Model’s output variance can increase when input variance decreases: a sensitivity analysis paradox?

Pour certains modeles, reduire la variance d’une ou plusieurs variables d’entree provoque une augmentation de la variance de la sortie du modele. Ce phenomene n’est pas concevable dans le cadre des modeles lineaires decrits par le GUM, mais peut etre, en revanche, observable par propagation des distributions sur des modeles non-lineaires. Dans tous les cas, les methodes d’analyse de sensibilite basees sur une decomposition de la variance sont aveugles a ce phenomene. Actuellement, seule la methode des gradients de la variance per-met de le detecter et d’en predire les effets. Dans cette etude, nous nous sommes poses plusieurs questions : (1) quel type de modele peut produire cette inversion …

Using of a uncertainty model of an polyarticulated coordinates measuring arm to validate the measurement in a manufacturing processsus

International audience; Coordinates Measuring Arms (CMA) are increasingly used to control industrial parts and are often an alternative to CMM controls that require conditions of laboratory measurement and involve significant costs. However, the control of uncertainties is often not guaranteed because the measurement process is complex and there is no standard for setting a framework qualification process of the measurement process.The proposed study, in this paper, is a first approach to model the measurement uncertainties of a CMA with contact sensor. The problem is complex because there are many sources of uncertainty, largely due to variability in the handling carried out by the operato…

Simple Large Scale 3D scanner

Abstract A new 3D measuring device for large dimensions is proposed. It is based on the combination of a simple system consisting of a smartphone that measures in stereo a near field with a robotic total station that tracks the position of the camera on a far field. The calibration method is described and the metrological properties obtained make it possible to measure objects of several tens or even hundreds of meters long with errors of the order of a millimeter. This makes it possible to consider the use of the system for many industrial applications

Improvement of segmented bars for the verification of coordinate measuring arms

Incertitude de mesure : de la pratique au calcul

Evaluation of 3D measurement uncertainties in a shop floor for any measurands

Estimation des incertitudes de mesure sur bras polyarticulé portable par méthode de Monte Carlo

International audience; Les bras polyarticulés portables ont progressivement évolué et sont de plus en plus utilisés dans l’industrie. Cependant, à l’heure actuelle, la traçabilité de ces dispositifs est difficile à effectuer et les incertitudes de mesures relatives à l’utilisation de ces appareils ne sont pas quantifiées. Le travail mené consiste à déterminer les incertitudes de mesures associées à la quantification, par un bras polyarticulé portable, des caractéristiques géométriques et dimensionnelles d’une pièce mécanique. Les travaux visant à élaborer un modèle d’incertitude de mesure, sont basés sur la méthode de Monte Carlo du supplément 1 du Guide pour l'expression de l'incertitude …

Evaluer simplement et efficacement les incertitudes de mesure

Methodology for assessment of measuring uncertainties of articulated arm coordinates measuring machine

International audience; The Articulated Arm Coordinate Measuring Machines (AACMM) have gradually evolved and are increasingly used in mechanic industry. At present, measurement uncertainties relating to the use of these devices are not yet well-quantified. The work carried out consists on determining the measurement uncertainties of a mechanical part by an Articulated Arm Coordinate Measuring Machine. The studies aiming to develop a model of measurement uncertainties are based on the Monte Carlo method developed in Supplement 1 of the Guide to Expression of Uncertainty in Measurement [1] but also identifying and characterizing the main sources of uncertainty. A Multi-level Monte Carlo appro…

Good practices and uncertainty assessment process on AACMM

International audience; This paper presents a methodology of evaluating the performance of Articulated Arm Coordinate Measuring Machines (AACMM) for general acceptance-based on the manufacturer's specifications, and on site-based mainly on the application requirements. The first part of this paper takes stock of ISO 10360-12: 2016 standard, which defines the tests that the AACMM user should perform to validate or not the performance of his machine. The various tests recommended by the standard are analyzed and their practical usefulness is explained. In the second part of the paper, an on-site uncertainty estimation methodology is proposed. The interest of the on-site verification methodolo…

PROPOSITION OF AN INTERIM STANDARDIZED TEST FOR ARTICULATED ARM COORDINATE MEASURUNG MACHINE

International audience; Improving the kinematic calibration of a coordinate measuring arm using configuration analysis Precis. Eng. 50 171-82 1. Comparison of the AACMM mechanical deformation during the ISO 10360-12 test and the interim test. 2. Study the possibility of calibration of an AACMM with the proposed interim test, or a similar test (study already engaged). Note: The recommendations concerning the repetition and calculation were detailed in [1] and the recommendations concerning the length of the small artifact and the directions of measurement will be detailed in our coming work.

Virtual machine concept applied to uncertainties estimation in instrumented indentation testing

The basis of the virtual machine concept, which is commonly used in coordinate measuring machines, was implemented to determine more realistic uncertainties on the estimation of the elastic modulus obtained from nanoindentation tests. The methodology is based on a mathematical model applied to simulate the testing process and to evaluate the uncertainties through Monte Carlo simulations whose application depends on the studied system (instrument, material, scale, etc.). The methodology was applied to the study of fused silica (FQ) and steel samples tested in a nanoindentation system. The results revealed that the most relevant sources of uncertainty are related to the calibration procedure,…

Optimization of the straightness measurements on rough surfaces by Monte Carlo simulation

Summary The straightness error of a coordinate measuring machine (CMM) is determined by measuring a rule standard. Thanks to a reversal technique, the straightness uncertainty of the CMM is theoretically dissociated from the straightness uncertainty of the rule. However, stochastic variations of the whole measurement system involve uncertainties of the CMM straightness error. To quantify these uncertainties, different sources of stochastic variations are listed with their associated probability density functions. Then Monte Carlo methods are performed first to quantify error and secondly to optimize measurement protocol. It is shown that a 5-measurement distance from 0.1 mm to each measurem…

Mesure Et Métrologie - Quel Futur ?

International audience

Rapid and robust on-site evaluation of articulated arm coordinate measuring machine performance

International audience

Etalonnage et incertitudes associées de cuves refroidisseurs de lait en vrac de grande capacité

Dans le vocabulaire international de metrologie (edition 2008) [1], la definition de l'etalonnage aevolue. Il y a maintenant deux phases, la premiere est toujours d’etablir la relation entre les valeurs et lesincertitudes de mesure associees fournies par des etalons et les indications correspondantes avec lesincertitudes associees. La deuxieme phase est l’utilisation de cette information pour etablir une relationpermetant d’obtenir le resultat de mesure a partir de l'indication. Ce travail s'inscrit dans le cadre del'amelioration de la qualite et de la tracabilite des reservoirs de grande capacite fabriques par la societe Nevinox(groupe Galactea) a Nevers (France). Le but du papier est de d…

Modèle théorique pour estimer les incertitudes de positionnement de l'effecteur d'un robot parallèle à câble plan

International audience; Les robots parallèles à câbles se développent de plus en plus pour diverses applications. Leur principal avantage réside dans leur capacité de déplacement très rapide sur des distances qui peuvent être importantes. Les déplacements s'effectuent grâce à l'enroulement du câble sur un cabestan. La commande de ces robots est réalisée en pilotant le couple appliqué à chaque câble la position d'équilibre dynamique repose donc sur l'équilibre des efforts appliqués à l'effecteur. La mesure de la position se fait donc de manière indirecte et sans boucle de retour. Pour intégrer ces robots dans un dispositif métrologique, il est nécessaire d'estimer les incertitudes de positio…