Proposal of a Method for Measuring Inside Diameter of Tubes Using a Drive Unit of a Robot for Inspection of Small Tubes

Sewerage systems are indispensable infrastructures; thus, it is important to monitor their condition through periodic inspections. The wall thickness of pipes is particularly important during inspection. However, measuring the wall thickness of pipes in long, narrow, and complicated shapes using existing technologies is difficult. Therefore, this study aims to establish a method for measuring and estimating the inside diameter of pipes that can be used for long-distance, complex buried pipes. In a previous study, a pneumatically driven robot was developed for long-distance pipe inspection. We proposed a method to estimate the pipe inner diameter from the information obtained from the driving unit of this robot. In this method, a geometry model of the pneumatic drive unit was developed, and the model was used to estimate the pipe’s inner diameter from the supply pressure and flow rate to the unit. Experimental results show that the developed model can estimate the inside diameter within an error range of less than 5%. This method can be used to estimate the inside diameters of long, narrow, and complicated pipes, and it can help prevent accidents, such as liquefaction and gas leakage caused by pipe failure.