In this study, a new electro-magnetic proportional actuator composed of an armature and stator with multi convex teeth to control oil hydraulic valves was designed and examined. Each of the convex teeth forms a magnetic pole, and when multiple magnetic poles produce a force simultaneously, a large thrust force is generated in the actuator. The shape of the teeth was varied and influence on the thrust force was examined. As a result, the interval between the convex teeth could be reduced. A 10-step pole type actuator was designed, and its thrust force was estimated. When the dimensions of this actuator are 52mm height, 68mm width, by 102mm length, its thrust force is constant within 2mm of the armature stroke, producing about 300N at an electric power consumption of 15W, and it generates the thrust force in proportion to the coil current. The thrust force of this actuator is about 2.5 times as large as that of conventional proportional solenoids and linear motors of the same installation area to the valve body, length and power consumption.

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Variable valve lift (VVL) system for automotive engines is one of the key technologies to attain improvement of fuel economy and power output and reduction of emission. This paper presents a highly reliable VVL mechanism controlled by a hydraulic 3-step rotary actuator. 3-step VVL with high-, middle- and low-valve lift, is realized by the pivot shifting of an intermediate cam placed between a camshaft and valve tappet. The hydraulic actuator with no electric device is installed in a cylinder head and its rotary positioning generates 3-step rotation of a specially-designed sprag cam. The actuator can work in low supply pressure of 0.1MPa and control 3-step angles within the interval in which the valve is at rest during camshaft rotation. This paper describes the analytical simulation model of the VVL system, and the experimental evaluation for the developed VVL mechanism and hydraulic 3-step rotary actuator.

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This study concerns a new rotary water hydraulic pressure intensifier. The object of this paper is to introduce the structure and the working principle of the pressure intensifier, and to present the fundamental characteristics by experimental results. The basic structure is similar to that of a water hydraulic planetary gear motor. Its main part consists of a stator, a rotor, nine planetary gears and two side plates. The inside of the stator is formed by a curve with 5 lobes and the outside of the rotor is formed by a curve with 4 lobes. Their curved surfaces have teeth like a gear. Nine displacement chambers are formed by the stator, rotor, planetary gears and side plates, and the each chamber's volume varies periodically when the rotor rotates. A side plate has 5 inlet distribute holes and 5 outlet distribute holes alternately located on its surface. Each displacement chamber connects to an inlet distribute hole during the volume is increasing, and it connects to an outlet distribute hole during the volume is decreasing. Now, one of the outlet distribute holes is separated from the other 4, the intensified higher pressure water is discharged from the separated distribute hole. It is found that the critical intensification ratio is about 2.5 by experimental results with a prototype.

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A flow visualization of a liquid crystal was conducted under the application of an electric field in a mini cylinder with electrode strips on the inner surface. Three-phase alternating currents were used as rotation electric fields to generate the rotational flow of the liquid crystal. A pump with a spiral flow channel was designed based on the rotational flow mechanism of the liquid crystal by using the three-phase alternating currents. The pressure-flow rate characteristics of the pump were measured and the characteristics for the length and the shape of the flow channel in the pump were investigated for various amplitudes of electric fields. The pressure increased when we used a liquid crystal with a high dielectric constant and a high kinematic viscosity for the constant voltage. Dimensional analysis was conducted to arrange the characteristics of the present pump simply and the non-dimensional flow rate and pressure were almost on one line. The size of our pump can be decreased by further research. This study contributes to the development of a micro-pump in micro-fabricated systems and our pump eliminates mechanical vibration and noise.

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One of the main problems of electrohydraulic drives is relatively low dynamic load stiffness due to compressibility of oil. Sudden load variations can cause significant deviations of the position of the drive and, consequently, a reduced precision of the controlled process. This has led to a partial substitution of electrohydraulic drives by electromechanical drives in a low power range recently.
One of the approaches to increase dynamic stiffness of a cylinder is to raise valve dynamics. Thus, the system can react to a control deviation and provide the cylinder with a compensating flow faster.
The objective of this paper is to show the development of a stiff cylinder drive using a new high-response servovalve - the hybrid valve. In contrast to a conventional servovalve with an unmovable sleeve, the idea of the hybrid valve is to actuate both the spool and the sleeve simultaneously in opposite directions. Using a piezo-actuator as sleeve drive provides the hybrid valve with very high dynamics in the range of small valve opening, which should be sufficient to increase the disturbance rejection of the cylinder. The performance of the valve prototype and of the cylinder will be shown, and application fields will be discussed in this work.

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Noise is a well-known challenge in hydraulic systems and hydrostatic pumps are one of the largest noise contributors in a hydraulic system. The existing noise reduction features, such as pressure relief groove and pre-compression filter volume, are more or less dependent on the working condition. It is essential to know the amount of free air when designing a quiet pump; however, it is not evident how much free air the oil contains. The free air content is different if the suction port is boost pressured or self-priming. The amount of free air in a well-designed system can be as low as 0.5% while in others up to 10%.
This paper uses the three-transducer method to measure the amount of free air in the oil. The oil's compressibility can be measured for different working conditions and the free air content can then be calculated. The pre-study is performed with an extensive simulation model. Various noise reduction features' sensitivity to free air content is considered.

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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 support 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 was composed 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.

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Among the elderly person, most of their injuries are reported to be caused by falling down with stumbling. It is due to their shuffling walking style resulted from deterioration of their dorsiflexion muscle force along with aging. Walking plays an important role in their independent day life. In this study, we aim at developing a wearable walking support equipment embedded into shoes for a purpose of fall prevention of elderly person. A commercial product of Ankle Foot Orthosis is introduced and newly developed wire type pneumatic actuator is equipped on to support dorsiflexion motion during swing period at walking motion actively. In generally, these kind of active supporting systems require power source. We propose a driving scheme with no use of electric power, but with only potential energy of the wearer. Required specifications for the equipment are derived and the validity of proposed walking support shoes is verified through some experiments

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