Dynamic model based length measurement using stationary waves

A highly accurate pipe length on-line measurement with acoustic sensor is considered. Stationary waves in straight pipes are modeled with a finite-dimensional linear dynamic system including unknown parameters. Posteriori probabilities of the candidates for the unknown parameters are calculated and pipe length measurement is obtained by taking expectation of the candidates. In order to realize a highly accurate on-line measurement, a criterion to select the optimal modes of the stationary wave is also presented. (C) 2000 Elsevier Science Ltd. All rights reserved.