Ultrasonic Spread Spectrum Velocimetry Study

With the development of transportation industry, traffic accident is on the increase. Since most accidents are caused by overspeed, it is important to monitor the vehicles'transport speed for the drivers'securities. Aiming at the insufficiencies in measuring accuracy and operating range of most domestic velometers, this dissertation is focused on the research of ultrasonic spread spectrum speed measurement.1. The operating principle and implement method of ultrasonic spread spectrum speed measurement are studied. Based on the research of the respective characteristic of speed measurement sensors, several kinds of ultrasonic speed measurement methods are provided. Aiming at their insufficiencies in measuring accuracy and operating range, a new method of ultrasonic spread spectrum speed measurement is proposed. The operating principle is analyzed in detail and the feasibility of this method is demonstrated in theory.2. A hardware platform of ultrasonic spread spectrum speed measurement system is set up. According to the practical speed measuring requirement, system parameters are determined such as code period, code rate, and frequency resolution. BF531 is selected as the system core processing unit based on the analysis of computational complexity and the correlative parts of hardware design are described.3. The software design of ultrasonic spread spectrum speed measurement system is introduced. The generating programs of m series and band-limited PN (pseudo noise) series are designed based on the research of correlative arithmetic. According to the testing principle and parameter characteristic of echo signal, decimation filter and digital correlator group are provided. The function of target detection and speed measurement is also provided in DSP software.4. The performance ultrasonic spread spectrum speed measurement system is tested by experimentation and the error analysis is also done.