In a hydraulic system, a displacement pump inevitably produces flow pulsation which becomes a main source of pressure pulsation. This source pulsation travels throughout the working oil in the passageways inside hydraulic components as an incident wave, and then is reflected by both of these components and the termination of a circuit. The standing waves of pressure pulsation arise from the interference of the incident and reflected waves. It has been well known that the amplitude of pressure pulsation becomes extremely high when the frequency of the source flow pulsation coincides with the resonance frequency of the standing waves. Therefore pump rotational speed or length of a connecting pipe should be designed so as to avoid the resonant modes of the standing waves. The final aim of this paper is to establish design tips for these parameters and clarify the standing wave characteristics in a pipe-line. In particular, the influence of the termination characteristics of the circuit on the resonant mode of the standing waves is investigated both numerically and experimentally.

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The purpose of this study is to estimate fluid transients in a pipe using measured pressure values of three points. In this study, method of estimating fluid transients by combining a steady-state Kalman filter and an optimized finite element model of pipeline dynamics is proposed. In this method, fluid transients can be estimated without accurate setting of initial conditions. Moreover, not only the flow rate but also the pressure in a pipe can be estimated by the Kalman filter. In this paper, fluid transients in a pipe were estimated off-line by using experimental values in order to show basic performance of the Kalman filter. In this off-line estimation, estimation results show good agreement with experimental results. Moreover, it was confirmed that the error between the estimation value and the measured value was decreased by the Kalman filter when the initial value was not set accurately. In addition, covariances of sensor noise and system noise, which are parameters of the Kalman filter, were investigated. For comparison, an off-line remote measurement method for unsteady flow and the method of characteristics were applied to the same data. Estimation results of the Kalman filter show good agreement with the result of the method of characteristics and the remote measurement method for unsteady flow.

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An actuator which has softness is necessary for small equipment used in environments that coexists with people such as welfare equipment and a power assistance device. A peripheral equipment such as a compressor is needed though an existing device that uses air pressure and oil pressure has flexibility. In addition, enlargement and the noise of the system are feared. Moreover, when an electromagnetic motor is used and controlled, there is a problem in that control is complex though the system is small. In this study, a new actuator that is capable of soft motion was developed by applying the EHD phenomenon. When the EHD phenomenon is applied to the actuator, an actuator with simple structure and a small system can be produced. In this study, firstly, a pump using the EHD phenomenon was produced. Next, an actuator which converts pressure into swing motion was produced. Also, the characteristics of an actuator that used the EHD phenomenon by the driving speed and the output torque was evaluated.

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