Determining Ultrasound Arrival Time by HHT and Kurtosis in Wind Speed Measurement

Shiyuan Liu,Zhipeng Li,Wei Zhang,Tong Wu

doi:10.3390/electronics10010093

Shiyuan Liu, Zhipeng Li + Show 2 more

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https://doi.org/10.3390/electronics10010093

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Abstract

The determination of ultrasonic echo signal onset time is the core of performing the time difference method to calculate wind speed. However, in practical cases, background noise makes precise determination extremely difficult. This paper carries out research on the accurate determination of onset time, exploring the advantages of an improved method based on the combination of Hilbert-Huang Transform (HHT) and high-order statistics (kurtosis). Performing Hilbert-Huang Transform to the received wave is aimed at determining a rough arrival time, around which a fixed size of data is extracted as initial sample to avoid a false pick. Then the fourth-order kurtosis of a smaller sample, extracted successively by a moving window from the initial sample, is calculated. The minimum point corresponds to the initial onset time. This approach was tested on a real ultrasonic echo signal dataset, acquired in a wind tunnel with an ultrasonic anemometer. The proposed method showed satisfying results in both ideal cases and low signal-to-noise ratio (SNR) environment, compared with traditional onset time determination approaches, including Akaike Information Criterion (AIC-picker), Short-term Average over Long-term Average (STA/LTA), and Teager-Kaiser energy operator (TKEO). The experimental results acquired by the HHT-kurtosis method demonstrated that the proposed method possesses a high accuracy.

Highlights

During the process of wind tunnel experiment, wind speed is one of the most critical parameters that needs to be accurately measured [1,2]
We propose an improved method based on the combination of Hilbert-Huang Transform (HHT) and kurtosis characteristic function
The purpose of this study is to develop an effective method for detecting the arrival time of ultrasonic signal, which is of vital importance during the wind speed determination

Summary

Introduction

During the process of wind tunnel experiment, wind speed is one of the most critical parameters that needs to be accurately measured [1,2]. Precise determination of wind speed can be of great significance in many fields relating to weather forecasting, power generating, farming, engineering, and manufacturing [3,4]. Mechanical anemometers can be damaged, especially for the rotating component inside. This component needs an initial speed to rotate due to its inertia, it is almost impossible to measure low-speed wind. Due to the low accuracy of the pressure sensor, it is exorbitantly consuming to design a pitot tube anemometer to precisely detect the pressure difference of low-speed wind. Ultrasonic anemometer is a reliable method with a wide measurement range and no start-up wind speed limitation while being applied in the field of wind speed determination

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