• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.49-56
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is a combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. In this paper the effect of transformer is studied. Multiple closed loop controllers with displacement feedback of variable pump/motor, speed feedback and position feedback of cylinder are used. The efficiency and energy consumption when cylinder is driven up and down is calculated by simulation. Simulation results show that considerable energy saving is achieved by choosing load ratio, circuit type and supply pressure.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.917-922
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1075-1080
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• 2007

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is a combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. In this paper the effect of transformer is studied. Multiple closed loop controllers with displacement feedback of variable pump/motor, speed feedback and position feedback of cylinder are used. The efficiency and energy consumption when cylinder is driven up and down is calculated by simulation. Simulation results show that considerable energy saving is achieved by choosing load ratio, circuit type and supply pressure.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.1-8
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• 1999

This paper experimentally investigates the steady shear behaviors of electro-rheological(ER) fluids under flow mode at high pressure level. As for the ER fluid to be tested, two types of ER fluids are employed; water-based ER fluids (ERF 1, ERF 2) and water-free ER fluid(ERF 3). The water-based ER fluids are composed inhousingly, and the concentrations of dispersed particles are 20 wt% and 30 wt% for ERF 1 and ERF 2, respectively. To generate the flow mode at high pressure, an experimental apparatus operated by two-way hydraulic cylinder is constructed and utilized. The pressure difference is measured by the pressure sensor, while the flow rate is calculated using the measured data of the displacement sensor(LVDT). Consequently, the shear stress and shear rate are distilled by incorporating the measured data; the pressure difference and the flow rate.