In the railway sector, efforts are being made to improve the efficiency of operations. One of these is the automatic operation of trains. To keep the train running safely, it is necessary to make ...sure that there are no obstacles in front of the railway vehicle. Therefore, automatic train operation requires obstacle detection system in front of the railway vehicle. In recent years, some railway operators have introduced onboard cameras as drive recorders in order to understand the situation at the time of an accident and to investigate the cause. In addition, efforts are being made in the railway sector to improve operational efficiency through the use of onboard cameras. In this paper, we propose an obstacle detection method using an onboard stereo camera. The proposed system can be divided into three parts. First, the center position of the track is estimated using RGB images, and the search area for obstacle detection is set. Second, proposed system checks for the presence of objects within the set search area and creates a candidate area of obstacle. Finally, the area of each neighboring candidate area of obstacle is calculated, and if the area is greater than a certain value, the object is determined to be an obstacle. Furthermore, the proposed system is verified by using a 1/10 scale model experimental vehicle. Validation results show that the proposed system is capable of detecting obstacles in front of railway vehicles.
This paper describes an investigation into the vibration characteristics resulting from lateral track irregularities that are transferred and become lateral vehicle vibrations when a railway car ...transits a curved section of track. These transfer characteristics are derived via vehicle dynamics simulations that take into consideration nonlinear characteristics such as flange contact between the wheels and rail. The derived results revealed that the transmissibility of wheel-set lateral movement from lateral track irregularity is larger on a curved section of track than that on a straight section due to restrictions between the wheel flange and rail. Consequently, the mechanism of vibration transfer that occurs when a railway vehicle is transiting a curved section of track can be theoretically explained.
To clarify the behavior of railway vehicles under crosswind, a new method using the left-right balance of air spring pressure is presented in this paper. The rate of off-loading, which is an ...evaluation index for vehicle behavior, can always be estimated by the new method without conventional special wheel-set. The method is theoretically derived and the accuracy is experimentally verified comparing the new method with the conventional method. In the experiment, lateral forces equivalent to crosswind were loaded statically or dynamically, and a running test was conducted. The results show that the new method and the conventional method are in good agreement and that the new method is useful when analyzing vehicle behavior under crosswind. By applying the practical method to the Shinkansen, it is possible to obtain statistical data on vehicles running at higher speeds or under higher wind speeds easily than with conventional methods. Much data was analyzed on the relationship between wind speed and the rate of off-loading, and the validity of the Kunieda’s equation used for vehicle design under crosswind is verified. This method can monitor effects of crosswind on vehicles not only at specific points but also along railway lines. Therefore, it is possible to identify areas where vehicles are likely to be affected by strong winds. Some examples further improve safety against strong winds are shown in this paper.
Wheel slips in railway vehicles cause poor acceleration and damage to wheels and rails. Re-adhesion control is widely used to resolve wheel slips in electric motor cars. In re-adhesion control, it ...has been an important problem to consider appropriately the vehicle dynamic motion, which affects the control performance greatly. In this study, we investigate the mechanism and characteristics of slip misdetection phenomena which occur due to bogie vibration excited during re-adhesion control. We construct a three-dimensional vehicle model including roll motion with parallel Cardan drives. The tangential force coefficient model between wheels and rails includes the influence of translational velocity, slip velocity and wheel loads. The simulation model is validated by comparison with measurements in a test run of a real vehicle conducted in previous research. Simulation results illustrate the behavior of the bogie under traction such as the difference of wheel loads of four wheels and the attitude of the bogie frame. It is shown that continual slip misdetection can occur because of pitch and roll vibration of the bogie frame which is excited during re-adhesion control when the primary vertical damping coefficient is small. The misdetection is prevented by changing the amount of motor torque reduction in re-adhesion control. The appropriate range of the amount of reduction to avoid the misdetection gets narrower as the primary vertical damping coefficient decreases. The primary vertical suspension stiffness and characteristic of tangential force coefficient also affect the occurrence of the misdetection.
In recent years, condition monitoring technologies have been widely developed aiming at safer railway operation and maintenance cost reduction. Condition monitoring systems of railway for both from ...onboard and on track have been widely studied thanks to the recent development of sensors. Using equipped sensors on track, as an example of the bogie abnormality detection, the diagonal imbalance of wheel-load for four wheels in a bogie is closely related to the running safety on curve. If serious problem happens in the bogie frame, the diagonal imbalance may change, and wheel load reduction occurs. For these reasons, the monitoring of the diagonal imbalance from track has a potential usefulness. However, in our previous research, the measured imbalance can be varied even though the focused bogies run on the track under almost the same condition such as boarding rate, vehicle velocity and so on. If the cause of variation is clarified, the limit of abnormality detection accuracy can be clarified. Therefore, in this study, variation of the measurement of bogie’s diagonal wheel-load imbalance are investigated. Furthermore, factors that affect the variation of the measurement is investigated using MBD simulation.
When railway vehicles run on sharp curves, the coefficient of friction (COF) between the outer rail and the leading-outside wheel flange of a bogie is an important value related to problems such as ...wheel/rail severe wear, squeak noise arising from wheel/rail contact, and running safety against flange-climb derailment. In general, it is difficult to grasp the actual state of COF, which changes from moment to moment during commercial operations. From the viewpoint of running safety and maintenance, it is desirable to detect curved tracks with relatively high COF from the entire service line. The monitoring bogie, which can measure wheel/rail contact forces during commercial operations, has realized a long-term observation of wheel/rail contact forces. For further applications of the monitoring bogie, the simulation-based estimation method of COF at the wheel flange have been proposed in the author’s previous paper. Furthermore, an investigation based on roller-rig tests have been conducted. However, the probability of the flange wear progress cannot be determined only by COF at the wheel flange, and other factors should be involved. The wear number is used to assess rolling contact fatigue and wheel/rail wear progress. In the present paper, on the basis of a multi-body dynamics simulation model of the roller-rig equipment, the difference of the wear number among four lubrication conditions on the bogie is clarified. The estimation method of COF is extended to estimate the wear number simultaneously. The extended method is applied to the roller-rig test and the wear number is estimated. The estimated wear number shows qualitative agreement with the amount of wear debris, which is observed in the roller-rig test conducted in previous research.
The conventional railway wheelset benefits from its self-steering and self-centering ability. Because the wheelset has a simple structure and preferable dynamics, railway trucks with wheelsets have ...been widely used for nearly 200 years. In the design of a railway vehicle with wheelsets, compatibility between curving ability and hunting stability has been studied for many years. Based on past research, the vehicle design with conventional wheelsets has been well summarised. Today, the requirement for railway systems has dramatically changed. For example, high-speed trains are required to run over a 350 km/h cruising speed, while maintaining a high quality of ride comfort and light rail vehicles for urban transit, are required to achieve an excellent curving ability at intersections and turnouts, while maintaining a sufficient degree of safety against derailment. It is true to say that unconventional approaches are necessary for designing the next generation of railway systems. In this paper, the history of research on steering bogies, including conventional wheelsets, is explained. Examples of unconventional railway vehicle concepts are introduced. Furthermore, a new wheelset concept based on the reconsideration of the wheel-rail interface is mentioned. In the new wheelset concepts, gravity stiffness is potentially effective to realise high curving performance; therefore, the dynamics and practical application, including negative tread conicity in independently rotating wheelsets, are mentioned. Nowadays, active control of the wheelset is becoming a practical solution for guidance and is mentioned regarding its brief history and future possibility with unconventional bogie design.
This study evaluates the effectiveness of a driver assistance system at signalized intersections by using an incident database. The research target is in the incident scenes of a vehicle and crossing ...pedestrians in which the vehicle proceeds straight to the signalized intersection. The evaluation of the effectiveness for the driver assistance system has three steps. Firstly, incident scenes for the crossing pedestrian during an amber traffic signal are extracted from the incident database by visual observation. Next, the extracted incident scenes are classified according to the behaviors of both the vehicle and the crossing pedestrian, and the location of the incident. Finally, assuming the driver follows the driver assistance system, the extracted incident scenes are analyzed as to what extent the incident could be prevented based on numerical simulation where the vehicle moves following the decision of the system whether continuing forward or stopping. For cases that the driver tries to enter the intersection despite the amber signal and being able to stop by the stop line, the driver assistance system is supposed to prevent the incident effectively. For cases that the crossing pedestrian does not obey the pedestrian traffic signal, the driver assistance system is found not to be effective. However, if both the driver and crossing pedestrian obey their respective traffic signals, the driver assistance system can prevent the incident effectively in many cases.
The authors researched and developed a new measurement method that can continuously measure the contact forces and derailment coefficients at all curves of commercial lines. This new method can ...determine the derailment coefficients, which change according to the friction coefficients and other factors, using the measuring system on in-service trains. In this paper, the analysis results for actual curve data collected on commercial subway lines are introduced. Additionally, parameters that are influential on the changes of the derailment coefficients, such as “friction” and “track irregularity,” are discussed using the regression analysis on the accumulated data with the newly developed system.
•We developed a new measurement method that can continuously measure the contact forces.•The method can grasp rail/wheel interface conditions every time using service trains.•We are collecting huge data on commercial lines by the developed method.•We analyzed the mechanism of increase of L/V (i.e. Y/Q) in sharp curves.•Increases of L/V by friction change and track irregularities are verified.
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.
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