Research On Mechanisam And Detecting Instrument Of Train's Longitudinal Impulse

With the constant development of the national railway system construction, besides high speed and high safety, high comfort is also of vital importance to improve trains riding quality. Whether trains could be manipulated steadily has a direct influence on running safety and passenger's comfortableness. The currently domestic and international researches focus on ride performance and comfort when assessing impulse grade, which. analyse mainly the transverse and vertical impulse by the amplitude and frequency characteristic of acceleration. And there isn't a uniform impulse assessing standard around the world yet. The stick-fallen method is being universally applied to measure impact by inland locomotive depots currently. However, there are a lot of disadvantages using this method which evaluates the impulse grade according to the sticks fallen that have different cross section. Hereby, the longitudinal impulse's criterion and measurement were researched in this paper to provide the theory and technique support for passenger train's comfort standard. The research task and innovation ideas included the following several respect mainly:1. The research about the norm of judging longitudinal impulse. Passenger trains' longitudinal force is always dynamic under a variety of force when running. The longitudinal impulse would be caused when the force changed vigorously, and the relative position between passengers with compartment would be changed. Under this changed status, people would be uncomfortable, but this comfortless would be different because of different sensitivity of human bodies. A new judge rule composed of the amplitude, inherent frequency and effect period of longitudinal acceleration was provided in this paper, based on studying the longitudinal dynamics of trains and human sensitivity. And general pattern of longitudinal impulse was concluded through analyzing the acceleration samples. Compared with traditional rules, the new criterion was more rational and exact, which was proved by experiments.2. The study about measuring longitudinal impact signals. Based on the technology of embedded system and virtual instrument, a new portable instrument of impulse testing was developed in this paper to sample trains' acceleration, which comprises accelerometer, conditioning circuit, data acquisition device, compact flash, touch screen and LCD monitor, and with embedded industrial computer as its kernel. This portable instrument can perform many sampling functions intelligently including acquisition, process, store and display. It was verified by experimentations that the detector achieved the functions and performance goal with high accuracy and high anti-jamming quality.3. The study about anaylsis and process methods of longitudinal impulse signal. Besides noise, there are other inevitable elements interfere the sample during the data acquisition. The sampled accelerator are mainly composed of impact accelerator signal,background noise and vibration accelerator signal. In this paper, sample signals are processed in the respect of translated physical meaning, dynamic feature decimation, digital filte, time domain and frequency domain analysis by digital signal processing and virtual instruments. A new method of extracting the longitudinal impulse signal based on the autocorrelation function was put forward. The longitudinal impulse signal was successfully stripped from vibration signal by autocorrelation analysis, and the judge accurateness of longitudinal was improved.4. The research about methods to determine longitudinal impulse. According to the three key elements, the longitudinal acceleration signal was carried out energy analysis. A complete set of methods to determine longitudinal impulse was put forward, which includes using longitudinal acceleration signal as the object for analysis, using Frequency signal analysis to determine its low-frequency characteristics, using autocorrelation analysis to detach vibration signals, and using energy analysis to determine the occurrence of longitudinal impulse.