Sébastien Barthélemy

Stability Measure of Postural Dynamic Equilibrium Based on Residual Radius

This paper formalizes the robustness of a virtual human dynamic equilibrium through the residual radius of its admissible generalized force set. The admissible generalized force set is defined as the image of the contact force constraints (corresponding to the Coulomb model) in the generalized force space. This set is approximated by a polyhedron and its residual radius is computed using a linear program. The measure relevance is analyzed from experimental data of a sit-to-stand motion on which residual radius is evaluated.

LQP-Based Controller Design for Humanoid Whole-Body Motion

Motion synthesis is a central question in humanoid robotics research. The present paper proposes a generic approach exploiting a quadratic programming method for solving the problem of motion coordination under physical constraints. Details about the problem formulation for dealing with sequences of complex activities are given. The method is illustrated in several examples using the iCub robot. We will show how whole-body control under multiple contact constraints can be achieved. We will also discuss how it is possible to organize the priorities between the tasks in this framework to balance multiple objectives.

LQP controller design for generic whole body motion

This paper deals with robotic control through optimization tools, as Linear Quadratic Program (LQP). This method allows whole-body control, takes account contacts between the robot and the environment, and achieves tasks simultaneously. Each task can have a priority level, so hierarchy is possible. The method is applied on a virtual robot Icub, designed from the real one.

Whole-Body Motion Synthesis with LQP-Based Controller – Application to iCub

This paper deals with the dynamic control of humanoid robots interacting with their environment, and more specifically the behavioral synthesis for dynamic tasks. The particular problem that is considered here is the sequencing of elementary activities subjected to physical constraints, both internal as torque limits and external as contacts, within the framework of posture/tasks coordination. For that we propose to convert the set of tasks into weighted quadratic functions and to minimize their cost with a Linear Quadratic Program. The combination of elementary tasks leads to complex actions, and the continuous evolution of the weights ensures smooth transitions over time, as it is shown in the results.

Parametric Kalman filter for chemical transport models

A computational simplification of the Kalman filter (KF) is introduced – the parametric Kalman filter (PKF). The full covariance matrix dynamics of the KF, which describes the evolution along the analysis and forecast cycle, is replaced by the dynamics of the error variance and the diffusion tensor, which is related to the correlation length-scales. The PKF developed here has been applied to the simplified framework of advection–diffusion of a passive tracer, for its use in chemical transport model assimilation. The PKF is easy to compute and computationally cost-effective than an ensemble Kalman filter (EnKF) in this context. The validation of the method is presented for a simplified 1-D advection–diffusion dynamics.

RobuDOG's Design, Modeling and Control

The paper gives a description of the kinematics and the mechatronics designof RobuDOG, a four-legged robot developed for supporting research and ed-ucation in robotics. Several aspects related to control and programming ofthis platform are considered as its inverse kinematic model, its velocity-basedcontrol and its dynamic behaviour analysis.