In case of charging of or discharging from a chamber with a compressible fluid, the temperature change of fluid in chamber affects pressure change as a result of convective heat transfer within the chamber wall. Therefore, in a pressure control system using a compressible fluid, the temperature change has an effect on the control characteristics of the pressure.
This study analyzed how a temperature change, owing to heat transfer with the chamber wall, can affect the control characteristics of the pressure in it with a normal chamber and isothermal chamber. An isothermal chamber is a chamber that can almost realize isothermal conditions due to the larger heat transfer area and heat transfer coefficient by filling it with steel wool. As a result, this study could confirm that a slight temperature change can affect the pressure control characteristics and dynamic characteristics of pressure response, making it better by a suppression of the temperature change in a chamber.

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Recently, the fuzzy control algorithm is frequently applied to various kinds of systems due to its simple algorithm, good adaptability to complex and nonlinear systems, etc. One of the problems when applying the fuzzy control algorithm is the tuning method of fuzzy control parameters for obtaining the optimum conditions. This study deals with a self-tuning fuzzy controller (STFC) applied to an electro-hydraulic servo system. The STFC has a hierarchical structure consisting of an algorithm being identical to a fuzzy controller at the lower loop and a tuning algorithm assisting the performance evaluation and parameter modification function at the upper loop. As for the algorithm for tuning at the upper loop, another fuzzy logic was adopted for constructing a fuzzy self-tuner. The whole procedure of STFC was repeatedly performed until an acceptable control level was achieved. The STFC must be able to assess its performance in order to improve its control strategy. The basic functions of STFC can be summarized as follows : (a) to provide appropriate control action while evaluating the performance, (b) to modify the control action based on this evaluation.
It could be verified by experiment and digital simulation that the STFC developed in this study was useful and effective for the control of the electro-hydraulic servo system.

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The two-and three-dimensional pressure and velocity distributions around restrictors in pipes are numerically obtained by applying the finite volume method with k-ε turbulence model. As the numerical method is not applicable to flows with phase change, the results correspond to the fluid with an enough tensile strength. However, for the case of three kinds of orifices whose experimental results have already been reported, the minimum pressure which appears just after the inlet edge of orifices is shown to be able to explain the facility of cavitation occurrence.

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This paper shows a simple method to identify the approximate transfer function of an instrument as a standard 2nd order delay system, and illustrates its application for an electro-hydraulic servo-valve. It is shown that the dynamic performance parameters, i.e., the damping ratio ζ_υand undamped natural frequency ω_nυ of the electro-hydraulic servo-valve can be identified by analyzing the self-excited oscillation waves in the bang-bang integrated flow-rate control system.
The experimental setup of the self-excited vibration system consists of an electro-hydraulic servo-valve, a flow-rate sensing system, an integrator and nonlinear electro-circuit. The dynamic performance parameters ζ_υ ω_nυ of the electro-hydraulic servo-valve under general operational conditions are obtained by means of the self-excited vibration system, and in addition, the frequency responses of the hydraulic servo-valve are measured. Then, the frequency characteristics of the identified transfer function and of the measured data are compared to confirm the coincidence of both characteristics within the band width where the phase angle of frequency response becomes -75--90°.

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