Eung-Tai Kim

A study on the parameter estimation of DURUMI-II for the fixed right elevator using flight test data

The stability and control derivatives of DURUMI-II UAV using the flight test are obtained. The flight test data is gathered from the normal flight condition (normal mode) and the flight condition assumed as the right elevator fixed (fault mode). Using real-time parameter estimation techniques, applied to Fourier transform regression method, simulates the aircraft motion. From the result, the fault of control surface is to be detected. In this paper, the results of the real-time parameter estimation techniques are compared with the results of the Advanced Aircraft Analysis (AAA). Using the aerodynamic derivatives, it provides the base line of normal/failure for the control surface by using the on-line parameter estimation of Fourier transform regression. In flight, this approach maybe helpful to detect and isolate the fault of primary control surface. It is explained how to perform the flight condition assumed as the right elevator fixed in the flight test. Also, it is mentioned how to switch between the normal flight condition and the assumed fault flight condition.

A Track Scoring Function Development for Airborne Target Detection Using Dynamic Programming

Track-before-detect techniques based on dynamic programming have provided solutions for detecting targets from a sequence of images. In its application to airborne threat detection, dynamic programming solutions should take into account the distinguishable properties of objects in a collision course. This paper describes the development of a new track scoring function that accumulates scores for airborne targets in Bayesian framework. Numerical results show that the proposed scoring function has slightly better detection capabilities.

Vision-based long-range target detection using coarse-to-fine particle filter

In this study, we develop a coarse-to-fine particle filter algorithm for track-before-detect in order to track a subpixel-sized, low signal-to-noise ratio target in sensor data. The proposed algorithm enhances tracking performance in the presence of target motion uncertainty and it also maintains the computational load without increasing the number of particles. This coarse-to-fine particle filter, which is newly applied to track-before-detect, has two recursive stages: a coarse stage for extensive searches of the target’s state space and a fine stage that narrows down the tracking results. During the coarse stage, particles are propagated with uniformly distributed noise to compensate for highly nonlinear target motion. The fine stage disturbs the particles filtered from the coarse stage using Gaussian distributed noise. Monte Carlo simulation results using artificial image sequences indicate improved performance with the proposed algorithm when uncertain large frame-to-frame pixel differences are caused by nonlinear target motions such as jittering effects. The algorithm is also applied to the real camera image frames to verify its detecting performance.

Application of Control Allocation Methods to SAT-II UAV

This paper focuses on applying various control allocation schemes to SAT-II UAV system. Control allocation is a useful method for controlling an aircraft with redundant control surfaces and deals with distributing control commands among individual actuators when some control surfaces are failed. In order to implement control allocation scheme in the aircraft control system, control system has to be designed through two step procedures. The first step is to design a baseline control system specifying total control command to be produced, and the second step is to design a control allocator that maps the total control command on individual actuators. The baseline control system of the SAT-II UAV is constituted of speed, altitude, and lateral deviation controllers for tracking a predetermined glide path during automatic landing phase. In the baseline control system, proportionalintegral controllers and lead/lag compensators are effectively combined to assure enough gain and phase margins. Several control allocation methods such as pseudoinverse control allocation method, daisy chain control allocation method, direct control allocation method, and optimization based control allocation methods are considered in this paper. The performance of these methods is evaluated and compared to each other through the nonlinear simulation under the assumption that right aileron failed and are stuck at fixed deflection position during the glide approach phase.

Track-Before-Detect Algorithm for Multiple Target Detection

Vision-based collision avoidance system for air traffic management requires a excellent multiple target detection algorithm under low signal-to-noise ratio (SNR) levels. The track-before-detect (TBD) approaches have significant applications such as detection of small and dim targets from an image sequence. In this paper, two detection algorithms with the TBD approaches are proposed to satisfy the multiple target detection requirements. The first algorithm, based on a dynamic programming approach, is designed to classify multiple targets by using a k-means clustering algorithm. In the second approach, a hidden Markov model (HMM) is slightly modified for detecting multiple targets sequentially. Both of the proposed approaches are used in numerical simulations with variations in target appearance properties to provide satisfactory performance as multiple target detection methods.

Analysis on Flight Test Results of Reconfiguration Flight Control System

This paper presents the analysis results obtained by the flight test of reconfiguration flight control system for an aircraft. The reconfiguration flight control system was designed by using control allocation scheme that automatically distributes the demanded control moments determined by control law to each actual control surface. In this paper, some control allocation algorithms for reconfiguration control of general aircraft with redundant control surfaces are summarized and their performance evaluation results through nonlinear simulation and Hardware-In-the-Loop-Simulation (HILS) test are shown. Also, Unmanned Aerial Vehicle (UAV) system adopted as a platform for the flight test of reconfiguration flight controller and the implementation procedure of reconfiguration flight controller into real-time UAV system were introduced. Finally, flight test results were analyzed.

Development of Altitude Determination System by Using GPS/INS/Baroaltimeter

This paper introduces an altitude determination algorithm using GPS/INS/Baroaltimeter and evaluates the algorithm by real field tests. The test results show that the proposed method can determine the altitude of an aircraft continuously and sensitively. Therefore, it is appropriate to be used as an altimeter for a flight control system, especially for the automatic take-off and landing. In addition, it is shown that the second and the third baro-inertial vertical channel damping methods are essentially complementary filters while the proposed scheme improves these complementary filters.棜?⨀ᔌ툀؀㌸㜮ㄻ

비행시험을 통한 소형 커나드항공기의 비행 특성 연구

This paper presents the analysis of the flight test data measured by the sensors installed on a four-seat canard aircraft. The inherent stall proof characteristics of canard aircraft was verified from the stall test. The dihedral effect, adverse yaw and roll control power were examined and the neutral point that determines the longitudinal stability of the aircraft was investigated. The dynamic characteristics such as dutch roll mode were also examined. Without relying on the parameter identification method, the aerodynamic derivatives or the relations between the aerodynamic derivatives were obtained by analyzing the steady state flight data.

Reconfiguration Control Using LMI-based Constrained MPC

In developing modern aircraft, the reconfiguration control that can improve the safety and the survivability against the unexpected failure by partitioning control surfaces into several parts has been actively studied. This paper deals with the reconfiguration control using model predictive control method considering the saturation of control surfaces under the control surface failure. Linearized aircraft model at trim condition is used as the internal model of model predictive control. We propose the controller that performs optimization using LMI (linear matrix inequalities) based semi-definite programming in case that control surface saturation occurs, otherwise, uses analytic solution of the model predictive control. The performance of the proposed control method is evaluated by nonlinear simulation under the flight scenario of control surface failure.

Sensor Fusion of GPS/INS/Baroaltimeter Using Wavelet Analysis

This paper introduces an application of wavelet analysis to the sensor fusion of GPS/INS/baroaltimeter. Using wavelet analysis the baro-inertial altitude is decomposed into the low frequency content and the high frequency content. The high frequency components, ‘details’, represent the perturbed altitude change from the long time trend. GPS altitude is also broken down by a wavelet decomposition. The low frequency components, ‘approximations’, of the decomposed signal address the long-term trend of altitude. It is proposed that the final altitude be determined as the sum of both the details of the baro-inertial altitude and the approximations of GPS altitude. Then the final altitude exclude long-term baro-inertial errors and short-term GPS errors. Finally, it is shown from the test results that the proposed method produces continuous and sensitive altitude successfully.