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The vortex tube can separate a mass flow into a hot and cold mass flow. In this paper, the energy balance in the boundary layer of the vortex tube is analyzed with respect to a possible effect of temperature separation in the boundary layer by the viscous term of the enthalpy balance equation. A Large Eddy Simulation is used to generate the velocity profiles used for the computation of the viscous source terms. The dominant contributions of the source terms in the boundary layer of the vortex tube are identified and computed from the velocity fields. It is demonstrated how the strong velocity gradients in the boundary layer create a viscous flux of energy. An implementation of balance equations both with and without source term show the effect of energy separation in the boundary layer of the vortex tube.
Bicycle-drawn cargo trailers with an electric drive to enable the transportation of high cargo loads are used as part of the last-mile logistics. Depending on the load, the total mass of a trailer can vary between approx. 50 and 250 kg, potentially more than the mass of the towing bicycle. This can result in major changes in acceleration and braking behavior of the overall system. While existing systems are designed primarily to provide sufficient power, improvements are needed in the powertrain control system in terms of driver safety and comfort. Hence, we propose a novel prototype that allows measurement of the tensile force in the drawbar which can subsequently be used to design a superior control system. In this context, a sinusoidal force input from the cyclist to the trailer according to the cadence of the cyclist is observed. The novelty of this research is to analyze whether torque impulses of the cyclist can be reduced with the help of Model Predictive Control (MPC). In addition, the powertrain of the trailer is intended to support the braking process of the system with regenerative braking. In the context of this research, a first MPC controller design is carried out and analyzed with the help of a Hardware-in-the-Loop (HIL) approach where the microcontroller of the power electronics is included as hardware to ensure the vehicle dynamics control interacts properly with the lower-level field-oriented control. The battery and motor subsystems are simulated in a Typhoon HIL 604, which is supplemented by a vehicle dynamics model of the trailer that is integrated as a Functional Mock-Up Unit (FMU). First results indicate that the MPC longitudinal dynamics controller supports the driver during acceleration, attenuates the sinusoidal oscillations and reduces the force with which the trailer pushes the bicycle during braking.
In today's AI-driven era, computer vision, including autonomous driving, robotics, and healthcare, is prevalent. How-ever, acquiring ample data while managing resources and privacy constraints is challenging. This article proposes a solution: synthetic data generation. We use CAD software to craft intricate 3D models, process them in Blender, and evaluate quality using metrics like Structural Similarity and PSNR (Peak Signal to Noise Ratio). Synthetic data achieves up to 90% similarity with real data and an average PSNR of 21dB. Our method offers a streamlined, dependable ap-proach for enhancing computer vision, especially in object detection, addressing data acquisition challenges.
The power density of electric machines is a critical factor in various applications, i.e. like the power train. A major factor to improve the power density is boosting the electric current density, which increases the losses in the limited volume of the electric machine. This results in a need for an optimized thermal design and efficient cooling. The dissipation of heat can be achieved in a multitude of ways, ranging from air cooling to highly integrated cooling solutions. In this paper, this variety is shown and analyzed with a focus on water cooling. Further various structures in electric machines are presented.
A planar testbench is built to systematically analyze water cooling geometries. The focus lies in providing different power loss distributions along cooling channels, accurate temperature readings in a multitude of locations, as well as the pressure drop across the channel. The test bench results are aligned with simulations and simplified analytical evaluation to support the development process.
The main goal in this paper is to determine temperature gradients in the material close to the stator to quantize the potential for future cooling jacket designs. One question ,to answer is: How large the gradient is considering a realistic power loss distribution. Another sensible point are the different thermal expansions of aluminum used in cooling jackets and the steel core of the stator. This can be bypassed by using a steel cooling jacket. In this case, the performance of a steel cooling jacket compared to an aluminum version is investigated and also if light weight construction can compensate the lower thermal conductivity of steel.
After the analysis, an outlook about future changes of the measurement methods are given and first potentials for future cooling jackets are proposed.
Die Studie „Kulturen des Lehrens in der hochschulischen Erstausbildung von Hebammen in
Deutschland“ widmet sich der übergeordneten Frage, wie die Lehre in
Hebammenstudiengängen auf der institutionell-strukturellen und der personellen Ebene
gestaltet wird. Diese Frage wird im Rahmen einer qualitativ-rekonstruktiven Studie und über
eine between-method-triangulation bearbeitet. Dabei werden zwei Synopsen von
Strukturmerkmalen von Studiengängen (2019, 2021), eine Dokumentenanalyse der
Modulhandbücher (2019), Expert*innen-Interviews mit Studiengangsverantwortlichen (2019)
und berufsbiografisch-narrative Interviews mit Lehrenden durchgeführt (2019/2020).
Auf einer institutionell-strukturellen Ebene zeigen die Synopsen, die Dokumentenanalyse und
die Expert*innen-Interviews eine Studienlandschaft, welche sich im Hinblick auf verschiedene
Strukturmerkmale in einem Entwicklungsprozess befindet und personelle und zeitliche
Ressourcen erfordert. Anhand der dokumentarischen Interpretation der berufsbiografischnarrativ Interviews mit den Lehrenden in Hebammenstudiengängen lassen sich drei Lehrtypen rekonstruieren, welche sich in Bezug auf ihre habituellen Muster im berufsbiografischen Werdegang und der handlungsleitenden Orientierungen in Bezug auf die hochschulische Gestaltung von Lehre unterscheiden.
Die Studie beschreibt und rekonstruiert aus verschiedenen Perspektiven Kulturen des Lehrens
in der hochschulischen Erstausbildung von Hebammen und setzt einen Referenzpunkt für
weitere Entwicklungen. Die Ergebnisse betonen sowohl auf institutionell-struktureller Ebene
als auch auf der Ebene der Lehrenden die Relevanz personeller und zeitlicher Ressourcen für
die Implementierung einer kompetenzbasierten, wissenschaftsbasierten und
praxisintegrierenden hochschulischen Erstausbildung. Im Rahmen eines
professionstheoretischen Diskurses betonen die Ergebnisse die Bedeutsamkeit des
Strukturkerns hochschulischen Lehrhandelns für die Herausbildung eines professionellen,
wissenschaftsreflexiven Hochschullehrendenhabitus in Hebammenstudiengängen.
Ergänzend zu bestehenden Mobilitätskonzepten entwickeln sich derzeit neue Mikromobilitätskonzepte, die eine Beförderung von Lasten ermöglichen. Hier bieten elektrisch unterstützte Anhänger eine Option, in kommerzieller und privater Nutzung, Waren oder Lasten zu transportieren. Bereits verfügbare elektrisch unterstützte Anhänger benötigen eine Steuerungsverbindung zum Zugfahrzeug. In der vorliegenden Schrift wird als Alternative eine intelligente Zugdeichsel zur Steuerung des Anhängerantriebs ohne Steuerverbindung zum Zugfahrzeug vorgestellt. Dabei werden insbesondere die Sicherheitsaspekte genauer betrachtet.
Battery electric vehicle (BEV) adoption and complex powertrains
pose new challenges to automotive industries, requiring
comprehensive testing and validation strategies for reliability and
safety. Hardware-in-the-loop (HIL) based real-time simulation is
important, with cooperative simulation (co-simulation) being an
effective way to verify system functionality across domains. Fault
injection testing (FIT) is crucial for standards like ISO 26262.
This study proposes a HIL-based real-time co-simulation
environment that enables fault injection tests in BEVs to allow
evaluation of their effects on the safety of the vehicle. A Typhoon
HIL system is used in combination with the IPG CarMaker
environment. A four-wheel drive BEV model is built, considering
high-fidelity electrical models of the powertrain components
(inverter, electric machine, traction battery) and the battery
management system (BMS). Additionally, it enables validation of
driving dynamics, routes and environmental influences and provides
a precise analysis of the effect of powertrain system faults on driving
behavior. A possible case for a fault injection is to introduce a shootthrough fault in the inverter. Through the co-simulation, it is possible
to analyze the effects on the powertrain and the vehicle dynamics in
different driving situations (e.g. snow). This work demonstrates that
co-simulation is a valuable tool for the development and validation of
BEVs, and presents specific fault cases introduced into the
powertrain and the resulting effects tested under different driving
conditions. In addition, the study discusses the system's limitations
and future possibilities such as controller hardware integration
(Controller-HIL) and autonomous driving system validation.
Robotic grasping has been a prevailing problem ever since humans began creating robots to execute human-like tasks. The problems are usually due to the involvement of moving parts and sensors. Inaccuracy in sensor data usually leads
to unexpected results. Researchers have used a variety of sensors for improving manipulation tasks in robots.
This thesis focuses specifically on grasping unknown objects using mobile service robots. An approach using convolutional neural networks to generate grasp points
in a scene using RGBD sensor data is proposed. Two neural networks that perform grasp detection in a top down scenario are evaluated, enhanced and compared in
a more general scenario. Experiments are performed in a simulated environmentas well as the real world.
The results are used to understand how difference in
sensor data can affect grasping and enhancements are made to overcome these effects and to optimize the solution.
This thesis is an improvement on the works of Douglas Morrison, Peter Corke and Jürgen Leitner in their work Closing the Loop for Robotic Grasping: A Real-time,
Generative Grasp Synthesis Approach and Fu-Jen Chu, Ruinian Xu and Patricio A. Vela in their work Real-world Multi-object, Multi-grasp Detection.
Fahrdynamiksimulation von einem Fahrrad mit Anhänger zur Lastenbeförderung in der Mikromobilität
(2023)
Diese Arbeit befasst sich mit der Modellierung und Validierung eines Simulationsmodells in MATLAB/SIMULINK. Es wird untersucht, ob Simulationsergebnisse ähnlich wie in der PKW-Simulation auch für die Mikromobilität (hier Fahrrad plus Anhänger) genutzt werden können. Dafür wurde im Voraus ein Pacjeka Reifen Modell mit der Magic For-mula auf Basis eines Fahrradreifens erstellt. Das Simulationsmodell wurde mit Hilfe eines Anhänger-Prototypen und Realfahrtests validiert. Für die Validierung war es wichtig ein Fahrer-Regler in das System zu integrieren und für die Fahrtests auszulegen. Dieser Fah-rer ist für die Längs- und Querregelung verantwortlich und wurde mit Referenzkurven aus den Messdaten versorgt.
Die Auswertung zeigt eine große Übereinstimmung der Fahrdynamik-Messwerte bei dem hier benutzten Einspurmodell. Um möglichst eindeutige Messergebnisse für den Ver-gleich zu erhalten, muss der Einfluss des Fahrers bei den Testfahrten so klein wie möglich gehalten werden. Es ist möglich ein solches Simulationsmodell mit der Realität zu ver-gleichen und dieses für Fahrdynamik-Regelungen zu nutzen.
Distribution of Cooling Structures in Water Cooled Electrical Machines using Localized Loss Profiles
(2023)
Cooling is a critical factor for improving power density in electrical appliances, especially in integrated drives for mobile applications. However, the issue of distributed losses in electric machines can lead to hotspots and temperature gradients within the electric drive. Traditional cooling jackets use unidirectional flow without or with evenly distributed cooling structures. This often aggravates the issue of hotspots, resulting in thermal derating and thus limiting the operation range. As well, a non-demand oriented distribution of cooling structures leads to unnecessary pressure losses.
This problem is addressed with a newly elaborated method for distributing cooling elements, i.e., pin fins with varying density distribution inside the cooling channel. Results from previous work, numerical simulations, and measurement data from a planar test bench are used. The approach segments the cooling channel by using a loss profile. This profile and analytic heat transfer calculations are used to determine the required density of cooling elements for dissipating the locally induced losses. For a linear channel with uniformly distributed losses, this results in an increasing number of cooling elements within the channel in fluid flow direction. With localized losses, this will result in an increased density distribution in the respective areas. The method is evaluated by applying it to a planar test channel and investigating the temperature distribution on a test bench. First results indicate that the newly developed cooling element distribution provides an advantageous temperature distribution. The temperature gradient along the cooling channel shows a reduction from 23 K to 9 K with the distributed cooling elements.
The method, previously tested in the linear planar channel, then is applied to the construction of a cooling jacket with a specifically designed two-layer cooling channel. This design is analyzed using CFD, a prototype is currently under production. Tests on the prototype will follow in further investigations.