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RISS 인기검색어
- 검색키워드
- 저자 : Nguyen Anh Tung (검색결과 2 건)
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Collision-free Formation Control of Multiple Nano-quadrotors
Nguyen Anh Tung 세종대학교 대학원 2021 국내석사
Multi-agent systems have gained massive popularity among recent fascinating research topics with a view to performing large-scale interconnected systems in a colossal number of real-world applications. This thesis presents the development and implementation of formation control utilized to manage multiple nano-quadrotor systems. The aim of this work is to develop a theoretical framework for the time-varying formation flight of the multi-quadrotor system with consideration to anti-collisions. In order to achieve this goal, finite cut-off potential functions are devoted to avoiding the occurrence of collisions among agents in the group as well as between an agent and an obstacle/adversary. Then, in light of Lyapunov's direct method, the control algorithm navigates the group of quadrotors to asymptotically reach an anticipated time-varying formation. The validity and effectiveness of the proposed approach are demonstrated via numerical results and several experimental scenarios. Two case studies corresponding to available laboratory equipment are employed to show powerful demonstrations of the proposed algorithm. With hopes of performing actual tests, this thesis provides the implementation of techniques utilized to operate Crazyflies nano-quadrotors, one of the most popular indoor practical platforms.
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Dynamic notification aggregation CoAP based on Markov chain
Nguyen Tung Anh Korea University 2019 국내석사
Nowadays, wireless sensor networks (WSNs) have greatly influenced many aspects of society. WSNs can be defined as a network of spatially dispersed devices and sensors that are capable of exchanging information collected from a manipulated area through a wireless link. Devices and sensors are nodes acting as tiny computers. They are embedded devices in charge of detecting physical or environmental conditions, producing output in the form of an electrical signal that is delivered to an operator for further processing. WSNs are able to cover a great number of spatially distributed nodes, from just a few to several hundred, or even thousands. Size and cost constraints on sensors and embedded devices generate obstacles for WSNs, for example, needing low energy consumption, and having limited memory and restricted computational ability and communications bandwidth. Furthermore, as a demand of development, WSNs must be compatible with the Internet. Thus, Constrained Application Protocol (CoAP) and Observing Resources in CoAP (CoAP/Observe), which follow the client/server paradigm, were proposed by the Internet Engineering Task Force (IETF) in the context of low-power and low-rate networks for tackling the aforementioned problems. CoAP is a representational state transfer application protocol for constrained nodes and constrained (e.g, low-power, lossy) networks. Although CoAP is designated under the client/server paradigm, a node can be a server or a client, depending on its function. CoAP creates favorable conditions to communicate between nodes and with the wider Internet using identical protocols. Thanks to compatibility with Hypertext Transfer Protocol (HTTP), CoAP provides a way to exchange information not only between nodes in constrained networks but also between constrained network and general nodes on the Internet. CoAP/Observe extends the original CoAP protocol and relies on the design pattern from the Gang of Four (GOF). CoAP/Observe is a model of the best-effort approach, which tries to keep the same state in both client and server with low power consumption. To reduce the power consumption in nodes, states are transmitted to the client when resources meet particular conditions, called CoAP Conditional Observe. This method also makes the sending time between two states a random variable, which generates diverse approaches to mathematically model for the reduction of power consumption. Due to increasing amounts of sensor overtime, many responses will be transmitted over WSNs. Although other CoAP Conditional Observe methods have made great contributions to the diminished energy of nodes in a constrained network, they are still not resilient. In this thesis, an approach to reducing energy consumption in constrained devices based on CoAP Conditional Observe is proposed. The proposed method relies on a Markov process with its probability transition matrix for predicting packets to combine in order to save energy. It is plausible that there are many methods to forecast opportunities for aggregation of packets. But the Markov process was chosen in this research because its approach requires low computational power and energy, which is appropriate to constrained nodes and WSNs. In this thesis, a mathematics model and an algorithm are proposed. For evaluating the efficiency of the proposed method, CoAP and CoAP Conditional Observe are used as baselines where energy consumption and waiting time are considered.
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