Research On The Detection Method Based On Multi-frequency Ultrasound

Currently, ultrasonic detection systems mostly use pulse signal. This signal takes longtime and is not accurate enough. When SNR is low, the existing methods of distancemeasurement and obstacle recognition lack of accuracy. And the existing guidance productusually has a long detection time, the accuracy is not high, and the prompt method is not clear.This article is mainly to improve the above problems. The main contents are as follows:1. Bat echolocation system is a highly evolved system. This article points out theadvantages of bat’s multiple frequencies signal. The paper analyzed the CF and FM ultrasonicsignal, and raised the method of using both CF and linear FM signals in detection.2. Currently, people mainly use the delay estimation algorithm to measure distance.Threshold method is relatively simple, but it’s not accurate enough. Cross-correlation functionmethod is more commonly used now. But it needs the prior knowledge of the signal, andwhen SNR is low, it’s not accurate enough. The minimum mean square error adaptivealgorithm doesn’t require a priori knowledge of the signal and it can adapt to differentenvironments better. This paper raised a joint method that uses both threshold method andLMS method.3. In the aspect of obstacle recognition, people mostly use constant carrier frequencysignal now, the amplitude estimation method for CF signal mainly includes quadraturesampling method, quarter sampling method and so on. These algorithms need to knowaccurate frequency of the signal, and when SNR is low, the accuracy is difficult to guarantee.This paper raised linear FM signal amplitude estimation method. In different SNR, thismethod has higher accuracy than the conventional methods. This article uses the amplitudeand delay-time as characteristic the value, and also use BP neural network to identify differentobstacles in the environment.4. The existing guidance methods and equipment have shortcomings such as taking along time, low accuracy and unclear prompting message. This paper raised a new kind ofguidance method and equipment. This method use both CF and linear FM signal to detect, use better algorithm to measure distance and recognize obstacles. And the equipment alsoprovides multiple ways to prompt the obstacles and can give the users better experience.