  This paper introduces the Omnidirectional Tractable Three Module Robot for
traversing inside complex pipe networks. The robot consists of three
omnidirectional modules fixed 120{\deg} apart circumferentially which can
rotate about their own axis allowing holonomic motion of the robot. The
holonomic motion enables the robot to overcome motion singularity when
negotiating T-junctions and further allows the robot to arrive in a preferred
orientation while taking turns inside a pipe. We have developed a closed-form
kinematic model for the robot in the paper and propose the Motion Singularity
Region that the robot needs to avoid while negotiating T-junction. The design
and motion capabilities of the robot are demonstrated both by conducting
simulations in MSC ADAMS on a simplified lumped-model of the robot and with
experiments on its physical embodiment.
