Monitoring the conditions of railway asset is essential for ensuring the railway safety. This paper presents the application of condition monitoring technologies to vehicle suspensions and railway track. The theory, concepts and implementation status are summarized with the key trends appeared in recent international railway conferences and discuss with a future look.

View full abstract

[in Japanese]

View full abstract

Dedicated trucks with air-suspension systems are used in the transport of cultural properties. However, there is limited information regarding the determination of a safe position on the loading platform and the total load corresponding to which the air-suspension achieves optimum performance. It is, thus, essential to conduct a detailed analysis of such trucks in order to ensure and enhance the safety of cultural properties during transit. In the present work, we developed a simple model of an air-suspension system and truck and simulated the possible situations likely to be encountered during transportation. Analysis results clearly demonstrate that vibration levels experienced during transit are influenced by the type of suspension system, payload, payload center of gravity position, truck speed, and loading position. Furthermore, the characteristics of the tires must be considered in the analysis, and the road surface characteristics and air-suspension systems must be modeled more precisely.

View full abstract

A rubber bush used in an automotive suspension system is an important element for the ride comfort and the driving stability. The relation between the applied force to the rubber bush and its deformation is non-linear and shows a feature of viscoelasticity. In a real-time analysis of a vehicle model with the rubber bush, it becomes a subject of discussion how to express the characteristic of the rubber bush with a simple model. In this study, modeling method for rubber bush based on evaluation test was considered. A generalized maxwell model was used for the bush model. In order to identify the model parameters based on measurement results, evaluation test of viscoelastic material was conducted.

View full abstract

A rubber bush used in an automotive suspension system is an important element for the riding comfort and the driving stability. Since rubber bush has a high stiffness, a vehicle model considering rubber bushes has high natural frequencies. In the analysis of such a stiff system, a small time step is required to execute a steady simulation. As a result, the amount of calculation is increased. However, in real-time analysis, it is necessary to calculate each step of numerical integration within a specified time. Therefore, real-time analysis of a stiff system requires high efficiency. In this paper, the dynamics analysis of a vehicle model with rubber bush was executed with Generalized-α method, and the execution speed and the accuracy of analysis were evaluated.

View full abstract

It is important to grasp the road surface condition in real time to prevent slipping accidents caused by ice road surface. Particularly in autonomous driving technology, its importance increases. We focused on QEF (Quasi-Electrostatic Field) sensing technology as one of the methods of road surface condition sensing technology. QEF has a characteristic that it is distributed like a static electricity in a dielectric such as a human body or a vehicle body. QEF sensing is to sense electrical changes occurring between the tire and the road surface with a sensor on the vehicle body. Therefore, the tire itself is a sensor and there is no need to attach a sensor device directly to the tire. In this research, we developed a QEF sensor unit and conducted comparative experiments on dry road, wet road, snow road and ice road using experimental vehicles. As a result, it was found that a difference of 10 dB or more was obtained as the amplitude value average of the voltage of the frozen road compared with other road surface conditions. Based on this, we proposed and verified the road surface estimation method with the amplitude value as the feature quantity, and it was confirmed that the road surface condition excluding the snow road is consistent.

View full abstract

An accurate grasp of a road profile is important because an uneven road causes vibration, which affect the vehicle stability and ride comfort. In this paper, a cost-effective estimation method of a road profile from the measurement data is proposed. In the method, the estimation is performed with only inexpensive sensors that can be mounted on general cars. The road profile is estimated by using a disturbance observer and multibody dynamics analysis. First, the road profile is estimated with a disturbance observer based on a simple model. After this process, the road profile is corrected with an iteration process by using a multibody model based on a developed trailer by authors. In this study, the accuracy of the estimation method of a road profile was improved by considering the longitudinal tire force. In order to evaluate the effect of longitudinal tire force in the estimation method of a road profile, running simulations and running tests were conducted with the trailer. The result of estimated road profile was compared to the input road profile. The advantage of considering the longitudinal tire force was shown in the estimation method of a road profile.

View full abstract

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.

View full abstract

Tricycles, prevailing in Asian countries, have attractiveness such as lightweight, low cost, small turning radius and high loading capacity, but have the disadvantage being easy to rollover at the time of cornering. In the case of a tricycle with one wheel in the front and two wheels in the back, even if the rear track is expanded, the anti-rollover effect is small if the center of gravity is not close to the rear axle. The analyzed tricycle model has the typical specifications with maximum seven occupants. First, the simple rollover threshold estimation and the roll angle calculation for tricycle are introduced modified from the ones for four-wheeled vehicle. Under the disadvantageous specifications against rollover, the rollover thresholds are calculated, considering the relationship of the contribution of several parameters not only the dimensions but also number of occupants. And CarSim, a vehicle dynamics simulation software, is employed to simulate rollover during a steady state turn and a braking in a turn. The calculation results give a few suggestions for avoiding rollover.

View full abstract

It is thought that the first step to understanding vehicle movement is to measure and analyze that movement in order to confirm that it falls within the range of the laws of physics. In the case of a four-wheeled vehicle, in general, the friction limit is defined within the circle of longitudinal acceleration and lateral acceleration through the use of a G-G diagram. Then measurements are taken to confirm that the driving state is within that range. G-G diagram was applied to a two-wheeled vehicle. Measurements were also taken during actual motard riding by top-class Japanese motard motorcycle riders. It was confirmed that this measurement data was distributed within the range of the friction circle. Consequently, it was confirmed that it is possible to use G-G diagram to accurately grasp the vehicle movement limits and the associated driving state for two-wheeled vehicles.

View full abstract

Two-wheeled vehicles have been receiving attention as economical and convenient vehicles. However, two-wheeled vehicles are unstable. Therefore, falling down accidents happen very often by external factors such as wind, slipping and rough road. Moreover, two-wheeled vehicles often require driving skills such as keeping control vehicle’s posture, and it is especially difficult for elderly people. In order to solve this problem, we are developing Motor-and-bicycle Anti Rolldown System (MARS). This system can prevent falling down accident of two-wheeled vehicles by using a gyroscopic effect, and it can control the stability of vehicles. In this paper, we report the optimal feedback gain values for self-standing test by using the prototype which we developed for the first time.

View full abstract

This paper investigates a method to estimate the driver’s braking reaction time in various driving conditions considering the personal differences among drivers. First, the effects of driving conditions on individual driver’s braking reaction time are analyzed by means of analysis of variance (ANOVA) on data collected through driving simulator experiments. From the results of ANOVA, it is found that the braking reaction time is affected by preceding vehicle deceleration, preceding vehicle speed, and inter-vehicle time. Second, this paper proposes a method to estimate individual driver’s braking reaction time in emergency situations based on the performance index for approach and alienation using braking data of normal driving conditions. The braking reaction time estimated by the proposed method is compared with that determined by a conventional method. The results show that the estimation accuracy on the braking reaction time is improved by the proposed estimation method.

View full abstract

This study examines a driver assistance system to predict driving behavior considering the pre-preceding vehicle behavior. The assistance system indicates the evaluation index on road ahead virtually to recognize longitudinal operation easily. Driving simulator experiments are carried out with several participants who are instructed to follow a preceding and a visible pre-preceding vehicles with and without the driving assistance system. The participants with the assistance system realize the driving behavior with the small relative velocity to the pre-preceding vehicle. These effects make it possible not to suppress the variation of the collision risk to the preceding vehicle and to reduce fuel consumption of the following vehicle. In addition, the proposed assistance system does not change visibility of assistance information and makes it possible to follow these vehicles with gentle acceleration in comparison with the conventional assistance system, which is indicated at the rear end of the preceding vehicle.

View full abstract

ADAS (Advanced Driver Assistance System) has been developed recently, and it is desirable that the driver assistance system assists driver to avoid or prevent the high risk situation. Therefore, it is necessary to find situations with high driver’s risk and high assistance effect. In complex traffic situations where other traffic participants exist, the risk of overlooking pedestrians is increased by distributing driver’s attention on steering maneuver. Drive recorder analysis shows that the risk of overlooking pedestrians increases while turning at an intersection. In this paper, experiment was conducted in a test course by using a special test vehicle (called as ARV) equipped with steering control assistance as the driver assistance. By this experiment, it was found that the steering control assistance can double the safety confirmation time for detecting pedestrian under the existence of the lead vehicle so that it may become safer even when following the lead vehicle.

View full abstract

Recently, the number of elderly drivers is increasing in japan. Although the driving performance of the elderly drivers generally tend to decreased due to the decrease of the physical ability, they still have high motivations to drive a vehicle. A shared control based driver assistance system is a promising approach to maintain skillful driving performance. This system allows both driving maneuver input from the human and the system simultaneously. The key feature of the shared control system is the expert driver model which is embedded to indicate the reference maneuvers to the actual drivers. The actual expert drivers perform the driving maneuvers which are combined with lateral control and speed control appropriately. However, the conventional steering shared control systems are focused on the lateral control without considering the speed control. I am order to enhance the shared control system, this paper proposed the expert driver model which calculate the reference steering behavior with longitudinal control by using the reference curvature. The effectiveness of the proposed expert driver model is evaluated by comparing with the experimental results which is conducted by an actual expert driver in curved path tracking maneuvers.

View full abstract

In late years, as natural disaster in Japan, damage caused by The 2011 off the Pacific coast of Tohoku Earthquake and The 2016 Kumamoto Earthquake. The one that is hard to shelter by oneself is left behind at the time of the disaster, and there are people passed away. It is intended and, in this study, investigates refuge by the natural disaster and movement load reduction of the one of the wheelchair user after the disaster in the publication record of documents and the metropolis and districts local government as the fundamental researches. With an existing wheelchair, we evaluate it than the laboratory finding that simulated a disaster. By the experiment, we perform the ride comfort analysis using a vibration measuring instrument. We suggest the new mechanism wheelchair which can evade the barrier of the constant level after a disaster and a disaster based on the knowledge that we got fundamental researches and an experiment effectively.

View full abstract

Traffic accidents caused by the pedal operation error by the elderly drivers have become social problem, for example the collision with structure, vehicle or pedestrian. It is generally known that due to the weakening of the flexibility of the elderly's body, the angle at which the knees are placed inside decreases. As the result, in the sitting posture of elderly drivers, there is a difference in the posture of the legs with non-elderly drivers. This may be the hypothesis that it is one of the major causes of the increase in pedal operation errors by them. In this study, we focused attention on the posture of the leg when parking the vehicle with backward movement, and visually checked the sitting posture of the driver's leg and the behavior of the right foot, the driving in simulating the rearward turning motion experimentally verified by twisting the waist of a person. As this check, it is clarified the relationship between the posture of driver's leg or right foot and the foot location area on the brake pedal, which are assumed making effects of pedal operation error.

View full abstract

To prevent fall accident that occur when elders use mobility devices in pedestrian space, a driving assistance system is required. The objective of this research is to clarify the requirements for such system and construct a driving assist system based on requirements. First, we extracted environmental elements which causes fall accident from mobility scooter’s drive recorders and recorded the driving environment and user’s operation. Among the environmental elements, we especially focused uneven roads which cause failure in prospecting vehicle motion for users. We propose a driving fall risk evaluation method based on prospecting vehicle motion at prospective waypoint by calculating positions of the wheels using an elevation map. We verified the effectiveness of the proposed method in uneven road using a mobility scooter.

View full abstract

The automobile industry is required to deal with the environmental problems including global warming as other industries. Hence, the tire industry is also required to reduce the environmental burden by lowering rolling resistance to improve fuel economy and by improving tire wear to save material. Because rolling resistance and wear are incompatible, the research of tire wear is the important subject. Studies on wear mechanics of tire are classified to three categories, analytical study on indoor and outdoor evaluation, and application of computational mechanics such as the finite element method (FEM). The features of an analytical model are to be used in the conceptual design, to estimate the mechanism and gain an insight more easily than the FEM. Hence, we developed an analytical wear model of tire which can consider the wear caused by higher slip angle or slip ratio. Furthermore, the wear model can deal with the tire wear in arbitrary wear course, since the time history of external force to a tire is calculated by the computer model of the vehicle (CarSim) and then it is transformed to the probability density function of external force by using the shape function of the FEM.

View full abstract

The rail is one of the most important elements in constructing railway system. The phenomenon such as wear or defect will occur caused by the repeated wheel/rail rolling contact. The wear of rail, which does not occur in a short period of time, has a close relation to crack initiation. And there is a possibility that it influences the running stability or the curving performance of vehicle due to the change in the rail profile attributable to it. Therefore, it is very important to analyze the wear development of the rail. 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 to examine the influence of lateral slip on wear development.

View full abstract

Wheel / rail wear affects on running safety, ride comfort, and maintenance. The studies on the clarification of the mechanism of wear development are required. The observation of wear development in practical railway systems requires a great deal of time and cost. To predict the wear profile of wheel and rail, numerical procedure with Multi-body Dynamics Software is proposed in this paper. 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 ones at the wheel/rail contact patch. Both longitudinal and lateral slips effects on the development of wear. So, in this study, to research each influence for wear development by longitudinal slips and lateral slips, we constructed wear predict model in numerical approach and compared between the numerical and the experimental results.

View full abstract

Nowadays Electric Vehicles (EVs) attract people’s attention as means of an environmental problem. However, EVs have disadvantages of their short cruising range. Therefore, our group has proposed Range Extension Autonomous Driving (READ) system which minimizes the consumption energy by optimizing the velocity profile. This paper extendes the method for minimizing the total consumption energy by cooperating with two electric vehicles. The effectiveness of the proposed method is verified by simulations and experiments.

View full abstract

Recently, Drive recorders are spreading and recorded data has been collected everywhere and is used for various purposes. In this paper, we will consider effective presentation method for using DS study as one way to utilize these data. Making a mask on the image and providing a point for easy gaze. We created an environment that enhances the presence and makes it easy to examine.

View full abstract