46 research outputs found
Macro-continuous computed torque algorithm for a three-dimensional eel-like robot
International audienceThis paper presents the dynamic modeling of a continuous three-dimensional swimming eel-like robot. The modeling approach is based on the "geometrically exact beam theory" and on that of Newton-Euler, as it is well known within the robotics community. The proposed algorithm allows us to compute the robot's Galilean movement and the control torques as a function of the expected internal deformation of the eel's body
Improved Lighthill fish swimming model for bio-inspired robots - Modelling, computational aspects and experimental comparisons.
International audienceThe best known analytical model of swimming was originally developed by Lighthill and is known as large amplitude elongated body theory (LAEBT). Recently, this theory has been improved and adapted to robotics through a series of studies [Boyer et al., 2008, 2010; Candelier et al., 2011] ranging from hydrodynamic modelling to mobile multibody system dynamics. This article marks a further step towards the Lighthill theory. The LAEBT is ap- plied 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 modelling approach and focus our attention on the model of hydrodynamic forces. This model is numerically in- tegrated 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 manoeuvres for a wide range of parameters. The discrepancies between modelling 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 com- pared 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 modelling
Action-Perception Trade-Offs for Anguilliform Swimming Robotic Platforms with an Electric Sense
International audienceThe work presented addresses the combination of anguilliform swimming-based propulsion with the use of an electric sensing modality for a class of unmanned underwater vehicles, and in particular investigates the relative influence of adjustments to the swimming gait on the platform's displacement speed and on sensing performance. This influence is quantified, for a relevant range of swimming gaits, using experimental data recordings of displacement speeds, and a boundary element method-based numerical simulation tool allowing to reconstruct electric measures. Results show that swimming gaits providing greater movement speeds tend to degrade sensing performance. Conversely, gaits yielding accurate sensing tend to prove slower. To reconcile opposing tendencies, a simple action-perception cost function is designed, with the purpose of adjusting an anguilliform swimmer's gait shape, in accordance with respective importance afforded to action (i.e. movement speed) and perception
Multi-Objective Design Optimization of the Leg Mechanism for a Piping Inspection Robot
This paper addresses the dimensional synthesis of an adaptive mechanism of
contact points ie a leg mechanism of a piping inspection robot operating in an
irradiated area as a nuclear power plant. This studied mechanism is the leading
part of the robot sub-system responsible of the locomotion. Firstly, three
architectures are chosen from the literature and their properties are
described. Then, a method using a multi-objective optimization is proposed to
determine the best architecture and the optimal geometric parameters of a leg
taking into account environmental and design constraints. In this context, the
objective functions are the minimization of the mechanism size and the
maximization of the transmission force factor. Representations of the Pareto
front versus the objective functions and the design parameters are given.
Finally, the CAD model of several solutions located on the Pareto front are
presented and discussed.Comment: Proceedings of the ASME 2014 International Design Engineering
Technical Conferences \& Computers and Information in Engineering Conference,
Buffalo : United States (2014
A Hybrid Dynamic Model Of An Insect-Like MAV With Soft Wings
International audienceThis paper presents a hybrid dynamic model of a 3-D aerial insect-like robot. The soft-bodied insect wings modeling is based on a continuous version of the Newton-Euler dynamics where the leading edge is treated as a continuous Cosserat beam. These wings are connected to an insect's rigid thorax using a discrete recursive algorithm based on the Newton-Euler equations. Here we detail the inverse dynamic model algorithm. This version of the dynamic model solves the following two problems involved in any locomotion task: 1â—¦) it enables the net motion of a reference body to be computed from the known data of internal motions (strain fields); 2â—¦) it gives the internal torques required to impose these internal (strain fields) motions. The essential fluid effects have been taken into account using a simplified analytical hovering flight aerodynamic model. To facilitate the analysis of numerical results, a visualization tool is developed
Macro-continuous dynamics for hyper-redundant robots: application to locomotion bio-inspired by elongated animals
International audienceThis article presents a unified dynamic modeling approach of continuum robots. The robot is modeled as a geometrically exact beam continuously actuated through an active strain law. Once included into the geometric mechanics of locomotion, the approach applies to any hyper-redundant or continuous robot devoted to manipulation and/or locomotion. Furthermore, exploiting the nature of the resulting models as being a continuous version of the Newton-Euler models of discrete robots, an algorithm is proposed which is capable of computing the internal control torques (and/or forces) as well as the rigid overall motions of the locomotor robot. The efficiency of the approach is finally illustrated through many examples directly related to the terrestrial locomotion of elongated animals as snakes, worms or caterpillars and their associated bio-mimetic artifacts
A hybrid dynamic model for bio-inspired soft robots - Application to a flapping-wing micro air vehicle.
International audienceThe paper deals with the dynamic modeling of bio-inspired robots with soft appendages such as flying insect-like or swimming fish-like robots. In order to model such soft systems, we propose to use the Mobile Multibody System framework introduced in [1][2][3]. In such a framework, the robot is considered as a tree-like structure of rigid bodies where the evolution of the position of the joints is governed by stress-strain laws or control torques. Based on the Newton-Euler formulation of these systems, we propose a new algorithm able to compute at each step of a time loop both the net and passive joint accelerations along with the control torques supplied by the motors. To illustrate, based on previous work [4], the proposed algorithm is applied to the simulation of the hovering flight of a soft flapping-wing insect-like robot (see the attached video)
Poincaré-Cosserat equations for Lighthill three-dimensional dynamic model of a self propelled eel devoted to Robotics
International audienceIn this article, we propose a dynamic model of the three-dimensional eel swim. This model is analytical and suited to the on-line control of eel-like robots. The proposed solution is based on the Large Amplitude Elongated Body Theory of Lighthill and a working frame recently proposed in [1] for the dynamic modeling of hyper-redundant robots. This working frame was named "macro-continuous" since at this macroscopic scale, the robot (or the animal) is considered as a Cosserat beam internally (and continuously) actuated. This article proposes new results in two directions. Firstly, it achieves an extension of the Lighthill theory to the case of a self propelled body swimming in three dimensions, while including a model of the internal control torque. Secondly, this generalization of the Lighthill model is achieved due to a new set of equations which is also derived in this article. These equations generalize the Poincaré equations of a Cosserat beam to the case of an open system containing a fluid stratified around the slender beam
Estimation of relative position and coordination of mobile underwater robotic platforms through electric sensing.
International audienceIn the context of underwater robotics, positioning and coordination of mobile agents can prove a challenging problem. To address this issue, we propose the use of electric sensing, with a technique inspired by weakly electric fishes. In particular, the approach relies on one or several of the agents applying an electric field to their environment. Using electric measures, others agents are able to reconstruct their relative position with respect to the emitter, over a range that is function of the geometry of the emitting agent and of the power applied to the environment. Efficacy of the technique is illustrated using a number of numerical examples. The approach is shown to allow coordination of unmanned underwater vehicles, including that of bio-inspired swimming robotic platforms
Fast Dynamics of a three dimensional eel-like robot: comparisons with Navier-Stokes simulations
International audienceThis article proposes a dynamic model of the swim of elongated ï°£shes suited to the on-line control of bio-mimetic eel-like robots. The approach is analytic and can be considered as an extension of the original reactive "Large-Elongated-Body-Theory" of Lighthill to the three dimensional self propulsion augmented of a resistive empirical model. While all the mathematical fundamentals are detailed in [1], this article 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 ï°£sh head and the ï°£eld of internal control torque from the knowledge of the imposed internal strain ï°£elds. Based on the Newton-Euler formalism of robots dynamics, this algorithm works faster than real time. As far as precision is concerned, many tests obtained with several planar and three dimensional gaits are reported and compared (in the planar case) with a Navier-Stokes solver, devoted until today to the planar swim. The comparisons obtained are very encouraging since in all the cases we tested, the diï°¢erences between our simpliï°£ed and reference simulations do not exceed ten per cent