. The relationships of the proposed formulation with conventional proportional navigation guidance and guidance-to-collision are analyzed, and the results show that the proposed guidance law encompasses previously suggested approaches. The significant contribution of the proposed guidance law lies in that it ensures zero final guidance command and enables energy saving with the aid of using gravity turn. Nonlinear numerical simulations clearly demonstrate the effectiveness of the proposed approach.
Open Access
An image based visual servoing approach for multi-target tracking using an quad-tilt rotor UAV
(IEEE, 2017-12-31) Zarudzki, Mateusz; Shin, Hyosang; Lee, Chang-Hun
This paper proposes a guidance algorithm of a UAV for multiple targets tracking, considering physical constraints of the platform and its sensor. The on-board sensor used for target tracking is a camera. To relax the need of a gimbal system and provide flexibility in utilisation of the vision sensor, a new rotorcraft type of UAV is developed. The main focus in designing tracking guidance is to develop an image based visual servoing approach, appropriate to the newly developed platform. A complementary to the guidance system a control system for the unconventional UAV is also presented. Both control and guidance algorithms are based on the PID control techniques and this paper shows that the tracking guidance can be significantly simplified with the new type of UAV developed. The performance of the proposed tracking guidance along with the controller designed is validated by numerical simulations and flight tests.
Open Access
Impact time control based on time-to-go prediction for sea-skimming antiship missiles
(IEEE, 2018-02-07) Tahk, Min-Jea; Shim, Sang-Wook; Hong, Seong-Min; Choi, Han-Lim; Lee, Chang-Hun
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 and the impact angle control guidance law are extended by the proposed method for impact-time-control guidance and impact-time-and-angle-control guidance, respectively. The performance of the extended guidance laws is demonstrated by numerical simulation.
Open Access
New application of data analysis using aircraft fault record data
(AIAA, 2018-04-06) Lee, Chang-Hun; Shin, Hyosang; Tsourdos, Antonios; Skaf, Zakwan
Open Access
A new command shaping guidance law using Lagrange multiplier
(Elsevier, 2017-10-18) Lee, Chang-Hun; Shin, Hyosang; Tsourdos, Antonios; Lee, Jin-Ik
This article presents a new command shaping guidance law by change of Lagrange multiplier (LM), called CSGL-LM. The Schwarz inequality approach is used to solve the optimal guidance problems considering both terminal constraints on interception and impact angle control. LM is introduced to combine two terminal constraints into a single equation. The main idea of this paper is to use LM as a design parameter for shaping the guidance command as well as controlling the terminal constraints. The guidance command of CSGL-LM is given a unified functional form of the time-to-go, the state variables, and LM. Therefore, through an appropriate choice of LM, we can achieve various shapes of the guidance commands for the interception case, as well as the impact angle control case. As illustrative examples, this paper also shows that a class of previous guidance laws is just one of particular solutions of CSGL-LM. Numerical simulations are performed to validate the properties of CSGL-LM, compared with the conventional guidance law.
Open Access
New design methodology for impact angle control guidance for various missile and target motions
(IEEE, 2017-09-26) Seo, Min-Guk; Lee, Chang-Hun; Tahk, Min-Jea
This brief introduces a new design methodology for impact angle control guidance (IACG) laws. The proposed methodology can extend any proven homing guidance laws to their impact angle control versions if the expressions of the estimated terminal flight path angles under those guidance laws are given. The time derivatives of the estimated terminal flight path angles are obtained as functions of the guidance commands. The IACG versions of the homing guidance laws are derived from those functions and the desired error dynamics of the estimated terminal flight path angle. The guidance law of each IACG version has two terms: the first term maintains the characteristics and capturability of the original guidance law and the second term drives the estimated terminal flight path angle to converge to the specified flight path angle. When a well-understood homing guidance law for a certain combination of target and missile models is given, an IACG law for that combination is easily derived without reformulating the guidance problem again. The usefulness of the proposed method is demonstrated by several examples, deriving new IACG laws for various target and missile models.
Open Access
New insights into guidance laws with terminal angle constraints
(AIAA, 2018-04-19) Lee, Chang-Hun; Seo, Min-Guk
Introduction : In the field of guidance technology, advanced guidance laws are being developed using various control theories such as optimal control [1,2], sliding mode control [3–6], H-infinity control [7], the state-dependent Riccati equation [8], the Lyapunov theory [9], the geometric control theory [10], predictive control [11,12], and feedback linearization control [13]. The general procedure of this approach is to first establish the guidance problem to be solved and to define the guidance geometry and kinematics equation corresponding to the guidance problem. A guidance law is then systematically designed in such a way that an appropriate control theory is applied to a predetermined guidance problem. The potential importance of this approach is that a number of advanced guidance laws can be newly developed, depending on the combinations of guidance problems and control theories. Therefore, recent trends in the design of guidance laws focus on finding a new combination of guidance problems and control theory to obtain a new guidance law that is superior to the conventional guidance law. Although previous research has focused more on the methodology and the design process itself, little effort has been made toward understanding the characteristics of the newly developed guidance laws.
Open Access
A new multiple flights routing and scheduling algorithm in terminal manoeuvring area
(IEEE, 2018-12-10) Bae, Sangjun; Shin, Hyo-Sang; Lee, Chang-Hun; Tsourdos, Antonios
We address multiple flights planning problems from its initial waypoint to its destination while satisfying the minimum separation requirement between each aircraft at all times in a Terminal Manoeuvring Area (TMA) to maintain or increase runway throughput. Due to operational constraints for safety, most of the current aircraft fly over or by waypoints, and along nominal routes in the airspace. Where the waypoints and routes in the airspace can be modelled as a weighted digraph, called airspace graph. We propose a problem that consists of determining a flight path (routing problem) and its speed profile (scheduling problem) in a given airspace graph in which a time-based weighting scheme of the airspace graph is proposed to reflect a speed-limitation-compliant schedule that satisfy the minimum separation requirement. For multiple flights cases, the flight paths and schedules are obtained by iteratively solving the problem for each flight by applying the First Come First Served (FCFS) algorithm to determine an arrival sequence. The main contributions of this paper are increasing a solution search space by solving two problems simultaneously, efficient computational time, and providing the separation-compliant flight path and speed profile within the speed limitation for each flight. We demonstrate the advantages of the proposed approach through a case study in which multiple flights arrive at a single airport, and we compare the results with Regulated Tactical Flight Model (RTFM) obtained from EUROCONTROL Demand Data Repository 2 (DDR2). Although, we consider only a single airport and make an assumption to simplify flight routes from holding stacks to a Final Approach Fix (FAF), the results show the potential usage of the proposed algorithm as a Decision Support Tool (DST) for Air Traffic Controllers (ATCOs) if the following considerations are taken into account: detailed routes-based flights after the holding stacks, multiple airports, departing aircraft, all possibe aircraft types, and uncertainties produced by external sources.
Open Access
Nonlinear acceleration controller for exo-atmospheric and endo-atmospheric interceptors with TVC
(IEEE, 2017-07-20) Lee, Chang-Hun; Jun, Byung-Eul; Shin, Hyo-Sang; Tsourdos, Antonios
In this paper, we propose a nonlinear acceleration controller that can be used for both the endo- and exo-atmospheric interceptors with thrust vector control (TVC) without changing the control configuration. The acceleration perpendicular to the velocity vector is selected as the output to be controlled. Then apply the feedback linearization and the specific form of the desired error dynamics to create the resulting controller which is given by the well-known three loop control structure with parameter-varying control gains. According to changes in altitude operating conditions, the proposed controller can adaptively allocate the aerodynamic force and the thrust to produce the required normal acceleration. Also, we can have confidence in the reliability of the proposed controller because it is given by a similar form of the well-known three loop controller. Numerical simulations are performed to show the validity of the proposed method.
Open Access
Nonlinear autopilot design for endo- and exo-atmospheric interceptor with thrust-vector-control
(IEEE, 2019-06-05) Hong, Ju-Hyeon; Lee, Chang-Hun
This paper proposes an autopilot design for an interceptor with Thrust-Vector-Control (TVC) that operates in the endo- and exo-atmospheric regions. The main objective of the proposed autopilot design is to ensure control performance in both atmospheric regions, without changing the control mechanism. In this paper, the characteristics of the aerodynamic forces in both atmospheric regions are first investigated to examine the issue of the conventional control mechanism at various altitudes. And then, a control mechanism, which can be applied to both atmospheric regions, is determined based on the analysis results. An autopilot design is then followed by utilizing the control mechanism and the feedback linearization control (FBLC) method. Accordingly, the proposed autopilot does not rely on changing the control mechanism depending on flight condition unlike the conventional approach as well as it can adjust the control gains automatically according to the changes of flight operating conditions. In this paper, the robustness of the proposed autopilot is investigated through the tracking error analysis and the relative stability analysis in the presence of model uncertainties. The physical meaning of the proposed autopilot is also presented by comparing to the well-known three-loop control structure. Finally, numerical simulations are performed to show the performance of the proposed method.
Open Access
Optimal impact angle guidance for exo-atmospheric interception utilizing gravitational effect
(IEEE, 2018-09-24) He, Shaoming; Lee, Chang-Hun
This paper aims to develop a new optimal intercept angle guidance law for exo-atmospheric interception by utilizing gravity. A finite-time optimal regulation problem is formulated by considering the instantaneous zero-effort-miss (ZEM) and the intercept angle error as the system states. The analytical guidance command is then derived based on Schwarz's inequality approach and Lagrange multiplier concept. Capturability analysis using instantaneous linear time-invariant system concept is also presented to provide better insights of the proposed guidance law. Theoretical analysis reveals that the proposed optimal guidance law encompasses previously suggested optimal impact angle constrained guidance laws. Numerical simulations with some comparisons clearly demonstrate the effectiveness of the proposed guidance law.
Open Access
Optimal proportional-integral guidance with reduced sensitivity to target maneuvers
(IEEE, 2018-04-09) He, Shaoming; Lee, Chang-Hun
This paper proposes a new optimal guidance law based on proportional-integral (PI) concept to reduce the sensitivity to unknown target maneuvers. Compared to existing PI guidance laws, the proposed guidance command is derived in the optimal control framework while guaranteeing finite time convergence. The kinematics equation with respect to the zero-effortmiss (ZEM) is utilized and the integral ZEM is augmented as a new system state. The proposed guidance law is derived through the Schwarz's inequality method. The closed-form solution of proposed guidance law is presented to provide better insight of its properties. Additionally, the working principle of the integral command is investigated to show why the proposed guidance law is robust against unknown target accelerations. The analytical results reveal that the proposed optimal guidance law is exactly the same as an instantaneous direct model reference adaptive guidance law with a pre-specified reference model. The potential significance of the obtained results is that it can provide a point of connection between PI guidance laws and adaptive guidance laws. Therefore, it allows us to have better understanding of the physical meaning of both guidance laws and provides the possibility in designing a new guidance law that takes advantages of both approaches. Finally, the performance of the guidance law developed is demonstrated by nonlinear numerical simulations with extensive comparisons.
Open Access
Optimality of error dynamics in missile guidance problems
(2018-02-21) He, Shaoming; Lee, Chang-Hun
Open Access
Sense and avoid using hybrid convolutional and recurrent neural networks
(Elsevier, 2019-11-25) Navarro, Daniel Vidal; Lee, Chang-Hun; Tsourdos, Antonios
This work develops a Sense and Avoid strategy based on a deep learning approach to be used by UAVs using only one electro-optical camera to sense the environment. Hybrid Convolutional and Recurrent Neural Networks (CRNN) are used for object detection, classification and tracking whereas an Extended Kalman Filter (EKF) is considered for relative range estimation. Probabilistic conflict detection and geometric avoidance trajectory are considered for the last stage of this technique. The results show that the considered deep learning approach can work faster than other state-of-the-art computer vision methods. They also show that the collision can be successfully avoided considering design parameters that can be adjusted to adapt to different scenarios.