This paper proposes a new velocity measurement algorithm by measuring the velocity emf of electric actuator with high accuracy. First of all, the principle of measurement using in this algorithm is presented. Then, the whole structure and function of each element in this algorithm are explained. Also, the analysis of the adaptive control system, which is included as a component of this algorithm, is given. After all, results of the simulation experiments verify that the proposed method is valid to design velocity measurement algorithm.

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It is well known that preloaded ball screws with double nut produced hysteretic motion between the rotary motion of the screw shaft and the linear motion of the nut, which is called “lost motion”, affects positioning accuracies of ball screws.
Preloaded ball screws with a double nut have the characteristic that loaded balls wedge into a right angle direction to a ball rolling direction because the directions of screw shaft and nut raceways differ from the ball rolling direction. Loaded balls of preloaded ball screws with a double nut have two contact points geometrically. When the ball screw is operated under the condition of screw shaft turning and nut stationary, the balls have the velocity component perpendicular to the load line of action due to the helical raceway groove. Therefore the balls wedge into nut grooves. In the case of a ball screws with a circular-arc groove profile, “ball wedging” phenomenon is saturated when the force of resistance to ball wedging exceeds a frictional force between the ball and the raceway groove.
In the present study, the authors experimentally investigated the lost motion of the X-table which is composed of a preloaded precision ball screw and a couple of linear air bearings, and the ball wedging behaviors under the condition of varied preload with double nut or over-sized balls have also measured.

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Contact lens has much convenience unlike glasses lens. Therefore, it has been used a lot so far after the safety of the contact lens was secured. However, the standard of the contact lens is only geometric parameters of the lens shape. Recently, measurement of contact lens aberration has begun to improve the quality of vision. This report describes wavefront measurement of contact lenses by point diffraction interferometer (PDI). In the experiment, a PDI experimental device for wavefront measurement of contact lens is proposed and the method for alignment of the optical system is considered by error analysis. Next, wavefronts of hard contact lens and soft contact lens are measured. As a result, the contact lenses used for experiments are the same maker, but it is found that the wavefronts of lenses in the same diopter power are different.

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This paper describes a fast tool control (FTC) system integrated with a piezoelectric force sensor, namely FS-FTC system, which is designed for in-process measurement of cutting force during the fabrication of micro-lens array. It is confirmed that the FS-FTC unit has a stiffness of 62.2 N/μm. Micro-lens arrays are fabricated on two Ni-P plating roll workpieces with different degrees of hardness by using the FS-FTC system. Each of the micro-lenses has a length of 200 μm and a depth of 5.2 μm. The amplitudes of thrust forces measured during the cutting process by the FS-FTC system are 2.12 N and 0.94 N for the hard and the soft Ni-P plating roll workpieces, respectively.

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This paper proposes a precise and fast approach to solve stereo correspondence problem in monocular eye-in-hand systems. Basic stereo methods use two static viewpoints. Some stereo methods use multiple static viewpoints. These methods improve accuracy performance, but take a lot of time in the monocular eye-in-hand systems. For a precise and fast measurement, our approach uses two static viewpoints and multiple dynamic viewpoints. Using the dynamic viewpoints, we take two steps. 1) propose two simple movement models of the eye-in-hand systems, 2) define tracking stability of each feature points in the models.

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Self-excited chatter vibration in end milling is caused by the regeneration and mode coupling mechanisms. In order to avoid chatter vibration, both mechanisms need to be investigated. Past researches have shown that the mode coupling effect in end milling can be suppressed by using cutting tools with anisotropic dynamic characteristics. However, it is difficult to apply previously developed analytical models for predicting the chatter stability limits in end milling with the anisotropic tools. Hence, suitable conditions for chatter suppression and the overall phenomena have not been clarified thoroughly yet. This paper proposes a new analytical model to predict chatter stability limits in end milling with tools that have anisotropic transfer functions. The model considers the anisotropic tool to vibrate steadily in a rotating coordinate system rather than in an inertial coordinate system. The cutting process is formulated in this rotating coordinate system, and variation in the transfer function of the anisotropic tool with respect to the spindle speed is considered. Fundamental cutting tests have been conducted to verify the proposed model. Experimentally identified stability limits agreed closely with the predictions. Furthermore, analytical investigations have shown that the transfer function of the cutting tool changes considerably with the spindle speed. This affects the chatter stability prediction significantly. Using the proposed model, it is concluded that higher stability limits can be achieved only at low spindle speed conditions by using anisotropic tools. However, the number of flutes on the tool is limited to be less than three, and they need to be arranged at suitable positions. The effect of the cutter helix also needs to be negligible.

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Ti(C,N) base WC containing polygenic cermets possessing both wear resistance, toughness and characteristics gained from the fine surface perfect for products have been used in multiple ways in the milling process of SKD11 steel used as a metallic material in recent years. However thermal cracks form at the tip of the tool blade in milling process conditions where a severe intermittent load is repeated, often reducing the life of the tool. The life of the tool needs to be lengthened.
This study investigated the effect of microstructure that changes according to the WC content amount in the cermet when SKD11 materials are intermittently processed using a WC containing Ti(C,N) base cermet tool on the milling cutting performance in order to develop a milling cutting process cermet tool. We also observed and rated signs of thermal cracks created on the tip of the tool blade using a transmission electron microscope(FE,TEM). This showed that cermet materials containing much WC in a range where abnormalities do not occur form triple dense core rigidity with a (Ti, W) C rim or double dense core rigidity with a (Ti, W) C core, and the lifespan of defect resistance is extended because the thermal crack growth resistance is increased.

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Self-lubricative tungsten carbide bodies were prepared by electrical current activated sintering with the addition of carbon onion, and their mechanical and tribological properties were examined. The addition of carbon onion into the sintered tungsten carbide bodies led to reduced friction coefficients in both air and vacuum, in particular, at high temperature. On the other hand, Rockwell hardness and three-point bending strength declined. SEM observation of the fractured surface of the tungsten carbide bodies revealed that grain boundary fracture happened. Moreover, the aggregation of carbon onion and the pores were found on the fractured surface. These results would indicate that carbon onion works as a lubricant in the sintered bodies but not a binder between tungsten carbide particles.

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SiC is a promising next-generation semiconductor material for high-temperature, high-frequency and high-power device applications due to its excellent properties, such as good thermal conductivity, good carrier mobility and high chemical stability. In device fabrication, atomically smooth and damage-free SiC substrates are highly required for producing high-quality epitaxial films and gate-oxide interfaces. However, such SiC substrates are relatively difficult to machine because of its mechanical hardness and marked chemical inertness. We have proposed and developed an ultra-precision polishing method for single crystal SiC substrates utilizing an ultraviolet (UV) irradiation. This paper describes the planarization method of SiC substrate by constant-pressure grinding and ultraviolet irradiation assisted polishing. The surface qualities were measured and evaluated using phase-shift interferometric microscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The obtained results show that the many asperities on the preprocessed surface could be completely removed and the surface roughness was markedly improved by constant-pressure grinding and ultraviolet irradiation assisted polishing. The microroughness of the processed surface was improved and realized to be 0.12 nm (Ra) and 1.55 nm (Rz), respectively.

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In case of drilling for a large number of holes, the total process time is composed of the sum of the movement time between a hole and another, and the sum of the drilling time of holes. The former time depends on the drilling order although the latter time is constant. Thus, the difficulty increases with increasing the number of holes in deciding the appropriate drilling order. In addition, it is required to avoid changes in the movement direction because the reverse movement causes the vibration and the degradation of machining accuracy. In this study, the decision problem of the drilling order for a large number of holes is treated as Traveling Salesman Problem. By considering influence of the change in the tool posture, the movement time and the number of the reverse movement are selected as the objective function. In order to optimize the objective function, Simulated Annealing and Genetic Algorithm are applied in the study. As the result of conducting drilling simulation, it is found that SA is superior to GA in this study. The sum of the movement time is reduced to 1/3 by SA, compared to the conventional method. It is also confirmed that the number of the reverse movement is reduced to 3/4 of the conventional method.

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