Using short-time Fourier transform and wavelet packet filter banks for improved frequency measurement in a Doppler robot tracking system

Previous research has shown that an ultrasonic tracking system using the Doppler effect can potentially track high-speed robot motion very accurately. However, ultrasound energy that is reflected by obstacles in the robot workspace can cause significant distortions in the frequency measurement. To reduce the distortions, a novel method for frequency measurement is described in this paper. This uses the short-time Fourier transform (STFT) to estimate the frequency of the interference signal. Then, the estimated frequencies are analyzed with an adaptive filter constructed with wavelet packet filter banks. Results are given that demonstrate great improvements in frequency measurement.