• Journal of the Ergonomics Society of Korea
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• v.7 no.2
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• pp.31-44
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• 1988

If an error occurs in the automatic mode when the advanced teleoperator system performs a task in hostile environment then the automatic mode changes into the manual mode. The operation by the control program and the operation by a human recover the error in the manual mode. The system resumes the automatic mode and continues the given task. It is necessary to improve the manual mode in order to make the best use of a man-robot system, as a part of the human interface technique. Therefore, the error recovery task is performed by combining the operation by the control program representing autonomy of a robot and the operation by a human representing versatility of a human operator effectively in the view point of human factors engineering. The geometric inverse kinematics is used for the calculation of the robot joint values in the operation by the control program. The singularity operation error and the parameter operation error often occur in this procedure. These two operation errors increase the movement time of the robot and the coordinate reading time, during the error recovery task. A singularity algorithm, parameter algorithm and fuzzy control are studied so as to remove the disadvantages of geometric inverse kinematics. And the geometric straight line motion is studied so as to improve the disadvantages of the operation by a human.

• Journal of Information Technology Applications and Management
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• v.11 no.2
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• pp.29-43
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• 2004

As the development of an information technique, gradually, mobile device is going to be miniaturized and operates at high speed. By such the requirements, the devices using a flash memory as a storage media are increasing. The flash memory consumes low power, is a small size, and has a fast access time like the main memory. But the flash memory must erase for recording and the erase cycle is limited. JFFS is a representative filesystem which reflects the characteristics of the flash memory. JFFS to be consisted of LSF structure, writes new data to the flash memory in sequential, which is not related to a file size. Mounting a filesystem or an error recovery is achieved through the sequential approach. Therefore, the mounting delay time is happened according to the file system size. This paper proposes a MJFFS to use a multi-checkpoint information to manage a mass flash file system efficiently. A MJFFS, which improves JFFS, divides a flash memory into the block for suitable to the block device, and stores file information of a checkpoint structure at fixed interval. Therefore mounting and error recovery processing reduce efficiently a number of filesystem access by collecting a smaller checkpoint information than capacity of actual files. A MJFFS will be suitable to a mobile device owing to accomplish fast mounting and error recovery using advantage of log foundation filesystem and overcoming defect of JFFS.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.2
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• pp.98-109
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• 2010

This paper deals with a new method of unmanned aerial vehicle (UAV) recovery when a UAV fails to get a global positioning system (GPS) signal at an unprepared site. The proposed method is based on the simultaneous localization and mapping (SLAM) algorithm. It is a process by which a vehicle can build a map of an unknown environment and simultaneously use this map to determine its position. Extensive research on SLAM algorithms proves that the error in the map reaches a lower limit, which is a function of the error that existed when the first observation was made. For this reason, the proposed method can help an inertial navigation system to prevent its error of divergence with regard to the vehicle position. In other words, it is possible that a UAV can navigate with reasonable positional accuracy in an unknown environment without the aid of GPS. This is the main idea of the present paper. Especially, this paper focuses on path planning that maximizes the discussed ability of a SLAM algorithm. In this work, a SLAM algorithm based on extended Kalman filter is used. For simplicity's sake, a blimp-type of UAV model is discussed and three-dimensional pointed-shape landmarks are considered. Finally, the proposed method is evaluated by a number of simulations.

• The Transactions of the Korea Information Processing Society
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• v.7 no.5
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• pp.1330-1340
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• 2000

Multimedia isn ow applied to various real world areas. In particular, the focus on multimedia system and CSCW(Computer Supported Cooperative Work) has increased. In spite of this current trend, however, the study of fault tolerance for CSCW has not yet fully progressed. We propose EDR_MSCW. It is a system that is suitable for detecting ad recovering software error based on multimedia computer supported cooperative work as DOORAE by using software techniques. DOORAE is a framwork for supporting development on multimedia applications for computer-based collaborative works. When an error occurs, EDR_MCSCW detects an error by using hooking methods in MS-Windows API(Application Program Interface) function. If an error is found, we present a checkpointing and recovery algorithm which has the removal function of the domino-effect for recovering multimedia and CSCW by using stack.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.245-249
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• 2004

In this paper, we have proposed a clock recovery algorithm of Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio(OFDM/QPSK-DMR) system using Band Limited-Pulse Shaping Filter(BL-PSF) and compared the clock phase error variance of OFDM/QPSK-DMR system with that of single carrier DMR system. The OFDM/QPSK-DMR system using windowing method requires training sequence or Cyclic Prefix (CP) to synchronize the clock phase of received signal. But transmit efficient is increased in our proposed DMR system because of no using redundant data such as training sequence or CP. The proposed clock recovery algorithm is simply realized in the OFDM/QPSK-DMR system using BL-PSF. The simulation results confirm that the proposed clock recovery algorithm has the same clock phase error variance performance in a single carrier DR system under Additive White Gaussian Noise(AWGN) environment.

• Journal of Internet Computing and Services
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• v.3 no.5
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• pp.95-106
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• 2002

In current storage system environment, we use disk mirroring or Chained-declustering scheme to improve data availability and reliability. If disk error is occurred when these schemes are used. we need efficient recovery schemes for these situations. In this paper, it is proposed that a recovery method of disk mirroring that guarantees I/O performance similar to normal state during disk failure, Also, we execute performance evaluation for our recovery scheme and existing schemes in various environments. We show through the simulation that our algorithm outperforms the classic schemes in terms of I/O response time.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.74-79
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• 2010

This paper explains the design and implementation of nested session management based the FRA(Fault Recovery Agent). FRA is a system that is suitable for recovering software error for multimedia remote control based on industry safety environment. In this paper, we discuss a method for increasing reliability through organization of nested session.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.44-50
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• 2009

In this study, the relationship between military pilot's spatial ability and unusual attitude recovery was investigate. MRT(Mental Rotation Test) was measured with spatial ability whereas recovery time and error rates were mearsured with respect to 11 unusual attitudes. Eight fighter pilots and eight rear cockpit pilots of F-4E participated in this study. The results showed that MRT response time was significantly correlated with unusual attitude recovery time. The regression equation showed that unusual attitude recovery time was linearly related to MRT response time and could be explained by MRT response time more than 66%. In conclusion, it is recommended that a training is needed to improve the mental rotation ability in a visually restricted environments during maneuvering.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1864-1871
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• 2001

In this paper, new symbol timing recovery algorithm is proposed, which is suitable for the digital communication system with Multi-level PAM signals. In the newly proposed symbol timing recovery algorithm, the timing error function is derived by compensating the several difference values between sampled symbol and neighboring symbol every symbol period with mid samples and decided symbol values. Conventional symbol timing recovery methods did not work well in Multi-level PAM signals, but the newly proposed method can be applied to Multi-level PAM signals as well as QPSK. For the performance analysis, the derived variance of the timing error function and the timing error characteristics of S-curve show that the proposed method has better performance than Gardner method and the modified Gardner method.

• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.615-618
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• 2011

Living cells generate the cell cycle or apoptosis, depending on the course will be repeated. If an error occurs during this period of life in order to maintain the cells in the peripheral cells find the error portion. These cellular functions were applied to the system to simulate the circuit. Circuit implementation of the present study was constructed the redundant structure in order to found the error quickly. Self-repairing of digital systems as an advanced form of fault-tolerance has been increasingly receiving attention according as digital systems have been more and more complex and speed-up especially for urgent systems or those working on extreme environments such as deep sea and outer space. Simulating the process of cell differentiation algorithm was confirmed by the FPGA on the counter circuit. If an error occurs on the circuit where the error was quickly locate and repair. In this paper, we propose a novel self-repair architecture for fast and robust fault-recovery that can easily apply to real, complex digital systems. These Self-Repairing Algorithms make it possible for the application digital systems to be alive even though in very noisy and extreme environments.