• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1994년도 추계학술대회 논문집
• /
• pp.466-471
• /
• 1994

To make a dynamic system a given desired motion trajectory, a new feedback error learning scheme is proposed which is based on the repeatability of dynamic system motion. This method is composed of feedforward and feedback control laws. A benefit of this control scheme is that the input pattern that generates the desired motion can be formed without estimating the physical parameters of system dynamics. The numerical simulations show the good performance of the proposed scheme

• 제어로봇시스템학회논문지
• /
• 제20권6호
• /
• pp.641-646
• /
• 2014

In this paper, we propose a controller for a ball and beam system which reduces the measurement error effect under AC and DC noise. The ball and beam system measures data through a sensor. If sensor noise is included in a controller via the feedback channel, the signal is distorted and the entire system cannot work normally. Therefore, some appropriate action for the measurement error effect is essential in the controller design. Our controller is equipped with a gain-scaling factor and a compensator to reduce the effect of measurement error in the feedback signal. Effectively, our proposed controller can reduce the AC and DC noise of a feedback sensor. We analyze the proposed controller by Laplace transform technique and illustrate the improved control performance via an experiment for a ball and beam system.

• Structural Engineering and Mechanics
• /
• 제12권6호
• /
• pp.633-656
• /
• 2001

In this paper, modal control with direct output feedback is formulated in a systematic manner for easy implementation. Its application to the seismic protection of structural systems is verified by a shaking table test, which involves a full-scale building model and an active bracing system as the control device. Two modal control cases, namely, one full-state feedback and one direct output feedback control were tested and compared. The experimental result shows that in mitigating the seismic response of building structures, modal control with direct output feedback can be as effective and efficient as that with full-state feedback control. For practical concerns, the control performance of the proposed method in the presence of sensor noise and stiffness modeling error was also investigated. The numerical result shows that although the control force may be increased, the maximum floor displacements of the controlled structure are very insensitive to sensor noise and modeling error.

• 한국통신학회논문지
• /
• 제34권12A호
• /
• pp.991-997
• /
• 2009

전송 빔포밍은 다수의 송수신 안테나 기법에서 다이버시티 이득을 최대로 얻을 수 있는 간단한 방법으로 널리 알려져 있다. 그러나 이와 같은 다이버시티 이득을 얻기 위해서는 송신단과 수신단 모두 채널 상태에 관한 정보를 완벽하게 알고 있어야 하고 이는 피드백이 한정되어 있는 실제 시스템에서 비현실적이다. 이와 같은 이유로 현실적인 시스템에서는 송수신단이 모두 알고 있는 코드북(codebook)에서 수신단 출력에서의 신호 대 잡음비(SNR)가 최댓값을 갖는 전송 빔포밍 벡터를 선택하여 이의 인덱스만 수신단에서 송신단으로 피드백 해주는 코드북을 기반으로 하는 피드백 기법을 사용한다. 본 논문에서 우리는 코드북 기반의 피드백을 사용하는 다중 송신 안테나 시스템 (MISO)에서 피드백 채널에 에러가 존재하였을 경우에 대한 성능을 평균 비트 에러 (BER) 측면에서 수식적으로 분석하였으며, 이 수식을 이용하여 주어진 코드북에 대하여 최적의 빔포밍 벡터 인덱싱 기법을 제안하였다.

• 제어로봇시스템학회논문지
• /
• 제16권7호
• /
• pp.668-673
• /
• 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.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2005년도 ICCAS
• /
• pp.330-333
• /
• 2005

In this study, a method of designing a neurointerface using neural network (NN) is proposed for controlling nonholonomic mobile robots. According to the concept of virtual master-slave robots, in particular, a partially stable inverse dynamic model of the master robot is acquired online through the NN by applying a feedback-error learning method, in which the feedback controller is assumed to be based on a PD compensator for such a nonholonomic robot. A tracking control problem is demonstrated by some simulations for a nonholonomic mobile robot with two-independent driving wheels.

• 한국HCI학회:학술대회논문집
• /
• 한국HCI학회 2009년도 학술대회
• /
• pp.1109-1113
• /
• 2009

웹사이트의 회원가입 프로세스, 온라인 쇼핑 사이트의 구매 프로세스 등에서 유저와 서버간 data 교환은 사용자들이 입력 폼(form)에 데이터를 입력함으로써 이루어지는데, 이때 유저가 입력 오류를 일으킨 경우 시스템은 오류메시지를 통해서 수정을 유도하게 된다. 적절한 피드백 제공 방식과 관련된 문헌을 살펴보면 국제 표준화 기구(ISO)는 즉각적인 피드백 제공을 권고하고 있으나[1], Bargas et al. 의 연구 결과 온라인에서 데이터를 입력할 때에는 즉각적인 피드백 보다 작성 완료 후 한번에 오류 메시지를 제공하는 피드백 방식이 더 사용성이 높은 것으로 나타났다[2]. 본 연구에서는 오류 발생 즉시 메시지를 제시하는 조건과 작성 완료 후 한번에 메시지를 제시하는 조건으로 나누어 오류 메시지 제시 시점에 따른 사용성을 비교하는 실험을 실시하였다. 실험 결과 Bargas et al.의 연구 결과와 대조적으로 즉각적인 피드백이 제시되는 경우 사용성과 만족도가 더 높은 것으로 나타났다.

• 제어로봇시스템학회논문지
• /
• 제8권6호
• /
• pp.524-532
• /
• 2002

This paper presents a new in-flight alignment method for an SDINS under large initial heading error. To handle large heading error, a new attitude error model is introduced. The attitude errors are divided into heading error and leveling errors using a newly defined horizontal frame. Some navigation error dynamic models are derived from the attitude error model for indirect feedback filtering of the in-flight alignment system. A Kalman filter with Position measurement is designed to estimate navigation errors as the indirect feedback filter Simulation results show that the proposed in-flight alignment method reduces the heading error very quickly from more than 40deg to about 5deg so as to apply a refined navigation filter. The total alignment process including leveling mode and navigation mode in addition to the proposed one allows large initial values not only in heading error but also in leveling errors.

• International Journal of Control, Automation, and Systems
• /
• 제6권5호
• /
• pp.689-701
• /
• 2008

In this paper, a fully adaptive feedforward feedback synchronized tracking control approach is developed for precision tracking control of 6 degree of freedom (6DOF) Stewart Platform. The proposed controller is designed in decentralized form for implementation simplicity. Interconnections among different subsystems and gravity effect are eliminated by the feedforward control action. Feedback control action guarantees the stability of the system. The gains of the proposed controller can be updated on line without requiring any prior knowledge of Stewart Platform manipulator. Thus the control approach is claimed to be fully adaptive. By employing cross-coupling error technology, the proposed approach can guarantee both of position error and synchronization error converge to zero asymptotically. Because the actuators work in synchronous manner, the tracking performances are improved. The corresponding stability analysis is also presented in this paper. Finally, simulation is demonstrated to verify the effectiveness of the proposed approach.

• Journal of Communications and Networks
• /
• 제16권3호
• /
• pp.322-334
• /
• 2014

Multimedia content is very sensitive to packet loss and therefore multimedia streams are typically protected against packet loss, either by supporting retransmission requests or by adding redundant forward error correction (FEC) data. However, the redundant FEC information introduces significant additional bandwidth requirements, as compared to the bitrate of the original video stream. Especially on wireless and mobile networks, bandwidth availability is limited and variable. In this article, an adaptive FEC (A-FEC) system is presented whereby the redundancy rate is dynamically adjusted to the packet loss, based on feedback messages from the client. We present a statistical model of our A-FEC system and validate the proposed system under different packet loss conditions and loss probabilities. The experimental results show that 57-95%bandwidth gain can be achieved compared with a static FEC approach.