Do-Myung Kim

A Modified Nonlinear Guidance Logic for a Leader-Follower Formation Flight of Two UAVs

This paper presents a guidance algorithm for formation flight of two UAVs. Since the nonlinear guidance algorithm have good properties to follow nonlinear flight trajectory based on geometric and kinematic, the nonlinear guidance algorithm is modified as a leader-follower station keeping formation control law for two UAVs using the relation of the nonlinear guidance algorithm to the proportional navigation. The proposed guidance algorithm provides a good performance and relatively simple control logic. The performance of the proposed guidance algorithm is tested via semi-flight test environment that is composed of near-real-time simulation for the leader and real flight for the follower.

A Glidepath Tracking Algorithm for Autolanding of a UAV

In this paper, a glidepath tracking algorithm of a UAV was proposed and the performance was analyzed. The glidepath tracking strategy was implemented using precision longitudinal flight control law. A performance output- based design method was proposed for smooth transition to the new state minimizing saturation of the control effectors. By comparison with several LQ servo design methods such as Brysons general rule and frequency domain matching method, the suggested design shows fast and smooth responses through numerical simulation. Furthermore, the performance of the strategy was investigated through the touch down point(TDP) error analysis with regard to atmospheric disturbance. It was verified that the proposed glidepath tracking strategy can be successfully applied to the practical autolanding of UAV systems.

Development of near-real-time simulation environment for multiple UAVs

This paper describes development of a simulation environment for multiple UAVs. The simulation environment consists of several PCs, each of them represents simulated motion of individual UAV and a host PC that controls and monitors the whole UAVs. UAVs can fly individually or sometimes they can cooperate to fly in formation following the leader. Each UAV has inherent stabilization capability and autopilot, while the leader UAV can monitor the motion of other UAVs and perform group coordination. Flight information of one UAV can be transferred to the other UAVs via UDP communication. Several simulation flight sorties were performed from individual flight to formation flight in order to demonstrate the multi-vehicle simulation environment.

GPS Output Signal Processing considering both Correlated/White Measurement Noise for Optimal Navigation Filtering

In this paper, a dynamic modeling for the velocity and position information of a single frequency stand-alone GPS(Global Positioning System) receiver is described. In static condition, the position error dynamic model is identified as a first/second order transfer function, and the velocity error model is identified as a band-limited Gaussian white noise via non-parametric method of a PSD(Power Spectrum Density) estimation in continuous time domain. A Kalman filter is proposed considering both correlated/white measurements noise based on identified GPS error model. The performance of the proposed Kalman filtering method is verified via numerical simulation.

Flight test of a Flying-Wing Type UAV with Partial Wing Loss Using Neural Network Controller

This paper presents flight test result of flying-wing type UAV with partial wing loss using neural network controller. 22% and 33% loss of wing area moment were considered for the damage configuration. A new trim state was obtained for each damaged model with the variation of mass, center of gravity and moment of inertia. A numerical simulation was performed to investigate the changed flight dynamics. It is verified that the damaged UAV shows sluggish roll behavior with unstable longitudinal response. A neural network based adaptive controller combined with feedback linearization was designed in order to compensate for the partial damage. It is verified that the instability caused by partial wing damage can be effectively controlled, and the overall system can be stabilized via neural network controller.

Development of a 3D Position Determination Device using PSD sensor

In this paper, a new 3D-PDD (Position Determination Device) is developed based on PSD (Position Sensitive Detector) sensor. Vision sensor uses PSD camera modules, and relative position and distance from a target point to PSD sensors are calculated via stereo vision. A LED driver module at target point consists of IR LEDs and LED driver chip, and emits Infrared Ray proportional to the relative distance. DSP module processes analog signal from PSD sensors and band pass filter. Camera calibration is implemented by way of high order polynomial in order to compensate lens distortion. Effectiveness of the proposed method will be demonstrated via integrated ground test.

Modified nonlinear guidance logic for formation flight of two UAVs

This paper presents a guidance logic for formation flight of two UAVs. Since the nonlinear guidance logic have good properties to follow nonlinear flight trajectory based on geometric and kinematic, the nonlinear guidance logic is modified as a leader-follower station keeping formation control law for two UAVs using the relation of the nonlinear guidance logic to the proportional navigation. The proposed guidance logic provides a good performance and relatively simple control logic. The performance of the proposed guidance logic is tested via various numerical simulations using developed multiple UAVs simulation environment.

MTF Analysis for the Image Performance Prediction of Observation Satellites

The prediction of image performance of an observation satellite necessitates analysis of the performance of a satellite payload and the static/dynamic characteristics of a spacecraft in the space environment. This paper introduces essential performance indices and their systematic relationships required to estimate and analyze image performance of an observation satellite. It also presents techniques and methods of integrated modeling for efficient evaluation of image performance. And the results of a system MTF (modulation transfer function) prediction are given with a consideration of each subsystem MTF of an observation satellite