[Show abstract][Hide abstract] ABSTRACT: This article presents a set of generic tools for multibody system dynamics devoted to the study of bio-inspired locomotion in robotics. First, archetypal examples from the field of bio-inspired robot locomotion are presented to prepare the ground for further discussion. The general problem of locomotion is then stated. In considering this problem, we progressively draw a unified geometric picture of locomotion dynamics. For that purpose, we start from the model of discrete mobile multibody systems (MMSs) that we progressively extend to the case of continuous and finally soft systems. Beyond these theoretical aspects, we address the practical problem of the efficient computation of these models by proposing a Newton–Euler-based approach to efficient locomotion dynamics with a few illustrations of creeping, swimming, and flying.
[Show abstract][Hide abstract] ABSTRACT: Bio-inspired by moth or humming-birds, several micro air vehicles (MAV) have recently been developed. In these systems, the motion of the lifting surface is complex and modeled by flapping motion-controlled soft wings. The synchronization of the actuated periodic flapping motion of the wings and that of passive twisting degrees of freedom (dof) allows producing hovering flight. Depending on the feature of the MAV such as stiffness, and geometric characteristic, hovering flight can be naturally stable or not. In the first case hovering is obtained via an open loop control (or a local closed loop control) while in the second case a global control strategy is required to achieve the same objectives. Thus, it is crucial to take into account the influence of the design of the MAV on the control in order to choose an appropriate morphology that can reduce the burden of control. In this paper mathematical tools and methodologies are proposed to achieve this objective and reduce the computational cost of control.
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: The 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 , , . 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 , the proposed algorithm is applied to the simulation of the hovering flight of a soft flapping-wing insect-like robot (see the attached video).
Proceedings - IEEE International Conference on Robotics and Automation 05/2014; DOI:10.1109/ICRA.2014.6907372
[Show abstract][Hide abstract] ABSTRACT: This paper presents an extension of Lighthill’s large-amplitude elongated-body theory of fish locomotion which enables the effects of an external weakly non-uniform potential flow to be taken into account. To do so, the body is modelled as a Kirchhoff beam, made up of elliptical cross-sections whose size may vary along the body, undergoing prescribed deformations consisting of yaw and pitch bending. The fluid velocity potential is decomposed into two parts corresponding to the unperturbed potential flow, which is assumed to be known, and to the perturbation flow. The Laplace equation and the corresponding Neumann’s boundary conditions governing the perturbation velocity potential are expressed in terms of curvilinear coordinates which follow the body during its motion, thus allowing the boundary of the body to be considered as a fixed surface. Equations are simplified according to the slenderness of the body and the weakness of the non-uniformity of the unperturbed flow. These simplifications allow the pressure acting on the body to be determined analytically using the classical Bernoulli equation, which is then integrated over the body. The model is finally used to investigate the passive and the active swimming of a fish in a Kármán vortex street.
[Show abstract][Hide abstract] ABSTRACT: This 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: 1°) it enables the net motion of a reference body to be computed from the known data of internal motions (strain fields); 2°) 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 (see video available at ).
Robotics and Biomimetics (ROBIO), 2012 IEEE International Conference on; 12/2012
[Show abstract][Hide abstract] ABSTRACT: In 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.
Proceedings - IEEE International Conference on Robotics and Automation 05/2012; DOI:10.1109/ICRA.2012.6224686
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present a unified dynamic modeling approach of (elongated body) continuum robots. The robot is modeled as a geometrically exact beam continuously actuated through an active strain law. Once included in the geometric mechanics of locomotion, the approach applies to any hyperredundant or continuous robot that is devoted to manipulation and/or locomotion. Furthermore, by the exploitation of the nature of the resulting model of being a continuous version of the Newton–Euler model of discrete robots, an algorithm is proposed that is capable of computing the internal control torques (and/or forces), as well as the rigid net motions of the robot. In general, this algorithm requires a model of the external forces (responsible for the self-propulsion), but we will see how such a model can be replaced by a kinematic model of a combination of contacts that are related to terrestrial locomotion. Finally, in this case, which we name “kinematic locomotion,” the algorithm is illustrated through many examples directly related to elongated body animals, such as snakes, worms, or caterpillars, and their associated biomimetic artifacts.
[Show abstract][Hide abstract] ABSTRACT: The 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.
[Show abstract][Hide abstract] ABSTRACT: This paper reports the first results from a program of work aimed at developing a swimming robot equipped with electric sense. After having presented the principles of a bioinspired electric sensor that is now working, we will build the models for electrolocation of objects that are suited to this kind of sensor. The produced models are in a compact analytical form in order to be tractable on the onboard computers of the future robot. These models are tested by comparing them with numerical simulations based on the boundary elements method. The results demonstrate the feasibility of the approach and its compatibility with online objects electrolocation, i.e., another parallel program of ours.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a unified dynamic modeling approach of bio-inspired continuum robots. The locomotion analysis shows that how this dynamic model work with the environ-mental interaction model in order to produce locomotion. The resulting algorithm exploits a continuous version  of the Newton-Euler models of discrete structures and, is ca-pable of computing the net motions as well as the inter-nal control torques (and/or forces) of the continuum robot. The efficiency of the algorithm is finally illustrated through many examples directly related to the terrestrial locomotion of elongated animals as snakes, worms and caterpillars.
[Show abstract][Hide abstract] ABSTRACT: In bio-inspired robotics, use of a Central Pattern Generator (CPG) to coordinate actuation is fairly common. The gait achieved depends on a number of CPG parameters, which can be adjusted to control the robot's motion. This paper presents an output feedback motion control framework, addressing issues encountered when dealing with this type of control problem, including partial state measurements and system uncertainty. Efficacy of the presented approach is illustrated by results of numerical simulations in the case of a swimming robot.
[Show abstract][Hide abstract] ABSTRACT: The paper deals with the modeling of a fish-like robot equipped with the electric sense, suited to study sensorimotor loops. The proposed multi-physics model merges a swimming dynamic model of a fish-like robot with an electric model of an embedded electrolocation sensor. Based on a TCP-IP and threaded framework, the resulting simulator works in real time. After presenting the modeling aspects of this work, this article focuses on two numerical studies. In the first, the interactions between body deformations and perception variables are studied and a current correction process is proposed. In the second study, an electric exteroceptive feedback loop based on a direct current measurement method is designed and tested for obstacle avoidance.
Intelligent Robots and Systems (IROS), 2011 IEEE/RSJ International Conference on; 09/2011
[Show abstract][Hide abstract] ABSTRACT: We present an analytical model of a sensor for the navigation of underwater vehicles by the electric sense. This model is inspired from the electroreception structure of the electric fish. In our model, that we call the poly-spherical model (PSM), the sensor is composed of n spherical electrodes. Some electrodes play the role of current-emitters whereas others play the role of current-receivers. By imposing values of the electrical potential on each electrode we create an electric field in the vicinity of the sensor. The region where the electric field is created is considered as the bubble of perception of the sensor. Each object that enters this bubble is electrically polarized and creates in return a perturbation. This perturbation induces a variation of the measured current by the sensor. The model is tested on objects for which the expression of the polarizability is known. A unique off-line calibration of the poly-spherical model permits to predict the measured current of a real immersed sensor in an aquarium. Comparisons in a basic scene between the predicted current given by the poly-spherical model and the measured current given by our test bed show a very good agreement, which confirms the interest of using such fast analytical models for the purpose of navigation.
Robotics and Biomimetics (ROBIO), 2010 IEEE International Conference on; 01/2011
[Show abstract][Hide abstract] ABSTRACT: This 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.
[Show abstract][Hide abstract] ABSTRACT: The paper deals with the modeling of a fish- like robot equipped with the electric sense, suited to study sensorimotor loops. The proposed multi-physics model merges a swimming dynamic model of a fish-like robot with an electric model of an embedded electrolocation sensor. Based on a TCP- IP and threaded framework, the resulting simulator works in real time. After presenting the modeling aspects of this work, this article focuses on two numerical studies. In the first, the in- teractions between body deformations and perception variables are studied and a current correction process is proposed. In the second study, an electric exteroceptive feedback loop based on a direct current measurement method is designed and tested for obstacle avoidance.
[Show abstract][Hide abstract] ABSTRACT: In this article, we describe a dynamic model of the three-dimensional eel swimming. This model is analytical and suited to
the online control of eel-like robots. The proposed solution is based on the Large Amplitude Elongated Body Theory of Lighthill
and a framework recently presented in Boyer et al. (IEEE Trans. Robot. 22:763–775, 2006) for the dynamic modeling of hyper-redundant robots. This framework 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 introduces
new results in two directions. Firstly, it extends 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 are also derived in this article. These equations generalize the Poincaré equations
of a Cosserat beam to an open system containing a fluid stratified around the slender beam.
[Show abstract][Hide abstract] ABSTRACT: In 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  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 uid stratied around the slender beam.