Objective The mutual cooperation between the electric braking and pneumatic braking of metro trains (hereafter referred to as "electro/pneumatic braking"), and the resulting efficiency can significantly enhance the stability and reliability of train stopping. Therefore, it is necessary to analyze and optimize the electro/pneumatic braking coupling phenomenon during metro train sliding control.
Method The vehicle's braking control principle and fault phenomena are analyzed. Taking the instance of severe sliding and the resulting various degrees of wheelset scratch phenomena on three metro trains in Xuzhou, a detailed analysis is conducted on the software data during the traction system and pneumatic braking system failures, as well as the cause of the axle speed "coupling" phenomenon. The time and manner of electric braking fade-out after the electric braking cut-off during severe sliding are investigated, to optimize and verify the electric braking fade-out function.
Result & Conclusion After cutting-off, the electric braking will reduce its force according to a certain slope to prevent excessive vehicle jerk. When encountering a severe train sliding, the actual electric braking force will completely fade out at the end of the anti-slide control, but the given electric braking force still persists for about 700 ms, thus causing the train pneumatic braking unable to perform timely slide control. This is the reason for wheel tread scratches. Appropriately shortening the electric braking fade-out time, or immediately reducing the given electric braking force to 0 upon receiving the cut-off signal, can effectively reduce tread scratches without significantly increasing thevehicle jerk risk.
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