A novel underactuated tetrahedral mobile robot

This paper presents a novel underactuated tetrahedral mobile robot with 12 degrees-of-freedom (DOFs). The robot contains four vertices and six URU chains (where U represents a universal joint and R represents an actuated revolute joint). The tetrahedral structure makes the robot have continuous mobile ability at any posture. The mobility analysis has been made and demonstrates the feasibility of underactuated which demands fewer devices and low costs. A kind of rolling locomotion of the robot is proposed, and the feasibility of the locomotion is proved by the kinematic and locomotion analysis based on an equivalent planar mechanism. Finally, a prototype is manufactured and a series of experiments are performed to verify the mobile capability of the robot.