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2 족 로봇을 위한 선형 역진자 모델 기반의 토크 효율적인 걸음새 생성
신혁기,김병국 제어로봇시스템학회 2009 제어로봇시스템학회 국내학술대회 논문집 Vol.2009 No.9
This paper deals with walking reference trajectory generation techniques that is a key problem for stable locomotion of biped robots. In most studies based on the Linear Inverted Pendulum Model (LIPM) that widely employed in the full actuated-biped robot walk, the Zero-Moment-Point (ZMP) reference during a single-support phase is kept fixed in the center of the sole of the supporting foot. This approach makes the robot walk with the most stable condition but lacks naturalness and efficiency, in that, the ZMP in the human walk moves on the foot contact area. This paper propose a torque-efficient reference trajectory generation algorithm that ZMP references which move on the stable region in contact polygon, to minimize the input torques for all joints of a 12 DOF biped robot. Simulation results indicate that the variable ZMP references result in more torque-efficient gait.
2족 보행 로봇을 위한 허용 ZMP (Zero Moment Point) 영역의 활용을 통한 에너지 효율적인 기준 보행 궤적 생성
신혁기(Hyeok-Ki Shin),김병국(Byung Kook Kim) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.10
An energy-efficient reference walking trajectory generation algorithm is suggested utilizing allowable ZMP (Zero- Moment-Point) region, which maxmizes the energy efficiency for cyclic gaits, based on three-dimensional LIPM (Linear Inverted Pendulum Model) for biped robots. As observed in natural human walking, variable ZMP manipulation is suggested, in which ZMP moves within the allowable region to reduce the joint stress (i.e., rapid acceleration and deceleration of body), and hence to reduce the consumed energy. In addition, opimization of footstep planning is conducted to decide the optimal step-length and body height for a given forward mean velocity to minimize a suitable energy performance - amount of energy required to carry a unit weight a unit distance. In this planning, in order to ensure physically realizable walking trajectory, we also considered geometrical constraints, ZMP stability condition, friction constraint, and yawing moment constraint. Simulations are performed with a 12-DOF 3D biped robot model to verify the effectiveness of the proposed method.
중간자 PLC를 이용한 CPS 은닉형 공격 실험환경 구축 방안
장엽,이우묘,신혁기,김신규 한국정보보호학회 2018 정보보호학회논문지 Vol.28 No.1
Cyber-Physical System (CPS) is a system in which a physical system and a cyber system are strongly integrated. In orderto operate the target physical system stably, the CPS constantly monitors the physical system through the sensor andperforms control using the actuator according to the current state. If a malicious attacker performs a forgery attack on themeasured values of the sensors in order to conceal their attacks, the cyber system operated based on the collected data cannot recognize the current operation status of the physical system. This causes the delay of the response of the automationsystem and the operator, and then more damage will occur. To protect the CPS from increasingly sophisticated and targetedattacks, countermeasures must be developed that can detect stealthy deception attacks. However, in the CPS environmentcomposed of various heterogeneous devices, the process of analyzing and demonstrating the vulnerability to actual fielddevices requires a lot of time. Therefore, in this study, we propose a method of constructing the experiment environment ofthe PLCitM (PLC in the middle) which can verify the performance of the techniques to detect the CPS stealthy deceptionattack and present the experimental results. 사이버 물리 시스템(CPS: Cyber-Physical System)은 물리시스템과 사이버시스템이 통합되어 운영되는 시스템을 말한다. CPS는 대상 물리시스템을 안정적으로 운영하기 위해 다수의 센서를 이용하여 끊임없이 물리 대상을모니터링하고 현재 상태에 따라 액추에이터 제어를 수행한다. 만약 악의적인 공격자가 자신들의 공격을 은닉하기 위해서 센서들의 측정값을 대상으로 위변조 공격을 수행한다면, 수집된 데이터에 기반하여 운영되는 사이버시스템은현재 물리시스템의 운영 현황을 확인할 수 없게 된다. 이는 자동화 시스템 및 운전원의 대응을 지연시켜 더욱 큰 피해가 발생하게 된다. 점차 정교해지는 타겟형 공격들로부터 CPS를 안전하게 보호하기 위해서는 센서 및 측정값을대상으로 수행되는 은닉형 공격을 탐지할 수 있는 대응기술을 개발해야 한다. 그러나 다양한 이기종 장치들이 존재하는 CPS에서 실제 현장장치들을 대상으로 취약점을 분석하고 실증하는 과정은 많은 시간을 필요로 한다. 따라서본 연구에서는 CPS 은닉형 공격 탐지 기술의 성능 검증에 활용 가능한 중간자 PLC 실험환경 구축 방안을 제안하고 그 실험결과를 제시한다.
코팅 방식의 차이에 따른 고강도 마그네슘 합금 압출 금형의 특성 분석
김대하(D. H. Kim),주준식(J. S. Joo),이수영(S. Y. Lee),김상호(S. H. Kim),신혁기(H. G Shin) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
When executing extrusion of high strength magnesium alloy, it is done using various coating methods in order to restrain frictional force arises high temperature and high pressure. For extrusion molding, a coating method which produces a low coefficient of friction and reasonably a high surface hardness should be used. Nitriding is the most frequently using method for extrusion molding, but it also faces many limitations. Thus development of a new method is necessary to increase productivity and to produce high strength extrusion products. This study conducted a comparison analysis between the molds produced by CrAIN coating using PACVD method and that of nitriding. An abrasion test was conducted in order to analyze the difference in a coefficient of friction of the two coating methods during a rectilinear motion, and the hardness of the coated surface was analyzed. Also, to see whether the coating layer was evenly formed, the thickness of the layer was measured using SEM. To evaluate the productivity of extrusion of the two methods, a 60mm X 5mm sectional rectangular billets were extruded and analyzed the intensity of illumination of its surface.