• Journal of Biosystems Engineering
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• v.17 no.3
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• pp.223-228
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• 1992

This study was conducted to develop an electro-hydraulic three-point hitch control system using an electro-hydraulic servo valve and microcomputer and to investigate the performance of the three-point hitch control system through indoor and field experiments. 1. The results from indoor experiments coincided with those from computer simulation reported in the previous paper. However, the draft control with the value 4 of Kd showed a slight sustained oscillation after it reached the draft set. 2. From the field experiments, it appeared that the RMS errors increased with the ground speed of tractor. In position control, the three-point hitch control system with electro-hydraulic servo valve showed better performance than that with on-off electro-magnetic valve in the ground speed less than 1.6 m/s. In draft control, however, there was no significant differece in performance between those two systems. 3. In depth control, the both types of electro-hydraulic three-point hitch control system showed better performance than the conventional mechanical-hydraulic three-point hitch control system.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.45-53
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• 2009

Today, reduction of $CO_2$ exhaustion gas for global-warming prevention becomes important issues in all industrial fields. Hydraulic systems have been widely used in industrial applications due to high power density and so on. However hydraulic pump is always being operated by engine or electric motor in the conventional hydraulic system. Therefore most of the conventional hydraulic system is not efficient system. Recently, an electro-hydraulic hybrid system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. In the electro-hydraulic hybrid system, hydraulic pump is operated by electric motor only when hydraulic power is needed. Therefore the electro-hydraulic system can reduce the energy consumption drastically when compared to the conventional hydraulic systems. This paper presents a new kind of hydraulic load simulator which is composed of electro-hydraulic hybrid system. Disturbances in the real working condition make the control performance decrease or go bad. QFT controller is designed to eliminate or reduce the disturbance and improve the control performance of the electro-hydraulic load simulator. Experimental results show that the proposed controller is verified to apply for electro-hydraulic hybrid system with varied external disturbances.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.2
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• pp.124-130
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• 2003

The electro-hydraulic servo system with a servo valve is applied widely in force control. However, the composition of control system using a servo valve is difficult due to nonlinearities in the servo valve, such as square-root terms in flow equation. The electro-hydraulic servo system using a DDV(Direct Drive Valve) instead of a servo valve was proposed and it's characteristics was estimated. The DDV and whole system are modelled by parameter identification using the input-and-output data, then the models are verified by the comparison of simulation with experiment. Also, the state feedback controller has been designed based on this model, then the performance of the electro-hydraulic force servo system using a DDV is evaluated by simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1360-1365
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• 2011

Electro-hydraulic servo motor is used to a lot of in the field of industrial equipment which requires one of the control functions among pressure, flow, and power output. In this paper, linear discrete reference model of the electro-hydraulic servo motor system are made for 1-step ahead predictive control. The parameters of electro-hydraulic servo motor system are estimated using the recursive least square method. 1-step ahead predictive model output of electro-hydraulic servo motor system corresponded to reference model output in spite of estimated parameters are not meet real parameters. Control performance affections are studied due to the forgetting factors variation.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.48-55
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• 2004

This study presents a genetic algorithm-based method fur optimizing control parameters in the pressure control of electro-hydraulic pump with variable displacement. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics and search the optimal control parameters maximizing a measure that evaluates the performance of a system. Four control gains of the PI-PD cascade controller for an electro-hydraulic pressure control system are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that genetic algorithm is an efficient scheme in optimizing control parameters of the pressure control of electro-hydraulic pump with variable displacement.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.195-205
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• 1997

The propulsion marine diesel engine have been widely applied with a mechanical- hydraulic governor to control the ship speed for long time. But it was recently very difficult for the mechani¬cal - hydraulic governor to control the speed of engine under the condition of low speed and low load because of jiggling by rough fluctuation of rotating torque and hunting by dead time of Desiel engnie The performance improvement of mechanical - hydraulic governor is required to solve these problems of control system. The electro - hydraulic governor using PID algorithm is provided to compensate the faults of mechanical- hydraulic governor. In this paper, in order to analyze the ship speed control system, the transfer function was converted from the z tansformation to w transformation. The influence of dead time changing by engine speed which induces hunting phenomena was investigated by Nichols chart of w plane. As a method of performance improvement of mechanical hydraulic governor, a Eletro - hydraulic governor shows that fine control results can be obtained through optimal parameter tuning of PID

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2181-2190
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• 1993

An electro-hydraulic controlled rig type CVT(Continuously Variable Transmission) system was developed and its performance tests were carried out for the optimal operation. A CVT map was suggested based on the speed ration-axial force-torque relationship which was derived from the metal belt CVT mechanics. Also, a real time control and operation software was developed for the electro-hydraulic CVT system. By using the software and the CVT map, the control system was designed for the CVT speed ratio control with various drive modes. The electro-hydraulic CVT system developed in this study showed that the optimal operation algorithm could be obtained for the best fuel economy or the maximum power mode.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.77-89
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• 2020

This paper proposes a simple and intuitive model-free torque-tracking control for rotary electro-hydraulic actuators. The undesirable natural-velocity-feedback effect is discussed by introducing mechanical impedance into the electro-hydraulic actuation system. The proposed model-free torque control comprises inner- and outer-loop control to achieve two control objectives. Inner-loop control reduces the mechanical impedance passively and optimally. To improve the tracking accuracy, a certain form of proportional-integral-derivative control is applied to the outer loop. The robustness of the proposed closed-loop system against external disturbances is demonstrated by transforming the two-loop control structure into a disturbance observer form. The proposed method is validated on a single joint electro-hydraulic actuator.

• Journal of Drive and Control
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• v.16 no.4
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• pp.16-22
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• 2019

The electro-hydraulic training device (TP511) provided by Festo Didactic are widely used, but teaching materials do not include mathematical modeling. Thus, there is a limit for full-scale learning about the electro-hydraulic servo system by using this equipment. In this study, for the purpose of improving students' understanding of the classical control and modern control Festo's electro-hydraulic servo training device (TP511) was mathematically modeled and parameter values were calculated by examining the characteristics of each component. And P, PI, PD, and PID controllers highly used in the industrial field, were designed by using the root locus method to achieve the optimal gains and used for simulation and experiments using the Festo's electro-hydraulic servo training apparatus. The validity of the derived mathematical model and the calculated parameter values were verified through simulation and experiment. It was found that the p control can achieve the control target more effectively than the pid control for Festo's electro-hydraulic servo training system by using the root locus method.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.236-243
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• 1999

This study deals with the application of high speed on-off valves to an electro-hydraulic servo indexing system incorporated electro-hydraulic servo valces. Comparing with the electro-hydraulic servo valve the high speed on-off valve has some merits. Which included low price robustness to the oil contamination and dircect control without D/A converter. The considered sys-tem of this study is controlled by pulse width modulation(PWM) of the control law which is pro-duced by a PID controller which is used broadly in industrial equipments. The dynamic character-istics corresponding to variations of system parameters such as inertia moment system gain and supply pressure are investigated by computer simulation and experiment. Consequently the availability of the application of high speed on-off valve to servo indexing system instead of electro-hydraulic servo valve is confirmed.