In manufacturing technology, the predominant tendency in recent years has been for machine tools, for example, turning-, milling-, and drilling-machines, to employ electrically operated actuators such as a servo-motor equipped with a ball screw. There are, however, various problems with these electric driving systems; they are excessively large-sized with complex machinery, and their application is expensive, as seen, for example, in the case of the NC-machine. In order to solve these problems, this study aims to develop a precision driving system actuated by a hydraulic cylinder. The hydraulic driving system consists of a cylinder and four ON/OFF solenoid valves. The valves are the same as those used in a fuel injector of an automobile, which are capable of high speed switching, as fast as 1.5 ms. It was confirmed in experiments that the developed system had a moving resolution of 1.2 μm and, as a result, was applicable to a precision driving table for micro-processing.

In the previous paper based on this study, the authors proposed a high-speed ON/OFF digital valve driven by a laminated piezoelectric (PZT) actuator. One drawback of this digital valve was that the PZT actuator could not produce enough displacement in order to actuate the main valve. Additionally, it may be pointed out that the laminated PZT actuator is considerably expensive for general consumer use. In this study, for the purpose of overcoming such drawbacks, an improved type of high-speed digital valve was developed by adopting a bimorph PZT actuator in place of a laminated actuator. The bimorph PZT is cost-effective to produce and can realize a large displacement; the valve will be financially practical and capable of high performance. To actuate the spool valve, a nozzle-and-flapper mechanism was adopted in the proposed valve. The static and dynamic characteristics of the new device were investigated by experiment and digital simulation. As a result, we found that the valve could be driven by frequencies of a PWM carrier wave as high as 200 Hz.

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I’m especially pleased to send you my congratulations on the publication of “International Journal of Automation Technology”. The automation technology has the extremely clear purpose of replacing human work with automated system. However, the automation technology requires various kinds of technologies, ranging from mechanical technology, electronics, control technology, software technology for computer, to system technology necessary for those to be functioned effectively. Therefore, people, who start to learn the automation technology or keep up on it, cannot help gathering fragmentary information from many kinds of technology fields. Additionally, relationship and collaboration between academic institute and industries are important issues that mean industrial firms investigate mostly practical applications of automated machines and production systems, while mainly universities and institutes research fundamental and elemental technologies. With these backgrounds, it has been tough to grasp its whole picture of the automation technology in general, although some of leading universities, institutes and industry firms themselves advance and accumulate the automation technology systematically. This time, through publishing “International Journal of Automation Technology”, I believe the automation technology must become popular and familiar for a great number of engineers, researchers and students. Especially, this publication is delightful news for young engineers, who work toward advanced automation in global business. I greatly expect this journal play a roll of network among engineers and researchers working on the automation in various technology fields, to help upskilling and stimulation for them, and to contribute the development of the automation technology itself as well.