Research On Embedded Remote Crack Monitoring System Of Bridge Based On GPRS And EMD

Crack is one of important signs of a bridge health status, and it is also a major source of bridge security status deterioration, so it has great significance to real-time monitor it. With a rapid development of video scanning technology, computer technology, wireless transmission technology and signal analysis technology, a new look is shown in crack monitoring. Some key technologies of a remote monitoring system for bridge crack proposed by author's tutor and his collaborators are studied in this paper. Several key features of the system are achieved, and their effectiveness is verified.A new signal decomposition method - empirical mode decomposition method (EMD) is used in the system for crack image processing. EMD is the core technology of signal processing method - Hilbert-Huang transform (HHT), it directly against the data and can adaptively decompose one-dimensional signal into finite number of intrinsic mode function (IMF). The EMD method is based on the scale of data's local characteristic, rather than other established functions (such as cosine function in Fourier transform), and thus the EMD method can be applied both to stationary signals and non-stationary signal.There are several key technologies in EMD - fitting envelope, termination criteria technology, end effect suppression technology etc. The quality of these techniques determines the reliability and validity of EMD. To suppress EMD end effect, a new inhibition method– the intrinsic wave matching and prediction method is successfully implemented in this paper based on intrinsic wave matching. The effectiveness and advancement of the method is illustrated by cleverly constructed simulated signal and actual measured signal.Real-time on-line image signal processing is required in bridge crack monitoring, but there is no real-time EMD method at present. To solve this problem, we present a real-time EMD method - overlapping segments - means inheritance EMD method (referred to as the SS-MIEMD) by using several special techniques such as signal segment, mean inheritance, overlap processing etc., A dynamic, continuous, rapid and high-precision EMD treatment can be achieved by this method. The effectiveness and feasibility of the method is validated by a number of simulated measured signals, the algorithm is also extended to the two-dimensional EMD method.At the same time, the embedded technology, GPRS technology is introduced into BCMSBVF and an embedded remote crack monitoring system of bridge based on GPRS and EMD is constructed and initial realized in the paper. The system has simple structure and is flexible to use. It can achieve the function of remote bridge video image collection, information dissemination and disaster alarm. The experiment under laboratory condition verifies the effectiveness of the system.