Frédéric Boyer

Macro-continuous computed torque algorithm for a three-dimensional eel-like robot

This 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 robots Galilean movement and the control torques as a function of the expected internal deformation of the eels body

Model for a Sensor Inspired by Electric Fish

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.

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

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 . (http://www.irccyn.ec-nantes.fr/hebergement/Publications/2007/3721.pdf, 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%.

An Efficient Calculation of Flexible Manipulator Inverse Dynamics

This article presents an efficient recursive computation of the in verse dynamics of flexible manipulators. The algorithm is equiva lent to the nonlinear computed torque law offlexible manipulators. The computation method is based on the generalized Newton-Euler model of flexible manipulators and can be considered as a gener alization of the computed torque control algorithm of rigid robots proposed by Luh, Walker, and Paul for executing joint trajectories. The given algorithm is programmed using Mathematica to get au tomatically an efficient customized symbolic model with a reduced number of operations.

Generalization of Newton-Euler model for flexible manipulators

In this article we propose an extension of the Newton-Euler models to the case of flexible robots. Such models are mainly used today for rigid manipulators. In this case they have given the best results to solve the simulation and control problem, as far as time consumption and programming simplicity are concerned. The extension that we propose is based on the theoretical notion of description formalism of a motion and on the use of the DAlembert principle. The proposed model is intrinsic and concerns any open chain with ponctual joints.

Improved Lighthill fish swimming model for bio-inspired robots: Modeling, computational aspects and experimental comparisons

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.

Underwater Reflex Navigation in Confined Environment Based on Electric Sense

This paper shows how a sensor inspired by an electric fish could be used to help navigate in confined environments. Exploiting the morphology of the sensor, the physics of electric interactions, as well as taking inspiration from passive electrolocation in real fish, a set of reactive control laws encoding simple behaviors, such as avoiding any electrically contrasted object, or seeking a set of objects while avoiding others according to their electric properties, is proposed. These reflex behaviors are illustrated on simulations and experiments carried out on a setup dedicated to the study of electric sense. The approach does not require a model of the environment and is quite cheap to implement.

Further Results on the Controllability of a Two-Wheeled Satellite

This article deals with the open-loop attitude control of a satellite actuated by two reaction wheels when the kinetic momentum is not necessarily equal to zero. Hence this article helps to answer the following question: What is the most to be expected in such conditions? As a matter of fact, the satellite with two reaction wheels and non-null kinetic momentum is not controllable over the entire state space of the spacecraft attitudes. Nevertheless, a five-dimensional subspace of feasible states is potentially reachable. In this article, this subset will be explicitly defined and the reachability of two control objectives related to it will be studied. The first objective deals with steering the satellite from any feasible attitude state to any feasible rest state. The second deals with steering the spacecraft from any feasible state to any given configuration irrespective of the spin about the nonactuated spacecraft axis. This article gives constructive demonstrations of reachability rather than qualitative answers, because it presents open-loop control laws based on path planning compatible with these two objectives. Finally, some simulation results illustrate the feasibility of the approach.

Flexible Links Manipulators: from Modelling to Control

This paper relates recent results obtained in the field of modelling and control of flexible link manipulators and proposes an investigation of the problem raised by this type of systems (at least in the planar case). First, adopting the modal floating frame approach and the Newton–Euler formalism, we propose an extension of the models for control to the case of fast dynamics and finite deformations. This dynamic model is based on a nonlinear generalisation of the standard Euler–Bernoulli kinematics. Then, based on the models recalled we treat the end-effector tracking problem for the one-link case as well as for the planar multi-link case. For the one-link system, we propose two methods, the first one is based on causal stable inversion of linear non-minimum phase model via output trajectory planning. The other one is an algebraic scheme, based on the parametrization of linear differential operators. For the planar multi-link case the control law proposed is based on causal stable inversion over a bounded time domain of nonlinear non-minimum phase systems. Numerical tests are presented together with experimental results, displaying the well behaved of these approaches.

Recursive Inverse Dynamics of Mobile Multibody Systems With Joints and Wheels

This paper is related to the inverse-dynamic modeling of mobile multibody systems articulated with joints and wheels. An easily-implementable algorithm, which is based on Newton-Euler (NE) recursive dynamics, is proposed. From imposed joint and/or actuated-wheel motions, the algorithm performs fast calculations of the control torques, as well as the overall rigid motions involved in locomotion tasks. The engineering applications include tree-like mobile manipulators, satellite-reorientation systems, and modular robots, such as snake-like robots, eel-like robots, and a snakeboard.