This paper starts with describing a method of deriving the resonance mode of a pendulum utilizing its equation of motion. This resonance mode is that the equilibrium position of the pendulum locates the vertical plane including its fixed point and the mass accelerates in proportion to the distance from the equilibrium position to its mass. Further, the equation of motion of vehicles was converted to a form conforming to the equation of motion of the pendulum. As a result, it was found that the equilibrium position of yaw resonance is the extension line of the vehicle speed vector at the front wheel position. Moreover, it turned out that its rear wheel accelerates toward this extension line in proportion to the distance from this extension line to the rear wheel is the yaw resonance mode under a special condition. Finally, the step steering response was considered. At the moment of steering input, the mode of the yaw lead time constant appears, and then the yaw resonance mode becomes apparent. Hence, the yaw resonance is revealed in the latter half of the transient response. Therefore, it is considered that the yaw natural frequency is suitable as a metric of the latter half behavior of the transient response.
Influence of body stiffness on vehicle maneuverability and handling characteristics has been open problem for decades. This paper focuses on the influence of the high frequency body vibration on human motion sensitivity, and clarifies that the vibration reduction in the 20 Hz band shortens the time to recognize the lateral motion during the minute lane change. Furthermore, we derive sensory quantity of the lateral motion from skin shear displacement on the contact point with sheet back, and clarify the mechanism that "vibration reduction in the 20 Hz band reduces the noise of the sensory quantity of lateral motion and shortens the recognition time of the lateral motion". This shows that "vehicle body vibration characteristics in the 20 Hz band effect vehicle maneuver feeling".
In recent years, as a natural disaster in Japan, there were damage from the 2011 Tohoku Region Pacific Offshore Earthquake and the 2016 Kumamoto Earthquake. In the event of a disaster, people who are difficult to evacuate can not escape, and sometimes they die. In this research, we investigate damage situation on natural disasters in recent years, and make basic experiments on running experiments simulating bad roads after disasters. Based on the results obtained from experiments, we aim to propose a wheelchair that can be utilized at the time of a disaster or after a disaster. In addition, riding comfort analysis was carried out using the vibration measuring device during the experiment. From the results of the research, it was shown that the introduction of a wheelchair driven vehicle aimed at reducing the load assuming natural disasters is effective. Also, by increasing the size of the front wheel, it is possible to alleviate the gap between the step and the step. It is possible to reduce the load exerted on the body by using a tire with less electric assistance or less resistance.
In railways, on-track running tests are implemented to assess running safety against flange climb derailment. Results of tests depend on the frequency component of measured data. In this paper, the relationship between the measured data of the derailment quotient, which is the assessment quantity of derailment, and wheel rise are investigated. The data for the investigation are obtained in a flange climb running test at low speed on a test track, which includes two sharp curves with cants. Several types of track irregularities, such as track twist, rail misalignment and angular bent at joints, are added to the test track, which are some of factors causing flange climb derailment. Some static wheel unloading is also set at the test vehicle's leading wheelset to induce flange climbing. We show that the derailment quotient data obtained through filter processing with some cutoff frequencies and the amount of wheel rise of the leading outer wheel have a similar tendency in time sequence, which indicates the usability of the filtered derailment quotient data for the assessment of flange climb derailment at low speed. Further, the cumulative value of the derailment quotient which is larger than the target maximum value is examined in order to evaluate the safety margin for derailment more precisely compared to the ordinary assessment by the derailment quotient only. As a result, we propose a new assessment quantity considering the cumulative value, and its target maximum value derived from the wheel rise and running distance.
Shape Memory Alloy (SMA) actuators must be continued to be heated generally to retain a shape of a smart structure deformed by the SMA actuators. To save the energy applying to the smart structure, a new control method was proposed utilizing the fact that strain is not single valued even at the same stress and temperature state due to hysteresis in stress-strain-temperature relationship of SMA. Feasibility study of the control method was performed by a fundamental experiment for an antagonistic SMA system. When a pulsed voltage was applied to one SMA, the system moved to some direction, and while the voltage was not applied to the SMA after the pulsed voltage, the system did not return to the original position and was remained at a certain position. Successively, when a larger pulsed voltage was applied to the same SMA or another pulsed voltage was applied to the other SMA, the system moved to the same direction more or the other direction, respectively, and was retained at certain positions without applying the voltages. To explain and confirm the behavior of the system, numerical simulation was also performed. The simulated result agreed with the experiment qualitatively and could explain the mechanism of the behavior. From the results mentioned above, the feasibility of the proposed control method could be shown both experimentally and numerically.
The rail is one of the most important elements in constructing railway system. The phenomenon such as wear or defect of rail will be caused by the repeated wheel/rail rolling contact. The wear of rail, which will not develop in a short period of time, has a close relation to crack initiation. Further, there is a possibility that the worn profile of rail influences the running stability or the curving performance of vehicle. Therefore, it is very important to analyze the wear development of the rail. Previously, we constructed the prototyped model for predicting worn profiles of rail with Simpack and validated of this model. At the same time, the wear of rail occurs more outstandingly in the curved section than in the straight section. In the curved section, the wheel passes with an attack angle, which gives rise to not only longitudinal slips but also lateral slips at the wheel/rail contact patch. In previous research, longitudinal slips and lateral slips have been treated as the equivalent. In this research, we conducted wear experiments by use of wheel/rail rolling contact test equipment to examine the influence of lateral slips on wear development. Moreover, we constructed wear predicting model considering lateral slip and analyzed the worn profile of rail in the same contact condition with the wear experiments. As a result of the experiments and the analysis, the analytical model was confirmed being valid to predict worn profile of rail considering lateral slip.
Under the existing method based on a detailed equation for evaluating the wind speed that can cause a vehicle to overturn, it is assumed that the crosswind blows the vehicle at the same wind speed uniformly over the entire length of the vehicle body along the track. However, taking into consideration the actual wind state, there is a wind speed distribution over the length of the vehicle body and there is a high possibility that the crosswind does not blow at the same wind speed over the entire length of the vehicle body. Therefore, if the wind speed distribution is considered, it becomes possible to evaluate the critical wind speed in more detail. In previous research, an evaluation formula of aerodynamic force in consideration of the wind speed distribution has been proposed with the natural wind direction assumed to be 90 degrees. On the other hand, the calculation of the wind speed that can cause a vehicle to overturn requires extending the evaluation formula so as to be applicable to the other natural wind directions. In this study we proposed, extending the existing evaluation formula, a method of calculating the critical wind speed in consideration of the spatial fluctuation of wind speed. We also evaluated the critical wind speed for the combination of the vehicle and the track constructions with the proposed method. In addition, we also evaluated the critical wind speed in accordance with changes in the height of the center of the car body from the ground and the roughness length. As a result of the evaluation, we confirmed that the critical wind speed increases by up to 1.4m/s, provided that the vehicles and railway structures are those assumed in this study.
In order to improve the running performance of a railway vehicle, the authors developed the axle box suspension with the magnetic elastomer. The magnetic elastomer is composed of magnetic particles and the elastomer such as synthetic rubber. This material is characterized by its hardness variation depending on the magnetic field. In this paper, the authors synthesized the bimodal magnetic elastomer containing nonmagnetic particles. In a characteristic test, the authors confirmed that Young's modulus of the magnetic elastomer changed in the range of about 2.2 times depending on the magnetic field. Moreover, the authors carried out a running test on a test line of the MIHARA Test Center. The authors confirmed that the axle box suspension with the magnetic elastomer were able to secure the running stability at 70 km/h without causing an unstable state. In addition, the authors carried out a running test on a test line of the Railway Technical Research Institute. The authors confirmed that the axle box suspension with the magnetic elastomer were able to reduce the outer lateral force of a leading wheelset.
Hunting oscillation is unfavorable to the running stability because it can generate relatively large lateral force between the wheels and tracks. In addition, once hunting oscillation occurs, it lasts until the running speed is reduced to some degree. Therefore, we have studied global stability against hunting oscillation by conducting hunting motion tests using a real bogie on roller rigs. In this study, we confirmed that there exists a clear point where initial lateral displacement of the wheelset caused hunting oscillation. Then, we concluded that the point in question originated from unstable limit cycles, generated by subcritical Hopf bifurcation. On the basis of the obtained global stability, we devised a simple method that could make the hunting oscillation converge to the equilibrium point by oscillating the roller rig, without slowing down the rotational speed of roller rigs.
It has been shown that passengers have large reduction effect on the elastic vibration of a railway vehicle car body. That effect is considered due to the viscoelastic motion and multi-directional motion of a human body. This study focuses on the latter one and aims to develop a new vibration reduction device to mimic the multi-directional motion of passengers. In this paper, an experimented multi-directional dynamic vibration absorber (called MDDVA in this report) is developed. The MDDVA consists of a steel ball supported resiliently by elastic balls bottled in a rigid cylindrical vessel. The steel ball can vibrate multi-directionally in the vessel and is expected to work as a MDDVA. In addition, the natural frequency of the MDDVA can be changed by pressing the elastic balls from the top. To evaluate the effectiveness of the MDDVA, excitation tests by means of a scale model of a railway vehicle is conducted. As a result, the MDDVA can reduce the elastic vibration by adjusting the natural frequency of MDDVA to that of the scale model, and multi-modal vibration reduction effect is successfully observed. And then, FEM models of the MDDVA and a scale model of the railway vehicle are constructed to verify the mechanism of the multi-modal vibration reduction. As a result of the FEM analysis, it is confirmed that the multi-directional motion of the steel ball produces the multi-modal vibration reduction effect.
The steering vibrations include the useful information, such as road condition, for the drivers. Therefore, the various evaluations about relations of the steering vibration characteristics and the road information are carried out. In this paper, the human vibration sensitivities of the steering vibration concerned with the road information were evaluated first. It is clarified that the vibration direction of frequency band more than 20Hz can’t be discriminated and the sensitivity of the vibration power is decrease at an incline of 10dB/dec for frequency. Next, the evaluating method of the steering vibration using the steering simulator was examined based on the human vibration sensitivities. As a result, it was clarified that the steering vibration can be evaluated by the vibration combination of the rotational vibration and the translation vibration more than 20 Hz.
This study examines a driver's judgment assistance system at a signalized intersection. The assistance system indicates the evaluation indices on a road ahead virtually using the Head-Up Display (HUD). The HUD for the driving simulator consists of a projector, a screen and a combiner. The assistance system informs a driver visually of the distance which the vehicle can advance by maintaining the present vehicle velocity until the red signal onset. The driving simulator experiments are conducted to evaluate the assistance system with the HUD. The assistance system encourages the driver to make the earlier deceleration before the amber signal onset and prevents the emergency braking behavior. In addition, the assistance system with the HUD maintains drivers' braking reaction time to the emergency deceleration of the preceding vehicle in comparison with the assistance system assuming the HUD, which is directly indicated on the road in the simulated front view. Indicating evaluation indices on the road ahead virtually through the HUD helps the driver to decelerate earlier and avoid the emergency braking maneuver. These effects make it possible to suppress the collision risk to the preceding vehicle and contribute to the safety driving.
In S-N diagrams for high strength steels, the duplex S-N curves for surface-initiated fracture and interior inclusion-initiated fracture were usually confirmed in the very high cycle regime. This trend is more distinct in the loading type of rotating bending due to the stress distribution. In the case of interior fracture mode, the fish-eye is usually observed on the fracture surface and an inclusion is also observed at the center of the fish-eye. In the present work, the authors have attempted to construct a probabilistic model on the statistical fatigue property of bearing steel in the interior fracture mode based on the distribution characteristics of the location and the size of the interior inclusion at the crack initiation site. The probability density functions of the radius of the largest inclusion among n of total inclusion, ρn and the inclusion depth, ξ were derived by connecting the concept of extremes distribution and Weibull distribution. The joint probability function for ρn and ξ is given by multiplication of the probability density functions of ρn and ξ. The distribution pattern of the fatigue strength at N=109 derived from the joint probability function is well corresponding to the experimental aspect of the fatigue strength distribution for the bearing steel of SUJ2.
In this paper, we aim to clarify the effect of cutting direction on the cutting characteristics of polyethylene terephthalate (PET) film with mechanical anisotropic properties during the wedge indentation process. In order to reveal the difference in the cutting line force due to the cutting direction, the wedge cutting force on the PET film was experimentally measured by choosing the cutting direction as the machine direction (MD) and the cross machine direction (CD), while the cutting profile of the PET film was observed from the side line direction. From the experiment, the cutting line force of PET film in orthogonal to CD was the larger than the cutting line force of PET film in orthogonal to MD. It was found that there were three deformation modes of the cutting profile and the occurrence frequency of these modes was changed with respect to the cutting direction. In addition, a finite element method (FEM) analysis was carried out to compare the cutting profile and the internal stress state in the sheared zone due to the difference of the cutting direction and the lubrication state. It was clarified that the cutting deformation of the PET film at the necked stage was characterized by the tensile test based mechanical properties and the frictional coefficients with the wedge blade and the underlay.
The relationship among strength, ductility, toughness and microstructure was studied in order to find out microstructure image of stronger and tougher steel. Initial samples with two different microstructures, ferrite-pearlite and martensite (and/or bainite), were prepared and then caliber rolling was conducted at warm working temperature. Two kinds of low carbon steel bars with ultrafine elongated grained (UFEG) structure in transverse grain size of 1.0 μm and 1.3 μm, respectively, were produced. For comparison, conventionally quenched and tempered 0.29%C steel and 1.03%C steel with a martensitic structure and low-carbon steel with ferrite (grain sizes, 10μm and 18μm)/pearlite structure were also prepared. The Charpy impact and static tensile tests were conducted at a temperature range from 200°C to －196°C. The reduction in area and the plastic deformation limit were used as a universal parameter of ductility. In the Charpy impact test, only the UFEG steels fractured with delamination crack, the delamination remarkably appeared near energy transition temperature and the impact energy becomes larger than all other steels. As a result, the UFEG steel with transverse grain size of 1.0 μm was best balance in correlation between strength and ductility and between strength and toughness.
Digital Image Correlation (DIC) method was applied to measure the strain fields around the crack tip in a Ni-base single crystal superalloy. DIC systems were assembled to appropriately measure the strain fields at room temperature, 700°C and 900°C. Influences of crystallographic orientation and temperature on the crack tip strain fields were investigated. A series of measurement at room temperature revealed that cracks propagated in shearing mode and the strain fields around the crack tip were strongly affected by anisotropic plastic deformation along the octahedral slip system. Based on the shear strain components along the slip systems, effect of the crystal orientation on the strain field was visualized, and the visualized strain field provided a reasonable explanation on the crack propagation path and propagation rate. At 700°C, on the contrary, cracks propagated in opening mode and symmetric shear strain fields were measured around the crack tip. Temperature dependent strain fields and resultant cracking modes were explained by the slip system activity which was also influenced by temperature. The present DIC systems could measure the strain field even at 900°C, and it was found that the strain around the crack tip was higher at 900°C than that at 700°C.
An underexpanded radial jet is generated downstream of intake and exhaust valves of an internal combustion engine, a pressure control valve and so on. In addition, when a supersonic jet issuing from a circular nozzle impinges on a flat plate, the wall jet on the plate often becomes underexpanded and spreads out radially. The underexpanded jet has typical shock-cell structure and strongly oscillates and its behavior is known to cause many industrial problems. In this study, a jet structure and an emitted noise from an underexpanded jet radially discharged from a circular slit nozzle, which consists of two circular tubes, are examined experimentally for different nozzle pressure ratios and different diameters of tube, and the experimental results are compared with those of a two dimensional jet issuing from a rectangular nozzle. As a result, multiple ring-shaped shocks are visualized in the radial underexpanded jet, and the sound source of noise measured is found to be in the vicinity of the end of the second cell. Furthermore, collapse of the cellular structure of radial jet occurs upstream in comparison with the case of rectangular jet and the length of second cell is shown to be one of the most important parameter of a frequency of the emitted screech tone.
Selected from various eigenmodes of blading, nodal diameter κ= 0 and κ= 1 are both related to shaft torsional and/or axial vibration and shaft bending vibrations respectively. In order to avoid the possibility of 2f (f=power system frequency) from torsional vibration resonance, ISO regulates the final calculation results considering the combination betweenκ= 0 blade and torsional shaft vibration. The combination between κ= 1 blade and shaft bending vibration may become increasingly problematic as industry moves toward blade upsizing. This study explains a global method for blade-shaft coupled vibration analysis governing bothκ= 0 and κ= 1 in a systematic manner. According to our methods, the uncoupled blade vibration is first calculated for eigenvalue solutions using a general-purpose code of 3D-FEM (Finite Element Method), such as Nastran®. This solution provides a simplified blade model based on the concept of mode synthesis. Based on this blade model of our small scale test rotor, coupled vibration analysis was completed using the following two methods: -1) A simplified model of a shaft system was also prepared in a similar manner, and the two reduced models were then combined to understand the blade-shaft coupling system. 2) A 1D-FEM code specialized for shaft vibration analysis, defined as only beam elements, was connected with the prepared blade model to analyze the coupling effect. - These two methods provide numerical solutions that are approximate and within practical accuracy. As a result, it is a suitable alternative when a 3D-FullFEM evaluation is not possible on actual machines like large scale turbine generator sets.
A planetary gear train (PGT) is one of the most important components in the hybrid and electric vehicles owing to its high torque-to-weight ratio, light weight, and compactness. But transmission mechanism is still unclear due to structural complexity. Planet gears make PGT complex because of its motion (simultaneous rotation and revolution) and different contact ratio, or meshing stiffness between internal meshing (ring-planet) and external meshing (sun-planet). Although many experimental studies about PGT’s steady condition had been conducted all over the world, no studies have proved motion of planet gear experimentally. In this paper, planet gear instant center of rotation (ICR) is found out based on its velocity distribution and it was proved with direct motion observation on planet gear motion by high speed monitoring. ICR is expected to be effective to estimate meshing transmission errors (MTE) with its feature like light lever. MTEs in a PGT were also discussed based on the fluctuation of trace of ICR, or centrode.
A novel two-limb six-degrees-of-freedom (dof) parallel robot redundantly driven by eight actuators is proposed. The proposed robot was named Atarigi Carrier or ATARIGI for short. An atarigi is a long wooden pestle, an instrument used in Japanese cooking. A chef holds an atarigi with his two hands and grinds sesame and miso paste in a large mortar bowl. The precessional motion of the robot is similar to that of a Japanese chef using an atarigi. The mechanism of ATARIGI has a two-layer structure in which the eight-dof actuators control six-dof hand via seven-dof internal mechanism. The first part of the hierarchy from the eight-dof actuators to the seven-dof internal mechanism has actuation redundancy, and the second part of the hierarchy from the seven-dof internal mechanism to the 6-dof hand has kinematic redundancy. ATARIGI is a novel parallel mechanism which simultaneously has kinematic redundancy and actuation redundancy. The kinematic redundancy contributes to singularity avoidance, while the actuation redundancy contributes to backlash removal by acting on the internal forces of the mechanism. These redundancies enable the proposed parallel robot to have a large workspace by avoiding the singularity and high accuracy by removing the backlashes. Closed-form solutions for forward and inverse displacement analysis, and forward and inverse kinetostatic analysis were derived. The derived solution was implemented using MATLAB and Mathematica, and the validity was verified by numerical calculations.
Sound masking is a method that used for protecting speech privacy of conversation at public open space such as a pharmacy or a bank window. In a conventional masking, a masking sound is used to cover contents of conversation. This masking sound which is generated from a loudspeaker allow a third party not to understand what is said, but there is a problem that the sound level is increased because of a masking sound. Against this problem, we proposed Low-noise sound masking method using active noise control (ANC). The approach of this method is to make spectrum of phonemes flat by control sound. It is difficult to recognize phonemes that are processed by this method because the major factor determining the phonemes in speech recognition is the relative relationship of the peaks of its spectrum. In this paper, the sound attenuation performance of the proposed method is validated by control experiments in an anechoic chamber. Moreover, a listening experiment is carried out to investigate the sound masking performance. The result show that comparing with the conventional sound masking method, the proposed method can achieve the sound masking effect with a smaller sound pressure level.
This paper presents a dynamic stability analysis of a plate supported by air pressure and experiments conducted using one and two supply slits. In the analysis, the steady-state such as flow distribution of the air supplied from the slits, a floating gap of the plate, pressure and air density in the gap under the plate are calculated by a floating analysis (steady-state analysis) based on the theory of two-dimensional leakage-flow. Then, unstable condition of a self-excited vibration of the plate is calculated by the dynamic stability analysis (unsteady-state analysis) when the plate vibrates around the steady-state. The basic equation of leakage-flow considers the effect of air compressibility. The equation of continuous air flow in the chamber includes the effect of air compressibility. The vibration characteristics and unstable condition of the self-excited vibration of the plate are calculated using the characteristic equation for the system. The experimental setup comprised a plate supported by the pressure of air supplied from one or two supply slits on the upper surface of the chamber, where the vibration characteristics are examined. The occurrence of the self-excited vibration is clarified by comparing the analysis and experiments. Finally, the local work done by the unsteady fluid force acting on the plate (bottom surface) is presented, and the instability mechanism of the self-excited vibration is discussed.
This research proposes a new image visualization method of bulldozer and surrounding dangerous area to operator. Bulldozers are operated on uneven terrain which contains dangerous slope or obstacle. The objective of this research is to visualize the pose of bulldozer and surrounding terrain shape and to emphasis existence of dangerous terrain shape. Our proposed method consists of following three parts. First part is machine pose visualization. Machine pose is measured by on-board IMU and GNSS. The 3DCG model pose is changed according to measurement rotation and translation motion. Second part is terrain shape visualization. Terrain shape is measured by on-board laser radar and change projection plane shape. Third part is danger area detection and visualization. Danger area is detected by point density and incline of ground shape mesh. An experiment was conducted with a real bulldozer. The image which was generated by the proposed method was compared to what generated by the conventional method. Visibility of pose change of bulldozer and surrounding danger environment was improved.
This article presents the algorithm for real-time distant 3D tracking by RobotEye RE05, the 3D laser scanner using gimbal mirror mechanism. It is comprised of real-time extraction of moving objects by 3D background subtraction for 3D point cloud scanned by the scanner, tracking of a moving object, and scanning densely around it. For recognizing moving objects, high-speed background subtraction and clustering algorithms for point cloud data are developed. In the background subtraction, background data which contains no moving object is measured, and the distance map is generated, which contains distances of points in sections divided into every small azimuth and elevation angles. The map is adjusted to reduce noises caused by the measurement error and noises around object edges. Then, current data is measured which contains data of moving objects and the distance map is generated. If the distance in the map of current data is nearer than background data, the point is remained as the foreground data. Before clustering, edge noises in the foreground data are removed by the filter newly developed based on statistical outlier removal. This filter is improved by adjusting the number of neighbor points used for searching and mean distance with the neighbor points using the distance of each point. In the clustering, intervals of azimuth, elevation angles and distances of each point are considered to obtain proper results in any distances. Finally, the position and the width of moving objects are computed from the clusters. For following and scanning the moving object, the new function named Tracking Scan was developed, which is new scan motion of RobotEye RE05 for tracking application. This scanner can scan appointed range in azimuth 360deg and elevation ±35deg by desired density. Moreover, the range and density can be updated during scan in Tracking Scan. At last, the experiment result of moving person tracking is described.
This paper proposes an identification method for the excitation force of a rigid body vibration source. This is done by constructing a characteristic matrix without a force signal during a preliminary excitation test. In mechanical products, if an abnormal vibration such as excessive vibration occurs after machine assembly, reworking is necessary to rectify the problem. This extends of the development period and increases cost. Therefore, quantitative vibration prediction at the design state is important. In order to predict quantitative vibration, it is necessary to understand the excitation force of the vibration source. The proposed method of excitation force does not use a force signal during the preliminary excitation test. Therefore, there is no restriction on the vibration method in the preliminary vibration test, and it solves the problem in the case where the excitation point cannot be secured. In this method, the modal mass is calculated using a rigid body mode vector of 6 degrees of freedom (acquired during the preliminary vibration test) and the mass of the vibration source. Then, after determining the mass normalized mode vector from the calculated modal mass, the characteristic matrix of the rigid body vibration source is identified. Finally, the excitation force when the machine is running is identified from the equation of motion in the frequency domain. As a result of testing the verify the validity of the method, the proposed method can identify the excitation with the same precision as when using the force signal and has demonstrated its usefulness.
The current increase in health awareness has led to greater attention to exercise. However, the growing number of competitors in various sports has caused a concomitant increase in the number of injuries during matches. After an injury, an immediate return to competition is difficult. A related problem is the shortage of athletic trainers. Strong teams such as professional, corporate, and university teams retain athletic trainers who can create unified plans spanning from injury to recovery, including subsequent recurrence prevention. However, only a fraction of teams can maintain such support staff, and so measures to accommodate the increase in the competitive population in various sports are beginning to fall increasingly behind. Competitive sports are supported by the continued influx of amateur athletes, and so when members quit due to injury or injury aggravation, it is undesirable both for the individual and for the sport as a whole. Thus, there is a need to develop rehabilitation devices that can provide an environment in which the user can safely be rehabilitated while determining his or her own state of recovery even if no athletic trainer is available. Conventional rehabilitation devices have emphasized recovery of cardiopulmonary function or the function of specific joints, with little to no development of devices aiming for an early return to competition. Against this background, the objective of this study is to design and develop a rehabilitation device that prevents reduced range of motion in joints and also prevents decreased muscle strength and proprioception in athletic movements during the rehabilitation period. The device works by recreating a running action close to that used in daily life as a common movement in numerous sports. We demonstrate that the use of a planar linkage with one degree of freedom is effective in the design of such a device. This rehabilitation device uses a planar six-bar linkage to simulate the path of the legs during running. Furthermore, we investigate a design with a form that uses a slider crank mechanism with the motion of the arms during running as an input to create the proprioceptive sensation of a motion that includes not only the legs but the arms in a linked operation. We aim to develop a device that, by being used while seated in a saddle and employing adjustable links, can track a range of different leg pathways instead of being designed for a specific individual. Using a prototype device, we verify the reproduction of the running motion as well as the amounts of muscle activity when using the apparatus in order to investigate its utility as a rehabilitation device.
The surface of phenolic composite material was continuously observed through borosilicate glass (BK7) during friction to verify the tribo-reduction of copper oxide (CuO) taking place at the interface. Two types of pad samples were slid against a rotating BK7 glass disk. These pad samples were made up of selected components, one of which contained CuO as an additive, from a commercial brake pad. During rubbing, dark wear tracks appeared on both pads, where debris generation and its flow were so frequent that the temporal change of these tracks was extremely fast. Using laser microscope after the friction test, small metallic spots were clearly visible on the dark wear tracks of the pad that had contained CuO. The EPMA analysis of these spots showed that the main component was Cu itself. This means that CuO was reduced to Cu, i.e. tribo-reduction took place on the dark wear tracks. Pad friction surface was also observed during friction in relatively dimmed light conditions. The orange luminescence from some spots on the dark wear tracks appeared. The orange color suggested that the temperature of these spots reached significantly high. Heating experiments evidenced that CuO powder, when mixed with phenolic resin powder, was reduced to Cu at 300 °C or higher associated with the weight decrease of mixed powder. Therefore, the luminescence at the surface indicated that the temperature was high enough to cause the degradation of phenolic resin, which promoted the reduction of CuO. It was thus confirmed from the chemical composition and luminescence color that CuO in phenolic composite material was reduced to copper during friction.
In this study, the automated process planning system for end-milling operation is realized. This study considers to minimize the number of times of tool change and to determine the appropriate machining sequence in the process planning. In our previous process planning system, the machining sequence is calculated geometrically, based on the Total Removal Volume (TRV) and the machining regions split from TRV. However, it remains difficulty to determine the best machining sequence from the large number of the calculated machining sequences. The previous process planning systems also do not consider machining conditions in the determination of the appropriate machining sequence. First, our new process planning system generates the association chart of machining regions, which represents the geometrical constraints to determine machining sequence. According to the association chart, the candidates can be selected from the enormous candidates of the machining sequence. Subsequently, our new process planning system determines the best machining sequence under considering the machining conditions. The best machining sequence is determined to minimize the number of times of tool change. A case study was conducted to show the effectiveness of our new proposed process planning system, and the machining sequence was automatically determined based on the geometrical constraints considered in process planning and the machining conditions considered in operation planning.
Under certain weather conditions, avalanches can occur because of snow cover on a steep slope. Such avalanches can reach snow fences that are arranged as countermeasures. Furthermore, traffic is completely blocked when fences collapse and snow falls on a road. Therefore, prediction of avalanche occurrence is important, but such predictions are considered difficult. To resolve this difficulty, this study assessed measurement of the danger degree by measuring the risk to the avalanche fence at the time of snowfall and falling rock according to changes in the load and the impact of voltage proportional to the avalanche barrier deformation. This measurement system has fixed sensors attached with mounting brackets to a dedicated avalanche prevention measurement fence. It measures the pressure and vibration measurement of the snowfall at the time of avalanche or rock fall occurrence at the main structure of the fence. Furthermore, this fence made of lumber from thinned timber is useful as a defensive barrier countermeasure against avalanches and falling rock. It is designed to withstand a snow load of 3–5 [t/m2] during an avalanche.
Ultrasonic pulse reflection method was employed for in situ estimation of several forces including moment acting on dual race type hub-bearing operating with low speed. The estimation of these forces was performed through the observation of echo height h which is reflected from the interface of outer ring/ball and varied with contact condition of lubrication surface. The echo ratio H (=h/h0 : h0 is the echo height in dry condition) is decreased at the ball position in loading side (dense contact) and is increased in unloading side (sparse contact). For instance, the reflection echo height h in upper side of hub bearing is decreased, since the supporting load of the ball in there increases, when only the load (vertical force) Fz is applied to the bearing through the tire. Meanwhile, the echo height in lower side of the bearing is increased up to the quantity same as the variation mentioned above in contrast to upper side, because the supporting load of the ball in lower side is decreased. The behavior of such contrastive H appears, when the axial force, the moment around x-axis horizontal to the roadbed and the moment around z-axis vertical to the roadbed are applied to bearing. Estimation of the load and the axial force becomes possible from the mean value of the echo ratio change that those contrastive influences in H are canceled. Moreover, the estimation of the moment around x or z-axis is enabled from the differences between such mean value and echo ratio change of each ball. Then, the potential that can individually measure the several forces and moments generated by steering was clarified, even if the condition that they were superimposed simultaneously.
It has been long since the technology for human space flight system was established. In order to realize challenging manned space missions, further improvements in the system reliability and crew safety are essential. Comprehensive design and operation considerations based on the quantitative crew safety analysis are key issues. Crew injury risk prediction method due to the transient dynamic load such as the excessive water landing speed, the explosion overpressure, and the off-nominal acceleration of the launch abort system (LAS) are developed and investigated in this study. In the early design stages, parametric injury risk analysis should be carried out. For this purpose, an anthropomorphic test device (ATD) model based on the multi-body dynamics is suitable to cover the wide range of conditions. In addition, an human finite element model is employed for more detailed crew injury risk analysis. Although there have been comprehensive research efforts in the automotive safety fields for many years, further research efforts are needed for the crew safety of human space flight since a wider range of the magnitude and the direction of the impact load should be considered. This paper deals with the human injuries evaluation using finite element model. The results are compared with those using Hybrid-III and safety margin is evaluated in view of NASA injury criteria to extract highly damaged body region in both models. The validity of brain injury criteria BrIC is investigated by using mechanical properties in brain and new risk curve for BrIC suitable for LAS environment is finally proposed.
This study systematically analyzed life cycle CO2 (LCCO2) emissions of a comprehensive set of mass-produced 2,000 cc class sedan-type vehicles, using a hybrid life cycle inventory approach. Gasoline and diesel internal combustion engine vehicles (ICEVs), hybrid electric vehicle (HEV) as well as battery electric vehicle (BEV) and fuel cell vehicle (FCV) were investigated, considering (i) the current BEV market trends, (ii) Japan's energy mix (the average for 2012–2014), and (iii) the use of the HVAC system. The results show that the annual average increment of CO2 emissions in use phase by HVAC system in Japan (assumed annual mean temperature of 15°C) was presumed to be evenly 9% regardless of vehicle types, although further detail analysis is required. The CO2 emissions in use phase of BEV were higher than those of HEV and FCV (applied hydrogen produced by steam reforming of LPG (on-site)) due to thermal power dominant electricity generation mix in Japan in recent years. As a consequence of high CO2 emissions from power supply and battery production, the LCCO2 emissions of BEV equipped with 75 kWh battery were higher than those of HEV, FCV (on-site), and conventional ICEV (diesel). By reducing the battery capacity to 40 kWh or less, the LCCO2 emissions of BEV become lower than those of ICEVs and FCV (on-site), making BEV a competitive alternative. However, it is difficult that BEV mitigates both LCCO2 emissions and driver's range anxiety. In conclusion, HEV shows the competitive performance in terms of LCCO2 emissions with long driving range in Japan.