On the Use of Unscented Kalman Filter for Improving Ultrasonic Time-of-Flight Measurement

The paper deals with distance or level measurements based on ultrasonic time-of-fight estimation. Starting from a past experience concerning the use of the discrete extended Kalman filter (DEKF) to overcome some limitations affecting already available ultrasonic-based techniques, the authors are going to present a new digital signal-processing method capable of improving the cited advantages. The method is based on the unscented Kalman filter (UKF), a new extension of Kalman filter theory mandated to face some DEKF problems, mainly due to its inherent linearization approach. At this aim, UKF is applied to the acquired ultrasonic signals in order to improve the estimation of returned echo envelope as well as location of its onset. After describing key features and implementation issues of the new method, results obtained in a number of tests on simulated and actual ultrasonic signals are given, which assess its reliability and effectiveness along with advantages with respect to the previous one.