Shoki Ofuji

A small three-way valve using particle excitation with piezoelectric transducers for hydraulic actuators

Abstract Robots composed of hydraulic actuators have been utilized in various fields and at disaster sites. However, the hydraulic control system for multiple-degree-of-freedom mechanisms is large because such systems require many control components. The purpose of this research was to develop a small hydraulic flow control valve. This paper describes the fabrication and evaluation of a small three-way valve by particle excitation using a piezoelectric transducer. This valve consists of two transducers and can switch the inlet and outlet ports by applying an AC voltage of different driving frequencies to each transducer because each transducer has different resonant frequencies. The flow rate was controlled by applying a voltage to the piezoelectric transducer. We evaluated the vibration characteristics of the fabricated three-way valve. The vibration velocity exhibited peaks at 120 and 155 kHz for the inlet and outlet port, respectively, and that of each transducer increased with the applied voltage. Therefore, this three-way valve can switch the opening port by changing the driving frequencies and continuously controlling the flow rate. As a result, we have succeeded in driving the novel small three-way valve.

A small three-way valve for hydraulic actuators using piezoelectric transducers

Hydraulic actuators has been utilized for various types of robots. However, hydraulic control system for multiple degrees of freedom mechanisms has a large volume because such system needs many control components. The purpose of this research is to develop a small hydraulic flow control valve. In the previous research, we have developed a small flow control valve using particle excitation by a piezoelectric transducer [1], and applied this valve to a hydraulic system. In this research, we have fabricated and evaluated a small three-way valve for further miniaturization.

Low flow rate spraying using a torsional ultrasonic transducer

Generally, the atomization condition is dominated by the Weber number. In this research, we have fabricated the torsional transducer and longitudinal transducer to evaluate the effect of the atomization by the Weber number. We have observed the spray angle and atomization condition. First, to evaluate the performance of the spraying nozzle with the torsional vibration, water has been sprayed. When the driving frequency, the applied voltage, and the flow rate were 18.3 kHz, 100 Vp-p, and 15 ml/min, the water has been successfully atomized. In addition, although the ethylene glycol has higher viscosity, we have succeeded in atomizing ethylene glycol effectively. As a result, the torsional vibration is suitable for the atomization in a low flow rate.