• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.92-99
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• 1997

A model reference adaptive control(MRAC) theory is very useful for controlling a plant of which the parameters are unknown or vary during operation usint only input-output signal of plant. In this study, 2' nd order discreter time MRAC controller is designed for an electrohydraulic position control system which is represented with nonlinear mathematical model and the least square method is adopted for the para-meter adjustment law. This control algorthm is applied to the position control of electrohydraulic servosystem through computer simulation and the effect of the change of load, sampling time upon the performance following reference model and upon the performance of estimating plant parameters are examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.213-220
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• 1989

This paper describes the application of the variable structure control(VSC) concept for the position control of an electro-hydraulic servomotor system. The basic philosopy of VSC is that the structure of the feedback control is altered as the state crosses discontinuity surfaces in the state space with the result that certain desirable properties are achieved. The switching of the control function yields total(or selective) invariance to system parameter variations and disturbances, and closed loop eigen value placement in time-varing and uncertain systems. The control scheme is derived, implemented and tested in the laboratory where analog controller have been used to control the representive servosystem. The control system schematics are given and simple results are shown for illustration. And the results of variable structure system for the electro-hydraulic servomotor were compared to that of the fixed structure system when load disturbance and system parameter variation exists.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.103-108
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• 2005

In this paper, a controller design procedure for an electro-hydraulic positioning systems have developed using $H_\infty$ control theory. The generalized models and weighting functions for a multiplicative uncertainty modelling error is presented along with $H_\infty$ controller designs in order to investigate the robust stability and performance. The multiplicative uncertainty case is specifically suited for the design of an electro-hydraulic positioning control systems using $H_\infty$ control.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.405-410
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• 1999

Hydraulic pipeline between servo valve and actuator affect the dynamic characteristics of electrohydraulic servo systems in serveral ways. This paper deal with the speed control of oil hydraulic gear motor using electrohydraulic servo valve. The frequency and transient response of electrohydraulic servo valve coupled to a gear motor is anlayzed. In particular, the effect of short and long hydraulic pipelines between servo valve and gear motor is investigated. The dynamic characteristics of the speed control systems of gear motor with short pipeline is first described via frequency response experiments with small signal linearized analysis. Loner pipeline is applied distributed parameter pipeline model with consideration of frequency dependent viscous friction.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.50-59
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• 1999

The effect of a variant drain orifice damping on the characteristics of a servovalve flapper-nozzle stage is analyzed. Steady-state characteristics of flapper-nozzle stage and the linearized dynamics of flapper-nozzle assembly with a spool valve show that the variant drain orifice damping could improve such null performance characteristics as null pressure sensitivity and linearity of gain function. Generalized design criterion and a sufficient condition for servovalve stability are also established.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.181-184
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• 1993

일반적으로유압 장치를 사용하여 힘, 속도, 그리고 위치 등을 제어하는 경우 그 제어계의 설계, 제어방식의 선택에있어서는 최종 목표치의 정도, 응답성 등의 제어 성능을 고려함과 동시에 공업적으로는 가격, 동력효율 등이 중요한 설계인자로서 고려 되어 져야한다. 제어 방식응 벨브 제어와 펌프 제어 방식으로 크게 나뉘어 질 수 있으나, 벨브 제어방식에 있어서는 유압 서보벨브를 사용하여 출력 기구를 고정도로 직접 구도하는 것이 많으나 동력손실이 큰 편이며, 효율을 개선하기 위하여 압력 보상형 비례 전자 제어 벨브를 이용하는 것도 있으나, 소출력용으로서만 이용가능할 뿐이다. 이에 비하여 가변 용량형 펌프를 이용한 제어방식은 정도, 응답성은 다소 뒤떨어 지지만 효율이 양호하고 대출력 기구에 적용 가능하다는 점에서최근 주목의 대상으로되고 있다. 본 연구에서는 에너지의 효율적인사용이 가능한 전기. 유압 펌프 시스템을 설계하기위하여 먼저 각 신호전달 요소에 대한 동특성 및 정특성 실험을 행하여 시스템의 근사적인 모델링을 행하고 사판의 경사각을 제어함으로써 유압모터의 속도를 제어하는 시스템을 설계하여그 성능을 고찰하고자 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.74-80
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• 2006

This paper deals with the control and fault monitoring of a DDV hydraulic actuation system. A hydraulic servo system has a nonlinear dynamics of an orifice flow through a valve spool. A full nonlinear model for a DDV actuation system is driven, and linearized to a simple model which is convenient for a control loop and fault monitor design. A top level requirement on the performance and safety for the actuation system is introduced. A control system and fault monitoring structure which can meet these requirements are discussed. A simulation package for a DDV actuation system which has a triplex redundant structure is developed.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.2
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• pp.23-28
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• 2011

This paper investigates the motion control of a hydraulic motor-load system using the Simple Adaptive Control (SAC) method. The plant transfer function has been modelled mathematically. The open-loop responses have been obtained experimentally in order to identify the design parameters of transfer function. The hydraulic motor-load system has been modelled using the 3D CAD and imbedded in the hydraulic circuit simulation program to verify the overall performance. The experimental results confirm that the SAC method gives a good tracking performance compared to the PID control.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.8
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• pp.936-941
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• 2011

This paper deals with the issue of motion control of a single rod cylinder-load system using simple adaptive control (SAC) method. Prior to controller design, the experiment of open-loop response has been performed. Based on it, design parameters of transfer function are obtained and used for controller design. The effect of parallel feedforward compensator has been investigated by computer simulation, suppressing the oscillatory motion. Through experiments it is conformed that the SAC method gives good tracking performance compared to the PD control method.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.1
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• pp.26-32
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• 1993

The loads exerted on electro-hydraulic servo system are classified into inertial, viscous, and spring load. The additional load called disturbances is also exerted on system but is generally not modeled. To deal with these kinds of loads, it is necessary to maintain the continuous signal transfer, so we can construct compensator to satisfy control specifications using feedback signal such as displacement, velocity, acceleration and pressure known as state variables. In case of controlling the speed of hydraulic motor, we must keep up robust performance for the various loads and disturbances acted on the system. However, the load flow rate in the valve is characterized by nonlinearity so that traditional theory of linear control could not be expected to give the desired performance. In this paper, it is shown that speed controller of hydraulic motor gives a good command following and disturbance rejection performance by applying sliding mode theory as a way of robust control to the nonlinearity, variation of loads and disturbances.