http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Ngoc Hung Phi,Bui Huu Nguyen,Jong-Wook Lee 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
Beyond the first three generations of metamaterials, space-time metamaterials provide the important capability for dynamically manipulating the electromagnetic wave. By controlling the structure parameters, the metamaterial could exhibit the nonreciprocal characteristic implying that wave propagates in different ways when interchanging source and observation points. Due to depending on multiple parameters, this characteristic is difficult to investigate. In this paper, we propose a time-varying metamaterial-based waveguide that breaks the reciprocity nature. After that, we apply Deep Neural Network (DNN) algorithm to determine which parameter sets show this property. The results show that DNN successfully predicts the forward and backward transmission difference with high accuracy: 99.2% and 98.8% of 1,472 cases for each have mean square error (MSE) of less than 2.5×10<sup>-3</sup>. In addition, comparing to ADS simulation, the computation time can be decreased 1,500 times.
Ngoc Hung Phi,Bui Huu Nguyen,Alsaadi Abdulrahman,Jong-Wook Lee 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
Time periodic circuits with space-time modulation have recently attracted significant interest for their appealing properties such as reflection reduction, frequency conversion and nonreciprocity. In circuit-based structures, space-time modulation is synthesized by integrating nonlinear elements into their periodic structure. The intriguing phenomena occurring when combining these two aspects leads to determining the dispersion relation; it exhibits all the interaction types of electromagnetic waves, expanded in spatial harmonics. In this study, we investigate the dispersion characteristic of the left-hand metamaterial waveguide using the periodic circuit theory combined with Bloch-Floquet condition. The nonreciprocal properties of waves in the meta-material waveguide are analyzed using this dispersion relation. In particular, the horizontal distance difference between the harmonics illustrates how strong the nonreciprocity occurs when different modulation frequency ratios are used. Finally, results of the transmission coefficient demonstrate how the dispersion relation is expressed realistically.
Bui Huu Nguyen,Ngoc Hung Phi,Seneke Chamith Chandrarathna,Jong-Wook Lee(이종욱) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
Wireless power transfer (WPT) is a convenient method of delivering energy to multiple devices without connecting wires. To further enhance WPT efficiency, unique characteristic metamaterials, such as electromagnetic field focusing, have been successfully utilized. Normally, metamaterial characteristics depend on multiple parameters. Several metamaterial designs require a significant amount of time to complete numerical simulation. In this work, we propose a rapid design metamaterial method using a deep neural network (DNN). When DNN is used, the results show an accuracy of 98.1% and an accumulated mean square error (MSE) less than 0.3×10<sup>-3</sup>. For synthesizing the design parameters, the MSE is less than 8×10<sup>-3</sup>. Besides, the computation time of the 1000 samples can be reduced 85×10<sup>3</sup> times compared to the HFSS simulation.
Daewon Park,Hansol Jeong,Nguyen Ngoc Phi,Sung Kyung Hong 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10
This paper presents a robust formation tracking control algorithm for multi-agent system in a finite time. For faster convergence and less steady state error than the existing formation tracking algorithm, we first propose a fast and robust formation tracking control algorithm by using the fast terminal sliding mode control. Then, a disturbance observer algorithm is added to formation tracking control law to handle external disturbances. The stability of the algorithm is verified by Lyapunov theory. The numerical simulation is proposed to show the effectiveness of proposed method using MATLAB environment.
Multi-sensor-based Target Pose Estimation for Autonomous Precision Perching of Nano Aerial Vehicles
Truong-Dong Do,Nguyen Xuan-Mung,Ngoc-Phi Nguyen,Ji-Won Lee,Yong-Seok Lee,Seok-Tae Lee,Sung-Kyung Hong 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
Nano Aerial Vehicles have become widely used for a variety of complex missions due to their mobility and the ability to access hard-to-reach areas. In most cases, these tasks require the vehicles to land on ground targets or perch on platforms mounted on diverse surfaces. Considering the surface the vehicle will reach, controlling perching is obviously a challenging task. Besides, the reliability of target position and direction estimation has a significant impact on perching performance. In this paper, a multi-sensor-based target pose estimation for autonomous precision perching of nano drones is proposed. First, the perching target, a cube cage containing a small marker inside a larger one, is designed to enhance pose estimation capability at a wide range of distances. Second, we constructed a nano drone with an upward monocular camera and a 5-direction multi-ranger deck. Next, the flying vehicle’s pose toward the perching target is calculated, followed by a Kalman filter for filtering and estimating the missing data. Finally, we introduced an algorithm to merge the pose data from multiple sensors when drones approach close to the target. Real measurements are conducted on the testbed. The experimental results demonstrated the utility and potential of the adopted approach with millimeter-level precision.