Design And Implementation Of Multi-point Displacement Synchronous Measurement System

Displacement and deformation may occur in time and space domain,when building is used in outside harsh environments over a long period of time.When the amount of displacement reaches or exceeds the safety criticality,it often brings catastrophic consequences,such as collapse of mines,bridges,high-rise,break of dam,etc.Thus,precise displacement monitoring is one of the most important means of preventing buildings from disastrous consequences caused by deformation.Multi-point displacement synchronous measurement system in this thesis is utilized for precise displacement monitoring of large buildings such as high-rise,dams,and provides real-time acquisition,calculation and display of the displacement generated by the building.Firstly,this thesis analyzes the displacement monitoring system based on microwave phase comparison and the displacement monitoring system based on CDMA.Thesis proposes multi-point displacement synchronous measurement system inspired by the above mention systems.The reference beacon is installed on the fixed location,and the observation beacons are installed on other locations which occur to displacements easily.The beacons were distinguished by different frequencies;they utilize a common frequency local oscillator to ensure the coherence of the intermediate frequency carrier;observation beacons employ double sideband-amplitude modulation to cancel the random phase of the sine wave by the later calculation;The receiver uses FFT algorithm to obtain the phase spectrum and amplitude spectrum of received signals,and calculates the displacement of the observation beacons relative to the reference beacon.The simulation results show that the multi-point displacement synchronous measurement system can effectively distinguish beacons,and it can accurately obtain observation beacons displacement relative to the reference beacon through the FFT conversion and post-calculation.The thesis then analyzes the parameters of SNR,FFT points,and frequency offset on the impact of the system.Secondly,this thesis introduces the development platform of multi-point displacement synchronous measurement system.Receiver includes ZedBoard development board and AD6645.AD6645 digitizes the analog signal,and sends the digital signal to the ZedBoard development board for processing and display.The chip of Zynq-7000 series integrates ARM and FPGA,and FPGA achieves the hardware circuit design while ARM implements device call and GUI display.Finally,it introduces the realization of multi-point displacement synchronous measurement system.The system includes transmitter and receiver.The transmitter includes AD9959 and Spartan-6,and Spartan-6 controls the AD9959 to generate reference beacon and observation beacons signals.The hardware circuit of the receiver includes digital down-conversion module and an FFT module.The digital down-conversion module reduces frequency offset.The FFT module realizes the conversion from time domain to frequency domain and calculates the reference beacon phase and the upper and lower sideband phases of the observation beacons.The receiver's software design mainly includes the driver and GUI.The driver realizes the communication between ARM and FPGA.The GUI reads the phase values of the beacons by calling the peripheral device,then calculates and displays the displacement of the observation beacons relative to the reference beacon.