Globular actuator group for reversible movement in a complex pipe

Finding damage inside pipes is important for the inspection of complex pipes used in nuclear power plants and chemical plants. An in-pipe robot capable of movement in narrow complex pipes has not yet been developed. Two actuators of the same size and characteristics are coupled by the magnetic connection method, which generates almost no mechanical loss. The globular magnetic actuator group capable of reversible motion through elongation and contraction of eight shape-memory-alloy (SMA) coils was fabricated. Experimental results indicate that the prototype actuator group is able to climb at a rate of 73 mm/s in a straight pipe with no load mass. In addition, the average speeds for two patterns of movement in a complex pipe with several curved sections and step sections were measured. The prototype actuator group is able to move in a complex pipe at an average speed of over 30 mm/s.