Lois du mouvement de Newton | EPFL Graph Search

Les sont un ensemble de principes à la base de la grande théorie de Newton sur le mouvement des corps, appelée mécanique newtonienne ou mécanique classique. À ces lois générales du mouvement, Newton a ajouté la loi de la gravitation universelle permettant d'expliquer aussi bien la chute des corps que le mouvement de la Lune autour de la Terre. Elles sont énoncées pour la première fois dans son ouvrage Philosophiae naturalis principia mathematica en . Première loi de Newton ou principe d'inertie Principe d'inertie Énoncé L'énoncé originel de la première loi du mouvement est le suivant : Dans la formulation moderne de la loi, on parle de mouvement rectiligne uniforme, et on remplace la notion de force par celle de résultante des forces appliquées sur le corps, plus générale. Autrement dit, s'il n'y a pas de force qui s'exerce sur un corps, ou si la somme des forces s'exerçant sur lui est égale au vecteur nul, sa vitesse est constante (la direction, le sens

A Dynamical System Approach for Adaptive Grasping, Navigation and Co-Manipulation with Humanoid Robots

Aude Billard, Salman Faraji, Nadia Barbara Figueroa Fernandez, Mikhail Koptev

In this paper, we present an integrated approach that provides compliant control of an iCub humanoid robot and adaptive reaching, grasping, navigating and co-manipulating capabilities. We use state-dependent dynamical systems (DS) to (i) coordinate and drive the robots hands (in both position and orientation) to grasp an object using an intermediate virtual object, and (ii) drive the robot’s base while walking/navigating. The use of DS as motion generators allows us to adapt smoothly as the object moves and to re-plan on-line motion of the arms and body to reach the object’s new location. The desired motion generated by the DS are used in combination with a whole-body compliant control strategy that absorbs perturbations while walking and offers compliant behaviors for grasping and manipulation tasks. Further, the desired dynamics for the arm and body can be learned from demonstrations. By integrating these components, we achieve unprecedented adaptive behaviors for whole body manipulation. We showcase this in simulations and real-world experiments where iCub robots (i) walk-to-grasp objects, (ii) follow a human (or another iCub) through interaction and (iii) learn to navigate or co-manipulate an object from human guided demonstrations; whilst being robust to changing targets and perturbations.

IEEE2020

Exploitation of a general-coordinate guiding centre code for the redistribution of fast ions in deformed hybrid tokamak equilibria

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé

Self-consistent fast ion distributions are usually obtained using a code that solves the guiding-centre equations, with an appropriate fast ion source (e.g. NBI pinis) and sink (e.g. collision operators). Straight field-line coordinate systems, such as Boozer coordinates, are ordinarily convenient due to the simple separation of longitudinal and cross-field motion, and the simple expression of magnetic differential operators. However, these coordinates are found to be near-singular at the boundary of the internal helical region associated with an n = m = 1 infernal mode. These important configurations are associated with many tokamak phenomena, including snakes and long-lived modes [1] in spherical or more conventional devices. Such internal helical states occur when there is a radially extended region where the safety factor is close to unity. Recent calculations predict the possibility of helical equilibria in ITER hybrid scenarios [2]. The ANIMEC code [3] conveniently produces an equilibrium helical state despite choosing for example an axisymmetric fixed boundary. The corresponding magnetic field in these coordinates can now be fed to the newly devised Particle-In-Cell (PIC) code VENUS-LEVIS, which has been upgraded with phase-space Lagrangian guiding-centre orbit equations [4], embodying full 3D anisotropic electromagnetic fields and a formulation that is independent of coordinate choice, despite retaining intrinsic Hamiltonian properties. The simulations are applied to MAST experiments where the presence of along-lived mode can effect confinement of neutral beam ions, potentially affecting NBI heating and current drive [1]. Neighbouring equilibria from ANIMEC, one helical in the core and the other axisymmetic, permits a precise means of identifying the effect of 3D geometry on the simulated confinement properties of MAST's neutral beam fast ion population. In agreement with the compared experimental data from MAST neutron camera, a significant fraction of particles are pushed out of the helical core region affecting both the measured radial neutron distribution and the heating and current drive properties of the neutral beam population.

Iop Publishing Ltd2012

Exploitation of a general-coordinate guiding centre code for the redistribution of fast ions in deformed hybrid tokamak equilibria

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé

Iop Publishing Ltd2012