High precision positioning can be achieved by incorporating positioning control, if accurate modeling of frictional behavior occurring in such linear motion ball bearings is conducted. Final goal in this research is an achievement of ultra-precision positioning by building the accurate frictional model on displacement range under nano-meter level. For that reason, it is necessary to clarify the frictional behavior in minute displacement range. This paper describes that nonlinear spring behavior is shown in range of amplitude of displacement under 100μm. In addition, it indicates difference characteristics when the amplitude of displacement is continuously changed. Moreover, the frictional behavior in minute displacement is influenced by changing very small velocity compared with experimental results of sinusoidal and triangle feed.
Speckle interferometry is a useful optical deformation measurement method for objects with rough surfaces. The method can measure not only the out-of-plane but also the in-plane deformation of these objects without any contact. Generally, it is very difficult to measure the three-dimensional deformation from the buckling of a plate, because the deformation distribution of the plate under such a buckling phenomenon is complex and unstable. In this paper, the deformation of the plate is measured at a high resolution by a three dimensional speckle interferometer with the same sensitivity in each of the three dimensions. Furthermore, the measured results are compared with the results of FEM analysis. It is confirmed that the measured results agree qualitatively and quantitatively with the results of FEM. It is estimated that the out-of-plane and in-plane deformations in the buckling phenomenon of the plate can be measured within the accuracy better than several 10 nm. It is concluded that the use of the proposed method will be essential in the studies of buckling in the future.
Hydrostatic bearing is often employed as a journal bearing of grinding wheel spindle for achievement of high accuracy. For the realization of a compact and inexpensive bearing, reduction in number of pockets is an effective way. To maintain performance of a hydrostatic bearing with fewer pockets than that of the conventional one, it is essential to improve static stiffness per a pocket. A self-controlled restrictor with a diaphragm improves static stiffness of the proposed hydrostatic bearing. In this research, a compact headstock using hydrostatic bearing with a self-controlled restrictor is proposed. Numerical analysis of dynamic stiffness and static stiffness of the proposed bearing is carried out by using Reynolds equation, which considers non-linearity of oil flow at restrictor, elastic deformation of plumbing and volumetric strain of air bubble in oil. By experimental evaluation of static stiffness and dynamic response, the developed headstock has demonstrated higher performance than that of one using orifice restrictor. In comparison with a conventional headstock using ball bearing, the proposed headstock has achieved one-half of total length and higher grinding accuracy.
We propose an efficient estimation method of three dimensional profiles of through-silicon vias (TSVs) from one-shot projection images captured with a nano-focus X-ray microscope with a resolution of 0.25 μm aiming at an in-line inspection system. Complicated three dimensional profiles after etching are represented with a simplified model that consists of 8 dimensional parameters. X-ray projection images are simulated with varied parameters determined by extraction of generated uniform random datasets. Machine learning by support vector regression algorithm is applied to form a transfer function to get the geometrical parameters from data of the images. This method gives a repeatability of estimation of < 0.2μm for profiling of TSVs with a targeted size of φ8μm × 90μm depth.
This study has proposed a method of machining curved-holes using electrical discharge machining (EDM) with a suspended ball electrode. The EDM characteristics for aluminum alloy (JIS A5052) and die steel (JIS SKD11) using suspended ball electrode were investigated in this paper. Using a copper-tungsten ball electrode of 7.0 mm in diameter, the stable machining for both types of material were possible. Under almost EDM conditions, the machining speed using a suspended ball electrode was faster than that using a rod electrode with an electrode jump motion, when the hole was not so deep. The hole-diameter using the suspended ball electrode was larger than that using the rod electrode. It was found that the machining stability with the suspended ball electrode was affected mainly by the servo voltage. Additionally, the possibility of curved-hole machining using a suspended ball electrode was discussed. The experimental results showed that 15°, 30°, and 45° bended-holes could be successfully machined in these materials by tilting the workpiece.
The motion accuracy of 5-axis controlled machining centers typically is inferior to the accuracy of 3-axis controlled machining centers. Especially, the motion error of rotary axis by motion direction changes in particular has bad influence to machined surfaces in comparison with the motion error of translational axis, because it is amplified by the distance from the center of the rotary axis to the machining point. In this study, a measurement system and a machining test method are proposed to evaluate the dynamic characteristics of rotary axis by motion direction changes, and the compensation method is considered. It is confirmed by the measuring system and the machining tests that the influence of tracking error on the machined surface is related with the size/shape of the tools and geometrical relationships between the tracking error and the machined surface. In addition, the method to improve the machining accuracy by the dynamic characteristics of rotary axis around the motion direction changing point is proposed, and the effect is confirmed by the actual machining tests.
A wearable body temperature control equipment using body's temperature regulation physiology and a small heat and cold generation device has been developed. Since thermal sensation is settled by core temperature, by heating and cooling directly blood through the neck, the equipment inflects core temperature most efficiently. The equipment is composed of Peltier elements, and a radiation mechanism combining a water-cooling tube and a radiator. It is regulated by an individually adaptive temperature control algorithm that learn the hygrothermal sense of each wearer. Performance evaluation and safety confirmation have been carried out through experimental use in both temperature-humidity control room and daily life environment. The developed equipment weighs 650g including a rechargeable battery, and consumes only one-tenth of electric power compared to conventional air-conditioner. It implements neck temperature control from 20℃ to 40℃, enabling to always carry a comfortable thermal environment.