外文翻譯--數(shù)字技術(shù)在超聲波傳感器中的應(yīng)用(編輯修改稿)
2024-09-06 17:30 本頁面
【文章內(nèi)容簡(jiǎn)介】 ceeded by the signal or its envelope. Although it has proved to be simple and cheap, this technique may suffer from poor resolution, particularly the echo pulse has been greatly attenuated.The correlation technique is a kind of more sophisticated technique for applications requiring high accuracy, which bases the ToF estimation on the search of the relative maximum in the crosscorrelation function between the transmitted signal and the echo signal. According to the index of the maximum value of the correlation function, the time delay between the two signals is obtained. The correlation function is defined as: (5)when the value of ) (hT C is the maximum, the ToF is hT . (6)Considering the procedure of the sampling data, actually, the f T estimation can be expressed in the form: (7)where h is the integer part of ) 5 . 0 / ( + T Tf , and λ is a real number in the interval ) 5 . 0 , 5 . 0 [? , a suitable measurement algorithm must be used to evaluate exactly the real number λ. It is possible to estimation the fraction number λ through a suitable interpolation technique. The secondorder approximate interpolation determines the parameter λ as: (8)the equation (1) can be expressed as: (9)4. SIMULATION AND ERROR ANALYSISIn order to validate the proposed method, a realistic simulation must be setup to mirror the characters of an actual ultrasonic sensor: assuming a sampling frequency M f = 8MHZ, an ultrasonic sensor frequency fs =550KHZ ,an ultrasonic wave speed in the medium s m v / 1390 = , the distance resolution is, according to the equation (1), . The error analysis can be implemented on the puter simulations. Systematic ponent of errors in ToF estimationThe finite sampling frequency during the procedure of the A/D conversion make the ToF estimation inaccurate,that is, the time resolution error of system is a error source for the ToF estimation. This is a systematic error,which can be thought as a function of the time the equation (5), this 39。ideal39。 resolution error can be written as: (10)that corresponds to a maximum distance error equal to mm 043 . 0 . When the ToF is a multiple of the sampling period ( λ), the error will be zero.According to the equation (6), the result obtained by puter simulations confirm that the interpolation method make the time resolution error to a minimum value. As a result, the systematic error in distance measurement can be written as follows: (11 ) Random ponent of errors in ToF estimationIn the practical applications, the existence of noise is a cause of ToF inaccuracy. We can assume that the noise is a white noise. From the viewpoint of energy, low SNR leads to high noise intensity. For th
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