Design Of High-speed Fiber Doppler Signal Acquisition System

In the engineering field, vibration measurement can be used to measure the dynamic characteristics of objects. The vibration technology based on the doppler effect is an important means of detection. A scheme for signal real-time acquisition and processing is proposed based on the field programmable logic gate array (FPGA) as core processor in order to solve the real-time acquisition and processing problem. In this paper, the scheme is a innovative and exploratory way to vibration signal acquisition and processing technology and The main research contents include:1. The optical system of the laser doppler vibration is designed and improved.Combining the optical heterodyne detection technique with advantages of simple and with the advantages of the coaxial optical path structure, a new kind of all-fiber laser vibration system is redesigned and improvd.2. According to model analysis of doppler signal, a scheme for signal acquisition and processing system based on FPGA is designed. And the hardware system consists of Cyclone IV’s FPGA kernel control module and outer modules such as the signal conditioning circuit, A/D circuit, D/A conversion circuit and other peripheral modules.Based on measurment accurancy of the system, each module of the hardware system is analyzed and studied. And its related devices are chosen. The schematic document is drew by use of Altium Designer software, algorithm is programmed and hardware circuit is real-time debugged by use of Quartus Ⅱ software. The changes of target velocity and displacement are obsreved on oscilloscope. And the communacation between the network communication port and PC is achieved.3. The research on the vibration signal processing algorithm. The algorithm regards the multi-cycle synchronous frequency measurment method as the core, combined with signal extraction algorithm and realized the information extraction of the vibration signal of velocity and displacement.4. The analysis of the experiment and data. The paper build the experimental validating device with the voice coil actuator, tuning forks, sound as the testing objects. The vibration measurment experiment is done. The experiment results show that the measuring range of velocity measurement in the 0.1～10 m·s-1, the measuring range of frequency is DC to 1MHz, the error of frequency measurment is 0.04%. The experiment verifies the reliability and precision of the vibration measurement system.