Length Measurement for Pipes with Curves and Branches Using Stationary Wave

In the field of measurement, we often face the situations where pipe lengths have to be indirectly measured. As the indirect measurement media, light and sound waves are well known. But, in the cases where vapor appears and/or the pipes have curves and branches, light waves cannot be applied because of its scattering and rectilinear propagation properties. On the contrary, sound wave is not affected by the vapor, and also not strongly affected by curves and bend points in the propagation. One of the authors thus previously developed a pipe length measurement system for straight pipes using the sound wave. The system modeled the stationary wave, instantaneously generated in the pipe, as an output of a linear dynamic system and enabled an on-line high-accurate pipe length measurement using a maximum likelihood method. This paper extends the method to be able to measure the lengths of pipes with curves and branches. Experimental results will show that accurate pipe length measurement is realized with the method.