Fault Analysis and Optimization Scheme of Insufficient Air Braking in Metro Train

［Objective］ Currently, when metro trains operate on mainline tracks under the ATO (automatic train operation) mode and stop at stations, the rail transit signaling system must confirm that all braking signals are applied previously before issuing a door-opening command, which ensures passenger safety. Failure to issue this command would prevent the door system from opening in coordination, significantly impacting mainline train operation. Therefore, it is essential to explore new optimization solutions to enhance train operational service quality. ［Method］ Using a real fault case on Ningbo Rail Transit Line 4 as research object, where a train door failed to open in coordination due to unapplied braking during mainline operation, the problem is analyzed from multiple dimensions, including train door-opening logic, braking control principles, fault reporting logic, and data. The goal is to develop effective optimization solutions. The feasibility and reliability of the proposed solutions are verified through multiple trials. ［Result & Conclusion］ In the braking system, the optimization of braking software improves the fault reporting mechanism, significantly reducing the fault reporting rate. Additionally, enhancements to the braking application mechanism in fault scenarios effectively mitigate the negative impact of such faults on operations. For the LCU (logic control unit), the optimized software improves the output logic of the ′all braking applied′ signal, successfully preventing door coordination failures caused by braking issues. Results from multiple trials demonstrate that the optimization scheme significantly reduces fault impacts, improves the reliability of metro train operations, and enhances service quality, showcasing a high practical value.