| 1. |
- Raduenz, Henrique, 1990-
(författare)
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On Machine Learning-Based Control for Energy Management in Construction Machines
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High energy efficiency is a key requirement for modern construction machinery. This is because of stricter environmental targets, electrification, and reduction of operation costs. To meet this requirement, the powertrain architectures of the machines are becoming increasingly complex, for example through hybridisation of drivetrain and work functions, or with improved hydraulic systems. However, the more complex the architecture is, the harder the management of splitting power between different sources and consumers. The number of work functions, operating environments, and tasks these machines engage in, along with the added degrees of freedom with respect to how energy can be recovered, ex-changed, and reused, makes them unique. Therefore, the development of control strategies for energy management in such machines requires specific research and development with their architecture and application in focus. This doctoral thesis presents an analysis of two methods for the development of machine learning-based energy management strategies for construction machines. One is based on supervised learning and the other on reinforcement learning. The methods use optimisation to find optimised solutions for the control problem of the systems and machine learning for learning and implementing the control decisions. In both methods, models of the physical systems are used for the learning and training. The thesis highlights and confirms, with experimental results, the potential of such methods to derive control strategies for these machines. The studied methods can learn and implement improved control decisions in the real systems that result in the potential for increased efficiency. At the same time, their robustness is shown in the application to unseen scenarios during training, although that does not eliminate the need for further training in the real systems after deployment. The thesis also increases the comprehensiveness on energy management for construction machines. The thesis was completed in a double-degree format between the Federal University of Santa Catarina, Florianópolis, Brazil, and Linköping University, Linköping, Sweden.
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| 2. |
- Knöös Franzén, Ludvig, 1990-
(författare)
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An Ontological and Reasoning Approach to System of Systems
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- System-of-Systems (SoS) are all around us and are becoming more common in today’s highly interconnected world. Systems are connected with other systems and have strong dependencies with their operational environments. This leads to an increased level of complexity and risk during product development. A holistic view, and an SoS perspective, is consequently needed in order to develop an early understanding of the available design spaces for new system solutions. This thesis suggests a method that has been developed for this purpose, and to meet the demand for a more holistic product development. Overall, the method consists of two correlated approaches that show how a design space for SoSs can be generated and later processed with, for example, design space reductions. Search and Rescue (SAR) operations have been used as examples of typical SoSs throughout this work and in the development of the presented method. An architecture framework has been used to introduce a standardized and consistent way of understanding the relationships that exist between needs, capabilities and functions. This approach can consequently be used to generate a design space of functions to be performed to meet the overarching needs of an SoS. The second approach has been based on ontology and description logic reasoning. Ontology has here been used to represent an SoS design space with, for example, available SAR assets and their relationships with the operational environment. An SoS representation in an ontology model introduces additional expressiveness and the design space processing capabilities needed for a holistic design process and product development. Based on these results, this thesis and its suggested method and approaches contribute to holistic product development from an SoS perspective.
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| 3. |
- Kärnell, Samuel, 1993-
(författare)
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On Electrified Fluid Power Systems in Mobile Machinery
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High power density in combination with flexible power distribution possibilities and extreme robustness are reasons why fluid power has been the preferred technology in mobile machinery, such as excavators and cranes, since the mid-20th century. In principle, the machines have been powered by a combustion engine which powers a pump, with the output from the pump being distributed to different functions via valves. However, a transformation is currently underway. Combustion engines are being replaced by electric motors, and batteries able to store energy corresponding to several hours of operation are often desired. Since batteries tend to be heavy and expensive, reducing the energy consumption is getting higher priority than ever before. There are applications where electrification means that hydraulic components are replaced by electric counterparts, but fluid power has characteristics that are highly desirable in mobile machinery. Therefore, many hydraulic actuators will remain. Conventional hydraulic systems, which are known for their inefficiency, should, however, be adapted to the new conditions brought about by electrification. The question, and the overall subject of this thesis, is: how? The research has focused on two main topics: pump-controlled systems, which are systems where each actuator has its own supply unit, and the use of variable displacement pumps in electrified systems.A large proportion of the losses in many conventional hydraulic systems is due to the simultaneous operation of functions that require different pressure levels. One way to avoid these losses is to use pump-controlled systems. How these systems should be designed is, however, far from obvious. In this thesis, different types of pump-controlled systems are compared, both statically and dynamically.Regarding variable displacement pumps, they have had a natural place in many conventional systems, but electrification may change this, since speed-control can now also be used for flow- and pressure control. However, there are still aspects relating to energy consumption and component dimensioning, among other things, that makes variable pumps relevant. These aspects are investigated here, and different types of variable pumps are reviewed.
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| 4. |
- Hällqvist, Robert, 1983-
(författare)
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On the Realization of Credible Simulations in Aircraft Development : Efficient and Independent Validation Enabled by Automation
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Designing modern aircraft is not an easy task. Today, it is not enough to optimize aircraft subsystems at a subsystem level. Instead, a holistic approach is necessary whereby the constituent subsystems need to be designed for the best joint performance. The State-of-the-Art (SotA) in simulating and ex-changing simulation models is moving forward at a fast pace. As such, the feasible use of simulation models has increased and additional benefits can be exploited, such as analyzing coupled subsystems in simulators. Furthermore, if aircraft subsystem simulation models are to be utilized to their fullest extent, open-source tooling and the use of open standards, interoperability between domain specific modeling tools, alongside efficient and automated processes for model Verification and Validation (V&V) and credibility assessment are required.The financial and safety related risks associated with aircraft development and operation require well founded design and operational decisions. If those decisions are to be founded upon information provided by models and simulators, then the credibility of that information needs to be assessed and communicated. Today, the large number of sensors available in modern aircraft enable model validation and credibility assessment on a different scale than what has been possible up to this point. This thesis aims to identify and address challenges to allow for automated, independent, and objective methods of integrating subsystem models into simulators while assessing and conveying the constituent models aggregated credibility.The results of the work include a proposed method for presenting the individual models’ aggregated credibility in a simulator. As the communicated credibility of simulators here relies on the credibility of each included model, the assembly procedure itself cannot introduce unknown discrepancies with respect to the System of Interest (SoI). Available methods for the management, distribution, and accurate simulation of coupled models are therefore exploited and tailored to the applications of aircraft development under consideration. Finally, a framework for automated model validation is outlined and established that supports both on-line and on-line simulator credibility assessment.
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| 5. |
- Knöös Franzén, Ludvig, 1990-
(författare)
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A System of Systems View in Early Product Development : An Ontology-Based Approach
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The concept of system-of-systems is becoming increasingly common and relevant in many engineering applications. Today’s highly interconnected world entails that more and more systems have dependencies on other systems. This increasing number of interdependencies results in new levels of complexity that must be managed in the early development of new products. Different viewpoints must also be handled to understand the many layers of a system-of-systems and its surrounding context. An ever-changing future results in uncertainty about the operational environment but also other aspects, such as available technologies, which complicates the matter even further. Traditional approaches for early product development can be used to some extent, but the complexity, scale and sheer number of interconnections in system-of-systems require a holistic perspective to obtain an early understanding of the problem, design spaces, and multiple aspects involved. This dissertation aims to present a method that has been developed to address the demand for a more holistic system-of-systems view in early product development. Overall, the method consists of four parts that together show how design spaces for system-of-systems can be generated and later processed to find suitable solutions. Search and rescue operations have been used as examples of system-of-systems throughout this work and in the development of the presented method. The first two parts of the method are based on architecture frameworks and ontologies with description logic reasoning capabilities. An architecture framework is here used to break down system-of-system needs into functions to be fulfilled by constituent systems. Ontologies are thereafter used to represent the outcome and the resulting system-of-system design spaces with involved entities and their relationships. Description logic reasoning can subsequently be used to process the available design spaces and suggest suitable system-of-system solutions. The last two parts of the method build upon a concept exploration and estimation approach, together with visual analytics. The approach illustrates how individual system concepts can be estimated from an ontology-represented design space, and how visual analytics can be used to explore different system-of-system viewpoints at an early stage. Based on the outcomes of the presented method, this dissertation contributes a holistic take on early product development from a system-of-systems perspective.
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| 6. |
- Schön, Sofia, 1993-
(författare)
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Model Fidelity in Mission Scenario Simulations for Systems of Systems : A Case Study of Maritime Search and Rescue
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Systems of Systems (SoS) represent a view where individual, independent systems named Constituent System (CS) collaborate to achieve overarching capabilities not attainable by a single CS alone. In cyberphysical systems, CS can be engineered entities like boats or aircraft, when they collaborate in an environment it can be viewed as an SoS. There is a large interest in modeling and simulation of phenomena present at different scales of SoS, which requires choosing appropriate model fidelity and resolution for the study. This thesis delves into the intricacies of modeling and simulation of mission scenarios within SoS, with a keen focus on engineered CS operating in physical environments. At the heart of the thesis lies the concept of model fidelity, examined through philosophical, scientific, and engineering perspectives.A maritime search and rescue scenario by airborne search assets serves as case study, using Agent Based Simulation (ABS) to explore the Measures of Effectiveness (MoE) of the mission. Through a hierarchical viewpoint it is studied how the model fidelity on Sub-System (SS) level affects its performance and how it aggregates up to performance on the CS level and at last the MoE on SoS level. In the scenarios, manned assets utilize traditional search patterns that is used in present search and rescue operations. Concurrently, autonomous assets employ a belief map search strategy where the map is based on probability density functions underpinned by a Bayesian modeling approach to new observations as the search progresses.The study shows that increasing the model fidelity at the SS level, particularly by refining the representation of the search sensor, can impact the MoE of the mission at the SoS level. However, this influence shows to be notably scenario-dependent, emphasizing the intricate relationship between model fidelity and system performance. The findings indicate that the relevance of model fidelity is tied to how measures of performance at lower levels aggregate to influence overarching mission outcomes. The thesis concludes by discussing validation and verification of the case study and ties encountered modeling difficulties to resolution and model fidelity aspects. Future work is suggested to be a deeper dive into mission engineering, where the mission itself is viewed as the system of interest, and how it could be combined with modeling and simulation in product development.
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| 7. |
- Sobrón Rueda, Alejandro, 1990-
(författare)
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On subscale flight testing : Cost-effective techniques for research and development
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Experiments with downscaled or subscale physical models have traditionally been an essential source of information in aerospace research and development. Physical models are very effective at revealing unforeseen issues and providing confidence in design predictions or hypotheses. While computational methods are predominant nowadays, experimental methods such as wind-tunnel testing still play a critical role as verification and calibration tools. However, wind-tunnel testing is often too expensive, too slow or unavailable during aircraft conceptual design or the early development of immature technologies. It is here that testing free-flight subscale models - referred to as subscale flight testing (SFT) - could be an affordable and low-risk complementary method for obtaining both qualitative and quantitative information.Disruptive technological innovations have significantly altered both the cost and the capabilities of SFT during recent decades. Such innovations include the price performance of miniaturised electronics and communication systems, advances in rapid prototyping techniques and materials, the availability of specialised components from the booming drone market and the rapid development of open-source software and hardware, allowing for sophisticated and capable test platforms at a fraction of the cost compared to a few decades ago. It is therefore necessary to re-evaluate the benefits and limitations of SFT, as well as its role in contemporary aircraft design and technology development processes.This dissertation aims to contribute to knowledge on the use of the SFT method for research and development, focusing on low-cost, time-efficient solutions that are particularly suitable for small organisations and limited resources. The method’s challenges, needs and limitations are identified through a critical study of the physical similarity principles, an in-depth review of the experiences of other organisations, and practical field experiments with different subscale models in real conditions. Some of the proposed solutions include a low-cost data acquisition system with custom-made instruments, a novel method for automatic execution of excitation manoeuvres, specific techniques and parameter-identification methods for flight testing in confined airspaces, and a set of tools for the analysis and visualisation of flight data. The obtained results may serve as proof of the current possibilities to evaluate and demonstrate new technology through SFT using very limited economic and human resources.
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| 8. |
- Knöös Franzén, Ludvig, 1990-, et al.
(författare)
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A System of Systems Approach for Search and Rescue Missions
- 2020
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Konferensbidrag (refereegranskat)abstract
- System-of-Systems Engineering (SoSE) has become a constantly growing field within product development for complex systems. Systems are becoming more and more connected with other systems and the operational environment in general. This takes the development process to new levels of complexity where high degrees of uncertainties are expected due to ever occurring changes in the operational environment, and other external factors such as politics, economy, and technology. This creates a need of being able to understand the influence of changes early in the development process and to facilitate the systems? perseverance. The focus of the development shifts from fulfilling specific requirements, to being able to meet needs and deliver capabilities over time. Additionally, modeling and simulation for complex systems and System-of-Systems (SoS) becomes a valued alternative to the economically prohibited and almost impossible prototype testing. In consideration of this problem, the presented work introduces a method for both modeling and simulation of a SoS. The method uses ontology with description logic reasoning to derive and narrow down a SoS design space which is further analyzed using Agent Based Simulation (ABS). A Search and Rescue (SAR) scenario is used as a case study to test the method. Measures of Effectiveness (MoE), based on the time it takes to find a rescue subject and the cost of doing so, are used to evaluate the SoS performances. The presented method is envisioned to be used early in the development of complex systems and SoS to increase the overall understanding of them.
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| 9. |
- Kärnell, Samuel, 1993-
(författare)
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Fluid Power Pumps and the Electrification : With a Focus on Discrete Displacement Control in Load Handling Applications
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- More and more vehicles are being electrified. Mobile working machines and heavy trucks are not excluded, and these machines are often hydraulically intense. Electrification entails new requirements for the hydraulic system and its components, and these requirements must be taken into consideration.Hydraulic systems have looked similar for a long time, but now there is an opportunity to advance. Many things change when a diesel engine is replaced with an electric motor. For example, variable-speed control becomes more relevant, electric regeneration becomes possible, and the use of multiple prime movers becomes an attractive alternative. The noise from the hydraulic system will also be more noticeable when the diesel engine is gone. Furthermore, the introduction of batteries to the system makes the energy more valuable, since batteries are heavy and costly compared to a diesel tank. Therefore, it is commercially viable to invest in the hydraulic system.This thesis revolves around the heart of the hydraulic system, that also is the root of all evil. That is the pump. Traditionally, a pump has had either a fixed displacement or a continuously variable displacement. Here, the focus is on something in between, namely a pump with discrete displacement. The idea of discrete displacement is far from unique, but has not been investigated in detail in combination with variable speed before. In this thesis, a novel design for a quiet pump with discrete displacement is presented and analysed. The results show that discrete displacement is relevant from an energy perspective for machines working extensively at high pressure levels and with low flow rates, and that a few discrete values are enough to make a significant difference. However, for other cycles, the possible energy gains are very limited, but the discrete displacement can be a valuable feature if downsizing the electric machine is of interest.
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| 10. |
- Larsson, Felix, 1995-
(författare)
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Evaluation of Aircraft Actuator Technologies
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The flight control actuation system is one of the most critical systems in an aircraft. A failure of this system cannot occur, since it would have catastrophic consequences. The environment it operates in is considered as highly demanding, with temperatures ranging from -50 to +60 degrees Celsius, speeds from 0 to Mach 2+ and G-forces from -3 up to 9. At the same time, the system shall be as small and lightweight as possible, since every gram and cm3 will decrease the available payload and/or increase the total aircraft size, which in turn increase the fuel-burn. The preferred choice of technology for actuators has, since the late 1930s, been hydraulics. Hydraulic actuators are characterized by high power density, high technical maturity, high safety, and high response. With emerging benefits from the electric domain, research during the last decade has been focusing on electrified alternatives as the future alternative for actuators. With varying requirements on the actuators depending on the type of air-craft platform, it is not trivial when it is a better alternative to electrify the actuators. For example, with smaller platforms, the forces acting on the actuators will be lower in comparison with larger aircraft. The purpose of this thesis was to investigate if, and when certain technology may be the preferred alternative with regards to size and weight, performance, power consumption and thermal characteristics. Also, it was investigated how to compare different topologies which utilize different technologies, and how certain technology may affect the requirements of surrounding systems in the platform. This work has led to three different approaches for comparison and evaluation of actuator technology that can be applied in early conceptual design of aircraft platforms. The first approach can be used to ensure comparability of the topologies to be studied. The second approach focuses on modeling of performance and thermal impact and can be applied to study static and dynamic behavior of different technologies. The third approach can be used to study how size and weight of actuators will be affected by operational requirements, with special emphasis on high-level modeling with few inputs.
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