A highly accurate ultrasonic ranging method based on onset extraction and phase shift detection

The opposite-type ultrasonic ranging application is widely used in spatial 3D coordinates measurement systems. The traditional phase shift (PS) estimation based on multi-frequency ultrasonic pulse is a highly accurate ranging method but has high requirement to the transducers and signal processing algorithm. This paper proposes a novel opposite-type ultrasonic ranging method with single frequency pulse. It can estimate the time of flight (TOF) roughly through extracting the signal's onset based on self-correlation and correct the TOF accurately through detecting the phase shift between the transmission and reception signals. In order to reduce the noise disturbance to this algorithm, a new de-noising method based on wavelet decomposition is presented, and the de-noising effect is analyzed by MATLAB simulation. Finally, three separate ultrasonic ranging experiments were designed to validate the effects of wavelet de-noising, PS detection and temperature field compensation. The accuracy of distance measurement can achieve 0.5 mm for the distance up to 5000 mm.