• 근관절건강학회지
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• 제18권1호
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• pp.16-27
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• 2011

Purpose: The purpose of this study was to investigate the effects of a visual feedbackbased balance training, using force platform biofeedback, on the postural balance of elderly faller. Methods: Fifty one community-dwelling older adults (aged 66-88 years) with a recent history of fall participated in the study. Participants were randomized to an experimental group (EG, n=25) and to a control group (CG, n=26). The EG participated in training sessions three times/week for 6 weeks. Visual feedbackbased balance training with the a computerized force platform with visual feedback screen was used in the experimental group. Static balance (center of gravity) and dynamic balance (Functional reach test, Timed "Up & Go" test, Berg balance scale) were assessed before and after end of training. Results: A significant improvement in static balance and dynamic balance were demonstrated within the EG (p<.05), but not in the CG. Conclusion: Visual feedback-based balance training may be an effective intervention to improve postural balance of elderly fallers.

• Journal of Power Electronics
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• 제16권1호
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• pp.351-361
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• 2016

Power quality is a critical issue in distribution systems, where a dynamic voltage restorer (DVR) is commonly used to mitigate the voltage disturbances for loads. This paper deals with a nonlinear control for the three-phase four-wire (3P-4W) DVR under a grid voltage unbalance and nonlinear loads in the distribution system, where a novel control scheme based on the feedback linearization technique is proposed. Through feedback linearization, a nonlinear model of a DVR with a PWM voltage-source inverter (VSI) and LC filters is linearized. Then, the controller design of the linearized model is performed by applying the linear control theory, where the load voltages are kept constant by controlling the d-q-0 axis components of the DVR output voltages. To keep the load voltage unchanged, an in-phase compensation strategy is employed, where the load voltages are recovered to be the same as the previous voltage without a change in the magnitude. With this strategy, the performance of the DVR becomes faster and more stable even under unbalanced source voltages and nonlinear loads. The validity of the proposed control strategy has been verified by simulation and experimental results.

• The Journal of Korean Physical Therapy
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• 제29권2호
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• pp.74-79
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• 2017

Purpose: The purpose of this study was to compare the effects of the FES-gait with augmented feedback training to the FES alone on the gait and functional performance in individuals with chronic stroke. Methods: This study used a pretest and posttest randomized control design. The subjects who signed the agreement were randomly divided into 12 experimental groups and 12 control groups. The experimental groups performed two types of augmented feedback training (knowledge of performance and knowledge of results) together with FES, and the control group performed FES on the TA and GM without augmented feedback and then walked for 30 minutes for 40 meters. Both the experimental groups and the control groups received training five times a week for four weeks. Results: The groups that received the FES with augmented feedback training significantly showed a greater improvement in single limb support (SLS) and gait velocity than the groups that received FES alone. In addition, timed up and go (TUG) test and six minute walk test (6MWT) showed a significant improvement in the groups that received FES with augmented feedback compared to the groups that received FES alone. Conclusion: Compared with the existing FES gait training, augmented feedback showed improvements in gait parameters, walking ability, and dynamic balance. The augmented feedback will be an important method that can provide motivation for motor learning to stroke patients.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.193-193
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• 2000

This paper proposes a dynamic observer that is applicable to linear time-invariant systems subject to unknown input, The proposed method utilities Che output feedback control structure to design unknown input observer. We name it as the dynamic unknown input observer(UIO). The dynamic UIO can be designed easily over the usual static UIO, and the system response could be improved.

• 한국정보시스템학회:학술대회논문집
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• 한국정보시스템학회 2004년도 춘계학술대회
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• pp.316-335
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• 2004

This paper builds a system dynamics model analyzing first mover effect and growth strategy of online retailer, a major segment of B2C e-commerce. The dynamic model in this paper is calibrated to the online book market and Yes24.com as major test cases. The model consists of eight key value chain sectors. Five of these(Users, Site Operations, Human Resources, Financial Accounting, and Fundraising) are internal to the company, and three others(Market, Financial Market, and Relative Performance) are external to the company. With the model, this paper suggests research propositions representing positive feedback loops and negative feedback loops that lead to corporate growth and limits to growth according to dynamic causal relationships among eight key value chain sectors, and simulate these propositions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.173-178
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• 1993

In this paper, we present an algorithmic technique for determining a feedback compensator which will stabilize the interval dynamic system, specifically, the robust regulator design for interval plants. The approach taken here is to allow the system parameters to live within prescribed intervals then design a dynamic feedback compensator which guarantees closed-loop system stable. The main contribution of this paper is the idea of introducing a "simplified Kharitonov's result" for low order polynomials to search for suitable compensator parameters in the compensator parameter space to make the uncertain syste robust. We also design the robust regulator which will D-stabilize (have the closed-loop poles in the left sector only) the dynamic interval system while having good performance. The nuerical examples are given to show the substantially improved robustness which results from our approach. approach.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국제학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.1014-1017
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• 1988

Direct-drive robots have excellent features including no backlash, small friction, and high mechanical stiffness. However, dynamic coupling among joints as well as nonlinear effects become more prominent than traditional robots with reducers. Another critical issue is that the robot becomes more sensitive to the change of load. In this paper, we develop a simple current feedback scheme for reducing the influence of dynamic coupling and load sensitivity on the direct-drive robots. The method is implemented on a 2 d.o.f. planar direct-drive robot. Then the validity of the method is demonstrated through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.632-637
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• 1992

Recently many dynamics control algorithms using robot dynamic equation have been proposed. One of them, Kawato's feedback error learning scheme requires neither an accurate model nor parameter estimation and makes the robot motion closer to the desired trajectory by repeating operation. In this paper, the feedback error learning algorithm is implemented to control a robot system, 5 DOF revolute type movemaster. For this purpose, an actuator dynamic model is constructed considering equivalent robot dynamics model with respect to actuator as well as friction model. The command input acquired from the actuator dynamic model is the sum of products of unknown parameters and known functions. To compute the control algorithm, a parallel processing computer, transputer, is used and real-time computing is achieved. The experiment is done for the three major link of movemaster and its result is presented.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권2호
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• pp.87-89
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• 2005

The necessary and sufficient conditions for the linearization of the nonlinear control systems via restricted dynamic feed back have been found. These require checking with almost all indices from 0 to 2n-3. In this paper, we exploit the inherent structure of the system and find an efficient method to find linearizability of the system by reducing the range of the index to check. Our examples show the efficiency of our method.

• 전자공학회논문지B
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• 제31B권8호
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• pp.64-73
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• 1994

In this paper we present an algorithmic technique for determining a feedback compensator which will stabilize the interval dynamic system specifically the robust regulator design for interval plants. The approach taken here is to allow the system parameters to live within prescribed intervals then design a dynamic feedback compensator which guarantees closed-loop system stable. The main contribution of this paper is the idea of introducting a "simplified Kharitonov`s results" for low order polynomials to search for suitable compensator parameters in the compensator parammeter space to make the uncertain system robust. We also design the robust regulator which will $D_{\phi}$ -stabilize (have the closed-loop poles in the left sector only) the dynamic interval system while having good performance. the numerical examples are given to show the substantially improved robustness which results from our approach.