Papers by Keyword: Air Bearing

Abstract: Calibration for torque measurement devices has become a great demand in many industrial areas. The most important in a calibration process is decreasing its uncertainty. This paper presents in building formula to evaluate the measurement uncertainty for torque standard machine using air rotary bearing which is experimented at the Hanoi University of Science and Technology. The uncertainty of the device is composed of the uncertainty of the component elements such as arm length, load, friction torque, axial tilt, vibration load...etc. Based on them the formula is built to estimate the measurement uncertainty of torque standard machine, find out factors that affect most to the measurement uncertainty value, therefore it can benefit the further researches to improve the accuracy of the torque standard machine.

Abstract: The resultant force acting on the moving part of the ceramic aerostatic linear bearing is measured highly accurately as the inertial force of the moving part of the bearing by means of the levitation mass method (LMM). The measurement results of the ceramic aerostatic linear bearing and metal aerostatic linear bearing of different mass are compared. The regression equation of the ceramic aerostatic linear bearing and metal aerostatic linear bearing are calculated. The ceramic linear bearing and metal linear bearing have extremely small frictional force.

Abstract: The objective of this research is to develop a PC-based closed-loop nanopositioning system using the dual-frame two-axis drive single mobile independent framework. The stage body was supported by an air bearing on a granite base to reduce the frictional force. The developed stage was driven by the PC-Based interface of ANCA 5DX CNC controller, for the precision motion control of the linear motors. The laser scales were used as the feedback sensors so that the closed loop control of the developed system was possible. Based on the test results, the designed closed loop nanopositioning system was capable of precision positioning within the travel of 100 mm along X-axis and Y-axis. The Z-direction stage stability of the developed system was 20 nm, the maximum yaw error of the stage moving along X-axis was about 3.77 arc-seconds, and the maximum pitch error of the stage moving along Y-axis was about 1.04 arc-seconds, based on the test results. By utilizing the PC-Based interface of ANCA 5DX CNC controller based closed-loop PID control system, the positioning capability of X-axis and Y-axis was about 20 nm. Performing the circular test with radius of 20 mm, the deviation of circular positioning test was about 223 nm. Based on the tracing speed test results, the standard deviation along X-axis and Y-axis was 5 nm under tracing speed of 0.05 mm/min.

Abstract: This paper focuses on the pressure distribution on the surface of slider in hard disk drive when its flying height is in nanoscale. The gas rarefaction effect and van der Waals force are involved in the analysis process. Here the air bearing force model is based on F-K model and we establish the equation of van der Waals force between the head and disk. Using the finite element method, the modified Reynolds equation and the van der Waals force were obtained. The air bearing force on slider before and after the van der Waals force involved were compared. The results illustrate that the effect of van der Waals force on the air bearing force is different according to the slider shapes and flying heights. As a result, van der Waals force plays an important role when the flying height of slider is below 10 nm.

Abstract: A new-type frictionless pneumatic cylinder with an aerostatic bearing as its piston can decrease the friction significantly. The stability and the leakage of this cylinder mostly depend on the radial load carrying capacity(RLCC) and the air consuming of the bearing. In order to make a better use of this cylinder in pneumatic servo systems, a simulation study on the influence of the structural parameters and time-varying surrounding parameters to this cylinder was carried out on the basis of a numerical solution method based on finite element method(FEM) which was constructed to solve Reynolds equations in this paper. Simulation shows that introducing a recess chamber at the end of the orifice hole can increase the RLCC significantly and smooth the sharp distribution of the pressure around the orifices in the air film, which makes the bearing working more stable; the time-varying parameters have a combined effects on the performance characteristics of the bearing.

Abstract: Under different throttle type, the bearing lateral force is calculated with the heeling angle changed by using the finite volume method. Also, cavity diameter and depth are selected, which can get influence on bearing lateral force in the same heeling angle. By attributing the error between experiment results and compensational ones to measurement error and instrument error itself, the results are verificated.

Abstract: This paper presents the dynamic response of an air-bearing displacement sensor for on-machine surface form measurement of micro structures. The on-machine measurement system has some merits in terms of measurement efficiency and re-machining for error compensation after measurement. On the other hand, the performance of the contact type measurement system based on stylus methods is dominated by the dynamic characteristics of the system because the system is subject to random vibrations of the machine tool including the spindle during measurement. Therefore, the dynamic response of the system is useful for analyzing the mechanical vibrations of the practical on-machine measurement system. In this paper, the equation of motion for the air-bearing displacement sensor to the excited input displacement is derived and the displacement behavior of the system by using a PZT actuator is investigated within certain frequency ranges experimentally for identifying the dynamics of the system.

Abstract: A new type of hydrostatic journal gas bearing with axial slot of tangential gas entry for miniature air turboexpander is firstly developed in this paper. This bearing configuration is presented and constructed to fit manufacture simplicity. The experimental investigations are carried out to reveal the relationship between bearing parameters and instability threshold speed. It is feasible to increase the stability of hydrostatic journal gas bearing by adopting this kind of configuration with axial slot of tangential gas entry. Some valuable tested results are obtained to reveal the optimum slot height and radial clearance for this miniature air turboexpander.

Abstract: Based on various combinations of ACs of the slider and disk, the influence of ACs, were investigated by researchers. In the present paper, the static characteristics of air bearing film with the linear ACs are investigated. Pressure distribution and shear stress distribution are obtained by solving the free molecular MGL equation numerically by a mesh-free method, called Least square finite difference (LSFD). The simulation results show that with different ACs the shear stress and pressure are different, and on shear stress the influence of AC of slider is more obvious than that of disk in close to disk read-and-write head.

Abstract: The air-lubricated pneumatic workbench introduced in this paper is used in rotary ultrasonic machining which are widely used to machine hard and brittle materials. It is necessary to use special ultrasonic machine tool for rotary ultrasonic machining in the traditional ultrasonic machining, limiting the application of ultrasonic machining. A new type of rotary ultrasonic grinding cutter is developed, which can be mounted on the general purpose machine tool used to machine the hard brittle materials. The air-lubricated pneumatic workbench on which the workpiece is fixed can be used to precisely control the force between the workpiece and rotary ultrasonic grinding cutter when machining. Based on the experimental results of the pneumatic workbench which has been manufactured we find that the force between the workpiece and rotary ultrasonic grinding cutter can’t be easily controlled for the rolling bearings used in such workbench and the rolling friction force between the rolling bearing and guide way. This paper describes a novel pneumatic workbench where we replace the rolling bearing with air bearing which introduces essentially zero friction between the air bearing and guide way. The stiffness of the air-lubricated pneumatic workbench has been calculated in this paper.