Publications

In this paper an insertion method of electrode carriers of straight and curved form is shown for the use in cochlear implants. The aim of using a fluid-mechanical actuator is to minimise the contact between the electrode carrier and the cochlea and consequently avoiding damage during its insertion. First, the synthesis method used for beam-shaped fluid-mechanical actuators is shown. The model-based scaling of parameters demonstrates that actuators must be geometrically similar to reach the same form by same inner pressure. This fact facilitates the experimental investigations using up-scaled demonstrators. Electrode carriers as fluid-mechanical actuators of straight and curved form are designed by theory of curved rods for large deformations. For these carriers, a gentle insertion used a stylet and fluidic actuation in combination and is described analytically by the above mentioned theory. The results demonstrate that the insertion of a curved electrode carrier requires lower pressure and does not need any inner pressure in the end position. The measurements of the deformation behaviour of carrier demonstrators prove the validity of the analytical model. The maximum value of the differences between calculated and measured results of the inner pressure is about 10%.

This paper reports about enhanced compliant mechanisms with flexure hinge based on new analytic and/or FEM models that have been manufactured by state of the art wire EDM technology. Experimental proofs at test benches, equipped with ultra-precise interferometer based length and angular measurement systems, show first time the residual deviation to the intended path of motion with a resolution of nanometers/arc seconds. Theoretically determined and measured data are in good correlation. Repeatability limitations are rather more given by the residual noise of the overall test arrangement and mainly not by the mechanism itself.

Recent research topics in bionics focus on the analysis and synthesis of animal spatial perception of their environment by means of their tactile sensory organs: vibrissae and their follicles. Using the vibrissae, these mammals (e.g., rats) are able to determine an obstacle shape using only a few contacts of the vibrissa with the object. The investigations lead to the task of creating models and a stringent exploitation of these models in form of analytical and numerical calculations to achieve a better understanding of this sense. The sensing lever element vibrissa for the stimulus transmission is frequently modeled as an EulerBernoulli bending rod. We assume that the rod is one-sided clamped and interacts with a rigid obstacle in the plane. But, most of the literature is limited to the research on cylindrical and straight, or tapered and straight rods. The (natural) combination of a cylindrical and pre-curved shape is rarely analyzed. The aim is to determine the obstacles contour by one quasi-static sweep along the obstacle and to figure out the dependence on the precurvature of the rod. To do this, we proceed in several steps: At first, we have to determine the support reactions during a sweep. These support reactions are equate with the observables an animal solely relies on and have to be measured by a technical device. Then, the object shape has to be reconstructed in using only these generated observables. The consideration of the precurvature makes the analytical treatment a bit harder and results in numerical solutions of the process. But, the analysis of the problem results in an extension of a former decision criterion for the reconstruction by the radius of pre-curvature. Is is possible to determine a formula for the contact point of the rod with the profile, which is new in literature in context of pre-curvature.

Täglich ist der Mensch Schwingungen ausgesetzt. Die Normen ISO 2631-5 und VDI 2057-1 haben den Anspruch, standardisierte Mess- und Auswertungsmethoden bereitzustellen, um das Gefährdungspotential solcher mechanischen Einwirkungen einschätzen zu können. Jedoch ist ihre Anwendung nicht trivial. Besonders die Signalaufnahme, -umrechnung und -auswertung erfordern Expertenwissen. In diesem Artikel werden, die in den Normen beschriebenen Vorgehensweisen zur Gefährdungseinschätzung von Ganz-Körper-Schwingungen erläutert, exemplarisch durchgeführt und die Ergebnisse verglichen. Als Beispiel dient ein Proband in einem elektrischen Rollstuhl. Messaufbau, Umrechnungen des Messsignals und die Bewertung der Gefährdung werden dargestellt. Es wird gezeigt, welche Einflüsse die verschiedenen zeitlichen Einwirkungsparameter auf die Berechnungsergebnisse haben. Es kann zusammengefasst werden, dass durch Anwendung der Normen nur unzureichende Prognosen für die Prävention von arbeitsbedingten Gesundheitsgefahren getroffen werden können, da die individuellen Eigenschaften der Probanden nicht berücksichtigt werden. Die Normen haben unterschiedliche Anwendungsbereiche und führen zu verschiedenen Gefährdungsbeurteilungen für ein und dieselbe Schwingungsbelastung.