• International Journal of Fluid Machinery and Systems
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• v.9 no.1
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• pp.39-46
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• 2016

A high frequency hydraulic rock drill drifter with sleeve valve is developed to use on arm of excavator. In order to ensure optimal working parameters of impact system for the new hydraulic rock drill drifter controlled by sleeve valve, the performance test system is built using the arm and the hydraulic source of excavator. The evaluation indexes are gained through measurement of working pressure, supply oil flow and stress wave. The relations of working parameters to impact system performance are analyzed. The result demonstrates that the maximum impact energy of the drill drifter is 98.34J with impact frequency of 71HZ. Optimal pressure of YZ45 rock drill is 12.8 MPa-13.6MPa, in which the energy efficiency reaches above 58.6%, and feature moment of energy distribution is more than 0.650.

• Journal of Drive and Control
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• v.13 no.2
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• pp.26-33
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• 2016

This paper describes of a mathematical and real experimental analysis for a walking robot which uses servo valve driven hydraulic actuator. Recently, many researchers are developing a walking robot based on hydraulic systems for the difficult and dangerous missions such as walking in the rough terrain and carrying a heavy load. In order to design and control a walking robot, the characteristics of the hydraulic actuators in the joint through the view point of walking such as controllability and backdrivability must be analyzed. A general mathematical model was used for analysis and proceeds to position and pressure changes characteristic of the input and backdrivability experiment. The result shows the actuator is a velocity source, had a high impedance, the output stiffness is high in contact with the rigid external force. So stand above the controller and instruments that complement the design characteristics can be seen the need to apply a hydraulic actuator in walking robot.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.12
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• pp.698-704
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• 2005

Passive suspensions with fixed design constants are very restrictive in the inherent suspension problem, the trade-off between the ride quality and the suspension travel. Active suspensions are used to solve some drawbacks of passive suspensions. In this paper, we propose a controller design for vehicle active suspensions considering variable driving conditions. Our controller estimates the current driving conditions by detecting the road frequencies gotten from Fourier Transform and decides which factor must be emphasized between the ride quality and the suspension travel. In one case of focusing on the ride quality, we use the skyhook control law and in the other case of focusing on the suspension travel, the double skyhook control law is used. The control law modified by various road situations outputs the reference force value the electro-hydraulic actuator in active suspension system must generate. To track the reference force, we adopt the sliding control law which is very useful in controlling the nonlinear system like the electro-hydraulic actuator.

• Journal of Drive and Control
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• v.17 no.1
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• pp.37-43
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• 2020

An intelligent excavator can be divided into Machine Guidance (MG), semi-automatic, and unmanned by technology. The MG technology excavator is equipped with a tilt sensor on each link of the excavator and a GPS is installed on the excavator body to inform the user of the position of the excavator bucket end. Machine control (MC) technology that assists the user's work can be divided into semi-automatic and fully automatic technology. The semi-automatic MC equipment has already been commercialized by Komatsu and Caterpillar. The MC excavator is equipped with an electro-hydraulic system, sensors and controllers to control the excavator bucket end according to the user's needs. In this study, the semi-automated excavator modified based on manual excavator, is equipped with an electro-hydraulic system, a controller system, multi-sensors and a control algorithm is developed to assist in excavation work such as leveling and grading. By applying the developed technology, it was possible to confirm productivity improvement compared to manual digging and leveling work. In the future, further research to improve the accuracy of the hydraulic precision control and collaborative work with heterogeneous construction equipment such as dump truck and automated collaboration tasks technology could be developed.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.132.4-132
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• 2001

Field robot represented by excavator can be applied for various kinds of working in manufacturing, construction, agriculture etc. because of the flexibility of its multi-joint mechanism and the high power of hydraulic actuators. In general, the dynamics of field robot have strong coupling, various kinds of non-linearity, and time varying parameters according to working conditions. Therefore, it is very difficult to describe the system well, and design controller systematically based on its model. This paper established the mathematical model of field robot driven by electro-hydraulic servomechanism and constructed the adaptive control system robust to external load variations. The proposed control system for the field robot was evaluated by the computer simulation, and the performance results of trajectory tracking were compared with that of PID control system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.496-499
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• 1997

Field robot represented by excavator can be applied for various kinds of working in manufacturing, construction, agriculture etc. because of the flexibility of its multi-joint mechanism and the high power of hydraulic actuators. In general, the dynamics of field robot have strong coupling, various kinds of non-linearity, and time-varying parameters according to working conditions. Therefore, it is very difficult to describe the system well, and design controller systematically based on its model. This paper established the mathematical model of field robot driven by electro-hydraulic servomechanism and constructed the adaptive control system robust to external load variations. The proposed control system for the field robot was evaluated by the computer simulation and the performance results of trajectory tracking were compared with that of PID control system.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.357-364
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• 2001

This study deals with the effect on non-martensitic layer on the fatigue strength in carburized gear. The test gears are carburized, then treated by the combination of chemical polishing and electro-polishing. Carburization treatment is used widely on parts of power transmission system like surface hardened layer to improve fatigue strength. Carburized gears are observed using a scanning electron microscope(SEM) to determine the characteristics of crack initiation mechanism in the surface layer. The constant street amplitude fatigue test is performed by using and electro-hydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. The effect of non-martensitic layer on the fatigue strength is clarified.

• Journal of Drive and Control
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• v.9 no.3
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• pp.16-22
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• 2012

Nowadays, electro hydrostatic actuator (EHA) has shown great advantages over the conventional hydraulic actuators with valve control system. This paper presents a position control for an EHA using a modified back stepping controller. The controller is designed by combining a backstepping technique and adaptation laws via special Lyapunov functions. The control signal consists of an adaptive control signal to compensate for the nonlinearities and a simple robust structure to deal with a bounded disturbance. Experiments are carried out to investigate the effectiveness of the proposed controller.

• Journal of Drive and Control
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• v.14 no.4
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• pp.61-70
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• 2017

In this study, an extended-state-observer (ESO) based non-linear servo control is introduced for an electro-hydrostatic actuator (EHA). Almost hydraulic systems not only are highly non-linear system that has mismatched uncertainties and external disturbances, but also can not measure some states. ESO that only use an output signal can be used to compensate these uncertainties and estimate unmeasurable states. To improve the position tracking performance, the barrier Lyapunov function (BLF) that can guarantee an output tolerance is introduced for the position tracking error signal of back stepping control procedures. Finally, the proposed servo control is compared with the proportional-integral (PI) control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.3869-3875
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• 2012

In this study, mathematical modeling and experimental analysis were executed in order to evaluate the valve dynamic characteristics when the hydraulic pressure applied. High pressure on the master cylinder effects on the valve dynamic characteristics have been analyzed. The pulsation pressure generated in hydraulic systems causes noise, vibration and odd effect to the system. To reduce the pulsation pressure, high frequency PWM control of 20KHz was attempted. Also, an analytic method is proposed for the resultant forces of electromagnetism and hydraulic pressure generated in the real vehicle electro stability program. Consequently, results of solenoid valve dynamic characteristics analysis derived in the study can be confirmed criteria for the optimal control of electronic stability program system.