Optimization Design of Anti-aliasing Filter for the Stability and Instability Detection Device of EMU

Abstract

In the transmission process, acceleration signal collected by the stability and instability detection device of EMU is easily interfered due to the long wiring and complex electromagnetic environment. If the interference signal is not fully suppressed, it is easy to produce aliasing phenomenon in the sampling process of analog conversion, resulting in false alarms or missing alarms, and affecting driving safety. The traditional anti-aliasing filter method uses analog high order (5~7 order) low pass filter to remove the interference signal outside the effective bandwidth. Although it meets the anti-aliasing requirement, it has some problems such as complex circuit, poor consistency and inconvenient parameter modification. Aiming at the problems, an improved digital-analog hybrid anti-aliasing filter scheme is proposed. Firstly, frequencies of aliasing points in the sampling process are improved by high-order over-sampling, so that the complexity of the analog filter circuit can be greatly reduced to the first-order one. Then, a digital FIR low-pass filter is used to remove the redundant signals brought by the over-sampling process. Test results show that the performance of the stability and instability detection device by the improved scheme is basically consistent with that of the one by pure hardware scheme, which meets the requirements of practical applications. Meanwhile, the problems of consistency and flexibility of high-order hardware filter circuit in traditional design are solved.

Keywords

• anti-aliasing
• oversampling
• digital filter
• multiple unit train
• stability and instability detection