Shihpin Lin

Self-steering ability of the proposed new concept of independently rotating wheels using inverse tread conicity

This paper proposes the use of independently rotating wheels with inverse tread conicity to get self-steering ability without any complex bogie structure. The effectiveness of the vehicle with two single-axle bogies that use two independently rotating wheel units with inverse tread conicity is proved by the 1/10 scale model experiment. The full vehicle model is made by means of multibody dynamics software SIMPACKTM. Both the experiment and simulation results show that the proposed inverse tread with independently rotating wheels have good performance. Running stability and curving ability of the proposed inverse tread for independently rotating wheels can be realised by using the semi-active yaw damper.

Theoretical and experimental analyses on stabilization of hunting motion by utilizing the traction motor as a passive gyroscopic damper

The wheelset on a railway vehicle experiences the problem of hunting motion, the onset of which occurs when travelling above the associated critical speed. This is known as a flutter-type self-excited oscillation resulting from non-conservative contact forces acting between the wheels and rails. Traditional methods for preventing hunting motion while running on a straight rail include using bolsters, yaw dampers, or stiffer supports. However, these methods decrease the running performance on a curved rail. To enhance the running performance on both straight and curved rails, we propose using a gyroscopic damper. Until now, a gyroscopic damper has been theoretically and experimentally shown to increase the critical speed for hunting motion. This control method does not need state feedback control, but is not a passive control method, because the gyroscope is rotated by an additional actuator provided separately from the traction motor. In practice, the weight increase from the additional actuator has been a problem in applying this control method. In this study, using the traction motor itself as a passive gyroscopic damper, a new stabilization control mechanism is proposed that eliminates the need for an additional actuator to rotate the gyroscope. An analytical model of a single railway vehicle wheelset was introduced at a scale corresponding to the experimental equipment. From the eigenvalue analysis, it was found that the critical speed increased with an increase in the rotor speed of the gyroscopic damper. Experiments were conducted using a simple apparatus consisting of a roller rig and a two-degree-of-freedom wheelset with a gyroscopic damper that has a mechanism equivalent to what is proposed. The results experimentally validate the proposed passive gyroscopic damper for the stabilization of hunting motion.

Dynamics of three-axle-one-unit vehicles with self-steering single axle

This paper proposes a new rail vehicle concept: a ‘three-axles-one-unit’ vehicle, with a self-steering single axle. Usually, a single-axle vehicle requires a short and wide car body, which is a system design of the next generation of railway vehicles. The authors propose a new ‘three-axle-one-unit’ vehicle steering a single-axle truck for the railways. This proposed vehicle uses three trucks and has the standard body length of a conventional train. It has the merit of decreasing elastic-body vibration by using a lightweight car body and by setting a truck in the middle of the car body. This system design can provide high performance with respect to stability, curving performance, and axle load limitation. Analyses were made with multi-body dynamic simulations and the basic characteristics were cleared. Finally, 1/10-scale model was made and tested. The proposed vehicles potential for high performance was proved from running experiments, including curving.