本文選題：Barker碼 + MIMO�。� 參考：《南京信息工程大學(xué)》2014年碩士論文

【摘要】：液位超聲測量方法的準(zhǔn)確性是超聲測量領(lǐng)域中的一個重要問題,為此,本文基于MIMO超聲測量系統(tǒng)的基礎(chǔ)之上實現(xiàn)動態(tài)液位測量,并從信號的角度提出了測量誤差的補(bǔ)償方法,進(jìn)一步提高動態(tài)液位狀態(tài)下的測量準(zhǔn)確性。 本文首先研究單通道編碼發(fā)射的超聲測量系統(tǒng)誤差來源并進(jìn)行了分析,假設(shè)測量誤差來源于回波信號波形的畸變,回波信號除了在時間上被延遲外,信號幅度上是由于噪聲干擾影響而產(chǎn)生改變,碼元寬度上是由于聲波傳播非線性因素影響產(chǎn)生的改變,為此,研究碼元寬度變化引起的測量誤差問題,并在超聲測量過程中,先估計碼元寬度的增加量,再對測量結(jié)果進(jìn)行相應(yīng)的誤差補(bǔ)償。除此之外,在測量之前,采用自適應(yīng)濾波器對回波信號進(jìn)行平滑,濾除噪聲成分,獲得較好的回波信號波形,實驗仿真結(jié)果證明了該方法的可行性,并獲得了較好的結(jié)果；其次,對常規(guī)的單通道超聲液位測量方法在動態(tài)液位測量的準(zhǔn)確性存在的問題進(jìn)行了分析,提出了基于Barker碼發(fā)射的MIMO超聲測量方法,并對其構(gòu)成的主要關(guān)鍵技術(shù)進(jìn)行介紹,如陣元陣列結(jié)構(gòu)設(shè)計、發(fā)射信號波形優(yōu)化、合成聚焦技術(shù)、脈沖壓縮及通道分離系統(tǒng),仿真并構(gòu)建實際的MIMO超聲測量系統(tǒng)進(jìn)行了相關(guān)驗證,證明了采用Barker碼發(fā)射的MIMO超聲測量方法可以有效的提高超聲測量準(zhǔn)確性,改善測量精度,優(yōu)于傳統(tǒng)的單通道編碼發(fā)射的超聲測量方法；再次,結(jié)合Barker編碼發(fā)射的單通道超聲液位測量系統(tǒng)的誤差補(bǔ)償方法,對波束合成后的信號碼元寬度進(jìn)行估計,并利用Barker碼發(fā)射的單通道超聲測量誤差補(bǔ)償方法進(jìn)行測量結(jié)果修正,也獲得了較好的測量結(jié)果,并提高了超聲測量精度。在Barker碼發(fā)射的MIMO超聲測量系統(tǒng)中,并未采用自適應(yīng)濾波器,主要是因為在對回波信號進(jìn)行合成處理時,在信號同相位處,信號合成處理對噪聲成分起到了平均處理作用,“削弱”了噪聲成分對超聲測量結(jié)果的影響,此外,也對引起B(yǎng)arker碼發(fā)射的MIMO超聲液位測量誤差的其它因素進(jìn)行研究,包括采樣精度、液位波動幅度過高,為Barker碼發(fā)射的MIMO超聲測量系統(tǒng)構(gòu)造提供了一定的理論基礎(chǔ)。最后,通過實驗結(jié)果證明,采用Barker碼發(fā)射的MIMO超聲測量方法不僅可行,而且,結(jié)合相應(yīng)的測量誤差補(bǔ)償方法,可以提高超聲測量精度,改善測量系統(tǒng)穩(wěn)定性。實驗仿真結(jié)果表明：當(dāng)回波信號碼元寬度變化時,采用新方法對設(shè)置液面空間采樣點(diǎn)的測量誤差在±0.06cm之間,通過最小二乘擬合法進(jìn)行修正后得到測量誤差在±0.015cm之間；當(dāng)被測液面波動時,若液面波動平均速度v1.67m/s,采用直接多普勒頻移補(bǔ)償法進(jìn)行速度補(bǔ)償,若液面波動平均速度v1.67m/s,采用多支路多普勒補(bǔ)償法進(jìn)行速度補(bǔ)償。
[Abstract]:The accuracy of liquid level ultrasonic measurement method is an important problem in the field of ultrasonic measurement. In this paper, the dynamic liquid level measurement is realized based on MIMO ultrasonic measurement system, and the compensation method of measurement error is proposed from the point of view of signal. The accuracy of dynamic liquid level measurement is further improved. In this paper, the error sources of single-channel coded ultrasonic measurement system are studied and analyzed. It is assumed that the measurement error originates from the distortion of echo signal, which is delayed in time. The amplitude of signal is changed by noise interference, and the width of symbol is changed by nonlinear factor of acoustic wave propagation. Therefore, the measurement error caused by variation of symbol width is studied, and in the process of ultrasonic measurement, The increment of symbol width is estimated first, then the measurement result is compensated accordingly. In addition, before the measurement, adaptive filter is used to smooth the echo signal, filter the noise component, and obtain a better echo signal waveform. The experimental results show that the method is feasible and the better results are obtained. Secondly, the problems existing in the accuracy of the conventional single channel ultrasonic liquid level measurement method in dynamic liquid level measurement are analyzed, and the MIMO ultrasonic measurement method based on Barker code is proposed, and the main key technologies are introduced. For example, array structure design, waveform optimization of transmitting signal, synthesis focusing technology, pulse compression and channel separation system, simulation and construction of the actual MIMO ultrasonic measurement system are verified. It is proved that the MIMO ultrasonic measurement method using Barker code can effectively improve the accuracy of ultrasonic measurement and improve the measurement accuracy, which is superior to the traditional single-channel coded ultrasonic measurement method. Thirdly, Combining the error compensation method of single channel ultrasonic liquid level measurement system with Barker code, the width of signal number element after beam-forming is estimated, and the measurement result is corrected by using the single channel ultrasonic measurement error compensation method which is transmitted by Barker code. Good results are obtained and the accuracy of ultrasonic measurement is improved. In the MIMO ultrasonic measurement system transmitted by Barker code, the adaptive filter is not used, mainly because when the echo signal is synthesized, at the same phase of the signal, the signal synthesis process plays an average role in processing the noise component. The effect of noise components on ultrasonic measurement results is "weakened". In addition, other factors causing MIMO ultrasonic level measurement error caused by Barker code transmission are studied, including sampling accuracy and excessive fluctuation amplitude of liquid level. It provides a theoretical basis for the construction of MIMO ultrasonic measurement system based on Barker code. Finally, the experimental results show that the MIMO ultrasonic measurement method based on Barker code is not only feasible, but also can improve the accuracy of ultrasonic measurement and improve the stability of measurement system. The experimental results show that when the width of echo signal is changed, the measurement error of the sampling point in liquid level space is 鹵0.06cm by using the new method, and the measurement error is between 鹵0.015cm by the least square fitting method. When the measured liquid level fluctuates, if the average velocity of the liquid surface fluctuation is v1.67 m / s, the direct Doppler frequency shift compensation method is used to compensate the velocity, and if the average velocity of the liquid surface fluctuation is v1.67 m / s, the multi-branch Doppler compensation method is used to compensate the velocity.
【學(xué)位授予單位】：南京信息工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TB551

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