• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.373-381
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• 2020

Quadrotor is simple to model because of the symmetric structure but it has the disadvantage of being relatively sensitive to the external disturbance and system uncertainty. The PID technique applied for the attitude control of quadrotor has been applied comprehensively, but it has a disadvantage that is hard to precise control in the nonlinear system. In this work, a quadrotor attitude control law using the super twisting algorithm is studied, which has robust characteristics against disturbance and system uncertainty. To evaluate the attitude performance by the proposed technique, simulation studies and actual flight tests are carried out, and compared with the conventional PID controller.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.217-225
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• 2013

Typical quadrotor aircraft use four differential thrust vectors to control the motion. In this study, we design a quadrotor aircraft using collective and cyclic control to improve the shortcomings of existing quadrotor aircraft. The quadrotor aircraft with cyclic control can fly at various attitudes due to the excessive control degrees of freedom. Hence the quadrotor aircraft with cyclic control is suitable as high performance aircraft. In this study, modeling and stability analysis of the quadrotor aircraft have been performed using FLIGHTLAB. LQR control systems were designed using linear models at various flight conditions and verified through nonlinear simulations using MATLAB.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.219-222
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• 2013

최근 몇 년간 무인항공기(UAV) 시장이 점차 커지면서 군뿐만 아니라 민간, 상업적으로도 무인항공기의 수요가 증가하고 있다. 이에 무인항공기의 한 종류인 에어드론(AR.Drone)을 활용한 실시간 원격 쿼드로터(Quadrotor) 퓨전제어기법을 제안하였다. 특히, 본 논문에서는 아이폰(i-phone) 기반의 제어기법이 아닌, 안드로이드(Android) 기반의 퓨전제어기법을 통하여 에어드론을 실시간으로 원격조정가능하게 했는데, 이는 아이폰 App 개발 시 제공되는 API와 PC 기반의 쿼드로터 제어기법을 퓨전하는 방식으로 쿼드로터의 비행제어와 영상처리를 분리시켜 기존의 방식보다 영상처리 속도를 향상시키는 방식이다. 그리고 제안된 퓨전제어기법의 우수성을 보여주기 위해, 기존의 방식들과 영상처리 속도를 비교분석하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.2
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• pp.118-128
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• 2012

The goal of this paper is to design the target tracking controller for a quadrotor micro UAV using a vision sensor. First of all, the mathematical model of the quadrotor was estimated through the Prediction Error Method(PEM) using experimental input/output flight data, and then the estimated model was validated via the comparison with new experimental flight data. Next, the target tracking controller was designed using LQR(Linear Quadratic Regulator) method based on the estimated model. The relative distance between an object and the quadrotor was obtained by a vision sensor, and the altitude was obtained by a ultra sonic sensor. Finally, the performance of the designed target tracking controller was evaluated through flight tests.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.6
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• pp.877-884
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• 2005

The importance and usefulness of a subjective evaluation of the sensorial properties of scoured silk fabrics is discussed. Silk fabric was treated at 12 different scouring rates and the scoured fabrics were used as specimens. Using paired comparisons, three trained subjects, evaluated seven subjective sensorial properties; softness, elasticity, drape, stiffness, crispness, and luster. A quad experimental design was adopted as an effective and reliable evaluation method. Results showed that some properties such as drape, luster were easily discriminated depending on the scouring rates whereas the smoothness was not easily discriminated. As the scouring rate increased, it was hard to discriminated the softness, drape, and stiffness, which indicates there is an optimum scouring rates to have a certain sensorial properties. It was suggested that these results should be applied to the manufacturing process.

• Journal of IKEEE
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• v.24 no.1
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• pp.106-119
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• 2020

In this paper, we propose a control scheme for quadrotor system using a pole placement method. When using a state feedback controller, a lot of trial and error in selection of control gains are often required to improve system performance. In order to relax this complicated process, we analyze the closed-loop system associated with control gains. Then, we present a control gain selection algorithm for control gains using a pole placement method to improve the system performance. The proposed control method is applied to the actual quadrotor system to illustrate the validity of the proposed method.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.163-166
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• 2012

OpenMP를 이용할 경우 컴파일러 디렉티브의 삽입으로 병렬화가 가능하다. 본 논문은 쿼드 트리를 이용한 데이터베이스 검색 프로그램을 OpenMP로 병렬화하여 실험을 진행한다. 실험을 통해 논리코어의 개수와 쓰레드 개수에 따른 상관관계가 적다는 것을 알 수 있다. 또한 쓰레드 개수 증가에 따른 오버헤드 발생이 성능에 영향을 준다는 사실을 알 수 있다. 쿼드 트리 자료구조를 이용한 데이터베이스 검색 프로그램을 OpenMP를 이용해 병렬화할 경우 논리적 코어의 개수가 8개, 쓰레드 개수가 16개일 경우에 1.8배의 최대의 성능향상을 이룬다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2335-2342
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• 2014

If you want to use the unmanned quad rotor for emergency information provision and information about the traffic situation of real-time and moving information is included in the car to help in emergency vehicle operation of the city and in the distribution future innovation the need to consider to have enough safety of the use of silent quad rotor. Therefore, in this study, the unmanned quad rotor system research of safe landing control from the center for the improvement of safety of unmanned quad rotor system you have a motor of four, has taken a good structural balance system based on the dynamic model and motion considering the nonlinear characteristics, and attempts to proceed via non-linearity and system disturbances, tough Fuzzy controller, and analyzed through a computer simulation result.

• Journal of Broadcast Engineering
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• v.8 no.4
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• pp.473-480
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• 2003

In this paper, we propose a new quadtree coding a1gorithm to improve the performance of the old one. The new algorithm can process any frame of size in standard and reduce encoding and decoding time by decreasing computational load. It also improves the image quality comparing with any old quantizer based on quadtree and zerotree structure. In order for the new algorithm to be applied for real video codec, we analyze the statistical characteristics of coefficients of differential image and add a function that makes It deal with an arbitrary size of image by using new technique while the old one process by block unit. We can also improve the image quality by scaling the coefficient's value from a differential image. By comparing the performance of the new algorithm with quadtree and SPIHT, it Is shown that PSNR is improved, that the computational load is not reduced in encoding and decoding.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.9
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• pp.1019-1025
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• 2014

Recently, the studies of the Unmanned Aerial Vehicle(UAV) has been studied a variety from military aircraft to civilian aircraft and for general hobby activity aircraft. In particular, for small unmanned aircraft research for the ease of turning and hovering and Vertical-Off Take Landing(VTOL), have been studied mainly quadrotor unmanned aircraft is a type suitable for this study of small unmanned aircraft. The studies of these unmanned aircraft is the kinetic analysis requires complex processes, because these support by the aerodynamic forces on the unmanned aircraft study, and the controller design based on these dynamical analysis and experimental model analysis. In this paper, after the implementation of the basic attitude control based on a general PID controller, we propose concept design of the attitude control method on quadrotor attitude control by using the reinforcement learning algorithm of neural networks for non-linear elements not considered in the controller design.