Fast Dynamics of an Eel-Like Robot—Comparisons With Navier–Stokes Simulations

Inst. de Rech. en Commun. et Cybernetique de Nantes, Ecole des Mines de Nantes, Nantes
IEEE Transactions on Robotics (Impact Factor: 2.43). 01/2009; 24(6):1274 - 1288. DOI: 10.1109/TRO.2008.2006249
Source: IEEE Xplore


This paper proposes a dynamic model of the swim of elongated fish suited to the online control of biomimetic eel-like robots. The approach can be considered as an extension of the original reactive ldquolarge elongated body theoryrdquo of Lighthill to the 3-D self-propulsion to which a resistive empirical model has been added. While all the mathematical fundamentals have been detailed by Boyer . (, 2007), this paper essentially focuses on the numerical validation and calibration of the model and the study of swimming gaits. The proposed model is coupled to an algorithm allowing us to compute the motion of the fish head and the field of internal control torque from the knowledge of the imposed internal strain fields. Based on the Newton-Euler formalism of robot dynamics, this algorithm works faster than real time. As far as precision is concerned, many tests obtained with several planar and 3-D gaits are reported and compared (in the planar case) with a Navier-Stokes solver, which, until today have been devoted to the planar swim. The comparisons obtained are very encouraging since in all the cases we tested, the differences between our simplified and reference simulations do not exceed 10%.

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    • "The dynamics of continuous robotic manipulators has been addressed in several studies, see, for example, Refs. [5] [6] [7] [8] [9]. The dynamics of a slewing flexible link is presented in Refs. "
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    ABSTRACT: We present the continuous model of a mobile slender mechanism that is intended to be the structure of an autonomous hyper-redundant slender robotic system. Rigid body degrees-of-freedom (DOF) and deformability are coupled through a Lagrangian weak formulation that includes control inputs to achieve forward locomotion and shape tracking. The forward locomotion and the shape tracking are associated to the coupling with a substrate that models a generic environment with which the mechanism could interact. The assumption of small deformations around rigid body placements allows to adopt the floating reference kinematic description. By posing the distributed parameter control problem in weak form, we naturally introduce an approximate solution technique based on Galerkin projection on the linear mode shapes of the Timoshenko beam model that is adopted to describe the body of the system. Simulation results illustrate coupling among forward motion and shape tracking as described by the equations governing the system.
    Journal of Dynamic Systems Measurement and Control 10/2015; 137(10). DOI:10.1115/1.4030816 · 0.98 Impact Factor
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    • "As a result, the drag forces are modeled with an empirical model due to Morison et al. [36]. The complete model was validated through extensive Navier–Stokes simulation in the case of the self-propelled swimming of an elongated fish in [37]. "
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    ABSTRACT: The new and promising field of soft robotics has many open areas of research such as the development of an exhaustive theoretical and methodological approach to dynamic modeling. To help contribute to this area of research, this paper develops a dynamic model of a continuum soft robot arm driven by cables and based upon a rigorous geometrically exact approach. The model fully investigates both dynamic interaction with a dense medium and the coupled tendon condition. The model was experimentally validated with satisfactory results, using a soft robot arm working prototype inspired by the octopus arm and capable of multibending. Experimental validation was performed for the octopus most characteristic movements: bending, reaching, and fetching. The present model can be used in the design phase as a dynamic simulation platform and to design the control strategy of a continuum robot arm moving in a dense medium.
    IEEE Transactions on Robotics 10/2014; PP:1-14. DOI:10.1109/TRO.2014.2325992 · 2.43 Impact Factor
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    • "Furthermore, modelling the fish body as a nonlinear Cosserat beam, we extended Lighthill's model in [Boyer et al., 2008] (numerically) and [Boyer et al., 2010] (theoretically) to: 1) the 3-D swimming; 2) the self-propelled swimming (i.e. the net motions are calculated rather than being imposed); 3) the computation of the internal stress field of the Cosserat beam (which models the forces of the fish muscles or robot motors); 4) the modelling of resistive forces through a Taylor-like resistive model [Taylor, 1952]. This analytical model has been validated by comparisons with N-S simulations [Boyer et al., 2008]. In the case of planar swimming gaits and manoeuvres, the trajectory and speed discrepancies between the analytical model and the N-S simulations do not exceed 10%, drastically reducing the requirements for the CPU time. "
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    ABSTRACT: The best known analytical model of swimming was originally developed by Lighthill and is known as the large amplitude elongated body theory (LAEBT). Recently, this theory has been improved and adapted to robotics through a series of studies ranging from hydrodynamic modeling to mobile multibody system dynamics. This article marks a further step towards the Lighthill theory. The LAEBT is applied to one of the best bio-inspired swimming robots yet built: the AmphiBot III, a modular anguilliform swimming robot. To that end, we apply a Newton–Euler modeling approach and focus our attention on the model of hydrodynamic forces. This model is numerically integrated in real time by using an extension of the Newton–Euler recursive forward dynamics algorithm for manipulators to a robot without a fixed base. Simulations and experiments are compared on undulatory gaits and turning maneuvers for a wide range of parameters. The discrepancies between modeling and reality do not exceed 16% for the swimming speed, while requiring only the one-time calibration of a few hydrodynamic parameters. Since the model can be numerically integrated in real time, it has significantly superior accuracy compared with computational speed ratio, and is, to the best of our knowledge, one of the most accurate models that can be used in real-time. It should provide an interesting tool for the design and control of swimming robots. The approach is presented in a self contained manner, with the concern to help the reader not familiar with fluid dynamics to get insight both into the physics of swimming and the mathematical tools that can help its modeling.
    The International Journal of Robotics Research 09/2014; 33(10):1322-1341. DOI:10.1177/0278364914525811 · 2.54 Impact Factor
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