Track switches (also known as "point" or "turnout") are essential to the railway system and provide route flexibility by allowing vehicles to move between tracks on the network. However, the single actuators in the current switch technology mean that a single actuator fault will result in the failure of the switch (and the concomitant delays to trains waiting to pass the switch). This paper focuses on providing redundant actuation through an approach known as High Redundancy Actuation (HRA), which might allow track switches to remain operational after failure in actuator elements. The paper also proposes the use of closed-loop control (track switches are usually operated open-loop). In the paper, we introduce a model of a C-type switch and validate it against results from a previous paper. This model is then used combined with an HRA of nine elements (3x3). Two closed-loop controllers are then proposed for each of the single actuator and the HRA actuator system. The findings indicate that closed-loop control on its own has some benefits. However, when combined with HRA, the resulting system is able to tolerate a number of faults in the actuator subsystems, creating an effective graceful degradation rather than the sudden failure with a traditional single actuator.

This paper proposes a new approach to the dynamic modelling of railway track switches. The approach results in a model which faithfully reproduces the dynamic bending of the switch blades, allows simulated actuators (forces) to be applied along the length of the rails and can be simulated in times that are an order of magnitude faster than similar models in multi-body dynamics software (such as Simpack). These are the main contributions that should be of use to researchers and engineers concerned with the design of switches and their actuation mechanisms. First, an actuator model is developed; then the switch blade FEA (Finite Element Analysis) model is developed and validated against static bending predictions; the two are then combined and validated against the dynamic and steady-state predictions from a validated Simpack model. The complete model can be found here: https://doi.org/10.25500/edata.bham.00000884 .

This paper provides an event-triggered finite-time adaptive bounded controller for attitude tracking of spacecraft formation flying under external disturbances and limited communication. To facilitate the realization of bounded control, a novel full-order terminal sliding mode surface is established according to the hyperbolic tangent function. To reduce the communication frequency among formation members, an event-triggered control strategy that can converge to zero in finite time is investigated based on the full-order sliding mode surface. Under the proposed control strategy, the spacecraft only send their information to neighboring spacecraft when the trigger error exceeds the defined threshold. Rigorous theoretical analysis provides that finite-time convergence and Zeno-free are achieved under the proposed controller. Finally, numerical simulations are exhibited to illustrate the effectiveness of the proposed control law.