Recent years, an electronic technique has been developing remarkably, electronics control has been applied to various control systems. Many sensors and actuators have been implemented into those systems, and an energy efficiency and a performances have been improved more than before. However the system has been more complicated on the other hand, and much time is needed in order to develop the controller of the system. In this paper, a method of automatic controller design for those systems is described. In order to automate design of an electronic controller, a evolutionaly computation is applied. First, the framework how to apply the genetic algorithm to the automation of controller design is described. In particular, the coding of a chromosome is shown in detail. Next, how to make an evaluation function is represented with an air-conditioner as an example case, and the controller of the air-conditioner is developed automatically using our proposal framework. Finally, the evolutionary simulation is performed to confirm our framework.

View full abstract

We deal with a communication method that can be commonly adopted for both human-robot and robot-robot communications. We discuss a communication style by means of simple sound such as human hand-clapping or electrical beep sound. In this study, a hand-clapping language is introduced. The formal language specification is developed. A preliminary experiment is conducted with 2D mobile robot in a simulation environment and experimental interface for hand-clapping communication. Basic feasibility of the proposed communication method is demonstrated.

View full abstract

Major advantages of a microactuator driven by light energy are that optical excitation enables noncontacting thermal energy supply and remote operation. Photothermal-drive is the method to get driving force by means of the thermal stress induced by the light energy. A micro-cantilever is the simplest element of a micromachine, and is driven by photothermal-effect using a modulated laser diode of 13mW. In the previous study, nanometer order of displacement is obtained by drive of a steel micro-cantilever. In this study, bimorph of aluminum and photoresist is employed that is made by improved fabrication method of a cantilever, and displacement of 630μm is obtained. Drive characteristics such as time response and frequency response of the bimorph micro-cantilever are measured. Applying the principle of photothermal driving to a bimorph microstructure of arch shaped cross, micromotion is excited on the bimorph microstructure by the periodic laser irradiation. A self-propelled bimorph microstructure is realized.

View full abstract

Vibration amplitude of a cantilever used in an atomic force microscope (AFM) measured by using the optical lever method may include errors and correction of the amplitude depending on the vibration frequency is necessary. Therefore, the correction factors for vibration amplitude of the cantilever with an added mass, spring and damping at an end were derived theoretically. These correction factors are useful for ultrahigh accuracy measurements, especially dynamic measurements, using the AFM.

View full abstract

A molecular dynamics simulation using a coarse-grained bead-spring model was applied to investigate the spreading characteristics of monolayer lubricant films on magnetic disks. One of the end beads of a perfluoropolyether molecule was fixed to the disk surface in order to model a bonded molecule. The simulated diffusion coefficient of mobile molecules for various coverages of the bonded molecules was in good agreement with previous experimental result using the half-dip method. The simulated relation between the coverage and bonding ratio was also in good agreement with the experimental one.

View full abstract

Raman imaging was carried out to measure strain mapping at around indented Si surfaces. Two or three Raman peaks of Si were observed at swells around the triangular indentation dimple made by Berkovich type indenter. On the other hand, single Raman peak with high Raman shift was observed at the center of indentation. Raman shift images of the indentation reveals that there are compressive strain at the center of dimple and tensile strain at the swelled surroundings. The peak separation is induced by biaxial or triaxial stresses during the indentation process. Calculated strain images using FEM (Finite Element Method) showed good agreement with the experimental results.

View full abstract

Since the discovery of carbon nanotubes (CNTs), the remarkable structural, electrical and mechanical properties as carbon material has attracted many researchers, and the synthesis of high quality CNTs using various methods have studied. Kusunoki et al. have reported that CNTs with high-density and well-alignment are formed vertically on a silicon carbide substrate. CNTs on SiC substrate could be used for tribomaterial as high friction or wear proof materials because each CNT covalently bonds with the SiC substrate. Thus, we have studied about wear property and wear mechanism of CNT film by micro-scratching test. Longer CNTs showed lower critical load than shorter CNTs. Considering the influence of the length and diameter of CNTs, wear property and wear mechanism of the CNT film were discussed.

View full abstract

This paper describes a micro-drill processing system of precise mechanical parts, using an electromagnetically levitated stage. Electromagnetically levitated stage is free from friction, so that convenient for measurement and control of small forces which occur in between a tool and a work-piece. In this paper, the effectiveness of this system is shown by an experiment of detecting the contact of micro-drill and work-piece and making pierced holes of 0.1mm diameter in a steel plate of 1mm thickness.

View full abstract

Advances of head disk interface (HDI) were summarized from the viewpoint of tribological requirements. Next, dimensions and construction of the updated HDI was introduced. Finally, future technologies to allow for a further increase in recording density were discussed.

View full abstract

Laser-assisted magnetic recording is one of the novel technologies for achieving a magnetic recording density of more than 1Tb/in^2. In this technology, it is suggested that there is serious issue for the ultra-thin liquid lubricant films on the disk surface. Because they are heated to high temperature with laser beams. In this study, we focused on the thermal stability of the lubricant film in laser-assisted magnetic recording. In other words, the behavior of lubricant film due the laser heating was investigated experimentally and discussed. As a result, it was found that the lubricant depletion was observed and could not be replenished. In addition, the effects of laser power as well as the laser irradiation time on the lubricant film depletion were studied and clarified.

View full abstract

Flying height of hard disk drives was measured based on Phase Comparison Michelson Interferometry (PCMI), which utilizes the phase comparison of two interference fringe patterns formed respectively on the inner surface of a glass disk and the air bearing surface of a flying head slider through the glass disk. To suppress Interference noise and to further enhance measurement accuracy, low coherent white light was adopted as an Illuminating source to replace high coherent laser. The measured results show that the application of white light illumination effectively improves interference fringe patterns, and greatly minimizes the measurement error of extracting the ridgeline in comparison with a laser. Sub-10nm flying height was measured with high accuracy and good repeatability.

View full abstract

Recently the spacing between the slider and the disk has been reduced to 10nm or less, and analysis of the slider dynamics becomes increasingly important. To perform this analysis, the highly accurate and numerically stable cubic interpolated propagation (CIP) method was applied to the 2-dimensional molecular gas-film lubrication (MGL) equation. First, static pressures caused by running discrete track media (DTM) are shown quantitatively (Case I). Secondly, dynamic pressures caused by the translational motion of a running disk (Case II) and a running wavy disk (Case III) having small amplitudes under a fixed finite-width slider were analyzed by the CIP method and were found to be in good agreement with the results obtained by the linearized analysis. The dynamic pressure generated when a running wavy disk has a large amplitude under a fixed finite-width slider accounting for the van der Waals pressure were shown quantitatively. Dynamic pressures caused by moving single projeciton (Case IV) and running disk with step (Case V) under a fixed finite-width slider were also analyzed by the CIP method and were shown quantitatively.

View full abstract

To achieve ultra-low flying height, magnetic spacing variations due to manufacturing tolerances, environmental variations, and write-induced thermal protrusion need to be reduced. To solve this problem, we have developed a thermal flying-height control (TFC) slider that carries a micro-thermal actuator. Using the actuator, the magnetic spacing of these sliders can be controlled in-situ while the drive is operating. In this report, temperature rise on the air-bearing surface (ABS) of the slider induced by heat from the heater was measured by infrared rays. The temperature rise measured by infrared microscope agreed well with the temperature rise calculated by the measured resistance change of read element. It was also roughly corresponding to the simulated result. These facts showed the accuracy of the easier measurement method, that is, observing read element resistance change, and the validity of the simulation. The temperature rise in non-flying condition and that in flying condition are significantly different. Therefore, it is necessary to measure it in flying condition for exact evaluation.

View full abstract

This paper describes the interactions between flying head sliders and ultra-thin liquid lubricant films in hard disk drives. In this study, two types of lubricants (A20H2000 & C2-2000) were tested and the surface energy of the test lubricants was investigated. In addition, the dynamics of the slider touchdown and takeoff hysteresis behavior was also evaluated by using Laser Doppler Vibrometer (LDV) and Acoustic Emission (AE) sensor. As a result, it was found that touchdown velocities of A20H2000 was smaller than that of C2-2000 and the takeoff velocities of A20H2000 and C2-2000 were almost same. Therefore, it was suggeseted that the slider hysteresis behavior may not be dependent on the surface energy of the ultra-thin lubricant films.

View full abstract

The effect of temperature on the spreading characteristics of ultra-thin liquid lubricant films has become more and more important in current hard disk drives. In this study, the spreading of molecularly thin Perfluoropolyether (PFPE) lubricant films on the carbon surfaces was investigated experimentally, varying the temperature of the micro-ellipsometer test stage. Three types of the lubricants ware used. The apparent diffusion coefficients of the test lubricants were also evaluated and compared with the trend of the bulk lubricant viscosity change for temperature. As a result, the temperature dependence of the spreading characteristics of lubricant films was clarified and it was found that A20H lubricant has the highest robustness for the temperature change among the test lubricants.

View full abstract

Mechanical characteristics of a liquid meniscus bridge were investigated experimentally using a newly developed apparatus. In the present study, characteristics of the force curve and the vibration transfer of a liquid meniscus bridge between a sphere and a plane were investigated. From the force curve results, difference between the maximum meniscus forces of the approach process and that of the withdrawal process was found and the hysteresis was observed. It was found that these phenomenon could be understood by considering the advancing and receding contact angles. From the vibration transfer results, the experimental resonance curve was similar to the theoretical curve obtained using the VCA model when the excitation amplitude was small, but at the excitation amplitude increases, the experimental results tended to approach the theoretical curve obtained using the VBP model. Moreover, the spring constant of the meniscus bridge was found positive when the contact angle was large.

View full abstract

In the head-disk interface (HDI) of a hard disk drive (HDD), lubricant deformation may effect on flying characteristics of the head slider, as the flying height decreases. To examine behaviors and instabilities of ultra-thin but continuum polar liquid films, the long wave theory was employed, which is the time-evolution for the shape of thin liquid film and includes surface tensions and surface forces such as the van der Waals forces (or disjoining pressure). The polar lubricant was found to be dynamically unstable due to the attractive or repulsive force of the polar component. Stability/instability and time-evolution of the polar liquid surfaces were numerically analyzed and the steady-state liquid film configurations were quantitatively obtained.

View full abstract

In the head-disk interface (HDI) of a hard disk drive (HDD), lubricant deformation may cause the degradation of flying characteristics of head slider, as the flying height is decreasing. Dai et al. analyzed washboard effect as the stability/instability problem of the lubricant surface from the view point of shear stress effects caused by slider vibration. In this paper we analyzed the similar problem considering i) the van der Waals attractive pressure on the lubricant surface from the slider, ii) the air film stiffness and damping dependent on excitation frequency and iii) the shear stress coefficient. In the natural frequency of the air film, the lubricant deformation may grow by the shear stress effect at the lubricant surface.

View full abstract

To ensure the reliability and durability of hard disk drives, molecularly thin polymeric liquid films of perfluoropolyether (PFPE) coated on the disk surfaces possess a mixed structure consisting of molecules bonded to the disk surfaces and non-bonded mobile molecules. Aiming to clarify the influence of film composition (mobile/bonded) on tribological performance, we measured friction properties of two types of 2-nm-thick PFPE films (polar Zdo12000 and nonpolar Z03) under lightly loaded (loading force: 0-1mN) and quasi-static (rotational speed: 2.1mm/s) conditions as a function of elapsed time. The friction force of Z03 remained unchanged with time and it increased linearly with loading force. In contrast, accompanying with the development of bonded molecules over time, the fiction force of Zdo12000 increased with time and transited to a nonlinear increase with loading force as the time proceeded.

View full abstract

This paper describe precise modelling about the friction characteristic of Head assembly in HDDs. In the recent research, the track pitch is more and more narrow for the increasing TPI. It is said that it is necessary to suppress the disturbance which was neglected in the part researches and to comprehend a behavior of each disturbance. In the following control system in HDDs, the head assembly was influenced the effect of several disturbances, e.g, RRO, flutter vibration, force disturbance, and so on. At the force disturbance, it caused by wind force, external shock, tension force of Flexible Printed Circuit, and friction. These disturbance recomposed between the cause of disk rotation and other effects. In this paper, we proposed a precise mathematical model of the disturbance caused by friction characteristic without effect of disk rotation. The experimental setup consists of the VCM with head arm and head assembly. The validity of the proposed mathematical model was verified that experimental setup.

View full abstract

This paper describes a magnetic head positioning mechanism in hard disk storages, which consists of a novel dual-stage actuator and uses drag forces acting on the contact slider. The contact slider is designed to be rotated by the drag forces and the rotation of the slider can be used as a fine actuator for the head positioning. First, the equations of motion of proposed positioning mechanism were derived. Static characteristics of this mechanism were investigated with the equations of motion. The equations were also linearlized and a frequency response of this mechanism was investigated. Next, transient responses were calculated for a certain variation of the drag forces. As a result, ability of the proposed positioning mechanism to position the magnetic head to a narrow recording track in near future was shown.

View full abstract

Numerical fluid simulation based on voxel mesh method was applied to a 3.5-inch hard disk drive and the results were compared with the experimental results obtained by PIV (particle image velocimetry) system. The results showed that the velocity distributions agree well and this method is useful for such a complicated geometry as hard disk drives.

View full abstract

We proposed a new actuator that was composed by a layered piezoelectric element and a displacement amplitude mechanism. A new shape of the actuator which was like a diamond realized large working-distance with high resonance frequency. Moreover, as the two piezoelectric elements worked to counterbalance each other's reaction force, the new actuator never excite a spin-stand which was estimation tester for high density magnetic recording. We compared an original model with a newly improved one which was optimized by the integrated design method. The optimized design model increased the working-distance dramatically without its declining crossover frequency of the open-loop transfer function.

View full abstract

An objective lens actuator using inner magnets for optical pickups was developed. The main magnets are paced outside the focusing coils, and the inner magnets are placed inside the coils. The inner magnets produce magnetic flux density in the tracking direction. Subsidiary driving forces generated in the focusing coils by the inner magnets when the moving part is moved in the tracking direction cancel the rolling moment caused by the main driving forces generated by the main magnets. The tilting of the actuator caused by the rolling moment is 90% less than with a conventional actuator without inner magnets.

View full abstract

To reduce the position deviation of the beam spot on the detector when there was a significant variation in temperature, we developed the jisso structure of an ultra-slim optical pickup. We clarified opticle parts that have a strong effect on the position deviation on the detector and modified the combination of the ways to fix these optical parts to the optical pickup case. The results that we calculated show that the position deviation on the detector of the improved optical pickup is reduced to below 3μm in ambient temperatures between 0 and 65℃.

View full abstract

We developed a light source module using a high-power light emitting diode (LED). Production of long life LED chips requires the thermal resistance of its LED module to be reduced. We analyzed thermal conductivity in an electrically conductive adhesive used in a LED module. Results confirmed that the thermal conductivity of an electrically conductive adhesive, including contact thermal resistance, is important when analyzing thermal conduction in a LED module.

View full abstract

Mechanical characteristics of transportation equipment for patients and its physical effect on the patients' body are discussed. Three dimensional acceleration of stretcher used in the hospital, ambulance and doctor helicopter are measured. Angular velocity of the stretcher is also acquired. In case of stretcher transport, acceleration gives little effect on the patients' body while angular velocity causes uncomfortable. Mathematical model that derives ride discomfort is used to estimate the ideal rotation method during stretcher transport. Next, an actively controlled stretcher (ACS) for ambulance is developed since the emergency brake causes blood pressure variation. The ACS reduces the blood pressure variation and gives good ride comfort during the transportation. Finally, mechanical characteristics of doctor helicopter are analyzed and it is found that helicopter transport gives lesser horizontal acceleration than ambulance one but it is expected to provoke motion sickness because of the huge vertical acceleration below 1[Hz].

View full abstract

We have developed a novel scanning micro-indentation tester with real-time observation of measuring point. A laboratory-made indenter and cantilever-type load cell were connected to the microscopic objective driven vertically with a commercial piezoelectric positioner, so that the point of indentation can be observed in real time during the measurement of load-displacement curves. We measured the distribution of elastic modulus and surface topography of bone-cartilage complex specimens with this tester, and compared them with the surface histology stained with Alizarin Red to find a wide variation of elastic modulus even in a calcified region stained uniformly. The tester would be useful in measurement of local elastic properties of tissues.

View full abstract

The perceptive recognition mechanism on tactile sense provides important information to progress alternative equipments, research and development of the robotics and welfare engineering. In the present research, we investigate the influence of kinesthesia using psychophysical in order to establish a new hypothesis and a mathematical model on the recognition mechanism of human haptic perception. We conduct a new experimental method using psychophysics, in which several pairs of two-dimensional convex-concave figures were presented to human subjects. In a series of experiments, the human subjects distinguish a circle from eight ovals possessing an equivalent area to the circle. These figures are formed as two-dimensional convex-concave relief using a special printer and touched by their fingertips or thenars. We examined three cases: 1) restricted finger movement, 2) free finger movement, 3) free finger movement and refrigerated specimens. From these results, it is found that the two dimensional figure is recognized mainly by the tactile sense only without a specific active movement, and that a peak of the standard deviation of the correct answer observed in the cases 1) and 2) disappeared because a specific mechanoreceptive unit is deteriorated and ceased emitting noise under low temperature.

View full abstract

This report focuses on a development of a 3-dimensional drag sensor. Three strain gauges and a nonmetal cylindrical material constitute the sensor. The strain gauges are put on the side of the cylindrical material at intervals of 2π/3 radians. The strain gauges detect the deformation of the cylindrical material. The output voltage of the gauges can be approximated by sinusoidal functions with a phase difference of 2π/3 radians. We show that the contact angle and the load are estimated by the approximated sinusoidal functions and measured output voltage.

View full abstract

This paper is concerned with the development of the wearable sensor system for recognizing Braille. A compact wearable sensor using a PVDF (Polyvinylidene Fluoride) film is developed. The sensor output is measured with the sensor mounted onto a fingertip moving over Braille manually. A compact measurement part, a robust recognition part and a voice output part are also proposed. The wearable sensor system is fabricated by combining the sensor with these parts in order to teach the user the recognition results by real-time voice output. The sensor system is examined experimentally whether it is effective to recognize Braille. The obtained results show that the wearable sensor system is effective to recognize Braille.

View full abstract

This paper reports on design, fabrication and testing of a prototype Polyvinylidene Fluoride (PVDF) tactile sensor for endoscopic application. This sensor measures compliance of biomedical tissue. It consists of a compliant central cylinder made of silicone rubber and a rigid cylinder made of aluminum. A relative deformation between adjacent parts of the contact object is used to measure the compliance. The theoretical analysis of the sensor is made and two sensors which have different compliant central cylinders are made, based on the theory. Experimental values given by the sensors are compared with theoretical values. An Electrical teeth brush is used as an indention and vibration device and silicone rubbers referencing elasticity of biomedical tissue are objects. First, fundamental characteristics of the sensor were examined. The object was vibrated to the fixed sensor. Next, the sensor was vibrated to the fixed object with consideration with clinical practice. The results showed that the experimental values have correspondences with the theoretical values and the sensor can measure elasticity of biomedical tissue.

View full abstract

Comparison of three-dimensional (3D) acceleration between ambulance transport and helicopter one and effect of the helicopter transport on human body are discussed. The 3D accelerations of the helicopter and the ambulance are measured using 3D accelerometer and its characteristics are evaluated using frequency distribution, discrete Fourier transform, statistical approach and exposure limit introduced by ISO2631. The experimental results suggest that the effect of the horizontal acceleration of helicopter on the human body is smaller than the ambulance while the vertical acceleration of the helicopter is large in the frequency domain of below 1[Hz] and is expected to provoke motion sickness. Moreover, hovering causes body resonance of the whole body of helicopter around 25[Hz] and huge acceleration which approaches the exposure limit of reduced comfort boundary for one hour.

View full abstract