  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.
