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Recently, due to the ageing in Japanese society and the decreasing birthrate, an important problem of providing nursing care for the elderly has occurred. As a result, it is necessary to develop wearable systems to aid in nursing care. To realize the system, we require not only wearable soft actuators, but also compact and flexible control valve that can drive the soft actuator such as a pneumatic artificial muscle. The purpose of our study is to develop a flexible, lightweight and compact control valve which can be safe enough to be attached to the human body. In this study, we proposed and tested a new type of control valve. The valve consists of a vibration motor and a check valve that made of a steel ball and an orifice in flexible tube. The operating principle of the valve is as follows. The valve is normally closed as a function of check valve. When the vibration is applied, the inner ball in the check valve moves and the valve opens. By giving continuous vibration, the valve can keep open. As a result, we find that the valve can control the relatively larger flow rate compared to their weight and size.

A poppet type brake pressure control valve, which the output pressure is proportional to the input displacement, is developed to use in the hydraulic control system for friction brake of railway rolling stock. Internal feedback structure isdesigned to eliminate the reliability problem of the pressure transducer, and the poppet type valve is utilized to reducethe internal leakage, which is a problem of the conventional control valve when the electrical supply is under failure.Compensation methods for the disadvantages of poppet valve and the stability are considered together with the structure of the valve. Static and linearized dynamic models of the valve are determined to study the effects and to decide the parameters of valve. The stability and performance of valve are studied and confirmed experimen tally. The experimental results show that the response of out put pressure is improved compared with the conventional pneumaticbrake system.

Our development program fabricated a proportional control valve that exclusively uses water as its working fluid. The valve is equipped with a spool, and the spool is directly driven by a proportional solenoid that is modified for water use. Characteristics of the proportional solenoid are described first in this report while proving its performances similar to those of the conventional oil hydraulics.Following, structural characteristics of the water hydraulic proportional control valve are discussed. Water, the valve's working fluid, is low in lubricity and viscosity; therefore, hydrostatic bearings that support the spool are installed in the valve. In addition, to stabilize movement of the spool, damping orifices are provided. Particularly, the hydrostatic bearing portion is designed such that it minimizes the total leakage including bearing flow while obtaining load carrying capacity. The constant flow from the hydrostatic bearings prevents water from decaying in the valve. Lastly, the paper introduces experimental results of cylinder positioning controlled by the developed water hydraulic proportional control valve to verify its satisfactory performances as a control valve.

Primarily in use at present is the nozzle flapper type servo valve providing with a torque motor.It is not in all cases appropriate for construction machines requiring large flow, owing to small control flow of the nozzle flapper.To deal with this situation, the linear motor servo valve using a magnet for a proportional solenoid has been developed.By driving metering spool directly by a linear motor, neutral leak is kept small and control flow increases.This valve operates independently of supply pressure fluctuation, i.e, pressure compensating characteristics.For large stroke of the linear motor, the orifice diameter is large, thus greatly lessening the possibility of contamination failure of the valve.Frequency response of the main spool is as much as 70Hz.This valve is thus shown suitable for construction machines.

Conventional electro-hydraulic servo valves have sleeves and spools which move axially to control the flow of fluid. However, very high manufacturing technology is required to make them. This paper describes a newly developed rotary servo valve that has a simple structure and is directly operated. It consists of a rotor and casings which control the flow of fluid by their relative positions, a magnetic circuit, a coil which drives the rotor directly by electromagnetic force, and a potentiometer to feed back the angular displacement of the rotor. The valve portion is easy to manufacture and easy to refurbish for reuse. This valve performs as well as the conventional one. The new rotary servo valve has been applied to hydraulic control systems of rolling mills with good results.

Spherical poppet valves are used for pressure, flow and direction control in many oil hydraulic systems as they can be produced with low cost using marketed hard steel balls.In this paper, a spherical poppet valve is used for pressure or flow control, and basic valve characteristics are experimentally studied under a relatively small valve opening condition. The flow rate characteristics, thrust force characteristics, cavitation condition and the effect of cavitation on valve characteristics are investigated using several kinds of typical formed valves with different shaped seats such as; sharp edged seat, spherical chamfered seat and conical chamfered seat. Observation of cavitation and measurement of pressure distribution in the valve are made with a half-cut model of the test apparatus. As a result, effects of the ratio of the spherical poppet diameter to the valve seat diameter, the length of the spherical chamfer on the seat, the difference of the shape of restriction orifice formed by the spherical poppet surface and the conical chamfered seat, are revealed.