Abstract
In the field of measurement and control, there are many applications where the measurement of a length of a pipe plays an important role. The present paper develops an automatic on-line measurement system which measures the length of a pipe on-line, to aim to measure the location of the time-variant sand surface in a steel pipe. This application is frequently found in the construction which improves weak foundation, irrespective sea and land. In the construction, the sand surface is fallen down in a steel pipe by repeating press and pressure reduction, which yields much water vapour in the pipe and makes the application of range sensors to the detection of the sand surface impossible.
From the viewpoint, the paper proposes to use an acoustic sensor to extract the information on the length between the sand surface and the upper end of the pipe. Furthermore, by making use of the fact that in a pipe, opened or closed at the ends, stationary waves become dominant in the fluctuation of the acoustic pressure as time passes, the paper models the fluctuation of the acoustic pressure adequately by a linear dynamic system and uses a bank of Kalman filters to estimate the length of the pipe on-line.
