A adjustive mechanism of pipe-line robot for variable diameters is designed

which comprises screw driven units.Firstly

the mechanical adjustment characteristic for the mechanism to adapt to the varying pipe size is analyzed.Meanwhile

the movement of the wheel

which is installed on the adjustive mechanism

is also analyzed for the case that the robot is walking in a circular pipe.Then with the help of Matlab software

kinematical simulation is presented

which shows the relationship between screw Torque

the linkage angle

the driving force and the screw-lead.Simulations also demonstrate that the robot is applicable to pipes with diameter ranging from 445mm to 558mm.The driving force is stability.