Atsushi Mitani

Microparts Feeding by a Saw-Tooth Surface

This paper examines the novel use of a saw-tooth surface with a simple planar and symmetric vibration for a unidirectional microparts feeding. In the microparts feeding, to drive the microparts in one direction, the driving force applied to each micropart must vary according to the direction of motion of the micropart. In the case of a saw-tooth surface, either the point or the slope of the saw-tooth can make contact with a micropart. The microparts move in one direction by the driving force according to the contact between the microparts and the saw-tooth surface. The feeding experiments show that the unidirectional feeding is achieved by the proposed method. The driving force at each contact and the dynamics of the microparts with adhesion force were formulated for the feeding simulations. Regarding the elevation angle at which the velocity was maximum, there was a good agreement between the simulation with adhesion force and the experimental values

A biomimetic soft fingertip applicable to haptic feedback systems for texture identification

Humans recognize textures using the tactile data obtained from the human somatosensory system. Recognition of textures allows humans discriminate objects and materials. Moreover, by understanding the objects or materials texture, the human intuitively estimates roughness and the friction properties of the object or the material. This ability is necessary for object manipulative tasks. Likewise artificial haptic systems too, should have the ability to encode textures and feedback those data to haptic applications such as haptic displays. In this paper a biomimetic soft fingertip sensor that can be used in above haptic systems is introduced. The fingertip has the ability to detect force and vibration modalities. We propose three features calculated from the covariance signal of two adjacent accelerometers in the fingertip to use in texture identification. The covariance signal is transformed using Discrete Wavelet Transform (DWT) and the three features mentioned below are calculated. The mean and variance of the approximate signal, and the energies of the detailed signal are chosen as features. Then, the proposed features were validate by using those in an Artificial Neural Network (ANN) to classify seven wood samples. The results showed a 65% success rate in classifying wood samples and that the proposed features are acceptable to encode textures.

Micro-Parts Feeding by a Saw-tooth Surface

This paper investigates micro-parts feeding using a saw-tooth surface. In parts feeding, the driving force applied on each part must vary according to the direction of motion of the part so that the part moves in one direction. Traditional feeders employ oblique or asymmetric vibration of the feeder surface, which often causes unstable motion of micro-parts. In this paper, we propose micro-parts feeding using a saw-tooth surface with simple planar and symmetric vibration. First, we describe the principle of the proposed technique. We then develop a model describing the contact between a micro-part and a saw-tooth, and formulate the condition for feeding. Next, we conduct experiments to assess the feasibility of micro-parts feeding by the proposed method. Finally, we discuss how well the feeding model fits experimental results.

Feeding of Submillimeter-sized Microparts along a Saw-tooth Surface Using Only Horizontal Vibration: Analysis of Convexities on the Surface of Microparts

We have previously showed that microparts can be fed along a saw-tooth surface using simple planar symmetric vibration. Microparts move forward because they adhere to the saw-tooth surface asymmetrically. We studied also the effects of saw-tooth pitch and vibration frequency on the movement of 2012-type capacitors (size:2.0 times 1.2 times 0.6 mm, weight:7.5 mg). In the present work, we studied the movement of smaller 0603-type capacitors (size:0.6 times 0.3 times 0.3 mm, weight:0.3 mg). We analysed the contact between a micropart and a saw-tooth surface based on measurements. A microscope was used for the measurements of a 0603-type capacitor surface to obtain a precise surface profile model. Smaller capacitors rotated on the saw-tooth surface when they were moving in one direction. We thus examined the movement of smaller capacitors, and then examined the decrease of feeding velocity caused by this rotation and swinging of the smaller capacitors.

Analysis of contact between feeder surface and microparts based on measurements for microparts feeder using an asymmetric surface

We previously showed that microparts can be fed along a saw-toothed surface using simple planar symmetric vibrations. Microparts move forward because they adhere to the saw-toothed surface asymmetrically. Using saw-toothed silicon wafers fabricated by a dicing saw applying bevel type blades, we evaluated the principle of unidirectional feeding of 2012-type capacitors (size, 2.0 times 1.2 times 0.6 mm: weight, 7.5 mg) and 0603-type capacitors (size: 0.6 times 0.3 times 0.3 mm, weight: 0.3 mg), by analysing the contact between these feeder surfaces and a spherical model of convexities on the electrode surfaces of these capacitors. To extend these findings, we analysed the contact between capacitors and the saw-tooth surface using direct measurements. Surface profiles of the feeder surfaces and 0603-type capacitors were measured microscopically. Picture analysing software was applied to obtain a numerical model of these surface profiles. By processing the numerical model, we calculated a linear polynomial that approximated the surface profile. An adhesion model was examined by analysing the contact between these approximated models. Finally, using this adhesion model, we formulated a model for the driving force of microparts.

The effect of anisotropic friction on vibratory velocity fields

This paper explores the role of anisotropic friction properties in vibratory parts manipulation. We show that direction-dependent surface friction properties can be used in conjunction with a vibrating plate to help design friction-induced velocity fields on the surface of the plate. Theoretical, simulation, and experimental results are presented quantifying the anisotropic friction effects of textured surfaces such as micromachined silicon and fabrics.

Evaluation of asymmetric microfabricated surfaces using femtosecond laser process for microparts feeding

Previously, we found that an asymmetric microfabricated surface can feed microparts along using simple planar symmetric vibrations. Microparts move forward because they adhere to the asymmetric surface asymmetrically. To feed along 0402-type capacitors (size, 0.4 × 0.2 × 0.2 mm; weight, 0.1 mg), we used a slight stainless shim tape microfabricated by a femtosecond laser processing tool, specifically the double-pulsed femtosecond laser irradiation technique, to generate an asymmetric profile surface. We then evaluated the characteristics of the microfabricated surface, including the effects of decreased adhesion, the differences in profiles of the two inclined surfaces, the coefficients of friction in both the forward and backward directions, and the friction angle of the 0402-type capacitors in both directions. Using the results of feeding of these capacitors, we assessed the relationship between driving frequency and feeding velocity. We also assessed two other microfabricated surfaces generated by the single beam femtosecond laser diagonal irradiation technique. We evaluated the asymmetry of these microfabricated surfaces based on measurements using an atomic force microscope (AFM) system. We then performed feeding experiments of 0402-type capacitors with the same driving conditions using newly and previously generated surfaces. Experimental results were compared to assess the surface most appropriate for feeding 0402-type capacitors.

Feeding Submillimeter Microparts Using an Asymmetric Fabricated Surface with Symmetric Vibrations: Effects of Feeder Surface Materials on Feeding

We have previously shown that microparts can be fed along an asymmetric microfabricated surface using simple planar symmetric vibrations. Microparts move forward because they adhere to the microfabricated surface asymmetrically. We have also described the effects of sawtoothed surfaces on the movement of submillimeter-sized microparts; for example, 0603 (size, 0.6 x 0.6 x 0.3 mm; weight, 0.3 mg) and 0402 (size, 0.4 x 0.2 x 0.2 mm; weight, 0.1 mg) capacitors. In the present work, we studied the effects of feeder materials on the feeding of single layer chip capacitors (size, 0.25 x 0.25 x 0.35 mm ; weight, 0.06 mg). We found that the motion of submillimeter microparts was affected not only by inertia but also by adhesion due to electrostatic, van der Waals, and intermolecular forces, and to surface tension. These effects are dependent on the two materials that are in contact with each other. The four materials selected for feeder surfaces were microfabricated so that periodic sawtooth structures were present on their surfaces. We assessed micropart feeding using these surfaces, as well as the relationship between feeding velocity and vibration frequency. By comparing the feeding velocity on each feeder surface, we assessed the effects of feeder surface materials on the feeding of microparts.

Experiment and simulation of micro-part dynamics with roughness effect

In this study, we perform an experiment and develop a dynamic model that describes the planar motion modes of a micro-part, including two linear motions and one rotational motion, on a saw-tooth surface. In the experiment, the planar motion of the micro-part is obtained by a particle-tracking method. The rotation angle is measured from the principal axis of the micro-part image. In a simulation, contact between the micro-part and the saw-tooth surface is assumed to be the contact between a number of hemispheres on the micropart and the surface, which results in either a point contact or slope contact. The effect of the saw-tooth surface roughness on the contact force at each contact point is modeled as a field of normal vectors. In addition, the roughness of the saw-tooth surface is approximated by superposing white noise on an ideal saw-tooth profile and is used to evaluate the adhesion force. The results show that the model describes the motion modes of a micro-part. Furthermore, the simulated results of the two linear motions are in good agreement with our experimental results from a previous study. The proposed model can be used to improve the design of surfaces for micro-part transport.

Feeding of microparts along an asymmetric surface using horizontal and symmetric vibrations — Development of asymmetric surfaces using anisotropic etching process of single-crystal silicon

We previously showed that microparts can be fed along an asymmetric microfabricated surface using simple planar symmetric vibrations. Microparts move in one direction because they adhere to the microfabricated surface asymmetrically. We developed sawtoothed surfaces with an elevation angle of 20 deg and various pitches of from 10 to 100 micrometer on the surface of silicon wafer material using a dicing saw with a bevel type blade. We also evaluated the movement of sub-millimeter microparts such as 0603 (size, 0.6 × 0.6 × 0.3 mm; weight, 0.3 mg) and 0402 (size, 0.4 × 0.2 × 0.2 mm; weight, 0.1 mg) capacitors. Then we found that there were fabrication errors and cracks on the top of teeth, and they caused variations of contact between fed microparts and feeder surfaces, which affected the feeding stability of microparts. In the present work, we applied the etching process of single crystal silicon to develop higher accurate and uniform asymmetric fabricated surfaces. Using a silicon wafer with a plain orientation of [221], an asymmetric periodic structure is generated on its surface because the etching speed is different between forward and backward of the crystal face. Three types of etched surfaces were obtained by adjusting the etching parameter. The surface profiles of each surface were measured using a scanning electron microscopy (SEM) system. We also examined the tribologic characteristics by the measurements experiments of the angle of friction of microparts. Finally, we conducted feeding experiments of microparts using these surfaces and compared feeding velocity on each surface.