Pneumatic Bearing Research Articles

A STUDY ON THE THERMAL CHARACTERISTICS OF THE GRINDING MACHINE APPLIED HYDROSTATIC BEARING

In order to activate the high precision and multi-functional machine tool, adequate technical level of the high-precision products is required. The hydrostatic bearings is used as a method for producing the high-precision products. The hydrostatic bearing has a relatively small run-out compared to its shape error by fluid film effect in hydrostatic state similar to pneumatic bearing and has high stiffness, load capacity and damping characteristics. In this study, we conducted a study on the thermal deformation of the grinding machine that has a great influence on the machining accuracy of the product. The temperature of the front bearing is 10°C or higher than the temperature of the rear bearing. Thermal deformation of the spindle was found to be dependent on the temperature of the hydrostatic bearing and could identify the overall thermal characteristics of the grinding machine.

Development of a Spherical Air Bearing Positioning System

In line with the general trend of the automation, spherical motion systems are increasingly required in applications such as robot joints, manipulators, orientation control systems, and angular alignment systems. In this paper, a spherical air bearing positioning system (SABS) aiming at providing highly precise rotational motions in two degrees of freedom is designed. The SABS mainly consists of direct-drive voice coil actuators and pneumatic bearing. This paper presents the mechanical structure and control system of the SABS. The model of the SABS is identified based on adaptive control concepts. To eliminate the measurement noise, a noise filter is designed on the basis of the model. Then, an observer-based PID controller is designed and implemented on a dSPACE development card. The experiment results show that the designed controller can achieve higher precision and better tracking performance of about ten times compared to that from a traditional PID controller.

601 ガスタービン用空気軸受の動特性の解析技術(OS1-(1) 計算力学と数値シミュレーション,オーガナイズドセッション)

Recently rotating speed of the rotary machine used in various fields is increased, the high temperature and the high pressure of the operation environment causes physical damage to the machine, and results in the wear-out for preventing such problems, it is important to predict and prevent the possible problem using CFD in the early stage of the designing. In this study, numerical analysis of fluid behavior in the pneumatic bearing was performed for the development of advanced pneumatic bearing for space. We reported here the result with respect to the dynamic characteristic of the solid of revolution.

S5.8. Development of an ultrasonic method to monitor the medium viscosity during blood plasma clotting process

An experimental facility has been designed to study the transverse response of the vortex-induced vibration of a fully submerged horizontal cylinder under the influence of vertical harmonic oscillating motion. The study aims to analyze the vortex self-induced vibration (VSIV) phenomenon which occurs on steel catenary risers (SCR) connected to floating platforms in the deep offshore. These vibrations occur in the absence of a current due to the self-motion of the body caused by a source afar. The experiments were conducted in a tank at the LOC/COPPE/UFRJ (Laboratory of Waves and Current of COPPE, Federal University of Rio de Janeiro). The amplitude and frequency of transverse motion are calculated for various Keulegan-Carpenter numbers and reduced velocities. Thanks to both the use of recent instrumentation and very low damping pneumatic bearing, the paper complements the pioneering work by Sumer and Fredsoe (1988) by exhibiting for the first time the trajectories of the VSIV motion. These are classified based on their different configurations such as oval-shape, eight-shape, etc. The Particle Image Velocimetry (PIV) tests are used to study the behavior of the flow around the cylinder during different trajectories of VSIV motion.

A new pneumatic bearing dynamometer for power input measurement in stirred tanks

A turntable dynamometer has been constructed for the accurate measurement of power input and mixing applications in bench stirred tank reactors. The main feature of this device is a pneumatic bearing with complementary conical parts. The conical pneumatic bearing permitted to apply eccentric loads without affecting its stability. The static friction torque in the pneumatic bearing was very small, 4 x Nm, and can be neglected in the experimental ranges of measured torques, i.e. from 5 x to 2.21 Nm. In accordance with the instrumentation used, the deviations obtained with the apparatus are less than 10% at low torque readings. At moderate torques, deviations lower than 1 % are routinely obtained. Several power input measurements show that the obtained data scatter is lower than 2.5 % . The power input response in the turbulent regime is in agreement with dimensional analysis: the power input depends on the cube of the impeller speed. In addition, data obtained with a turbine impeller under ungassed conditions agree with the predictions of a published correlation, which takes into account several geometrical parameters.

Environmental forces on engineering structures : Proceedings of the International Conference at Imperial College, London, July 1979 Edited by C.A. Brebbia, P.L. Gould and J. Munro

An experimental facility has been designed to study the transverse response of the vortex-induced vibration of a fully submerged horizontal cylinder under the influence of vertical harmonic oscillating motion. The study aims to analyze the vortex self-induced vibration (VSIV) phenomenon which occurs on steel catenary risers (SCR) connected to floating platforms in the deep offshore. These vibrations occur in the absence of a current due to the self-motion of the body caused by a source afar. The experiments were conducted in a tank at the LOC/COPPE/UFRJ (Laboratory of Waves and Current of COPPE, Federal University of Rio de Janeiro). The amplitude and frequency of transverse motion are calculated for various Keulegan-Carpenter numbers and reduced velocities. Thanks to both the use of recent instrumentation and very low damping pneumatic bearing, the paper complements the pioneering work by Sumer and Fredsoe (1988) by exhibiting for the first time the trajectories of the VSIV motion. These are classified based on their different configurations such as oval-shape, eight-shape, etc. The Particle Image Velocimetry (PIV) tests are used to study the behavior of the flow around the cylinder during different trajectories of VSIV motion.

Pneumatic applanation tonometer studies. III. Analysis of the floating tip sensor

A theoretical and experimental study has been made of a pneumatic tonometric sensor designed to continuously record intraocular pressure and intraocular pulse. The tonometric probe includes a pneumatic bearing, which allows the sensor to float freely on a cushion of gas. Theoretical and experimental analyses have shown that it acts in a closely similar manner to the sensor without a gas bearing. Both can record the intraocular pressure with minimal volume disturbance of the eye and both can follow accurately experimentally induced modifications of pressure. However, they do differ in that the air-bearing means that the sensor is pushed against the cornea with a force of a few grams. This additional force causes a pressure increment in the eye of 1 or 2 mmHg above that induced by the rigid sensor, depending on whether the sensor is applied either horizontally (1 mmHg) or vertically ( ca. 2 mmHg) to the eye.