Deformable tensegrity structure underwater robot with a transformation mechanism

Underwater robots for inspecting marine structures such as breakwaters, pipes and quay walls require mobility not only for self-transport but for rotation during inspection. To facilitate rotation mobility, we have proposed a portable, lightweight underwater robot whose performance to translate and rotate is achieved by it altering its shape. The shape is that of a three-strut tensegrity structure of three pipes connected with rubber strings. This manuscript describes a transformation mechanism for an underwater robot with a deformable tensegrity structure. The transformation mechanism includes a winding unit with a planetary gear. We show that the transformation mechanism has a self-locking feature by selecting a high gear ratio of the winding unit. We also evaluate the fluid characteristics of the robot with the transformation mechanism in several experiments in a circulating water tank to investigate the effect of the transformation mechanism.