Sensor integration for robotic laser welding processes

The use of robotic laser welding is increasing among industrial applications, because of its ability to weld objects in three dimensions. Robotic laser welding involves three sub-processes: seam detection and tracking, welding process control, and weld seam inspection. Usually, for each sub-process, a separate sensory system is required. The use of separate sensory systems leads to heavy and bulky tools, in contrast to compact and light sensory systems that are needed to reach sufficient accuracy and accessibility. In the solution presented in this paper all three subprocesses are integrated in one compact multipurpose welding head. This multi-purpose tool is under development and consists of a laser welding head, with integrated sensors for seam detection and inspection, while also carrying interfaces for process control. It can provide the relative position of the tool and the work piece in three-dimensional space. Additionally, it can cope with the occurrence of sharp corners along a three-dimensional weld path, which are difficult to detect and weld with conventional equipment due to measurement errors and robot dynamics. In this paper the process of seam detection will be mainly elaborated

Sphericity and twist as functional parameters to represent surface geometries

Topographical measurements of surfaces yield a lot of data which are usually presented by tables of height coordinates or by contour maps. Here a method is described to characterize the surface geometry by just a few parameters which quantify the functional properties: sphericity, twist, and waviness. Examples of applications are given from the field of surface plate measurement. Some measurement techniques based on electronic levels, autocollimators and laserinterferometers are briefly discussed. A resulting accuracy of 0.1 micrometers on a one square meter surface is claimed. With the characteristic parameters, even small geometrical changes due to the environmental conditions temperature and moisture could be recorded and explained

A spatial mechanism for pilot laser alignment with four independently controlled degrees of freedom

Alignment mechanism for optical components, such as mirrors for manipulating laser beams, frequently require four degrees of freedom: two translations and two rotations, i.e. a four axis system. When the adjustment of one axis influences the others, as often will be the case, alignment procedures can be rather cumbersome. The mechanism, described in this paper, has four mutually independent adjustments, each controlling just one axis. Rotation takes place around a fixed point, which can be located freely in space. A computer simulation program has been developed to determine first and higher order deviations. This program proved to be a useful designer's tool to optimize the construction with respect to other system parameters

Optical characteristics of Nd:YAG optics and distortions at high power

The intensity profile and beam caustics of a fiber coupled high power Nd:YAG laser beam through a lens system are studied. The thermal lensing effect and its influence on the beam profile and focal position are discussed. Asymmetry of the intensity profile in planes above and below the focal plane is demonstrated. Also the influence of small pollutions on the protective window is explained. Three different methods are used to measure the occurrence\ud of thermal lensing and quantify these effects

Prozessüberwachung beim Laserreinigen und Laserschichtabtrag durch Anwendung der Plasmaanalyse mittels "low resolution" Spektrometer

Bei der Laserreinigung und dem Laserabtrag an Mehrschichtsystemen ist es von großer Bedeutung, eine Be-schädigung der zu erhaltenden Schicht zu vermeiden. Ein Verfahren zur Überwachung des Laserabtragsprozes-ses ist die "Laser Induzierte Plasma Spektroskopie" (LIPS) [1,2,3,4]. Unterschiede im Schichtaufbau bewirken Veränderungen im Spektrum und der Intensität des Plasmas. Ein Nachteil gebräuchlicher LIPS-Systeme sind die hohen Investitionskosten und die komplexe Handhabung. Neueste Entwicklungen in der Spektrometer-Technologie bieten inzwischen sehr kompakte Systeme mit einfacher Handhabung und niedrigen Investitions-kosten [5,6]. Im Laserzentrum der FH Münster wurde ein "low cost"-LIPS-System zur Laserreinigung/-abtrag in einem Excimer-Laser und Nd:YAG-Laser (mit Frequenzvervielfachung) integriert, um den Abtragprozess zu ü-berwachen und ggf. zu regeln. Die Schichterkennung funktioniert über lineare Korrelation mit vorher aufge-nommenem Referenzspektrum [7,8,9]. Wenn der Korrelationskoeffizient sich einem vorher festgelegten Wert nähert, wird der Abtrags-/Reinigungsprozess gestoppt. Erste Tests haben positive Ergebnisse gezeigt und werden zusammen mit dem Verfahren in diesem Artikel beschrieben

Asbestschade buiten de werkomgeving

Met de totstandkoming van de TNS-regeling is de noodzaak van verdere ontwikkeling van niet-loondienst-gerelateerde schade niet vervallen. De overheid zal trachten verhaal te zoeken bij verantwoordelijke partijen. Slachtoffers kunnen ook niet van de regeling gebruik maken. Alleen langs de civielrechtelijke weg is volledige schadevergoeding mogelijk

Netwerkbeplanning van die riviervloeimeetstasienetwerk in die Oos-Transvaal

Text in AfrikaansWater is in 'n relatief droe land soos Suid-Afrika van uiterste belang. Daar is 'n groot behoefte aan inligting oor die potensieel verbruikbare waterbronne. Hierin word voorsien deur 'n netwerk van riviervloeimeetstasies. Met veranderende ekonomiese toestande word die effektiwiteit van die netwerk van al hoe groter belang. Dit is hier waar netwerkbeplanning 'n aktiewe rol begin speel. As gevolg van die groot variasie in die aard van die opvanggebiede in Suid-Afrika, en die feit dat daar 'n bestaande netwerk is, is dit nodig dat netwerkbeplanning stapsgewys benader word. Die Eerste Fase is 'n leerproses. Die verskillende opvanggebiede in die land kan gegroepeer word en die meetstasies kan geklassifiseer word. 'n Netwerkbeplanningsmetode, "Die ideale netwerk", is ontwikkel en word op drie opvanggebiede toegepas. Die belangrikste resultaat is die klassifikasie van al die meetstasies in die drie opvanggebiede.In a relative dry country like South Africa water is of critical importance. Information on the potential usable water resources is very valuable. This information is supplied by a network of river flow gauging stations. In changing economic times the effectiveness of this network is of increasing importance. Network design plays a major role in insuring this. Network design has to be approached in phases because of the variety in catchment characteristics in South Africa, and the fact that there is an existing network. The First Phase can be regarded as a learning phase, in which all the catchments in the country can be grouped and the stations can be classified. A network design method, · "The ideal network", was developed, and is applied in three catchments. The most important result is the classification of all the existing stations in the three catchments.GeographyM. Sc. (Geografie

Effects of biocontrol bacteria and earthworms on Aphanomyces euteiches root-rot and growth of peas (Pisum sativum) studied in a pot experiment

The role of below-ground interactions between microbial biocontrol agents and soil fauna for combatting soil-borne plant diseases have not been studied sufficiently. This study tested the hypothesis that the beneficial bacterium Bacillus velezensis UCMB5113 and the anecic earthworm Lumbricus terrestris positively influence health and growth of peas (Pisum sativum L.) infested with the pathogen Aphanomyces euteiches causing root-rot disease. A greenhouse fully factorial experiment studied the effects of A. euteches, B. velezensis and L. terrestris on the emergence, growth and health of pea plants. The factors B. velezensis and L. terrestris resulted in taller plants (p = .003 and p = .030). B. velezensis treatment resulted in a higher biomass of shoots and roots (p <= .001 and p = .005). The effects increased with the presence of both factors (p = .036). Earthworms reduced the disease symptoms significantly (p = .032). The decreased disease symptoms caused by the earthworms might be due to the consumption of A. euteiches (direct effect) as well as soil disturbance (indirect effect). Interactions between the microorganisms added and the earthworms were shown. B. velezensis and L. terrestris can be useful for enhancement of plant growth and for biological control of root-rot in peas