• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1136-1144
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• 2010

In this paper, the effects of HARQ feedback error are evaluated in IEEE 802.16m system when the HARQ and ARQ interactions that utilize the HARQ feedback information is used. Also, the HARQ and ARQ interaction scheme considering HARQ feedback errors are proposed. The HARQ and ARQ interaction scheme improve the system throughput by using the HARQ feedback information instead of the ARQ feedback message, which reduce retransmission time. However, errors in the HARQ feedback information generate severe performance degradation. Especially, the local NAK errors between HARQ feedback error critically degrade the performance, because the local NAK errors lead the loss of ARQ blocks. We propose a channel state-based schemes for HARQ and ARQ interactions to mitigate the throughput degradation due to HARQ feedback errors. Simulation results show that the proposed scheme improves the throughput and the delay performance.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.699-701
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• 2004

This paper proposes the algorithm of servo- writing based on feedback error learning neural networks. The controller consists of feedback controller using PID and feedforward controller using gaussian radial basis function network. Because the RBFNs are trained by on-line rule, the controller has adaptation capability. The performance of the proposed controller is compared to that of conventional PID controller. Proposed algorithm shows better performance than PID controller.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.286-294
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• 1998

This paper presents an experimental study on the performance of the active damper device by feedback variables. The damper is a mass-typed active device, which exerts the inertia control force on the building by AC servo motor. The control performance is experimentally analyzed considering the building response and the control force. It is found that the building response is greatly reduced by mass-typed device under the resonant and earthquake loading. Also, the experimental results show that the velocity feedback reduces the building responses with the smallest amount of control force than any other feedback variables.

• Asia pacific journal of information systems
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• v.9 no.2
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• pp.1-17
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• 1999

A feedback echo is a structured restatement of the user's query and informs the user what the system intends to do for the query. This provides backtracking of the user's query so that the user knows how the system has interpreted the query. This study scrutinizes whether the feedback echo, as currently available in the INTELLECT commercial system, can improve the performance of a casual user using a restricted natural language database interface. This study concludes that the particular type of feedback echo available in this commercial system was not effective in terms of overall performance for casual users. It is worth mentioning, however, that the feedback echo was effective for the specific type of error: using wrong conditions for data retrieval.

• International Journal of Control, Automation, and Systems
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• v.6 no.2
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• pp.269-277
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• 2008

This paper proposes a necessary and sufficient condition of convergence in the $L_2$-norm sense for a feedback-based iterative learning control (ILC) system including a multi-input multi-output (MIMO) linear time-invariant (LTI) plant. It is shown that the convergence conditions for a nominal plant and an uncertain plant are equal to the nominal performance condition and the robust performance condition in the feedback control theory, respectively. Moreover, no additional effort is required to design an iterative learning controller because the performance weighting matrix is used as an iterative learning controller. By proving that the least upper bound of the $L_2$-norm of the remaining tracking error is less than that of the initial tracking error, this paper shows that the iterative learning controller combined with the feedback controller is more effective to reduce the tracking error than only the feedback controller. The validity of the proposed method is verified through computer simulations.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.5
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• pp.360-366
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• 1987

The design problem of optimal constant PIDM (proportional-integral-derivative and measurable variable) feedback controller for linear time-invariannt systems is investigated with the time-weighted quadratic performance index. Necessary conditions for an optimality of the controller are derived and an algorithm for computing the optimal feedback gain is presented. It is shown via example that the design mithod using the time-weighted quadratic performance index improves the transient responses of the closed-loop system.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.960-967
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• 2008

This paper shows that design of a robustly stable repetitive control system is equivalent to that of a feedback control system for an uncertain linear time-invariant system satisfying the well-known robust performance condition. Once a feedback controller is designed to satisfy the robust performance condition, the feedback controller and the repetitive controller using the performance weighting function robustly stabilizes the repetitive control system. It is also shown that we can obtain a steady-state tracking error described in a simple form without time-delay element if the robust stability condition is satisfied for the repetitive control system. Moreover, using this result, a sufficient condition is provided, which ensures that the least upper bound of the steady-state tracking error generated by the repetitive control system is less than or equal to the least upper bound of the steady-state tracking error only by the feedback system.

• Journal of Power Electronics
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• v.14 no.1
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• pp.40-47
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• 2014

An average current mode control scheme that consistently offers good dynamic performance for LLC series resonant DC-to-DC converters irrespective of the changes in the operational conditions is presented in this paper. The proposed control scheme employs current feedback from the resonant tank circuit through an integrator-type compensation amplifier to improve the dynamic performance and enhance the noise immunity and reliability of the feedback controller. Design guidelines are provided for both current feedback and voltage feedback compensation. The performance of the new control scheme is demonstrated through an experimental 150 W converter operating with 340 V to 390 V input voltage to provide a 24 V output voltage.

• Journal of information and communication convergence engineering
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• v.9 no.2
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• pp.183-186
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• 2011

In this work, we consider imperfectness of feedback channels in the adaptive transmission scheme which was previously studied with an assumption of error-free feedback channels. New method of mapping the modulation index into the feedback channel symbols and quantifying feedback error over fading channels are proposed. The presented method and results are expected to offer valuable tools for the system designer to efficiently implement adaptive diversity schemes to compensate for the performance degradation due to feedback error.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.4
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• pp.59-68
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• 2015

PURPOSE: The purpose of this study was to determine the comparison of visual and auditory biofeedback during sit-to-stand training in patients with stroke. METHODS: Thirty-five subjects with chronic stroke were divided into three groups: a visual feedback group (12 subjects), an auditory feedback group (12 subjects) and a control group (11 subjects). All Groups received neurodevelopmental treatment, and sit-to-stand training for 30minutes three times a week for four weeks. During the sit to stand training, the experimental groups received visual feedback and auditory feedback, whereas the control group performed sit-to-stand training without feedback. Five times sit-to-stand test (FTSST), motion analysis and postural sway during sit-to-stand were used to evaluate sit to stand performance ability. In addition, Berg balance scale (BBS) was performed for evaluation of balance function in participants. RESULTS: All groups showed significant increase on FTSST and BBS between pre- and post-intervention. The BBS scores in visual feedback group was significant increase than control group. The motion analysis and postural sway, more improvement was observed in the visual and auditory feedback groups compared with the control group. The only visual feedback group was a better performance of midline excursion during sit-to-stand than control group. CONCLUSION: These findings suggest that sit-to-stand training using a biofeedback may help to improve sit to stand performance and balance ability of stroke patients.