Four-fin Bio-inspired Uuv: Modeling and Control Solutions

This paper describes the modeling and control development of a bio-inspired unmanned underwater vehicle (UUV) propelled by four pectoral fins. Based on both computational fluid dynamics (CFD) and experimental fin data, we develop a UUV model that focuses on an accurate representation of the fin-generated forces. Models of these forces span a range of controllable fin parameters, as well as take into account leadingtrailing fin interactions and free stream flow speeds. The vehicle model is validated by comparing open-loop simulated responses with experimentally measured responses to identical fin inputs. Closed-loop control algorithms, which command changes in fin kinematics, are tested on the vehicle. Comparison of experimental and simulation results for various maneuvers validates the fin and vehicle models, and demonstrates the precise maneuvering capabilities enabled by the actively controlled curvature pectoral fins. INTRODUCTION Current unmanned underwater vehicles excel at many critical tasks including deeply submerged and high-endurance operations, performing high-speed and large-radius maneuvers. However, the traditional propeller-driven vehicles performing these missions have not demonstrated the same levels of operational success in cluttered, near-shore environments where precise positioning and small-radius maneuvers are required in the presence of waves and alternating currents. Researchers have therefore studied the fin force production mechanisms employed by various fish species in their attempts to understand how these organisms achieve high levels of controllability in difficult environments [1]. Within fish swimming, articulation of the pectoral fins has been shown to produce forces and moments ideal for high-maneuverability in low-speed and hovering operations [2]. Several investigators have developed and adapted passively deforming robotic pectoral fins onto UUVs [3][4][5][6], whereas others have pursued the development of active control deformation pectoral fins [7][8][9]. In our previous work, we concluded that active control over the curvature of the robotic pectoral fins was necessary to achieve precise low-speed maneuverability of UUVs in highly time-varying external force environments, and others have come to similar conclusions about the use of fish-like fins [10][11]. Design, construction, and testing of such a fin on a two-fin vehicle have demonstrated the success of this strategy in achieving the force production and vehicle maneuvering capabilities necessary for operation in these challenging environments [8][12][13][14]. This paper details the subsequent development of a four-fin vehicle (Figure 1) which has more payload, greater top speed, and tighter turning capability than our two-fin active curvaturecontrol technology demonstration vehicle. The modeling of this four-fin vehicle is described with particular emphasis on the fin models. Using our previous studies of fin force production Proceedings of the ASME 2011 International Mechanical Engineering Congress & Exposition IMECE2011 November 11-17, 2011, Denver, Colorado, USA