Until the 1970s, hydraulic actuators were widely used in many mechanical systems; however, recently, electric motors have become mainstream by virtue of their improved performance, and hydraulic motors have largely been replaced by electric motors in many applications. Although this trend is expected to continue into the future, it is important to comprehensively evaluate which motor is most suitable when designing mechanical systems. This paper presents the results of a survey of the performance of electric and hydraulic servo motors and aims to provide quantitative data that can be used as a reference for selecting appropriate motors. We surveyed AC, AC direct, brushless DC, and brushed DC electric motors and swash plate-type axial piston, bent axis-type axial piston, crank-type radial piston, and multistroke-type radial piston hydraulic motors. Performance data were collected from catalogs and nonpublic data. We compared and evaluated the characteristics of these diverse servo motors using indexes such as torque, rotating speed, output power, power density, and power rate.

We have developed a flat device structure, which we call “FLAT”, with no isolation grooves/ridges and no Si substrate etching in the imaging area of the CMOS Image Sensor (CIS). We employed this FLAT structure to achieve a 1.12 μm pitch pixel CIS with a 1.25 transistor/pixel architecture and excellent image quality. It uses FLAT transistors(Trs) that generate greatly-reduced 1/f noise, and FLAT isolators (Isos) that increase the saturation capacity (Qs) due to increasing both effective photodiode (PD) area and PD potential under low dark current.

Air bubbles in working oil affect the stiffness and efficiency of hydraulic systems; thus it is important for technical issues that air bubbles be actively eliminated from the hydraulic oil. A bubble eliminator is a device that uses a swirl flow to remove air bubbles. The shape of the device affects bubble elimination performance, so the selection of shape is the most important parameter in increasing the performance of the device. The purpose of this study is to design a bubble eliminator with an optimal shape. This paper discusses the validity of numerical simulation by comparing, using various diameters of the vent port, the numerical results with the results of the experimental flow visualization. Moreover, we focus on the length of the inlet tube and tapered tube of the bubble eliminator and establish a method of selecting them.

The high-frequency vibration and resonance of armature assembly in the hydraulic servo valve are the main reasons for instability and failure. Magnetic fluid (MF) operating in the squeeze mode can be taken as an effective damper for resonance suppression in the servo valve. Due to excitation difficulty and the low signal-to-noise ratio of high-frequency vibration signals, the capability of MF to modify multiple-order modal damping ratios in a multi-degree-of-freedom system is still unclear. To reveal the mechanism of magnetic fluid for improving modal damping ratios, an algorithm for modal damping ratio identification is proposed. The modal damping ratios of the armature assembly with and without magnetic fluid are identified based on the tested resonance free decay responses. Four resonance frequencies of armature assembly are observed, and the corresponding damping ratios are identified. The equivalent modal damping ratios due to squeeze flow of MF are obtained. The results show that the proposed algorithm can identify damping ratios with an accuracy of up to 98.79%. The damping ratios are improved by double or more due to the magnetic fluid, and the maximum resonance amplitudes are significantly reduced by 65.2% (from 916.5 μm to 318.6 μm).