Research On Key Technologies Of Bridge Monitoring Based On Interferometric Radar

With the rapid development of urban road traffic in China,a large number of bridges are in an over-operational state.Under the influence of external factors,their structures may experience small deformations or even vibrations,which can lead to accidents such as bridge damage and collapse,causing personal injury and property losses.Therefore,it is urgent to conduct regular deformation monitoring and health and safety assessments of bridges.This thesis focuses on the study of building micromovement monitoring technology based on microwave sensing using interferometric radar.The main research includes deformation measurement technology based on phase inversion,phase unwrapping algorithm based on path tracking,and the design and experimental verification of miniaturized millimeter-wave interferometric radar.The main contents of this thesis are as follows:In view of the limitations of conventional monitoring techniques,such as high assembly costs,low level of intelligence,and poor all-weather working ability,this master’s thesis proposes the use of interferometric radar technology.Based on the principle of distance Doppler algorithm,a simulation of a 1000*1000 scene area is conducted,and the images obtained from antenna A and antenna B are used to generate an interferogram.The interferogram is processed and analyzed through image registration,removal of flat-earth phase,noise filtering,phase unwrapping,and phase inversion to obtain the deformation of the measurement position.After a series of processing,a registration rate of 99% can be achieved,and small deformation values can be extracted.This method has the advantages of high temporal and spatial resolution,fast processing,and is not affected by external environmental factors.In response to the problem of large residual point data and the easy formation of closed curves in the branch-cut algorithm,an improved branch-cut algorithm is proposed in this master’s thesis.This improved algorithm assigns a trust value to each residual point,restores the residual points with high trust values to normal pixels,and then combines the residual points to minimize the total length of the branch-cut line.This improved branch-cut algorithm not only reduces the number of residual points to improve the speed of phase unwrapping,but also improves the accuracy of phase unwrapping,thus solving the problem of isolated islands and achieving the accurate extraction of echo phase.Based on the above research,a high-precision prototype of an interferometric radar deformation monitoring system was developed.The hardware and software design of the prototype were carried out to achieve small size,high versatility,and low cost.Multiple field experiments were conducted using the prototype,which can perform deformation monitoring in various scenarios within a range of 0.5-100 m.The detection accuracy can reach the millimeter level,which lays a foundation for practical engineering in application.