Phase estimation method of ultrasonic transducers

The phase estimation method of time delay estimation is a practical method to improve the accuracy of ultrasonic delay estimation. Based on the fact that for a simple harmonic, the fourier transform (DFT) can be used to calculate its fourier coefficient corresponding to the resonant frequency, and thereby determining the phase shift of the simple harmonic with respect to the reference point. The complexity of this calculation depends mainly on the relationship between the simple harmonics and the sampling rate. Appropriate selection of the sampling rate can simplify the calculation of the fourier coefficients. If the moment of the sampling is strictly synchronized with the timing at which the ultrasonic transducers transmits the signal, then the phase shift between the transmitting signal and the receiving signal can be estimated by calculating the phase shift of the echo signal with respect to the sample.

When the propagation distance of the sound wave is greater than or equal to the wavelength of the sound wave, that is, the phase shift Δ> 2c, it is difficult to judge the actual phase shift, which is usually called the phase blur phenomenon. Since the operating frequency of the ultrasonic wave is > 20 kHz and its wavelength is < 17 mm, the measurement range of ultrasonic distance transducer is directly using the phase shift method must be less than 8.5 mm. For the on-board ultrasonic range finder, this small range detector has no practical application value. The proposing hybrid delay estimation method can solve the phase ambiguity problem and improve the ranging accuracy. The algorithm calculates the envelope correlation function and the phase shift to estimate the range time. Experiments have shown that the measurement error is less than 1 mm within the 1M measurement distance. The range time of the hybrid delay has estimation method. The proposing phase shift detection method based on the double-sideband (DSB) amplitude modulation method uses a low-frequency signal to modulate the ultrasonic frequency pulse excitation signal by appropriately selecting the modulation parameter, the ultrasonic frequency can be replaced by the low-frequency signal, thereby the range of the phase shift detection method is greatly expanded,and unique to the phase shift detection method is retained. For the large-range ultrasonic ranging system, not only the requirements for the distance and directivity of the ultrasonic sensor are put forward, but also the ultrasonic ranging system can quickly measure the distance of the target.

The development of ultrasonic range finding sensor and positioning technology, ultrasonic ranging and positioning technology is the edge technology discipline formed by the intersection of acoustic and instrumental science. It mainly studies how to use ultrasonic ranging sensor to realize the positioning problem of three-dimensional space targets. The ultrasonic ranging and positioning system is consisting of ultrasonic transducer, ultrasonic transmitting and receiving circuit, and microcomputer information processor has been widely used in various fields such as industry, transportation, and national defense. This paper discusses the development of vehicle active anti-collision control system based on multi-sensor information fusion in foreign countries, and participates in the paper published during the development of automobile anti-collision system. In these in-vehicle safety driving assistance systems, the ultrasonic distance sensor is mainly used to sense the road conditions of the front, rear, left and right of the vehicle to prevent accidental collision accidents when the vehicle is turning or changing lanes. They are on-board ultrasonic range finder developed by some universities and research institutes in China. The detection range of the forward-looking ultrasonic range finder is less than 10m, and the detection range of the rear view and peripheral visiting ultrasonic range finder is no more than 5m. The detection range of the short-range scanning radar mentioned (within 20m around the vehicle) is quite different. It can be seen that it is very necessary to develop a large-distance ultrasonic sensor, which will play a positive role in the development of the anti-collision warning system for domestically produced vehicles in the future.