This paper deals with a new type of miniature air compressor that mainly consists of a linear electromagnetic actuator, electronic drive circuit, cylinders, and intake and output valves. The cylinders are directly driven by the linear electromagnetic actuator without other mechanisms so it can be made smaller in size. The two rotors type balance mechanism is used to reduce the vibration of the compressor. The characteristics of this miniature compressor are experimentally investigated. In order to obtain better characteristics, the input signal frequency should be adjusted to make the compressor operate at a resonant rate as the output pressure changes. Two adjusting methods are proposed and their effectiveness is proven through experiments. By directly controlling the compressor the speed of pressure increase can be regulated and a constant pressure can also be supplied in the tank. These possibilities are confirmed by experimental results.

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In previous research we proposed to quantify available energy of compressed air by exergy. In this paper we discuss the distribution of available energy supplied to a pneumatic cylinder in cyclic actuation. First, we examined energy distribution for ideal actuation of cylinder driven by a meter-out and meter-in circuit It is clarified that over half of supplied available energy is used for mechanical work to load and for velocity control of the piston, and remaining energy is exhausted without being used. For actual actuation the method for calculating distribution of available energy is established and this distribution is clarified by simulation of cylinder responses. It is found that the available energy for piston acceleration, work against internal friction and loss in heat transfer are relatively small. As a result, the paper concludes that utilization of exergy is feasible and recommendable for analyzing distribution of available energy of compressed air in pneumatic equipment.

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A simulation model of a water-hydraulic molding press was developed, considering static and dynamic characteristics of a power unit, a ram cylinder, a servo valve, lift cylinders and a PLC controller. Some experimental data of water-hydraulic components were included. Simulation tests were performed to confirm a series of press operations. The simulated results were compared with results obtained from an experimental water-hydraulic molding press. Simulated results showed good agreement with the experimental results.

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Transient responses are theoretically given for laminar flows in tapered viscoelastic circular fluid transmission lines. The basic equations for the analysis are transfer matrices, which were derived based on a fluid line model in which the frequency-dependent effect of viscosity was taken into consideration. In the matrices, a modified version of the Voigt mechanical model is applied to the viscoelastic pipe wall model. The responses to stepwise changes in pressure or flow rate are theoretically obtained under open-end and closed-end conditions. It is confirmed that the theoretical results agree well with simulated ones, when the rate of divergence (or convergence) of the pipeline is very small.

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