Whole-body Control Based Lifting Assistance Simulation for Exoskeletons

Jeonguk Kang,Donghyun Kim,Kyung-Soo Kim,Hyun-Joon Chung,Kwang-Woo Jeon 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.6

Exoskeletons can help humans in a variety of ways in performing tasks. In particular, during the lifting operation, a human places a great burden on the knee or waist joint, and the exoskeleton can reduce the risks of this task. However, due to the weight of the exoskeleton itself and the movement of the overall center of gravity, balance ability and efficiency may decrease. Therefore, an appropriate assistance torque distribution strategy is required to achieve high performance with the exoskeleton. In order to solve the aforementioned problem, we propose an assistance method based on whole-body control. The proposed algorithm is meaningful because it is different from other simple model-based controllers. The controller fully utilize the dynamics to achieve a high performance. In addition, by adding a straight leg cost term, the singularity problem in the fully extended configuration was solved. This method finds the optimal solution that satisfies various constraints and minimizes the objective functions. Each objective is composed of a balancing-related term that minimizes the variation in the center of gravity, a term that supports the weight of the human and exoskeleton, a term that solves the singularity problem and a term related to efficiency. In this paper, first, a motion capture experiment is performed to analyze a human’s lifting motion. Through this experiment, the trajectory of each joint angle is obtained. With PD (proportional–derivative) feedback from the joint trajectories, the exoskeleton generates human torque in the simulation and implements a lifting operation. Second, a simulation is performed with the proposed controller. As a result, it is confirmed that the proposed method reduces the amount of human joint torque and increases stability and efficiency.

A Study on the Electrochemical Characteristics by Ag and Si02 Nano-Particle Additives on Si Anode Materials for Lithium lon Batteries

JeongUk LEE,SeokHwi HAN,HyeonSeok LEE 국제과학영재학회 2016 APEC Youth Scientist Journal Vol.8 No.1

In modern society, the core goal of multiple electronic devices is miniaturization and lightening. Therefore, built-in batteries have to be built with higher capacities in smaller spaces. Nowadays, researchers around the world are studying how to make secondary batteries that can be charged and discharged without replacement in order to improve their performance. The most promising research centers around lithium-ion battery technology. Anode materials such as Carbon and Silicon are currently used in lithium ion batteries and have drawn the attention offorward thinking scientists due to their high capacity properties. However, silicon has a volume problem during the charge-discharge process; Silicon can expand up to four times its original size and destroy the structure of the electrodes around it. Therefore, it currently cannot be commercialized. We created an anode electrode by coting Si powder with various materials. The substance used to make the anode electrode increased the conductivity of Ag and helped control the volume change by adding NP-SiO2 (SiO2nano-particles) and HF. We analyzed our sample with STEM (Scanning Transmission Electron Microscope), XPS (X-ray Photoelectron Spectroscopy), XRD (X-ray Diffraction) and made a coin cell with to confirm the electrochemical performance of the coin cell. As a result, our sample had higher rates of conductivity (better than existing Si anode materials) and made many charge/discharge cycles during the performance test.

Third quadrant Nyquist point for the relay feedback autotuning of PI controllers

Jeonguk Byeon,이지태,Jin-Su Kim,Su Whan Sung,Won Ryoo 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.2

The original relay feedback autotuning method of Astrom and Hagglund [1] is based on the Nyquist point at the phase angle of −π (the critical frequency). Recently, Friman and Waller [8] showed that the critical frequency is too high to tune PI controllers and proposed an autotuning method that finds a Nyquist point at the third quadrant through the two-channel relay. Here, the method to find Nyquist points in the third quadrant is revisited and adaptive relay feedback method which can be applied to noisy processes is proposed. It is shown that the bandwidths of PI control systems and the first-order plus time delay model identifications support the Nyquist point at the third quadrant. Nyquist points at the third quadrant can be obtained by introducing a filter and hysteresis to the relay feedback loop. However, the filter time constant and the size of hysteresis should be adjusted iteratively because their phase shifts are dependent on the resulting relay oscillation frequency. Simulations show that this adaptive relay feedback method finds a given Nyquist point at the third quadrant accurately under noisy environments and provides excellent PI control systems.

Third Quadrant Nyquist Point for the Autotuning of PI Controllers

Jeonguk Byeon,Jin-Su Kim,Daewoong Chun,Su Whan Sung,Jietae Lee 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

The original relay autotuning method of Astrom and Hagglund [1] is based on the Nyquist point at the phaseangle of ??? (the critical frequency). Recently Friman and Waller [8] have shown that the critical frequency is too high for PI controllers and proposed an autotuning method that finds a Nyquist point at the third quadrant through thetwo-channel relay and tunes PI/PID controllers. Here, we provide other reasons that Nyquist points at the third quadrantare better to tune PI controllers. In addition, methods to identify Nyquist points at the third quadrant which can be applied to noisy processes and to tune PI controllers are proposed.

사용자의 명시적 피드백 적용을 통한 소셜 추천시스템 내 개인화 증진

홍정욱(Jeonguk Hong),전계원(Gyewon Jeon),이상원(Sangwon Lee) 대한인간공학회 2023 대한인간공학회 학술대회논문집 Vol.2023 No.5

내부 네트워크에서 알려지지 않은 피싱사이트 탐지방안

박정욱(Jeonguk Park),조기환(Gihwan Cho) 한국정보보호학회 2015 정보보호학회논문지 Vol.25 No.2

피싱 공격이 지속적이고 다양하게 증가하고 있지만 대응방안은 아직도 공격을 식별한 이후에 방어하는 형태에 머무르고 있다. 공격 이전에 HTTP의 Referer 헤더필드를 이용한 피싱사이트 탐지방안이 제안 되었으나, 피싱의 표적이 될 사이트 마다 개별적인 트래픽 수집 시스템을 설치해야하는 한계점이 존재한다. 본 논문은 내부 네트워크에서 기존에 알려져 있지 않은 피싱사이트에 접속하는 것을 탐지하는 방안을 제안한다. 사용자가 피싱사이트에 접속할 때 발생하는 트래픽을 HTTP 프로토콜의 특성과 피싱사이트 특성을 바탕으로 전처리를 수행한다. 피싱으로 의심되는 사이트는 컨텐츠를 분석하는 피싱사이트 판단단계를 통해 탐지된다. 제안된 탐지방안은 100개의 피싱 URL과 100개의 정상 URL을 대상으로 두 가지 형태의 실험으로 검증하였다. 실험결과 피싱 URL의 탐지율은 66%, 정상 URL에 대한 오탐율 0%로 나타났으며, 이는 기존에 제안된 탐지방안에 비해 알려지지 않은 피싱사이트를 탐지하는데 높은 탐지율을 보인다. While various phishing attacks are getting to be increased in constant, their response methods still stay on the stage of responding after identifying an attack. To detect a phishing site ahead of an attack, a method has been suggested with utilizing the Referer header field of HTTP. However, it has a limitation to implement a traffic gathering system for each of prospective target hosts. This paper presents a unknown phishing site detection method in the Interior network environment. Whenever a user try to connect a phishing site, its traffic is pre-processed with considering of the characteristics of HTTP protocol and phishing site. The phishing site detection phase detects a suspicious site under phishing with analysing HTTP content. To validate the proposed method, some evaluations were conducted with 100 phishing URLs along with 100 normal URLs. The experimental results show that our method achieves higher phishing site detection rate than that of existing detection methods, as 66% detection rate for the phishing URLs, and 0% false negative rate for the normal URLs.

저마찰 DLC 코팅 밸브리프터 개발

안정욱(JeongUk Ahn),안승균(SeongGyun Ahn),여인웅(InWoong Lyo),김형익(HyeongIk Kim),김웅(Woong Kim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5

We have developed a well designed sputter DLC coating on valve lifter, which has reduced the mechanical friction by 40% and improved the fuel efficiency by 0.8%. This paper is focusing on mutual correlation between friction characteristic and the microstructure of DLC such as hydrogen concentration, sp3/sp2 ratio and I(D)/I(G).

컴퓨터과학 및 교육 2 : 제주 올레차를 위한 어플리케이션 개발

고정욱 ( Jeonguk Ko ),고혜리 ( Hyeri Ko ),박소정 ( Sojung Park ),조정원 ( Jungwon Cho ) 한국컴퓨터교육학회 2011 한국컴퓨터교육학회 학술발표대회논문집 Vol.15 No.2

본 논문에서는 제주의 청정 이미지에 부합하고, 제주산 감태로부터 추출한 후코이단이라는 기능성 물질을 알리기 위해 개발하고 있는 기능성 차 음료인 ``올레차``를 홍보하면서 동시에 관련 정보를 제공하는 스마트폰 어플리케이션을 기획 및 개발하였다. 기존의 어플리케이션은 정보제공에만 그 목적을 두어 사용자들이 직접 정보를 교류할 방법은 따로 블로그 포스팅을 하거나 입소문을 이용할 수밖에 없다는 제한점이 있었다. 본 논문에서는 이를 개선하며, 정보를 제공함과 동시에 사용자들의 정보교류를 위한 대화공간을 제공하는 등의 제주물산업을 위한 상품 홍보 어플리케이션을 개발하였다.

클러스터 로켓엔진 포고 안정도 예측을 위한 분기관 해석

유정욱(JeongUk Yoo),윤남경(NamKyung Yoon),이시훈(SiHun Lee),신상준(SangJoon Shin) 한국유체기계학회 2020 유체기계 연구개발 발표회 논문집 Vol.2020 No.8

개인형 이동수단 안전성 향상을 위한 음성 인터페이스 제안: 전동킥보드를 중심으로

홍정욱(Jeonguk Hong),이상원(Sangwon Lee) 한국HCI학회 2022 한국HCI학회 학술대회 Vol.2022 No.2

국내 공유 모빌리티 시장의 성장은 퍼스널 모빌리티를 중심으로 가속화되고 있다. 그 중에서도 공유 전동킥보드는 퍼스널 모빌리티에서 주를 이루며, 가장 보편적으로 이용되고 있는 만큼 안전사고도 급증하고 있다. 공유 전동킥보드 사용자 및 보행자의 안전성 개선에 대한 연구는 아직 부족한 상태다. 이에 본 연구에서는 전동킥보드 인터페이스 측면에서 사용자의 안전을 위협하는 요인을 체계적으로 분석하고, 각 요인 별 안전성 향상에 초점을 맞춘 음성 인터페이스에 대해 제안한다. 본 연구는 전동킥보드 안전사고 위험 요인을 분석하고, 이를 고려하여 사용자의 상황에 필요한 정보를 음성 인터페이스가 제공함으로써 유용한 정보를 시각적인 측면에서 지원하는 기존 인터페이스들과는 차별화하였다. 본 연구의 인터페이스적 제안은 사용자 및 비사용자 모두의 실질적인 안전 수준 향상과 긍정적인 이동 경험을 제공에 기여함으로써 모빌리티 혁신을 경험할 수 있도록 하여 공유 모빌리티 서비스 고도화에 도움이 될 것으로 기대된다.