As a simple and highly accurate axial force management method during manufacturing and maintenance of bolt-tightened structures, we examined a method to calculate the axial force from images of the bolt head. In this method, the axial force is calculated using the strain on the bolt head measured by digital image correlation (DIC) technique from images of the bolt head and the relationship between strain on the bolt head and axial force calculated by finite element analysis (FEA). We examined this method through two comparisons. The first was to compare the strain on the bolt head measured by the DIC method with the strain measured by strain gauges. The second was to compare the axial force calculated by this method with the axial force obtained from strain gauges on the bolt neck. The strain measured using the DIC method on M10 bolts had a mean absolute error of 15 μstrain compared to the strain measured by strain gauges. We confirmed that the DIC method can be used to measure the strain on the bolt head generated by bolt tightening with a high degree of accuracy. In all tightening tests in which M10 bolts were applied to axial forces of 16 kN, close to the proof load of 18 kN in strength category 4.8, the tightening coefficient was 1.11 based on the axial force calculated using this method. The coefficient of tightening was also 1.33 when considering geometric tolerances and variations in the coefficient of friction. We confirmed that the axial force management method based on the axial force calculation method using images of bolt heads can be used to manage axial forces with the same or higher accuracy than the conventional general torque management method with a tightening coefficient of 1.4 to 3.0.

The visualization system of soil fluidity in the chamber of EPB (Earth Pressure Balanced) shield has been developed to maintain appropriate fluidity of the excavated soil in real time during the shield advance under the tunnel construction. For further improvement of the visualization system, agitation tests of fluid soil admixed with foam have been carried out to study the relationship between number of rotations and agitating torque of the fluid soil. It is confirmed by the tests that the agitating torque of the fluid sand admixed with the foam reduces with increasing the number of rotations in the range of small number of rotations, and the agitating torque slightly increases in the range of large number of rotations. The phenomena appeared strongly as the volume percentage of foam addition decreased. On the other hand, in case of small weight percentage of fine friction in the fluid soil, the agitating torque reduced with increasing the number of rotations, the torque, however, increased with increasing the number of rotations as the percentage of fine friction increased. It is considered that the relationship between number of rotations and agitating torque of the fluid soil are affected by the friction of sand particles and fluidization due to foam addition and fine fraction in the fluid soil.

The present paper describes the flow characteristics of multiple round air jets with square arrangement at a relatively low-Reynolds number (Re = 4.1×10³). The diameter of a round nozzle was d = 6 mm. To investigate the influence of number of nozzles on the flow characteristics, the number of nozzles was varied 4×4, 6×6 and 8×8 with the nozzle spacing ratio of l/d = 3 where l was the nozzle spacing. To investigate the influence of nozzle spacing, the nozzle spacing ratio l/d was varied from 1.5 to 5 for the multiple round jets with the number of nozzles of 6×6. The mean and fluctuating velocities were measured using constant-temperature anemometer with the normal and reflected image layout cross-wire probes. In case of 6×6 and 8×8 square matrix nozzles, the shape of round jets which were located at the side of the ambient fluid were stretched into elliptical shape by the secondary flow caused by entrainment of the multiple round jets. The combined point of the multiple round jets issuing from square nozzle arrangement was x/d ≈ 16 without relation to the number of nozzles. At the downstream, the flow field of multiple round jets with square matrix arrangement has similarity for the dimensionless parameters of y/D_e, u/U_b, and u'_rms /U_b, without relation to the nozzle number. The multiple round jets with 6×6 matrix arrangement merged easily when the nozzle spacing ratio became small. Thus, the centreline velocity of the combined flow formed by the confluence of the multiple round jets increased with decreasing the spacing ratio. At x/l ≥ 12, the multiple round jets developed as a single jet, and the flow field has similarity for the dimensionless parameters of y/l, u/U_b, and u'_rms /U_b without relation to the nozzle spacing ratio.

The purpose of this study is to propose a method for deriving a structure that uniquely determines the elastic energy stored in the linear spring used in Mechanical Gravity Canceller (MGC) considering the value of the gravitational potential to be compensated. The conventional multi-DOF MGC has a structure in which each link is compensated individually, and when the gravitational potential to be compensated changes, the elastic energy stored in the multiple linear springs have to be adjusted. Therefore, there is a practical difficulty in adjusting the elastic energy when the multi-DOF MGC is applied to load compensation. In order to solve this problem, an articulated compensation method is discussed, focussing on the total amount of elastic energy required for compensation depends on the gravitational potential of the compensation target. In this method, the elastic energy required for compensation is stored in one linear spring and the appropriate amount of the energy is transferred to each link. First, MGC is tried describing from the view of potential energy. Then, the constraint conditions are derived when there is only one linear spring used for gravity compensation, and Triangular Displacement Adjuster (TDA) is designed as an example of the mechanism to satisfy these conditions. Finally, gravity compensation is successfully realized by the proposed elastic energy aggregation and distribution method using a 2-DOF experiment machine equipped with TDA. From the above, it is achieved that the method in which the elastic energy stored in the linear spring can be uniquely determined in response to changes in the gravitational potential which should be compensated.

In this paper, we propose a control system design method for a human-machine cooperative system in which a human and machine cooperate to propel a cart to a reference trajectory. In the previously proposed method, the human plays the role of recognizing the environment and determining the propulsive force, while the machine determines the steering angle based on the position and posture of the cart, using a vector field with the reference trajectory as the orbit attractor. However, since this method cannot avoid obstacles on the trajectory, we extend it to a region attractor. By setting an index variable that changes depending on human input, the vector field is designed in the extended dimensional space including the index variable, and the cart can avoid obstacles by moving within the region defined by the reference trajectory with its parallel trajectory depending on human input. In this paper, we describe (1) the design method of the reference trajectory and the parallel trajectory considering the workspace of the steering and the distance between the cart and the wall, (2) the design method of the region attractor in the extended dimension including the index variable, and (3) the experimental verification of the proposed method.

The wheel of the railway runs while coming into contact on a rail. Therefore, wear occurs in both. When these wears progress, the vibration is amplified. It leads to various problems such as a ride comfort and a noise. Many researchers examined the contact of a wheel and the rail so far. However, as for the shape of the abrasion to be formed on the surface of a wheel and the rail by progress of the abrasion, it is difficult to observe the abrasion situation to change each moment. It is necessary to investigate the process of shape change on wheel and rail in order to examine the influence of wear progress. In this study, we focused on a Discrete Element Method (DEM) that was effective for the dynamic behavior analysis of the granular material. The rail was expressed by replacing the irregularities of the rail surface to particles. A wheel ran on the particles replaced as a rail. Possibility of DEM was examined by comparing the calculated results with the experimental results of repetitive running. As a result, both showed that the acceleration level of the wheel increase and decrease repeatedly. In addition, it was found that the suggested analytical method of this study might be obtained the results similar to the tendency by the experiment.

The number of vehicles equipped with adaptive cruise control (ACC) is increasing, reflecting a trend toward autonomous vehicle development. It is expected that ACC systems will improve traffic in terms of string stability (i.e., attenuation of spacing errors along a vehicle string). For a group of vehicles without string stability, fluctuation in inter-vehicle distance is amplified as it propagates rearward, which may cause traffic congestion. It will take a few decades to replace all human-driven vehicles with autonomous vehicles. Communication technology such as fifth-generation mobile communication systems enables vehicle-to-vehicle communication with a sufficiently small delay. This paper proposes a method for avoiding traffic congestion based on distributed autonomous control. In the proposed method, autonomously controlled vehicles that satisfy string stability are distributed with adequate spacing to constrain the fluctuation of the distance between human-driven and standard ACC vehicles. The conditions for the string stability of distributed autonomously controlled vehicles are derived. The validity of the proposed method is demonstrated using numerical simulations.

Existing manufacturing systems based on processes involving the transportation of workpiece are not suitable for large products such as air mobility. We have previously proposed a novel manufacturing system, “Modularized-Structure and Multiple-points Simultaneous Machining System (MS-cubic)” , which is based on the concept of intelligent space, to realize ultra-complex manufacturing that performs multiple types of machining simultaneously without transporting a workpiece. By modularizing its structure, the system can process multiple points simultaneously and change its work space flexibily. In this paper, we discuss requirements and constraints to lead to a feasible design of the rail module and the machining unit, two main elements of MS-cubic. The performance of the prototype MS-cubic has been evaluated and its concept has been proved.

The simultaneously iterative procedure proposed by the authors is extended to hyperelastic shells. The weak form of the equilibrium equation and the plane stress condition at every material point are defined as a coupled problem, and a numerical procedure based on the block Newton method to solve them with simultaneous linearization is developed in this paper. In the proposed block Newton method, the tangent moduli can be constructed algebraically by eliminating the internal variables, which are also updated algebraically without any local iterative calculations. In addition, the pseudo-stress for the residuals of plane stress state is incorporated into the linearized weak form of the equilibrium equation. Hence, the proposed procedure enables us to decrease the residuals in the coupled boundary value problems simultaneously. Some numerical examples demonstrate the validity and the effectiveness of the procedures in hyperelastic shells.

Various factors in hobbing processes affect profile and helix deviations of hobbed gears, which prevent problems on the hobbing machine from being analyzed using them. Identifying problems requires a system that allows itself to evaluate motion errors in a hobbing machine from them. The proposed one in this study has artificial intelligence for image analysis. Thus, the developed hobbing simulation provided the data on profile and helix deviations of hobbed gears derived from the motion errors in the hobbing process, which determined correlation coefficients to express the similarities of the simulated micro-geometries between tooth flanks of a hobbed gear. These correlation coefficients are color-coded according to their magnitude and converted into images to constitute training data for artificial intelligence. However, different motion errors could lead to similar ones in tests with helical gears. The present paper describes the comparisons between images obtained for spur and helical gears computed by hobbing simulation and the comparisons between ones produced from the simulated and actual micro-geometries. As a result, the motion error that causes similar images depends on gear geometries, i.e., whether spur or helical. Furthermore, actual micro-geometries depend on hob accuracies, which require their compensation. That yields equivalent images to those produced from simulated data.

Conventionally, repeated experiments by trial and error have been used to improve the printing quality of continuous-type inkjet printers. This is because the trajectories of the ink droplets are affected by external forces such as air drag and Coulomb force and thus their analysis is difficult. In this study, a simulation technique to predict the trajectories of ink droplets, the Kriging model, and a multi-objective genetic algorithm were combined to develop an optimization system which determines a droplet charging pattern with better printing results. To enable parallel evaluation of the printing results with an arbitrary charging pattern, the simulation technique was developed based on OpenFOAM, which is an open-source software for computational fluid dynamics. A multi-objective optimization problem was defined by design variables which control the ink droplet charging pattern and by two objective functions which quantitatively evaluate printing quality from simulation results. The Kriging model was used to calculate the expected improvement of the two objective functions and to maximize this improvement by the multi-objective genetic algorithm (MOGA). The developed optimization system was applied to the digit “9” expressed by a 5×5 dot matrix. As a result, the expected improvement-based (EI-based) Bayesian optimization could find the solution which dominates most of the solutions obtained by the MOGA. Additionally, reaching this solution required only 1/7 of the number of simulations required by the MOGA optimization. The obtained solution was used for an experiment on an actual continuous-type inkjet printer and the quality of the printing results was evaluated. It was confirmed that the printing quality provided by the solution obtained by EI-based Bayesian optimization was sufficiently high, and the usefulness of the developed optimization system was demonstrated.

A research project was conducted to develop a grinding tool made of nano-polycrystalline diamond adaptable to fabricating a microdimple array (MDA) mold composed of a huge number of microdimples with a diameter of 30 μm, zero flattening, and a surface roughness of less than 10 nmRz on a surface of cemented carbide with a hardness of 2620 Hv. Eight spiral grooves twisted clockwise and counterclockwise and 7 μm in width and depth were formed on a hemispherical working surface with a radius of 0.1 mm to increase the ratio of actual depth of cut (ADC) that represents a specific grinding force. A set of a grinding test, the fabrication of MDA composed of 2107 microdimples and the measurement of the ADC by forming 18 microdimples before and after the MDA fabrication, was performed twice to evaluate the wear resistance of the grinding tool. The grinding test using the grinding tool with grooves twisted counterclockwise revealed that the tool enabled us to increase the ADC by 1.5-fold, compared with the tool without grooves, and that 4214 micrpdimples with a diameter flattening of less than 0.01 and a surface roughness of less than 10 nmRz were successively fabricated. Although it was difficult to fabricate these 4214 microdimples without any diameter change, the standard variation of the microdimple diameter was 0.07 μm when the ADC of the grinding tool became stable with the fabrication of more than 3000 microdimples.

In this study, we identify the effects of dynamic characteristics of the robotic walker on the muscle activities and operating forces of the young healthy subjects in sit-to-walk (STW) movement. The experiment was performed under a total of eight conditions where the dynamic characteristics, inertia, damping, and frictional force were changed in the STW movement. We analyzed the effect of the dynamic characteristics of the robotic walker on the muscle activity and operating force of the upper and lower limb muscle groups in the STW movement by multiple regression analysis. From the experimental results, it is revealed that the inertia of the robotic walker can change the load on the user's vastus lateralis and tibialis anterior muscle in the standing movement under the condition that friction is applied as a load, and the effect of the friction force of the robotic walker on the operation force is clarified from the viewpoint of walking stability of the user. Furthermore, we clarify that the damping and friction of the robotic walker can change the load on the user's rectus femoris, tibialis anterior, and gastrocnemius muscle in the transition phase from the standing movement to the walking movement.

Bridge noise may increase when a train with local wears on wheel treads runs at higher speed. In this study we developed the estimation method for bridge noise at a high-speed section based on permanent accelerometers at a low-speed section. We proposed combining outputs of three accelerometers to measure precisely the influence of the wear of each wheel on rail vibration at the low-speed section, since the influence of the wear is attenuated depending on distance between a position of an accelerometer and that of where the local wear contacts rail. Composite measured data at the low-speed section showed that rail vibration affected by the local wear can be measured independent of distance between them. We also proposed an estimation method that converts the rail vibration at the low-speed section into that at the high-speed section to predict the bridge noises during train running at the high-speed section. In the estimation, the vibration properties of a wheel, a track and a contact spring at each section are used, and it is assumed that a wheel roughness is greater than a rail roughness at the spatial frequencies where the effect due to the local wear appears. The impulse excitation tests were carried out to obtain these vibration properties and transfer functions in vibration from the rail to the bridge at the high-speed section. The transfer functions are used to estimate bridge vibration using the rail vibration induced by one wheel. The bridge noise generated by one wheel is also estimated from the bridge vibration by taking account of the radiation area of the viaduct. Summing the vibrations and noise generated by all wheels in one train results in the overall bridge vibration and noise. The estimated results at the high-speed section show a good agreement with the measured one at the frequencies where the local wear has a stronger effect.

There are many vehicles passing through on main road. On main roads, various safety countermeasures are constructed for securing traffic safety of a large number of vehicles. For example, separate sidewalks and driveways, or constructing median strips to prevent a head-on collision with vehicles going in the opposite direction, etc. On the other hand, the width of the residential areal road is narrow and the center line that separates the round-trip traffic of vehicles is not drawn. In addition, the separation of sidewalks and driveways is incomplete. Therefore, the residential areal road is not suitable for many vehicles passing through. For these reasons, under normal traffic conditions, many drivers choose to drive on main roads. However, when traffic jams occur on the main road, the number of vehicles flowing from the main road to the residential areal road increases in order to avoid the traffic jam. In a previous study, the authors have clarified that the traffic volume of parallel residential areal roads increases during the time when the length of traffic jams or the time required to pass the intersection becomes long on the main road during the morning and evening commuting hours. Then, it was clarified that the frequency of sudden braking on the residential areal road and the frequency of "dangerous experiences" by junior high school students passing through are increasing. In this study, we investigated the section where traffic jams occur during the morning and evening commuting hours of National Highway No. 2 in Fukuyama City, Hiroshima Prefecture, and the residential areal roads parallel to this section. Then, the authors verified that the residential areal road is a loophole of National Highway No. 2 by performing a traffic route analysis using ETC2.0 data. In addition, by analyzing the traffic accidents that occur on this residential areal road , we clarified the dangers hidden in this road used as a loophole, importance appropriately.