Improvement of the self-propelled rotary actuator in consideration of shape and rolling direction of steel sheets

It is very important for prevention of accidents to detect cracks and defects inside of steam generator tubes in the industrial plants as typified by nuclear power plants. In order to detect the defects inside of tube with complicated structure, it is necessary to developed an electromagnetic actuator self-propelled inside of tube. The easiest method of applying and exciting magnetic field to the electromagnetic actuator from the outside of tube is how to wind copper wire around tube and form a solenoid coil on the surface of tube. However, in this case, an exciting magnetic field is induced in parallel to the axis direction of tube by the coil.