• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.583-592
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• 1999

In order to control systems which contain nonlinearities control strategies must deal with the effects of them. Since most of control methods based on system mathematical models have been mainly developed focused on stability robustness against nonlinearities or uncertainties under the assumption that controlled systems are linear time invariant they have certain amount of limita-tions to smartly improve control perfomances of systems disturbed by nonlinearities or uncertainties. In this paper the fuzzy PID control law is suggested which can improve control performances of the nonlinear heavy load hydraulic systems disturbed by nonlinearities and uncertainties. Although the derivation process is based on the design process similar to general fuzzy logic con-troller resultant control law has analytical forms with time varying PID gains rather than linguis-tic forms so that implementation using commn-used versatile microprocessors can be achieved easily and effectively in real-time control aspect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1565-1576
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• 2002

By way of driving a 2-way on/off solenoid hydraulic valve with a pulse width modulation (PWM) signal, control of the pressure in a certain volume is frequently used in various applications. However, the pressure built-up according to the duty ratio and carrier frequency of the PWM signal is not so well understood. In order to clarify the characteristics of 2-way valve hydraulic pressure control systems, in this paper two formula fur the mean and ripple of the load pressure were derived through theoretical analysis. And the accuracy of the derived formula were verified by comparison with the experimental test result. Generally 2-way valve systems are constructed as a bleed-off circuit, while 3-way valves are used as a control element in a meter-in circuit pressure control system. In a bleed-off circuit, the system supply pressure from a hydraulic power pack does not remain constant, but changes according to their external load. In turn, the relief valve in the hydraulic power pack reacts accordingly showing complicated dynamic behavior, which makes an analytical study difficult. In order to resolve the problem, simple but accurate empirical dynamic models fer a bleed-off system were used in the course of formula derivation. As the result, selection criteria for two major control parameters of the driving signal is established and the basic strategy to suppress the unnecessary pressure fluctuation can be provided for a hydraulic pressure control system using a 2-way on/off solenoid valve.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.94-102
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• 1995

The active control system of structural vibration using a hydraulic actuator is developed. The developed system consists of three parts : a hydraulic unit, an actuator unit and a control unit. Structural vibration is sensored by the accelerometer attached to the structure and reduced by the optimally controlled motion of active mass giving anti-phase inertia force to the structure. It is experimentally confirmed that the vibration level of model structure is reduced to about 1/6 by the developed active control system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.44-52
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• 1994

Load simulator is essential to test and quality the performance of various control systems. It is good time to introduce a method to design and analyze the load simulator or since many research centers and industrial companies are trying to buy or design the load simulator. The stability, accuracy and response speed of the simulator are represented by the system parameters such as the hydraulic motor characteristics, the servovalve characteristics, supply pressure, rotational inertia, rotational spring constant, sensor and controller gains. Two design examples are shown here. A load simulator for a position control system and that for a velocity control system are designed. The goodness of the proposed method is verified by the digital computer simulations.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.11
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• pp.1153-1160
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• 2013

SMISMO valve configuration is now starting to draw attention of the researchers of the construction equipment industry to increase the fuel efficiency of their equipment like excavators and wheel-loaders. An open-loop control strategy for grading operation of hydraulic excavator systems using SMISMO valve configuration is investigated in this paper. Tabor's algorithm for 1 d.o.f. SMISMO system under the assumption of quasi-static operation is revealed as not adequate for multi d.o.f. system with large moment of inertia even though the motion of the system is slow. New parameters are proposed in this paper. It modifies Tabor's open-loop control strategy for the grading operation of hydraulic excavators using SMISMO valve configuration. A simulation-based parameter tuning method is also proposed. It uses GA (Genetic Algorithm) to find the best parameter values. Simulation study for a practical hydraulic excavator shows the validity of the proposed open-loop control strategy.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.36-42
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• 2016

A cylinder control system of the conventional construction machine has been controlled by hydraulic spool valves. This system is low-cost but system efficiency is not high. Recently, to improve this, all valves are controlled electronically and independently. Bu and Yao suggested four way electronic hydraulic control valve system. It is called IMVT(Independent Metering Valve Technology). The purpose of the study is to find proper IMV pressure control method for excavator and to validate excavator's bucket regeneration energy effect by controlling the IMV system. In this paper, we mathematically describe the bucket system of excavator first. And then, based on these results, we design the control system which is divided into two operations(none regeneration or regeneration).The results of the experiment show the desirable performance and usefulness of the designed control system.

• Journal of Drive and Control
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• v.14 no.4
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• pp.37-44
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• 2017

This paper introduces a control algorithm for trajectory control of an electro-hydrostatic rotary actuator. A key feature of this paper is that an adaptive PID based on sliding mode is used to control the nonlinearity and uncertainty factor of single input/output system. Accurate knowledge of rotary actuator angle can result in high-performance and efficiency of electro hydraulic system. First, the position control is formulated using the adaptive PID with sliding mode technique and uncertainties in the hydraulic system. Second, the controller can update the PID gains on-line based on error caused by external disturbance and uncertain factors in the system. Finally, three experimental cases were studied to evaluate the proposed control method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.131-144
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• 1995

This paper presetns modifications of a hydraulic shovel to robotize, and we derive a dynamic model of the hydraulic shovel arms,and hydraulic analysis are discussed . Then , our purpose is making to imitate a target railroad line of the grinder position by the PID control. Moreover, to determine the gains of the PId controller, we referenced the Ziegler and Nichols' method. In this paper, we demonstrated that the PID control is available for system. These results indicated the possibility of practical use fo the deburring robot with the hydraulic shovel.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.18-24
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• 2009

This paper shows the result of development about the revolution system of azimuth thruster which of power is less than 250kW for small ship. Advanced Azimuth revolution system can revolve propeller and rudder from 360 degree so that this system for vessel maneuvering can be excellent of propulsion effectively. Fluid power control system for azimuth thruster is designed with PID control system by using CEMTool/SIMTool program. And the actuator used for servo valve can control rudder angle, pressure and direction. The first, We had a test for the angle control of revolution system. The result of angle control confirmed that it has the good efficiency from experiment result of time input degree $30^{\circ}$, $90^{\circ}$ and $180^{\circ}$. The second, We had to a test for the pressure characteristic of hydraulic motor. As a result, We confirmed the maximum pressure 3.5MPa and steady state 0.7MPa nom experiment result of time input degree $30^{\circ}$. In this paper, it is identified the pressure characteristic of hydraulic motor and angle control for azimuth thruster by AMESim, and it has been confirmed the usefulness of AMEsim modeling was verified by comparison between AMESim simulation results and experiments results.

• Journal of Drive and Control
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• v.2 no.2
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• pp.8-12
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• 2005