Development of an Unmanned Hybrid Vehicle Using Artificial Pectoral Fins

Abstract

An unmanned vehicle has been developed for dual use as both an aircraft and a submersible. To achieve long-range emplacement of a highly maneuverable underwater asset to a target environment, the Flimmer (Flying-Swimmer) vehicle is designed for both high-speed flight and low-speed swimming. Building on previous research in bioinspired propulsion and control systems, the vehicle employs a unique set of artificial flapping fins for underwater maneuvering, which must be considered when evaluating the flight and water landing capabilities. This paper describes the computational analysis and experimental results for all three phases of vehicle operation—flight, landing, and swimming. Computational fluid dynamics simulation results predict aero- and hydrodynamic characteristics and demonstrate landing loads on and trajectory of the vehicle. Experimental data demonstrate flight and swimming performance and validate the computational results, and experimental testing of water landing provides a comparison with computations. Results and analyses of the Flimmer vehicle performance demonstrate the operational capabilities of an unmanned hybrid vehicle for long-range flight and low-speed swimming.

Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

“…They show that δ = -90 o and +90 o correspond to the maximum and minimum rear fin thrust respectively, while thrust is identical to that of the front fin (not shown) at 0 o . These results are in agreement with our prior findings for different fin kinematics [9,28,29].…”

“…The configuration of tandem, identical geometry fins flapping perpendicular to the direction of flow is similar to lift-based pectoral fin motions of some fish species [20]. This configuration is also found on a number of vehicles designs due to the control authority it affords in low-speed maneuvers [2,[9][10][11].…”

“…Based on our prior experience [9,28,29] and literature [15,31] we have opted for a bio-inspired trapezoidal fin with an aspect ratio of 3:1 (Figure 1b). This geometry produced greater thrust in a tandem two-fin configuration than an identical size and aspect ratio rectangular fin [29].…”

“…For a given axial distance between flapping fins, stroke amplitude and frequency, there appears to be an advantage in terms of the thrust output of the rear fin when δ is varied [9,28,29]. Hence, we look at thrust and power measurements at several δ values to probe the same.…”

“…Low-speed maneuvering and station keeping capabilities for small unmanned underwater vehicles (UUVs) is of great interest to the maritime community for operations in confined, dynamic-flow, shallow-water environments. To address these needs, several researchers have taken inspiration from the pectoral fins employed by various fish species to develop flapping mechanisms [1][2][3][4][5][6][7][8][9][10][11]. In many of these fins, large amplitude rotational stroke motions are used to achieve thrust.…”