Positioning Algorithm Of Ultrasonic Infrared Electronic Whiteboard Based On EMD-TFPF Combined With Teager Energy Operator

Ultrasound and infrared whiteboard can achieve positioning, enabling casual writing, labeling, storage and remote interactive functions by measuring the time of arrival of ultrasound (TOA). In addition to education, it is widely used in many areas such as conferences, exhibitions and training. In the using environment, there are a lot of interferences caused by sound, light, electromagnetic and etc., which damage the ultrasonic signals in some degrees and affect the whiteboard’s positioning accuracy.The most commonly used software and hardware threshold denoising method exists some errors, because it could not eliminate the interferences brought by itself, the detect errors and the unstable signals’non-ideal de-noising effects.According to the features that the ultrasonic signal waveforms are reliable, that is,one ultrasonic waveform only has one maximum peak, we put the maximum peak corresponded to the time, as the ultrasound delay. Therefore, we propose the algorithm accurately extract sub ultrasonic delay based on EMD-TFPF Teager binding energy operators, to achieve the precision of whiteboard’s positioning. This algorithm improves the ability and suitability of the algorithm against noise on the environment, based on the perspective of waveform characteristics.First, we need to carefully extract the useful ultrasound signals from the noisy ultrasound as much as possible. As the noisy ultrasound is non-stationary signals, in this paper, we de-noises it by frequency peak filtering algorithm (TFPF) which is optimized by empirical mode decomposition (EMD). It overcomes its own contradictions EMD modal aliasing algorithms defects and TFPF long window selected to some extent. Compared with the disadvantages of Non stationary signal in the presence of time frequency window fixed by frequently used time-frequency analysis methods, for example, window when a conventional (such as short-time Fourier transform and wavelet transform) the presence of non-stationary signals, the signals de-noised by ultrasound EMD-TFPF algorithm achieved a better balance on fidelity and noise pressing.Second, we need to determine the maximum peak of ultrasonic wave after de-noising. In this paper, we use Teager Energy Operator (TEO) to extract the instantaneous power waveform (ie waveform peaks), determined the maximum peak rising phase ultrasonic waveform, and then,we accurately extract the maximum peak corresponding to the moment ultrasonic signal delay. Compared with the use of an analog circuit extraction signal delay, this method is easy to implement, more stable, and non-restricted by the hardware-independent circuit conditions itself.Through simulation experiments, this paper shows that the algorithm is feasible and effective in ultrasound and infrared whiteboard positioning. It provides new ideas for ultrasound-based de-noising and other application areas, such as ultrasound automatic car navigation.