• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.229-229
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• 2023

강화학습은 에이전트(agent)가 주어진 환경(environment)과의 상호작용을 통해서 상태(state)를 변화시켜가며 최대의 보상(reward)을 얻을 수 있도록 최적의 행동(action)을 학습하는 기계학습법을 의미한다. 최근 알파고와 같은 게임뿐만 아니라 자율주행 자동차, 로봇 제어 등 다양한 분야에서 널리 사용되고 있다. 상수도관망 분야의 경우에도 펌프 운영, 밸브 운영, 센서 최적 위치 선정 등 여러 문제에 적용되었으나, 설계에 강화학습을 적용한 연구는 없었다. 설계의 경우, 관망의 크기가 커짐에 따라 알고리즘의 탐색 공간의 크기가 증가하여 기존의 최적화 알고리즘을 이용하는 것에는 한계가 존재한다. 따라서 본 연구는 강화학습을 이용하여 상수도관망의 구성요소와 환경요인 간의 복잡한 상호작용을 고려하는 설계 방법론을 제안한다. 모델의 에이전트를 딥 강화학습(Deep Reinforcement Learning)으로 구성하여, 상태 및 행동 공간이 커 발생하는 고차원성 문제를 해결하였다. 또한, 해당 모델의 상태 및 보상으로 절점에서의 압력 및 수요량과 설계비용을 고려하여 적절한 수량과 수압의 용수 공급이 가능한 경제적인 관망을 설계하도록 하였다. 모델의 행동은 실제로 공학자가 설계하듯이 절점마다 하나씩 차례대로 다른 절점과의 연결 여부를 결정하는 것으로, 이를 통해 관망의 레이아웃(layout)과 관경을 결정한다. 본 연구에서 제안한 방법론을 규모가 큰 그리드 네트워크에 적용하여 모델을 검증하였으며, 고려해야 할 변수의 개수가 많음에도 불구하고 목적에 부합하는 관망을 설계할 수 있었다. 모델 학습과정 동안 에피소드의 평균 길이와 보상의 크기 등의 변화를 비교하여, 제안한 모델의 학습 능력을 평가 및 보완하였다. 향후 강화학습 모델을 통해 신뢰성(reliability) 또는 탄력성(resilience)과 같은 시스템의 성능까지 고려한 설계가 가능할 것으로 기대한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.280-283
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• 2021

SME(small and medium sized enterprise) 환경의 스마트공장 환경에서는 실제 제조라인에서 동작하는 센서(Sensor) 및 액추에이터(Actuator)와 이를 관리하는 PLC(Programmable Logic Controller), 더불어 그러한 PLC를 제어 및 관리하는 HMI(Human-Machine Interface), 그리고 다시 PLC와 HMI를 관리하는 OT(Operational Technology)서버로 구성되어 있으며, 제어자동화를 담당하는 PLC 및 HMI는 공장운영을 위한 응용시스템인 OT서버 및 현장 자동화를 위한 로봇, 생산설비와의 직접적인 연결을 수행하고 있어서 스마트공장 환경에서 보안 기술의 개발이 중점적으로 필요한 영역이다. 이러한 SME 환경의 스마트공장 보안 내재화를 이루기 위해서는, 스마트공장 SW 및 HW 개발 단계에서 IEC 62443-4-1 Secure Product Development Lifecycle에 따른 프로세스 정립 및 IEC 62443-4-2 Component 보안 요구사항과 IEC 62443-3-3 System 보안 요구사항에 적합한 개발 방법론의 도입이 필요하다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.520-522
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• 2022

Lone Death is increasing as elderly population increases. Lone elderly is vulnerable in society for many reasons. This paper explores digital solution to protect solitary in society. First, sensor and AI care robot can be used to collect digital data and situation check. Second, digital device is checked regularly and visiting is expanded in digital environment. Third, digital emergency security system should be established. Fourth, user education is to be regularly carried out including complementary education.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.433-434
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• 2022

물류 시설에서 사람이 직접 물류를 입출고하는 방식이 일반적이다. 본 연구에서는 물류의 입출고를 인력의 소모 없이 보다 안전하고 효율적으로 하는 것을 전제로 하여 스마트 팩토리 산업에 사용되는 AGV 시스템에 물류 입출고 시스템을 접목하고자 한다. 본 논문은 기존의 인력의 소모와 산업재해 위험이 있는 물류 시설 근로 환경에 AGV를 이용, 인력의 소모를 줄여 물류 입출고 프로세스를 무인화하고자 "AGV 물류 자동화 시스템"을 제안한다. AGV 물류 자동화 시스템은 적외선 센서를 이용해 라인 트레이서를 구현하여 원하는 위치로 AGV를 이동시키고 각종 모터로 물품의 입출고 임무를 수행하도록 한다. 스마트폰의 물류 관리 어플리케이션을 통해 AGV의 제어와 물품의 재고 파악이 가능하도록 하여 물류관리의 효율성과 편의성을 증대시켰다.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.281-282
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• 2023

자율주행 자동차 시장 규모 및 기술이 급속도로 성장하고 있음에도 불구하고, 전문가 교육을 위한 높은 하드웨어 비용 때문에 실제로 이 기술을 실험하기 위한 집단 교육 플랫폼의 필요성이 높아졌다. 이에 따라 우리는 자율주행에 사용되는 센서와 액츄에이터, 그리고 자율주행 알고리즘 학습을 위한 1/5 크기의 하드웨어를 포함한 교육 플랫폼을 설계했다. 이 교육 프로그램은 온라인 강의와 실습으로 구성되며, 각각의 모듈은 로봇 운영체제(ROS)를 활용한 C언어로 개발되었다. 이 교육 플랫폼은 언제 어디서나 접근 가능한 온라인 형식으로 제공되므로, 학생들은 이론과 실습을 통해 자율주행 분야의 전문가로 성장할 수 있는 기회를 얻게 되고 혁신과 경쟁력 강화에 기여할 것으로 기대된다.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.7
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• pp.299-306
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• 2022

In recent, sensors embedded in robots, equipment, and circuits have become common, and research for diagnosing device failures by learning measured sensor data is being actively conducted. This failure diagnosis study is divided into a classification model for predicting failure situations or types and a regression model for numerically predicting failure conditions. In the case of a classification model, it simply checks the presence or absence of a failure or defect (Class), whereas a regression model has a higher learning difficulty because it has to predict one value among countless numbers. So, the reason that regression modeling is more difficult is that there are many irregular situations in which it is difficult to determine one output from a similar input when predicting by matching input and output. Therefore, in this paper, we focus on input and output data with periodicity, analyze the input/output relationship, and secure regularity between input and output data by performing sliding window-based input data patterning. In order to apply the proposed method, in this study, current and temperature data with periodicity were collected from MMC(Modular Multilevel Converter) circuit system and learning was carried out using ANN. As a result of the experiment, it was confirmed that when a window of 2% or more of one cycle was applied, performance of 97% or more of fit could be secured.

• Journal of Adhesion and Interface
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• v.24 no.3
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• pp.95-99
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• 2023

In this study, LiDAR-detectable black materials are synthesized by coating and reduction of titanium dioxide onto plate-type natural mica, which evaluated practical LiDAR verification. In detail, black TiO₂@Mica materials are fabricated by utilizing a sol-gel reaction to coat titanium dioxide onto natural mica, followed by reduction using sodium tetrahydridoborate. Subsequently, Black TiO₂@Mica materials are dispersed in hydrophilic transparent varnish and sprayed onto the glass substrate to assess applicability as paints. As a result, Black TiO₂@Mica-based paints exhibit true blackness (L^*=12.1) and a higher NIR reflectance (30.2 R%). In addition, it was confirmed that as-synthesized Black TiO₂@Mica materials are successfully recognized by a LiDAR sensor. This phenomenon is attributed to Fresnel's reflection law, in which light reflection occurs at the interface between natural mica and titanium dioxide with different refractive indices. In this regard, the findings of the study are expected to contribute to the potential utilization of LiDAR-detectable materials in various fields such as autonomous vehicles, robotics, and drones.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.218-222
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• 2014

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.705-709
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• 2016

Micro-electro-mechanical systems (MEMS) gyroscopes are widely used in various robot applications. However, these conventional gyroscopes need to vibrate the proof mass using a built-in actuator at a fixed resonance frequency to sense the Coriolis force. When a robot is not moving, the meaningless vibration of the gyroscope wastes power. In addition, this continuous vibration makes the sensor vulnerable to external sound waves with a frequency close to the proof-mass resonance frequency. In this paper, a feasibility study of a new type of gyroscope inspired by insect halteres is presented. In dipterous insects, halteres are a biological gyroscope that measures the Coriolis force. Wing muscles and halteres are mechanically linked, and the halteres oscillate simultaneously with wing beats. The vibrating haltere experiences the Coriolis force if the insect is going through a rotational motion. Inspired by this haltere structure, a gyroscope using a thin mast integrated with a robot actuation mechanism is proposed. The mast vibrates only when the robot is moving without requiring a separate actuator. The Coriolis force of the mast can be measured with an accelerometer installed at the tip of the mast. However, the signal from the accelerometer has multiple frequency components and also can be highly corrupted with noise, such that raw data are not meaningful. This paper also presents a suitable signal processing technique using the amplitude modulation method. The feasibility of the proposed haltere-inspired gyroscope is also experimentally evaluated.

• Convergence Security Journal
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• v.17 no.3
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• pp.59-64
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• 2017

Korea is experiencing a rapid increase in the number of elderly living alone accompanying the aging society problem, a nd is making efforts to solve the problem through the policy of 'living alone u-care service'. The purpose of this study is to propose a better u-Care service improvement method by applying new technology to improve the user experience of ucare service for the health and safety of the elderly living alone. First, the improvement of u-Care service for elderly livin g alone by applying IoT technology. It provides remote monitoring service using health information data measured through wearable device, and transmits personal health status to medical institution by using personal device such as smart phone, so that remote medical consultation or telemedicine can be connected in the future. Second, improvement of u-Care service through consideration of emotional stability of elderly living alone as well as simple safety and health care through applica tion of emotional service robot technology.It is expected that it will be able to help independent living of one person's elde rly person in the future by providing caring function service to existing u-care service providing service.