本文選題：超聲信號(hào) + EMD��； 參考：《南京郵電大學(xué)》2017年碩士論文

【摘要】：超聲檢測(cè)技術(shù)憑借穿透力強(qiáng),靈敏度高,設(shè)備輕便等優(yōu)點(diǎn)被廣泛應(yīng)用于現(xiàn)代工業(yè)各個(gè)領(lǐng)域中。在金屬構(gòu)件的超聲探傷過(guò)程中,我們主要是通過(guò)分析接收到的多重超聲信號(hào)來(lái)對(duì)缺陷進(jìn)行定位、定量、定性分析,然而目標(biāo)信號(hào)往往都夾雜在噪聲等一些干擾回波中,影響了我們對(duì)有用信號(hào)的準(zhǔn)確判斷,所以要想得到清晰有效的目標(biāo)信號(hào),必需對(duì)接收到的多重超聲波進(jìn)行加工和預(yù)處理,因此研究多重超聲信號(hào)的處理分析技術(shù),具有非常深遠(yuǎn)的意義。多重超聲信號(hào)處理技術(shù)研究主要集中于對(duì)采集到的信號(hào)進(jìn)行噪聲處理和目標(biāo)信號(hào)特征提取這兩個(gè)方面。由于多重超聲信號(hào)屬于非穩(wěn)態(tài)的時(shí)變脈沖信號(hào),分析研究這類信號(hào)時(shí),需要獲取其瞬時(shí)頻率信息,因此本課題從適合非線性非穩(wěn)態(tài)信號(hào)分析和處理的小波變換方法和經(jīng)驗(yàn)?zāi)B(tài)分解方法(Empirical Mode Decomposition,EMD)入手,在研究上述兩種時(shí)頻分析方法的根本上,重點(diǎn)對(duì)這兩種方法應(yīng)用在多重超信號(hào)處理中進(jìn)行分析研究,并進(jìn)行了比較。實(shí)驗(yàn)仿真結(jié)果證明了EMD方法根據(jù)信號(hào)本身不同尺度的波動(dòng)或趨向一層層解析出來(lái),對(duì)其進(jìn)行平穩(wěn)化處理,特別適合非線性非穩(wěn)態(tài)信號(hào)的分解處理。在上述研究的基礎(chǔ)上,本文提出了基于EMD的多重超聲回波閾值去噪新方法,并且利用仿真實(shí)驗(yàn)表明采用新方法去噪后的信號(hào),信噪比明顯提高,均方誤差減小,平滑度提高,去噪效果好于傳統(tǒng)的去噪方法。最后提出基于能量算子的多重超聲信號(hào)時(shí)間識(shí)別方法,利用能量算子提取降噪后信號(hào)包絡(luò),最后對(duì)包絡(luò)進(jìn)行參數(shù)估計(jì),實(shí)驗(yàn)證明,信號(hào)的降噪預(yù)處理使得該算法適用于低信噪比的狀況下,而且基于包絡(luò)的參數(shù)估計(jì)減少了計(jì)算量,精度也得到了提高,具有良好的工程應(yīng)用性。
[Abstract]:Ultrasonic testing technology has been widely used in various fields of modern industry by virtue of its strong penetration, high sensitivity and portable equipment.In the process of ultrasonic flaw detection of metal components, we mainly analyze the received multiple ultrasonic signals to locate, quantify and qualitatively analyze the defects. However, the target signals are often mixed in some interference echo such as noise.In order to get a clear and effective target signal, we must process and preprocess the received multi-ultrasound signal, so we study the processing and analysis technology of multi-ultrasound signal.Has very profound significance.The research of multiplex ultrasonic signal processing mainly focuses on the noise processing of the collected signal and the feature extraction of the target signal.Because the multiplex ultrasonic signal belongs to the non-steady time-varying pulse signal, it is necessary to obtain the instantaneous frequency information when analyzing and studying this kind of signal.Therefore, this paper starts with wavelet transform method and empirical mode decomposition method, which is suitable for nonlinear unsteady signal analysis and processing, and studies the fundamental of these two time-frequency analysis methods.The application of these two methods in multiplex supersonic signal processing is analyzed and compared.The simulation results show that the EMD method is suitable for the decomposition of nonlinear unsteady signals.Based on the above research, a new method of multi-echo threshold de-noising based on EMD is proposed. The simulation results show that the signal-to-noise ratio (SNR), mean square error (MSE) and smoothness of the signal denoised by the new method are obviously improved, the mean square error is reduced and the smoothness is improved.The denoising effect is better than the traditional denoising method.Finally, an energy operator based time recognition method for multiple ultrasonic signals is proposed. The envelope of the signal is extracted by energy operator, and the parameters of the envelope are estimated, which is proved by experiments.The pre-processing of signal denoising makes the algorithm suitable for low SNR, and the parameter estimation based on envelope reduces the calculation cost and improves the precision. It has good engineering application.
【學(xué)位授予單位】：南京郵電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB559;TN911.7

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