The authors have proposed a new dental treatment method by using powder jet deposition (PJD) technique to make coatings on human teeth. The method utilizes hydroxyapatite (HA), which is the main element of human hard tissue, as a restoration material. The coating process is achieved by high speed impacts of the particles on a tooth, and it can be carried out under room temperature and the atmospheric pressure. The thick PJD film is obtained through the accumulation of fractured parts of particles. This study focuses on the microstructures of the HA particles and the deposited film. To investigate the effect of particle crystal structures, two types of HA particles were produced: one (Type A particle) is covered with an amorphous surface, whose thickness is approximately tens of micrometers; the other one (Type B particle) is a type of complete-crystal-growth particles, which are produced by heating the particle A at 230°C for 12 hours. The film fabrication experiments were performed with these particles and machined areas were observed with a scanning electron microscope. It was found that the fabricated film with Type A particles was spalled during blasting. In contrast, the fabricated HA film with Type B particles is well deposited without film spalling. To further investigate the microstructures of the HA film, observations with a transmission electron microscope were conducted. The dark field image of the film with a Type A particle implies that the created HA layer consists of HA crystals of one to tens of nanometers. The bright field image indicates that cracks of approximately 300 nm generated in the film. Thus the mechanical strength of the film fabricated using the Type A particle is not strong enough against the subsequent particle impacts and the pressure of blasted air. In contrast, cracks were not observed in the film created with the Type B particle.
This paper discusses surface functional design by depositing various materials with regular pattern. First, three examples are introduced: (1) Thermal conductivity of pitch-type carbon fiber is higher than those of metals and thus the chopped fibers were deposited with spray coating on a resin plate to increase the overall thermal conductivity along the plate. (2) Silver nanoparticles were deposited and fixed keeping regular spacing, and attainable antibacterial activity was examined to make clear the minimum quantity of expensive silver particles. (3) Silica particles were self-assembled on a silicon wafer configuring lattice pattern to compromise both of optical reflectivity and wettability. It was confirmed that deposited particles shorten the drying time because the pinning hold the droplet edge and thus the surface area large, while reflectivity was kept by the smooth surface between the lattice particles pattern. Spatial frequency of the surface structure was often discussed as well as the material property, because regular cross-sectional profile or texture often changes the surface functionality. Finally, design methodology was discussed. Assuming different functions are related to respective spatial frequency component of the texture or material deposition, and the combination of plural frequency components should be integrated on the surface cross sectional profile to compromise plural functions simultaneously. Case study was the combination of friction, wettability and optical functions.
A new methodology to automate machining operation planning is proposed. A new machining operation plan is reconfigured from past case data or past machining operation data stored in the database. Machining information, e.g. cutting tool, cutting conditions, tool path pattern, is associated with a machining feature. A machining feature is recognized from the 3D CAD model of the finished shape. Sets of machining information are stored as the past case data with their 3D CAD models. In order to generate a new machining operation plan of a new product, machining features are recognized based on topological relationship of the 3D CAD model first. Then, each of machining feature is compared with machining features contained in 3D CAD models stored as the past case data quantitatively in terms of shape, size and material. Finally, the most similar machining feature is selected as the reference one. The machining information associated with the reference machining feature can be applied for each machining feature recognized in the new product. Finally, the NC program to perform a new machining operation is generated automatically. The usability and effectiveness of this proposed system to save time and effort of human operator was verified through a case study.
CFRP (Carbon Fiber Reinforced Plastic) is widely used for airplane, automobile and general machinery because of its high specific strength. CFRTP (Carbon Fiber Reinforced Thermo-Plastic) is especially attracting the attention of the viewpoint of recycling and molding speed. In machining of CFRTP, softening of matrix resin causes burrs due to high cutting temperature. In this study, side milling tests are carried out by changing cooling condition (Dry/Cryogenic). Liquid nitrogen (LN2) is used as coolant for cryogenic machining. Cutting temperature, cutting force, surface integrity and tool wear are examined. The cutting temperature of dry condition and cryogenic condition shows 51.2°C and -172.9°C, respectively. The cutting temperature of dry condition is higher than the glass transition point of matrix resin (PA66). It is thought that softening of matrix resin occurs under dry condition. The employment of cryogenic milling effectively suppresses burrs. It is also pointed out that the tool wear is larger than that in dry milling. It is thought that the elastic module of matrix resin influence the occurrence of burrs. In order to examine elastic module of matrix resin (PA66) by changing cooling condition (Room temperature/LN2), the indentation test are carried out on machining center. The elastic module of matrix resin in cryogenic condition is higher than that in room temperature. It is shown that the occurrence of burrs is related to elastic module.
This paper deals with the geometrical analysis of the surface roughness of a radius end milled workpiece with an inclined surface using the contouring and scanning cutter path methods. In the case of contouring, first it was classified into three types of cutting edges for generation of inclined surface. Secondly, three equations of the theoretical roughness of the machined surface were lead based on the geometrical analysis for each type. The calculation values of surface roughness almost coincide with the experimental values, therefore the validity of the analytical method is cleared. In the case of scanning, first the envelope surface of the bottom and corner edges was defined as the lower half surface of the torus. Secondly, the calculation and estimating method of the envelope curve which was obtained by the outside line of the projected torus surface is shown. The estimated values of surface roughness almost coincide with the experimental values, therefore the validity of the analytical and estimating method are cleared too. Finally, the selection of the scanning method is more effective in order to achieve highly accurate machining.
A new CNC lathe with a tandem table unit driven by two linear motors has been developed for machining non-axisymmetric curved surfaces by turning. This lathe, which equips 4 axes (X1 X2, Z and C), enables to realize the NACS-turning (Non-Axisymmetric Curved Surfaces Turning) with high speed machining synchronizing with the spindle rotational position. The key factors for this turning method is not only to realize precise tool tracking ability for the commanded position but also to cancel the inertia force caused by the rapid motion with high acceleration and deceleration. Therefore, the dynamic response of each axis is required so that the curved surfaces is machined accurately with the rapid motion, high acceleration, and jerk. In this study, we introduce a new CNC lathe with 4 axes including a tandem table unit that has achieved the acceleration and the deceleration of over 100m/s2 by the use of the tandem linear motors driving system. Each table is controlled synchronizing to obtain the accurate trajectory on the designed curved surface by canceling the inertia force during machining motion. In this report, the fundamental dynamic performance of the table motion of the CNC lathe are measured and evaluated. The effectiveness of suppression of the vibration transmission to the CNC lathe during the motion control for the curved surfaces is also evaluated.
In order to measure the two-dimensional distribution of the thickness of a metal layer coated on a dielectric layer at a time, we propose to use a micro-lens array (MLA), instead of a conventional single plano-convex lens, by which lots of surface-plasmon-resonance (SPR) dip patterns could be observed from a modified Otto configuration. The individual micro lenses produce circular ring-shaped SPR dip patterns in reflection, which enable us to estimate the thickness of the metal with high sensitivity and precision with ease. A spatial resolution is determined by the size of each lens and is 300 μm in diameter. As a proof-of the principle experiment, we measured the thickness of a 50nm-thickness Au film with precision ±0.9 nm for an area of 2.7 mm×2.7 mm. A method for improving the spatial resolution further is discussed.
A micro-scale texture generated on the surface characterizes wettability, friction and optical property of the substrates. In recent years, demands for adapting such functional surface to the large scale and complex structure have increased in a variety of industries. In general, the micro-scale texture can be generated by the ultra-precision machining process, which has high flexibility and high precision. In this study, for reduction in a lead time, in order to construct the micro structure and form a shape by milling at the same time, a non-contact positioning system driven by a giant magnetostrictive element (GME) is newly proposed. Besides, it is not possible to measure the displacement of a milling tool with a displacement sensor. Hence, this positioning system uses the GME not only as an actuator but also as a sensor simultaneously in order to estimate its displacement. As mentioned above, utilizing an actuator as a means of sensing its own displacement is referred to as a self-sensing function. Furthermore, by using estimated displacement for feedback control, hysteresis of a GME can be compensated. Therefore, this positioning system can be driven with non-contact without additional displacement sensor. From the performance evaluations, the positioning system provides high resolution and hysteresis compensation with self-sensing function.
Dry hobbing, which is a gear processing method without cutting oils, is useful for cutting cost and reducing environmental pollution. However, the dry hobbing has problems, for example, increase of the cutting temperature, cutting surface damage by the chips, and so on. This study proposes a new dry hobbing method "vibration hobbing" for the purpose of reducing the cutting temperature mainly. The method gives axial micro vibration to a rotating hob by a vibration generator. This paper explains the structure of the vibration hobbing machine which we developed, and shows the effectiveness of the machine by experimental results. We carried out the vibration hobbing as finish machining on the following conditions : the cutting depth is 0.34 mm, the hob frequency is 740 Hz, the hob amplitude is about 2μm, the cutting speed is 40.8m/min, the hob feed is 1.0mm/rev, the module is 1.75, and work hardness is HRC50. As the result, the black chips were changed into the white chips by the vibration. This result shows that the vibration hobbing reduces the cutting temperature. Moreover, when the work hardness is HRC55 and the hob amplitude is 1.2 μm, the height of feed marks on the gear tooth surface are reduced by the vibration hobbing. Thus, the effect of vibration hobbing is reducing the cutting temperature and the height of feed marks on the gear tooth surface for high hardness materials.
Recently, the method of micro fabrication has been important in the field of manufacturing, and a demand on microfabrication has been increasing for a new micro functional devices such as photonic crystals. In this research, we propose a new method of microfabrication using a metal ion solution, a conversing laser and photocatalyst nano-particles. When a conversing laser is illuminated in the metal ion solution including photocatalyst nano-particles, the photocatalyst particles are excited and metal ions are expected to be reduced only at the vicinity of beam waist. Then, scanning beam waist, we can fabricate the three dimensional micro structures. In this report, we estimated a mechanism of this proposed method through some verification experiment and investigated the capacity of this method. First, we made a fundamental experiment by changing the wavelength of focused beam in the silver ion solution including TiO2 nanoparticles and investigated a proper wavelength of focused beam. Second, we made some verification experiments under variable solution conditions and investigated the role of each chemical reagent of solution. Third, we estimated the mechanism of this fabrication method by these experimental results. Finally, we developed the experimental system of automatically scanning the focused beam and fabricated some micro structures using this system. From these result, we indicate the capacity of this method which can fabricate the free-form curves and three dimensional lattice structures with the process resolution of several micro meters.
In forming of glasses frame, bending and inverse bending of rim wires with 4 rolls are usually employed. Only an inverse bending roll, the 4th roll, can change the position to control the curvature of the rim wire. A deriving method of inverse bending roll position is proposed in this study. The proposed method requires not the computational simulations but only some simple steady inverse bending experiments to obtain a relationship between inverse bending roll position and bent curvature which depends on machine condition and bent wire. The experimentally obtained relationship is used in the formulation of deriving the inverse bending roll position. To validate the proposed method, a real glasses frame shape is formed by the proposed and conventional methods. The difference between the designed and formed shapes is evaluated by a sum of absolute shape deviation. The value by the proposed method is smaller up to about 75% than that by the conventional method.
When train passes through the railroad joint at the heel of tongue rail of railroad switch, impact vibration is induced due to the step difference of the joint. This impact vibration transfers to the front rod, which is the attachment device located on the toe of tongue rail and connected with position checker device, induces the wear of bearing and resulting switching failure. In order to clarify the mechanism of the wear, we have developed the finite element model of the railroad switch for the vibration analysis. The model is validated by the acceleration and axial force of the front rod measured in track open for traffic. Our model enables us to predict the wear amount from the contact pressure and sliding velocity of the bearing part. Combining with wear test and finite element model, we predicted the wear amount of the front rod in the track and found that the time to reach the limit of wear is over 80 years. Therefore, the present replacement period is thought to be extensively conservative. Our final goal is to propose the appropriate maintenance schedule for any other type of railroad switch under various working conditions.
The effect of processed surface condition on low cycle fatigue life of Ni based super alloy, Alloy 718, was investigated. Observation of turning surface indicates that the roughness is fairly small, i.e. Ra < 1 μm, however, many scratch are found. Compressive residual stress is measured on the surface. Specimen subsurface condition consists three characteristics including fine grained and plastically deformed layers and bulk material. Fine grained layer is divided into three layers. Specimens were prepared by electropolishing in order to remove the fine grained and plastically deformed layers. Low cycle fatigue tests were performed on these specimens. Under strain range Δε = 0.8 %, fatigue lives of the specimens with turned surface are longer than those of the electropolished specimens. On the contrary, the surface conditions have no effect on fatigue lives under Δε = 1.4 %. Fatigue cracks initiate from surface scratches and inclusions on the turned surface, while they are initiated from slip band for electropolished specimens. Under the test conditions in this study, residual stress has the strongest correlation with the low cycle fatigue lives affected by the surface conditions. To consider scratch, residual stress and microstructures are important to decide low cycle fatigue design and machining method.
We develop a three dimensional (3-D) flaw imaging system using the full waveforms sampling and processing (FSAP) technique and an ultrasonic matrix array transducer. In FSAP, each array element is sequentially used as an emitter and all other array elements are used as receivers. By changing the emitting element, we obtain a set of signals of every two-element combination. The combination of all signals enables the generation of focal beams at any point in the region of interest. Using the focal beams, we can reconstruct high-resolution 3-D images of flaws. In this study, we introduce massively parallel calculations with graphics processing unit (GPU) to accelerate the beam-forming in FSAP. Here, we implement the GPU accelerated FSAP on a signal acquisition system with a multiplexer, which can rapidly switch the ultrasonic transmission and reception. We validate the performance of the FSAP imaging system by 3-D numerical simulations with the elastodynamic integration technique and experimental measurements with an acrylic specimen. The results show high-speed calculation of the beam-forming, and accurate and clear flaw images.
Pressure pulsation is caused by the flow ripples from a positive displacement hydraulic pump. It transmits throughout fluid power equipment and causes unwanted excitation of the mechanical parts. In many practical applications, a Helmholtz type hydraulic silencer may be used to attenuate such pulsation. It is the preferred solution on account of its simple structure and high attenuation performance. However the distinctive drawback of this silencer is that it is effective only within a narrow range of the attenuating frequency. Therefore, the silencer is only suitable for use in the hydraulic systems running at constant pump rotational speeds. The purpose of this research is to develop a novel silencer for hydraulic systems that have a fixed displacement pump driven under variable speed. Firstly, a mechanism for adjusting the resonant frequency has been pro-posed. This works by changing the volume of the silencer. Secondly, a prototype of the novel silencer was designed using a new distributed parameter system model, in which the vessel volume was modelled as an annular fluid line. Finally, the at-tenuation characteristics of the prototype silencer were verified by measuring the transmission loss and insertion loss under various conditions, and comparing them with the calculated results.
Magneto-rheological properties significantly depend on the formation of aggregates of magnetic particles. In the present study, we focus on a ferromagnetic rod-like particle suspension to discuss the phase change of aggregate structures of magnetic rod-like particles in thermodynamic equilibrium. Hence, we here adopted Monte Carlo method, which is a powerful simulation technique for an equilibrium situation, in order to investigate the dependence of the phase change in aggregate structures on the magnetic field strength, the magnetic particle-particle interaction strength, and so forth. Internal structures of particle aggregates are discussed quantitatively in terms of order parameters. The main results obtained here are summarized as follows. In a weak applied magnetic field, the rod-like particles tend to aggregate to form thick linear chain-like cluster if the magnetic particle-particle interaction is sufficiently large for clusters being formed. The neighboring clusters align in the opposite directions to each other. As the magnetic field is increased, thick chain-like clusters grow and become thicker by absorbing the neighboring clusters that align in the opposite direction to the magnetic field direction. This phase change of aggregates is quantitatively verified in the characteristics of the order parameters.
Numerical simulations of single bubble volumetric oscillations have been conducted by using Gilmore model (Gilmore, 1952), to study the influences of liquid viscosity and surface tension on the theoretical threshold value (MIt) of the mechanical index (MI) that has been successfully used for the safe application of diagnostic ultrasound. MIt is defined as the minimum value of MI at various bubble radii and ultrasound frequencies when the temperature inside a bubble reaches 5000 K. The results show that MIts for water and blood are 0.314 and 0.405, respectively. It is found that the greater the viscosity or the surface tension is, the greater MIt is. It is also found that the ultrasound center frequency that gives MIt has a negative correlation to the viscosity and surface tension.
Japan Agency for Marine-earth Science and Technology (JAMSTEC) has been developing a 300 L class constant temperature bath to calibrate temperature sensors monitoring ocean water temperatures. This system consists of a constant temperature bath which requires the temperature stability within ±1 mK. The purpose of this study is to investigate experimentally the performance and accuracy of the 300 L class constant temperature bath. To evaluate the temperature distribution within the bath, we first evaluated the measurement uncertainty of a 12 channel thermometer to ensure the meaningful results with temperature differences at 1 mK level. Results using this 12 channel thermometer and another reference thermometer indicated that although temperature stability of the 300 L class constant temperature bath was within ±1 mK at each measuring point, the total calibration time was longer than the targeted time. In order to elucidate the reason for this, the transient temperature distribution was measured with the 12 channel thermometer, and it was found that a region within the bath takes a longer time to reach stability. Moreover, measurement of the velocity distribution within the bath using Particle Image Velocimetry showed that a lack of turbulent flow in the bath caused this delay.
The characteristics of biogas-oxygen diffusion flames were experimentally investigated using small counterflow burners, where the apparent equivalence ratio was set to unity. The flame thickness and flame diameter were determined as functions of the inner diameter of burners, the distance between burners and the flow rate of gases. When burners with large inner diameter were used, diffusion flames were observed in small burner distance. The flame thickness and flame diameter decreased as the burner distance became smaller, and they increased as the flow rate became larger. The flame stretch had a great influence on the flame thickness, i.e. the flame thickness decreased monotonously as the flame stretch rate became larger. In addition, the relation between flame thickness and flame stretch depended strongly on the inner diameter of burners and the flow rate of gases.
The recuperative burner and the regenerative burner that applied exhaust heat recirculation are proposed as energy-saving technology in furnaces in a practical use. Although, heating efficiency has the proportional to the rate of the exhaust heat recirculation, the burned gas temperature and NOx emission increases in the conditions of high exhaust heat recirculation. The newly developed two-stage combustion method was proposed in this research for improving NOx reduction. The two-stage combustion method is often applied as low NOx technology with using exhaust heat recirculation. This research proposed a tubular flame for the first stage of two-stage combustion. Since the tubular flame can sustain a stable premixed flame in rich mixture in the first stage, NOx generated in the primary burner suppresses due to low flame temperature in this proposed system. In addition, the inlet gas temperature in the secondary burner can be adjusted by intermediate cooling section that placed between the primary burner and secondary burner. This reduction of the inlet gas temperature is also contributed to reduction of NOx in the secondary burner. Results show that the first flame was successfully formed until equivalence ratio 1.7 by using tubular flame in the primary burner. The smallest NOx emission appeared in the condition that the adiabatic flame temperature become equilibrium to the amount of heat reduction calculated from the intermediate cooling section. The NOx emission is reduced to 16.3 ppm (O2=0%) at the equivalence ratio of 1.67 in the primary burner without intermediate cooling tube. This value is about 1/6 of the single-stage combustion with Bunsen flame, and about 1/4 of the two-stage combustion with partially premixed flame in the primary burner.
Global warming and air pollution mainly caused by emissions of CO2 and NOx are serious problems. We focus on a lean H2-O2 premixed flame because H2-O2 premixed flame emits no CO2 and NOx. H2-O2 mixture also has dangerous properties such as large burning velocity, wide flammability range and so on. In order to suppress the burning velocity of H2-O2 premixed flame, we propose an addition of CO2 to the mixture. However, a lean H2-O2-CO2 premixed flame tends to become unstable and form a cellular flame front owing to its intrinsic instability. For control of the combustion, it is necessary to elucidate the instability of lean H2-O2-CO2 premixed flames. In this study, we investigated the structure and behavior of lean H2-O2-CO2 premixed flames on a flat burner by direct photographs, time series analysis of light emission and Rayleigh scattering, and understand the flame instability. As the results, it was observed that the cell width obtained from the direct photographs increased with decreasing of equivalence ratio. To investigate the fluctuation characteristics of the flames, we reconstructed attractors from the light emission intensity of the flames. The attractors had torus shapes which indicate that the flame behaviors are quasi-periodic. In the Rayleigh scattering, we obtained not only width but also depth of the cellular flame. The cell width and depth increased with decreasing of equivalence ratio. Furthermore, the width and depth became larger as the CO2 concentration increases. These results showed that diffusive-thermal effect influenced the cellular structure.
This paper presents a detailed experimental study to understand the fundamental process of jet breakup during a core disruptive accident of a sodium-cooled fast reactor. The study mainly focuses on hydrodynamic interaction of jet breakup and fragmentation behavior. The experiments were carried out in an immiscible liquid-liquid system. The indices of refraction in the two liquids were matched, so that the vertical plane of jet flow was clearly visualized using laser-induced fluorescence (LIF). The jet breakup length obtained by image processing is compared with the existing correlations. The applicability of the jet breakup length correlations is discussed from the viewpoints of Weber number and film-boiling effect. When the Weber number is from 10 to 1000, and the boiling effect is small enough, it is suggested that jet breakup length is described by Epstein's correlation. Finally, the reduction of jet core diameter is investigated. It is shown, in this experiment, that the mean jet diameter reduces in the flow direction gradually, but it does not reduce linearly.
Gyro is not only used as a sensor but also used as an actuator. In the beginning of 20Th century, the gyro monorail using a gyro-actuator which was controlled by manual operation was proposed. In 1970's, the research on a gyro bike was reported. However, a standstill was only confirmed in it. On the other hand, the self-sustaining control of two-wheeled vehicles by using an inertia rotor are reported recently. However, it is difficult to make a large vehicle because this inertia rotor system has only a smaller power as compared with that using the gyro actuator which can obtain a larger power. The modeling is needed for the control system design of the vehicle with a gyro actuator. In this paper, first, positions, angles, and angular velocities are calculated from 3rd link system, then the model for the two-wheeled vehicle with a gyro actuator is made by using Lagrange equation, next the control system is designed by the Ricatti equation, finally the effects of this theory are confirmed by experiments.
We have been developing a standing ride type vehicle, such as electric skateboards. A human dynamics model is required to assist balance control of human standing in the vehicle. So far, however, little information has emerged on the human balance control mechanism. The purpose of this study is to construct a transfer function model of human body dynamics on frontal plane when the support surface moves to horizontal direction. The present investigation deals with the dynamics in low frequency range (below 4rad/s) with parallel stance. We assumed a human mechanical model as one degree-of-freedom system. In a previous paper we estimated characteristic roots of the human standing model from impulse response tests. Here we report a procedure to identify a transfer function model describing the system definitely from the result of impulse response tests and frequency response tests. Reference acceleration for the support surface in the frequency response test was composed of six trigonometric functions from 1.0 rad/s to 4.0 rad/s. Posture angle of the body and moment generated from support surface were measured by a motion capture system and a load measurement system respectively. The human model was identified by two steps in the present method. We estimated the characteristic roots from the result of impulse response test in first step. Then it allowed us to define denominator of the transfer function model as the estimated characteristic polynomial. In second step, we identified numerator of the transfer function model from the result of frequency response test by least square method. The present method enabled us to identify a low-dimensional transfer function model accurately from experimental data with large variability.
Soil behavior generated by a root-cutting blade moving under the ground of an automatic spinach harvester for spinach for eating raw is analyzed in this paper. It is difficult to harvest spinach for eating raw by using automatic harvester because stems and leaves of spinach are soft and easily bruised. Thus the harvester which can be widely used among farmers has not been developed. To overcome the difficulty, we have been developing the automatic spinach harvester which does not bruise spinach. A trajectory of a root-cutting blade is very important to achieve this automatic harvesting without bruising spinach because the motion of cutting the root of spinach is influenced by soil which the blade presses and moves in. In this paper, accordingly, some characteristics in the behavior of soil caused by the moving blade are clarified by using the distinct element method (DEM) to investigate the automatic harvesting. In conclusion two important characteristics, the velocity of the moving blade and the volume of soil in the passage field the blade moved, are pointed out and described.
The effects of friction on the driving mechanism using swing motion are investigated. The system comprises a body and a rod which have two and one freely rotating wheels, respectively. The rod is pinned to the body and can swing like a pendulum about the pinned joint by a servo motor. The system moves forward with or without slipping on the floor depending on the relationship of friction coefficient, swing amplitude and swing period. Effects of the parameters on the moving performance are clarified experimentally and analytically. The results demonstrate that the system is accelerated by the frictional force acting on the rod in the wheel axis direction. In addition, experimental results show that the bias angle of the rod makes turning motion of the system.
In the current automobile industry, the demand for ultra-compact vehicles as a means of transportation within a local area for elderly people, for example, for shopping, has been increasing. The effect of vibration of such vehicles on ride comfort is significant because of their small size and light weight, and it increases the discomfort perceived by persons in the vehicle. Moreover, ultra-compact vehicles frequently travel over alleys and unpaved roads; therefore, the ride comfort of ultra-compact vehicles is expected to deteriorate because of bumps, rough roads, and small obstacles. To solve this problem, we have proposed active seat suspension that can be installed in ultra-compact electric vehicles. Thus far, we have examined the control performance of this system and its practicality in terms of ride comfort, with the aim of reducing the vibration acceleration of the seat surface. To improve the ride comfort of vehicles, in addition to reducing the vibration acceleration of the seat surface, it is also necessary to control the vibration on the basis of the ride comfort perceived by drivers such as to reflect the mood and mental state at the time. Most studies have not focused on the psychological and physiological effects of active seat suspension on the ride comfort of ultra-compact vehicles. In this study, we carried out an outdoor traveling experiment and examined the effect of vertical vibrations on ride comfort by evaluating physiological and psychological information.
Active dynamic vibration absorbers are widely known as vibration control device exhibiting good performance for disturbance signal with various frequencies. Linear quadratic (LQ) control is often used in active dynamic vibration absorbers. We show that nonlinear control laws provide vibration control performance higher than the LQ controller by designing homogeneous control Lyapunov function (CLF) controllers guaranteed convergence rates and high robustness. In this paper, we design homogeneous exponential stabilization controllers based on Riccati solutions of LQ controllers and finite-time stabilization controllers for vibration control device using fixed surface and confirm that designing convergence rates are quite effective for vibration control performance. Moreover, the effectiveness of our controllers is verified by the analysis of transient and steady-state frequency responses for hybrid dynamic vibration absorbers with numerical simulation.
The demands for comfort vehicle are getting increased in these years. On the other hand, the demands for the weight reduction for low fuel consumption are also increasing. In order to achieve these demands, the most efficient way is to reduce the input to the vehicle body. For reducing the input from road surface to the vehicle body, the suspension plays very important roles. So far, many literatures written about reduction of the input by the suspension have been reported. However, there are less papers written about the influence of nonlinear restoring force of the suspension component such as the shock absorber and the suspension bush. Typically, time domain behavior like harshness has large displacement. Therefore, the influence of the nonlinear restoring forces is not negligible. In this paper, the influence of the nonlinear restoring force in time domain is presented. For simplicity, two dimensional model which consists of rigid links connected by the nonlinear springs and elastic beam is used. On the model, the restoring force characteristic of an actual suspension bush is taken into account to set the range of the design space for the nonlinear restoring force of springs. The instantaneous maximum beam energy is maximized and minimized in order to show the influence of the nonlinear restoring force of springs. The maximization and minimization are conducted using local optimization method by the use of the sensitivity with respect to the nonlinear restoring force coefficient. Besides, the mechanism of the change of the instantaneous maximum beam energy is discussed from the point of view of energy flow. Finally, the influence in different input characteristics is investigated by changing the speed passing over a protrusion.
A visual-servo type remotely operated vehicle (ROV) system with binocular wide-angle lens was developed to survey submarine resources, decontaminate radiation from mud in dam lake and so on. This paper explores the experiments on regulator performance and underwater docking of the robot system utilizing Genetic Algorithm (GA) for real-time recognition of the robot's relative position and posture through 3D marker. The visual servoing performances have been verified as follows; (1) The stability performances of the proposed regulator system have been evaluated by exerting abrupt distrubane force while the ROV is controlled by visual servoing. (2) The proposed system can track time-variant desired target position in x-axis (front-back direction of the robot). (3) The underwater docking can be completed by switching visual servoing and docking modes based on the error threshold, and by giving time-varying desired target position and orientation to the controller as a desired pose.
An evaluation technique of internal boundary surface using instantaneous frequency of ultrasonic pulse is proposed. The instantaneous frequency represents a variation of the frequency of the ultrasonic pulse waveform from moment to moment. In this paper, a novel technique to acquire precisely the instantaneous frequency of ultrasonic pulse is proposed. Results of fundamental experiments, in which several internal boundary conditions are simulated by rubber elements, show that the instantaneous frequency of ultrasonic pulse transmitted the internal boundary is sensitive to the change of the boundary condition. Profiles of instantaneous frequency significantly change according to surface roughness and contact pressure of boundary, so that the internal boundary conditions can be evaluated by the instantaneous frequency. It is demonstrated that internal boundary conditions can be modeled as linearly or non-linearly change of partial stiffness, and the profiles of the instantaneous frequency depend on the partial stiffness. In addition, it is shown that the proposed method is not only available to rubber element but also metallic component.
We developed a mesh morphing technique, which can be used to change the shape of existing analytical mesh models, and generated a mesh model for a new shape by morphing the mesh model for the previous one. Therefore, our method is suitable to use for analysis during the early stage of design because it reduces the amount of time required to generate analytical mesh models. However, this technique is impossible to morph a free-form surface, and to change surface type. Accordingly, we developed the fitting morphing technique for solving the problem. This technique is possible to morph based on specification of the STL data as morphed shapes and indication of fitting nodes and movable nodes. We developed a series of techniques that include three distinct features. (1) Geometric feature recognition algorithm based on region growing method. (2) Geometric feature assignment algorithm on the basis of distance and angle of geometric features between original mesh and morphed shapes. (3) Node fitting and moving algorithm by displacement coefficient calculation using Ferguson curve characteristics. We confirmed that this technique can morphed to free-form surface from cylindrical surface by applying to the piston head model. Furthermore, the technique can morphed to maintain the boundary continuity of the shape by applying to the gear model.
In this paper, we propose a robust shape optimization method for a linear elastic structure with unknown loadings. The concept of principal compliance for minimizing the maximal compliance in the unknown loadings is applied to a shape optimization problem of a linear elastic structure. The principal compliance minimization problem is transformed to the equivalent maximization problem of the fundamental eigenvalue, and the problem is formulated as the distributed-parameter shape optimization problem based on the variational method. The derived shape gradient function is applied to the H1 gradient method to determine the optimal shape variation, or the optimal free-form of the linear elastic structure. With this method, the optimal shape can be obtained without shape parameterization, while maintaining the surface smoothness. It is confirmed that the obtained shape has high and uniform stiffness in all directions. We confirm the proposed method is effective for designing the robust shape with high stiffness of a linear elastic structure with unknown loadings.
An optimization technique using the hybrid GA for large structures in which a lot of stiffeners are attached is proposed in this paper. The object function is the mass of structure and the design variables are the number and the position of stiffeners, the shape of stiffener and the thickness of plate. These design variables make a combinational optimization problem for which genetic algorithm is effective. However, this optimization problem includes the position of stiffener and the thickness of plate which are kinds of continuous design variables. A lots of bits are needed for expressing continuous design variables by strings of genetic algorithm in order to have reasonably small increments of them, which results in a large calculation amount. In order to overcome this problem, a hybrid GA is introduced in this paper. Hybrid GA is optimization method which combines GA with another optimization technique which handles continuous design variables. The relation among the thickness of plate, the span of stiffeners attached on the plate, the deflection and the stress of plate are introduced in order to predict suitable design variables in this added optimize technique. The proposed optimization method makes it possible to optimize continuous design variables, the position of stiffeners and the thickness of plate,with small calculation amount. Several selected problems are solved to show the capacity and validity of the proposed method.
Since titanium has a corrosion resistance and biological compatibility, it has recently been used in aeronautics and biomedical fields such as the development of artificial bone, medical tools and equipment. These specific applications often require a mirror-like surface in order to achieve an optimum efficiency and quality. However conventional polishing processes actively oxidize the polished surface and consequently the surface roughness isn't improved because of the presence of several surface oxides. Therefore a new polishing technology process that countermeasure oxidation during polishing of titanium was developed and evaluated. Firstly, new slurry was developed for the countermeasure against oxidation. L-ascorbic acid (also known as vitamin-C) was added to the slurry for the countermeasure against oxidation because it is frequently used as antioxidizing agent. Furthermore, xanthan gum was also added to the slurry as viscosity increasing material that allowed a better diamond grain dispersion in slurry. Here, respective optimum additive amount of L-ascorbic acid and xanthan gum were revealed. And surface roughness of titanium was improved by removing chips every feed by using developed slurry. Moreover, period of antioxidant effect of developed slurry was evaluated. Finally, corrosion resistance regarding titanium in developed slurry was performed. It is concluded from the results that (1) the slurry containing L-ascorbic acid and xanthan gum allowed and oxidation-free polishing, (2) polishing process without deep scratches was carried out by removing chips with sandpaper, (3) surface roughness of titanium was improved up to Rz 0.12 μm by using developed slurry, (4) developed slurry had antioxidant effect period of one week, (5) titanium submerged period of one month in slurry containing L-ascorbic acid and xanthan gum didn't erode.
In recent years, development of the automated driving system is aggressively promoted for the purpose of reducing burden of drivers and for the enhanced safety. Transferring the intention of the driver to the automobile control, such as to stop on the way or to change destinations, is essential even if a direct control from the driver is no longer necessary. Therefore, an in-car interface to conduct intention of the driver promptly and accurately to the automobile control is needed. In this paper, we proposed an interface which recognizes the intended target of the driver using gestures and speech recognition. The speech recognition technology was previously developed. Hence, we developed an interface to recognize the direction in which the driver is pointing toward from the gesture. We hypothesize that we can estimate the direction in which the driver is pointing toward from the fingertip and eye position. Verification using three-dimensional motion analysis system showed that it is possible to recognize the direction of the object with a maximum error of 5.5° and an average error of 1.2°. After verifying the hypothesis, a position measurement device that integrates Leap Motion® and KINECT®, the non-contact sensor, was developed to recognize gestures of the driver in the automobiles. The maximum error of the angle recognition in accordance with the present device was 16.1°. However, the value of the error exists only in a certain interval. For this reason, by taking into account the movement of the eye position, and provide adequate tuning for each driver, proposed interface is sufficiently usable.
This study examines a driver assistance system to predict driving behavior considering information on the pre-preceding vehicle behavior. The authors have defined an anticipation index called PRE3 and proposed a driving assistance system that indicates the PRE3 to the driver in real-time during a car-following. The assistance system indicates the predicted driving evaluation index at the rear-end of the preceding vehicle. The proposed driving assistance system considering the relations not only between the preceding and following vehicles, but also between the pre-preceding and following vehicles. Driving simulator experiments were carried out with eight participants who are required to follow a preceding vehicle and a visible pre-preceding vehicle with and without the driving assistance system. It was found that high acceleration and large speed difference with the preceding vehicle could be eliminated by the proposed system. These effects make it possible to suppress the variation of the collision risk to the preceding vehicle and to reduce fuel consumption of the following vehicle. In addition, the proposed assistance system reduces drivers' reaction time to the emergency deceleration of the preceding vehicle compared with the conventional assistance system, in which PRE3 is indicated at the onboard monitor of the following vehicle. Indicating PRE3 at rear-end of the preceding vehicle helps the driver to decelerate earlier and to avoid the high deceleration.
This paper describes a new cushion using a urethan within an air cell (UA cell). In order to reduce vibrations of occupants, we propose the UA cell enable to control mechanical properties by an air pressure in the vehicle seat. It is necessary to clear mechanical properties of UA cell for the reduction of vibration. The purpose of this paper is to clarify the mechanical properties of the UA cell when the air pressure of the UA cell changes. In this study, the UA cell consisted of a liner polyethylene and the urethan is designed. Relationships between the air pressure and the mechanical properties of UA cell are examined by a measurement using a vibration exciter. From these results, frequency response functions are changed by controlling the air pressure. A spring constant and a viscous damping coefficient are estimated from the frequency response functions. Relationships between the air pressure and mechanical properties are approximated by a 7th‐degree function. In addition, the variation range of the UA cell is wider than that of the air cell in the mechanical properties when the thickness of the UA cell and the air cell are changed within the same range. Therefore, it was shown that the UA cell could be used as an actuator to control the mechanical properties.
This paper proposes a method to simulate the primary bending vibration in a test stand consisting of one-third segment car body and a full-scale bogie of magnetically levitated (maglev) vehicles. The purpose of this system is to evaluate an effect of high-frequency vibration to the ride comfort on maglev vehicles. The system utilizes hardware-in-the-loop simulation (HILS), which incorporates hardware components in the numerical simulation. A vehicle dynamics simulation model in the HILS system calculates internal forces acting from remaining two-thirds segment car body which is missing in reality, and applies constraint forces equivalent to the internal forces to the one-third segment using electric actuators. Fundamental studies on the proposed system were conducted. First, a new mathematical model, which can calculate the internal forces in low dimensions for real-time simulation, is presented. The validity of the model is verified with an eigenvalue analysis. Second, results of swept sine excitation experiments demonstrate that the actuators can perform immediate vibration responses with a new control method. Finally, fundamental experiments were conducted with the mathematical model and the control method to evaluate effects on vibration characteristics of one-third segment car body with exciting shearing force and bending moment at the body end. The results of these studies show the technical prospect of the test stand to evaluate the high-frequency vibration of maglev vehicles.
This paper describes considerations of the effectiveness about the recovery control of the yaw rate motion of single-rotor helicopters by using both motors (engines) and main-rotor brakes in autorotation flight under tail-rotor damage conditions. First, the newly-developed main rotor brake unit for the experimental small helicopter is introduced. Flight test results show the yaw rate controllability by using the proposed brake and motor. Next, the yaw rate control system with a dead-zone estimator/compensator is designed to improve the control performance considering dead zones of input command signals of the brake or the motor. New method of dead-zone estimation when disturbances are applied to helicopters is proposed in this paper. This method is based on the nonlinear extended Kalman filter which enables simultaneous estimantion of dead zones and a yaw moment external disturbance by using a rotational speed of a main rotor in addition to a yaw rate for measurement updates of the estimator, which is designed based on the helicopter motion dynamics model including a clutch and a brake with motor dynamics. Estimation and control performances of the proposed system are validated through several simulation and flight test results.