Sayako Sakama

Comparative Study on Dynamic Characteristics of Hydraulic, Pneumatic and Electric Motors

Hydraulic or pneumatic motors are replacing electromagnetic servomotors in many applications. It is important for engineers and designers to select adequate actuators in given servo applications. In a previous paper, Nakano had predicted the performance of future electric or hydraulic motors after that there have been many advances in actuators. In this paper the performance of hydraulic and pneumatic motors, and electric AC servo and DC motors has been calculated, surveyed, and evaluated on the basis of specifications listed for them in current catalogs and nonpublic data. We selected 765 different kinds of electric motors and 404 different kinds of fluid power motors available in the market. Power density, torque–inertia ratio, power rate, and power rate density were selected as the performance indexes for comparison. Rated power and torque were found to be nearly proportional to motor mass and moment of inertia, respectively. The electromagnetic motors have developed high performance with large rated torque and a smaller moment of inertia. The newly developed small-size hydraulic motor was also included in the performance index, and its characteristics were plotted. The compact size of fluid power actuators has great potential for power rating or quick response.Copyright

Design and fabrication of ER braking device for micromouse

Micromouse contest is a competition which an autonomous micro-robot through a designated maze to compete for intelligence and speed. In this paper, a small soft mechanical braking device using electro-rheological fluid (ERF) for the micromouse was designed and fabricated. It was experimentally clarified that the prototype model of the ER braking device can provide a sufficient braking force.

A Study on Design and Estimation of Bubble Eliminator: (1st Report : Selection of Diameter of Vent Port)@@@(第１報, 放気口径の選定)

Hydraulic systems feature compact, high-output power and rapid response. However, when air bubbles are mixed into the hydraulic oil, they lower the efficiency of hydraulic systems and contribute to instrument malfunctions. Therefore, it is important to eliminate these bubbles from the oil. Our project team has been developing an active bubble elimination device termed a bubble eliminator, which removes air bubbles using a swirl flow. The shape of the device affects the removal performance, so the choice of shape parameters is key to improved performance of the device. The purpose of this study is to optimize the shape parameters of the bubble eliminator. We focus particularly on the optimal diameter of the vent port. In order to determine this parameter, flow behaviors in the bubble eliminator are investigated in the laboratory with transparent bubble eliminators and numerical analysis of the experimental conditions. The validity of numerical simulation is verified by comparing its results with flow patterns obtained from image photos of an experimental flow visualization. Numerical analysis is carried out under fixed conditions, and an optimal diameter for the vent port is determined.

Numerical evaluation of bubble eliminator for hydraulic systems

Air bubbles in working oil influence stiffness and efficiency of hydraulic systems, thus it is important for technical issues to eliminate the air bubbles actively from the hydraulic oil. Bubble eliminator is a device that removes air bubbles by using a swirling flow. The purpose of this study is to design optimal shape of the bubble eliminator. Flow and volume fraction of bubble in the bubble eliminator have been studied by numerical analysis. It is numerically evaluated to confirm effects of some parameters: diameter of outlet port, diameter of vent port, inlet flow, height of inlet port, length of inlet tube, length of tapered tube and diameter of inlet tube. The optimal dimensions of the bubble eliminator are proposed and the performance of bubble eliminator is evaluated by numerical simulation.