Study On Stability Of The Deflection Monitoring System Of Bridges Based On Laser & Image Measuring Method

Bridge is the very important component in Modern Transportation. The serious topic that Worldwide Bridge Engineering pay close attention to, is how to make sure the bridges are security on bridge operation stage. As the important basis of evaluation on bridge safety situation, bridge deflection can measure whether bridge structure deformation is in the range of bridge safety.As one of the non-measuring bridge deflection method, Laser & Image Deflection Method has many advantages, such as high measuring efficiency, precision and images information integrity. Thus, the deflection monitoring system of bridges based on Laser & Image measuring technique has been considered to be measuring tool in the monitoring process of bridge deflection. Meanwhile, as a newly emerging deflection measuring technique, the measurement data sometimes has been in unstable state when the system is used in the monitoring process of bridges deflection. How to make better research the influence of unstable factors on the system, and ensuring the system is in the stable operation on the influence of external factors, it will be the important research direction on the detection of bridges deflection.The dissertation focuses on the research of the influence of unstable factors on the system, based on the stability analysis for monitoring system of bridges deflection from actual conditions. The main research concerns on the following lists:1. Base on analysis of instability in monitoring system devices, especially making studies on the influence of measuring data due to vibration effect, relevant experiments of bridge load and vibration effect are specially designed to further proves the analysis results. Difference between normal value and abnormal value by the influence of vibration effect are analyzed through comparing the experiment results based on the methods of clustering and chart analysis. It will provide evidence for making the judgment on whether abnormal data by system acquisition is normal data. At last, according to the action characteristics of laser emitter are influenced by vibration effect, improvement advices are given to improve the system stability.2. According to the principle of monitoring system, based on a theoretical analysis of the influence of instability in monitoring system due to interference light, the changes of the data by system acquisition pre and post the influence of interference light are analyzed through comparing the experiment results, thus explaining the influence of system instability due to interference light and how to make it. The paper makes studies on digital image processing, and presents the methods of the image processing to solve the problems by the influence of main factors to image recognition and center location of laser spot. Based on making the research on common algorithms in image recognition and center location, according to difference in actual situation which the system may be applied to, the adaptive algorithms are be applied to the monitoring system.3. In combination with the practical situation of monitoring environment which the system is applied to, the paper puts the algorithms of gravity method and circle fitting into the program of system, and makes the studies on those imagines by system acquisition. Through making the comparison and analysis on the experimental data in the difference of light intensity, the corresponding conclusion is presented. The results, error analysis and the reasons of the influence of measuring accuracy are given at last.