Wireless In-Piping Actuator Capable of High-Speed Locomotion by a New Motion Principle

Finding damage inside pipes is important for the inspection of pipes used in nuclear power plants and chemical plants. A number of studies have investigated the mechanisms of an actuator with an electric cable to provide locomotion through various devices in pipes. A wireless actuator capable of movement in narrow pipes of several millimeters in diameter has not yet been developed. This paper proposes a novel wireless magnetic actuator with a new propulsion module that exhibits a very high thrusting force and is capable of locomotion in a thin pipe by a new motion principle. Including this principle, we completely established the motion principles of three types due to the change of a supporting force of the wireless magnetic actuator by a theory and an experiment. The application of a rubber leg having optimal flexural rigidity demonstrates that a reciprocating motion caused by vibration can be efficiently converted into movement in one direction. This actuator contains an electrical inverter that directly transforms dc from button batteries into ac. The actuator is moved by the synergy of the vibration amplitude and elastic energy of the mass-spring system due to mechanical resonance energy. Experimental results indicate that the proposed actuator is able to move upward at a speed of 68.5 mm/s by the power provided by ten button batteries when pulling a 10-g load mass. This wireless magnetic actuator has several possible applications, including small pipe inspection and maintenance.