• 대한전자공학회논문지TC
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• 제45권12호
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• pp.13-19
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• 2008

본 논문에서는 4개의 송신 안테나를 사용하는 새로운 폐루프 직교 시공간 블록 부호 (Closed Loop Orthogonal Space-Time Block Code) 기법을 제안하고 기존의 폐루프 기법들과 비트오율 (Bit Error Rate; BER) 성능을 비교한다. 제안된 기법은 송신기에서 폐루프 기법을 통하여 채널 정보를 귀환받고 심벌 결합기를 통해 변조 심벌들을 결합한 후 시공간 블록 부호화하여 송신 안테나로 전송한다. 그 결과, 제안된 기법은 기존의 폐루프 시공간 블록 부호 기법에 비해 귀환된 채널 정보를 보다 효율적으로 이용함으로써 최대의 채널 이득을 획득하는 동시에 full-rate을 만족한다. 또한 채널 행렬이 직교하므로 수신 심벌에 대한 선형적인 복호가 가능하며 수신기는 낮은 복호 복잡도를 갖게 된다. 모의실험 결과, 제안된 기법은 기존의 폐루프 기법들과 비교하여 성능 향상을 보임을 알 수 있다.

• 안보군사학연구
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• 통권1호
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• pp.311-343
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• 2003

In this paper, we propose a generalized disturbance torque suppression control scheme of servo motors for missile fin actuators. Our controller consists of both a model based feed-forward controller and a stabilizing feedback controller. The feed-forward controller is designed such that the output of nominal plant tracks perfectly the reference position command with a desired dynamic characteristics. The feedback controller stabilizes the overall closed loop system. Furthermore, the feedback controller contains a free function that can be chosen arbitrary. The free function can be designed so as to achieve both the suppression of disturbances and the robustness to model uncertainties. In order to illuminate the superior performance of our control scheme to the conventional ones, we present some simulation results.

• 소음진동
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• 제7권6호
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• pp.1007-1013
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• 1997

This paper presents active vibration control scheme of multi-mode forced vibration using piezocetamic sensors and actuators. The control scheme adopted is the Positive Position Feedback (PPF) control. Among various vibration control techniques. PPF control technique makes use of generalized displacement measurements to accomplish the vibration suppression. Two independent controllers are implemented to control the first and the second modes of the beam under external excitation. Experimental results for various damping ratios and feedback gains of the PPF controllers are compared with respect to the contorl efficiency. The results indicate that steady state vibration under wide band excitation can be controlled effectively when multiple sets of PZT sensors and actuators were used with PPF control technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.555-558
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• 1991

The IESF(Integral Error and State Feedback) controller, which incorporates state feedback as a modern control scheme and integral action as a classical control scheme, has better performance than that of the conventional PID controller in linear time-invariant systems. The IESF controller requires the measurement of all the state variables. But, unfortunately, it may be difficult or impossible to measure all state variables in many applications. And the IESF controller is applicable only to pole-assignable linear time-invariant system without time delay. In this paper, new IESF controller structure was proposed which performs feedback with only measurable state variables. In order to estimate the unmeasurable state variables. It was adopted the filter mode by full-order obserber. The good performance and effectiveness of the proposed controller was confirmed by computer simulation.

• 한국정밀공학회지
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• 제9권1호
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• pp.126-136
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• 1992

In this paper, a simple structured feedback compensation scheme for a electro-hydraulic servo system to keep the response characteristics unchanged regardless of the load variation is proposed. In electro-hydraulic servo system, servovalve is most important control element. But the relation between input corrent and output flowrate of the servovalve has properties as follows; firstly, in spite of constant input current, output flowrate decreases as load pressure increases, secondly, according to frequency response of typical servovalve, the characteristics of gain and phase shift is something like 2'nd order system. Load pressure feedback compensation method has been applied to eliminate the first influence, the second influence has been improved by phase lead compensation method. As a result of above compensation methods, regardless of variation load condition, spring and inertia load, the compensation scheme has been verified to be effective within the range of frequency less than 25Hz by static response and dynamic response in time domain and frequency domain through experiments.

• 대한전기학회논문지
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• 제39권8호
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• pp.828-835
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• 1990

A new state feedback control scheme is proposed to improve the stability and dynamic performances of the series resonant converter (SRC). The proposed scheme can be easily implemented without speed limitation. Design parameter of the proposed control is the ratio of the state feedback gains. A closed loop dynamic modeling for the SRC with the proposed control law is derived. Parametric curves which can be used to select the design parameter in the control system are presented. The experimental results show that the excellent dynamic performance of the converter can be obtained by properly selecting the design parameter. The results are further compared with both the theoretical analysis and the frequency control.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.197-202
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• 1991

Recently, an output feedback variable structure control scheme(OFVSCS) is proposed to remove the assumption of full state availability and to make the application of VSC scheme to the high order systems with unmeasurable state variables possible. In this paper, a design method of an output feedback variable structure control system (IOFVSCS) that guarantees the invariance of the sliding mode against process parameter variation and external disturbance is proposed. The IOFVSCS is composed of two components; dynamic switching surface driven by measured I/0 informations and switching control input generator driven by switching surface information and measured output, where the two components are constructed by adopting unknown vector modelling approach. The invariance condition for the IOFVSCS is proved to be the same as that of the conventional VSCS. Simulation results show that the IOFVSCS can be designed to have robust properties better than that of the conventional VSCS in spite that the IOFVSCS is driven by small amount of measured information.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.213-218
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• 2003

The equipment of industrial robot in manufacturing and assembly lines has rapidly increased. In order to achieve high productivity and flexibility, it becomes very important to develop the visual feedback control system with Off-Line Programming System(OLPS). We can save much efforts and time in adjusting robots to newly defined workcells by using OLPS. A proposed visual calibration scheme is based on position-based visual feedback. The calibration program firstly generates predicted images of objects in an assumed end-effector position. The process to generate predicted images consists of projection to screen-coordinates, visible range test and construction of simple silhouette figures. Then camera images acquired are compared with predicted ones for updating position and orientation data. Computation of error is very simple because the scheme is based on perspective projection which can be also expanded to experimental results. Computation time can be extremely reduced because the proposed method does not require the precise calculation of tree-dimensional object data and image Jacobian.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.349-352
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• 1997

A Piezoelectric actuator yields hysteresis effect due to its composed ferroelectric. Hysteresis nonlinearity is neglected when a piezoelectric actuator moves with short stroke. However when it moves with long stroke and high frequency, the hysteresis nonlinearity can not be neglected. The hysteresis nonlinearity of piezoelectric actuator degrades the control performance in precision position control. In this paper, in order to improve the control performance of piezoelectric actuator, an inverse modeling scheme is proposed to compensate the hysteresis nonlinearity problem. And feedforward-feedforward-feedback controller is proposed to give a good tracking performance. The Feedforward controller is inverse hysteresis model, and PID control is sued as a feedback controller. To show the feasibility of the proposed controller and hysteresis modeling, some experiments have been carried out. It is concluded hat the proposed control scheme gives good tracking performance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.969-974
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• 2003

A simple and cost-effective method for the electrostatic suspension of thin plates like silicon wafers is proposed which is based on a switched voltage control scheme. It operates according to a relay feedback control and deploys only a single high-voltage power supply that can deliver a dc voltage of positive and/or negative polarity. This method possesses the unique feature that no high-voltage amplifiers are needed which leads to a remarkable system simplification relative to conventional methods. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping origination from the air between the electrodes and levitated object. Using this scheme, a 4-inch silicon wafer was levitated stably with airgap variation decreasing down to 1 $\mu\textrm{m}$ at an airgap of 100 $\mu\textrm{m}$