Modellierung der Drehsteifigkeit dünner Festkörpergelenke in der Präzisionsgerätetechnik. - In: Jahrbuch Optik und Feinmechanik, ISSN 0075-272X, Bd. 64 (2018), S. 139-165
Festkörpergelenke werden seit langem in verschiedensten Bereichen der Feinwerktechnik eingesetzt, besonders dort, wo erhöhte Anforderungen an die Präzision bestehen. Beispiele dafür sind Präzisionswaagen und Massekomparatoren, die bereits eine beeindruckende Leistungsfähigkeit erreicht haben. Dies ist nicht zuletzt auf die genaue Kenntnis der mechanischen Eigenschaften und deren Modellierung zurückzuführen. Dennoch ergeben viele in der Literatur verfügbare analytische Modellgleichungen zur Berechnung der Drehsteifigkeit der hier typischen, besonders dünnen Festkörpergelenke eine Abweichung von rund 10 % gegenüber dem 3D-Modell basierend auf der Finiten-Elemente-Methode. Dies wird anhand der genauen Betrachtung des Spannungszustandes im belasteten Gelenk aufgezeigt und ist ein relevanter Aspekt für die Entwicklung von Geräten für Präzisionsanwendungen und deren Justierung. Der Beitrag beleuchtet dieses Phänomen im Detail, zeigt Grenzen verschiedener Modellansätze in Abhängigkeit der Geometrie auf und bietet dem Leser einen Vorschlag zur präzisen Modellierung in einem großen Parameterraum an, die ohne eine aufwändige Finite-Elemente-Analyse auskommt.
On the design of long range multiaxial nanofabrication machines based on Cartesian nanopositioning systems with additional ultra precision rotations. - In: 33rd ASPE Annual Meeting, ISBN 978-1-887706-77-3, (2018), S. 527-532
As result of a comprehensive literature survey, the majority of nanopositioning and nanomeasuring machines (NPMMs) are based on three independent linear movements in a Cartesian coordinate system with a repeatability in the nanometer range. This in combination with the specific nature of sensors and tools (further on summarized as tool) limits the addressable part geometries. Depending on the tool in use, spherical and aspherical geometries as well as free-form surfaces cannot be measured or only to a certain limit. This article contributes to the enhancement of multiaxial machine structures by the implementation of rotational movements while keeping the precision untouched. A systematic parameter based dynamic evaluation approach was developed for the creation and selection of adequate machine structures for multiaxial nanopositioning systems (DOF>3). To support the selection, detailed parameter sets are generated containing explicit moving ranges, uncertainties, resolutions, reproducibilities and costs. The parameter sets are further detailed with derived characteristics such as deformations, vibrations or thermal influences due to the additional rotations based on FEA-models and verified experimental data. This approach is also applied to the rotation of the sample. The results are compared to those of the tool rotation and mixed versions. After all, the knowledge gained, is formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines. Out of these investigations, a rotation of the tool is a favourable solution. Kinematics with a high degree of fulfilment consider a common instantaneous center of rotation in the tool center point (T). Compared to a fixed tool position this leads to shifting deviations of (T) due to deformations of the frame depending on the actual mass distribution. In addition, deviations of (T) are caused by vibrations and thermal influences of the positioning system. The strict separation of the force frame and the metrology frame, thermal shielding and direct measuring systems for the deviation of (T) can compensate the effects that are dependent on the selected overall structure and positioning system.
Ultra precise motion error measurement of rotation kinematics for the integration in nanomeasuring and nanofabrication machines. - In: 33rd ASPE Annual Meeting, ISBN 978-1-887706-77-3, (2018), S. 122-126
The semiconductor industry has been done an incomparable progress during the last 60 years. With the ongoing reduction of the structure size by new fabrication techniques the nanomeasurement systems have also increased their performance [1]. Besides this development the measurement and fabrication of freeform surfaces, aspheric lenses or high aspect ratio structures are still highly challenging. There are different commercial and scientific approaches to measure on freeform surfaces [2, 3, 4, 5].
On modeling the bending stiffness of thin semi-circular flexure hinges for precision applications. - In: Actuators, ISSN 2076-0825, Bd. 7 (2018), 4, 86, S. 1-16
Compliant mechanisms based on flexure hinges are widely used in precision engineering applications. Among those are devices such as precision balances and mass comparators with achievable resolutions and uncertainties in the nano-newton range. The exact knowledge of the mechanical properties of notch hinges and their modeling is essential for the design and the goal-oriented adjustment of these devices. It is shown in this article that many analytical equations available in the literature for calculating the bending stiffness of thin semi-circular flexure hinges cause deviations of up to 12% compared to simulation results based on the three-dimensional finite element model for the considered parameter range. A close examination of the stress state within the loaded hinge reveals possible reasons for this deviation. The article explains this phenomenon in detail and shows the limitations of existing analytical models depending on specific geometric ratios. An accurate determination of the bending stiffness of semi-circular flexure hinges in a wide range of geometric parameters without the need for an elaborate finite element analysis is proposed in form of FEM-based correction factors for analytical equations referring to Euler-Bernoulli's beam theory.
https://doi.org/10.3390/act7040086
Influence of additional rotational movements on the measurement uncertainty of nanomeasuring, nanopositioning and nanofabrication machines. - In: Sensors and Measuring Systems, (2018), S. 168-171
The measurement of freeform surfaces, aspheric lenses or the sidewall roughness of high aspect ratio structures are a current challenge in nanometrology. There are different publications and commercial products with approaches to perform a measurement of those quantities [1, 2, 3, 4]. Beside the nanomeasurement the nanofabrication on curved freeform surfaces is an upcoming trend. The measurement or the fabrication on a freeform surface is limited by the possible tilt angle between the tools working axis and the local surface normal. To achieve larger angles and a minimal measurement uncertainty the tool must be placed optimal to the local surface. According to those requirements, concepts are developed to increase the degree of freedom in positioning. The x-y-z translational positioning system of an nanomeasuring machine (NMM-1) with a working volume of 25×25×5mm^3 [5] will be extended by additional rotational movements. The rotation can be achieved by three basic principles of motion which are the rotation of the sample, of the tool or a combination of the tool and the sample rotation. In a first step the principles of motion are described by their bare geometrical properties and decoupled from real positioning systems. A constant instantaneous centre of motion in the sensor measurement point is determined as the optimal principle for a rotational system. This principle is further investigated and is made concrete by choosing a combination of kinematics [6]. A vectorial approach based on the GUM [7] is used to evaluate the influence of the axes error motion on the measurement result. The method and the results for a combination of a rotary table and a goniometer axis are described in detail.
https://ieeexplore.ieee.org/document/8436163
Qualification of the endurance strength enhancement of silane coated concrete parts. - In: Measurement science and technology, ISSN 1361-6501, Bd. 29 (2018), 10, S. 104003, insges. 9 S.
https://doi.org/10.1088/1361-6501/aad6c1
Theoretical investigations on the behavior of artificial sensors for surface texture detection. - In: Dynamical systems in theoretical perspective, (2018), S. 311-321
Animal vibrissae are used as natural inspiration for artificial tactile sensors, e.g., the mystacial vibrissae enable rodents to perform several tasks in using these tactile hairs: object shape determination and surface texture discrimination. Referring to the literature, the Kinetic Signature Hypothesis states that the surface texture detection is a highly dynamic process. It is assumed that the animals gather information about the surface texture out of a spatial, temporal pattern of kinetic events. This process has to be analyzed in detail to develop an artificial tactile sensor with similar functionalities. Hence, we set up a mechanical model for theoretical investigations of the process. This model is analyzed in two different directions using numerical simulations: at first a quasi-static and then a fully dynamic description.
https://doi.org/10.1007/978-3-319-96598-7_25
Experimental qualification of the strength enhancement of coated concrete parts. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 147-148
Investigations of the geometrical scaling in the systematic synthesis of compliant mechanisms. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 67-68
The implementation of ultra precision rotations to multiaxial nanofabrication machines: challenges and solution concepts. - In: Proceedings of the 18th International Conference of the European Society for Precision Engineering and Nanotechnology, (2018), S. 65-66
Existing long-range nanopositioning and nanomeasuring machines are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools (further on summarized as tool) limits the addressable part geometries. This article contributes to the enhancement of multiaxial machine structures by the implementation of rotational movements while keeping the precision untouched. A parameter based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify general solution concepts and adequate substructures. First evaluations show high potential for sample scanning mode variants considering linear movements of the object in combination with angular movements of the tool, considering a goniometer setup in specific. The evaluation system is further enhanced by the implementation of data based on comprehensive design catalogues, uncertainty calculations and CAD-model based footprint analysis for specific setups. To support the selection, detailed parameter sets are generated containing explicit moving ranges, uncertainties, resolutions, reproducibilities and costs. This approach is also applied to the rotation of the object. The results are compared to the tool rotation and mixed versions. After all, the knowledge gained, is formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines.