• The Transactions of the Korean Institute of Power Electronics
• /
• v.17 no.3
• /
• pp.266-273
• /
• 2012

In this paper, the new open fault detection and tolerant operation method for 3 phase PWM rectifier is proposed. When open fault occurred on the inverter switches of 3 Phase PWM rectifier, the DC link voltage ripple is increased because the input current of the faulty phase is distorted. In this case, the quality of electric power would decrease, and the life time of DC link capacitor is decreased. The open fault is detected by a simple MRAS(Model Reference Adaptive System) without additional hardware sensors, and the tolerant operation carried out by turning on the opposite switch of the faulty switch without any redundancy. By the proposed method, the faulty phase input current can be controlled, so that 3-phase input current is balanced relatively under the faulty condition and the voltage ripple of DC link output is reduced. The validity of the proposed technique is proved on the 6kW 3-phase PWM rectifier system by simulation and experiment.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.3
• /
• pp.25-31
• /
• 2015

In this paper, we propose PEP based on cross-layer and network coding in digital video broadcasting-return channel via satellite (DVB-RCS) networks. In particular, we propose not only a scheme of cross-layer information exchange for interaction between TCP and the resource allocation (RA) scheme in the link layer but also a tuning algorithm for the TCP contention window (CWND) by using information on the RA in the link layer and the redundancy rate for network-coded packets. The simulation results show that TCP CWND can be adjusted by RA information in the proposed protocol. Furthermore, through the transmission of network-coded packets and the proposed CWND tuning algorithm, TCP throughput is enhanced in lossy environment due to user mobility without the unnecessary resource overhead.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.1
• /
• pp.47-52
• /
• 2000

Redundant programmable logic controllers are used in practice with the aim of achieving a higher degree of availability or fault tolerance. Redundancy system is fault tolerant programmable logic controller for machine and plant. It is event synchronized master-standby system with a 2 channel(1-out-of-2) structure. A data link connects line the master to the standby controller.Fault tolerant systems should always be used when it is necessary to keep the probability of a total control system failure to a minimum. The objective of using high availability programmable logic controller is a reduction of losses of fault tolerant system are quickly compensated by the avoidance of loss of production.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.7
• /
• pp.144-153
• /
• 1997

The inverse kinematics problem of a reclaimer which excavates and transports raw materials in a raw yard is investigated. Because of the geometric feature of the equipment in which scooping buckets are attached around the rotating disk, kinematic redundancy occurs in determining joint variable. Link coordinates are introduced following the Denavit-Hartenbery representation. For a given excavation point the forward kinematics yields 3 equations, however the number of involved joint variables in the equations is four. It is shown that the rotating disk at the end of the boom provides an extra passive degree of freedom. Two approaches are investigated in obtaining inverse kinematics solutions. The first method pre-assigns the height of excavation point which can be determined through path planning. A closed form solution is obtained for the first approach. The second method exploits the orthogonality between the normal vector at the excavation point and the z axis of the end-effector coordinate system. The geometry near the reclaiming point has been approximated as a plane, and the plane equation has been obtained by the least square method considering 8 adjacent points near the point. A closed form solution is not found for the second approach, however a linear approximate solution is provided.

• Journal of the Optical Society of Korea
• /
• v.20 no.6
• /
• pp.678-685
• /
• 2016

The standard high-availability seamless redundancy (HSR) protocol utilizes duplicated frame copies of each sent frame for zero fail over time. This means that even in cases of a node or link failure, the destination node will receive at least one copy of the sent frame, resulting in no network downtime. However, the standard HSR is mostly based on the electrical signal connection inside the node, which leads to the production of considerable latency at each node due to frame processing. Therefore, in a large scale HSR ring network, the accumulated latencies become significant and can often restrict the mission-critical real-time application of HSR. In this paper, we present a novel design for optical HSR (OHSR) that uses beam splitting/combining techniques. The proposed OHSR passes the frames directly to adjacent nodes without frame processing at each node, thereby theoretically generating no latency in any node. Various simulations for network samples, made to validate the OHSR design and its performance, show that the OHSR outperforms the standard HSR.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.7
• /
• pp.572-580
• /
• 2013

IEEE 802.15.4e is a prospective standard for low latency control application in industries. This paper proposes a framework to evaluate the closed loop IEEE 802.15.4e based WNCS performance. The framework consists of two models: closed loop control system model and network model. The network model focuses on the PHY parameters of wireless link and takes the channel parameters into consideration. The PHY model combining with MAC model gives the control system model the probability of packet loss in a super-frame. In addition, redundancy mechanism is considered in IEEE 802.15.4e to reduce to data frame loss probability. The simulation is implemented in Matlab, PHY model takes the channel parameters from empirical results. Hence our evaluation gives insight into behavior of WNCS in different environments and it provides us a tool to design wireless network to achieve a good performance for control system.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.9
• /
• pp.26-37
• /
• 2016

The core technologies of the current transport network are OAM and protection switching to meet the sub-50ms protection switching time via a path redundancy when a link or node failure occurs. The transport networks owned by public network operators, central/local governments, and major enterprises are individually configured and managed with service resiliency in each own protected sub-network. When such networks are cascaded, it is also important to provide a node resiliency between two protected sub-networks. However, the linear protection switching in packet transport networks, such as MPLS-TP and Carrier Ethernet, does not define a solution of dual node interconnection. Although Ethernet ring protection switching covers the dual node interconnection scheme, a large amount of duplicated data frames may be flooded when a failure occurs on an adjacent (sub) ring. In this paper, we suggest a dual node interconnection scheme with linear protection switching technology in multiple protected sub-networks. And we investigate how various protected sub-network combinations with a proposed linear or ring protection process impact the service resiliency of multiple protected sub-networks through extensive experiments on link and interconnected node failures.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.11 no.4
• /
• pp.331-339
• /
• 2018

The IEEE 1588, commonly known as a precision time protocol (PTP), is a standard for precise clock synchronization that maintains networked measurements and control systems. The best master clock (BMC) algorithm is currently used to establish the master-slave hierarchy for PTP. The BMC allows a slave clock to automatically take over the duties of the master when the slave is disconnected due to a link failure and loses its synchronization; the slave clock depends on a timer to compensate for the failure of the master. However, the BMC algorithm does not provide a fast recovery mechanism in the case of a master failure. In this paper, we propose a technique that combines the IEEE 1588 with network bonding to provide a faster recovery mechanism in the case of a master failure. This technique is implemented by utilizing a pre-existing library PTP daemon (Ptpd) in Linux system, with a specific profile of the IEEE 1588 and it's controlled through bonding modes. Network bonding is a process of combining or joining two or more network interfaces together into a single interface. Network bonding offers performance improvements and redundancy. If one link fails, the other link will work immediately. It can be used in situations where fault tolerance, redundancy, or load balancing networks are needed. The results show combining IEEE 1588 with network bonding enables an incredible shorter recovery time than simply just relying on the IEEE 1588 recovery method alone.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.1
• /
• pp.61-69
• /
• 2005

The topology of NPC inverter coupled with the large number of devices used increases the probability of device failure. It's necessary to develop an optimal remedial strategy which can be used to continue the application when fault occurs. The fault tolerance is obtained by the use of the proposed method. The proposed method utilizes that the one phase load with the failed power device could be connected to the center-tap of the DC-link capacitor in order to dc-link voltage with balance and the sinusoidal phase current with constant amplitude under the single power device fault condition. The strategy described in this paper is expected to provide an economic alternative to more expensive redundancy techniques.

• The Journal of Korea Robotics Society
• /
• v.16 no.2
• /
• pp.147-154
• /
• 2021

One of the most challenging issues when robots interact with the environment is to establish contact quickly and avoid high impact force at the same time. The proposed method implements the passive suspension system using the redundancy of the torque-controlled robot. Instead of utilizing the actual mechanical compliance, the distal joints near the end-effector are controlled to act as a virtual spring-damper system with low feedback gains. The proximal joints are precisely controlled to push the mid-link, which is defined as the boundary link between the proximal and distal joints, towards the environment with high feedback gains. Compared to the active compliance methods, the contact force measurements or estimates are not required for contact establishment and the control time delay problems do not occur correspondingly. The proposed method was applied to the landing foot control of the 12-DoF biped robot DYROS-RED in the simulations. In the results, the impact force during landing was significantly reduced at the same collision speed.