The Research Of Variable Digital Filter Based On FPGA

With the rapid development of China’s high-speed railway, people’s life is more and more convenient. Meanwhile, the railway traffic safety, comfort and stability concerns become stronger. As the excitation source of the vehicle-track coupling system, the track irregularity has a great influence on the dynamic vehicle vibration. Research about the track inspection variable digital filter is an important part of irregularity signal processing systems, which is directly related to the vehicle safety, stability studies in the vehicle-track coupling system.Countries, such as Germany, USA, Japan, France and others have developed distinctive variable digital filter in the track irregularity signal detection system. According to current situation of China’s railway operation, the advanced GJ-5track inspection system is designed based on the introduction of foreign detection technology, in which the track irregularity signal processing system is an analog-digital cascade hybrid system. According to the analog anti-aliasing filter structure and characteristics in the hybrid system, the corresponding variable digital filter algorithm is studied in this paper. Both the hardware and software simulation of the algorithm are conducted to demonstrate the effectiveness in engineer application of the proposed method.First of all, this paper introduces the basic principle of digital filter design, development platforms, design methods, design processes, and a brief analysis of track irregularity detection principles, including track irregularity detection methods, detection mode and overall detection programs based on the track inspection variable digital filter theory. Thus, it leads to the role of the variable digital filter in track irregularity signal processing system, while detailing the shift change filter algorithm derivation. Since the filter order and the number of filter coefficients are so low that the parallel filter structure is selected in this paper. The variable digital filter is divided into five basic modules to implement filter algorithm based on FPGA, including the clock control module, shift input module, weights update module, multiplier module, as well as parallel cumulative output module.Finally, the variable filter algorithm for track inspection is tested respectively on the platform of MATLAB software and FPGA hardware. The comparative simulation results verify both the effectiveness and reliability of the filter algorithm based on FPGA implementation.