A snake-like hyper-redundant robot for giant thin-walled cylindrical section friction stir welding support

In friction stir welding of giant thin-walled cylindrical sections, the large welding force causes unacceptable deformation which raises demand for the proper fixture. However, most fixture nowadays needs manual work and without enough stiffness to countervail the welding force. Thus, we proposed a snake-like hyper-redundant robot with effective deployment, self-lock, and high supporting stiffness. We give the design of a snake with 3PUU joints and cable assistance system, established the kinetics model and static model with vector method and screw theory to control the robot with minimized joint force. Finally, we made a scaled prototype to verify motion control with 20 mm/s maximum and a full-sized prototype to verify the stiffness performance larger than 25 KN/mm on the radial.