Argon ion sputter-etching of SUS420J2 and SUS316 stainless steels was carried out at a power of 250W for 10.8ks to form cone-shaped sharp protrusions with bottom diameter of 10-30 μm and fine quasi-column-shaped protrusions with diameter smaller than 500 nm respectively by using a radio-frequency magnetron sputter-apparatus. Effects of two types of plasma-nitriding on gripping ability were examined; one is the nitriding of both steel specimens using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50W for 1.8 ks to maintain the original sharpness of protrusions, and another is the nitriding of SUS420J2 steel specimen using only nitrogen gas of 1.2 Pa at a power of 200 W for 7.2 ks to obtain the cone-shaped protrusions with round top. The coefficient of static friction, or gripping ability, of the plasma nitrided sharp protrusions of SUS420J2 steel specimen to polyethylene, polyvinyl-chloride, polyethylene-naphthalate sheets and a copy paper was about 1.8, 2.4, 1.1 and 1.5, respectively, at a large nominal compressive stress of 18 kPa. The reason for such large frictional coefficients is due to localized deformation of sheet under the sharp protrusions or piercing of the protrusions into the sheet. Although the sharp protrusions were partly broken, the frictional coefficients of these sheets were still about 1.6, 1.8, 1.1 and 1.4 after the second series of tests, which are more than twice as large as that of the specimen ground with #100 emery paper. The plasma-nitrided round protrusions of SUS420J2 steel and the fine protrusions of SUS316 steel were not broken during the friction tests of the polyethylene sheet and the copy paper but the frictional coefficients are smaller than those of the sharp protrusions. The protrusions with large frictional coefficients can be applied to the surface of a frictional conveying roll.
Surface modification of polystyrene (PS) dish used as a cell culture substrate is an indispensable strategy to enhance cell adhesion. In general, plasma treatment is employed to enhance the hydrophilic nature on the PS dish surface, and sterilization treatment of the PS dish is performed after the plasma treatment. We reported on a simultaneous process of surface modification and sterilization on the PS dish in a sterilization bag by using active oxygen species (AOS) generated via ultraviolet (UV) lamps, whose wavelength are 185 and 254 nm respectively. Herein, we attempt to investigate the dependency of the distance between UV lamp and PS dish on the surface modification by using the AOS. After exposure of AOS, the oxygen content of the PS dish was increased, whereas the water contact angle was decreased along with the decrement of the distance between PS dish and UV lamp owing to increase in the AOS concentration. Cell adhesion was also enhanced with decrease of the distance between PS dish and UV lamp compared with untreated PS. Especially, chemical states such as atomic concentration and chemical bonding affect cell adhesion rather than the surface wettability. Illumination of the UV lamps and AOS concentration at the PS dish surface affects the resultant cell adhesion.
In case of analyzing the wind turbine design conditions and power productions accurately, the wind data at hub height is generally ideated for simulation. Recently, due to the increase in the size of the wind turbine, it is difficult to measure wind data of hub height by the cylindrical observation tower. Therefore, lattice tower mast is adopted and there are cases where high altitude measurement is performed instead of cylindrical tower mast. However, even in case of measuring wind data using lattice tower mast, there are some uncertainty of flow distortions by tower shadowing. This paper shows a study on wind speed correction method of lattice tower mast using CFD simulations (Fluent). As a result of performing the wind speed correction using the inflow wind speed ratio by CFD calculation, the uncertainty of corrected wind speed fell by less than 1 % which is recommended by IEC 61400-12-1.
Behaviors of liquid films scattering from a disk-type or cup-type rotary atomizer are studied using computations based on the three-dimensional Smoothed Particle Hydrodynamics (SPH) method. To reduce computational costs while maintaining a high spatial resolution, the computational domain is limited to a fan-shaped region near the edge of the atomizers using a periodic boundary condition in the circumferential direction. Steady inflow is considered as the inlet condition. In both disk- and cup-type cases, the liquid film leaving the atomizer edge becomes wavy in the circumferential direction and forms elongated ligaments, which break up into droplets. When the atomizer is equipped with grooves on its outer edge, the process of ligament formation and droplet break up is strongly affected by the number and shape of the grooves, particularly for the cup-type atomizer, in which the centrifugal force works more effectively. Two ligament formation patterns are observed: one ligament from each groove and a pairing of ligaments from two neighboring grooves. Droplets of uniform sizes are likely to be generated when the former pattern appears. The results suggest that droplets of uniform sizes can be obtained by choosing the appropriate shape and number of grooves.
The conserved scalar and progress variable have been modified and proposed for spray and engine combustion simulation with chemical kinetics. The global equivalence ratio (GER) and progress equivalence ratio (PER) were proposed as the conserved scalar and progress variable in multi-zone model for engine simulations with chemical kinetics (Babajimopoulos et al., 2005). The combination of GER and PER work in lean mixture without EGR gas. But these would not work under rich mixture or EGR gas conditions. Thus, the modified GER is proposed to apply the EGR gas conditions where CO2 and H2O mix in air. Furthermore, the progress variable based on the chemical energy also proposed with modified GER. The zero-dimensional combustion simulations are done under constant pressure and adiabatic conditions to validate the proposed indexes. The reaction mechanism is the detailed chemistry of n-dodecane. That consists of 1,255 chemical species and 3,075 reactions. The results show that the conventional GER works in any mixture as conserved scalar and is good agreement with equivalence ratio under the ambient gas of air. But, the conventional GER overestimates equivalence ratio in lean mixture and underestimates equivalence ratio in rich mixtures. The modified GER is good agreement with equivalence ratio under the ambient gas of air and EGR gas including CO2 and H2O, regardless of lean and rich mixtures. The results also indicate that the PER works in lean mixtures. But that do not work in stoichiometric and rich mixture. The progress variable based on the mass fraction of some chemical species (Van Oijen and De Goey, 2010) works in any mixture, but the that can not compare the reaction progress between different GER conditions. The proposed progress variable works in any mixture and compares the reaction progress at different GER conditions quantitatively.
For the development of industrial heat pump system supplying a high-temperature heat source, the application of chevron type plate heat exchanger is being considered. In the present study, experiments and numerical simulation on flow characteristics in single chevron channel with chevron angle 30°, 45° and 65° were respectively performed. In the experiment, the pressure drop of the whole chevron channel and local pressure drops in each chevron channel were measured and path lines were also observed. Besides, numerical simulation reproduced the experimental results well. From both of the experimental and simulation results, it was confirmed that the pressure drop of the chevron channel became larger with increasing the chevron angle due to the strong mixing of fluids in the respective furrows of adjacent chevron plates especially in the high chevron angle channel. In such the high chevron angle channel, velocity and pressure drop gradient distributions were almost uniform in the channel width direction normal to main flow. While, in the small chevron angle channel, the fluids mixing between furrows of adjacent plates was weak and the velocity and pressure drop gradient distributions were markedly large in the width direction. Furthermore, it was found that large pressure drops occurred in the inlet and outlet regions where the channel had flow width expansion and contraction, respectively. The large pressure drops in the inlet and outlet regions affected the overall pressure drop in the chevron channel, especially in the low chevron angle channel. For each chevron angle channel, the local friction factor was obtained and the loss coefficient for the flow expansion and contraction at inlet and outlet regions was determined. Based on these results, the prediction method of overall pressure drop in the chevron channel was proposed.
The field of multi-robot systems (MRSs), which deals with groups of autonomous robots, is recently attracting much research interest from robotics. MRSs are expected to achieve their tasks that are difficult to be accomplished by an individual robot. In MRSs, reinforcement learning (RL) is one of promising approaches for distributed control of each robot. RL allows participating robots to learn mapping from their states to their actions by rewards or payoffs obtained through interacting with their environment. Theoretically, the environment of MRSs is non-stationary, and therefore rewards or payoffs learning robots receive depend not only on their own actions but also on the action of other robots. From this point of view, an RL method which segments state and action spaces simultaneously and autonomously to extend the adaptability to dynamic environment, named Bayesian-discrimination-function-based Reinforcement Learning (BRL) has been proposed. In order to improve the learning performance of BRL, this paper proposes a technique of selecting either of two state spaces: one is parametric model useful for exploration and the other is non-parametric model for exploitation. The proposed technique is evaluated through computer simulations of a cooperative carrying task with six autonomous mobile robots.
The ductility factors of nonlinear SDOF systems at Service Limits Ds “using elastic analysis design” in JEAC4601 are investigated, and it was confirmed that the ductility factors depend on the natural frequencies of systems, seismic motions and constant loads. Based on the above results, an acceptance criterion of components to prevent ductile failure and plastic collapse is proposed. The criterion is given as a limit of ductility factor for Service Limits Ds “using elastoplastic analysis design”. The proposed limit of ductility factor allows single state for nonlinear systems, and doesn't depend on the natural frequencies of systems, seismic motions and constant loads.
Power assist devices are worn by users, directly transmit actuator power to the users’ bodies, and can deliver assistance in activities of daily living, such as load lifting. In this study, we built a wearable power assist device for lower limbs driven by pneumatic actuators. Pneumatic power assist devices are safe for users, owing to the compressibility of air; however, the weight of the devices and assist torque often have a negative effect on the wearer’s body balance. Here, an assist control strategy is proposed for the pneumatic power assist device. In this strategy, the relationship between the lower-limb joint angles and the center-of-gravity (COG) of a human body is represented based on a simplified human body model during squatting. Assuming that the anterior and posterior movement of the COG follows the knee joint flexion and extension, the desired COG position is calculated from the knee joint angle measured with a sensor. The desired hip and ankle joint angles are found with the desired COG position, and the desired assist torque is obtained with these joint angles based on the human body model. The power assist device based on this principle was worn by research subjects, and its assistive performance was evaluated through experiments from the viewpoint of the COG fluctuation and muscle activity reduction.
CVT chains have become widely used in vehicles because the slip between parts is very small, which enables efficient power transmission. However, the motion caused by the pins of the CVT chain entering and leaving the pulleys one after another during the power transmission process results in periodic motion of the whole chain. This behavior is known to affect noise and other basic performance aspects of CVTs. Therefore, it is important to study the geometrical specifications of the chain that affect periodic motion, such as the shape and dimensions of the parts. This study aimed to (1) identify the periodic motion that affects noise, and (2) formulate a motional theory to derive the ideal specifications of a CVT chain. First, after measuring the acceleration of the pulleys under conditions that generate large CVT noise, it was found that noise was greatly affected by periodic motion caused by the chordal action of the chain. Based on this result, a mathematical model was proposed to describe this chordal action. The pin profile curve was particularly considered in the model since it determines the motion of the chain at both ends of the chord part and has an important effect on the chordal action. Next, the chordal action of the chain was measured using an accelerometer, and the measured results were compared with the results calculated by the model. The results were consistent, which confirmed the validity of the model.
In recent years, an automatic collision avoidance system has been put into practical use by various automotive companies. In this study, we propose an automatic collision avoidance system for a four-wheel independent drive vehicle using the state-dependent Riccati equation. By designing the state-dependent weighting functions, a control gain is automatically determined, based on the relative relationship with a preceding vehicle and the system can properly perform automatic braking and automatic steering. Moreover, by updating the state-dependent linear representation obtained from a nonlinear vehicle model in each control cycle, we design a control system in consideration of a change in vehicle dynamics due to vehicle velocity. Therefore, this study verifies the effectiveness of the automatic collision avoidance system using the state-dependent Riccati equation. We compare the performance of the proposed method with constant weight cases. The simulation results show that the proposed method can automatically adjust the control gain and properly avoid a collision by braking and steering to change the relative relationship with a preceding vehicle.
In this study, vibration characteristics of a single-degree-of-freedom linear oscillator with the fractional order derivative are examined in terms of the critical damping over a wide range of the order of the fractional derivative by using numerical analysis. Two types of the definitions of the critical damping used in the previous studies are considered. It is shown that (i) the critical viscoelastic damping ratio changes according to the order of the fractional derivative and its minimum value for both types of the critical damping is less than 1; (ii) no critical viscoelastic damping ratio is observed in a certain range of the order; (iii) the difference in the existence of the critical damping between the oscillators with the derivative of order 1/3 and 2/3 is caused by the change of the behavior of a component of the response corresponding to one of the roots of the characteristic polynomial for the oscillator. Finally, the impulse response characteristics are classified into three classes depending on the order of the fractional derivative and viscoelastic damping ratio of the oscillator.
In household refrigerators, the rotational speed of a reciprocating compressor can be appropriately adjusted according to the temperature inside of the refrigerator. The lower rotational speed reduces the power consumption of the compressor. However, several natural frequencies of the compressor exist in the low rotation region, and besides, the unbalance force arising from the piston motion acts on the internal drive unit. Thereby the vibrations of the compressor are likely to be larger due to the resonance in the low rotation region. In this study, a method for supporting the drive unit inside the shell, which is called “the self-standing support” is newly proposed in order to reduce the vibration of the compressor drastically. In the proposed method, a spherical support element is utilized instead of coil springs to support the drive unit. And the drive unit can maintain a stable self-standing state by acting restoring moment due to the gravity while it is directly placed on the shell. The natural frequencies of the compressor can be greatly reduced by decreasing the support stiffness for the drive unit in comparison with the support method using coil springs. Furthermore, in designing the drive unit, the application point of the exciting force is matched with the center of percussion to the contact point on the spherical support. As a consequence, the periodic restraining force acting on the contact point can be minimized. By these two features, it is possible to considerably reduce the vibration transmission from the drive unit to the shell. In the present study, a simplified model for a reciprocating compressor is treated, and the effectiveness of the self-standing support is investigated analytically and experimentally.
A semi-active vibration control technique using piezoelectric actuators with switched inductance shunts has been studied. This technique can be used for not only vibration suppression but also energy harvesting. In order to design semi-active vibration control systems and energy harvesters using this technique efficiently, it is necessary to analyze and understand the effects of design parameters on the performance of these systems. Responses of these systems to harmonic disturbance forces can be used for performance evaluation and previous studies analyze periodic responses of semi-active vibration control systems by assuming sinusoidal displacement responses and using method of harmonic balance. However, this control technique induces rectangular control forces and the displacement responses are distorted. Enhancing the control forces leads to stronger distortion of the responses and the validity of the assumption of the previous studies becomes lost. In order to overcome this problem, the authors have proposed to use shooting method which is a numerical method to calculate periodic solutions of non-linear systems without assuming certain forms of responses. This paper presents periodic responses obtained by shooting method with an improved non-dimensional model and the periodic responses are compared with ones obtained by method of harmonic balance. Furthermore, this paper considers not only the periodic responses but also non-periodic chaotic responses obtained by long term simulations with the non-dimensional model.
This study aims to realize fast disturbance estimation with a Kalman filter (KF). This paper presents a methodology of fast estimation and rejection for some types disturbances. This methodology attempts to estimate the state of mechatronics systems that rejected the influences of disturbance and noise by using KF. Most of known disturbance estimation method is the disturbance observer (DOB). However, the conventional DOB can not estimate the disturbance that is contaminated of noises. Generally, KF is known as state estimation algorithm that can consider influences of various noise. In addition, we had done some previous studies to design a linear KF with disturbance estimation. We obtained a fact that the disturbance estimation speed by the KF is slow from these studies results. Therefore, this paper proposes a new design method of KF with disturbance estimation which includes a design parameter to speed up disturbance estimation, where we have never concerned in this paper with KF design method except linear systems. Finally, we show the design method on the proposed method and usefulness via the simulation results relative to the position control for an simple cart system.
A motor shaft direct drive is known as a simple and low cost scheme for small toy vehicles, however the mechanism how it produces propelling force has not yet been explained nor discussed in detail. A trivial idea that a small dent is formed on the road surface just under the shaft end due to static weight takes us to the unexpected result. Brief calculus reveals that the propelling force vector of the system directs somewhat forward with respect to sagittal plane which includes motor shaft slant axis. It suggests that the motor alternative cw and/or ccw rotation generates gradual forward movement, i.e. the vehicle moves perpendicular direction with respect to that of right-left swinging motion. The forward motion is confirmed experimentally with single motor shaft direct drive vehicle, and also discussed in details.
In the field of precision positioning such as semiconductor exposure apparatus, weak disturbance vibration from the floor influences processing accuracy. In recent years, as the precision of the device increases, the vibration allowance value becomes more severe, and performance improvement of the vibration isolator is required. In order to improve the performance, there are researchs reducing natural frequency by the frequency characteristics of the vibration transmissibility from the floor to the vibration isolator. Reducing natural frequency and decreasing stiffness are equivalent, and main target was stiffness generated by compressed air of air spring. In addition, rubber bellows of air spring is also targeted for further performance improvement. We already proposed a method combining the two stiffness separately decreasing method. However, decreasing stiffness simultaneously destabilized the device, then it could not be completely decreased. In this paper, as a new stabilization method, stiffness is completely decreased only in the operation frequency band. Since the low frequency has positive rigidity, the localization is maintained. We demonstrated the reducing natural frequency by the experimental result. When stiffness was completely decreased, the servo stiffness which had not been focused in the past became dominant in determining the natural frequency. Therefore, an appropriate design of the servo stiffness is required for further reducing natural frequency. To satisfy this requirement, we calculated the relationship between natural frequency and servo stiffness and gave an index for appropriate design.
In this paper, it is confirmed that natural frequency of isolated table is operated and that degeneration, which means that some natural frequencies have the same value, has a bad influence. Pneumatic anti vibration apparatuses (AVAs) support that loaded devices, i.e., XY stages, operate accurately. However, many strict design conditions are imposed on AVAs with six degrees-of-freedom (DOF) which are used on manufacturing floor. There is a risk that the natural frequency of each motion mode approaches, in other words, that isolated table falls into degeneration. This disturbs accurate operations of XY stages. In this paper, AVA with two DOF is used to simplify motion instead of six DOF. First, it is stated that mode control is used to pressure control. Next, position differential feedback (PFB) is proposed. PFB, which is used to the natural frequency control, is applied for each mode. This means that air spring stiffness is considered as each motion mode, and these are deleted or given. It is shown that the natural frequency of each mode can be controlled individually, by calculation, simulation, and experiment. Finally, the degeneration is reproduced to AVA with two DOF by PFB. At this moment, acceleration control which effects to nearby the natural frequency interferes with each other mode. From these results, conclusions are the following: degeneration should be avoided, and mode PFB is effective to control natural frequency of each motion mode. In addition, mode PFB accomplishes not only avoiding degeneration, but also lowering the natural frequency.
One of effective ways to suppress vibration of a mechanical system is using a dynamic vibration absorber. The dynamic vibration absorber consists of a mass, a spring and a damper. The optimal tuning of natural frequency and damping ratio of the dynamic vibration absorber is required to suppress vibration, so adding an adjustable mechanism of stiffness and damping of the dynamic vibration absorber makes tuning easy. This paper proposes a new design concept of an adjustable dynamic vibration absorber consisted of an adjustable mechanism of stiffness and damping. The adjustable mechanism of stiffness consists of an arm, a couple of coil springs and a rotatable spring holder. Stiffness is varied by rotating the spring holder. The adjustable mechanism of stiffness can expand the range of stiffness by increasing spring constant of a couple of coil springs. The adjustable mechanism of damping consisted of a copper plate, a couple of magnets and a linkage mechanism. Damping is varied by driving the linkage. Driving the linkage to tune damping is necessary large torque because of attractive force of magnets. A compensation spring attached to the linkage can reduce the driving torque for tuning the damping. We made the proposed adjustable dynamic vibration absorber and verified whether the proposed adjustable mechanism is valid by experiments.
In order to clarify the mechanism of the vehicle body hysteresis affecting “rigidity feeling”, one of the driver's sensory evaluation in the driving test, the influence of friction acting on spot welding flanges on hysteresis, which is drawn by the displacement-load diagram of double-hat-shaped parts assembled by spot welding under static or relatively slow deformation, is experimentally and numerically evaluated. The hysteresis of two specimens, one has the contact around R-tangent of flanges and the other has it around edge, are compared and it is confirmed that the former type has larger hysteresis than the latter. The hysteresis is evaluated by the friction loss which is energy dissipation generated only by friction on the surfaces of the spot welding flanges. The loss calculated by the finite-element-method (FEM) with the contact and friction between two flange surfaces opposing each other has good agreement with that measured by the experiment. Additionally, by studying the detail of the relative slip and friction force distribution on the surface of two flanges obtained by the FEM analyses, the difference in hysteresis of two specimens and the cause of the friction loss are discussed.
Pneumatic artificial muscles have many advantages. They have high force mass ratio, high compliance and simple structures. Especially, the flexibility contributes to compose novel mechanisms. The flexibility of pneumatic artificial muscles releases us from the spatially strict design required for rigid mechanical elements: it could actualize compact mechanisms made of a fewer parts. Our research group developed a thin McKibben actuator. The thin McKibben actuators is more flexible than conventional McKibben actuators. Authors succeeded in manufacturing novel soft mechanisms that are made of only braided artificial muscles. We aim to establish a design method for these novel mechanisms. We already have fabricated a cylindrical mechanism made of helical muscles. In this paper, we report a geometric model for the cylindrical mechanism. We focus on only deformation of a side surface in the coordinate system of muscles to simulate the movements of the cylindrical mechanism. The movement was verified by an experiment, and besides, it was simulated successfully in the geometric model that was created. The deformation of height and radius directions changed according to muscles alignment.
Numerical simulations, such as the finite element method have been widely used to predict noise and vibration behavior. This allows reducing the development time and production cost of products. However, these results have been calculated based on the governing equations at each physical areas as the idealized conditions. Then, these simulations are not taken into account the fluctuation of response characteristic by the uncertainties of noise factors. Therefore, it is important to restrain the fluctuation of products properties by the uncertainties. In this paper, focusing on the transient analysis, we propose a robust design for minimizing the time history amplitude fluctuation by structure uncertainties. The robust design is implemented based on the combined use of the stochastic finite element method and the structural optimization. Since this method is performed by minimizing the 1st sensitivity, we will formulate the 1st and 2nd sensitivity in the time domain. Then, the proposed method is validated by applying it to the simple mass-damper-spring system whether the fluctuation of the time history response amplitude is restrained.
SU8 is a negative photoresist shows superior characteristics of heat resistance and chemical resistance. And, it is used to make high-aspect ratio micro structures such as master of electroforming. However, it is extremely difficult to remove SU8 from substrate. Researchers have investigated a means of SU8 removal. Therefore we proposed a new SU8 removal method “DI water (H2O) and lithium chloride (LiCl) doped NMP” which promises swelling furtherance of SU8, and we demonstrated that the new method could remove fine SU8 patters from substrate at proper level. The mechanism of SU8 fine patterns removal is presented as follows. A doped NMP broadens the width of SU8 patterns by swelling effect and reduces buckling stress of SU8 patterns. SU8 patterns reducing buckling stress increases the potential of buckling.
The Design of Experiments (DOE) is a method that is widely used due to its effectiveness to select optimum conditions in the design stage of product development. On the other hand, a fast, low cost, labor saving and energy-saving innovative development is also required in industry. In this research, a program for quickly searching the optimum condition using design of experiments is developed and evaluated. Relationships between each parameter and the final property are firstly cleared for each formula by using the design of experiments. Then the optimum conditions for each parameter were decided by using these formulas in a program. The optimum final property with each optimum level value were calculated. In addition, the optimum condition for cooling system using alkaline water mist was investigated for evaluating this program in an experiment. It is concluded from the result that (1) the program using the design of experiments was useful for fast development process, (2) this program could quickly and accurately decide the optimum cooling condition for cooling system using alkaline water mist.
Joining of plastics and light metals contributes to the reduction of a product weight. In this study, the punching rivet method was applied to joining of an acrylic resin sheet and an aluminum alloy sheet. The punching rivet method can join the sheets without drilling. The riveting process of this method is constituted of the punching process of the sheets using the rivet shank and the fastening process of the sheets using the rivet and the rivet holder. The sheets are fastened by using the plastic deformation of the rivet shank. From the observation of the joints made by the punching rivet method, it was found that the acrylic resin sheet of the joint had no crack and out-of-plane deformation of the joint was small. From the results of the joint strength tests, it was considered that the joint made by the punching rivet method had high strength due to the effect of the pressures on seating faces of the rivet and the rivet holder. As a result, the punching rivet method was effective to join the acrylic resin sheet and the aluminum alloy sheet.
Current production systems are required to stay up-to-date with the changing market conditions. To date, most conventional flexible systems are dependent on human flexibility. However, the demand for flexible automation systems is increasing because of rising labor costs and higher quality requirements, even in emerging countries. To implement automation systems in the unpredictable market, cost reduction is essential to reduce the investment risk. However, there is no systematic design method for reducing the cost of automation systems. Thus, in this study, we propose a new method for the design of material handling systems, wherein the waiting time of the equipment is reduced by grouping the operations and allocating certain equipment to each group. The proposed design method uses a genetic algorithm to determine the optimal grouping of operations on the basis of the equipment cost and cycle time. The design method is then applied to an automobile engine control unit to verify its effectiveness.
Elastohydrodynamic lubrication of a journal bearing has been usually calculated with bearing deformation. In this study, crank-pin deformation is included in addition to the bearing deformation of con-rod big-end. The calculated results are shown with and without the crank-pin deformation and the effects of the crank-pin deformation on calculated results are discussed. The effects of the crank-pin deformation appear after compression TDC during low speed operation and near suction TDC during high speed operation.
The neck is an important body part that links the head and chest sections. However, very few analyses of cervical movement derived from muscle contractions have been conducted with numerical simulation. This study aimed to construct a multi-body model of the neck comprising the bones, muscles, and ligaments (including the intervertebral disc) and to apply flexion and extension movements to analyze the behavior of each cervical segment. We created bone models (including cervical vertebrae C1-C7) from X-ray computed tomography (CT) images of the upper half of the human body. Each bone model was bound by 17 types of ligaments constructed as 51 wire models. We set six types of muscles as the protagonists for neck flexion and 12 types for the neck extension. Muscle strength was defined with a parallel contraction element model and an elastic element model. The intervertebral discs represented five spring models with repulsion characteristics on compression and attraction characteristics on extension. The neck section could flex up to 38.1° and extend up to 61.0° with contraction in the flexor and extensor models. The maximum cervical segment angles on flexion and extension were measured at C0-C1 and C4-C5, and their contribution rates were 20.7% and 19.3%, respectively. Each cervical segment angle when flexing and extending closely matched the experimental results measured by other studies. The centers of rotation for cervical segments from C2-C3 to C4-C5 on maximum flexion were different from those in previous experimental result. This may be because of the settings pertaining to the interspinous ligament, nuchal ligament and supraspinous ligament. On the other hand, our results for maximum extension were consistent with past experimental result. An improved neck model will allow the analysis of cervical segment movement through the joint restrictions based on damage to the ligaments and muscles or arthrodesis when flexing and extending.
Railway vehicles are equipped with many kinds of machines such as traction diesel engines and their failures sometimes lead to service disruptions and accidents. Vibration monitoring systems are expected to prevent their failures by detecting their abnormalities at an early stage. In order to make an effectual action after abnormal vibration detection, it is necessary to make a root cause diagnosis. To address this issue, a simple diagnosis method is proposed in this paper. In the method, a measured vibration octave spectrum is divided into three frequency bands and abnormality detections are conducted for the spectra to narrow down the root cause of the vibration. A one class classification method, which is an anomaly detection method in machine learning, is used in the abnormal vibration detection to make a general purpose vibration monitoring system. In addition, the ratios of abnormal vibration are calculated for the three frequency bands to show the progress of the fault. The effectiveness of the method is verified using vibration data acquired on simulated abnormality tests of traction diesel engines, i.e., auxiliary drive shaft failure test and engine abrasion test. The test results show that the proposed method is effective in detecting the abnormality and diagnosing the cause and the degree of the failure.
In order to achieve advanced missions, it is necessary to develop satellite with large aperture reflectors. Tension truss structure is effective for reducing the weight of the antenna. However, the total strain energy of the cables increases with the number of cables. Consequently, a support structure must be sufficiently rigid to prevent deformation of the surface. The reduction of the reflector's weight can be achieved if the tensile force of the cables decreases, while maintaining the required surface accuracy. Therefore, a surface design method in which compression members are located on the cable network instead of tension cables had been proposed. It was found that cable tension can be decreased within the required surface accuracy based on an analytical estimation. However, the cable tension can be changed after an adjustment of the surface accuracy to eliminate manufacturing and assembling errors. In this study, we evaluate the effectiveness of the proposed method based on an experiment including an adjustment of the surface accuracy. We measure the surface accuracy and reaction force from a support structure using assembled cable-network models. As a result, the total cable strain energy of the cable network with compression members can be decreased by half of that without compression members.
A new method of driving and controlling multiple piezoelectric actuators individually with a single power supply unit using variable resistors was developed, and its effectiveness was investigated. This method provides effective high-accuracy shape control under weight limitation as each actuator can have a desired voltage applied individually from the single power supply unit using variable resistors. It was observed that the proposed method can drive piezoelectric actuators without degrading their operational performance when compared to representative actuator driving methods. Moreover, a shape control utilizing the proposed method was demonstrated to be more accurate than the conventional grouping method of multiple piezoelectric actuators, by numerical analysis and experiments on cantilever beams.