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가려진 동적 장애물을 고려한 이동로봇의 안전한 주행기술개발
김석규(Seokgyu Kim),정우진(Woojin Chung) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.2
In this paper, we present one approach to achieve safe navigation in indoor dynamic environment. So far, there have been various useful collision avoidance algorithms and path planning schemes. However, those algorithms have a fundamental limitation that the robot can avoid only "visible" obstacles. In real environment, it is not possible to detect all the dynamic obstacles around the robot. There exist a lot of "occluded" regions due to the limitation of field of view. In order to avoid possible collisions, it is desirable to consider visibility information. Then, a robot can reduce the speed or modify a path. This paper proposes a safe navigation scheme to reduce the risk of collision due to unexpected dynamic obstacles. The robot"s motion is controlled according to a hybrid control scheme. The possibility of collision is dually reflected to a path planning and a speed control. The proposed scheme clearly indicates the structural procedure on how to model and to exploit the risk of navigation. The proposed scheme is experimentally tested in a real office building. The presented result shows that the robot moves along the safe path to obtain sufficient field of view, while appropriate speed control is carried out.
양자점을 이용한 플래시 메모리 기반 뉴로모픽 소자 연구
최지수(Jisoo Choi),양정목(Jeongmok Yang),김예은(Yeeun Kim),강다현(Dahyun Kang),박찬규(Changyu Park),정소연(Soyeon Jung),김석규(Seokgyu Kim),김용덕(Yongduk Kim),손병희(Byunghee Son),장문규(Moongyu Jang) 한국물리학회 2022 새물리 Vol.72 No.10
뇌에서는 외부 자극에 의해 뉴런들의 연관성이 높아지면 시냅스를 통하여 연결 강도가 달라지게 된다. 본 연구에서는 양자점을 사용하여 이러한 시냅스를 구현하는 소자를 제작하고 평탄대 전압을 변화시키며 메모리 효과를 확인하였다. Pt/Cr/Al₂O₃/Quantum Dots/SiO₂/Si 기판의 수직 구조를 가진 소자를 제작하였고, 소자의 동작을 위해 게이트 전극에 전압을 가하였다. 이때, 절연막 손상이 발생하지 않는 적절한 프로그래밍/이레이징 전압 범위 설정이 필요하므로 전류-전압을 측정하여 절연막의 항복 전압을 도출하였다. 이후, 적절한 프로그래밍 전압을 인가하며 정전용량-전압 측정을 진행하였고 이를 통해 양자점의 메모리 효과를 확인하였다. 우리는 소자에 인가하는 전압의 크기와 시간을 변경하며 양자점에 포획되는 전자의 수를 조절하였고, 양자점에 포획된 전자의 수에 따라 평탄화 전압을 변화시켜 여러 단계의 상태를 표현할 수 있었다. 이를 통해 상태가 다양한 강도의 아날로그 형태로 변화하는 시냅스 특성을 표현할 수 있는 가능성을 확인하였다. In the human brain, when the neuron association is increased by an external stimulation, the strength of the connection changes through the synapses. The semiconductor devices emulating these synapses are called neuromorphic devices. In this research, a device acting as a synapse was manufactured using quantum dots (QDs), and the memory effect was confirmed by changing the flatband voltage (VFB) through the injection and depletion of electrons into the QDs. The fabricated device contained a vertical gate stack Pt/Cr/QDs/Al₂O₃/SiO₂/Si substrate, and a current-voltage characteristic was used to determine the breakdown voltage and the select programming voltage within a range that did not affect the oxide. Subsequently, the capacitance-voltage was measured by applying the programming voltage, and the memory effect of QDs was confirmed. The number of electrons stored in QDs were adjusted by changing the voltage and time to the device, and the state of several steps was implemented by varying the VFB depending on the number of electrons stored in QDs. Through the manufactured device, we confirmed that the implementation of a synaptic device was possible with multiple connection strengths.