• Journal of Power Electronics
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• 제9권4호
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• pp.654-666
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• 2009

Direct torque control (DTC) of induction machines (IM) is a well-known strategy of these drives control which has a fast dynamic and a good tracking response. In this paper a nonlinear DTC of speed sensorless IM drives is presented which is based on input-output feedback linearization control theory. The IM model includes iron losses using a speed dependent shunt resistance which is determined through some effective experiments. A stator flux vector is estimated through a simple integrator based on stator voltage equations in the stationary frame. A novel method is introduced for DC offset compensation which is a major problem of AC machines, especially at low speeds. Rotor speed is also determined using a rotor flux sliding-mode (SM) observer which is capable of rotor flux space vector and rotor speed simultaneous estimation. In addition, stator and rotor resistances are estimated using a simple but effective recursive least squares (RLS) method combined with the so-called SM observer. The proposed control idea is experimentally implemented in real time using a FPGA board synchronized with a personal computer (PC). Simulation and experimental results are presented to show the capability and validity of the proposed control method.

• 한국통신학회논문지
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• 제19권12호
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• pp.2328-2339
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• 1994

ATM 전송 기술에 있어 PBS 방법은 혼재된 트래픽 환경하에서 각각의 트래픽이 서로 다른 서비스 품질을 요구할 경우, 체증 상태의 망 관리를 효율적으로 하기 위한 제시된 셀 준위의 우선 순위 제어방식이다. 이 논문에서는 시간 지연과 셀 손실에 민감한 두 트래픽에 대한 처리를 PBS 방법을 적용시켜 셀 손실에 대한 분포를 분석하고자 한다. 특히, 실시간 트래픽의 주요한 성능 척도인 연속적 셀 손실 확률을 정확하게 구하기 위한 셀 손실 간의 독립성을 가정하지 않은 재귀적 알고리듬을 사용한다. 이 방법에 의해 유도된 셀 손실에 대한 분포의 결과는 독립을 가정한 경우보다 더 심각하게 나타난다. 그리고, 실시간 트래픽에 대한 PBS 방법의 제한성과 주어진 서비스 품질 기준에 따른 허용 부하를 증가시킬 수 있음을 보여준다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권10호
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• pp.573-580
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• 2002

This paper presents neural load disturbance observer that used to deadbeat load torque observer and regulation of the compensation gain by parameter estimator As a result, the response of PMSM follows that of the nominal plant. The load torque compensation method is compose of a neural deadbeat observer. To reduce of the noise effect, the post-filter, which is implemented by MA process, is proposed. The parameter compensator with RLSM(recursive least square method) parameter estimator is suggested to increase the performance of the load torque observer and main controller. The proposed estimator is combined with a high performance neural torque observer to resolve the problems. As a result, the proposed control system becomes a robust and precise system against the load torque and the parameter variation. A stability and usefulness, through the verified computer simulation and experiment, are shown in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2949-2952
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• 2000

A new neural networks and learning algorithm are proposed in order to measure nonlinear heights of complexed road environments in realtime without pre-information. This new neural networks is Error Self Recurrent Neural Networks(ESRN), The structure of it is similar to recurrent neural networks: a delayed output as the input and a delayed error between the output of plant and neural networks as a bias input. In addition, we compute the desired value of hidden layer by an optimal method instead of transfering desired values by back-propagation and each weights are updated by RLS(Recursive Least Square). Consequently. this neural networks are not sensitive to initial weights and a learning rate, and have a faster convergence rate than conventional neural networks. We can estimate nonlinear models in realtime by ESRN and learning algorithm and control nonlinear models. To show the performance of this one. we control 7 degree of freedom full car model with several control method. From this simulation. this estimation and controller were proved to be effective to the measurements of nonlinear road environment systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2814-2818
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• 2000

This paper describes an image processing algorithm capable of recognizing the road lane using a CDF (Cumulative Distribution Function). which is designed for the model function of the road lane. The CDF has distinctive peak points at the vicinity of the lane direction because of the directional and positional continuities of the lane. We construct a scatter diagram by collecting the edge pixels with the direction corresponding to the peak point of the CDF and carry out the principal axis-based line fitting for the scatter diagram to obtain the lane information. As noises play the role of making a lot of similar features to the lane appear and disappear in the image we introduce a recursive estimator of the function to reduce the noise effect and a scene understanding index (SUI) formulated by statistical parameters of the CDF to prevent a false alarm or miss detection. The proposed algorithm has been implemented in a real time on the video data obtained from a test vehicle driven in a typical highway.

• 영어어문교육
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• 제11권2호
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• pp.67-89
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• 2005

Writing is a difficult skill for many people, both for children and adult alike and generally most people find it difficult to write down their thoughts effectively. Numerous studies have revealed that teachers find it frustrating to teach writing and many failed to help ESL students develop their writing ability. The theoretical emphasis on process oriented writing instruction has, in general brought about positive changes in the way writing is taught and has become widely accepted in the teaching of English as a second or foreign language (ESL/EFL). Although the interpretation and implementation of the process approach varies considerably from instructor to instructor, nevertheless, the emphasis on process writing has brought about significant and beneficial changes in teachers' orientations to writing. Despite the theoretical recognition of writing as a recursive process, many ESL/EFL classrooms continue to teach writing as a linear sequence of planning, pre-writing, writing, revising and editing and has not enhanced ESL/EFL students writing ability to the desired level. There appears to be a missing link in helping students to crystallize their thoughts before writing. Studies have shown that incorporating visual thinking tools into the process approach of ESL writing can enhance students' ability to write. This paper reports the findings of an exploratory study on the effects of using visual thinking tools in enhancing ESL students writing.

• ETRI Journal
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• 제37권5호
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• pp.833-844
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• 2015

Recently, new network systems have begun to emerge (for instance, 5G, IoT, and ICN) that require capabilities beyond that provided by existing IP networking. To fulfill the requirements, some new networking technologies are being proposed. The promising approach of the new networking technology is to try to overcome the architectural limitations of IP networking by adopting an identifier (ID)-based networking concept in which communication objects are identified independently from a specific location and mechanism. However, we note that existing ID-based networking proposals only partially meet the requirements of emerging and future networks. This paper proposes a new ID-based networking architecture and mechanisms, named IDNet, to meet all of the requirements of emerging and future networks. IDNet is designed with four major functional blocks-routing, forwarding, mapping system, and application interface. For the proof of concept, we develop numeric models for IDNet and implement a prototype of IDNet.

• Smart Structures and Systems
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• 제17권6호
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• pp.903-915
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• 2016

The classical Kalman filter (KF) provides a practical and efficient state estimation approach for structural identification and vibration control. However, the classical KF approach is applicable only when external inputs are assumed known. Over the years, some approaches based on Kalman filter with unknown inputs (KF-UI) have been presented. However, these approaches based solely on acceleration measurements are inherently unstable which leads poor tracking and so-called drifts in the estimated unknown inputs and structural displacement in the presence of measurement noises. Either on-line regularization schemes or post signal processing is required to treat the drifts in the identification results, which prohibits the real-time identification of joint structural state and unknown inputs. In this paper, it is aimed to extend the classical KF approach to circumvent the above limitation for real time joint estimation of structural states and the unknown inputs. Based on the scheme of the classical KF, analytical recursive solutions of an improved Kalman filter with unknown excitations (KF-UI) are derived and presented. Moreover, data fusion of partially measured displacement and acceleration responses is used to prevent in real time the so-called drifts in the estimated structural state vector and unknown external inputs. The effectiveness and performance of the proposed approach are demonstrated by some numerical examples.

• 대한조선학회논문집
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• 제57권3호
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• pp.175-181
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• 2020

For the success of a structural integrity management, it is essential to acquire structural response data at some critical locations with limited number of sensors. In this study, the structural response of numerical model was estimated by data fusion approach based on the Kalman filter known as stochastic recursive filter. Firstly, transient direct analysis was conducted to calculate the acceleration and strain of the numerical standing beam model, then the noise signals were mixed to generate the numerical measurement signals. The acceleration measurement signal was provided to the Kalman filter as an information on the external load, and the displacement measurement, which was transformed from the strain measurement by using strain-displacement conversion relationship, was provided into the Kalman filter as an observation information. Finally, the Kalman filter estimated the displacement by combining both displacements calculated from each numerically measured signal, then the estimated results were compared with the results of the transient direct analysis.

• 반도체디스플레이기술학회지
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• 제7권1호
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• pp.17-22
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• 2008

The proposed hybrid controller consists of PID controller, feedforward controller and RLSE (Recursive Least Square Estimating) adaptive controller to compensate the force ripple that is periodic function of position in a linear motor. The modeling of force ripple is divided into the current-dependent and current-independent components. The current independent components never change as the current into the linear motor changes. On the other hand, the current-dependent components change as current varies when the velocity and load of the linear motor change. The proposed controller can compensate both force ripples. The feedforward controller compensates the current-independent components and the RLSE adaptive controller compensates the current-dependents components. We verified the performance of the controller by simulation and experiments.