Stabilized Controller for Jet Actuated Cantilevered Pipe Using Damping Effect of an Internal Flowing Fluid

Fluid jet actuation is a potential actuation technique for continuum robots. It can generate and rapidly control a relatively large force using a small and lightweight structure because a significant amount of energy can be transported through its internal channels. Recently, jet-actuated flying continuum robots have been developed using this advantageous characteristic. However, a challenging issue in controlling the robot is the fluid structure interaction between the flexible body and the internal flowing fluid. This interaction often causes instability in the pipe conveying fluid. In this study, as a first step to address this issue, we propose a stabilized controller (vertical position control) for a jet-actuated two-dimensional cantilevered pipe with a nozzle unit at the tip using the damping effect of the internal flowing fluid and verify the controller with a real robot. Specifically, a model is constructed with the net force of the jets as the control input. A simple controller that can constantly decrease the energy function is proposed by utilizing the damping effect of the flowing fluid. Numerical simulations verify the stability of the system regardless of the flow velocity. In particular, fluid damping mainly suppresses the higher-order mode oscillations. Moreover, the stability of the system can be improved by adjusting the controller gains. We also conduct experiments using an actual robot to verify the simulation results. The vibrations can be damped by the fluid effect, and the stability can be improved using the proposed controller.