Mines ParisTech

About: Mines ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Microstructure. The organization has 6564 authors who have published 11676 publications receiving 359898 citations. The organization is also known as: École nationale supérieure des mines de Paris & École des mines de Paris.

Control of underactuated mechanical systems using switching and saturation

Abstract: In this paper we present some ideas on the control of underactuated mechanical systems using switching and saturation. We focus on the swingup control problem for a class of “gymnast” robots and also for the classical cart-pole system. The design methodology is based on partial feedback linearization in a first stage to linearize the actuated degrees of freedom followed by the control of the transfer of energy from the actuated to the unactuated degrees of freedom in a second stage. In a typical swingup control the desired equilibrium is unstable in the closed loop system as a consequence of the non-minimum phase behavior of the system. For this reason it is necessary to switch controllers at the appropriate time to a controller which renders the equilibrium stable. The successful implementation of the switching control has proved to be nontrivial, both in simulation and in experiment. We discuss both local and global design methods and present some simulation results.

Connectivity on Complete Lattices

Abstract: Classically, connectivity is a topological notion for sets, often introduced by means of arcs. A nontopological axiomatics has been proposed by Matheron and Serra. The present paper extends it to complete sup-generated lattices. A connection turns out to be characterized by a family of openings labelled by the sup-generators, which partition each element of the lattice into maximal terms, of zero infima. When combined with partition closings, these openings generate strong sequential alternating filters. Starting from a first connection several others may be designed by acting on some dilations or symmetrical operators. When applying this theory to function lattices, one interprets the so-called connected operators in terms of actual connections, as well as the watershed mappings. But the theory encompasses the numerical functions and extends, among others, to multivariate lattices.

Progress in the analysis of the mechanisms of ion nitriding

Abstract: In this paper the mechanisms of ion nitriding are discussed, particular attention being paid to d.c. diode nitriding. Recent trends in the analysis of the mechanisms of d.c. diode nitriding are reviewed, emphasizing the importance of the cathode fall region. Diagnostics of active species and calculation of their densities in the plasma are presented and related to modelling. The hydrogen effect and plasma-solid interaction are also discussed. New developments and alternatives to d.c. diode nitriding such as triode nitriding are highlighted.

Additive noise effect in digital phase detection

Abstract: The characteristic polynomials associated with the algorithms used in digital phase detection are used to investigate the effects of additive noise on phase measurements. First, it is shown that a loss factor η can be associated with any algorithm. This parameter describes the influence of the algorithm on the global signal-to-noise ratio (SNR). Second, the variance of the phase error is shown to depend mainly on the global SNR. The amplitude of a modulation of this variance at twice the signal frequency depends on a single parameter β. The material presented here extends previously published results, and as many as 19 algorithms are analyzed.