Research On Velocity Measurement Of High-Speed Object's Braking Process

High-speed moving object's braking and deceleration performance is one of the most important indicators which tightly related to the security and reliability of the braking system. In order to provide the braking system and deceleration devices with a reliable basis, it is necessary to carry out the velocity measurement of the whole braking process.In this paper, the braking process of the quality vehicle and other large high-speed moving objects is taken as the research object. According to its characteristics like the braking process is fast, the braking distance is short and the speed range is large, the paper puts forward a multi-zone velocity measurement system based on laser screens. By using a tooth-type bar fixed on the moving object, a pair of laser diode/photodiode and a high-speed counting circuit with large dynamic range and buffer capacity, the system realizes the whole process measuring of the moving object with the velocity from high to quasi-static.The paper introduces some current methods of the velocity measurement,and their applicability to the braking process is discussed. Then detailed feasibility studies of measuring method are carried out, hardware and software are realized. The paper also analyzes the system error sources and integrates them. For the existence of some singular values, data processing methods are discussed. In the case when the space of tooth-type bar is 3mm, the system is able to guarantee the highest-speed section has 200 pulses, the largest time error is 0.125μs.The velocity error of the high-speed section is less than 0.833% while the low-speed section less than 0.334%. The field test results show that the system can accurately measure the velocity from 65m/s to quasi-static.