Pneumatic pipes have a significant effect on the behavior of pneumatic cylinder systems. However, the influence of pipes on pneumatic cylinders has not been studied sufficiently. Up to now, pipes in pneumatic cylinder systems have been treated as a restriction using an equivalent effective area. This method does not consider the volume of the pipes or pressure propagation so that the motion time of a cylinder, which is very important for manufacturing products, can not be calculated correctly.
This paper describes simulation of pneumatic cylinder systems including the influence of pipes between the electromagnetic valve and cylinder. A previous proposed model applied for the pneumatic pipe-chamber system is extended for applications in the simulation of pneumatic cylinder systems. Experiments were carried out with cylinders of different sizes and pipes of different lengths. The calculated results are in close agreement with the experimental results. The time motion can be obtained more precisely compared with effective area methods and the results show the effectiveness of the simulation.

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A DSP (digital signal processor) and a feedforward compensation method called ZPETC (zero phase error tracking control) are applied to an electrohydraulic servo system with a nonsymmetrical cylinder to improve on the frequency responses of the system. ZPETC is a control algorithm, rendering the transfer function between the input and actual output close to unity. This algorithm assumes the controlled system to be linear. However, the relationship between the input and flow rate at the servo valve is nonlinear. Another nonlinear factor is added when the cylinder is nonsymmetrical. Therefore, these nonlinearities should be removed. The nonlinearity of the servo valve is compensated for by using the detected load pressure, and the effect of the nonsymmetrical cylinder is compensated for by using the detected sign of the input. The DSP performs the calculations for ZPETC and for linearization. The effects of improving the frequency responses of the system by this digital signal processing technique are investigated.

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Experimental studies are carried out to clarify the effects of ambient pressure on the structure and erosive property of an ultra-high-speed cavitating jet. Tap water is pressurized up to 118 Mpa and injected into a test cell at specified constant pressure. Specimens of aluminum alloy are used for erosion tests. The structure of the ultra-high-speed cavitating jet is observed by instantaneous photographs and high-speed photography. The damaged surface of the specimens are examined by using a scanning electron microscope and mechanism of the erosion by impingement of the ultra-high-speed cavitating jet is investigated.

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In this paper, the application of a self-tuning fuzzy control method for electro-hydraulic servo systems is described. As is well known, fuzzy controllers have the ability to control a system in uncertain or un-known environments. However, the control performance depends on the fuzzy rules. Therefore, suitable control rules are required. A self-tuning fuzzy controller (STFC), in which the fuzzy rules for the combination of all input signals are automatically adjusted by the tracking error, has been proposed. Although the STFC is effective for improving the tracking performance, it requires many control rules. To reduce the number of fuzzy rules, the ring- and separate-type STFCs are proposed. In the ring-type STFC, the fuzzy rules are described as a combination of two input signals. The fuzzy rules in the separate-type STFC are used to adjust the gain of each input signal. The effectiveness of the proposed fuzzy controllers for improving the tracking performance is demonstrated by an experiment of boom telescoping axis of an aerial working platform.

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