# Realisation of a Novel Functionally Redundant Actuation System for a Railway Track-Switch
## 6 Conclusions and Future Work  
This paper has focussed on the development and test of a new track-switch actuation system, which has been designed to allow fault-tolerant operation of a railway track switch. Development of the dynamic design model which is a co-simulation between Simulink and Simpack has been discussed; links have been made to its use in the design process. In particular, the model's use for the design of the control system has been covered. Both simulation and experimental results have been compared--showing that the model is indeed representative of the main dynamic response of the actuation and moving rails in the real application. Comprehensive results for the resulting switch and actuation system, installed and tested in a real railway environment, are presented and discussed. The implementation tests showed that the proposed closed-loop control algorithm achieves effective rail switching which met the specified control requirements for the system. The different tests of the novel switch, in the rail network, has been mainly achieved by three stages. The implemented scenario has been started by operating the track switch using all three actuators, then using two active bearers and finally, with only a single actuator to test robustness to faults. Overall the experimental tests show the rail switching operation is achieved by any two out of the three bearers, and also by every individual bearer. On both through and diverging routes (Normal/Revers switch positions), the experiential results also show that the rebalancing of switch rail loads over each actuator of the track switch is crucial to the success and evolution of this innovation switch. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Switch** \\ **Mode** \\ **Operation** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Actuators** \\ **(Bearers) Names** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Settling** \\ **Time (s)** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Steady-State** \\ **Error (\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Overshoot** \\ **(\({}^{\circ}\))** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Verant (A)—** \\ **for Each Motor** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Peak of Output** \\ **Mechanical Power (kW)—** \\ **for Each Actuator** \\ \end{tabular} } \\ \cline{5-8}  & & & & & & **Side-A** & **Side-B** \\ \hline \multirow{3}{*}{\begin{tabular}{c} Triple \\ bearers \\ \end{tabular} } & B1 \& B2 & 5.1 & 0 & 0 & 11.8 & 4.5 & 0.49 \\  & B2 & 5 & 0 & 1 & 2.31 & 11.72 & 0.48 \\  & B3 & 5.1 & 0 & 1 & 13.15 & 11.71 & 0.85 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Double \\ bearers \\ \end{tabular} } & B1 \& B3 & 5 & 0 & 1 & 10.39 & 7.66 & 0.56 \\  & B3 & 5 & 0 & 0 & 13.07 & 11.34 & 0.99 \\ \cline{1-1} \cline{2-8}  & B2 \& B2 & 5.1 & 0 & 0 & 6.09 & 7.69 & 0.49 \\  & B3 & 4.9 & 0 & 0 & 13.16 & 8.63 & 0.72 \\ \cline{1-1} \cline{2-8}  & B1 \& B2 & 4.9 & 0 & 1.2 & 15.3 & 3.96 & 0.77 \\  & B2 & 5 & 0 & 1.1 & 12.95 & 14.5 & 0.94 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Single \\ bearer \\ \end{tabular} } & B1 & 5.1 & 0 & 0 & 11.33 & 14.15 & 0.81 \\ \cline{1-1} \cline{2-8}  & B2 & 5 & 0 & 0 & 15.27 & 14.05 & 1.11 \\ \cline{1-1} \cline{2-8}  & B3 & 5.1 & 0 & 0 & 15.63 & 15.42 & 1.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Closed-loop performance under fault-free (triple), one out of three faults (double) and two out of three faults (single) actuation. The research described set out to redesign railway track switches to feature fault tolerance, primarily using redundancy of actuation, to significantly boost reliability and availability, whilst keeping the existing switch layout unchanged. The novel approach that has been presented used three mechatronic actuator-bearers and moved the switch rails through a motion unlike any existing track switch to facilitate passive locking.