• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.801-805
• /
• 2008

Today, hydraulic systems play an important role in modern industry for the reasons that hydraulic actuator systems take many advantages over other technologies with high durability and the ability to produce large forces at high speeds. In recent years, electro-hydraulic actuator systems, which combine electric and hydraulic technology into a compact unit, have been adapted to a wide variety of force, speed and torque requirements. Moreover these systems resolve energy consumption and noise problems characteristic existed in the conventional hydraulic systems. Therefore, these systems have a wide range application fields especially in an excavator. So the purpose of this paper is to demonstrate efficiency of the energy saving and present some control algorithms which apply to electro-hydraulic actuator system in the bucket of the excavator. Experiments are carried out to verify the effectiveness of the proposed system with various external loads as in real working conditions.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.3 no.2
• /
• pp.14-20
• /
• 2006

A controller design procedure for an electro-hydraulic positioning systems has been developed using $H{\infty}$ control. The generalized plant models and weighting function for multiplicative uncertainty modelling error was presented along with $H{\infty}$ controller designs in order to investigate the robust stability and performance. Both disturbance rejection and command tracking performances were improved with the $H{\infty}$ controller, and the better uniformity of time response is achieved across wide range of operating conditions than the PID, LQR and LQG control scheme. The multiplicative uncertainty case was specifically suited for the design of an electro-hydraulic positioning control systems using $H{\infty}$ control.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.2
• /
• pp.45-53
• /
• 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
• /
• v.9 no.2
• /
• pp.124-130
• /
• 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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2005.05a
• /
• pp.103-108
• /
• 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 Precision Engineering Conference
• /
• 2012.10a
• /
• pp.49-50
• /
• 2012

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.4
• /
• pp.907-914
• /
• 1999

This paper studies on the model identification of electro-hydraulic servo systems, which are composed of servo valves, double-rod cylinder and load mass. The identified plant is described as a discrete-time ARX or ARMAX model which is respectively obtained from the identification algorithms of least square error method, instrumental variable method and prediction error method. where a nominal model and the variation of model parameters are quantitatively evaluated.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1445-1449
• /
• 1996

To evaluate of active suspension, it is necessary for special equipment - so called Test Rig which can perfectly realize the road condition and the impact from the road. And most of the test rig systems controlling force accurately and rapidly consist of electro-hydraulic servo mechanism, and they need robust controller which can endure outer road change. But in the case of PID controller, we should choose its best gains by trial and error method, and once its gains are fixed, they cannot get changed, so we should reset PID controller gains respectively when the road is changed. Therefore based on the load pressure feedback compensation method, our aim at constructing electro-hydraulic test rig is not affected by various road disturbance.

• Journal of Biosystems Engineering
• /
• v.17 no.3
• /
• pp.223-228
• /
• 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 Institute of Control, Robotics and Systems
• /
• v.9 no.6
• /
• pp.442-447
• /
• 2003

This paper demonstrates that a modified hybrid neural-genetic multimodel parameter estimation algorithm can be applied to structured system identification of an electro-hydraulic servo system. This algorithm is consists of a recurrent incremental credit assignment(ICRA) neural network and a genetic algorithm. The ICRA neural network evaluates each member of a generation of model and genetic algorithm produces new generation of model. The modified hybrid neural-genetic multimodel parameter estimation algorithm is applied to an electro-hydraulic servo system the task to find the parameter values such as mass, damping coefficient, bulk modulus, spring coefficient and disturbance, which minimizes the total square error.