Volume 89, Issue 9

When operating bioreactors, monitoring the process temperature is of great importance. Ultrasonic temperature measurement enables this without the need for sensors inside the bioreactor. The average speed of sound can be determined from the travel time of ultrasonic waves along the path of known length between a transmitter and a receiver positioned in the reactor wall. Due to the temperature dependence of the speed of sound, the average temperature along the path can be calculated from the average speed of sound. If this measurement is carried out for a sufficiently large number of measurement paths in a slice plane of the bioreactor, the temperature field in this plane can be reconstructed. In this article, a measurement setup for measuring temperature distributions is presented. Two different methods are then used to reconstruct temperature fields from the travel times measured with this setup. The first method is the Tikhonov regularization, which is widely used to solve inverse problems. The second method is derived from compressed sensing and can only be used under certain conditions. However, if these conditions are met, this method always provides better results than Tikhonov regularization. In addition to reconstruction results from measured travel times, results from simulated travel times are also presented.

To reduce the error caused by optical device pollution and background value drift in the measurement process of ultra-low emission particulate concentration by light scattering method, an on-line calibration method which can realize self-check and full-range calibration was put forward. The single light source spectral method was used to set up calibration light path, through a strong emphasis on technology achieving light signal extraction. The calibration effect was evaluated based on the dust tunnel system. The results show that the light intensity-modulated technique can significantly improve the measurement accuracy of low concentration particles compared with the constant light intensity technology. When the concentration of particles to be measured is higher than 500 μg/m³, the relative error between the measurement results of the experimental prototype and those of the filter membrane weighing method is less than 10 %. The optimal calibration period of the measuring instrument is 3 hours. When the variation deviation from the calibration light intensity of light intensity modulation is less than 2 %, the relative error between the particle concentration measurement result and the filter membrane weighing method is less than 10 %.

Wire-race bearings are designed to be space-saving and are used in settings, where high precision under continuous high load and torque is required. Thus, load detection is a vital part of their condition monitoring. Measuring load using load cells defeats the space-saving purpose of these bearings. Using virtual sensors, by measuring axial and radial loading indirectly, via an accelerometer attached to the housing of the bearing, can provide an alternative. We extend an earlier approach of a virtual sensor using vibration spectrograms with convolutional neural networks. We propose to use transfer learning to reduce overfitting. Moreover we use Mel-spectrograms instead of standard spectrograms and apply feature augmentation techniques. Thereby the virtual sensor improves validation accuracy from 86.3 % to 94.2 %. Using the logarithmic Mel-scale enables to over-sample the characteristic rollover frequencies which appear up to 500 Hz. Frequency masking shows a higher degree of effect compared to normal spectrograms. Further, we find that by using Mel-spectrograms, the combined latency of the spectrogram generation and forward propagation is reduced by 61.6 %.

This approach analyses the differences between a single flank rolling test and an analytical simulation based on optical measurement data of micro gears. The focus is on a signal-based comparison of the rolling behaviour. Using methods in the time and frequency domain as well as the derivation of methods such as cross-correlation, the capability of this simulative approach is qualified. Due to short measurement times with high correlations to the test rig, an inline integration of this analytical simulation for quality assurance of micro gears in series production will be implemented as part of a holistic approach.

The rapidly advancing trend towards miniaturization in the series production of gears confronts quality assurance with new challenges. In this context, metrological technologies as well as expertise from the field of macro gears can only be transferred to a limited extent. Inline integration of metrology into micro gear production has not yet been implemented in a practicable way. This publication extends the current limits of micro gear quality assurance to date by qualifying the optical method of focus variation technology for complete inline measurements of micro gears in series production time. In detail, this work includes the development of a measurement program by means of Design of Experiments, the establishment of a practicable cleaning process, the evaluation of resulting measurement uncertainties, and a process capability analysis. Consequently, the focus variation technology is qualified for fast, three-dimensional measurements of micro gears with respectively low measurement uncertainties.

In Inductive Power Transfer (IPT) the misalignment between sending and receiving coils is critical and significantly influences both transfer efficiency and charging time. It can be compensated by the use of multiple coils on the sender side. However, by increasing the number of sending coils, the supply circuit becomes big, complex and not easy to control. In this paper, we propose a compact and efficient supply circuit for multi-coil IPT systems, which activates only the coil under the receiving coil. The receiver detection is based on a compact passive peak voltage detector measuring the sending coil voltage variation. The receiver coil position determination is supported by measurements of the sending coil neighbours voltages, so that a stable power transfer to battery-free wireless sensor nodes can be realized. The investigation of the influence of the type, the shape, and the size of conductive materials between sender and receiver shows that the system can distinguish between the receiver coil and different metallic objects such as iron, coins, and copper.

In industrial Computed Tomography (CT), scattered radiation causes a loss of quality of the reconstructed 3D volume. Scatter is caused by photon-matter interaction, whereby a photon is deflected from its initial propagation direction. The most prominent contributor to scattered radiation in the scope of photon energies occurring in industrial CT is Compton Scattering. With the used Beam Hole Array (BHA) technology for scatter correction, scatter intensities are determined by subtracting the primary intensities, which are gathered behind small apertures from the total intensities, which are gathered in the absence of the apertures. Intensities measured behind the apertures are assumed to be scatter free, since the transversal components of the radiation are strongly reduced. The scatter correction is performed by subtracting scatter intensities from primary intensities in the projection image. Improvements are evaluated for a newly developed test specimen considering image quality metrics and dimensional accuracy. The contrast could be improved especially for small structures. Cupping artifacts that express as systematic offset of grey values rising with the penetration length were reduced. Measurement deviations towards tactile references were decreased.

Zusammenfassung In den vergangenen Jahren wurden an der TU-Ilmenau zahlreiche Entwicklungen im Bereich der Nanopositionier- und Nanomesstechnik realisiert. Insbesondere die NMM-1 [Gerd Jäger, Eberhard Manske, Tino Hausotte, Jans-Joachim Büchner, Nanomessmaschine zur abbefehlerfreien Koordinatenmessung, tm – Technisches Messen , 67(7–8), 2000] sowie die NPMM-200 [Eberhard Manske, Gerd Jäger, Tino Hausotte, Felix Balzer, Nanopositioning and Nanomeasuring Machine NPMM-200 – sub-nanometre resolu-tion and highest accuracy in extended macroscopic working areas, euspen’s 17th International Conference , 2017] stellen ein Novum auf dem Gebiet der Koordinatenmesstechnik mit Nanometerpräzision unter Einhaltung des Abbe-Komparatorprinzips [Ernst Abbe, Messaparate für Physiker, Zeitschrift für Instrumentenkunde , 10:446–448, 1890] dar. Ausgehend von diesen Errungenschaften besteht ein nächster Schritt im Messen und Fabrizieren auf stark gekrümmten, asphärischen, oder freigeformten Oberflächen. Vor jenem Hintergrund wird im folgenden Artikel ein Konzept für ein zweiachsiges Rotationsmodul vorgestellt. Dieses dient als Erweiterung für die NMM-1 und ermöglicht über das kartesische Messvolumen von 25 mm × 25 mm × 5 mm25\hspace{0.1667em}\text{mm}\times 25\hspace{0.1667em}\text{mm}\times 5\hspace{0.1667em}\text{mm} hinaus zusätzlich eine Rotation des Tools über 360 ° um die Hochachse sowie 60 ° Neigung. Die Umsetzung erfolgt über eine neuartige sphärische Parallelkinematik. Mit Hilfe eines interferometrischen In-Situ-Referenzmesssystems können die während der Rotationsbewegungen auftretenden translatorischen Positionsabweichungen detektiert werden. Erste Untersuchungen an einem Prototypenaufbau erbringen den Funktionsnachweis des Referenzmesssystems über den gesamten adressierbaren Winkelbereich.