• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2588-2595
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• 2013

In a traditional hydraulic elevator, elevator car is descended by down control valve, and the oil hydraulic energy must be lost during the descending stroke. In this paper, the performance characteristics of the hybrid type energy saving unit, is used to save the hydraulic energy which is lost during the descending stroke, for a hydraulic elevator are studied. The energy can be reused as the auxiliary power. The results show that the performance characteristics, such as the pressure, flow rate, output current and voltage, efficiency, and the energy recovery rate of the unit are stable and good as the energy recovery rate is 54%, and the energy saving unit is useful to reuse the saved energy during the descending stroke of elevator car. Also, it was confirmed that the energy saving unit can be deployed on a commercial scale.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.231-237
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• 2007

The torque ripple of the hydraulic pumps for the Electro-hydrostatic Actuators can disturb the cylinder position control under slewing speed operation condition. In principle, the periodic change of the reaction torque generated by a piston type pump is highly dependent on the waveform of its cylinder chamber pressure. In case of uni-directional pumps operating at constant speed, the transient overshoot and rising slope of the cylinder pressure can be adjusted by the precompression angle and notch shape of their valve plates. Therefore, the influence of the valve plate geometry on the torque ripple magnitude of a bent-axis type piston pump for EHA application was investigated in this study. The results showed that any improvement of the torque ripple of such a bi-directional pump can not be achieved by modifying the valve plate geometry, regardless of its operation speed.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.533-540
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• 2013

Prime movers in engine rooms inherently are much affected by the adjustment of their governors for the steady state and transient properties, consequently requiring that marine engineers shall be well familiar with the way to manage governor dials for normal operation. The hydro-mechanical governors basically have different control characteristics and adjustment parameters of stability from digital governors. The former include compensation mechanism using dash pot while the control algorithm of the latter is usually based on the PID action. This study is for configuring a simulation module to let trainees practice how to adjust dials for stability on hydraulic governors in the view that the practice by real governors and engines is time consuming and high cost for operation. The governor module includes the adjusting points such as speed set, speed droop, needle valve and compensation pointer with engine module of $2^{nd}$ order coupled. The results of simulation showed satisfactory responses as a training tool for the adjustment of control parameters.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.55-64
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• 2002

Due to the friction characteristics of cylinders and the rail of a passenger car, in the system actuated with hydraulic systems, there exist dead zones, which can not be controlled by a PID controller. In this paper, the friction characteristics of a cylinder is examined, which may cause the abrupt increase of the acceleration in the zero-crossing speed region. To overcome the drawbacks of a PID controlled hydraulic system, a zooming fuzzy logic controller is designed and finally an improved hybrid controller is Proposed. The proposed controller is composed of the PID controller and the zooming fuzzy controller. The effectiveness of the proposed control scheme is shown by simulation and experimental results, In which the proposed hybrid control method yields good control performance not only in the zero-crossing speed region but also In the overall control region including steady-state region.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.211-215
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• 1995

전기유압식 좌심실 보조장치에서 모터 전류 파형을 정보로 하여 작동기의 이완기 속도를 조절함으로써 좌심방으로부터 유입되는 혈류량을 조절하는 알고리즘을 개발하였다. 전기 유압식 좌심실 보조장치에서는 혈액의 유입이 능동적으로 이루어지므로, 좌심방 함몰로 인한 심근 손상 및 외부 공기 유입으로 인한 색전증을 방지하기 위해 유입혈류량을 현재 좌심방 내의 상태에 따라 적절히 조절해 주어야 한다. 좌심방 내의 혈액량 정도는 혈액을 유입해내는 작동기의 이완기 동작 시에 소모되는 에너지 크기에 반영되고, 작동기를 구동하는 모터에 들어가는 전류의 크기는 작동기에 공급되는 에너지에 비례하므로, 이 전류 파형의 정보들을 통해 좌심방 내의 상태를 추정해 볼 수 있다. 본 논문에서는 퍼지로직을 적용하여 모터 전류 파형의 이상 유무를 판단한 뒤 이에 따라 작동기의 이완기 속도를 조절하는 알고리즘을 개발하여 모의순환장치 실험을 통해 그 실효성을 검증한 결과를 정리하였다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1995.10b
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• pp.387-392
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• 1995

전기 유압식 좌심실 보조장치에서 모터 전류 파형을 정보로 하여 작동기의 이완기 속도를 조절함으로써 좌심방으로부터 유입되는 혈류량을 조절하는 알고리즘을 개발하였다. 좌심실 보조장치(Left Ventricular Assist Device, LVAD)는 허혈성 심장질환 등으로 좌심실 의 혈액 박출 기능이 저하된 환자에게 시술하여 정상 상태의 심박출량을 유지할 수 있도록 하는 보조 혈액 박출 기능이이다. 전기 유압식 좌심실 보조장치에서는 혈액의 유입이 능동 적으로 이루어지므로, 좌심방 함몰로 인한 심근 손상 및 외부 공기 유입으로 인한 색전증을 방지하기 위해 유입혈류량을 현재 좌심방내의 상태에 따라 적절히 조절해 주어야 한다. 좌 심방 내의 혈액량 정도는 혈액을 유입해 내는 작동기의 이완기 동작 시에 소모되는 에너지 크기에 반영되고, 작동기를 구동하는 모터에 들어가는 전류의 크기는 작동기에 공급되는 에 너지에 비례하므로, 이전류 파형의 정보들을 통해 좌심방내의 상태를 추정해 볼 수 있다. 본 논문에서는 퍼지로직을 적용하여 모터 전류 파형의 정보들을 통해 좌심방 내의 상태를 추정 해 볼 수 있다. 본 논문에서는 퍼지로직을 적용하여 모터 전류 파형의 이상 유무를 판단한 뒤 에에 따라 작동기의 이완기 속도를 조절하는 알고리즘을 개발하여 모의순환장치 실험을 통해 그 실효성을 검증한 결과를 정리하였다.

• 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.

• Journal of Drive and Control
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• v.18 no.3
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• pp.8-15
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• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• Journal of Drive and Control
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• v.20 no.4
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• pp.35-44
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• 2023

This study aimed to analyze the performance of hydraulic systems for dental chair when long working hours makes the temperature of hydraulic fluid rise. The study was carried out in the following manner. First, 'cylinder's clearance' was reflected in the three kinds of hydraulic circuits, which were developed through the preceding study, in order to analyze oil leak. Second, 12 cases of simulations comprised of the up and down of cylinders were carried out. Third, it was determined whether the cylinder velocity of dental chair surpasses 1cm/s required in the development even in the hydraulic fluid temperature of 60℃. In conclusion, this study used SimulationX to verify the performance stability at high temperatures using three types of hydraulic circuits designed to develop a Korean unit chair.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.101-108
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• 1999

This paper was undertaken to do morphological analysis of wear particles for sliding members hydrauric rotary acuator. The lubricating wear test was performed under different experimental conditions using the wear test device and wear specimens of the pin on disk type was rubbed in paraffinic base oil by three kinds of lubricating materials, varying applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) are used for morphological analysis of wear particles. The results showed that the four shape parameters of wear particles depend on a kind of the lubricating materials. It was capable of presuming wear volume for three kinds of materials on driving time.