0 m/s,the relationship between current resistance and thrust push of the push tug at the transitional reach outside entrance of navigation lock is analyzed,and the requirement that the ratio of displacement tonnage to power should be less than 9.

According to the actual engineering needs,a lead screw and nut pair regulating mechanism is chosen and a novel in-pipe robot is designed,which can adapt to micro pipes with diameters in the range of 15 mm～20mm.