Improved curving performance using unconventional wheelset guidance design and wheel-rail interface - present and future solutions

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.