In recent years, the aging of pipelines has been severe and has caused fatal accidents. The pipe diameters are small, and the layouts are complex. Pneumatically driven mobile robots have become popular as inspection methods. Various types of robots have been studied, like earthworm-type robots, inchworm-type robots, and spiral-tube-type robots. Typically, they make periodic movements; however, they have challenges because they are driven by existing pneumatic valve technologies, which are limited to small mobile robots. Small pneumatic valves have low flow rates and limit the performance of pneumatic actuators. Therefore, we focused on the structure of the ball valve and periodic motion. Furthermore, in this paper, we developed the Compact Rotary Valve Mechanism for pneumatic mobile robots in pipe inspection, which generates periodic air pressure.
