Takuji Nakai

A proposal of wheel/rail contact model for friction control

Controlling the friction between wheel and rail is direct and very effective measures to improve the curiving performances of railway trucks, because the curving performances depend much on friction characteristics Authors have proposed a method, “fnction control”, which utilizes friction modifier (KELTRACK™ HPF) with onboard spraying system With the method, not only friction coefficient, but also fuction characteristics can be controlled as expected In this study, MBD simulation is very valuable tool to foresee the effect of the control in advance of experiment with real car And the creep characteristics of wheel/rail contact with the fuction modifier takes very important role in the simulation In this paper, authors propose a theoretical model of wheel/rail contact condition considering the creep characterstics of friction modifier, which is derived the application of principle tribological theories

Curving performance evaluation for active-bogie-steering bogie with multibody dynamics simulation and experiment on test stand

The authors propose a new concept of the active steering bogie, which has simple mechanism and high curving performance. Active-bogie-steering bogie has the steering mechanism only between car-body and bogie frame and no mechanism in wheelsets. On curved track, the bogie frames are steered towards radial steering direction by actuators according to active control law. In this paper, we show that the lateral contact force of the leading-outside wheel can be reduced to zero even on very sharp curve by this mechanism. Validity tests were carried out by using a full-size test bogie on the rolling test stand, which can simulate curve-running condition. Bogie parameters and steering actuator characteristics are identified in order to compare the experimental results with multibody dynamics simulation. After these stand tests and simulation, we successfully verified the effectiveness of the proposed bogie mechanism and control.

The Optimum Design of an Onboard Friction Control System Between Wheel and Rail in a Railway System for Improved Curving Negotiation

In the subway lines of Tokyo (Tokyo Metro), there are many tight curves that may cause squeal noise, excessive rail/wheel wear and rail corrugation. To solve these serious problems, an onboard friction control system with friction modifier has been developed by the authors and has been equipped on commercial trains as a trial. With this system, the balance between supply and consumption of friction modifier is very important. That is to say, in order to obtain the maximum effect of friction control steadily, it is natural that an appropriate quantity of friction modifier should be required. In this report, results of experiments with a two-roller-rig testing machine, and analysis of the observed data in commercial train tests are introduced. In addition, the authors considered the method to realize the appropriate balance between supply and consumption of friction modifier.

Study on control of air suspension system for railway vehicle to prevent wheel load reduction at low-speed transition curve negotiation

This article presents the curving performance of railway vehicles with air suspensions. Air suspensions sometimes cause reduction of wheel load at transition curve, which will reduce the margin for the safety of curve passing. And it may be the reason of derailment. In this study, the reduction of wheel load was restrained by using the new concept devices. The proposed active control device can supply air to, or exhaust air from, air springs by manipulating the levelling valve (LV), which is the core component of the current air suspension system, so that the distribution of pressure to each air spring can be controlled, and the reduction of wheel load can be prevented. At the same time, the proposed system is secured from electronic fail because the current air suspension system can be restored mechanically. Computer simulation and bench experiments were practised, and the expected control performance was obtained. As a result, the reduction of wheel load was restrained, and the safety of running was enhanced.

Simulation of Low Speed Transition Curve Negotiation and Air Suspension Control to Prevent Wheel Load Reduction of Railway Vehicle

This paper presents the curving performance of railway vehicles with Air Suspensions. Air Suspensions sometimes cause reduction of Wheel Load at transition curve negotiation. The axle spring of leading axle outside and air spring of leading bogie outside will extend when passing the exit transition curve because of the distortion of the track plane. Because Air Suspension has an automatic leveling function that each air spring is controlled by Leveling Valve to maintain a constant length, air in the extended spring exhaust through Leveling Valve to reduce the pressure of this air spring in order to make it back to original length. So the air spring pressure of leading bogie outside reduces furthermore and Wheel Load of leading axle outside reduces severely. This may be the reason of derailment. The distortion of track plane unbalances inner pressure of Air Suspensions and vertical load of wheels at entrance transition curve, because of the nonlinear characteristic of Air Suspension system caused by the Leveling Valve. Computer simulation of low speed transition curve negotiation shows that the lower running speed is, the more severe unbalance of Air Suspension inner pressure and Wheel Load become. The reduction of 1st axle outside wheel at exit transition curve is depended on this Wheel Load unbalance phenomena at circular curve. And this running process influences the after behavior of railway vehicle. The simulation also shows that the longer entrance transition curve is, the more severely the 1st axle outside Wheel Load reduces. The full-scale bench experiments gave the result as nearly same as computer simulation. A new concept control device is proposed to prevent the reduction of Wheel Load at exit transition curve. Both the simulation and bench experiment proved its control performance of Wheel Load reduction prevention. And proposed control device can also be used in tilting control and kneeling control of railway vehicle. General multi-body dynamics analysis software SIMPACK is used to confirm advantageous effect of proposed control device and full vehicle curve passing simulation shows that derailment coefficient reduced when proposed control device is applied in transition curve negotiation.Copyright

Wheel/rail friction control with feedback system detecting yaw moment of wheelset

In the subway lines of Tokyo Metro, there are many tight curves that may cause squeal noise, excessive rail/wheel wear and also rail corrugation. To solve these serious problems, an onboard friction control system has been developed by the authors and has been equipped on some commercial trains [Y. Suda, H. Komine, T. Iwasa, M. Tomeoka, K. Matsumoto, N. Ubukata, M. Tanimoto, M. Nakata, and T. Nakai, Improvement of curving performance with friction control between wheel and rail, The 17th IAVSD Symposium Poster Session, Lyngby, Denmark, August, 2001; Y. Suda, H. Komine, T. Iwasa, T. Fujii, Tomeoka, K. Matsumoto, N. Ubukata, M. Tanimoto, M. Nakata, and T. Nakai, Experiment and analysis for improvement of curving performance with friction control between wheel and rail, Veh. Syst. Dynam. 41(Suppl.) (2004), pp. 507–516.]. With the system, in order to obtain the enough effect of friction control steadily, it is natural that an appropriate quantity of friction modifier should be required [K. Matsumoto, Y. Suda, T. Fujii, H. Komine, M. Tomeoka, Y. Sato, T. Nakai, M. Tanimoto, and Y. Kishimoto, The optimum design of an onboard friction control system between wheel and rail in a railway system for improved curving negotiation, Veh. Syst. Dynam. 44(Suppl.) (2006), pp. 531–540]. On such a viewpoint, the authors propose a new friction control system with the detection of yaw moment acting on the running wheelset. In this paper, first, outline of conventional feed-forward control system is introduced; secondly, the concept of feedback friction control system is presented considering the results of the multi-body dynamics simulations, and finally some field running test results of the developed system are discussed.

Correlation between Effects of Friction Control and Quantity of Supply

Controlling the friction between wheel and rail is direct and very effective measures to improve the curving performances of railway trucks, because the curving performances of truck depend much on friction characteristics. Authors have proposed a method, “friction control”, which utilizes friction modifier (KELTRACKTM HPF) with onboard spraying system. With the method, not only friction coefficient, but also friction characteristics are able to he controlled as expected. In this paper, results of fundamental experiments are reported which play an important role to realize the new method.

Evaluation of Friction Control Between Wheel/Rail by Simulation and Experiment

Controlling the friction between wheel and rail is direct and very effective measures to improve the curving performances of railway trucks, because the curving performances depend much on friction characteristics. Authors have proposed a method, “friction control”, which utilizes friction modifier (specialized for wheel / rail contact) with onboard spraying system. With the method, not only friction coefficient, but also friction characteristics can be controlled as expected. In this paper, authors introduce a very interesting finding that revolution difference between leading and trailing axles depends on effectiveness of friction control which was found in the procedure of simulation. In order to certify the reality of the finding, authors carried out experiments with 1/10-scaled model vehicle. And as the result, the potential use of revolution difference between the leading and trailing as a means to evaluate effectiveness of friction control was recognized.Copyright