An optimized finite element model was applied to simulate the fluid transients in pipelines. The model is a distributed parameter model of pipeline dynamics, which is written as a state space equation. In this paper, an experiment of the fluid transients was carried out to examine simulation results of the optimized finite element model. Transient pressures in a closed-end pipe were measured and the pressures at the boundary conditions were input to the model for simulation. A comparison of simulation and experimental results has revealed the accuracy, limitations and convenience of the model.

抄録全体を表示

Generally, the electro-hydraulic servovalve for positioning control in hydraulic servo systems is used as a flow control valve. This system often needs to have dual performance (quick traverse and high accuracy of positioning) for positioning control. Therefore it is desirable that the above-mentioned servovalve has a low flow gain near its neutral spool position.
In order to realize a servovalve with this low flow gain, a hybrid-type servovalve has been newly created. This servovalve has an under lap at the oil supply port and an over lap at the oil return port in the spool valve, and it is possible to have a desirable flow gain near its neutral spool position by combining a suitable under lap and over lap.
When this servovalve is installed in the hydraulic servo system, the time constant of this system is affected by the controlled deviation near the set point in the case of feedback control. So it is necessary to clarify the dynamic characteristics of the hydraulic system installed with this servovalve, and the effect of its lap and the amplitude of input current on the time constant.
The purpose of this paper is to clarify the effect of the lap of the hybrid-type servovalve and the amplitude of input current on the time constant of the hydraulic servo system, and to obtain instruction for the design of this servovalve for practical application.
First, we analyze the relationship between output flow characteristics of the hybrid-type servovalve and the spool displacement, and obtain the dead time component of servovalve. Secondly, we theoretically obtain the transfer function of the hydraulic servo system considering the transfer characteristics of each element of the system, and deduce the effect of the lap on the time constant of the system. Moreover, as a result of the analysis, it becomes clear that the value of time constant is inversely proportional to the amplitude of the input current.

抄録全体を表示

Recently, electro-hydraulic servo systems with a servovalve for positioning control have been applied to various kinds of manufacturing systems. This system often needs to have dual performance (quick traverse and high accuracy of positioning) for positioning control. So a hybrid-type servovalve has been newly created to realize a servovalve suitable for positioning control.
In the previous paper, we analyzed the relationship between output flow characteristics of this servovalve and spool displacement, and obtained the transfer function of the hydraulic servo system installed with this servovalve. Furthermore, we theoretically clarified the effect of its lap and the amplitude of input current on the time constant of the system.
The purpose of this paper is to show the validity of the above-mentioned theoretical characteristics of this system, and to clarify frequency characteristics of the system.
First, we analyze frequency characteristics of the system. Secondly we theoretically make it clear that the value of the time constant is proportional to load friction. Finally, we obtain frequency characteristics of the hydraulic servo system using a hybrid-type servovalve experimentally, and show the validity of theoretical characteristics in comparison with experimental results

抄録全体を表示

In this study, the effect of a flange on the compensation of flow force in the main poppet valve of the hydraulic semi-active damper has been studied via numerical simulation. First, validity of the numerical analysis was confirmed by comparison between the computational and experimental results. Then, the mathematical models for the flow force acting on the poppet valves both with or without flange for converged flow were obtained based on the computational results. Introducing these mathematical models to the equivalent model of the whole semi-active damper system in the previous paper, the effects of the flow force on the stability of the damper system were investigated. As the result, the flange improves the stability of the system when the pressure difference and the main valve displacement are relatively large.

抄録全体を表示