Dynamic control of biologically inspired pulsatile jet propulsion thrusters

Inspired by the propulsion techniques employed by squid and other cephalopod, a new type of thruster was designed which utilized pulsatile jet propulsion to generate controlling forces. The thrust production from this jet actuator was characterized in a static environment and seen to be well approximated by a simple fluid slug model. A linear transfer function model was derived to describe the transient dynamics of this thruster being employed in a virtual vehicle simulation; which was developed to test the thruster with unsteady driving signals. It was predicted that an impulsive type of thrust (as is found in our jet actuator) is ideal in a non-linear damping environment, since all of the acceleration is being added to the system while it´s at its lowest velocity and therefore lowest drag. Due to the extremely non-linear nature of underwater vehicle environments we developed a scaling system to classify regimes of maneuvers and characterize their dynamics independently. Assuming a simple proportional derivative control algorithm, the vehicle closed loop frequency response was predicted using the transfer function model; which was linearized according to the maneuvering regime. Within the hybrid simulation environment, the closed loop frequency response was tested empirically and seen to be well approximated by the model.