A novel inner spiral in-pipe robot was proposed. The structure of the robot was designed, and the dynamics equations of the robot were established. When the robot run in the pipe filled with liquid, the pressure to the pipe wall, the robotic axial thrust force and the robotic circumferential resisting moment were analyzed numerically. The results show that the robot is driven by the external magnetic field, the robotic axial thrust force and the robotic circumferential resisting moment all increase and the damage to the pipe wall is also aggravated. In order to optimize the robotic axial thrust force and the robot energy efficiency index, the orthogonal experimental optimization method was used, and the optimal inner spiral geometric parametrical combination was obtained. According to the working principles of the inner spiral robot, an inner spiral driving device was designed and fabricated, and the running experiments in the pipe full of 201 methyl silicone oil proved the feasibility of the proposed robot. The proposed inner spiral robot has smooth surfaces and can be suspended to run. As the damage to the pipe is small, the robot can be used in tiny human pipes.
