• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.403-410
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• 2005

Many daily appliances for examples copiers, printers and ATMs contain the media transport system (MTS) and the slippage between the medium in the MTS deteriorates the performance quality of the whole system. The slippage of the medium in the MTS is affected by many parameters including the friction coefficient between the feeding rollers and the medium, the velocity of the feeding rollers, and the normal force exerted on the medium by feeding rollers. This paper focuses on the effect of the normal force on the slippage while the medium is being fed. For this purpose, we developed a two-dimensional simulation model for a paper feeding system. Using the simulation model, we calculated the slippage of the paper for different normal forces. We have also constructed a testbed of the paper feeding system to verify the simulation results. Experimental results are compared with the simulation results.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.5-13
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• 2014

Number of components and payload systems installed in satellites were found to be exposed to various disturbance sources such as the reaction wheel assembly, the control moment gyro, coolers, and others. A micro-level of vibration can introduce jitter problems into an optical payload system and cause significant degradation of the image quality. Moreover, the prediction of on-orbit vibration effects on the performance of optical payloads during the development process is always important. However, analyzing interactions between subsystems and predicting the vibration level of the payloads is extremely difficult. Therefore, this paper describes the analytical and experimental approach to microvibration effects on satellite optical payload performance with integrated jitter analysis frame-work, microvibration emulator and satellite structure testbed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3865-3883
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• 2016

Infrastructure as a Service (IaaS) encapsulates computer hardware into a large amount of virtual and manageable instances mainly in the form of virtual machine (VM), and provides rental service for users. Currently, VM anomaly incidents occasionally occur, which leads to performance issues and even downtime. This paper aims at detecting anomalous VMs based on performance metrics data of VMs. Due to the dynamic nature and increasing scale of IaaS, detecting anomalous VMs from voluminous correlated and non-Gaussian monitored performance data is a challenging task. This paper designs an anomaly detection framework to solve this challenge. First, it collects 53 performance metrics to reflect the running state of each VM. The collected performance metrics are testified not to follow the Gaussian distribution. Then, it employs independent components analysis (ICA) instead of principal component analysis (PCA) to extract independent components from collected non-Gaussian performance metric data. For anomaly detection, it employs multi-class Bayesian classification to determine the current state of each VM. To evaluate the performance of the designed detection framework, four types of anomalies are separately or jointly injected into randomly selected VMs in a campus-wide testbed. The experimental results show that ICA-based detection mechanism outperforms PCA-based and LDA-based detection mechanisms in terms of sensitivity and specificity.

• Advances in robotics research
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• 제2권2호
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• pp.113-127
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• 2018

Robotics and automation are rapidly growing in the industries replacing human labor. The idea of robots replacing humans is positively influencing the business thereby increasing its scope of research. This paper discusses the development of an experimental platform controlled by a robotic arm through Robot Operating System (ROS). ROS is an open source platform over an existing operating system providing various types of robots with advanced capabilities from an operating system to low-level control. We aim in this work to control a 7-DOF manipulator arm (Robai Cyton Gamma 300) equipped with an external vision camera system through ROS and demonstrate the task of balancing a ball on a plate-type end effector. In order to perform feedback control of the balancing task, the ball is designed to be tracked using a camera (Sony PlayStation Eye) through a tracking algorithm written in C++ using OpenCV libraries. The joint actuators of the robot are servo motors (Dynamixel) and these motors are directly controlled through a low-level control algorithm. To simplify the control, the system is modeled such that the plate has two-axis linearized motion. The developed system along with the proposed approaches could be used for more complicated tasks requiring more number of joint control as well as for a testbed for students to learn ROS with control theories in robotics.

• 한국통신학회논문지
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• 제33권8B호
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• pp.699-706
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• 2008

본 논문에서는 다양한 망 환경에서 SCTP 및 TCP 프로토콜의 전송처리율(throughput) 성능을 비교 분석한다. 실험을 위해 리눅스 테스트베드를 구축하고 성능측정 변수로써 MSS(Maximum Segment Size), 전송지연, 패킷 손실률을 고려하였다. 또한, SCTP 세션의 스트림(stream) 수가 성능에 미치는 영향을 분석하였다. 실험 결과, 동일한 망 환경에서 SCTP는 TCP에 비해 $20%{\sim}50%$ 정도의 높은 처리율을 제공하는데 이는 SCTP의 고유특성인 청크번들링(chunk bundling), 2 MTU로 시작하는 혼잡윈도우, SACK 기반 오류제어 등에서 기인한다. 한편, 패킷 손실이 존재하는 망에서 SCTP는 멀티스트리밍(multi-streaming) 전송을 통해 HoLB(Head-of-Line Blocking) 현상을 효과적으로 방지할 수 있음을 확인하였다.

• 제어로봇시스템학회논문지
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• 제17권2호
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• pp.176-182
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• 2011

Industrial network, often referred to as fieldbus, becomes an indispensable component for intelligent manufacturing systems. Thus, in order to satisfy the real-time requirements of field devices such as sensors, actuators, and controllers, numerous fieldbus protocols have been developed. But, the application of fieldbus has been limited due to the high cost of hardware and the difficulty in interfacing with multi-vendor products. As an alternative to fieldbus, the Ethernet (IEEE 802.3) technology is being adapted to the industrial environment. However, the crucial technical obstacle of Ethernet is its non-deterministic behavior that cannot satisfy the real-time requirements. Recently, the EtherCAT protocol becomes a very promising alternative for real-time industrial application due to the elimination of uncertainties in Ethernet. This paper focuses on the implementation of the IEC 61800 based real-time EtherCAT network for multi-axis smart driver. To demonstrate the feasibility of the implemented EtherCAT slave module, its synchronization performance is evaluated on the experimental EtherCAT testbed with a single axis smart driver.

• 제어로봇시스템학회논문지
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• 제16권10호
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• pp.1018-1023
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• 2010

The CAN (Controller Area Network) system is the most dominant protocol for in-vehicle networking system because it provides bounded transmission delay among ECUs (Electronic Control Units) at data rates between 125Kbps and 1Mbps. And, many automotive companies have chosen the CAN protocol for their in-vehicle networking system such as chassis network system because of its excellent communication characteristics. However, the increasing number of ECUs and the need for more intelligent functions such as ADASs (Advanced Driver Assistance Systems) or IVISs (In-Vehicle Information Systems) require a network with more network capacity and the real-time QoS (Quality-of-Service). As one approach to enhancing the network capacity of a CAN system, this paper introduces a CAN system with dual communication channel. And, this paper presents a distributed message allocation method that allocates messages to the more appropriate channel using forecast traffic of each channel. Finally, an experimental testbed using commercial off-the-shelf microcontrollers with two CAN protocol controllers was used to demonstrate the feasibility of the CAN system with dual communication channel using the distributed message allocation method.

• 융합신호처리학회논문지
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• 제10권1호
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• pp.66-71
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• 2009

3GPP에서는 넓은 서비스 영역과 높은 이동성의 장점을 가지는 3G 이동통신과 높은 데이터 전송률의 장점을 가지는 WLAN간 인터워킹 시스템에 대한 표준화 및 기술 개발이 진행되고 있다. 3GPP와 WLAN 이종망간의 서비스 연속성을 지원하기 위해서는 seamless handover를 지원해야하며 이를 위해서는 핸드오버시 발생하는 지연을 최소화해야 한다. 본 논문에서는 행드오버 과정에서 발생하는 지연 시간의 많은 부분을 차지하는 인증 메커니즘을 실제 USIM 기반의 인증 테스트베드에 구현하여 분석하였다. EAP-AKA 완전 인증 방법과 빠른 재인증 방법에 대해 단말과 AAA 서버에서 발생하는 지연 시간을 구체적으로 분석하였고, 실험 결과 빠른 재인증 방법이 인증에 소요되는 시간을 48.6% 단축시킬 수 있는 것으로 측정되었다.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.39-47
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• 2010

As vehicles become intelligent for convenience and safety of drivers, in-vehicle networking (IVN) systems are essential components of intelligent vehicles. Recently, the chassis networking system which require increased network capacity and real-time capability is being developed to expand the application area of IVN systems. Also, FlexRay has been developed for the chassis networking system. However, FlexRay needs a complex scheduling method of static segment, which is a barrier for implementing the chassis networking system. Especially, if we want to migrate from CAN network to FlexRay network using CAN message database that was well constructed for the chassis networking system by automotive vendors, a novel scheduling method is necessary to be able to reduce design complexity. This paper presents a node-based scheduling method for FlexRay network system. And, in order to demonstrate the method's feasibility, its performance is evaluated through an experimental testbed.

• 로봇학회논문지
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• 제9권1호
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• pp.11-19
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• 2014

In this paper, an external torque estimation problem in one-degree-of-freedom (1-DOF) flexible-joint robot equipped with a joint-torque sensor is revisited. Since a sensor torque from the joint-torque sensor is distorted by two dynamics having a spring connection, i.e., motor dynamics and link dynamics of a flexible-joint robot, a model-based estimation, rather than a simple linear spring model, should be required to extract external torques accurately. In this paper, an external torque estimation algorithm for a 1-DOF flexible-joint robot is proposed. This algorithm estimates both an actuating motor torque from the motor dynamics and an external link torque from the link dynamics simultaneously by utilizing the flexible-joint robot model and the Kalman filter estimation based on random-walk model. The basic structure of the proposed algorithm is explained, and the performance is investigated through a custom-designed experimental testbed for a vertical situation under gravity.