Detectability subspaces and observer synthesis for two-dimensional systems

The notions of input-containing and detectability subspaces are developed within the context of observer synthesis for two-dimensional (2-D) Fornasini-Marchesini models. Specifically, the paper considers observers which asymptotically estimate the local state, in the sense that the error tends to zero as the reconstructed local state evolves away from possibly mismatched boundary values, modulo a detectability subspace. Ultimately, the synthesis of such observers in the absence of explicit input information is addressed

A review of friction models in interacting joints for durability design.

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting systems. Friction is a complex phenomenon and occurs at the interface of two components in relative motion. Over the last several decades, the effects of friction and its modelling techniques have been of significant interests in terms of industrial applications. There is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational conditions. Classical dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity behaviour. Therefore, the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully analysed. Previously the dynamics and impact models used in mechanical joints with clearance have also been examined. The inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational conditions. The revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding surfaces. The presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces, would in turn affect the performance of revolute joints, and puts both reliability and durability of the systems at greater risks of failure. Key literature is identified and a review on the latest developments of the science of friction modelling is presented here. This review is based on a large volume of knowledge. Gaps in the relevant field have been identified to capitalise on for future developments. Therefore, this review will bring significant benefits to researchers, academics and industrial professionals

International conference on the physics of multiply charged ions and international workshop on ECR ion sources /

Conference ... Grenoble, France September 12-16, 198

Ionization equilibrium model for the multiply charged ion formation

A model is proposed to study an argon plasma ionization equilibrium. Considering elastic collisions between electrons, ions and neutrals, it appears that ion-ion collisions are dominant among these processes. From an evaluation of the diffusion coefficient, it is then possible to express an ion life time τ zi which varies as Zi2 (Zi being the ionic charge state). Balance equations are then solved with values of electron number density, electron and ion temperatures as observed in E.C.R. ion sources (Electron Cyclotron Resonance ion sources). The charge state distribution calculated from the model is compared with published experimental results. The agreement is good. It is suggested that increasing electron number density and decreasing neutral gas pressure, all other parameters being kept constant, would allow creation of hydrogen like argon ions.Un modèle d'équilibre d'ionisation d'un plasma d'argon est proposé. La considération des collisions élastiques entre électrons, ions et atomes neutres montre que les collisions ion-ion en sont les processus dominants. A partir de l'évaluation du coefficient de diffusion, on exprime un temps de vie des ions τZi qui varie comme Zi2 (Z i état de charge de l'ion). On résout les équations donnant l'équilibre de la densité des ions dans les différents états de charge Zi en fonction de la densité électronique, des températures électronique et ionique; les valeurs de ces grandeurs sont celles qui sont observées dans les sources à résonance cyclotron des électrons. La distribution des états de charge des ions est calculée et comparée aux résultats de mesure publiés. L'accord est satisfaisant. L'accroissement de la densité électronique et la diminution de la pression de gaz neutre, tous autres paramètres maintenus constants, permettraient la création d'ions argon hydrogénoïde

Capture électronique par des ions lents multichargés lors de collisions d'échange de charge sur des cibles atomiques

Single and double electron capture cross sections for low velocity Ar q+ ions with initial charges 2 ≤ q ≤ 12 colliding with gaseous targets (Kr and Xe) have been measured. In the considered energy range (2 q-10 q keV) it is confirmed that the cross section for single electron capture is quasi energy independent. Comparisons of the actual results are made to theoretically calculated and to previously measured cross-sections. It is shown from all our results that an experimental tendency is observed for σq,q-1 : σq,q-1 ~ Cte q/[IP]3 where q is the incident ion charge, IP the target ionization potential.On présente les résultats de mesure de la section efficace de capture d'un et deux électrons par des ions Arq+ (2 ≤ q ≤ 12) d'énergie comprise entre 2 q et 10 q keV effectuant des collisions d'échange de charge sur des cibles atomiques (Kr et Xe). Après comparaison à des résultats théoriques et à des résultats expérimentaux, on déduit de l'ensemble de nos résultats, une tendance expérimentale selon laquelle σ q,q-1 ~ Cte q/[PI]3 où q est la charge de l'ion incident et PI est le potentiel d'ionisation de la particule cible

INTERACTION D'ONDES H. F. ET BF DANS LE PLASMA D'UNE DÉCHARGE REFLEX

Lorsqu'on injecte des signaux hyperfréquence ou basse fréquence dans le plasma d'une décharge Reflex, des effets non linéaires apparaissent pour des niveaux d'excitation peu importants. L'interaction entre ondes BF et H. F. observée dans différents systèmes faisceau-plasma est mise en évidence et étudiée expérimentalement. Pour une forte excitation hyperfréquence un surcroît d'ionisation important est créé et des raies nouvelles apparaissent dans le spectre des fréquences émises par la décharge.When we introduce high and/or low frequency signals into the plasma of a cold cathode PIG discharge, some non linear-effects appear for relatively low excitation levels. The interactions between high and low frequencies which are often observed in beam-plasma devices are studied here. For high levels of high frequency excitation an enhanced ionization occurs and new lines are observed in the frequency spectra of the discharge

Charge exchange cross sections of argon ions colliding with rare gas targets at keV energies

Single electron capture cross sections have been measured for argon ions with initial charge 2 ≤ q ≤ 12 incident on rare gas targets of helium, neon and argon. The cross sections measured in the energy range 2 q-10 q keV are quasi energy independent. It is observed that the cross sections show oscillations about a mean linear variation in charge. The cross sections show a dependence on the target ionization potential.Les sections efficaces d'échange de charge ont été mesurées pour les ions Arq+ de charge initiale 2 ≤ q ≤ 12 incidents sur des gaz rares : hélium, néon et argon. Les sections efficaces mesurées dans le domaine d'énergie 2 q-10 q keV sont indépendantes de l'énergie. On observe que les valeurs des sections efficaces oscillent autour d'une variation moyenne linéaire en charge. Les sections efficaces présentent une dépendance par rapport au potentiel d'ionisation de la cible