| Pipelines play an important role in transporting oil or natural gas because of their unique advantages.However,the long-term operation will cause problems such as aging and corrosion of the pipeline,resulting in thinning of the pipe wall and subsequent fracture or perforation.Pipeline leakage accidents occur frequently,causing major economic losses and environmental pollution.Realizing the monitoring and fault diagnosis of pipelines by means of remote detection is a growing application requirement and the direction of automation development.Ultrasonic guided wave is an emerging non-destructive testing technology in recent years.It realizes rapid global detection of the pipeline by exciting and receiving ultrasonic guided waves at a certain position in the pipeline.However,when pipelines are inspected at an actual industrial site,due to the large size of the pipeline network,guided wave detection devices usually have multiple probes,which usually generate a huge amount of data.It is necessary to consider and solve the problem of compression of the pipeline ultrasonic signals.Firstly,a system scheme for remote pipeline guided wave detection was proposed for the above problems,and an experimental system for pipeline guided wave detection was set up,which mainly involved the design optimization of guided wave transducers and the configuration and debugging of each device.This system can be effective.Motivates the reception of multi-modal pipe guidance signals.On this basis,an ARM-based embedded detection platform was further designed based on the remote detection requirements to realize the acquisition and processing of pipeline guided wave data and the remote transmission of GPRS wireless network.Secondly,the characteristics and mathematical model of ultrasonic guided wave signal in pipeline are analyzed.Based on the principle of data compression correlation and comparison of various compression algorithms,a two-level compression scheme based on wavelet processing and LZW is proposed.The signal is preprocessed to achieve primary compression and LZW coding is used for lossless compression.Based on the implementation of the basic algorithm,the influence of the steps and parameters of the algorithm on the compression result is further analyzed,and the algorithm is optimized in terms of storage structure,matching length coding,and dynamic threshold.Finally,guided wave detection experiments are conducted on pipelines with different loss states,and the collected data are compressed.The compression performance is analyzed and summarized using the compression evaluation index.The results prove that the method can achieve higher compression ratios.In order to determine the influence of compression process on defect detection and evaluation,the defect signal analysis of the decompressed data of guided wave signal is further analyzed,including detection,positioning and modal analysis.The results also indirectly reflect the correctness of the compression reconstruction process. |
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