Abstract: A power self-support in-pipe robot is studied. The robot is entirely immersed in the pipe that is full of fluid. Depending on driving force generated by the pressure of fluid and energy of fluid speed, the robot moves forward with the fluid in the pipe. According to the different fluid medium, the robot must conquer inertia mass, overcome the friction force between pipe-walls, and keep proper working speed state. So the design of broad sense physical dimension and hydromechanics condi-tion that the pipe must provide with are studied.

Key words: Fluid pressure, In-pipe robot, Power self-support