Design and Experimental Validation of a Novel High-Speed Omnidirectional Underwater Propulsion Mechanism

This article details the design, working principles, and testing of a novel position control mechanism for marine operations or inspection in extreme, hostile, or high-speed turbulent environments where unprecedented speed and agility are necessary. The omnidirectional mechanism consists of a set of counter-rotating blades operating at frequencies high enough to dampen vibrational effects on onboard sensors. Each rotor is individually powered to allow for roll control via relative motor effort and attached to a servo-swashplate mechanism, enabling quick and powerful manipulation of fluid flow direction in the hull's coordinate frame without the need to track rotor position. The mechanism inherently severs blade loads from servo torques, putting all load on the main motors and minimizing servo response time, while exploiting consistent blade momentum to minimize the corresponding force response time. A small-scale force-validating model is fabricated and tested for various force and moment commands. Kinematic and hydrodynamic analyses of the hull and surrounding fluid forces during various blade maneuvers are presented, followed by the mechanical design and kinematic analysis of each subsystem in a small scale model. Experimental results of the small-scale model are presented that verify the concepts presented for the larger-scale model. Finally, an open-loop controller is constructed with decoupled parameters for each degree of freedom.