Étalonnage (métrologie) | EPFL Graph Search

En métrologie, l'étalonnage est une opération qui concerne les appareils de mesure ou de restitution de données. Deux appareils différents — de conception différente, mais aussi deux appareils de la même gamme (même marque, même modèle) — ne réagissent pas exactement de la même manière. Il faut donc une procédure permettant d'obtenir le même résultat à partir de la même situation initiale. On rencontre aussi l'anglicisme en. Le mot « calibrage » a un sens différent. Étalonnage, vérification et ajustage d'un équipement de mesure D'après le Vocabulaire international de métrologie (VIM) édition 2008, l'étalonnage est une . En clair, cette opération consiste à mesurer la même grandeur avec l'équipement à étalonner et l'équipement étalon, et à comparer les indications des deux instruments, puis à exploiter les résultats de cette comparaison. Prenons par exemple l'étalonnage d'un thermomètre, que nous allons simplifier. Dans un milieu homogène, à une température stabilisée (f

Improving the accuracy of parallel robots

The main objective of this thesis is the accuracy improvement of parallel robots. Accuracy can be improved either by precise manufacturing and assembly or by calibration of each individual robot using a kinematic model which takes geometric deviations into account. The latter has the advantage of leading to low cost solutions but requires sophisticated modeling of the robot's structure which is usually considerably more complex than the derivation of its nominal model. To substantiate the theoretical tools proposed in this thesis two examples of parallel structures are chosen. One of them is the Delta robot with three translational degrees of freedom whereas the second example is a novel structure called Argos having three rotational degrees of freedom. For experimental verification a mock-up was built for each of the two structures. Four calibration steps, modeling, measurement, identification, and implementation are investigated. Investigations were restricted to static errors due to geometric deviations assuming rigid bodies. First a formula is proposed which allows to calculate the number of independent kinematic parameters required for a complete model of a parallel structure. Then a systematic parameterization is introduced and applied to derive four calibration models, two for each example. Two measurement devices are described which were built to determine the position and orientation (pose) of the end-effectors of the two robots. For the Delta robot two additional set-ups using no external (additional) measurement device are proposed. For parameter identification different methods were tested by simulation. Calibration based on the implicit model is proposed as a standard method to calibrate parallel robots. Another calibration method is introduced, referred to as semiparametric calibration, which leads to low computational effort. Fast solutions of the direct and inverse problems had to be found. For the first time al1 the solutions of the direct problem for the Delta robot were found by means of an algorithm introduced by Husty. In addition a fast numeric algorithm for the Delta's direct problem is proposed. The main contribution of this thesis is the experimental verification of calibration methods to improve the accuracy of parallel robots. Using these calibration methods for the two robots, ARGOS and DELTA, between a three- to a twelve-fold improvement of accuracy was achieved and experimentally verified.

EPFL1996

Gas Sampling Using Convection and Humidity Stabilization to Improve Point Gas Sensor Responses

Emily Ann Hammes

Many diseases including sick building syndrome, respiratory problems and cancers can be caused by exposure to high concentrations of toxins commonly used in modern building materials, paints, glues and furniture. To minimize exposure to these toxins, it is important to have air exchange with the outside environment. However, this is usually not energy efficient because the air must be heated or cooled. The purpose of the Intasense project was to resolve this problem by creating an air quality monitor which could determine the current quality of air within the building. This information would then be used to control the ventilation system within an energy efficient building. The purpose of this Ph.D. thesis was both to build a system which could be used to test and calibrate sensors used in the air quality monitor as well as to build its final fluidic platform. During this thesis, three fluidic platforms which include a humidity buffering system were designed, tested and constructed. The first platform was used to test an electrochemical sensor or metal oxide sensor in the laboratory. The second and third platforms held three electrochemical or metal oxide sensors, respectively. They are able to deliver equal quantities of gas to the sensors simultaneously. To date, the multisensor metal oxide platform has been used to create two versions of the Intasense Demonstrator and used to calibrate novel and commercial gas sensors. In both of these applications simultaneous delivery of equal quantities of the sample gas are required for optimal gas sensor signal processing: equal quantities are required so that the amount of analyte in contact with each sensor is the same and simultaneous delivery allows all three sensors to respond concurrently. This was achieved by creating a computational model of gas flow through the system, conducting a parameter sweep and then selecting the optimal set. To confirm that the model and machine error were not significant, a Latin square design was used to test the platform. This test showed that gas delivery to each channel was equal within statistical boundaries. Another major challenge was buffering humidity fluctuations without loss of analyte gas. This was necessary because metal oxide gas sensors are also sensitive to humidity fluctuations. To prevent a false positive caused by a rapid humidity increase, a reversible adsorbent was placed upstream of the gas sensors. However, there was concern that the adsorbent may remove analyte gasses. To optimize the tradeoff between humidity buffering and loss or delay of analyte signal, a computational model of adsorption and desorption of gasses within the filtration system was developed. It was experimentally tested using benzene, carbon monoxide, formaldehyde and nitrogen dioxide. To date ten platforms have been delivered to laboratories throughout Europe. Three are being used to test and calibrate gas sensors. The rest have been used to create demonstrators of the Intasense Air Quality Monitor.

EPFL2016

Improving the accuracy of parallel robots

EPFL1996

Gas Sampling Using Convection and Humidity Stabilization to Improve Point Gas Sensor Responses

Emily Ann Hammes

EPFL2016