A large number of vibrations are applied to a railway vehicle while it is running, and the natural vibration phenomenon occurs when the frequency of the vibration approaches the natural frequency of the vehicle itself. It is a common phenomenon but it is also an issue to prevent it from occurring, and it is necessary to clarify each natural vibration mode of the vehicle. In this study, we performed a running experiment by using a railway roller rig. By PSD analysis of the vibration acceleration at each measurement point, it is clear where the natural vibration phenomenon occurs at lateral and we know the experimental value through running experiment. We also modeled horizontal 6 degrees of freedom of the roller rig model, calculated the natural frequency, and grasped the theoretical natural vibration mod by using numerical analysis software. By comparing the theoretical value and the experimental value, the natural vibration analysis method was established.

The Remote Tower (RT) /Digital Tower (DT) operation is a future air traffic control concept for airport tower. In the RT/DT system will provide a target tracking function as for supporting operation based on motion detection technique on the 360 degree panorama display. System needs to detect moving target from large size panorama pixel data by using image processing algorithm such as an optical flow. On the other hand, system has to process image data to detect target quickly to avoid delay. In this research, we tried to optimize the detection process to for improving detection update rate. We discuss about technique of target detection process to improve image processing speeding up.

Derailment at a turnout on railway often adversely affects operation. The existing turnout has a guard rail to prevent misguiding, but there is no guard to prevent derailment. In addition, in the large earthquake warning area, derailment guards are installed even in normal sections, but turnout sections are not installed. If it is possible to install a derailment guard in the turnout section, it is effective as an earthquake countermeasure and prevention of derailment during normal times. In this study, the authors investigated the feasibility of derailment guards in the turnout section. As the primary verification, physical verification was performed using a 127 mm gauge turnout.

For improving safety and work efficiency in payload transporting using an overhead crane without depending on the skill of the operator, we examined the payload sway suppression control technology to shorten a payload overshoot, which is a payload moving distance from stopping start, without a residual sway, which is a payload sway after a crane is stopped. We proposed a simulated repowering control which is simulated a repoweing operation by a skilled operator. In this method, a crane is driven deceleration and trapezoid wave motion after stopping start, and cancel the payload sway caused by the deceleration with the payload sway caused by the trapezoid wave motion. In order to apply this control to actual operation, we investigated the simulation which changed the pendulum length and the stopping start timing. As a result, we confirmed that the residual payload sway can be suppressed and the payload overshoot can be shortened than the conventional payload sway suppression control without depending on the pendulum length and the stopping start timing.

In our previous study, we developed the high-damping rubber mount of under-floor equipment and confirmed the reduction effect of flexural vibrations in a railway vehicle carbody by the developed rubber mount. The developed rubber mount is also expected to suppress the high-frequency vibration of the under-floor equipment itself. The aim of this report is to confirm the vibration isolation performance of the developed rubber mount against vibration transmitted from the under-floor equipment. Excitation tests using a Shinkansen type test vehicle were conducted by a vibration exciter installed on the under-floor equipment. The sine wave excitation test shows that the rubber mount reduces peak value in the acceleration power spectrum density of carbody floor corresponding to the excitation frequency. The random wave excitation test also confirmes that the vertical vibration of carbody floor is reduced over a wide frequency band.

To improve the ride comfort in railway vehicles, we have developed a new mounting structure for yaw dampers to reduce the flexural vibration of railway vehicle carbody. The new mounting structure of yaw dampers has a rotational axle with bearing units and restoring spring. One of the features is that yaw damper brackets attached to the carbody side can move in the longitudinal direction along the carbody. We developed the prototype device for a full-scale test vehicle and carried out the verification tests at the rolling stock testing plant of the Railway Technical Research Institute. The hunting stability test shows that the critical speed of a vehicle with the developed device is more than 250 km/h. The rolling test shows that the vertical vibration of carbody floor induced by the rotation of wheelsets with small mass imbalance is lower with the developed device compared to original structure.

In the development of an automobile, various testing systems with hardware-in-the-loop simulation (HILS) techniques are proposed. Tire-suspension HILS system was a hybrid method with vehicle dynamics analysis and bench test of the tire-suspension system. The accuracy of an actuator control of the testing machine is significant for this system. In this paper, we proposed the tire-suspension HILS system with new actuator control using inverse dynamics compensation via ‘simulation of feedback control system’ (IDCS). IDCS is a numerical method to obtain an approximate inverse dynamic via feedback control simulation, using only the forward dynamic model of the system. The multibody dynamics model of the testing machine was used as the forward dynamic model and the suspension behavior of the vehicle dynamics analysis was reproduced by the actuator in the testing machine.

In automobile engines, torque fluctuations caused by combustion cause large vibrations in power transmission. Also, vibration problems become prominent after a lock-up condition. Automatic transmission for cars has a damper built into the torque converter to suppress this vibration. In order to make it more difficult to transmit vibration, it is necessary to reduce the rigidity of the damper. A three-stage piecewise-linear spring is used to achieve this in space saving. However, subharmonic vibration of order 1/2 occurs near the switching point of the spring restoring force characteristics. In this study, the suppressive effect of the dynamic absorber against subharmonic vibration is examined from both experimental and theoretical analysis by using the basic model of the two-degree-of-freedom system. We discussed the effects of differences in the mass ratio, natural frequency and damping ratio of the dynamic absorber. As a result, it was found that the subharmonic vibration can be completely suppressed by using the dynamic absorber with a large mass. Also, the analysis results agreed well with experimental results.

In order to ensure a stability and safety of trains running on turnouts, gaps between a tongue rail and a stock rail should be as small as possible by a fixing force of a switching equipment. To check indirectly condition of the fixing force, an opening force at the toe of the turnout, which is proportional to the fixing force, is usually measured during periodical maintenance works of the switching equipment. However, the proportionality of the forces is known to be affected by some parameters such as the type of turnout, the friction between the tongue rails and the bed plates, and closure distance between the tongue rail and the stock rail. In this paper, the effect of rail closure distance against opening force is analyzed using a 2-D beam model of tongue rails which allows for calculation of bending displacement and forces. The results of analysis confirm that the proportional coefficient of the opening force to the fixing force is affected by a gap closure on an end side of a switch rod.

A pantograph is a device for collecting electric power from an overhead contact line and feeding to a traction circuit of rolling stocks. The pantograph receives aerodynamic force while a train is traveling. Since the aerodynamic force increases in proportion to the square of the flow velocity relative to the pantograph, the influence of the aerodynamic force becomes apparent in a high-speed train. When a high-speed train runs in a tunnel, the flow velocity relative to the pantograph becomes faster than that in an open section. The authors measured the flow velocity around a train model running in a tunnel using a rake of total pressure tubes. The measurement waveforms were distorted due to the influence of the frequency characteristic of the measurement system. The authors developed a method for restoring the distorted waveforms and applied it to the measured waveforms to obtain the flow velocity. Until now, detailed analysis has not been performed on the fluctuation values of the flow velocity obtained from the restored waveforms. In this report, the flow around the train model is analyzed by using the restored waveforms measured by rake of total pressure tubes and the following quantities are obtained; average flow velocity, standard deviation, turbulence intensity, displacement thickness, momentum thickness, shape factor, and frequency distribution of flow velocity fluctuation. Moreover, a method for predicting the flow velocity including the fluctuation values is examined.

This paper proposes a new configuration of the instrumented wheelset, which is used to measure the wheel/rail contact forces for the porpose of assessment of a running safety and evaluaiton of a curving performance of railway vehicles. In general, the contact forces are measured by the strain gauges placed on wheels. The lateral force is measured by measuring the normal strain of the wheel web that is objected by the bending deformation of the wheel in the conventional instrumented wheelset. In this measuring principle of the lateral force, the measured lateral force is influenced by the bending deformation objected by the wheel load. That is, when the contact point between the wheel and the rail is displaced laterally, the wheel load, which is the contact force along the vertical direction, also induces the bending deformation of the wheel web. This could reduce the measurement accuracy of the lateral force. In this paper, a new instrumentation method for measuring the lateral force is introduced by means of the shear strain of the wheel web, which can reduce the influence of the wheel load.

Hunting oscillation is unfavorable to the running stability because it can generate relatively large lateral force between the wheels and tracks. In order to assess the running stability, hunting motion test is usually conducted using a real bogie on roller rigs. Hunting occurs at a certain speed without any disturbance. However, even below the hunting speed, hunting can occur when disturbance is input. The former study showed that there exists a clear point where initial lateral displacement of the wheelset caused hunting oscillation and the point originates from unstable limit cycle. Therefore, the author tried to calculate the unstable limit cycle by utilizing the shooting method, which can calculate periodic solution for nonlinear system. This paper reports summary of the shooting method and its application for vehicle dynamics model, then examines the validity of the result obtained by the method.

Carbody elastic vibration of railway vehicles negatively affects the ride comfort of passengers. One of the sources of the vibration is excitation force induced by the longitudinal vibration of the bogies. The purpose of this study is to develop a longitudinal vibration isolator between carbody and bogies for railway vehicles. Since the vibration isolator possibly affects running stability of the vehicle, we need to develop a device which copes with both the vibration reduction and running stability. To confirm the vibration isolation performance and also to evaluate the running stability, we construct a simulation model of a test vehicle equipped with rubber bushes in the traction links and yaw dampers using multi-body dynamics software. As a result, we confirm that the elastic vibration can be reduced by equipped with displacement-dependent rubber bushes to the traction links. It is also verified that the device affects the critical hunting speed, especially under the condition where a yaw damper is attached to one side of the bogie, which simulates the failure of another damper. Then, using the simulation model, we investigate the desirable characteristics of the device in order to reduce the carbody elastic vibration and to improve the running stability simultaneously. As a result, we confirm that it is possible to cope with both the vibration reduction and running stability by changing the characteristics of the device.

The brake systems used in current railways utilize the tangential force (so called the adhesion force) acting upon rails and wheels for reducing speed. The tangential force is affected by conditions such as climate, contact surfaces of rails and wheels. It is difficult to keep the braking performance in the lower tangential force conditions which can frequently cause wheel slides. The wheel slide protection system (WSP) is one of the useful approaches used in many vehicles. However, existing WSPs control the braking forces based on the information induced only from rotational speed of the wheels. They do not optimally perform braking in response to the frequently changed tangential force. In this study, we propose the use of the value equivalent to the tangential force, which are estimated by using brake cylinder pressures during wheel slides. In addition, we propose a method which extracts the statistic feature about the tangential force from many braking test data. Furthermore, we set out a new WSP which can decide the action based on the effectiveness and the statistic feature about the tangential force. We carried out bench tests and the results of the test show the proposed WSP can keep higher deceleration than existent ones.

From past research, when the riding comfort of the E5 Series High-speed train was evaluated by optical topography, the stress felt while riding was affected by various external influences other than vehicle vibration, and reflected the overall comfort of the vehicle. Therefore, in this study, we focused on the cabin noise in the High-speed train, which is considered to be one of the major factors that determine the comfort inside the High-speed train, and objectively evaluated the comfort against the cabin noise in the High-speed train by optical topography. As a result, there is a correlation between the discomfort index of High-speed train in-vehicle noise and the stress brain index, and the effect of cabin noise on the in-vehicle comfort of the High-speed train can be accurately evaluated by optical topography, and the predictable discomfort formula considering the sound quality index is used. It was clarified that the evaluation method can be used to evaluate the comfort of cabin noise in the High-speed train.

In order to evaluate stresses including stress concentration at weld toes for fatigue evaluation of complex-shape welded structures such as railway bogie frames, previous studies proposed the stress assessment procedure through measuring strains of actual structures by attaching strain gauges with gauge edges to be at weld toes. On the other hand, several codes and recommendations including fatigue design recommendation of International Institute of Welding provide the structural hot-spot stress method for fatigue evaluation of the complex-shape welded structures. This study compares the stresses resulted from both of the stress assessment methods. Evaluated models were basic type welded joints without post treatments. As a result, both of the stress assessment methods provided approximately the same assessment results for the joints with plate thickness of 8–16 mm, the thickness range that was able to be compared.

In this paper, we propose a method for evaluating vehicle dynamics performance in the medium and low speed range using an autopilot system. In recent years, high performance has been required as a need for vehicle. Conventionally, in vehicle dynamics performance evaluation, there are many parts that rely on human driving, and there is a large variation in driving. Especially at medium and low speeds, quantitative evaluation was difficult due to the above variations. Therefore, we developed a driver model that minimized the variation of the following trajectory with respect to the target trajectory at medium and low speeds, and implemented it in the autopilot system. Then, the vehicle dynamics performance was quantitatively evaluated from the amount of operation during running.

In this study, a broad-band frequency tunable dynamic vibration absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer (MRE) that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. Results of preliminary performed experiments show that the vibration of an acrylic flat plate could be reduced automatically in the frequency range from 50 to 150 Hz with simple techniques to determine the strength of the magnetic field to be applied to the MRE by controlling the electric current applied to the coil. Then, we applied the proposed absorber to decrease the noise in a vehicle cabin by absorbing the vibrational acceleration of the vibrating parts of the vehicle. We could reduce interior engine booming noise or road noise according to the small steps by absorbing the vibration of the vibrating parts of the vehicle with controlling the electric current applied to the coil based on its engine speed or vehicle speed.

In this study, to achieve a human-adaptive vibration design in a vehicle cabin based on the sensory characteristics of the passengers, the psychological stress of the passengers by the vibration of the seat of the commercial vehicle were studied. As an initial study, the measurement of the vibrational acceleration and its modal analysis of the seat were performed. We measured 22-points and 10-points vibrational acceleration for 3-directions (vertical, longitudinal, and lateral) of the seat and occupant in a commercial vehicle, respectively. Then, we performed modal analysis with obtained data. Results showed that the seat had four distinct vibrational modes in the idle state: vertical; horizontal; folding; rising. The amplitude of the folding mode vibration was 24 Hz and it was consistent with the 2^nd order vibration of the engine of the vehicle. It was the biggest vibration of the seat. We also performed the measurement of the brain wave and pulse wave of the occupant seating on the seat to estimate his psychological stress caused by the seat vibration. Results showed that the psychological stress could be estimated by using his brain wave. However, the pulse wave was not suitable to estimate the psychological stress of the occupant due to the negative influence of the noise caused by the engine to his pulse wave. In addition, we also found that the sensitivity of the occupant to the seat vibration can be predicted from the results of spectral analysis of the gravity center of the occupant.

This paper proposes a design method of traction control by multiple-stage fuel injection cut using model predictive control (MPC) for an internal combustion engine. Traction control by fuel-cut is an effective method to improve acceleration performance and stability of motorsport vehicles in some situations where usage of an electric throttle valve is restricted or undesirable. We previously proposed a traction control method by two-stage fuel injection cut using MPC, which improved vehicle acceleration performance. However, fluctuation of slip ratio caused by fuel injection cut of the internal combustion engine was observed. The proposed method in this paper aims to resolve this problem by the multiple-stage fuel injection cut operation. This control is performed by MPC with the evaluation function including time-derivative terms of slip ratio. The method to reduce the computational load for prediction algorithm is also proposed. The effectiveness of the control is demonstrated by numerical simulation and Hardware-In-the-Loop-Simulation.

Advances in sensing and control technologies have led to rapid improvements in safety devices to avoid hazardous events. However, when the driver's does not operate the vehicle in automatic operation and the system requires sudden operation, the sudden change in vehicle behavior by the system may put passengers in danger. The purpose of this study is to realize the discovery of the driver's hazard prediction in normal driving by deep learning. In this experiment, we used deep learning to categorize the forward images based on the unconscious braking/accelerating operations and the resulting acceleration in a situation that does not lead to a near miss accident, and extracted the features. This can prevent sudden operations by detecting the risk of collision earlier. We have shown that it is possible to discriminate situations that do not lead to near miss accidents by investigating the conditions of classification for the early identification of collision risk from images in front of the vehicle.

This study focuses on a driver-less shuttle (level 4 driving automation) with four-wheel-drive in-wheel motors. We aim to construct a control law for a braking/driving force distribution of the front and rear wheels to prevent passengers from falling over inside the shuttle. The previous paper modeled the shuttle by using a half-car model which considers the braking/driving force to establish the equation of motion and a passenger by using a rigid body. This study introduces a zero-moment point (ZMP) of the passenger system as an evaluation index for the possibility of falling over inside the shuttle. To suppress the evaluation index value, the present manuscript applies a 2DOF control system which consists of an optimum regulator as a state feedback controller and a feedforward controller derived from the inverse model. Numerical simulation is performed to verify the effectiveness of the proposed control method.

Recently, accidents caused by elderly drivers from pedal operation error, when pedal change operation between brake and accelerator pedal have become a social problem. In the previous report, the authors, focused on the vertical pedal step, among the pedal layout of the brake and accelerator pedal, and analyzed the behavior of the right toe during the pedal change operation from the accelerator to the brake of an elderly driver, using plural type vehicles (different vertical pedal step type) as test vehicles. As a result, the authors clarified that not only physical decline due to aging but also vertical pedal step is one of the factors that influence pedal operation error. When the vertical pedal step is low, it is possible to operate the pedal in a stable state with the driver’s heel attached to the floor, but when the vertical pedal step is high, this is not possible. And furthermore, even when the pedal step is low, it was confirmed that there are cases of near misses in which the driver steps on a place near the accelerator pedal, depending on the position of the heel. In this report, the authors focused on the position where the driver places the heel of the right foot when the vertical pedal step is low, and analyzed the relationship between the position of heel and occurrence of pedal operation error. As a result, the authors confirmed that the position where driver’s heel is placed is one of the factor that influence pedal operation error.

The additive manufacturing technology has a potential to improve manufacturing costs and may help to achieve high-performance aerospace structures. One of application candidates would be a wind tunnel wing model. A wind tunnel model requires sophisticated designs and precise fabrications for accurate experiments, which frequently increase manufacturing cost. The additive manufacturing technique may help to reduce the expensive testing cost and allow us to investigate aeroelastic characteristics of new designs of aerospace structures as many as we need. In this paper, metal wing models with the additive manufacturing technique for a flutter test has been studied. Structural/aeroelastic characteristics of additively manufactured wing models are evaluated numerically and experimentally.

In recent years, careless accidents of field workers in situations where hard labor is often placed, such as construction sites, and excessive physical burden associated with work has been regarded as problems. At these civil engineering and construction sites, it is regarded that many accidents and injuries are caused by fatigue. As a method for evaluating fatigue, measurement of heart rate and blood pressure with a smartwatch is generally used, but the measurement of these methods differs greatly depending on individual differences. It is difficult to measure fatigue appropriately. Therefore, in this study, we applied the detection of three-dimensional center of gravity (D3DCG) to bodies under walking conditions. D3DCG calculates the position of the center of gravity of the bodies (C.O.G.) from the frequency of heaving and rolling in walking motions. We conducted experiments of long-distance walking by subjects who differ the distinction of age and sex. The subjects walked in hours on smooth surface and rough surface measuring the motions. Results of calculations by D3DCG showed that there were three different C.O.G.s found in the bodies by which fatigue of walking may be measured. When the fatigue accumulated, each amplitude of the three C.O.G.s changed accordingly to balance the bodies against the fatigue. Degree of the change was quicker on the rough surface than on the smooth surface.

The crash safety structure of the railway vehicles is important as one of the safety measures against the train crews and the passengers in the event of a collision accident. It is impractical to perform collision testing many times using the actual train unit in order to design the crash safety structure. Therefore, the numerical simulation is effective and it is important to validate the analytical accuracy. Firstly, the authors performed the collision test of an actual-size partial stainless-steel carbody structure of a railway leading vehicle against a dump truck for the purpose of validating and improving the analytical accuracy of numerical simulation. Secondly, we carried out finite element analysis under the same condition as the experimental test. We compared the numerical result to the experimental one in terms of the deformation behavior, time histories of the total compression load and the velocity of the test specimen. As a result, the numerical result was consistent with the experimental result.

This paper considered the yaw resonance mode at general vehicle speed. The equilibrium position is on the extension line of the vehicle speed vector at the position where the sideslip angle becomes 0 in steady turning, and the rear wheel moves toward this line. Furthermore, this paper points out the response parameters that govern the two-stage transient movement at the general vehicle speed.

Steering torque is one of the most important information for a driver because it influences the driver’s maneuvering. The characteristics of steering torque are affected by mechanical properties of the steering system like torsional stiffness, steering wheel inertia and the mechanical friction. When vehicle handling and stability are evaluated using a driving simulator or a steering torque simulator, it is necessary to give proper steering torque considering these effects. In this study, two types of friction models, the LuGre model and the Masing model, were applied to the steering torque simulator. By numerical and experimental evaluation, it is shown that the LuGre model can reproduce various kinds of steering friction characteristics like the Masing model.