I. Introduction
Fluid injection has promising potential as a novel actuation approach to enable the rapid switching of large forces for controlling the motion of a robot. The principle involves injecting fluid vigorously and harnessing the resulting reaction force as the driving force. Several long flexible tube-shaped robots have adopted this approach for flying and for rapid direction control at the tip or middle of the body using water jets [1]–[7] and air jets [8], [9]. A previous study has also reported an air jet perturbation device attached to the wrist, used for determining the mechanical properties of the human arm [10].