In the latest high speed railway vehicles, air spring car-body tilting control systems are employed to increase speed and improve ride comfort on curved sections for achieving shorter travel time. This system tilts the car-body by controlling the height of the air springs when the train runs into curved sections. However, the rolling vibration occurs when the train travels through transition curves at high speed. This paper presents a design method based on a state observer to suppress the vibration of air spring car-body tilting vehicles. Experiments were conducted on a half car-body test bench and curving simulation results show the effectiveness of our proposed method.

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The operating railway of Hokkaido Railway Company stretches for approximately 2,500km, one third of which (a section of about 800km) is used by a notably small daily mean number of passengers carriedbelow 500. This yearly shrinking railway use causes JR Hokkaido severe loss-making operations, along with route bus companies. Meanwhile, JR Hokkaido has continued various operations such as "Driver-only Operation" to improve the management of local lines, and "Review of Station Operations," including for the assignment and working hours for station employees. However, such corporate efforts fail to revitalize the management, even with cost reduction measure in particular. Amid these circumstances, dual mode vehicle (DMV), a new concept which can achieve the running of a vehicle both on the railway and road, has been developed to improve the management of local lines.

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We have devised a steering system in which the magnetic elastomer is used for the elastic members such as a rubber bush of the axle box suspension. The magnetic elastomer is composed of magnetic particles and the elastomer such as synthetic rubber. This material is characterized by its hardness variation depending on the magnetic field. This axle box suspension is capable of varying the longitudinal stiffness. In straight sections, the application of this axle box suspension ensures running stability by increasing the longitudinal stiffness by means of applying a magnetic field. On the other hand, in curve sections, it improves curving performance by decreasing the longitudinal stiffness by means of turning off the magnetic field. We made test pieces towards the development of the magnetic elastomer for the steering truck. In a characteristic test, we confirmed that the Young's modulus of the magnetic elastomer changed in the range of about five times depending on the presence or absence of the magnetic field. In addition, we simulated the vehicle running model by applying the longitudinal stiffness change of the magnetic elastomer to the axle box. We confirmed that this axle box was capable of reducing the average of the outer wheel lateral force in the circular curve section compared to that of the normal axle box.

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We have devised a steering system in which the magnetic elastomer is used for the elastic members such as rubber bushings in the axle box suspension of railway vehicles. The magnetic elastomer is composed of magnetic particles and the elastomer such as synthetic rubber. This material is characterized by its hardness variation depending on the magnetic field. The axle box suspension using the magnetic elastomer is capable of varying the longitudinal stiffness. In straight sections, the application of this axle box suspension ensures running stability by increasing the longitudinal stiffness by means of applying a magnetic field. On the other hand, in curve sections, it improves curving performance by decreasing the longitudinal stiffness by means of turning off the magnetic field. We made test pieces towards the development of the magnetic elastomer for the steering bogie. In a characteristic test, we confirmed that the Young's modulus of the magnetic elastomer changes in the range of about five times depending on the presence or absence of the magnetic field. In addition, we simulated the vehicle model by applying the longitudinal stiffness change of the magnetic elastomer to the axle box of the bogie. We confirmed that this axle box was capable of reducing the average of the outer wheel lateral force in the circular curve section compared to that of the normal axle box.

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In order to shorten travel time of a limited express train operated between Sapporo and Kusiro, the tilting diesel car called series DC 283 with a forced steering bogie had been developed by JR Hokkaido and RTRI. The regular operation of the train was started in March, 1997. This paper describes the lateral force between wheel and rail as observed on curve in field tests and that obtained from computer simulations. The influences of varying of steering ratio and wheel tread profile on the lateral forces were verified through simulations and field tests. The results of simulations and field tests are as follows; (1) The lateral force can be reduced by employing the forced steering bogie. (2) The decrease of the lateral force due to the forced steering bogie should be verified not only on circular curve but also on transition curve. (3) The lateral force of first wheelset is the largest. (4) The lateral force can also be reduced by using an arc profile tread on trasition curve. (5) In circuler curve, the steering performance is less dependent on wheel profile.

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The authors have developed an assist steering bogie system using hydraulic actuators to improve curving performance on narrow gauge line railway vehicles. This system can be applied in ordinary bogie angle linked steering systems. Some numerical simulations are carried out to check the reduction effect of the lateral axle load, and then a running test using an actual vehicle is conducted. These examination results have shown the effect of assist steering bogie system is capable of reducing the lateral axle load at transition curve sections. Although further studies concerning fail-safe functions are needed to apply these steering bogie systems into practical use, a considerable potential of the system can be confirmed.

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It’s generally known that tangential force of wheel/rail interface which depends on a change of coefficient of friction between wheel and rail has a big influence on a steady lateral force of railway vehicle. According to our past researches, regardless of an attack angle, tangential force coefficient becomes smaller in the case with fine unevenness than in the case without fine unevenness on the surface by means of a two-disk rolling contact machine. In particular, a tangential force coefficient is more affected by the situation of with /without fine unevenness under low relative humidity condition. The conditions under low relative humidity are almost the same as the conditions that a coefficient of friction of wheel/rail is high. In this paper, in order to reduce steady lateral force during a railway vehicle passing curve, we proposed a new wheel tread profile with providing one streak of fine unevenness, called ‘Micro-ribbed wheel tread profile’ on a wheel tread away from a flange. We verified a validity of this wheel tread profile by applying a numerical analysis and a running test in RTRI. As a result, we confirmed that the Micro-ribbed wheel tread profile is effective to reduce the steady lateral force of the outside wheel/rail interface when the railway vehicle is passing curve under high coefficient of friction between wheel and rail.

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In this paper, we proposed a method to introduce a fine unevenness on a part of a wheel tread in order to improve a curving performance without decreasing a hunting stability of railway vehicle, and verified a validity of this proposed method by applying a numerical analysis. Although a rolling radius difference of wheel tread with fine unevenness is the same as those without fine unevenness, a contact patch near the side other than the flange are different. When a railway vehicles run into a curved section, a contact point of inner wheel/rail shifts to the side other than the flange. At this time, if the creep coefficient of an inner rail side becomes small, the lateral force of inner and outer rail can become small, and thus the vehicle can pass the curve more smoothly. We showed that especially the wheel tread with fine unevenness has a large reduction effect of outer lateral force and derailment coefficient in cases where vehicles run on a small radius curved section with a large cant at a low speed by numerical analysis.

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