Joint strength of dissimilar thin pipe friction welded joints between 5052 Al alloy (A5052) and 304 stainless steel (SUS304) was investigated. Pipes had the outer diameter of 16 mm and the inner diameter of 12 mm, and those were welded with a friction speed of 27.5 s−1, a friction pressure of 30 MPa, and a friction time of 1.2 s. When joints were made with as-received pipes, the joint strength at a forge pressure of 60 MPa had approximately 64% in the tensile strength of the A5052 base metal although that had scattering. Almost all joints fractured between the weld interface and the A5052 side though some joints fractured in the A5052 side. Thus, the fractured portion of joints had scattering at the same friction welding condition. On the other hand, the joint strength at a forge pressure of 50 MPa had approximately 77% in the tensile strength of the A5052 base metal when joints were made by pipes with the machined of the inner and outer diameter parts from solid bars. In addition, all joints fractured from the A5052 side. That is, to obtain good joint such as the fracture in the A5052 side without scattering of the fractured portion of joints, the joint should be made without the affected layer on the pipe surface at the manufacturing of itself.
ISO230-1, an international standard of test code for machine tools, has been revised for the first time in 16 years. A volumetric accuracy for three linear axes was defined as a term of multi-axes motion in the revision of ISO 230-1. As a matter of course, the volumetric accuracy is closely connected with the linear axis error motions in three axis machining centers. The error motions of linear axes have been checked in compliance with ISO 10791-1 and -4 for a long time. However, the relationship between the measured error motions of linear axis and volumetric accuracy has not become clear. In this paper, the positional deviations of lattice points within the entire working volume of machining centers were measured via laser interferometer. Positional deviations were estimated by using a mathematical model in consideration of measurement coordinate systems and the tested linear error motions. As the results, the estimated positional deviations of the volumetric accuracy corresponded reasonably well with the measured deviations in a small machining center.
In wire electrical discharge machining (wire EDM), debris tends to stagnate around the wire electrode, since the machined kerf is very narrow. Then, secondary discharges often occur and discharges easily concentrate on the same location, which leads to unstable machining performance, such as frequent wire breakage, low machining rate and low shape accuracy. Thus, better exclusion of debris and bubbles from the gap is very important to obtain stable electrical discharges and high machining accuracy. Conventionally, the debris exclusion from the gap has been carried out by jet flushing of working fluid from upper and lower nozzles. However, in the case of conventional nozzle flushing method, a vortex flow area around middle region behind the wire electrode always generates by inclined flows from the upper and lower nozzles. Therefore, much debris generating in the front surface of wire electrode stagnates in the area. In order to improve the wire EDM characteristics, the vortex flow area should be eliminated or reduced, for improvement of the wire EDM characteristics. This study aims to propose new jet flushing methods for smooth debris exclusion from the gap in wire EDM, leading to high-performance wire EDM characteristics. In this paper, a nozzle jet flushing method with a fine insert following behind the wire electrode is newly proposed, considering smooth debris exclusion by utilizing computational fluid dynamics (CFD) analysis, and the effectiveness of the jet flushing method are experimentally investigated.The analysis results clarify that debris exclusion can be greatly improved by the insert nozzle flushing method, since the working fluid flow around the wire electrode is optimally controlled with a reduced stagnation area, resulting in low debris stagnation. It is also confirmed that the wire EDM characteristics can be improved practically by using the insert nozzle flushing method.
A sphere is a frequently used shape as a reference of calibration for 3-dimensional measurement instruments because of its isotropic shape. It is demanded to measure the diameter of the reference sphere with high accuracy. For micro-scale 3-dimentional metrology, size of the reference sphere is from several millimeters to a few tens of micrometers. These spheres have to be measured with accuracy of better than 10 nm. Therefore, we have proposed the new measurement method of a microsphere based on whispering gallery mode resonances. One of the key points to the proposed method is to measure the whispering gallery mode resonant wavelength accurately and precisely. In this paper, the measurement system for WGM was developed. Using this system, the measurement repeatability of WGM resonant wavelength better than 0.2 pm was achieved.
In a large-area electron beam (EB) irradiation method developed recently, the large-area EB with high energy density can be obtained without focusing the beam. It can be used for melting and evaporating metal surface instantly. Therefore, highly efficient surface finishing for mold steels can be done by the EB irradiation. It was also clarified that surface functions such as wear resistance and corrosion resistance of mold steels were improved by formation of modified layer on the surface after melting and resolidification of workpiece surface. On the other hand, the workpiece surface was slightly removed by evaporating the surface. Then, control and prediction of modified layer and removal thickness are effective to maintain the surface function. In this study, influence of magnetic property for workpiece on thickness of removal and modified layers in large-area EB irradiation is investigated. Experimental results show that the thickness of removal and modified layers on workpiece with high relative permeability is larger than that with low one. These results suggest that high energy density of EB is irradiated to the workpiece with high relative permeability. Therefore, the analyzed energy density on workpiece surface is calculated by using an electron track analysis. The energy density on workpiece with high relative permeability is larger than that with low one since EB more concentrates on the surface of workpiece with high relative permeability. Variations of removal and modified layer thickness for workpiece with different magnetic property can be precisely predicted by using an unsteady heat conduction analysis with considering EB concentration.
There is an increasing demand of high-value-added workpieces that generally have three dimensional and complex shapes such as aircraft parts. In complex parts machining, workpiece shape and stiffness change greatly during a rough machining operation and induce workpiece displacement and vibration that strongly affect machining accuracy and tool life. However, it is difficult to automatically determine machining process parameters such as cutting sequence, tool paths and cutting conditions by using a commercial CAM system because there is a large number of combinations. Therefore, in order to improve the efficiency of complex parts machining, it is necessary to clarify these tacit knowledges and to formulate the implicit machining know-how owned by skillful experts. The authors have been proposed a determination method of complex workpiece shapes during a rough machining operation based on topology optimization. In the method, topology optimization is used to calculate workpiece shapes to ensure the stiffness by dividing a rough machining operation into several steps. However, the operation planning has not been adequately considered to determine machining process parameters. Moreover, it is necessary to repeat the calculation of topology optimization because a rough machining operation is divided into many machining steps. Thus, in this study, a determination method of cutting sequence is proposed by using the design variables obtained in the calculation process of topology optimization of workpiece. In order to estimate the machined shape based on the proposed cutting sequence, cutting experiments are conducted. The results show the effectiveness of the proposed cutting sequence to reduce the deformation of workpiece during a rough machining operation of complex parts machining.
Directed Energy Deposition (DED), which is one of the Additive Manufacturing (AM) processes, can deposit metallic production efficiently by irradiating a high-power laser beam on a baseplate and supplying material powder simultaneously. DED has a problem in low mechanical strength due to residual pore inside of the production. However, the residual pore is also available to fabricate low density production as an opponent idea. If the residual pore could be increased intentionally and drastically, DED is applicable to foam metal fabrication. Foam metal could be produced continuously with high degree of freedom in shaping, if melt-pool can be foamed in DED. Therefore, this paper proposes a simple fabrication method for foam stainless alloy with DED by applying titanium hydride (TiH2) as a foaming agent for melt pool. TiH2 releases hydrogen in a high temperature environment as more than 500℃. Considering that high viscosity and low surface tension are required to stabilize pore generation, material powder also should contain a thickening agent (CaO: calcium oxide) and a surface active agent (Te: tellurium). According to the experimental results, an effect of CaO was hardly observed because the liquid stainless may already have high viscosity enough. On the other hand, Te certainly reduced the critical film thickness and prevented the pore collapse in stainless foam fabrication, according to the porosity rate calculation, the observation with a high speed camera, and the elemental distribution analysis. Furthermore, the proposed method successfully produced a foam structure in stainless steel with high porosity rate as 61% at maximum.
This paper describes the novel on-machine measurement method of tool edge shape by using fluorescence emitted from cutting fluid. Tool wear and chipping are a major factor of decreasing machining accuracy. Therefore, on-machine measurement methods of tool edge shape with high accuracy are the subject of intensive study. Especially, considering the machining process, a robust measurement method with water-soluble cutting fluid is required for precise machining. For these reasons, the purpose of this research is to develop the technique that enables to measure tool edge shape precisely by using a confocal microscope. In order to achieve it, we have proposed the measurement method of tool edge shape by detecting fluorescence of cutting fluid adhering to the tool edge. Previous research has shown that it is possible to measure tool edge shape precisely by using oily cutting fluid. However, the applicability to water soluble cutting fluid is still remained. In particular, since water-soluble cutting fluid is used with dilution, it is worried that its fluorescence emission efficiency is lower than oily cutting fluid and the fluorescence detection is difficult. In this paper, it is shown that fluorescence could be detected from water-soluble cutting fluid. Then, the cutting tool edge shape adhering water-soluble cutting fluid is measured. These results show that the proposed method has high applicability to an on-machine measurement.
Manufacturing technology for three-dimensional nano/micro-structures has been desired. In this study, we newly proposed the laser additive manufacturing method in vapor phase, by utilizing optical trapping potential to confine particles in a range smaller than diffraction limit of laser beam. In this paper, we have developed the optical trapping system with Bessel beam in order to investigate feasibility of the proposed fabrication methods. The water droplet of several µm in diameter containing particles suspended in space were successfully trapped in the optical potential of Bessel beam and then the only particles were deposited on the substrate. As a result of processing experiment, the silica particles with a diameter of 1 µm could be three dimensionally structured on the axis of the Bessel beam.
The drag and lift forces acting on a droplet moving near a plane wall were numerically investigated using a three-dimensional direct numerical simulation (DNS) based on the marker and cell (MAC) method. The numerical results showed that the presence of the wall causes an increase in the drag force. The less viscosity ratio of the internal fluid to the external fluid caused the decrease in the wall-induced drag coefficient. The direction of the wall-induced lift force acting on a droplet near the wall changed depending on the viscosity ratio in the high Reynolds number cases. At low Reynolds numbers, the wall-induced drag and lift coefficients of a droplet had the similarity for different viscosity ratios, respectively.
In this paper, heat transfer characteristics and the pressure drop response of sandwich structures containing open-cell core were studied by using numerical simulation. The effect of micro-architecture and cell size of the unit cell on these characteristics were investigated by changing relative density of the models. In this paper, three types of open-cell were analyzed. There is a trade-off relationship between the heat transfer characteristics and the pressure drop response. These factors are the direction of thermal paths, surface area size and internal flow state. Also, these factors can be controlled without changing the relative density when the cell size is changed and the aspect ratio is equal. In order to clarify the characteristics of the open-cell, the open-cell were compared with two types of closed-cell as representative of other cores in terms of two dimensionless numbers (Nusselt number and friction factor). As a result, it was confirmed that the open-cell has high superiority in applications requiring light weight and high heat transfer characteristics.
This paper is concerned with the demonstration of scallop-like swimming with the aid of robot toy; using jet propulsion by clapping the shells quickly. Previous works from biological approach have indicated what structures contributes to generate the jet propulsion. This paper tries to perform quick underwater locomotion by mimicking the structures of scallop based on constructive approach: development of scallop-like robot with autonomous generation of jet propulsion. After designing the structure and actuation mechanism by mimicking the scallop, we focus on the effect of the mantle property on swimming. Firstly we confirm that developed robot can perform scallop-like swimming. Secondly we also compare the swimming speed by changing the property of designed mantles.
Low back disorder is a commonly observed worker injury in Japan. Statistical figures revealed that there were 600 to 900 workers who were absent from work more than four days every year because of the low back pain caused by handling heavy objects in the manufacturing industries. Use of mechanical lifters can be a solution but there are still many ill-shaped heavy objects which should be handled manually in the workplace. Wearable power assist devices can provide physical support to workers who are handling heavy loads in their daily work. The present paper proposes a two-class weight discriminator for lifting-up motion of a human worker, looking to use the output of the proposed discriminator in the control of the wearable power assist device in the future. The proposed discriminator mainly uses the magnitude of two dimensional acceleration spikes measured during a lift-up task using an accelerometer mounted on his/her shoulder, when he/she is trying to do a lift-up motion. We formulated and trained both the linear and the nonlinear support vector machines (SVMs) for the classification of the feature vectors, and evaluated the trained SVMs with independent evaluation dataset. Satisfactory discrimination accuracy has been observed both with the linear and the nonlinear SVMs which use the reaction acceleration feature values. We also evaluated the use of additional three dimensional accumulated body motion accelerations as supplemental feature vector elements. Higher dimensional SVMs were formulated and trained accordingly and the result of discrimination accuracy clarified both positive and negative aspects of high dimensional feature vector for the discrimination of two load weight classes in lift-up motions.
Continually using the machine with the vibration may lead to a blood circulation failure to a hand. Vertical vibration and the torsional vibration are generated on the handle part of those machines. If the particle damper is attached on such a machine, an impact to act on a hand may be reduced. The particle damper is a device decreasing vibration by many particles which are filled into the container of the collision damper. It is difficult to experimentally observe the complex behavior of particles in the container since compressive forces, frictional forces, and impacts are generated between particles and the wall. Therefore, calculation of particle behavior by modeling a discrete body that contains the particles and the container is necessary. Discrete element method (DEM) might be one of the effective methods for its simulation. In this study, the torsional vibration is focused on and the characteristic of the damper examined through experiments and DEM simulation. In the experiment and simulation, many spherical particles as impactors were filled into a container. The container was given periodically a twist motion. The calculation results were compared with the experimental results by means of provided resonance curve. As a result, it turned out that the torsional vibration decreases when the selected particles which have a suitable particle diameter and a filling ratio were filled into the container.
This paper proposes a control allocation method for the motion control in which the number of manipulated variables is one more than control degree of freedom. Proposed method is formulated as an optimization problem including several Quadratic Programming sub-problems (QPs), and can calculate optimal allocation in real-time. The real-time performance is improved by the Parallel Quadratic Programming (PQP) method. The effect of the proposed method is verified by numerical simulations in terms of control response and calculation time. Furthermore, in order to suppress the steep change of manipulated variables in proposed method, rate limiter process is added to the latter part of proposed method. It indicates by numerical simulations even if rate limiter process is provided after the optimization calculation, it is possible to perform a trajectory tracking by feedback control.
It is known that mechanical behavior of a composite structure is strongly influenced by not only the shape and properties of the macroscopic region but also the shape and properties of the micro region. In this study, we propose a multi-scale shape optimization method to design the shape of a periodic microstructure. The method consists of two-step optimization. At first, the material properties of a macrostructure are optimized using a size-optimization technique, where the components of the liner elastic tensor are set as the design variables. Objective function and the constraints are set according to design purpose. Next, the shapes of periodic-microstructures are determined to identity the material properties of the macrostructures obtained in the first step, where the inverse homogenization method and the H1 gradient method are used. The shape optimization problem of a microstructure is formulated as a distributed-parameter optimization problem, in which the mass is set as an objective functional and the shape variation field is set as a design variable, as the constraints are the target macroscopic material properties and the homogenization equation. Through numerical calculation examples, we confirmed the effectiveness of the proposed method based on the inverse homogenization method and the H1 gradient method.
To improve productivity and energy efficiency, attention has been paid to practical methods to evaluate productivity and energy consumption in actual manufacturing processes. In the plastics industry, the injection molding machine is one of the common production machines for manufacturing plastic parts. It consumes a large amount of energy due to having injection molding processes such as melting the material. In addition, a production line including the injection molding machine generally has various auxiliary machines to improve productivity and maintain product quality. Since the states of each machine in the production line change based on production situations, the behavior of energy consumption in the production line becomes more complicated. Therefore, it is difficult to evaluate energy consumption in the production line while grasping dynamically changing the states of each machine. This paper proposes a simulation system that simultaneously evaluates productivity and energy consumption in the production lines including the injection molding machine for design and improvement of production line. To simulate productivity and energy consumption, we develop a state transition model in the production line. This model defines the interrelationship between state transitions and their sequence among the machines. Furthermore, by making a correlation between the machine state and its energy consumption, the state transition model enables to calculate energy consumption in various production scenarios. By implementing the state transition model in a discrete-event simulation, it is possible to evaluate the indicators of productivity and energy consumption such as throughput and specific energy consumption. To verify the effectiveness of the proposed simulation system, we show a case study of productivity and energy consumption when designing a new production line including an injection molding machine. The results show that we obtain the evaluation indicators of productivity and energy consumption regarding various production lines.
We proposed an advanced mesh generation technique that reuses the proven analysis models by similar sub-part search. The purpose of this research is to reduce interactive mesh improvement work time and to comply with the mesh specifications. It is our feature technique to search sub-parts similar to the archived sub-parts of proven models from new design CAD. In this technique, the similar sub-parts are retrieved from a CAD model described by boundary representation and made correspondence relation surface pairs of a retrieval model (proven model) and a target model (CAD of new design). A similarity score is based on the attributed graphs of a retrieval model and a target model. And, this score is calculated by a geometrical similarity and topological similarity. If there is such search noise, unreusing sub-parts must be canceled by interactive operation. This is an obstacle to automation. Therefore, with the goal of eliminating search noise, we developed a technique to improve the accuracy of similar partial shape retrieval. By quantifying the geometric relationships such as concentric circles and face-to-face distance as similarity, high precision could be realized. It was applied to a door switch cover part of an automobile which is a verification model, and it was confirmed that search noises disappeared.
We have already developed a speech-driven embodied entrainment CG character system called “InterActor” which generates communicative motions and actions such as nods for entrained interaction from speech rhythm based on only voice input. Conventional InterActor performed the entrained communicative body movements and actions based on speech input without a voice back-channel. In this study, we develop an embodied character system with the voice backchannel based on the embodied interaction model. Two experiments are performed to confirm the effectiveness of the system by sensory evaluation. In the first experiment, the effects of the automatic generation and presentation method of the voice back-channel are examined in each situation with and without character presentation. In the second experiment, the frequency of the voice back-channel to nodding motion is examined. The effectiveness of the system is confirmed from these experimental results.
Large number of simulations or experiments is needed for optimization and uncertainty quantification of a mechanical system. Therefore, if simulations or experiments are numerically expensive and time consuming, it is difficult to execute optimization and uncertainty quantification in practical cost and time. To reduce the cost and time, a surrogate model is often used. The surrogate model is a mathematical model which represents a relationship between control variables and corresponding response value. The surrogate model is constructed from sampling data; a set of results of simulations or experiments with different values of control variables. When the surrogate model is used for optimization and uncertainty quantification, its result depends greatly on an accuracy of the surrogate model. Hence, it is important to construct an accurate surrogate model. Generally, an accuracy of the surrogate model increases as a number of sampling data increases. However, if a number of sampling data increase, the cost and time to make them also increase, which should be avoided. Therefore, it is necessary to develop a methodology which can construct an accurate surrogate model with fewer number of sampling data. In mechanical design problems, there often exist experimental equations which represent relationships between control variables and response values. In this study, we proposed a method which uses the experimental equations to improve an accuracy of the surrogate surface. In the proposed method, the experimental equation and its parameters are used as priori knowledge for constructing a surrogate model, and values of parameters and an offset between the experimental equation and true values are estimated simultaneously based on sampling data. We applied the proposed method to construct surrogate models for a heat resistance and a pressure drop of a pin-fin heat sink. As a result, it is shown that the proposed method can construct surrogate models which gives better estimation than conventional methods and has robustness to accuracies of priori knowledges.
Improving space sufficiency of cabin is one of significant factor in enhancing the value of automobiles. However, experiment with actual automobile mock-up requires excessive time and cost. Our aim of this study was to investigate the feasibility of spaciousness evaluation of automobile cabin by using virtual reality (VR). Twelve students (6 males and 6 females) participated in this study. The participants evaluated the visual spaciousness of automobile CG models with different roof heights R (0, +50, and +100 mm) and windshield depth W (0, +100, and +200 mm). The views from driver seat in the VR space were provided, and the subjective space sufficiency was measured in a 7-point Likert scale. The result showed that the average space sufficiency increased with the increase of the roof height and windshield depth, whereas it was almost constant irrespective of the windshield depth when R = +100 mm. The effect of roof height was statistically significant, whereas that of windshield was not significant. The relationship between the probability of the subjective score and the two factors (i.e., roof height and windshield depth) was formulated by applying the ordered logistic regression to the measured data. In addition, the results of ordered logistic regression were compared with a previous study in which the space sufficiency was measured in real space using an actual automobile mock-up. The results of the ordered logistic regression of this study roughly agreed with the previous study.
DLC (Diamond-Like Carbon) has excellent tribological properties such as high hardness, low friction and high wear resistance. It is widely applied in industrial field. In order to prevent excessive wear, DLC is also applied to the vane which is the main sliding component of the compressor for air conditioning. In this study, we investigated the wear reduction effect on sliding surface between the DLC vane and the compressor roller which is made of cast iron. As a result, the DLC vane can reduce the wear of the surface of roller compared to a nitriding vane. And it is found that carbon film is formed on sliding surface of the roller in the case of using DLC vane. This carbon film does not have the structure of DLC but the structure of glassy like carbon. We consider that this carbon film is generated from the graphite composition of the roller by friction heat and it contributes to the wear reduction of roller. Furthermore, we carried out experiments using rollers containing different content ratios of graphite on the surface, and confirmed that the same wear reduction effect exists owing to the carbon film.
Industrial machinery accidents occupy a quarter of the whole accidents in manufacturing industry, and the ratio is increasing. In these accidents, some of the workers were killed or seriously injured when they were crushed or jammed by industrial machines since these machines have a big power. There are safeguarding equipments such as area sensors and guards at working areas of factories which prevent workers from hazards. Although these equipments are effective in automatic operation of the machines, they are often disabled during adjustment, cleaning, error recovery, or any other maintenance of machines. Many accidents are reported at non-routine work due to a human error when safeguarding was disabled. In order to make workplaces safe, the authors propose a risk-reduction system for air cylinders. The proposed system is attached to the rod end of a typical air-cylinder, and it makes a quick retract when a hand is mechanically detected at the end of the system. The system reduces possible crush risks from an air cylinder without using any external safeguarding system. This paper describes a novel structural principle of the proposed system. The performance of a prototype system is evaluated and the system is proved to be effective in reducing crush risks.
Battery train is in development as train which can travel in non-electrified section using power supplied from onboard storage system such as lithium-ion battery. However, as characteristics of this type of train, an energy consumption of battery train depends on the state of charge of the storage system. In consideration of these characteristics, we propose a generation method of the timetable which is the most energy-saving when a single battery train travels on a route section containing multiple stations in this research. Although this optimization can be defined as a nonlinear programming problem, we ease to solve this problem using linear approximation to the energy consumption characteristic. In the end, we carried out a simulation in a simple case and achieved 4.7% reduction in energy consumption by the proposed method.
This paper describes a method for statistically estimating five components included in the time series of vertical track geometry measured at the same point on a railway track. We have developed a statistical model to represent the change of vertical track geometry. The model decomposes the time series into five components: seasonality, trend, effects of maintenance works, short-term variation, and noise. The vertical geometry in the near future is also forecasted with the components. Two features of the model are as follows: first, the model extracts the effects of seasonal variations. We actually identified track geometry that changes seasonally at some fixed points. The seasonal variations are found to be relevant to rather air temperature than train loads. This finding is contrary to a general belief that track geometry changes monotonically due to daily train loads. Second, the Kalman filter algorithm is applicable to this model. The parameters included in the model are thus estimated effectively according to the maximum likelihood method. In addition, the five components are obtained according to the fixed-interval smoothing algorithm. The goals of this study are to help the scheduling of railway track maintenance with forecasted track geometry and to obtain new information on changes of track geometry.
Interior design of train cabins play an important role in providing comfortable transportation, since visual stimuli have major psychological impact on passengers. To evaluate the amenity of cabin’s interior design, we focused on data of brain activity which lead to intuitive favorability obtained by NIRS in addition to a subjective evaluation by questionnaire. We made an intuitive sight evaluation of interior design for Shinkansen by observing brain activity in reaction to a variety of image showing different combinations of cabin facilities’ colors and lighting color temperature to propose appropriate conditions for a comfortable cabin environment. As a result, on the whole, lighting color temperatures of 5000K were more highly regarded except in the case of blue facilities. However, blue facilities were favored at illumination temperatures of 3500K. On the other hand, the case of red facilities was more highly regarded in the highest lighting color temperature of 6500K. Moreover, to verify the impact of visual stimuli while train is in motion, subjects wearing virtual reality headsets were seated in a train-riding simulator, and stress brain indices and mood brain indices were measured in addition to a subjective evaluation. In the case of blue (3500K), the subjects consistently felt stress-free. We found that a combination of cool-color of facilities and warm-color light temperature is most preferable, which shows good agreement with the results obtained from subjective evaluation by questionnaire. Consequently, NIRS is useful to evaluate the amenity of cabin’s interior design.
Automated driving vehicle technology is expected to solve several road traffic issues. Therefore, this technology has been receiving increased attention and several relevant experiments have been conducted. This paper describes the development and verification of target trajectory and speed control target calculation. The control target calculation system of the autonomous vehicle algorithm, which is the focus of this study, mimics an expert driver's direction and speed control in detail. The proposed algorithm consists of a driver model, which considers the risk potential, and vehicle dynamics model like a human driver. We think that a human driver drives under the influence of some obstacles and the oncoming vehicle on the road. And they change a driving action so that their risk is always kept low. At first we measured the traveling path and vehicle speed as a driving action of the human driver by the experiment in the real traffic condition. Next, we reproduced the driving action of the human driver by the proposed algorithm. The parameter of the risk potential driver model was estimated by the experiment results. In addition, we performed inspection by the simulation about calculated control target. As a result, it was confirmed that direction control and the vehicle speed control by proposed algorithm simulated the driving of the human driver in detail.
The part of rail joint becomes the cause of the disadvantage points such as ride discomfort, undesired sound and track maintenance, etc. For restraining those points, the long rail made by welding the standard length rails has been developed. However, the problems of the buckling caused by the axial stress (i.e. the thermal stress which is brought out by the weather conditions or the friction heat between wheel and rail) of the rail have been pointed out. Therefore, some evaluation techniques for buckling management have been proposed. In this study, the relationship between the increase in compressive stress and the behaviors of the characteristics of the wavelet transform (i.e. a kind of time-frequency analysis) results of ultrasonic echoes was researched. The stress was increased in 10 [MPa] interval, and the echo at each stress was detected. From the results of experiment and analysis, it became clear that there is the relatively correlation between three characteristics and the stress. They are RMWC, RWE and RKTW respectively. The value of each RMWC, RWE and RKTW shows the ratio to the initial value (i.e. shows at 0[MPa] in this case) of MWC (i.e. the maximum wavelet coefficient), WE (i.e. wavelet energy) and KTW (i.e. the kurtosis of the time fluctuation waveform of the wavelet coefficient of the frequency that indicates MWC). Therefore, it was able to show the possibility of comparatively accurately predicting the increment of the stress by comparing the transitions of those.
Rail corrugation is a periodic rail surface roughness that is formed as the rolling stock runs repeatedly on the rail. The rail corrugation occurs in various track alignment and track structures, but the generation mechanism and wavelength determination mechanism are often unknown. Therefore, in this paper, in order to measure the rail surface roughness of rail corrugation in detail, we have developed a trolley that can measure rail surface roughness continuously regardless of moving speed of the device. At that time, the asymmetrical chord method widely used in track geometry cars was adopted as a measurement method of the rail surface roughness in the longitudinal direction of the track. In this way, we considered to measure the rail surface roughness with any wavelength with high accuracy, and verified the measurement accuracy. Finally, we indicated that measurement cases at commercial lines, and the prospect of how to use the developed trolley.
In order to study chassis specifications, we considered a tire physical property Model that could identify cornering stiffness accurately, and devised TM Tire Model. TM Tire Model is derived from the detailed representation of tire cornering compliance. Two characteristics of cornering compliance and cornering stiffness were identified using TM Tire Model and compared with the existing physical property Model, it was verified that TM Tire Model is superior to the existing tire Model. We describe the internal configuration and evaluation results of TM Tire Model in this paper.