Urban Air Mobility Vehicle and Fleet-level Life-Cycle Assessment Using a System-of-Systems Approach

Can Urban Air Mobility (UAM) systems constitute viable and sustainable mobility solutions? This question has increasingly been concerning scientists, companies, policy makers, and authorities as more and more UAM vehicle concepts are seeing the light of day. In order to come closer to answering this question and to demonstrate the dependencies and impacts of the numerous parameters used to describe a highly complex system of a fleet of UAM vehicles operating in an urban environment, this paper employs a System of Systems (SoS) approach. A collaborative SoS framework with an agent-based simulation is introduced, which connects the UAM vehicle design, fleet performance, vertiport network, and re-energizing infrastructure with a Life-Cycle Assessment (LCA). The framework is used to simulate four exemplary UAM fleet-operation scenarios based on two cities and two operational modes, namely urban and suburban operations. Different vehicle design configurations, e.g. multirotor and lift + cruise vehicles, are evaluated in each scenario based on respectively realistic Concepts of Operations (CONOPS). Additionally, two different points in time, namely 2025 and 2050, are considered and assessed for powering the vehicles by taking into account the characteristics of batteries as well as the underlying electricity mix for their operation. Lithium nickel manganese cobalt oxide battery and lithium-sulfur (Li-S) batteries are considered. The SoS framework helps to asses various UAM metrics such as the average wait time for a passenger, the ideal number of aircraft needed for transporting all passengers within given time, the energy required on a vehicle and fleet level, sustainability metrics, e.g. the global warming potential associated with the energy carriers and many more. The capability to explore a wide design space and to visualize the dependencies between the system parameters and their impacts on different SoS metrics provides stakeholders with a helpful tool for their decision making

Towards Active Structural Psychoacoustic Control

Gegenstand der vorliegenden Dissertation ist die Reduktion der Schallabstrahlung schwingender Strukturen hinsichtlich psychoakustischer Größen mittels aktiver Maßnahmen. Psychoakustische Größen bieten eine bessere Darstellung der subjektiven Empfindung von Schall im Vergleich zu physikalischen Schallgrößen wie die Schallleistung. Die vorliegende Dissertation untersucht die Möglichkeit aktive Systeme, die auf eine Struktur applizierte Sensoren und Aktuatoren beinhalten, zu nutzen, um psychoakustische Größen gezielt zu beeinflussen. Insbesondere wird die Möglichkeit der Beeinflussung der psychoakustischen Lautheit durch eine geeignete Wahl der Platzierungen der Aktuatorik auf der zu beruhigenden Struktur untersucht. In numerischen sowie experimentellen Untersuchungen wird für eine ebene Platte eine aktive Steuerung ausgelegt und der Einfluss der Aktuatorplatzierungen auf das resultierende Schallfeld ausgewertet. Es wird nachgewiesen, dass die Erweiterung des aktiven Systems durch eine Aktuatorplatzierungsmethodik nach psychoakustischen Kriterien die gezielte Beeinflussung psychoakustischer Größen erlaubt

Using a psychoacoustic criterion for the actuator placement in an active structural acoustic control system

Active structural acoustic control (ASAC) systems for flexible structures with enclosed cavities are normally designed with the goal of minimizing the acoustic potential energy in the cavity. This goal is also taken into account during the search for an optimal actuator placement for the ASAC sys-tem. This paper is concerned with the change in the acoustic response of a structurally excited cavity when a psychoacoustic criterion is used for the placement of the actuators of the ASAC system instead. The placement of actuators on a flexible structure enclosed by a cavity is optimized using a genetic algorithm. Two optimization criteria are used: the acoustic potential energy in the cavity and the psychoacoustic loudness in the cavity. Numerical results regarding the acoustic potential energy reduction and the loudness reduction in the cavity of the coupled system in the case of an optimal feedforward control are presented for the two different actuator placement criteria

Numerische und experimentelle Untersuchungen zur Reduktion der Körperschalltransmission

The use of compounds and lightweight structures further emphasises the problem of sound transmission and radiation. Vibration, caused by the engine of an aircraft for instance, results in sound emission into the cabin. An new approach in noise reduction is taken by the use of structural intensity as a measure for the vibrational power per unit area. Using structural intensity instead of velocity as a cost function for control, the power flow is interrupted und there is a global attenuation of the downstream structure. This thesis gathers the necessary basis for the measurement and control of structural intensity using the example of a one-dimensional structure. The first part deals with different methods for measurement and calculation proposed in literature. These differ in the number of sensors used. By neglecting near field components of the vibration a reduction of the number of sensors is possible. Hence the error implied by this simplification is observed. Further limitations for the sensor spacing, as well as errors caused by displaced sensors, are calculated. Finally the methods using accelerometers are tested in an experiment. In the course of numerical investigations on the basis of a finite element model, it is shown that the simplified methods allow a qualitative analysis of the intensity. Especially in near field areas there is a significant error in intensity level. Only the full methods considering all field components are applicable for control. The methods using pure accelerometers or the corresponding method with combined accelerometers and angular rate sensors are capable of exactly calculating the structural intensity in near and far field areas. Due to the direct measurement of the angular rate, the method using combined sensors shows less errors caused by increasing sensor spacing or sensor displacement. Hence the control of structural intensity is based on these two methods. In order to use linear filters, the structural intensity is separated into its linear terms, being the basis for the calculation of the filter coefficients. Numerical analyses on a state space model show a tonal as well as a broadband attenuation of the energy flow and velocity. This barrier effect is observed globally downstream of the control. In comparison, a pure velocity control can only achieve global attenuation at resonance frequencies

Assessment of Three Commuter Aircraft Concepts from a Transport System Perspective

Over the last few years the environmental impact of transport in general and aviation specifically has increasingly gained attention. In this context recent developments focus on new technologies for more sustainable aviation. This paper focuses on the assessment of three novel electric commuter aircraft concepts by comparing them not only with existing aircraft with similar top-level requirements, but also with other modes of transport. By choosing a solution-neutral statement of the problem (here regional travel) and taking into account aspects such as inter-modal door-to-door travel, environmental impact, and noise emissions, a holistic assessment of the proposed aircraft concepts is intended. The evaluation of the aircraft concepts is conducted by considering the proposed aircraft designs as part of a more comprehensive transport system. This transport system includes other modes of transport that may be used for the range in which the proposed aircraft can be operated (e.g. car, train). It also considers the door-to-door travel time by taking into account the available infrastructure. Different modules are used to evaluate the vehicles when used on individual connections (traveling from origin A to destination B) in terms of time, cost, and overall passenger’s choice preference. The model used to describe the choice behavior of the passengers does not only include door-to-door time and travel costs, but also soft factors like e.g. environmental awareness. Taking the example of Germany’s transport system as a use-case scenario, an assessment of the aircraft concepts on a transport system level is attempted. The developed methodology is applied to compare partial aspects of the proposed concepts such as environmental impact, as well as to estimate overall metrics, such as the potential market share of the concepts in the transport sector. Furthermore the impact of possible future scenarios, e.g. the availability of a larger number of airports or the introduction of a tax on emissions, on the overall performance of the proposed concepts is investigated from a transport system point of view

A study on the relation between the actuator placement and the characteristics of the sound radiated by a plate structure

One of the parameters influencing the performance of active control systems for the reduction of vibration or noise is the placement of the active components of the system (actuators) on the host structure. In active vibration control systems the actuators are normally placed following a criterion related to the kinetic energy on the structure, whereas in active noise reduction systems they are placed taking into account a sound pressure related metric. This numerical study investigates the placement of point force actuators on a generic plate structure within an active structural acoustic control system. Two setups are tested: a plate radiating in free field, and a plate radiating into a rectangular cavity. In both setups the plate is excited in its first natural frequencies by an incident diffuse sound field. The optimal placements of the actuators on the plate determined for a minimal sound power radiated in free field or a minimal acoustic potential energy radiated into the cavity are compared to the optimal actuator placements determined for a minimal mean loudness over the area of interest. The effect of the different actuator placements on the ttenuation of the dominant radiation modes is analysed. The possible benefits of using the psychoacoustic loudness as an actuator placement criterion are discussed

Power and Biomass to Liquid - An option for Europe’s sustainable and independent aviation fuel production

To answer the question, if Europe can self-sufficiently cover its sustainable fuel (SAF) demand with the PBtL path, three key issues have to be addressed: The availability of sufficient biomass resources in Europe has to be assessed. Second, a techno-economic analysis uncovers fuel production costs for different economic boundary conditions, i.e. national grid electricity cost or biomass prices, to ensure the economical provision of SAF. Third, whether the fuel can be regarded as sustainable according to the EU’s RED II is determined by the production path’s global warming potential (GWP), which strongly depends on the used electricity GWP. To that end, a GWP assessment based on local production conditions is conducted and the production capacity for SAF determined. A discussion of different electricity sources on a regional level not only shows possible sweet spots for the role-out of the PBtL technology but also reveals Europe’s potential SAF production capacity and cost. Advantages of the PBtL process in terms of CO2 abatement and production capacity over other biomass paths will be highlighted. Finally, the possible role for PBtL in Europe’s move towards sustainable aviation fuel production will be discussed

Lärmreduktion in Flugzeugen mit aktiven Linings

Das DLR erforscht im Verbund mit dem Industriepartner Diehl Aircabin die Möglichkeiten zur Lärmreduktion in Flugzeugen mit Hilfe von aktiven Seitenwandverkleidungsteilen (Linings). Neuartige Antriebe in Kombination mit leichten und hochsteifen Rumpfstrukturen können die Transmission insbesondere von niederfrequentem Schall in die Kabine begünstigen. Linings stellen als große schallabstrahlende Flächen einen wichtigen Transmissionspfad dar. Es wird daher versucht, die Schallabstrahlung von Linings durch adaptronische Maßnahmen zu beeinflussen und die in die Kabine eingetragene Schallleistung zu reduzieren. Dieser Beitrag soll einen Einblick in die Erforschung aktiver Linings am DLR geben und auf wichtige Ergebnisse eingehen. Zur Durchführung von Experimenten wurde eine Rumpfstruktur aus kohlenstofffaserverstärktem Kunststoff (CFK) gefertigt und in die Prüföffnung eines Transmissionsprüfstands eingebaut. An dieser Rumpfstruktur ist das Lining gelagert. Das System wird seitens der Rumpfstruktur mit einem Lautsprecherfeld akustisch angeregt. Die Realitätsnähe des Versuchsaufbaus erlaubt belastbare Aussagen über die Wirksamkeit passiver und aktiver Akustikmaßnahmen. Die Messergebnisse zeigen, dass mit nur wenig Aktuatorik erhebliche Reduktionen der abgestrahlten Schalleistung und der Schalldruckpegel im Passagierbereich vor dem Lining zu erreichen sind. Durch Zusatzfunktionen wie Passenger Announcement (PA) könnten klassische Lautsprechersysteme ersetzt und Masse eingespart werden