Wireless actuation within hermetically enclosed precision systems. - In: Proceedings of the 20th International Conference of the European Society for Precision Engineering and Nanotechnology, (2020), S. 73-74
Modelling and control of fast-switching solenoid direct injection valves using a new magnetics library. - In: Proceedings of Asian Modelica Conference 2020, Tokyo, Japan, October 08-09, 2020, (2020), S. 49-58
https://doi.org/10.3384/ecp202017449
High frequency DC-DC converter for an integrated electrical excitation of an axial flux machine with fiber-composite rotor: a multidisciplinary approach. - In: CIPS 2020, (2020), S. 371-376
https://ieeexplore.ieee.org/document/9097711
Thermal simulation for power density optimization of SiC-MOSFET automotive inverter. - In: CIPS 2020, (2020), S. 333-338
https://ieeexplore.ieee.org/document/9097704
Characterization of GPS disciplined oscillators using a laboratory GNSS simulation testbed. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
This paper introduces a testbed to characterize the performance of GPS disciplined oscillators using a GNSS signal simulator and a measurement system based on software-defined radios and digital signal processing that allows to examine the stability of up to four devices with sub-nanosecond precision, time-coherently for 1 PPS and 10 MHz signals, in a controllable laboratory environment with reproducible and adjustable GNSS signal settings over a long-term observation period. To demonstrate the effectiveness of this method, four devices of one specific low-cost GPSDO type available to the authors are characterized and compared in terms of their positional accuracy and their time and frequency stability in steady state and during stabilization.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234932
Measurement of drift and jitter of network synchronized distributed clocks. - In: IEEE IFCS-ISAF 2020, (2020), insges. 8 S.
We propose a measurement setup for simultaneous measurement of drift and jitter of network synchronized distributed clocks using only off-the-shelf components. A network interface card with hardware timestamping capability and a local GPS-synchronized PTP grandmaster combined with appropriate post-processing enable absolute time measurement with sub-microsecond accuracy. The setup is explained in detail and its use exemplified by a 34 day measurement campaign. By polling a selection of globally distributed, GPS-synchronized NTP servers, delay asymmetry measurements were enabled. A detailed analysis of results illustrates the time-variant statistical properties of the jitter.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234926
Stochastic modeling of short and long term clock skew. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
Traditional black box clock skew models are either the power-law noise model or a more recent approach based on auto-regressive (AR) filters. Unfortunately, neither algorithm can accurately model short and long term skew due to limited degrees of freedom or stability constraints. We propose a novel model that employs the current AR algorithm recursively with appropriate pre- and post-processing to achieve numeric stability and accurate reproduction of short and long term effects. The model coefficients are derived from a measured skew signal, with the model output matching an exemplary original signal closely in terms of Allan variance and time-domain behavior.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234818
Characterizing GPS disciplined oscillators for distributed vehicle-to-X measurement applications. - In: IEEE IFCS-ISAF 2020, (2020), insges. 4 S.
In this paper, we analyze the reference signal stability of 1 PPS and 10 MHz signals provided by a low-cost GPS disciplined oscillator under application specific conditions using a comparable light-weight measurement system based on software defined radio and digital signal processing. In mobile measurement scenarios, GPS signal impairments are inevitable, due to obstacles such as buildings, street canyons, bridges, and tunnels. Therefore, we preliminarily characterize four GPSDOs under test in a stationary setup using controlled GPS reception loss to drive them into alternating operation modes, namely free-run, disciplined and holdover mode. Further, we conducted a more than 100 km real-world diversified test drive to characterize the performance of the particular GPSDO as realistically as possible for the intended use in mobile V2X measurements.
https://doi.org/10.1109/IFCS-ISAF41089.2020.9234915
Liquid metal swirling flow affected by transverse magnetic field. - In: Magnetohydrodynamics, Bd. 56 (2020), 2/3, S. 121-129
In this work we study numerically liquid metal flow in a squareduct under the influence ofa transverse magnetic field applied in a spanwise direction (coplanar). The key interest of thepresent study is an attempt of passive control of flow regimesdeveloped under magnetic fieldand thermal loads by applying specially shaped conditions,such as swirling, at the duct inlet.In this paper, we report results of numerical simulations ofthe interaction of swirling flow andtransverse magnetic field in a square duct flow. Analysis of the obtained regimes might beimportant for the development of an experimental setup, in order to design corresponding inletsections.
https://doi.org/10.22364/mhd.56.2-3.3
MHD Taylor-Couette flow with insulating walls at periodic condition and low magnetic Reynolds number. - In: Magnetohydrodynamics, Bd. 56 (2020), 2/3, S. 103-112
This work studies turbulent behavior in Taylor-Couette flow of an electrically conducting fluid between two co-axial and infinitely long insulating cylinders in the presence of an axial magnetic field at a low magnetic Reynolds number. The inner cylinder rotates and the outer one is kept stationary. Direct numerical simulation was conducted to study the problem with Reynolds numbers of 4000 and 8000 with different Hartmann numbers. The results show a continuous suppression of turbulence in the flow under the applied magnetic field. The mean flow profile is not directly affected by the magnetic field, but its transformation depends on the decrease of turbulent fluctuations and wall normal momentum transport. With increasing Hartmann number, the observed decrease of Taylor vortex flow is accompanied by the elongated axial wavelengths, confirming the theoretical prediction of linear stability theory. A comparison of the considered case of insulating cylinders with a previous study with conducting cylinders also indicates a difference between these two cases and highlights a significant impact of the electric boundary conditions on turbulence.
https://doi.org/10.22364/mhd.56.2-3.1