This paper centers on the theoretical analyses of the pressure versus the flow characteristics of a force -balance nozzle-flapper type pneumatic pressure control proportional valve. The influence of the flow force and effective area of the diaphragm, regarding the pressure versus the flow characteristics, have be studied. Especially, the effects of the radii of the corner rounding of the disk and casing wall have been researched. It has been clarified that the main reason for a pressure decrease in the valve characteristics is due to the change in the effective diaphragm area according to the displacement of the supply valve, and that the flow force may have a slight effect on the characteristics at the time the valve setting pressure is low.

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In pace with a society which in the near future is largely to be composed of elderly people, a necessary technology is one which is friendly to human. There mainly are 1) user friendly man-machine interfaces, 2) smart actuators, 3) intelligence friendly to human.
This paper describes how to make a support instrument for use in nursing care, concerning an intelligent actuator incorporated in the support instrument. A voice-controlled pneumatic servo seems to be more suited as a support instrument than electric and hydraulic ones, because its high compliance caused by air compressibility is friendly to users. We adopt an electro-pneumatic servovalve and cylinder to build a control system which can follow the use's intentions (voice). In control strategy, not only system stability but also safety, comfort and accessibility ease are considered. Using a performance index of comfort or friendliness, driving patterns of the actuator based on the load acting on the bolster are decided and studied with simulations and experiments.

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Absolute negative pressure phenomena occasionally occurs in oil hydraulic circuits containing throttles and pipelines. Here, a new simple simulation technique is proposed by using an SSS (Simple-Stable-Simulation) element which is introduced to solve the nonlinear part including a throttle, in consideration of the surface tension of a contained lumped bubble. This element can be standardized under SSS devices (subroutines). The devices can also treat the systems including distributed parameter systems, under a Runge-Kutta main loop. The simulated results show good agreement with the experimental results.

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In this study, solutions were sought for two problems encountered in a large scale hydraulic optimal control active mass damper (AMD) system, spillover oscillation and low efficiency of cylinder stroke in a single rod cylinder. To prevent spillover oscillation without a larger system model or compromise of control performance, a control rule modified by the pole assignment method is proposed. The theoretical optimal control rule for a single rod cylinder was derived. The control method was shown valid by simulation. The experimental results showed close agreement with those of simulation and on the basis of which, a system test of AMD without real structure, was established.

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In this paper, the author has presented a high-speed hydraulic turbo motor using a negative damping flow force causing self-excited oscillation of the valve.
Traditional turbo machines employ a flux of momentum for fluid passing out and into the control volume. However, the turbo motor studied here is driven by the flux of the momentum passing out and into the control volume plus the rate of change of momentum within the control volume of the turbo motor.
A theoretical analysis regarding equations of the turbo motor and some experiments were made. According of the results of the simulations using the Runge-Kutta Method, it could be clarified that the rate of change of the momentum within the control volume increases the rotational speed of the turbo motor.
As a result of these, about 40, 000 rpm was obtained at 10 MPa and 60°C. The theoretical computations were in good agreement with the experimental results.

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