Metal Thickness Measurement Module with Scotch Yoke Mechanism for Tank Inspections

To avoid oil leakage accidents in large storage tanks, measurements of metal thicknesses are important to assess the structure conditions. Ultrasonic sensors are widely used to measure metal thicknesses. To realize ultrasonic thickness measurement by robots, it is necessary to realize contact between a probe and surfaces. In this study, we proposed a novel mechanism of a metal thickness measurement module which includes a Scotch Yoke mechanism to convert a robot’s movement to a pressing motion of a probe. The proposed module consists of a probe, a slider box, a slider, wheels, and a rotation disk with a pin. When the disk connected to the wheels rotates, the pin moves the slider connected to the probe up and down simultaneously. The module mounted on a magnet-type wall-climbing robot measured the metal thicknesses of the test pieces. We confirmed that the prototype module can realize the contacting and releasing of the probe to surfaces according to the wheel’s rotation.