• Journal of the Ergonomics Society of Korea
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• v.31 no.4
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• pp.551-556
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• 2012

Objective: This study presents the effect of visual feedback on one-hand gesture performance in vision-based gesture recognition system when people use gestures to control a screen device remotely. Backgroud: gesture interaction receives growing attention because it uses advanced sensor technology and it allows users natural interaction using their own body motion. In generating motion, visual feedback has been to considered critical factor affect speed and accuracy. Method: three types of visual feedback(arrow, star, and animation) were selected and 20 gestures were listed. 12 participants perform each 20 gestures while given 3 types of visual feedback in turn. Results: People made longer hand trace and take longer time to make a gesture when they were given arrow shape feedback than star-shape feedback. The animation type feedback was most preferred. Conclusion: The type of visual feedback showed statistically significant effect on the length of hand trace, elapsed time, and speed of motion in performing a gesture. Application: This study could be applied to any device that needs visual feedback for device control. A big feedback generate shorter length of motion trace, less time, faster than smaller one when people performs gestures to control a device. So the big size of visual feedback would be recommended for a situation requiring fast actions. On the other hand, the smaller visual feedback would be recommended for a situation requiring elaborated actions.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.3
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• pp.134-141
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• 2003

PID controllers with constant gains have been widely used in various control systems due to its powerful performance and easy implementation. But it is difficult to have uniformly good control performance in all operating conditions. In this paper, we propose a nonlinear variable PR controller with immune feedback mechanism. An immune feedback mechanism is based on the functioning of biological T-cells, they include both an active term, which controls response speed. and an inhibitive term, which controls stabilization effect. Therefore, the proposed nonlinear PID controller is based on immune responses of biological. immune feedback mechanism which is the cell mediated immunity and In order to choose the optimal nonlinear PID controller games, we also propose the tuning algorithm of nonlinear function parameter in immune feedback mechanism. To verify performance of the proposed algorithm, the speed control of nonlinear DC motor are performed. Front the simulation results, we have found that the proposed algorithm is more superior to the conventional constant fain PID controller.

• Korean Journal of Human Ecology
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• v.15 no.4
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• pp.551-561
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• 2006

The purpose of the study is to examine the influence of children's familiarity with a task and teachers' feedback on their problem solving performances. It was assumed that children's' problem solving performance would be different depending on the children's familiarity with a task and the feedback from teachers. The study also examined whether children's' problem solving competence would be different depending on their gender and age. The experiment was conducted with two experimental tools. The subjects were 58 children who were 5 to 6-year-old, enrolled in kindergartens in Koyang city in Kyunggi province. The collected data were processed with SPSS 11.0 program to get the average and the standard deviations, and with one-way ANOVA and two-way ANOVA with repeated measures. The results of the experiment are as follows; First, children's' problem solving competence was different depending on their age. Older children showed higher performance than younger children, while there's no difference in children's performance depending on their gender. Second, the teachers' feedback didn't influence children's problem solving performance. Third, children showed higher performance when familiar tasks were provided, compared to when typical tasks were provided. Finally, this study found that children's task familiarity has an influence on their problem solving performance.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.299-303
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• 2011

In this paper, we propose an output feedback controller for a chain of integrators system compensating measurement noise of feedback sensor. Measurement noise makes feedback signals distorted, and results in performance degradation or even system failure. Therefore, we need to design a robust controller to accommodate the possible measurement noise in the feedback information. Our controller is equipped with a gain-scaling factor to reject or minimize the effect of measurement noise in output feedback information. We give a theoretical analysis of the controlled system and illustrate the improved control performance via an example.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.4
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• pp.401-409
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• 2012

PURPOSE: The purpose of this study is to assess the difference in the effect of provision of feedback on knowledge of performance and knowledge of result in the training using somesthetic video game aimed at enhancement of balance of hemiparalysis patients due to stroke. METHODS: 20 stroke patients participated in the study. The participants were randomly divided into 2 groups, namely, the knowledge of performance feedback group (KP group, n=10) and the knowledge of result feedback group (KR group, n=10). Both groups received somesthetic video game training 5 times (30 minutes each) a week for total of 4 weeks. The KP group received feedback on the patterns of movement in execution of somesthetic video game. The KR group received feedback on the scores acquired following execution of somesthetic video game. Verification of the significance of the data was performed through paired t-test and independent t-test. RESULTS: Both groups displayed significant reduction in the movement of center of pressure (COP) and Timed up and Go (TUG), and significant increase in the Berg Balance Scale (BBS) following the training. Although the movement of COP was reduced for the KP group in comparison to the KR group, it was not statistically significant, and there was significant reduction in TUG and significant increase in BBS. CONCLUSION: The above results illustrate that provision of feedback on knowledge of performance is more effective than feedback on knowledge of result in somesthetic video game training for the purpose of enhancement of balance in stroke patients. Therefore, provision of feedback on knowledge of performance is necessary in somesthetic video game training for stroke patients.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.327-334
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• 2008

Conventional on-channel-repeaters (OCRs) have a crucial problem that the power of a re-transmitted signal is highly limited by a feedback signal due to antenna coupling. The power limitation problem in OCRs has been solved by incorporating a demodulation-type feedback canceller which eliminates unwanted feedback signals by estimating a feedback channel. In applying the demodulation-type feedback canceller to T-DMB repeaters, there is a troublesome problem of unfrequent known pilot symbols, resulting in poor convergence performance of channel estimation. To solve this problem and enhance the accuracy of estimation, we propose a partitioning method of the Phase Reference Symbol (PRS) transformed in time domain. Since filter coefficients are updated every one partitioned subgroup, the number of updates is increased by the number of partitioned subgroups and thus the convergence speed is enhanced. The improved performance of feedback-channel estimation is directly connected with the feedback-cancellation performance. Simulation result shows that the feedback canceller incorporating the proposed partitioning method has a good performance in terms of residual feedback power.

• Journal of the Ergonomics Society of Korea
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• v.31 no.6
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• pp.725-731
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• 2012

Objective: The aim of this study is to investigate visual feedback effects and human performance in the foot mouse control. Background: Generally, computer mouse tasks are controlled by visual feedback. In order to understand the characteristics of a foot mouse control, it is important to investigate the patterns of visual feedback involved in foot-mouse control tasks. Human performance of foot mouse control is also an important factor to understand the foot mouse control. Method: Three types of mouse control were determined to investigate visual feedback effects and human performance in the foot mouse control. Visual feedback effects in the foot mouse control were compared with those of a typical hand mouse. The cursor movement speed and mental workload were measured in the three types of tasks and two types of mouses. Results: Mouse control tasks with an element of homing-in to the target were more quickly performed by the hand mouse than the foot mouse. Mental workload was also higher in the foot mouse than the hand mouse. However, in the steering movement, human performance of the foot mouse control was not lower than that of the hand mouse control. Visual feedback in the foot mouse control was less required than in the hand mouse control. Conclusion: The foot mouse was not efficient in the most mouse control tasks, compared to the hand mouse. However, the foot mouse was efficient in the steering movement, moving a cursor within a path with lateral constraints. Application: The results of this study might help to develop the foot mouse.

• ETRI Journal
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• v.38 no.2
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• pp.280-290
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• 2016

To implement high-order multiuser multiple input and multiple output (MU-MIMO) for massive MIMO systems, there must be a feedback scheme that can warrant its performance with a limited signaling overhead. The interference-to-noise ratio can be a basis for a novel form of Codebook (CB)-based MU-MIMO feedback scheme. The objective of this paper is to verify such a scheme's performance under a practical system configuration with a 3D channel model in various radio environments. We evaluate the performance of various CB-based feedback schemes with different types of overhead reduction approaches, providing an experimental ground with which to optimize a CB-based MU-MIMO feedback scheme while identifying the design constraints for a massive MIMO system.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.7
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• pp.668-673
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• 2010

Given a periodic reference signal or disturbance, repetitive control is a special control scheme to reduce a tracking error effectively by the periodic signal generator in the repetitive controller. In general, a repetitive controller is added on the existing feedback control system to improve the tracking performance. However, because the information used in the design of the feedback controller is not taken into account, the design problem of the repetitive controller is totally another problem irrespective of that of the feedback controller. In this paper, we present a more general method to design an add-on type repetitive controller using the information on the performance of the existing feedback control system. We first show that a robust stability condition of repetitive control systems is obtained using the well-known robust performance condition of general feedback control systems. 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. From the obtained results, several design criterions for repetitive controller are provided. Through the simulation study, the feasibility of the proposed method is verified.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.2
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• pp.156-160
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• 2012

In this paper, we investigate the effect of asynchronous haptic and video feedback on the performance of teleoperation. To analyze the effect, a tele-manipulation experiment is specially designed, which operator moves square objects from one place to another place by using master/slave telerobotic system. Task completion time and total number of falling of the object are used for evaluating the performance. Subjective study was conducted with 10 subjects in 16 different combinations of video and haptic feedback while participants didn't have any prior information about the amount of each delay. Initially we assume that synchronized haptic and video feedback would give best performance. However as a result, we found that the accuracy was increased when haptic and video feedback was synchronized, and the completion time was decreased when one of the feedback (either haptic or video) was decreased. Another interesting fact that we found in this experiment is that it showed even better accuracy when haptic information arrives little bit earlier than video information, than the case when those are synchronized.