Abstract: A novel design of creeping micro in-pipe robot is presented, aiming at micro pipelines with diameters of 15~20 mm. The instability of robot motion is found through virtual prototype simulation. To further provide guidance for the design and optimization of the system structure, the dynamic model of robot motion under constraint condition of frictional contact is established. The reduced-order model is obtained with linear complementarity theory. Existence and uniqueness of solutions to the model are discussed. Kelvin model and singular perturbation are used to reveal the additional conditions for ensuring contact force stability in the reduced-order model. The stability of the robot moving in straight pipe is simulated. And improved design of the robot structure is proposed according to the simulation result. Correctness of the theoretical analysis and advantages of the improved design are proved by virtual simulation and experiments.

Key words: Linear complementarity problem, Micro in-pipe robot, Singular perturbation, Stability, Virtual prototype