Realizing Large Shape Deformations of a Flying Continuum Robot With a Passive Rotating Nozzle Unit That Enlarges Jet Directions in Three-Dimensional Space

Flexible continuum robots have considerable potential for use in exploring intricate spaces, and their ability to make large body shape deformations can increase the inspection area. We previously proposed a jet-actuated flying continuum robot for extinguishing fires. The main challenge in implementing large shape deformations is accommodating the twisting of the body that results from the deformation. To address this problem, we proposed a two-dimensional passive rotating nozzle unit that can expand the directionality of net force against torsion; however, it has not yet been tested on a flying robot. In this study, we achieved the large shape deformations of a jet-actuated flying continuum robot using an improved passive rotating nozzle unit that can handle three-dimensional (3D) force. First, we developed a model of the improved nozzle unit and confirmed that the unit can increase the net force direction. Herein, the design strategy for the rotary damper to handle the instability that arises from motor limitations is discussed. The stabilized flight controller was applied to a continuum robot with the nozzle unit. Simulation results showed that the 2 m robot could perform large head bends (from 0° to 135°). Although the previous fixed nozzle unit twisted by approximately 40°, which made the extra movable range of the nozzles effectively zero, the proposed nozzle unit maintained the movable range to avoid twisting. We experimentally confirmed that the nozzle unit can expand the direction of the 3D net force, and that a large shape bending of approximately ±90° can be achieved using a 1.6 m flying robot.