Air-Jet Levitation of Continuum Robots: Stable Head Floating by Passive Thrust Vectoring for Enhancing Mobility

Abstract Flexible, continuum-type robots can access narrow spaces in debris areas during search-and-rescue missions. However, their current problem is the lifting capability of the head, which is necessary to surmount the rubble. This study proposes a passive-thrust vectoring method to stabilize head levitation for air-jet-actuated, long, continuum robots, and thus enhance their step-climbing abilities. An air jet can generate a thrust force that is sufficient for head levitation. A critical issue in levitation involves the backward bending of the head without using any air-jet control; however, thrust control is inappropriate because of the delay caused by the long channel. Therefore, the proposed method maintains the thrust direction constant. Sufficient conditions for global stability are derived and confirmed via dynamic simulations. The proposed method is simple and can be mechanically realized with a passive head-bending mechanism, thus contributing to a lightweight design. Experiments demonstrated that the developed air-floating-type, 7-m long robot, can achieve stabilized head levitation, and that the robot can climb a step with a height of 250 mm. Robot demonstrations in rubble justify the robot’s capacity to surmount the rubble. This passive-thrust vectoring method is expected to contribute to the future enhancement of the mobility of continuum robots owing to its simplicity and practicality.