• 한국공작기계학회논문집
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• 제10권1호
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• pp.120-126
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• 2001

This study deals with a flow and pressure ripple characteristics for a hydrostatic transmission(HST) consisting of a vari-able axial piston pump connected in an open loop to a fixed displacement axial piston motor. These flow ripples produced by pump and motor in HST interacts with the source impedances of the pump or motor and dynamic characteristics of the connected pipeline, and results in a pressure ripples, Pressure ripples. Pressure ripples in HSP is major source of vibration, which can lead to fatigue failure of components and cause noise. In this paper, the flow ripples generated by a swash plate type axial piston pump or motor in HST are measured by making use of hydraulic pipeline dynamics and the measured pressure data at two points along the pipeline. By using the self-checking functions, the validity of the method us investigated by comparison with the measured and estimated pressure ripples at the halfway section of the pipeline, and good agreement is achieved.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1998년도 동계 학술대회 논문집
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• pp.422-428
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• 1998

• 유공압시스템학회논문집
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• 제2권4호
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.

• International Journal of Fluid Machinery and Systems
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• 제8권4호
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• pp.318-326
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• 2015

A valve-less electro-hydraulic servo steering device (short: VSSD) for ships was chosen as a study object, and its mathematic model of hydraulic shock was established on the basis of flow properties and force balance of each component. The influence of system structure parameters, changing rate of motor speed and external load on hydraulic shock strength was simulated by the method of numerical simulation. Experiment was designed to test the hydraulic shock mathematic model of VSSD. Experiment results verified the correctness of the model, and the model provided a correct theoretical method for the calculation and control of hydraulic shock of valve-less electro-hydraulic servo steering device.

• Journal of Power Electronics
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• 제9권3호
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• pp.491-498
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• 2009

The hydraulic-oil pump is widely used for building machinery, brake systems of vehicles and automatic control systems due to its high dynamic force and smooth linear force control performance. This paper presents a novel direct instantaneous pressure control of the hydraulic pump system with SRM drive. The proposed hydraulic pump system embeds the pressure controller and direct instantaneous torque controller. Due to the proportional relationship between pump pressure and torque, pressure can be controlled by the motor torque directly. The proposed direct torque controller can reduce inherent torque ripple of SRM, and develop a smooth torque, which can increase the stability of the hydraulic pump. The proposed hydraulic pump system has also fast step response and load response. The proposed hydraulic pump system is verified by computer simulation and experimental results.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.201-211
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• 2002

In this research, we are trying to research about hydraulic system design and vehicle dynamic modeling far the development of the tire roller. The reason why we would like develop it is that tire roller is one of the most useful machine for the road construction site and application other construction equipments. Here, we conceptualize the new hydraulic system and derive the equations of motion fur dynamic analysis and also investigate system modeling by using a DAQ board. We design the hydraulic circuit of steering and traction mechanism system. This design can be used to create virtual prototypes of construction equipment. So, we studied tire roller to integrate development technology. In system analysis, we formulate hydraulic traction system model and hydraulic steering system model. Also, we integrate DAQ system to acquire experimental results in real tire roller equipment.

• 드라이브 ㆍ 컨트롤
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• 제18권4호
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• pp.43-51
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• 2021

In this study, we designed a hydraulic propulsion propeller system that allows dredged materials to be carried out by the dredger to the disposal place. The proposed model equation was used to formulate the screw propeller specifications considering the resistance to the dredger, and the quantitative specifications of the hydraulic propulsion propeller were determined through the numerical analysis programs. In addition, based on the proposed results, we were able to determine the specifications of the hydraulic system that was used for the hydraulic motor in the propulsion propeller device and then manufactured the hydraulic propulsion propeller. To guarantee the reliability of the proposed model equation, an external testing agency was invited and verified that the hydraulic propulsion propeller based on the proposed model equation could achieve the target speed in the dredger.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1462-1469
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• 1997

This study presents a genetic algorithm-based method for optimizing control parameters in fluid power systems. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics. A genetic algorithm seeks control parameters maximizing a measure that evaluates system performance. Five control gains of the PID-PD cascade controller fr an electrohydraulic speed control system with a variable displacement hydraulic motor are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that optimization of the five gains by manual tuning should be a task of great difficulty and that a genetic algorithm is an efficient scheme giving economy of time and in labor in optimizing control parameters of fluid power systems.

• 동력기계공학회지
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• 제4권3호
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• pp.55-61
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• 2000

In this study, a new design of an one-body type of an unbalanced-fixed- displacement type vane pump combined with an induction type electric motor was suggested. By the application of the new design scheme, it was possible to reduce the number of parts of the pump system and to cut down the volume of power package than that of already-used products. The case in this study enabled efficient heat transfer and electricity insulation of hydraulic fluid. Thus oil moves through the inside of the package for cooling and returns to the reservoir. Because of this design, it was difficult to measure the shaft-input torque. Therefore the package overall efficiency in the paper was evaluated with a ratio of hydraulic power and electric power.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.290-295
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• 2001

The surface morphology of oil-lubricated surface for hydraulic piston motor is believed to be extremely effective in contact mechanics. adhesion, friction and wear. In order to describe morphology of various rubbed surface on driving condition, the wear test was carried out under different experimental conditions in oil-lubricated system. And fractal descriptors was applied to rubbed surface of hydraulic driving material with image processing system. These descriptors to analyze surface structure are fractal dimension. Surface fractal dimension can be determined by sum of intensity difference of surface pixel. Morphology of rubbed surface can be effectively obtained by fractal dimensions.