Design and analysis of carbon fiber reinforced plastic body frame for multi-legged subsea walking robot, Crabster

This paper describes a new approach for a design and finite element analysis (FEA) of a body frame for a multi-legged subsea walking robot, Crabster200, of which the abbreviated name is CR200 and the operating depth is 200 m. Main body of the structural frame of CR200 is designed as a curved-rib-cage structure in order to disperse applied external loads effectively and to make a streamlined shape for minimizing hydrodynamic forces acted on CR200. The curved structural frame is made of carbon fiber reinforced plastic (CFRP) considering machinability, corrosiveness and stiffness per weight. Therefore, the frame is lighter and stronger than a frame of the other metallic materials used under the sea water in convention. In order to perform a reasonable FEA for the CFRP body frame, we have applied the material properties of CFRP obtained from a specimen test to the FE model. Then we have performed modal analyses and FEA with respect to certain load conditions for walking on the sea floor and the floor in air as well, and for a launch-and-recovery process of CR200 at sea. We also have performed FEA on the frame made of a conventional material and compared its characteristics to that of CFRP.