Calling it obsolete technology would be far too emphatic, but pneumatically operated cylindrical linear actuators draw the keen attention of engineers who are involved in the design of micro/nano positioning, where any electric or magnetic interferences are to be prohibited to secure a micro-machining in production of the latest μ-chips. This paper aims to describe our preliminary challenge to realize a precise pneumatic positioning system, which includes a very conventional pneumatic cylinder having inherent and tough stick-slips, a servo-valve with undesirable dead-zone and the Simple Adaptive Control Algorithm that accommodates non-linear functions to minimize the influence of stick-slip without risk of system instability. The stick-slip deteriorates both of transient and steady-state response, therefore the effectiveness of our proposal should have been confirmed by experiment in this paper.

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In the present study, we succeeded in improving an oil hydraulic ball valve using the visualization technique, in order to prevent the vibration, cavitation and the noise of the ball valve. The valve body outside of the ball is made of transparent acrylic resin in order to observe the cavitation bubbles and the motion of the ball. The cavitation cloud near the orifice in the valve, and the movements of the ball, the ball support and the spring in the three dimensions during cavitation and the vibration of the ball are observed using a commercially available digital video camera, a high-speed video camera and X-rays. The results of the flow analysis using CFD (Computational Fluid Dynamics) technique are also considered to understand the relation between the cavitation phenomenon and the lateral vibration of the ball for the conventional valve. After the flow phenomenon and the vibration of the ball inside the conventional ball valve are investigated in detail, a new type of the ball valve without the lateral oscillation is designed to obtain good performance. It is found that there is no cavitation bubble and no cavitation noise for one of the new types of the valve. The flow structure in the two developed valves in the present study is also investigated in order to understand the reason for the good performance for the one of two valves by the mumerical simulation using the vortex method. In the present work, we propose one of the useful methods for improving an oil hydraulic control valve using the visualization technique.

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This paper describes a novel type of fluid power motor, IP Motor, which can be driven by domestic tap water pressure. Because the driving fluid does not directly contact mechanical moving parts of this motor, it makes it possible to solve problems such as leakage, lubrication, rust and contamination that have plagued previous contact-type motors, without requiring a seal. In order to design the motor with such advantages, this paper examines (i) basic design principles for pinch-roller-driven mechanism, (ii) structural consideration to realize infinite rotation, (iii) the characteristic analysis, and (iv) the mechanism to improve the performance. Finally, the validity of the introduced design methods is demonstrated through the motion experiments which were conducted with a developed prototype.

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