Stability analysis of tensegrity mechanism coupled with a bio-inspired piping inspection robot

Abstract: Piping inspection robots play an essential role for industries as they can reduce human effort and pose a lesser risk to their lives. Generally, the locomotion techniques of these robots can be classified into mechanical and bioinspired. By using slot-follower leg mechanisms, DC-motors, and control units, a rigid caterpillar type inspection robot was designed and developed at LS2N, France . This rigid prototype helped in identifying the static forces required to accomplish good contact forces with the pipeline walls. In order to work inside curvatures, a tensegrity mechanism that uses three tension springs and a passive universal joint was introduced between each module of this robot. The optimal parameters of the robot assembly were identified by considering a preload of the cables, which ensured the stability of the entire robot. However, under static conditions, there exist some forces on the robot, especially on the tensegrity mechanism when one end of the leg mechanism is clamped with the pipeline walls. These forces are dominant when the orientation of the pipeline is horizontal. The objective of this article is to understand the effect of the stiffness of the spring on the static stability of the tensegrity mechanism under the self-weight of the robot assembly.