According to a speedup of the Shinkansen, it is increasing to feel the passage of the vertical curve. However, the actual situation is not clarified because it is hardly investigated the ride comfort about the vertical curve passage until now. Therefore, two kinds of subject experiments by the high-speed train were carried out to obtain the knowledge of the ride comfort in the vertical curve passage, and the following results were provided. It was suggested that not only the acceleration but also the jerk influenced the perception of the vertical curve. In the same condition as the passengers of the operating train, the perception ratios of the vertical curve were about 60 % at maximum speed 275 km/h, and about 70 % at that 320 km/h. In the vibration ride comfort of including the vertical curve, the railroad employees were strictly evaluated than general subjects, and young group subjects were strictly estimated than elder ones.

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This paper presents the laboratory experimental results in relation to tangent force between a wheel and a rail under different environmental conditions. In the experiments, we used two types of cylindrical test specimens (with / without fine unevenness on contact surface) assuming actual wheels, and investigated the relation of tangent force to the cases of with / without fine unevenness on contact surface under the conditions of different environmental temperature and relative humidity. Consequently, under the conditions of without fine unevenness on the contact surface of a test specimen, it showed that there is a tendency in the tangent force which turned out low whence relative humidity is over 60%, regardless of environmental temperature. However, on the conditions which have fine unevenness on the contact surface of a test specimen, we could not observe the effect of environmental temperature and relative humidity on the tangent force. In addition, running stability analysis of railway vehicle was carried out for the cases of with / without fine unevenness on wheel tread of railway vehicle under the condition of different relative humidity. As a result, it was shown that the critical hunting velocity under the condition of without fine unevenness becomes low while increasing relative humidity.

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We experimentally investigated the dynamics of railway vehicles, which derail from the top surface of a rail onto the ground, using full-scale models of one bogie and a half carbody on the large shaking test facility. The dynamics of derailing vehicle were as follows: 1) After a wheel leaved the top surface of a rail, the wheel firstly landed on the ground. 2) Then, the gear case next to the wheel hit the inner side surface of the rail. 3) Finally, the bogie slightly yawed and the L-shaped guide under the axlebox at the diagonal position of the gear case hit the outer side surface of the opposite rail. During the derailment, the maximum piston velocity of the lateral damper was about 0.6 m/s and the maximum action force of the L-shaped guide was about 60 kN. In addition, we numerically simulated the derailment of wheels using 3-DOF model. The numerical results were consistent with the experimental result about the falling time of wheels. Finally, we showed the relationship between wheel deviation speed and landing position when the wheel derails from rail surface onto real concrete slab surface.

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To minimize the risk of fatalities in the event of earthquakes, it is extremely important to prevent the derailed vehicle from deviating from the track as well as to prevent the vehicle from derailment. Authors have developed a post derailment stopper (hereinafter referred to as, “stopper”), which attaches to a bogie frame and prevents derailed vehicles from veering of the track. For the development of the stopper and evaluation of its efficacy, we conducted running tests under derailment conditions using real bogies and tracks. Based on the results of the running tests, we have developed a 15DOF vehicle dynamics model in order to discuss the motion of the bogie in the derailment condition. In this model, focusing on the analysis of the motion of the bogie and the stopper, vertical wheel displacements which were measured at the running tests are used as input data and non-linear characteristics observed at the running tests are considered. In this paper, we analyze the motion of the bogie and efficacy of the stopper with this model and the test results.

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In this investigation, curving performance for low-floor light rail vehicles (LRV) with friction controls on wheel/rail interface is discussed. To this end, a creep force model subjected to friction modifiers is developed by introducing an equivalent shear modulus of rigidity. Good agreements in the creep force characteristics are obtained between the proposed model and experiment. It is shown with the proposed creep force model that use of friction modifiers on an inner rail is effective for reducing lateral contact forces of LRV with independently rotating wheels.

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Three-dimensional motion analysis is necessary to describe the complex tire behavior on soft ground due to the deformation of the tire and the landform of the soft ground such as the ground heaving in the vicinity of the tire side edge. We developed the three-dimensional interactive model for the performance of the tire on soft ground that were composed of the distributed lumped mass-spring model as the tire, Discrete Element (DE) model as soft ground. In the present study, we have extended the previous model by dividing the soft ground into the upper and the lower soft ground, and by adding the lug to the tire with considering the contact geometry with soft ground. Numerical simulations of the tire behavior on soft ground have been carried out under several conditions using the proposed model. The numerical results showed that the three-dimensional motion analysis of the tire behavior on soft ground could be conducted, and that the proposed model could be validated through comparison with previous experimental results on the tractive performance and the cornering performance of the tire on soft ground.

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This paper proposes SSM(Sensor Steering Mechanism) for a lateral guided vehicle with an articulated body which has an arbitrary position of articulation joint. The last paper shows the SSM for an articulated vehicle with a bending joint located at the center of its wheel base. The articulated robotic vehicle with SSM is demonstrated an accurate line following at low speed and a drift cornering at high speed moving. This paper discuses the SSM for the arbitrary position of articulated joint and the simple relation is derived for the lateral guided method for the articulated vehicle. In order to demonstrated the advantage of this method, an experimental vehicle is developed and tested on the evaluation course which is used previous papers. Dynamical simulations of experimental vehicle are preformed and the data is compared with the experimental data. These results demonstrate that a SSM for articulated vehicles achieve at high speeds and maintain stability on a test course.

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Eco-driving is a driving mode through driver behaviors mainly about accelerator pedal operations, including smooth acceleration at start, preservation of steady speed, and active uses of engine brake, and proposed for reduction of vehicle CO₂ discharges. In this paper, driving experiments by subjects were conducted in the modes of normal driving, eco-driving, and eco-driving with eco-indicator in virtue of a universal driving simulator (DS). In the experiments, signals of surface electromyography (sEMG) of leg muscles of driver were measured to clarify the degree of muscle fatigue, and effect of mental workload of driver was also comparatively analyzed by a subjectivity evaluation of NASA-TLX method in the different driving modes. The studies suggested that the fuel economies can be improved by the eco-driving mode, which requires more muscular activities of leg for accelerator pedal operations than the normal driving. However, the muscular activities of leg can be decelerated by using the eco-indicator during eco-driving. Moreover, the evaluation results about mental workload shown that drivers always tend to feel mental workload for achieving target values of eco-indicator during the eco-driving.

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This study examines a collision avoidance system for motorcycles by automated steering control. The Model Predictive Control (MPC) is applied to the automated steering control with constraints on the motorcycle rolling motion by considering the rider's body movement in emergency avoidance. Two types of MPC controllers are designed and evaluated by the simple computer simulation of obstacle avoidance. One is a controller with a constraint on the rolling angle. The other is a controller with a constraint on the roll rate. Both controllers improve obstacle avoidance performance in comparison with the Liner Quadratic (LQ) controllers as conventional control theory. The MPC controller with the constraint on the roll rate decreases the roll rate under the permissible rolling angle. The controller with constraints on not only the roll rate but also the steering torque suppresses the large steering torque input. The improved avoidance performance by the MPC controller is observed at other vehicle velocities.

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This paper focuses on the effectiveness of maintenance in fault-tolerant multi-robot systems. The multi-robot system intended in this paper is completely parallel. That is to say, the system is enabled to work as long as one robot works. For this system, it is required to ensure fault tolerance and keep high performance taking robot failure and maintenance, such as prevention and correction of robots, into account. Therefore, we propose an optimal maintenance strategy on the basis of reliability engineering. This strategy enables robots to undergo preventive maintenance at an optimal interval and corrective maintenance each time they fail. Consequently, the number of robots undergoing maintenance or its effect on the system performance is minimized. Through simulation experiments, the effectiveness of the optimal maintenance strategy for the higher system performance is shown. In addition, the influence of robots undergoing maintenance on the system performance is mathematically and experimentally discussed on the basis of the number of robots used and maintenance strategies.

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Rail grinding as a part of maintenance of railway track is executed for the purpose of reducing damage on rails and environmental noise etc. When executing grinding to remove head checks at rail gauge corner in curve sections, the grinding-rail profile and grinding range should be carefully considered so as not to induce flange climb derailment. The authors have implemented numerical simulation of a vehicle running on ground rails in curve sections at a low speed, and examined running safety against flange climbing characterized by such factors as the wheel-load imbalance and curve radii. Based on the simulation results, a new indicator, which is concerned with the vertical displacement and the contact angle of a wheel on high rail, is proposed in order to evaluate the tolerable quantity to limits for securing safety against flange climb derailment. The indicator and the further consideration of the rail profile derive an acceptable condition of the grinding range of the rail profile and the curve radius in tracks.

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In this paper, we have proposed wave algorithm for manipulating energy transfer between globally coupled two harmonic oscillators with internal resonance by intermittent perfect elastic impacts at balanced point. When the temporal interval of the impacts, Δt, is the same of the periodic time, 2π, the coupled oscillators exchange their energies slowly and periodically. Its periodicity depends on the ratio between the mass of the oscillators. By skipping an impact, we can reverse the direction of energy flow. And by skipping an impact in every 2nπ period, the system shows 4nπ-periodic recurrence phenomena. By controlling the intermittent of the impacts, we can keep maximizing or minimizing the amplitude of one certain oscillator. We can analytically explain these phenomena from the combinations of unitary operators under wave algorithm. Moreover, under the periodic 2π impacts, the system shows periodic recurrence phenomena, only when the rational ratio between the mass of two coupled oscillators, γ =1, 1/3 or 3; otherwise, it shows strictly ergodic behavior in velocity space.

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In this paper, focusing on the coupled vibration of light weight vehicle engine and frame, the efficient method to reduce the vibration is discussed. First, target coupling vibration is explained by experimental data. And transfer force identification which transmits from the engine to the frame through the engine mount is carried out using dynamic stiffness method. In order to explain how the engine and the frame are coupling, the coupling index is introduced. The index is defined by inner products of the identified force and the frame FRF. Finally, the method to reduce the coupling index by adjusting the engine mount angle is proposed. The optimal adjustment angle is predicted and modifying the angle in experiment, it is shown that the adjustment method can reduce the coupling index and coupled vibration.

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It is known that, under appropriate conditions, the amplitude of vibration of some blades in the mistuned bladed disk system become large compared to what would be predicted by an analysis of the perfectly tuned system. In this paper, the rms responses of the mistuned bladed disk system subjected to random excitation with the spatial decorrelation and correlations are investigated. The effect of the correlation of the random excitation on the rms response is discussed. It is shown that the rms response of the mistuned system subjected to the spatially-uncorrelated random excitation is almost the same as that of the tuned system. In the case the random excitation is spatially-correlated, it is noted that the rms responses of the mistuned system is much larger than those of the tuned system and that the mistune arrangements effect on the rms responses. With the spatial correlation, it is also noted that the particular mode shapes play an important role in the rms response.

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This paper proposes a new model predictive PID control method for the traction control of EV (electric vehicle). The method aims to improve the vehicle dynamics performance and the stability of EV by controlling the tire slip rate. In the proposed method, the PID controller gains are derived by off-line calculation from the optimal control input based on the model predictive control (MPC) algorithm. Numerical simulation results demonstrate the effectiveness of the proposed method.

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The attitude sensor mounted on unmanned systems is required high accuracy attitude under the dynamic acceleration environment for the autonomous attitude control. In order to estimate attitude by using a quaternion based on extended Kalman filter (EKF) , the attitude sensor detects a direction of the gravity by using a tri-axis accelerometer. However, accelerometers are usually sensitive to both the gravity and dynamic accelerations. In this paper, the dynamic accelerations are dealt with explicitly, and two types of algorithms are proposed. In the first approach, measured accelerations are filtered, and divided into the gravity and dynamic accelerations. Using only the gravity, EKF estimates high accuracy of attitude. This algorithm can be realized with relatively small amount of computation, and have a good effect under the short dynamic acceleration environment. The second approach demonstrates adequate performance with EKF which includes the dynamical model of accelerations. This paper shows a critical comparison of attitude estimation algorithms under the dynamic acceleration environment for the autonomous control of unmanned systems.

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The falls of the elderly are becoming a serious problem, not only medically but also socially. The several study reported recovery movement of the lower extremity during slipping, but the recovery movement of the trunk research reported a few. The purpose of this study was to investigate the balance recovery mechanisms of the separated trunk during slipping with gait. The trunk segment was divided by the upper trunk, the lower trunk and pelvis. A kinematic and kinetic data during slipping were measured by 3D motion analysis system and force platform. Center of mass of the upper body, joint angles and joint moments were calculated by inverse-dynamics method. The results showed that the slip recovery movement needed strongly muscle activation of the upper trunk rather than the lower trunk. The fall prevention requires enough flexor torque of lower trunk for maintaining position between upper trunk and lower trunk. In additionally, trunk constraints group were needed extensional torque for maintaining position lower trunk in the late slip time.

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Methods of underground installation of certain geophysical sensors such as seismometers and heat flow sensors are required for future lunar and planetary exploration. On the Moon, installing such units at depths below several tens of centimeters allows them to survive overnight without any thermally shielded mechanism. Conversely, methods of driving piles into the regolith would help robots operate, because it is very difficult to obtain sufficient reaction force in the regolith, which is powdery and soft. In 2008, we proposed a new mechanism known as a “Self-Turning Screw Mechanism” (STSM), which uses the reactive torque of a wheel to drill into the regolith. In this paper, we report the concept of the STSM, the design of our recent prototype and the result of the experiment. The length, diameter, and weight of the prototype are 364.6 mm, 80 mm, and about 2.5 kg, respectively. In the latest test, the prototype was able to drill down to 669 mm into the fly ash sand which simulates the lunar regolith. In addition, the prototype successfully drove backward to eject itself from the fly ash. These results proved the applicability of the mechanism to autonomous drilling systems in future landing missions.

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Shuttlecock used in a badminton match is light in mass (around 5 grams), and is strongly influenced by air drag force. For professional badminton players, the highest initial speed of the shuttlecock exceeds 84m/s (300km/hr), which is the fastest speed for a ball, racket or projectile sports. The shuttlecocks are of two kinds: one of feather and one that is a synthetic shuttlecock. A feather shuttlecock is constructed of 16 goose feathers with a cork base mostly. Also, a synthetic shuttlecock is made of plastic or nylon with a cork. Both shuttlecocks are light and of a complicated shape, therefore, it is extremely difficult for the shuttlecock to be launched at speeds of more than 42m/s without breaking the feather, even if the newest mechanical technology is used. In this study, new insertion equipment and the motion control system were proposed, and an exercise machine for badminton, used to project the shuttlecock at high speeds (over 42m/s), has been developed. The mechanism of the shuttlecock launcher in this machine was achieved using the friction force between two turn rollers and the shuttlecock. The results of the launcher experiments using the badminton machine show that the machine can project the feather shuttlecock at the maximum flight distance of about 11.5m, with a standard error of about 0.32m and the highest initial speeds being 52.8m/s. In the case of the synthetic shuttlecock, this machine achieved the maximum flight distance of about 9.7m, and the highest speeds being 47.8m/s.

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Since the number of trans-femoral amputees has increased by industrial or traffic accidents in modern society, the demand for a prosthetic limb has also increased year after year. In this case, those amputees must regain moving pattern by refined efficient gait training using load conditions on a prosthetic limb as quantitative evaluation indices. However, conventional prosthetic gait training systems cannot measure long continuous walking motions under a wide range of environmental conditions. In this paper, a novel six-axis force/moment sensor, which is attached to a prosthetic limb for the unrestrained gait measurement, is developed. As a result of applying structural optimization techniques using response surface method and desirability function to this sensor by finite element analysis, optimum design variables to make the effect of interference components much smaller are obtained. Finally, characteristics test using the production model by applying optimum design variables is performed and the effectiveness of the developed sensor is validated.

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Many methods for physical medicine and rehabilitation strategies have been developed for physically disabled people. Most of them have been determined by physical therapists based on anatomical and physiological assessment of the subject. With application of robot technology which allows smooth achievement of complex trajectories, and with loading or assisting designated muscles in an accurate manner, a better rehabilitation strategy can be developed. In this paper, we propose a new method to design the motion trajectory of lower limbs and the applied forces acting on the foot. In order to improve the rehabilitation effect in full consideration of biomechanical stability of the trajectory and musculo-skeletal model of each subject, we have applied genetic algorithm to search the parameters of spline curves for the trajectory and the applied force acting on subject's foot. The usefulness of the proposed method is confirmed through simulation results and the comparison with a conventional training trajectory.

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A hybrid optimization method using simulated annealing (SA) and a genetic algorithm (GA) developed in a previous study is improved in order to achieve high computational performance. The previous method, in which the genetic operations for generating initial search solutions of the next generation are introduced into the computation process of multi-point SA, can efficiently and globally compute Pareto-optimal solutions, as compared to SA using a re-annealing method. However, a large number of Pareto-optimal solutions exceeding the acceptable amount of computer memory may be obtained. In the proposed method, in order to effectively store Pareto-optimal solutions in computer memory, all obtained solutions are classified according to topology type, and those that should be stored are selected from each topology group. In addition, selection methods based on four criteria are newly proposed in order to improve the convergence of solutions and to maintain their diversity. The proposed SA/GA hybrid algorithm for simultaneous optimization of the topology and geometry of a two-dimensional framed structure is applied to a two-objective optimization problem of minimizing the total weight and maximizing the first natural frequency under displacement and stress constraints. The validity of the proposed methods is confirmed through performance evaluation based on the Wilcoxon rank-sum test.

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Compared with the machining process for mass production, the machining processes such as deburring are performed on a wide variety of products in various quantities by workers on a piece-by-piece basis. Accordingly, the accuracy of the product depends on the worker's skill. The partial over grinding or machining mistakes caused by these factors often result in useless products and wasted materials. The aim of this research is to develop a finish machining support system that is possible without machining mistakes. The machining is supported by using the haptic device and controlled by the bilateral control system. Here, we propose a control method based on a machining model made up of several components, including tool speed, feed speed of the tool and others, in order to control the robots under conditions in which it is possible to achieve highly accurate machining surfaces. The motion of a slave robot that requires precise control is controlled automatically, and the worker is given the force calculated by this control method. The effectiveness of this system is shown in a machining experiment.

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This paper studies the static and dynamic characteristics of tilting-pad journal bearings (TPJBs) with the load directions different from either of the two typical load directions of LOP (Load On Pad) and LBP (Load Between Pads). Theoretical results show that the effects of the load direction on the static and dynamic characteristics are found in the range of low Sommerfeld number S and increase with the decrease of S. The cross-coupling terms of spring and damping coefficients are no longer zero if the load direction is different from LOP and LBP, but the cross-coupling spring coefficients are equal, which indicates that the non-zero cross-coupling terms of the spring coefficients do not cause the self-excited vibration.

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The activation mechanism of motorcycle weave mode is clarified within the framework of the energy flow method, which calculates energy flow of mechanical forces in each motion. It is demonstrated that only a few mechanical forces affect the stability of the weave mode from among a total of about 40 mechanical forces. The activation of the lateral, yawing and rolling motions destabilize the weave mode, while activation of the steering motion stabilizes the weave mode. A detailed investigation of the energy flow of the steering motion reveals that the steering motion plays an important role in clarifying the characteristics of the weave mode. As activation of the steering motion progresses the phase of the front tire side force, and the weave mode is consequently stabilized. This paper provides a design guide for stabilizing the weave mode and the wobble mode compatibility.

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The carbonaceous hard coating such as Diamond-Like Carbon is one of the materials to prevent surface damage. It was reported that Carbon Nitride (CNx) coating showed superlow friction coefficient when it slid against a Si₃N₄ ball in N₂ environment. In the case of applying CNx coating for industrial fields, it is necessary to improve adhesion between CNx coating and substrate. In this study, we clarify the effect of interlayer to improve adhesion of CNx coating to WC substrate. 4 different kinds of interlayer materials were prepared. From the scratching test results, adhesion of using CrN and no interlayer was smallest. On the other hand, SiN, CN and DLC interlayers showed high adhesion. From the finite element analysis, interlayer thickness and Young's modulus did not affect to improve adhesion between CNx coating and WC substrate.

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The static characteristics of journal bearings with an axial groove under starved lubrication are studied theoretically and a lubrication condition map is newly proposed. This map is represented using the contour map of the eccentricity ratio with the Sommerfeld number S in the horizontal axis and the dimensionless oil flow rate Q_sup externally supplied in the vertical axis for the wide range of the operating conditions. It is found from the map that the eccentricity ratio increases with the decrease of Q_sup. This tendency is more marked for a higher Sommerfeld number. Journal center loci show that the attitude angle decreases with Q_sup. The degree of the starvation Λ and the oil supply rate Ψ are defined as the ratio of the dimensionless oil flow rate into the inlet of the oil film region to that obtained under the flooded lubrication condition and as the ratio of Q_sup to Q_sup^* obtained under flooded lubrication conditions, respectively. The degree of starvation Λ varies with Ψ and the value of Λ can be determined by setting the value of Ψ. These facts suggest that the static characteristics and Λ are theoretically predicted once the value of Q_sup or Ψ is determined.

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In general, grinding fluid is supplied from the supplying nozzle to the grinding wheel-workpiece contact zone during the surface grinding process. However, when the profile or curved surfaces need to be machined, the supply of the grinding fluid to the contact zone seems to be more difficult due to the fixed direction of the grinding fluid supplying nozzles. Therefore, the system which can supply the grinding fluid through the grinding wheel was developed and evaluated. In order to evaluate the effectiveness of this system, the maximum workpiece temperature on the backside of the grinding point using the thin wall workpiece was measured by an infrared radiation camera. The flow rate of grinding fluid and grinding parameters showed a significant effect on the temperature and the grinding performance. Moreover, the profile grinding of the turbine blade shape was successfully conducted.

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Robot welding using TIG welding process is often used to join thin metal plates because of the stability of arc compared with other arc welding processes. However, the tungsten electrode tip of the TIG welding torch is considerably consumed during the welding process due to the high temperature of the arc and the oxidation by surrounding air. As a result, the shape of the electrode tip changes and the arc becomes unstable. Accordingly, in order to realize stable welding, control of the tungsten electrode tip is important. Since the arc is essentially unstable, sometimes it becomes unstable by some factors. On the contrary, the laser beam has extraordinary stability and directivity because of the nature of the light beam. Therefore, stabilization and control of the unstable TIG arc by the laser beam was investigated. In this study, the feasibility of stabilization and control of welding arc by laser beam was studied using hybrid welding process combining TIG arc and low power YAG laser.

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