| Distributed vibration measurement is an important branch in the field of modern measurement and control measurement engineering.It is widely used in various fields,such as bridge and tunnel quality inspection,vibration source positioning,and engineering blasting.In practical,the data information collected by the vibration measuring nodes at different locations should be modeled and analyzed based on the consistency of time.If there is a large deviation in the time of each vibration measuring equipment node,the results of the modeling analysis will also be biased.Therefore,the clock synchronization between the nodes of the vibration measuring system is a key factor that affects the accuracy of data acquisition.Aiming at the relatively large clock deviation between the equipment nodes of the current vibration measuring system,this paper is going to analyze the commonly used clock synchronization technology via doing researches,so as to design a distributed vibration measuring with high-precision clock synchronization.The main work is as follows:(1)Considering the frequency range of signal and communication mode of distributed vibration measuring system,a design scheme of software and hardware combination of distributed vibration measuring system based on IEEE1588 protocol with clock synchronization is proposed.In terms of hardware,NUC980DK61 microprocessor which supports IEEE1588 protocol is selected as the core processor,and the Ethernet transceiver module,vibration signal measuring module,power supply module,storage module,etc.are analyzed and designed;Based on the Vx Works operating system,vibration measuring module,clock synchronization module,and remote communication are carried out.In combination,a distributed vibration measuring system with high sampling rate and high-precision clock synchronization is accomplished in this paper.(2)In the process of clock synchronization,the frequency drift rate of crystal oscillator will become faster with the temperature change.And with the commonly-used first-order Kalman algorithm to filter the clock compensation parameters,there will be serious phase delay and amplitude distortion.In this paper,combined with the temperature sensor module of distributed vibration measuring system,a self-adaptive first-order Kalman filter taking ambient temperature as the feed-forward parameter is designed,which can adjust the clock compensation parameters quickly when the ambient temperature changes,so as to reduce the range of clock deviation caused by temperature change between master clock and slave clock in the clock synchronization process.The synchronization process between master clock and slave clock is simulated based on the MATLAB software to verify the validity of the algorithm.(3)Carry out functional testing and analysis of the vibration measuring system.The physical platform is built to verify the vibration measurement function,remote network communication function and time synchronization function of the vibration measuring system,and the effectiveness of the first-order Kalman filter algorithm based on temperature is verified in hardware.At the same time,the factors affecting the master-slave clock synchronization are analyzed experimentally,which provides experimental basis for the construction of distributed vibration measuring network.After experimental verification,the maximum sampling rate of the distributed vibration measuring system can reach 128 k SPS,and the vibration signals between0～500HZ、-10V～10V could be sampled without distortion.At the same time,the clock synchronization accuracy between master and slave nodes is within 150 ns after passing through the Gigabit switch,which is far less than the minimum time interval of 7.8us between the two sampling points at the maximum sampling rate.This paper both provides theoretical and practical reference for the research of distributed vibration measuring system with clock synchronization. |
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