Study On The Alarm System Of Approaching Train Based On Detection Of The Wheel/rail Driving Sound

To advance alarm the approaching train is a good method for the safeguard of maintenance builder and passerby on rail. Now, there already have some alarm systems for specialties section of short rail, such as bridge, tunnel, mine, etc. But these alarm systems are costliness, and also difficult to apply to the long rail.A method is brought forward in this paper to measure the solid state sound's changing in rail to alarm the approach train depending on the study of the law of the sound stimulated by wheel/rail and the sound diffused in the rail. It can be used not only in the short rail but also in the long rail.1. The vibration of wheel/rail stimulates sound. It finds out the connection of the PSD of rail's vertical vibration speed and the wheel/rail surface roughness ratio spectrum depending on the Remington model and the coupling of wheel's radial vibration and rail's vertical vibration. By the method of admittance measure and frequency scan, we can obtain the character frequency of 60kg rail of China, first-order frequency is 150Hz and second-order frequency is 300Hz.We can calculate the character frequency of rail horizontal vibration depending on the fixed-fixed bar model vibration equation, first-order frequency is 155Hz and second-order frequency is 3 10Hz.That proves the rail vibration is whole-vibration.2. The sound of wheel/rail diffuses in the air and in the rail. When the sound diffused in the air, the attenuation is soon because of infinitude medium of the air and the great damping of the air. And there is many interfering sound source in the air, it is difficult to judge the driving train by people's ear. The rail can be regarded as a wave-guide because of fixed size, when the sound diffused in it would follow the lawof wave-guide. The cutoff frequency of rail is higher than the frequency of the wheel/rail sound, so no hyper-order wave exists in the rail. As the rail's damping is more than the air's damping, the interfering sound source in the air can hardly affects the solid-state sound in rail. That proves that we can obtain the driving information of the train by measuring the solid-state sound in rail.3. In this paper, the DSY-1 microphone is used for measuring the solid sound in rail, whose wave band and sensitivity can suit the measure of rail's sound. According to the result of measuring the solid-state sound single of driving train, the PSD of the single by the data processing in MATLAB can be obtained. The PSD figure shows that the peak value of 300Hz has especially distinct change..4. According to the rule of the solid-state sound change in the rail, we design alarm system on the core of MCU for alarming the driving train. This system can alarm in much format, sound and light alarming or vibration alarming, etc. Moreover, it is low-powered and portable, so it can be powered by dry battery or storage battery or solar battery based on the environment. The alarm system has characteristics of anti-jamming, better reliability, high capability-price ratio, handy and durable use. Because the point is not the solid-state sound sensor fixed when a train passes by it, so the system can avoid making an wrong alarm caused by electromagnetic interference owing to long cable.