Funding
The following list gives an overview of research projects with participation of the Chair of Flight Mechanics and Flight Control.
Current:
Duration: 2024-2025
Funding Agency: ESA
Contact: Frederik Thiele
The ever-growing ambition of space missions drives upwards the spacecraft complexity, leading to com-posite assemblies whose dynamic behaviour may not be predicted with the required degree of certainty during design and in-orbit offline assessments, using traditional estimation techniques. Real-time sys-tem identification (SysID) methods are expected to significantly benefit the Attitude and Orbit Control System (AOCS) design in these cases to reach the desired performance.
Duration: 2024-2025
Funding: BMDV
Contact: Sebastian Schubert
As the development of UAS systems progresses, further large-scale areas of application will arise in the future, such as wind damage analysis on transport infrastructure or the delivery of parcels. For large-scale implementation, such as flying over a kilometer-long railroad line with suspected hurricane damage, range plays a major role. With battery-powered UAS, this is mainly limited by the weight of the battery. This project is intended to help find a particularly energy-efficient route along the task route based on a wide range of available data in order to extend the range, enable longer flights for a longer observation period and ultimately operate the systems more sustainably.
Increasing the efficiency of UAS by reducing the necessary energy consumption is to be achieved by utilizing the wind field during mission flights along traffic infrastructure. The aim of the project is therefore to obtain flight test data from the sensors integrated in the overall system for wind field measurement in relation to forecast and weather station data.
For this purpose, a demonstration system for wind field determination based on established sensors that can be integrated on a UAS is being set up as part of the project. In parallel, we are developing a data pipeline to derive high-resolution wind fields from on-board wind measurements of UAS and from coarse-resolution forecasts of regional weather models in order to put the data in relation to each other. Finally, the wind field measurement system will be demonstrated on a representative flight route to illustrate the potential savings in energy consumption of the autonomous UAS.
Duration: 2024 - 2027
Funding Agency: EU
Contact: Felix Biertümpfel
REDECORATE proposes CubeSat swarms as a cost-effective way to mitigate space debris. It develops a debris deorbiting and recommissioning concept for decommissioned satellites. The concept combines novel control and guidance approaches with a CubeSat swarm using ionic electro spray engines (iESE).
In principle, a CubeSat swarm can rendezvous with space debris, dissipate its rotational energy (detumble) using, for example, its reaction wheels. The CubeSats’ main thrusters then lower the debris orbit to burn-up the system in the atmosphere. Such a mission is highly challenging, requires coordinated CubeSat swarm guidance and control, reliable hardware and effective propulsion - a combination which does not exist so far. REDECORATE addresses three crucial problems of such a mission.
First, iESE thrusters are proposed to overcome the limitations of current CubeSat propulsion and attitude control. Electrospray engines are passively fed, compact, fuel-efficient, and can be used for both main propulsion, and attitude and position control. Due to their small form factor, multiple stages of iESE can be installed on a CubeSat and then be sequentially used. Staging achieves longer missions, higher reliability, and thrust than standard CubeSat propulsion. Moreover, iESEs are completely throttleable and jitter-free. Hence, using electrospray thrusters for attitude and position control facilitates new levels of CubeSat control performance. If the CubeSats are attached around a decommissioned satellite, coordinated activation of the iESEs can function as a new control system for detumbling (avoiding unreliable reaction wheels) and deorbiting. Due to their long life-time, the swarm can also be used to recommission the satellite if, e.g., a failure in the satellites flight control system, caused a premature end of its mission. Second, a safe-by-design hierarchical control framework will be developed to address the need for high reliability. It uses a planner-tracker feedback stack and addresses all mission segments. Third, integral quadratic constraints (IQCs) will be used to increase robustness w.r.t. system uncertainties and communication delays inside the swarm. The feasibility of the control concept will be validated using IQC-based and probabilistic robustness analyses on a digital twin of the iESE CubeSat swarm and microcontrollers-in-the-loop.
Duration: 2024-2027
Funding Agency: ESA
Contact: Carl-Johann Winkler
Planning and control problems are becoming ever more challenging due to the increased complexity of modern space missions (e.g., re-usable launchers and celestial hopping systems). Classical model-based control methods are reaching a point where they will no longer be able to fulfil performance requirements for such complex systems, thus compromising mission safety and success. To maintain system-level simplicity without sacrificing performance, guidance, navigation and control (GNC) systems must be more versatile and adaptable to the many tasks and system configurations.
Adaptability, and thus improved safety, can be achieved by online optimization. Model-free/learning-based approaches remove the necessity of complex, task-specific, high-fidelity models, thus making them more versatile to different use-cases. This project focuses on applying a model-free, online optimisation control algorithm (e.g., learning) to spacecraft landing scenarios. In order to guarantee robustness in the resulting controllers, the algorithm will utilise perception-based control to learn the system states from live image data then subsequently optimise the controller gains with certain robustness and performance bounds.
To test the model-free, vision-based GNC approaches online in a realistic-setup, they will be implemented on a multi-copter test-bed. The multi-copter can accurately simulate various space systems in different environments. Modularly removable flexible pendulums, tanks and masses, incorporate varying dynamics (sloshing, flexibility, instability, etc.). Direct thrust control simulates different gravitational fields as well as thrust vectoring control of the vehicle. And, modular sensors provide the visual input to the GNC algorithms. Overall, the work will provide valuable insight into using model-free approaches on autonomous space systems, simulated on a demonstrator more versatile than those developed for NASA.
Duration: 2023-2027
Funding Agency: EIC
Contact: Harald Pfifer
This project aims to bring ionic air-breathing propulsive systems beyond the pioneeristic phase, exploring their capabilities and improving their performance. Non-thermal plasma for atmospheric propulsion is a subject of recent investigations: model airplanes and vertical lifters have recently flown with this type of propulsion, but the potential of this technology is much higher. Many open aspects in this field deserve to be investigated, from fundamental research on ion production to geometric optimization of electrodes and integration of propulsion systems in existing aircrafts.
Duration: 2023-2024
Funding Agency: ESA
Contact: Carl Winkler
The New-Space developments with the emergence of microlaunchers face new challenges to be competitive against the ride-share offers of larger launcher systems. A mission configuration campaign that takes several months, with the GNC being one of the main drivers, does not meet the requirements. Therefore, a departure from the classical approach to the GNC design and V&V is unavoidable to reduce the time and recurrent cost for each mission. Robust control techniques offer great opportunities to design and validate controllers in a faster and more reliable way but require the right set of tools and/or expert level knowledge. The main objective of the project is to develop a Control Design Framework to provide a foundation to develop and validate robust controllers that paves the way for industrialization in the New-Space market.
Duration: 2023-2026
Funding Agency: ESA
Contact: Emily Burgin
Future space missions become more demanding as lunar gate ways and manned mars landing are introduced. Due to increased system complexity and need for autonomy, classic methods for navigation, guidance, and control are not sufficient for safe operation. Moreover, spacecraft no longer have a single configuration. They interact with one another, change configuration multiple times along their missions and have varying dynamics due to propellant burn and changing environmental conditions.
The project develops an artificial intelligence (AI) enhanced real-time system identification and LFT generation methods. Therefore, novel online identification techniques will be deployed to quantify uncertainties. Through AI the system identification process is coupled to a low order LFT generation covering uncertainties and varying dynamics. Then, the control law is updated in real-time based on current system dynamics and configurations. The applicability will be shown on a rapidly reconfigurable system. Hence, the work provides a holistic AI enhanced identification, modelling and synthesis framework.
Duration: 2022-2025
Funding Agency: DLR
Contact: Frederik Thiele
The primary goal of the project "ARCTIS" is to diminish noise and thus improve rotor efficiency and reduce environmental impact and pollution. This shall be achieved by investigating curvature changes of shape-adaptive rotor blades. A highly accurate mapping of the dynamics of such rotor blades and their influence on noise emission forms the theoretical basis for the creation of aero-acoustic models. Control laws are to be derived by means of modern periodic control techniques to reduce noise. Potentially suitable sensors are investigated in order to enable the measurement of the necessary quantities during flight and to guarantee the applicability of the research.
Duration: 2022-2024
Funding Agency: ESA
Contact: Emily Burgin
Over the course of their operational life, spacecraft undergo changes on various levels with significant implications on the attitude and orbit control system (AOCS). Examples include deployment and rotational movement of appendages such as solar arrays or instruments (e.g. the Scatterometer of MetOp-SG), which directly affect the dynamic behaviour by changing the spacecraft’s mass properties and structural mode frequencies. State-of-the-art solutions relying on robust linear time-invariant techniques are able to solve these technical challenges, albeit with suboptimal performance and potentially unnecessary design iterations and re-tunings. An attractive option for improvement is to employ linear parameter-varying (LPV) techniques. The objective of the project is demonstrating the feasibility of applying LPV and adaptable control techniques to real-life spacecraft attitude control problems caused by one or several variable parameters and evaluating where the advanced techniques improve upon existing solutions in terms of technical performance as well as development effort.
Duration: 2022-2024
Funding Agency: DLR
Contact: Hannes Rienecker
The main objective of the URBANSens project is to optimise flight routes in urban areas for energy efficiency according to weather conditions. In particular, the wind conditions along the flight route have a considerable influence on the energy expenditure. In order to obtain even more detailed data, sensors on the aircraft will record the wind and weather conditions both in advance and around the aircraft. This weather information will then be shared with the other aircraft, so that a comprehensive picture of wind conditions is created by networking and analysing the data. As an example application, a delivery logistics system will be developed based on networked unmanned aerial systems (UAS) equipped with novel measurement technology. Due to their small size and weight, UAS are strongly influenced by local environmental aerodynamics in urban areas.
Past:
Duration: 2023
Funding Agency: ESA
Contact: Harald Pfifer
There is a steady increase of cost pressure in industry despite a steady increase of satellite system complexity. This bears the risk of cost explosion in future missions if not counteracted early enough. The study proposed here is an essential step to counteract this risky trend by increasing the industrial efficiency. Verification & Validation (V&V) activities constitute approximately 30-60% of the overall Attitude and Orbit Control System (AOCS) cost. This large proportion justifies "V&V" as being the focus of this study. The study aims at reducing the gap between the V&V technology available at research institutes and the V&V technology established in industry.
Duration: 2021-2023
Funding Agency: Industrial Research funded by Voith Hydro
Contact: David Noelle
The design of the air circuit for cooling hydropower generators is largely carried out using CFD simulations and network calculations. However, for innovative designs, which sometimes deviate strongly from the previously established ones, direct measurements of the pressure loss characteristics are still required to validate the calculations. Scaled models of the original machines are used for this purpose.
The scaling of the generators into the model is not simply done by applying a scaled reduction, but according to principles of fluid mechanical similarity as well as empirical values. This results in quite different scaling factors for individual elements of the geometry and in the spatial directions. Only partial similarity can be achieved, which is why the approaches used always represent compromises between different criteria. There is a lack of specialist literature as a reliable guideline or for checking the selected scaling approaches. Also, the amount of publications in this field is very limited.
Therefore, the aim of this project is to create a broad data basis and, based on this, to develop guidelines for the scaling of hydropower generator models. For this purpose, basic theoretical, numerical and experimental considerations are carried out.
Duration: 2021-2023
Funding Agency: ESA
Contact: Felix Biertuempfel
Future space missions become increasingly challenging following the introduction of re-usable launchers and concepts of manned mars landing. Due to the increasing system complexity and autonomy, classical methods for planning, guidance, and control are no longer adequate to assure mission safety and success. Re-usable launcher and landing systems have rapidly varying dynamics due to the high fuel fraction, rapid fuel-burn, and changing environmental conditions. This must be explicitly considered by the control and planning strategies. The state-of-the-art approach is heading towards onboard, online optimization to meet the performance and autonomy requirements. However, standard real-time embedded optimization methods need convergence guarantees when dealing with nonlinear dynamics under uncertainties. The project aims at developing analytical V&V tools to explicitly meet the requirements for uncertain nonlinear systems under safety constraints over finite time and control horizons. The existence and fixed-point convergence will be guaranteed using the integral quadratic constraints (IQC) framework.
Bodeneffekt
Start und Landung stellen die kritischsten Flugphasen in der Luftfahrt dar. Kurz vor dem Aufsetzen bzw. kurz nach dem Abheben wirkt außerdem der Boden auf die Flugzeugumströmung zurück und verändert so dessen aerodynamische Eigenschaften. Windkanalmessungen im Bodeneffekt sind deshalb fester Bestandteil bei der Entwicklung von Großflugzeugen. Bei solchen Versuchen werden ebenso wie im Fahrzeugbau mitlaufende Bänder zur korrekten Modellierung der Bodenrandbedingung verwendet.
Prinzipuntersuchungen mit einem stark angestellten Spaltflügel in Rückenlage zur Überprüfung des stabilen Bandlaufes unter Saugspitzen mit einem touchierenden Laserstrahl
Im Rahmen von M-Fly/Aeronext geförderte umfangreiche Untersuchungen zu Bodeneffektmessungen an Transportflugzeugen dienen einer grundlegenden Klärung von Problemen, die im Versuchsbetrieb in größeren Kanälen wie dem DNW-LLF auftreten. Dazu zählen Unterdruckgebiete, die infolge der Interaktion von Klappenrandwirbeln und Propellerstrahlen auf dem Boden entstehen und zu einem Abheben des Gurtbandes führen können. Außerdem ist eine Überprüfung der Eignung moderner Elektromotoren aus dem Flugmodellbau für Windkanalmessungen Bestandteil des Projektes. Die Leitung starker, nicht völlig geglätteter Ströme an der Messwaage vorbei wirft Fragen bezüglich elektromagnetischer Verträglichkeit und Kabelsteifigkeit auf, die es zumindest auszuräumen gilt.
Die gewählte eher ungewöhnliche asymmetrische Modellkonfiguration erlaubt die Behandlung aller geforderten Aufgaben bei einem günstigen Modellmaßstab. Die Halterung durch den Flügelstummel ermöglicht zudem den Verzicht auf Anbauten am Rumpf, die so in der Realität nicht vorhanden sind und z.B. das Seitenleitwerk abschatten. Für die Messungen ist eine spezielle Fünfkomponentenwaage angefertigt worden, deren Messwerke sich wie Kettenglieder umschlingen und die damit quer im Rumpf des Modells Platz findet.
TAMGIV
Im Ergebnis konnten u.a. das Auftreffen des Randwirbels auf das Band und ein auftriebsmindernder Rückstau vom Boden bis auf die innere Spaltklappe identifiziert werden.
Strömungsbeeinflussung an Hochauftriebskonfigurationen
Die Arbeiten zurAusftriebssteuerung durch Absaugung an der Flügelhinterkante mündeten in einem im Rahmen des Luftfahrtforschungsprogramms LuFo IV (M-Fly/Aetronext) geförderten Projekt, bei dem die Beeinflussung der Strömung auf dem transsonischen Profil DLR F-15 in Hochauftriebskonfiguration untersucht wird. Ziel ist es, die Wirkung eines als Wölbklappe absenkbaren Spoilers durch Ausblasung am Scharnier und Absaugung an der Hinterkante zu verbessern und in der Folge den Ausschlag der Spaltklappe vergrößern zu können, was im Endziel zu einer Steigerung des Gesamtauftriebs führt. Im Umkehrschluss soll es mit solchen Technologien möglich sein, auf komplizierte, schwere und geräuschintensive Mehrfachspaltklappen zu verzichten.
Ursprünglicher Aufbau senkrecht in der Messstrecke, Blick ins Modellinnere
Späterer, waagerechter Aufbau; Arrays mit paarweisen Heißfilmen zur Ablösungsdetektion auf der Klappe
Neben dem Nachweis der Möglichkeit der Auftriebssteigerung durch Absaugung auch an der Hinterkante des abgesenkten Spoilers wurde in einer letzten Projektphase in Zusammenarbeit mit Partnern aus Ottobrunn die Möglichkeit untersucht, einsetzende Ablösungen auf der Klappe anhand von paarweise angeordneten Heißfilmen zu detektieren, da diese den Richtungssinn der wandnahen Strömung erkennen können sollten.
„Skalenübergreifende Modellierung in der Strömungsmechanik und Meteorologie“
Anwendungsbereich : Große Skalen der Turbulenz
Forschungsvorhaben:
„Turbulente Austauschprozesse zwischen Waldflächen und der Atmosphäre“
In Landschaften stellen Wälder in thermischer und dynamischer Hinsicht die wichtigsten Inhomogenitäten dar. Ihre vertikale Ausdehnung und ihre komplexe Struktur führt zu zahlreichen Effekten, die bis heute noch völlig unzureichend beschrieben werden können, z.B. Rezirkulationen mit elastischen Rauigkeitselementen, zeitlicher Wechsel zwischen ge- und entkoppelten Bestandsräumen oder transienten, internen Grenzschichten ohne vollständige Anpassung an die Unterlage. Diesem Manko soll durch eine Kombination von Strömungsexperimenten und Modellsimulationen abgeholfen werden. Dabei arbeiten die beiden beteiligten Institute der TU Dresden sowohl experimentell als auch numerisch eng zusammen und stimmen ihre Vorgehensweisen hinsichtlich der jeweiligen dynamischen Randbedingungen so ab, dass in jedem Teilprojekt die meteorologischen und strömungsmechanischen Belange vertreten sind. Von besonderer Bedeutung in den beiden Teilprojekten ist der anwendungsorientierte Aspekt der Ausbreitung von Spurenstoffen, also CO2 sowie Schadstoffen, im Bereich des Waldes und seinen Rändern.
Poster zum DFG-Schwerpunktprogramm 1276, Teilprojekt C4
„Bildgebende Messverfahren für die Strömungsanalyse“
Thema:
„3-D PTV zur quantitativen Bestimmung Lagrange’scher Partikeltrajektorien in Gasströmungen"
3-D PTV (particle tracking velocimetry) ist ein photogrammetrisches Messverfahren der Strömungsanalyse, welches es erlaubt, für eine große Anzahl von unregelmäßig über ein dreidimensionales Beobachtungsvolumen verteilten Partikeln alle drei Komponenten des Geschwindigkeitsvektors zu bestimmen. Zusätzlich ist 3-D PTV in der Lage, Partikel über längere Zeit zu verfolgen und damit dreidimensionale Trajektorien als Voraussetzung für eine Lagrange'sche Betrachtung zu generieren.
Berechnete Partikelbahnen
Das Verfahren wurde bislang ausschließlich für die Analyse von Phänomenen in Flüssigkeiten eingesetzt. Im Rahmen des Forschungsvorhabens soll ein Verfahren entwickelt werden, das erstmals die Bestimmung von 3-D Trajektorien in Gasströmungen ermöglicht. Dazu wird eine digitale Hochgeschwindigkeitskamera mittels eines Prismenvorsatzes zu einem Aufnahmesystem erweitert, welches mit hoher zeitlicher Auflösung stereoskopische Bildsequenzen von durch geeignete Partikel visualisierten Strömungen aufnimmt. In diesen Bildsequenzen werden durch Methoden der digitalen Bildverarbeitung Partikel detektiert, aus denen durch Herstellung der spatio-temporalen Korrespondenzen dreidimensionale Trajektorien bestimmt werden.
Optischer Aufbau mit Strahlteiler
Das System wird zur quantitativen Untersuchung von Ablösungserscheinungen hinter stumpfen Körpern im Windkanal angewandt. Damit können auch instationäre Vorgänge dreidimensional mit hoher räumlicher und zeitlicher Auflösung analysiert und mit numerischen Simulationen sowie Resultaten anderer Messverfahren verglichen und grundlegende Erkenntnisse über die Bildung von Wirbelstrukturen bei umströmten Körpern erhalten werden.
Vergleichsmessungen zur mittleren Geschwindigkeit der Zylinderumströmung mit Hitzdraht
Vergleichsmessungen zur mittleren Strömungsgeschwindigkeit mit Hitzdraht
Vergleichsmessungen zur Aufenthaltswahrscheinlichkeit der Partikel anhand der Ausbreitung einer CH4-Fahne.