• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.3
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• pp.26-30
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• 2012

This paper presents the observer design method for discrete-time nonlinear systems with delayed output. It is shown that by considering a nonlinear term of error dynamics as an additional state variable, the discrete-time nonlinear error dynamics with time delay can be transformed into the discrete-time linear one with time delay. Sufficient conditions for existence of state observer are characterized by linear matrix inequalities. Finally, an illustrative example is given in order to show the effectiveness of our design method.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.171-176
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• 2015

일반적으로 어떠한 계의 크기가 커지면 확산계수 (Diffusion coefficient, D) 는 증가하는 것으로 알려져 있다. 본 연구에서는 원자의 개수와 계의 크기를 증가시키면서 정방계와 직방계에서의 확산계수를 계산하였다. 확산계수를 계산하는 방법으로 Einstein-Smoluchowski 관계식을 사용하였다. 정방계에서 x, y, z축의 확산계수를 계산해본 결과, 계의 크기와 원자의 개수가 증가할 때 각 축의 확산계수도 같이 증가하는 것을 확인할 수 있었다. 그리고 직방계에서 x, y축의 셀 길이를 고정시키고 z축의 셀 길이를 늘여가며 확산계수를 계산해본 결과, x, y축의 확산계수는 정방계와 비슷하게 증가하는 경향을 보였으나 z축의 확산계수는 변화가 거의 없음을 확인할 수 있었다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.140-147
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• 2015

In this paper, we propose a state feedback robust controller of 2-axis gimbal system which have bounded parametric uncertainty. The proposed controller is robust against dynamics variations of gimbal system and contains a dynamic compensator in order to improve a steady state error and a transient response. The stability of the closed-loop system is proved by Lyapunov approach. The performance of the proposed method is demonstrated by simulation on a 2-axis gimbal system.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1166-1173
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• 2011

There have been many researches about SUGV (Small Unmanned Ground Vehicle) mechanism regarding off-road mobility and obstacle negotiation. This paper introduces an analysis of geometry parameters to enhance the vertical obstacle negotiation ability for the SUGV. Moreover, this paper proposes an anti-shock structure analysis of wheels to protect the main body of the SUGV when it falls off a vertical obstacle. Major system geometry parameters will be determined under certain constraints. The constraints and optimization problem for maximizing the ability of vertical obstacle negotiation will be presented and discussed. Dynamic simulation results and experiments with manufactured platform will also be presented to validate the analysis. Several types of wheel materials and structures will be compared to determine the best anti-shock wheel design through FEM (Finite Element Method) simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2554-2561
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• 2015

In this paper, we strengthen the advantages of a simple PID controller as a study on the formation control of mobile robots and propose an adaptive PID controller with robust performance at the dynamics characteristics of following robot. Simulation studies show that the adaptive PID controller has better keeping constant distance and angle such as tracking performance of following robot for the formation control than a conventional PID controller. This is the proposed adaptive PID controller to change the gains is found to represent the best performance. This is able to verify that the performance of the proposed adaptive PID controller is excellent.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.170-178
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• 2017

This paper proposes an improved path-planning technique based on the $A^*$ algorithm. The conventional $A^*$ algorithm only considers the optimality of the planned path and sometimes produces a path that an unmanned underwater vehicle (UUV) cannot navigate due to its dynamic constraint such as the limit of the radius of gyration. It is because that the previous method evaluate the moving cost based on the straight distance between nodes. We enhance the conventional method by evaluating the moving cost on the basis of the practically navigable trajectory, which is generated by the waypoint-tracking control of the UUV dynamics. The simulation examples indeed show the effectiveness of the proposed technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.503-509
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• 2014

In this paper, a PID controller with adaptive neural network compensator is proposed to control the formations of mobile robot. The control system is composed of a kinematic controller based on the leader-following robot and dynamic controller for considering the dynamics of the mobile robot. The dynamic controller is constituted by a PID controller and the adaptive neural network compensator for improving the performance and compensating the change in dynamic characteristics. Simulation results show the performance of the PID controller and the neural network compensator for the circular trajectory and linear trajectory. And it is verified that by improving the performance of a PID controller via the adaptive neural network compensator, the following robot's tracking performance is improved.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.165-178
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• 2021

We studied driftwood behaviors including generation and deposition in a tsunami using a numerical simulation. We used an integrated two-dimensional numerical model, which included a driftwood dynamics model. The study area was Sendai, Japan. Observation data collected by Inagaki et al. (2012) were used to verify the simulation results by comparing them with driftwood deposition patterns. A simplified model was developed to consider the threshold of driftwood generation by the drag force of water flows. To consider the volume of driftwood generated, we estimated the total wood number in the study area using Google Earth. Therefore, we simulated more than 13,000 pieces of driftwood that were generated and transported inland from approximately 300,000 trees that were growing in the forest. The final distribution of the driftwood was similar to the observation data. The reproducibility of the generation and deposition patterns of driftwood showed good agreement in terms of longitudinal deposition pattern. In the future, a sensitivity analysis on driftwood parameters, such as the size of the wood, boundary conditions, and grid size, will be implemented to predict the travel patterns of driftwood. Such modeling will be a useful methodology for disaster prediction based on water flow and driftwood.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1811-1817
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• 2014

In this paper, a PID controller with interpolated gains by use of neural networks is proposed for the formation control problem that following robots track a leading robot with constant distances and angles when there are changes in the mass of the following robot. The whole control system is composed of a kinematic controller and a dynamic controller considering the robot dynamics. The dynamic controller is the PID controller with varying gains, and the proper gains are obtained for some representative masses of the follower robot by the genetic algorithm. Neural networks is trained using the genetic algorithm with the gain data obtained in the previous step. The trained neural network determines optimal PID gains for a random mass of following robot. Simulation studies show that for arbitrary masses of the tracking robot, the PID controller with interpolated gains by the trained neural network has better tracking performance than that of the PID controller with fixed gains.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.230-230
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• 2022

최근 기후변화로 인해 예측이 어려운 국지성 호우가 빈번하게 발생하고 있다. 국지성 호우는 대량의 홍수를 일으켜 유송잡물을 동반한 흐름을 야기할 수 있다. 대량의 유송잡물이 하상에 퇴적되면 통수능을 저하시키기도 하며 식생효과와 마찬가지로 유목주변으로 유속이 증가하면서 세굴현상이 발생하게 되는데, 이는 하상저하를 일으키며 수공구조물의 안정성에 지속적으로 피해를 줄 수 있다. 기후변화는 또한 강우패턴을 변화시켜 식생의 성장과 활착에도 영향을 미치게 된다. 본 연구지역인 내성천 회룡포의 경우, 2015년 대가뭄 발생 이후 식생활착으로 인해 식생대 면적이 증가하고 잇는 상황이다. 이는 연구지역의 흐름과 사주교란 및 하상변동에도 큰 영향을 미칠 것으로 판단되며, 특히 식생의 증가는 유송잡물의 증가를 야기 할 수 있기 때문에 식생과 유송잡물의 영향이 하천에 미치는 영향을 예측하는 연구가 필요할 것으로 판단된다. 따라서 본 연구에서는 2차원 흐름모형인 Nays2D와 입자법기반의 유목동역학 모형을 활용하여 식생과 유송잡물이 하상변동에 미치는영향에 대한 수치실험을 수행하고 결과를 분석하였다. 여기서, 식생의 경우, 식생성장모형을 적용하여 시간에 따라 식생이 성장하여 항력이 증가하는 것으로 가정하였으며 유송잡물의 경우, 하상에 퇴적되는 유송잡물의 개수와 면적만큼 항력이 증가하는 것으로 가정하였다. 흐름의 경계 조건은 일반화된 부정류 수문곡선을 입력하였으며 초기 하도의 형상은 일정한 경사를 가지는 평지로 가정하여 부정류에 따라 하상변동이 발생하는 것으로 모의하였다. 시뮬레이션 결과, 유송잡물보다 식생대 번성이 하상변동에 상대적으로 큰 영향을 주는 것으로 나타났으며, 유송잡물의 경우 국부적으로 퇴적 분포되어 그 주변으로 침식을 일으키는 것으로 나타났다. 또한 유송잡물은 하안의 얕은수역에서 주로 퇴적되었다. 본 연구는 만곡부 하상변동에 대해 식생과 유송잡물을 고려하여 예측모의를 수행한 사례로서, 식생과 유송잡물이 흐름과 하상변동에 미치는 영향을 이해하는데 도움이 될 것으로 판단된다. 또한 이는 추후에 식생을 고려하는 하천관리방안을 수립 시, 식생과 유송잡물의 영향을 물리적으로 설명할 수 있는 근거자료로 제시할 수 있을 것으로 보인다.