Highly accurate pipe length measurement for straight pipes with open ends using stationary waves

摘要

The authors previously developed a pipe length measurement system for straight pipes with closed ends using an acoustic sensor. The system realized a highly accurate on-line length measurement by making use of the stationary wave in the pipes as state variables of a linear dynamic system and also by using Kalman filters and maximum likelihood method. There are however practically lots of applications where length measurement is required for the pipes with open cuds. In order to measure the length of such a pipe, a compensation for the open ends must be taken into account. The problem is however that the compensation strongly depends on the environment around the open ends and what is worse the compensation coefficient is not a priori known. The paper thus proposes a new measurement system which exactly measures the length of pipes with one or two open ends despite of the measurement environment around the open ends. Experiments will show that a highly accurate pipe length measurement is realized together with the open end compensations.