Explorando por Autor "Darnieder, Maximilian"

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Adjustment of the relative position of compliant joints within a monolithic mechanism
(Pontificia Universidad Católica del Perú, 2019-09-27) Pomiano Picon, Victor Arturo; Theska, René; Barriga Gamarra, Eliseo Benjamín; Darnieder, Maximilian
The sensitivity of electromagnetic force compensated weighing cells can be enhanced by adjusting the relative distance between two specific joints in its mechanism. However, owing to the difficulties of the adjustment of the flexure hinge position in the compliant mechanism, this adjustment option has not yet been realized. In this scientific thesis, an adjustment device was developed. This adjustment device can be integrated into an EMFC weighing cell and allows adjustments while the balance is in operation. To this end, the guideline VDI 2221 was applied in the design process to develop possible concept solutions. The most suitable option was selected by a technical-economic analysis. The technical realization of the selected solution concept was elaborated based on design guidelines and model equations. The adjustment device was designed to work under a tensile force of up to 15 N. A finite element analysis was performed to evaluate the operation of the adjustment device. This analysis demonstrates the feasibility of the device to shift the flexure hinge within a displacement range of 6 mm. The numerical analysis reveals an angular deflection up to 7.2 arcsec perpendicular to the rotational axis of the adjusted joint. Based on the original model, geometry variations of certain components were investigated to identify optimization possibilities. It was found that the angular distortion can be diminished by a more symmetric setup, especially concerning the linear guide.
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Artificial tactile sensors for surface texture detection-finite element models and numerical treatment
(Pontificia Universidad Católica del Perú, 2017-02-07) Darnieder, Maximilian; Alencastre Miranda, Jorge Hernán; Behn, Carsten
The biological example of vibrissa-type sensors in the animal realm is attributed with impressive sensing capabilities. A recently discovered ability is the surface discrimination task. Preceding research on the topic elaborated certain hypotheses for the functionality of the sensor. The scientiﬁc work is predominantly based on an empirical approach closely related to the biological example. Complex and highly nonlinear mechanical interrelations and tribological aspects of the contact frequently remain unconsidered. In the interplay between the properties of the biological example and the desired technical realization of the sensor concept, the present thesis incrementally develops a complex mechanical model. Its purely numerical treatment is based on the ﬁnite element method framed in the software package ANSYS. Following three modeling stages, the nonlinear structural model is successively implemented ﬁrstly enhancing the contact formulation and secondly including dynamic eﬀects in the computation. The attributes of the biological example like elastic support, pre-curvature and conicity are incorporated and their eﬀects are related to the desired sensor function. Beside the characteristic of the sensor system, elaborated through parameter studies, special emphasis is placed on the determination of the working range and its limiting borderlines as well as the uncovering of problematic aspects of the concept. The complex picture of the static behavior of the sensor system is complemented by a ﬁrst dynamic calculation in close proximity to an experiment, which is conducted in parallel. The juxtaposition of the outcomes are interpreted and a proposal for a measurement strategy is outlined.
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Experimental setup for measuring the mechanical behavior of loaded thin compliant joints with highest precision
(Pontificia Universidad Católica del Perú, 2018-10-25) García Ayala, Braulio Jesús; Darnieder, Maximilian
Compliant mechanisms with flexure hinges represent a defining element of many precision devices in various fields of science and technology. Due to their importance, the ability of modeling their behavior with high precision represents the key for a further enhancement of their performance. The present scientific work contributes to the experimental verification of distinct mechanical models for thin semicircular flexure hinges. For this purpose an experimental setup for the load application on the hinge has been developed, designed and set up. The device is designed to precisely determine the rotational stiffness of thin flexure hinges in their elastic range with a minimal notch height of 50, 75 and 100 ➭m, but can be applied in a wider context in other applications as well. Two sets of hinges were analyzed, both manufactured by wire EDM in different companies. Although both sets were made with the same geometric dimensions, pronounced differences in their stiffness were measured. It is demonstrated that manufacturing has a large impact on the stiffness of the hinges because it affects the resulting geometry in the microscopic scale. The experimental results for one of the hinge sets are in good agreement with the calculations using the finite element method. Further research is required to confirm this trend. This would provide solid evidence for the invalidity of existing analytical stiffness equations for flexure hinges in the considered thickness range.
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Modeling of the elastic mechanical behavior of thin compliant joints under load for highest-precision applications
(Pontificia Universidad Católica del Perú, 2018-10-16) Torres Melgarejo, Mario André; Darnieder, Maximilian
For the most demanding measurement tasks in force metrology flexure hinges in compliant mechanisms represent a key component. To enhance the mechanical properties of devices like weighing cells, the ability of precise modeling of flexure hinges is essential. The present scientific work focuses on the modeling of the mechanical behavior of a single flexure hinge subjected to geometric deviations and non-ideal loading conditions as those encountered in weighing cells. The considered hinge has a semi-circular contour and a large width compared to its minimum notch height. This geometry is modeled using the finite element method. Requirements for a trustworthy and efficient computation are elaborated under the consideration of geometric deviations for later parametric studies. Analytical expressions found in the literature are compared to numerical results to prove the validity of their assumptions for thin hinges. The model is used for studying the deviation of the stiffness in non-ideal flexure hinges. Sources of deviation are identified and described by parameters. The range of values for each parameter is chosen on the basis of available manufacturing technology. Influential parameters are identified through a sensitivity analysis. The effect of loading conditions is studied in the context of the application in weighing cells. For the enhancement of the overall sensitivity, the stiffness of the flexure hinges can be reduced. One option, the alteration of the geometry by adding a flexure strip in the center of the semi-circular flexure hinge is studied in comparison to existing analytical equations. The effects of ground tilts for a single loaded flexure hinge are investigated as a foundation for future modeling of a tilt insensitive state of a weighing cell mechanism (autostatic state). By adjusting the vertical position of the center of mass of the lever, the tilt sensitivity can be reduced to zero. An approach to find the position for this state is presented considering the numerical limitations of finite element modeling. Using this approach, the variation of the sought position is evaluated for different values of the design parameters.