Conference Paper

Octopus-inspired Eight-arm Robotic Swimming by Sculling Movements

DOI: 10.1109/ICRA.2013.6631314 Conference: IEEE Int. Conf. Rob. Autom. (ICRA'13), Volume: pp. 5135-5141


Inspired by the octopus arm morphology and exploiting recordings of swimming octopus, we investigate the propulsive capabilities of an 8-arm robotic system under various swimming gaits, including arm sculling and arm undulations, for the generation of forward propulsion. A dynamical model of the robotic system, that considers fluid drag contributions accurately evaluated by CFD methods, was used to study the effects of various kinematic parameters on propulsion. Exper- iments inside a water tank with an 8-arm robotic prototype successfully demonstrated the sculling-only gaits, attaining a maximum speed of approximately 0.2 body lengths per second. Similar trends were observed, as in the simulation studies, with respect to the effect of the kinematic parameters on propulsion.

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    • "The temporal variation of the angular velocity xðtÞ and the angle of rotation /ðtÞ may take various forms for a two-stroke motion profile, in which the arm rotates upwards and downwards in a cyclic way. Here, we examine two basic profiles, as displayed in Fig. 2a and b: a sinusoidal oscillation, and a sculling profile [4] [5] [37] [38] of different velocity ratio b between a relatively slow upstroke (termed as recovery stroke [37]) and a considerably faster downstroke (termed power stroke [37]). These motion profiles originate from observations of live octopus and analysis of the reconstructed 3D arm trajectories, during arm-swimming motion, in the way described in the previous paragraph and presented in Fig. 1. "
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    ABSTRACT: The complexity in structure and locomotion of cephalopods, such as the octopus, poses difficulties in modeling and simulation. Their slender arms, being highly agile and dexterous, often involve intense deformations, which are hard to simulate accurately, while simultaneously ensuring numerical stability and low diffusion of the transient motion results. Within the immersed-boundary framework, this paper focuses on an arm geometry performing prescribed motions that reflect octopus locomotion. The method is compared with a finite-volume numerical approach to determine the mesh requirements that must be employed for sufficiently capturing, not only the near wall viscous flow, but also the off-body vortical flow field in intense forced motions. The objective is to demonstrate and exploit the generality of the immersed boundary approach to complex numerical simulations of deforming geometries. Incorporation of arm deformation was found to increase the output thrust of a single-arm system. It was further found that sculling motion combined with arm undulations provides an effective propulsive scheme for an octopus-like arm.
    Computers & Fluids 07/2015; 115. DOI:10.1016/j.compfluid.2015.03.009 · 1.62 Impact Factor
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    • "Although this captures the basic motion components, a more quantified kinematic description would reveal new aspects of this unique propulsion mode if implemented in robotic models. We have recently presented a multi-arm underwater robot [11]–[14] that mimics the morphology of the octopus, possessing 8 compliant arms and a passively-compliant web. The robotic model has included detailed information of hydrodynamic results [15]–[18] and is in accordance with relevant elastodynamic investigations of arm muscle activation [19], [20]. "
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    ABSTRACT: The octopus uses the arm-swimming behavior primarily for escape, defense, or foraging. This mode of locomotion is comprised of two strokes, with the arms opening slowly and closing rapidly, and generally results in considerable propulsive acceleration. In light of the recent development by our group of an octopus-like eight-arm underwater robot, we are interested to analyze the details of the biological arm swimming motion, in order to understand its kinematics. In this paper, we address methodological aspects of the 3D reconstruction process of octopus arm trajectories, based on computer vision, and present the resulting arm swimming movement of a benthic common octopus. The 3D trajectories of all eight octopus arms were tracked and analyzed, providing information about speed, acceleration and arm elongation. The animal's performance is then used for a direct comparison with our 8-arm robotic swimmer. The data obtained provide new kinematic information about this, relatively unknown, propulsive mode, which can be exploited for multi-functional underwater robots.
    Proceedings - IEEE International Conference on Robotics and Automation 06/2015; 2015:1178-1183. DOI:10.1109/ICRA.2015.7139340
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    • "In particular, for the closed-loop control task, our results suggest that soft body dynamics can be sufficient to perform the task to control the body without the need of an external controller for additional memory capacity. This can be, for example, directly applied to the recently proposed octopus-inspired swimming robot [27] to generate the arm motion in a closed-loop manner exploiting the body dynamics itself, which largely outsources the computational load required to generate the motor command to the body. The technique presented here can be potentially applied to a wide class of soft robots because the main component required is the soft body itself. "
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    ABSTRACT: Soft materials are not only highly deformable but they also possess rich and diverse body dynamics. Soft body dynamics exhibit a variety of properties, including nonlinearity, elasticity, and potentially infinitely many degrees of freedom. Here we demonstrate that such soft body dynamics can be employed to conduct certain types of computation. Using body dynamics generated from a soft silicone arm, we show that they can be exploited to emulate functions that require memory and to embed robust closed-loop control into the arm. Our results suggest that soft body dynamics have a short-term memory and can serve as a computational resource. This finding paves the way toward exploiting passive body dynamics for control of a large class of underactuated systems.
    Journal of The Royal Society Interface 06/2014; 11(100). DOI:10.1098/rsif.2014.0437 · 3.92 Impact Factor
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