Translational Disturbance Rejection for Jet-Actuated Flying Continuum Robots on Mobile Bases

Although continuum robots have the potential to operate in narrow areas by changing their shapes and propelling their bodies, they easily vibrate under sudden or periodic applications of external forces. Suppressing vibrations is difficult in our jet-actuated continuum robot because the movements of its mobile base cannot be controlled with the same system as the movements of the robot, and mobile base oscillation increases the risk of resonance. In this study, a disturbance rejection was realized for the Dragon Firefighter, a jet-actuated flying continuum robot on a mobile base, for rapid and safe fire extinguishing using a 4-m-long flying fire hose consisting of two nozzle units and flexible hoses. An $\mathcal {H}_\infty$ -based disturbance-rejection controller was designed to suppress the vibration of the head nozzle unit posture against the acceleration of the mobile base. Then, the robot parameters were identified from tensile tests and dynamic excitation experiments. Dynamic simulations confirmed that the controller reduced the peak gain of the frequency response by approximately 2 dB for various robot shapes. Robot experiments confirmed that the proposed method reduced the peak gain of the frequency response by approximately 3 dB, which increased the extra injection range of the nozzle by approximately 16%.