| 1. |
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| 2. |
- Aler Tubella, Andrea, 1990-, et al.
(författare)
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ACROCPoLis : a descriptive framework for making sense of fairness
- 2023
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Ingår i: FAccT '23. - : ACM Digital Library. - 9781450372527 ; , s. 1014-1025
-
Konferensbidrag (refereegranskat)abstract
- Fairness is central to the ethical and responsible development and use of AI systems, with a large number of frameworks and formal notions of algorithmic fairness being available. However, many of the fairness solutions proposed revolve around technical considerations and not the needs of and consequences for the most impacted communities. We therefore want to take the focus away from definitions and allow for the inclusion of societal and relational aspects to represent how the effects of AI systems impact and are experienced by individuals and social groups. In this paper, we do this by means of proposing the ACROCPoLis framework to represent allocation processes with a modeling emphasis on fairness aspects. The framework provides a shared vocabulary in which the factors relevant to fairness assessments for different situations and procedures are made explicit, as well as their interrelationships. This enables us to compare analogous situations, to highlight the differences in dissimilar situations, and to capture differing interpretations of the same situation by different stakeholders.
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| 3. |
- Baer, Katharina, 1984-, et al.
(författare)
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Aspects of Parameter Sensitivity for Series Hydraulic Hybrid Light-Weight Duty Vehicle Design
- 2016
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Ingår i: Proceedings of the 9th FPNI Ph.D. Symposium on Fluid Power (FPNI2016). - : American Society of Mechanical Engineers. - 9780791850473
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Konferensbidrag (refereegranskat)abstract
- Hybridization of a vehicle’s drivetrain can in principle help to improve its energy efficiency by allowing for recuperation of kinetic energy and modulating the engine’s load. How well this can be realized depends on appropriate sizing and control of the additional components. The system is typically designed sequentially, with the hardware setup preceding the development and tuning of advanced controller architectures. Taking an alternative approach, component sizing and controller tuning can be addressed simultaneously through simulation-based optimization.The results of such optimizations, especially with standard algorithms with continuous design variable ranges, can however be difficult to realize, considering for example limitations in available components. Furthermore, drive-cycle based optimizations are prone to cycle-beating. This paper examines the results of such simulation-based optimization for a series hydraulic hybrid vehicle in terms of sensitivity to variations in design parameters, system parameters and drive cycle variations. Additional relevant aspects concerning the definition of the optimization problem are pointed out.
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| 4. |
- Baer, Katharina, et al.
(författare)
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Component Sizing Study for a Light-Duty Series Hydraulic Hybrid Vehicle in Urban Drive Cycles
- 2013
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Konferensbidrag (refereegranskat)abstract
- With the focus on energy efficiency for many different kinds of vehicle applications,hybridization is considered a possible solution to reduce fuel consumption. While hybrid electric concepts are already available for passenger vehicles, and also considered for heavier applications, hybrid hydraulic alternatives have been mainly limited to the latter, which benefit most from the higher power density available. To study the different hybrid architectures and applications, a modeling framework for the system design is developed using the simulation tool Hopsan from Linköping University. Previously, the model of a series hydraulic hybrid vehicle was introduced, a light-duty vehicle simulated over two standard urban drive cycles, and its potential for further work established. In this paper, the model is extended by including a simple combustion engine power management to provide for more realistic propulsion of the hydraulic drivetrain, showing the potential to operate a series hydraulic hybrid vehicle’s engine in more efficient regions. Additionally, the design is studied concerning the effects of a variation of key component sizes on the accuracy and energy efficiency objectives. Instead of subjecting the system to (multi- objective) optimization, at this stage the individual component’s influence is studied, and the objectives are dealt with separately from each other to eliminate the need for compromise between them, both to gain a better understanding of the interdependencies.
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| 5. |
- Baer, Katharina, et al.
(författare)
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Design Study and Parameter Optimization for a Light-Weight Series Hydraulic Hybrid Vehicle
- 2015
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Konferensbidrag (refereegranskat)abstract
- Hydraulic hybrid drives are one potential way of improving the fuel efficiency of vehicles, including the possi-bility of recuperating braking energy in a hydraulic accumulator. The high power density of fluid power is mainly advantageous for heavy vehicles, or duty cycles characterized with frequent braking and acceleration. For smaller vehicles, hydraulic hybrid drives are thus most interesting under urban and suburban driving conditions. Amongst the existing architectures, the series hydraulic hybrid offers the advantage of operating the internal combustion engine independently of the vehicle speed, at the cost of a less efficient transmission path than a purely mechanical one. Previously, a series hydraulics hybrid light-duty vehicle was modelled in the transmission-line modelling (TLM)-based simulation software Hopsan from the division of Fluid and Mechatronic Systems (Flumes) at Linköping University. This paper studies through simulation-based optimi-zation how the fuel-optimal vehicle design is affected by various mixes of urban and suburban driving requirements. Both the system’s hardware and the parameters of a basic control strategy are considered. The results show quite similar designs for most performance requirements combinations, and can be the base for further studies addressing additional requirements, conditions and objectives.
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| 6. |
- Baer, Katharina, 1984-, et al.
(författare)
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Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle
- 2019
-
Ingår i: International Journal of Fluid Power. - : Taylor & Francis. - 1439-9776 .- 2332-1180. ; 20:1, s. 27-51
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Tidskriftsartikel (refereegranskat)abstract
- Hybridisation of hydraulic drivetrains offers the potential of efficiency improvement for on – and off-road applications. To realise the advantages, a carefully designed system and corresponding control strategy are required, which are commonly obtained through a sequential design process. Addressing component selection and control parameterisation simultaneously through simulation-based optimisation allows for exploration of a large design space as well as design relations and trade-offs, and their evaluation in dynamic conditions which exist in real driving scenarios. In this paper, the optimisation framework for a hydraulic hybrid vehicle is introduced, including the simulation model for a series hybrid architecture and component scaling considerations impacting the system’s performance. A number of optimisation experiments for an on-road light-duty vehicle, focused on standard-drive-cycle-performance, illustrate the impact of the problem formulation on the final design and thus the complexity of the design problem. The designs found demonstrate both the potential of energy storage in series hybrids, via an energy balance diagram, as well as some challenges. The framework presented here provides a base for systematic evaluation of design alternatives and problem formulation aspects.
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| 7. |
- Baer, Katharina, et al.
(författare)
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Modeling of a Series Hybrid Hydraulic Drivetrain for a Light-Duty Vehicle in Hopsan
- 2013
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Ingår i: Conference proceedings. - Linköping, Sweden : Linköping University Electronic Press. - 9789175195728 ; , s. 107-112
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Konferensbidrag (refereegranskat)abstract
- Hydraulic hybrids continue to receive attention as a possible solution in the search for improved fuel economy for different vehicle types. This paper presents a model for a series hydraulic hybrid light-duty vehicle, developed in the Hopsan simulation tool of Linköping University’s Division of Fluid and Mechatronic Systems (Flumes). Focusing on the hydraulic transmission which employs a pump control based on the hydraulic accumulator’s state-of-charge (SoC), several simplifications were made, especially concerning mechanical components. Simulation over two urban standard cycles shows promising results concerning dynamic performance and energy recuperation potential, provided sufficient component sizing to compensate for the mechanical limitations. This paper lays the foundation for both a further refined model - suitable for optimizing the full drivetrain, including component sizing and controller parameterization - and the development of comparable models for parallel and power-split hybrid architectures.
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| 8. |
- Baer, Katharina, 1984-, et al.
(författare)
-
Robustness and performance evaluations for simulation-based control and component parameter optimization for a series hydraulic hybrid vehicle
- 2020
-
Ingår i: Engineering optimization (Print). - : Taylor & Francis. - 0305-215X .- 1029-0273. ; 52:3, s. 446-464
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Tidskriftsartikel (refereegranskat)abstract
- Simulation-based optimization is a useful tool in the design of complex engineering products. Simulation models are used to capture numerous aspects of the design problem for the objective function. Optimization results obtained can be assessed from various perspectives. In this study, component and control optimization of a series hydraulic hybrid vehicle is used as an application, and different robustness and performance aspects are evaluated. Owing to relatively high computational loads, efficient optimization algorithms are important to provide sufficient quality of results at reasonable computational costs. To estimate problem complexity and evaluate optimization algorithm performance, the definitions for information entropy and the related performance index are extended. The insights gained from various simulation-based optimization experiments and their subsequent analysis help characterize the efficiency of the optimization problem formulation and parameterization, as well as optimization algorithm selection with respect to parallel computation capabilities for further development of the model and optimization framework.
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| 9. |
- Baer, Katharina, 1984-
(författare)
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Simulation-Based Optimization of a Series Hydraulic Hybrid Vehicle
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hybrid transmissions are characterized by their utilization of more than one form of energy storage. They have the potential to help reduce overall fuel consumption and vehicle emissions by providing the possibility of brake energy recuperation and prime mover operation management. Electric hybrids and electric vehicle drives are nowadays ubiquitous, and mechanical energy storage in flywheel has been investigated in the past. The use of fluid power technology with a combustion engine has also been investigated since the late 1970s, and is frequently revisited.Hydraulic hybridization is especially attractive for heavy vehicles with frequent braking and acceleration which benefit most from fluid power components’ high power density, typically busses, delivery or refuse vehicles, and vehicles with existing hydraulic circuits and transmissions, such as forest and construction machinery, but have been considered for smaller vehicles as well.Due to the characteristic discharge profile of hydraulic energy storage, special attention needs to be paid to control aspects in the design process to guarantee drivability of the vehicle. In this respect, simulation models can be of use in early design process stages for cheaper and faster evaluation of concepts and designs than physical experiments and prototyping, and to generate better understanding of the system studied. Engineering optimization aids in the systematic exploration of a given design space, to determine limits and potentials, evaluate trade-offs and potentially find unexpected solutions. In the optimization of a hydraulic hybrid transmission, the integration of component and controller design is of importance, and different strategies (sequential, iterative, bi-level and simultaneous approaches) are conceivable, with varying consequences for the implementation.This thesis establishes a simulation-based optimization framework for a hydraulic hybrid transmission with series architecture. Component and control parameter optimization are addressed simultaneously, using a rule-based supervisory control strategy. The forward-facing dynamic simulation model at the centre of the framework is built in Hopsan, a multi-disciplinary open-source tool developed at Linköping University. The optimization is set up and conducted for an example application of an on-road light-duty truck over standard drive cycles. Both results from these experiments as well as the framework itself are studied and evaluated. Relevant design aspects, such as explicit design relations to be considered and performance requirements for more robust design, are identified and addressed, and the optimization problem is analysed with regard to algorithm performance and problem formulation. The final result is an optimization framework that can be adjusted for further in-depth studies, for example through the inclusion of additional components or optimization objectives, and extendable for comparative analysis of different topologies, applications and problem formulations.
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| 10. |
- Baer, Katharina, et al.
(författare)
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System Parameter Study for a Light-Weight Series Hydraulic Hybrid Vehicle
- 2014
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Ingår i: PROCEEDINGS OF THE 8TH FPNI PH.D SYMPOSIUM ON FLUID POWER, 2014. - : ASME Press. - 9780791845820 ; , s. V001T03A004-
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Konferensbidrag (refereegranskat)abstract
- Amongst the hybrid vehicle propulsion solutions aiming to improve fuel efficiency, hybrid electric solutions currently receive most attention, especially on the market. However, hydraulic hybrids are an interesting alternative, especially for heavier vehicles due to higher power density which is beneficial if higher masses are moved. As a step towards a comprehensive design framework to compare several possible hydraulic hybrid architectures for a specified application and usage profile, the model of a series hydraulic hybrid vehicle was previously introduced and initially studied concerning component sizing for an exemplary light-duty vehicle in urban traffic. The vehicle is modeled in the Hopsan simulation tool. A comparably straight-forward engine management is used for the vehicle control; both pump and engine controls are based on the hydraulic accumulator’s state-of-charge. The model is developed further with respect to the accumulator component model. Based on that, the influence of several system and component parameters, such as maximum system pressure and engine characteristics, as well as controller parameters on the vehicle’s performance is analyzed. The goal is to allow for more understanding of the system’s characteristics to facilitate future optimization of the system.
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| 11. |
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| 12. |
- Björklund, Henrik, et al.
(författare)
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Between a Rock and a Hard Place : Parsing for Hyperege Replacement DAG Grammars
- 2016
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Ingår i: Proc. 10th International Conference on Language and Automata Theory and Applications (LATA 2016). - Cham : Springer Publishing Company. - 9783319300009 - 9783319299990 ; , s. 521-532
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Konferensbidrag (refereegranskat)abstract
- Motivated by applications in natural language processing, we study the uniform membership problem for hyperedge-replacement grammars that generate directed acyclic graphs. Our major result is a low-degree polynomial-time algorithm that solves the uniform membership problem for a restricted type of such grammars. We motivate the necessity of the restrictions by two different NP-completeness results.
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| 13. |
- Björklund, Henrik, et al.
(författare)
-
Minimisation and Characterisation of Order-Preserving DAG Grammars
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Order-preserving DAG grammars (OPDGs) is a formalism for processing semantic infor- mation in natural languages [5, 4]. OPDGs are sufficiently expressive to model abstract meaning representations, a graph-based form of semantic representation in which nodes en- code objects and edges relations. At the same time, they allow for efficient parsing in the uniform setting, where both the grammar and subject graph are taken as part of the input.In this article, we introduce an initial algebra semantic for OPDGs, which allows us to view them as regular tree grammars. This makes it possible to transfer a number of results from that domain to OPDGs, both in the unweighted and the weighted case. In particular, we show that deterministic OPDGs can be minimised efficiently, and that they are learnable in the so-called MAT setting. To conclude, we show that the languages generated by OPDGs are MSO-definable.
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| 14. |
- Björklund, Henrik, et al.
(författare)
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On the Regularity and Learnability of Ordered DAG Languages
- 2017
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Ingår i: Implementation and Application of Automata. - Cham : Springer International Publishing. - 9783319601335 - 9783319601342 ; , s. 27-39
-
Konferensbidrag (refereegranskat)abstract
- Order-Preserving DAG Grammars (OPDGs) is a subclass of Hyper-Edge Replacement Grammars that can be parsed in polynomial time. Their associated class of languages is known as Ordered DAG Lan- guages, and the graphs they generate are characterised by being acyclic, rooted, and having a natural order on their nodes. OPDGs are useful in natural-language processing to model abstract meaning representa- tions. We state and prove a Myhill-Nerode theorem for ordered DAG languages, and translate it into a MAT-learning algorithm for the same class. The algorithm infers a minimal OPDG G for the target language in time polynomial in G and the samples provided by the MAT oracle.
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| 15. |
- Björklund, Henrik, et al.
(författare)
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Parsing Weighted Order-Preserving Hyperedge Replacement Grammars
- 2019
-
Ingår i: Proceedings of the 16th Meeting on the Mathematics of Language. - : Association for Computational Linguistics. ; , s. 1-11
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Konferensbidrag (refereegranskat)abstract
- We introduce a weighted extension of the recently proposed notion oforder-preserving hyperedge-replacement grammars and prove that the weightof a graph according to such a weighted graph grammar can be computeduniformly in quadratic time (under assumptions made precise in the paper).
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| 16. |
- Björklund, Henrik, et al.
(författare)
-
Parsing Weighted Order-Preserving Hyperedge Replacement Grammars
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We introduce a weighted extension of the recently proposed notion of order-preserving hyperedge-replacement grammars and prove that the weight of a graph according to such a weighted graph grammar can be computed uniformly in quadratic time (under assumptions made precise in the paper).
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| 17. |
- Björklund, Henrik, et al.
(författare)
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Tree-based generation of restricted graph languages
- 2024
-
Ingår i: International Journal of Foundations of Computer Science. - : World Scientific. - 0129-0541. ; 35:1 & 2, s. 215-243
-
Tidskriftsartikel (refereegranskat)abstract
- Order-preserving DAG grammars (OPDGs) is a formalism for representing languages of structurally restricted graphs. As demonstrated in [17], they are sufficiently expressive to model abstract meaning representations in natural language processing, a graph-based form of semantic representation in which nodes encode objects and edges relations. At the same time, they can be parsed in O (n2 + nm) , where m and n are the sizes of the grammar and the input graph, respectively. In this work, we provide an initial algebra semantic for OPDGs, which allows us to view them as regular tree grammars under an equivalence theory. This makes it possible to transfer results from the field of formal tree languages to the domain of OPDGs, both in the unweighted and the weighted case. In particular, we show that deterministic OPDGs can be minimised efficiently, and that they are learnable under the \minimal adequeate teacher" paradigm, that is, by querying an oracle for equivalence between languages, and membership of individual graphs. To conclude, we demonstrate that the languages generated by OPDGs are definable in monadic second-order logic.
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| 18. |
- Björklund, Henrik, et al.
(författare)
-
Uniform Parsing for Hyperedge Replacement Grammars
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that hyperedge-replacement grammars can generate NP-complete graph languages even under seemingly harsh restrictions. This means that the parsing problem is difficult even in the non-uniform setting, in which the grammar is considered to be fixed rather than being part of the input. Little is known about restrictions under which truly uniform polynomial parsing is possible. In this paper we propose a low-degree polynomial-time algorithm that solves the uniform parsing problem for a restricted type of hyperedge-replacement grammars which we expect to be of interest for practical applications.
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| 19. |
- Björklund, Henrik, et al.
(författare)
-
Uniform Parsing for Hyperedge Replacement Grammars
- 2021
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Ingår i: Journal of computer and system sciences (Print). - : Elsevier. - 0022-0000 .- 1090-2724. ; 118, s. 1-27
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that hyperedge-replacement grammars can generate NP-complete graph languages even under seemingly harsh restrictions. This means that the parsing problem is difficult even in the non-uniform setting, in which the grammar is considered to be fixed rather than being part of the input. Little is known about restrictions under which truly uniform polynomial parsing is possible. In this paper we propose a low-degree polynomial-time algorithm that solves the uniform parsing problem for a restricted type of hyperedge-replacement grammars which we expect to be of interest for practical applications.
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| 20. |
- Björklund, Henrik, et al.
(författare)
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Uniform vs. Nonuniform Membership for Mildly Context-Sensitive Languages : A Brief Survey
- 2016
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Ingår i: Algorithms. - : MDPI. - 1999-4893. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Parsing for mildly context-sensitive language formalisms is an important area within natural language processing. While the complexity of the parsing problem for some such formalisms is known to be polynomial, this is not the case for all of them. This article presents a series of results regarding the complexity of parsing for linear context-free rewriting systems and deterministic tree-walking transducers. We discuss the difference between uniform and nonuniform complexity measures and how parameterized complexity theory can be used to investigate how different aspects of the formalisms influence how hard the parsing problem is. The main results we survey are all hardness results and indicate that parsing is hard even for relatively small values of parameters such as rank and fan-out in a rewriting system.
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| 21. |
- Braun, Robert, et al.
(författare)
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Full Vehicle Simulation of Forwarder with Semi Active Suspension using Co-simulation
- 2016
-
Konferensbidrag (refereegranskat)abstract
- A major concern in the forest industry is impact on the soil caused by forest machines during harvesting. A six-wheel pendulum arm forwarder is being developed. The new forwarder aims at reducing soil damage by an even pressure distribution and smooth torque control and thereby also improving the working environment. The suspension contains pendulum arms on each wheel controlled by a hydraulic load sensing system in combination with accumulator.A natural approach is to model each part of a system in the bestsuited software. In this case, the hydraulic system is modelled in the Hopsan simulation tool, while the vehicle mechanics is modelled in Adams. To understand the whole system it is necessary to simulate all subsystems together. An open standard for this is the Functional Mock-up Interface. This makes it possible to investigate the interaction between the hydraulic system and the multi-body mechanic model.This paper describes how different simulation tools can be combined to support the development process. The technique is applied to the forwarder’s pendulum suspension. Controllers for height and soil force are optimized to minimize soil damage and maximize comfort for the operator.
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| 22. |
- Braun, Robert, 1984-, et al.
(författare)
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Hopsan: An Open-Source Tool for Rapid Modelling and Simulation of Fluid and Mechatronic Systems
- 2020
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Ingår i: <em>Proceedings of the BATH/ASME 2020 Symposium on Fluid Power and Motion Control</em>. - 9780791883754
-
Konferensbidrag (refereegranskat)abstract
- Hopsan is an open-source simulation package developed as a collaboration project between industry and academia. The simulation methodology is based on transmission line modelling, which provides several benefits such as linear model scalability, numerical robustness and parallel simulation. All sub-models are pre-compiled, so that no compilation is required prior to starting a simulation. Default component libraries are available for hydraulic, mechanic, pneumatic, electric and signal domains. Custom components can be written in C++ or generated from Modelica and Mathematica. Support for simulation-based optimization is provided using population-based, evolutionary or direct-search algorithms. Recent research has largely focused on co-simulation with other simulation tools. This is achieved either by using the Functional Mock-up Interface standard, or by tool-to-tool communications. This paper provides a description of the program and its features, the current status of the project, and an overview of recent and ongoing use cases from industry and academia.
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| 23. |
- Chábera, Pavel, et al.
(författare)
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A low-spin Fe(iii) complex with 100-ps ligand-to-metal charge transfer photoluminescence
- 2017
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 543:7647, s. 695-699
-
Tidskriftsartikel (refereegranskat)abstract
- Transition-metal complexes are used as photosensitizers1, in light-emitting diodes, for biosensing and in photocatalysis2. A key feature in these applications is excitation from the ground state to a charge-transfer state3,4; the long charge-transfer-state lifetimes typical for complexes of ruthenium5 and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron6 and copper7 being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs6,8,9,10, it remains a formidable scientific challenge11 to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered12 photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers13,14,15. Here we present the iron complex [Fe(btz)3]3+ (where btz is 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene)), and show that the superior σ-donor and π-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(iii) d5 complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer (2LMCT) state that is rarely seen for transition-metal complexes4,16,17. The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers.
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| 24. |
- Dell' Amico, Alessandro, et al.
(författare)
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Modelling and experimental verification of a secondary controlled six-wheel pendulum arm forwarder
- 2015
-
Ingår i: the 13th European Conference of ISTVS. - 9781942112464 ; , s. 1-10
-
Konferensbidrag (refereegranskat)abstract
- One of the major concerns in the forest industry is the impact on the soil caused by the forest machines duringharvesting, where damages can have a negative impact on e.g. further growth. One of the main reasons is wheel slip.Another concern is the working environment of the operator due to the harsh ground in the forest. Both these issueshave a negative impact on productivity. An attempt to overcome these challenges is made within a collaborative researchproject, which among others also includes Linköping University, where a new six-wheel pendulum arm forwarder isbeing developed. The new forwarder aims at reducing the soil damage by an even pressure distribution and smooth torquecontrol, as well as increased damping of the complete chassis, and thereby improving the working environment. This ispossible since each wheel, driven by its own hydraulic motor, is attached to a pendulum arm allowing to control the heightof each wheel independently of each other. The forwarder has a total maximum weight of 31 tonnes, including 14 tonnesmaximum load. It consists of two steerable joints and is driven by a 360 bhp diesel engine. The transmission consists oftwo hydraulic pumps and six hydraulic motors.This paper deals with the development of the driveline and presents the first experimental tests of the implementedcontrol strategies, where a secondary control approach is chosen for its ability to individually control the torque on eachwheel. The control strategies, presented in the paper, include pressure control, velocity control of the vehicle and ananti-slip controller. To support the development of the control strategies, models of the vehicle and hydraulic subsystemsare derived. The aim with this paper is to verify the concepts on the actual vehicle. The initial results are promising,indicating that the suggested concept is feasible.
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| 25. |
- Ericson, Fredric, et al.
(författare)
-
Electronic structure and excited state properties of iron carbene photosensitizers - A combined X-ray absorption and quantum chemical investigation
- 2017
-
Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 683, s. 559-566
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and excited state properties of a series of iron carbene photosensitizers are elucidated through a combination of X-ray absorption measurements and density functional theory calculations. The X-ray absorption spectra are discussed with regard to the unusual bonding environment in these carbene complexes, highlighting the difference between ferrous and ferric carbene complexes. The valence electronic structure of the core excited FeIII-3d5 complex is predicted by calculating the properties of a CoIII-3d6 carbene complex using the Z+1 approximation. Insight is gained into the potential of sigma-donating ligands as strategy to tune properties for light harvesting applications.
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| 26. |
- Ericson, Liselott, 1976-, et al.
(författare)
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An Electric Hydraulic Hybrid Light Vehicle with Energy Recovery
- 2011
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Ingår i: 52nd National Conference on Fluid Power. - Las. - 0942220498 ; , s. 741-749
-
Konferensbidrag (refereegranskat)abstract
- A three wheeled electric hydraulic hybrid vehicle with tiltingbody was built and tested at Linköping University as a partof a student project. The goal of the student project wasto design and fabricate an environmentally friendly vehicleto enter the Formula ATA Electric & Hybrid Italy 2009 competition.The design of the vehicle was based on the rulesand requirements of the competition. The vehicle was alsoprepared for a hydraulic recovery system which was laterimplemented on the vehicle. Hydraulic motor/pump unitsare used to brake and recover energy and to provide additionalboost during acceleration. The energy recovery storageis hydraulic gas accumulators, while the primary propulsionsystem is electrical with Li-Fe batteries. Gas accumulatorshave very high power density superior to electricalbatteries.In this paper, the design of the hydraulic recovery system isdescribed along with simulation and experimental results.The concept shows high potential and the tests show a20 % recovery of the kinetic energy by the hydraulic systemfor a given cycle.
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| 27. |
- Ericson, Liselott, 1976-, et al.
(författare)
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MODELLING OF A SECONDARY CONTROLLED SIX-WHEEL PENDULUM ARM FORWARDER
- 2015
-
Konferensbidrag (refereegranskat)abstract
- One of the major concerns in the forest industry is the impact on the soil caused by the forest machines during harvesting, where damage can have a negative impact on growth at replanting for example. Another concern is the working environment of the operator. Both these issues have a negative impact on productivity. A new six-wheel pendulum arm forwarder is being developed within a collaborative research project. The new forwarder aims to reduce soil damage by means of an even pressure distribution and smooth torque control. This paper presents the first step in the development of the driveline, where a secondary control approach is chosen for its ability to control the motion of each wheel individually. Simulation models of both vehicle and driveline have been constructed developed, partly for the development of the control strategy, and partly for evaluation. A speed control concept and a torque control concept have both been evaluated for different scenarios with regard to their ability to reduce wheel slip. Results have shown that a velocity control approach is more sensitive to kinematic model accuracy while wheel slip is handled automatically. A torque control approach is more robust towards model accuracy while the reduction of slip is dependent on an accurate model.
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| 28. |
- Ericson, Petter, 1986-
(författare)
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A bottom-up automaton for tree adjoining languages
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Current tree parsing algorithms for nonregular tree languages all have superlinear running times, possibly limiting their practical applicability. We present a bottom-up tree automaton that captures exactly the tree-adjoining languages in the non-deterministic case. The determinstic case captures a strict superset of the regular tree languages, while preserving running times linear in the size of the tree.
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| 29. |
- Ericson, Petter, 1986-
(författare)
-
Complexity and expressiveness for formal structures in Natural Language Processing
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The formalized and algorithmic study of human language within the field of Natural Language Processing (NLP) has motivated much theoretical work in the related field of formal languages, in particular the subfields of grammar and automata theory. Motivated and informed by NLP, the papers in this thesis explore the connections between expressibility – that is, the ability for a formal system to define complex sets of objects – and algorithmic complexity – that is, the varying amount of effort required to analyse and utilise such systems. Our research studies formal systems working not just on strings, but on more complex structures such as trees and graphs, in particular syntax trees and semantic graphs. The field of mildly context-sensitive languages concerns attempts to find a useful class of formal languages between the context-free and context-sensitive. We study formalisms defining two candidates for this class; tree-adjoining languages and the languages defined by linear context-free rewriting systems. For the former, we specifically investigate the tree languages, and define a subclass and tree automaton with linear parsing complexity. For the latter, we use the framework of parameterized complexity theory to investigate more deeply the related parsing problems, as well as the connections between various formalisms defining the class. The field of semantic modelling aims towards formally and accurately modelling not only the syntax of natural language statements, but also the meaning. In particular, recent work in semantic graphs motivates our study of graph grammars and graph parsing. To the best of our knowledge, the formalism presented in Paper III of this thesis is the first graph grammar where the uniform parsing problem has polynomial parsing complexity, even for input graphs of unbounded node degree.
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| 30. |
- Ericson, Per G P, 1956-, et al.
(författare)
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A 14,000-year-old genome sheds light on the evolution and extinction of a Pleistocene vulture
- 2022
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- The New World Vulture [Coragyps] occidentalis (L. Miller, 1909) is one of many species that were extinct by the end of the Pleistocene. To understand its evolutionary history we sequenced the genome of a 14,000 year old [Coragyps] occidentalis found associated with megaherbivores in the Peruvian Andes. occidentalis has been viewed as the ancestor, or possibly sister, to the extant Black Vulture Coragyps atratus, but genomic data shows occidentalis to be deeply nested within the South American clade of atratus. Coragyps atratus inhabits lowlands, but the fossil record indicates that occidentalis mostly occupied high elevations. Our results suggest that occidentalis evolved from a population of atratus in southwestern South America that colonized the High Andes 300 to 400 kya. The morphological and morphometric differences between occidentalis and atratus may thus be explained by ecological diversification following from the natural selection imposed by this new and extreme, high elevation environment. The sudden evolution of a population with significantly larger body size and different anatomical proportions than atratus thus constitutes an example of punctuated evolution.
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| 31. |
- Ericson, Petter, 1986-
(författare)
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Investigating different graph representations of semantics
- 2016
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Konferensbidrag (refereegranskat)abstract
- Combinatory Categorial Grammar is a generic approach to the mechanical understanding of language, where movement is minimised in favour of using combinators such as B (composition) and T (type lifting) to clearly define in which ways various constituents can refer to each other. Taking the tree languages induced by the syntactic derivations and connecting the various leaves linked through the semantics, one ends up with a class of graph languages. The present work aims to point out promising avenues of research in order to investigate this class, specifically in terms of similarities with other graph-based semantic representations, such as Abstract Meaning Representations (AMR), and furthermore what graph generating or recognising formalism would be most suitable to define the class characteristics.
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| 32. |
- Ericson, Petter, 1986-, et al.
(författare)
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Musereduce : a generic framework for hierarchical music analysis
- 2023
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Ingår i: Music Encoding Conference 2022 Proceedings. - : Music Encoding Initiative. ; , s. 40-51
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Konferensbidrag (refereegranskat)abstract
- In comparison to computational linguistics, with its abundance of natural-language datasets, corpora of music analyses are rather fewer and generally smaller. This is partly due to difficulties inherent to the encoding of music analyses, whose multimodal representations—typically a combination of music notation, graphic notation, and natural language—are designed for communication between human musician-analysts, not for automated large-scale data analysis. Analyses based on hierarchical models of tonal structure, such as Heinrich Schenker’s, present additional notational and encoding challenges, since they establish relations between non- adjacent tones, and typically interpret successions of tones as expressions of abstract chordal sonorities, which may not be literally present in the music score. Building on a published XML format by Rizo and Marsden (2019), which stores analyses alongside symbolically encoded scores, this paper presents a generic graph model for reasoning about music analyses, as well as a graphical web application for creating and encoding music analyses in the aforementioned XML format. Several examples are given showing how various techniques of music analysis, primarily but not necessarily hierarchical, might be unambiguously represented through this model.
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| 33. |
- Ericson, Petter, 1986-
(författare)
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Order-preserving graph grammars
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of semantic modelling concerns formal models for semantics, that is, formal structures for the computational and algorithmic processing of meaning. This thesis concerns formal graph languages motivated by this field. In particular, we investigate two formalisms: Order-Preserving DAG Grammars (OPDG) and Order-Preserving Hyperedge Replacement Grammars (OPHG), where OPHG generalise OPDG.Graph parsing is the practise of, given a graph grammar and a graph, to determine if, and in which way, the grammar could have generated the graph. If the grammar is considered fixed, it is the non-uniform graph parsing problem, while if the grammars is considered part of the input, it is named the uniform graph parsing problem. Most graph grammars have parsing problems known to be NP-complete, or even exponential, even in the non-uniform case. We show both OPDG and OPHG to have polynomial uniform parsing problems, under certain assumptions.We also show these parsing algorithms to be suitable, not just for determining membership in graph languages, but for computing weights of graphs in graph series.Additionally, OPDG is shown to have several properties common to regular languages, such as MSO definability and MAT learnability. We moreover show a direct corresponcence between OPDG and the regular tree grammars.Finally, we present some limited practical experiments showing that real-world semantic graphs appear to mostly conform to the requirements set by OPDG, after minimal, reversible processing.
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| 34. |
- Ericson, Petter, 1986-, et al.
(författare)
-
Tracing class and capitalism in critical AI research
- 2024
-
Ingår i: tripleC. - : TripleC. - 1726-670X. ; 22:1, s. 307-328
-
Tidskriftsartikel (refereegranskat)abstract
- This article explores the rapidly developing field of Critical AI Studies and its relation to issues of class and capitalism through a hybrid approach based on distant reading of a newly collected corpus of 300 full-text scientific articles, the creation of which is itself a first attempt at properly delineating the field. We find that words related to issues of class are predominantly but not exclusively confined to a set of studies that make up their own distinct subfield of Critical AI Studies, in contrast to, e.g., issues of race and gender, which are more broadly present in the corpus.
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| 35. |
- Eskilson, Olof, 1992-, et al.
(författare)
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Self-Assembly of Mechanoplasmonic Bacterial Cellulose-Metal Nanoparticle Composites
- 2020
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 30:40
-
Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC-NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self-assembly strategy is described for fabrication of complex and well-defined BC-NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self-assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near-field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.
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| 36. |
- Finn, Eric Lyckegård, et al.
(författare)
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The use of accelerometer bracelets to evaluate arm motor function over a stroke rehabilitation period – an explorative observational study
- 2024
-
Ingår i: Journal of NeuroEngineering and Rehabilitation. - 1743-0003. ; 21:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Assessments of arm motor function are usually based on clinical examinations or self-reported rating scales. Wrist-worn accelerometers can be a good complement to measure movement patterns after stroke. Currently there is limited knowledge of how accelerometry correlate to clinically used scales. The purpose of this study was therefore to evaluate the relationship between intermittent measurements of wrist-worn accelerometers and the patient’s progression of arm motor function assessed by routine clinical outcome measures during a rehabilitation period. Methods: Patients enrolled in in-hospital rehabilitation following a stroke were invited. Included patients were asked to wear wrist accelerometers for 24 h at the start (T1) and end (T2) of their rehabilitation period. On both occasions arm motor function was assessed by the modified Motor Assessment Scale (M_MAS) and the Motor Activity Log (MAL). The recorded accelerometry was compared to M_MAS and MAL. Results: 20 patients were included, of which 18 completed all measurements and were therefore included in the final analysis. The resulting Spearman’s rank correlation coefficient showed a strong positive correlation between measured wrist acceleration in the affected arm and M-MAS and MAL values at T1, 0.94 (p < 0.05) for M_MAS and 0.74 (p < 0.05) for the MAL values, and a slightly weaker positive correlation at T2, 0.57 (p < 0.05) for M_MAS and 0.46 − 0.45 (p = 0.06) for the MAL values. However, no correlation was seen for the difference between the two sessions. Conclusions: The results confirm that the wrist acceleration can differentiate between the affected and non-affected arm, and that there is a positive correlation between accelerometry and clinical measures. Many of the patients did not change their M-MAS or MAL scores during the rehabilitation period, which may explain why no correlation was seen for the difference between measurements during the rehabilitation period. Further studies should include continuous accelerometry throughout the rehabilitation period to reduce the impact of day-to-day variability.
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| 37. |
- Fjeldså, Jon, et al.
(författare)
-
What’s special about passerines?
- 2020
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Ingår i: <em>The Largest Avian Radiation</em>. - Barcelona : Lynx Edicions. - 9788416728336 ; , s. 27-34
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 38. |
- Harasim, Daniel, et al.
(författare)
-
The jazz harmony treebank
- 2020
-
Ingår i: Proceedings of the 21st ISMIR Conference. ; , s. 207-215
-
Konferensbidrag (refereegranskat)abstract
- Grammatical models which represent the hierarchical structure of chord sequences have proven very useful in recent analyses of Jazz harmony. A critical resource for building and evaluating such models is a ground-truth database of syntax trees that encode hierarchical analyses of chord sequences. In this paper, we introduce the Jazz Harmony Treebank (JHT), a dataset of hierarchical analyses of complete Jazz standards. The analyses were created and checked by experts, based on lead sheets from the open iRealPro collection. The JHT is publicly available in JavaScript Object Notation (JSON), a human-understandable and machine-readable format for structured data. We additionally discuss statistical properties of the corpus and present a simple open-source web application for the graphical creation and editing of trees which was developed during the creation of the dataset.
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| 39. |
- Jonsson, Knud Andreas, et al.
(författare)
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Complete subspecies-level phylogeny of the Oriolidae (Aves: Passeriformes): Out of Australasia and return
- 2019
-
Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier. - 1055-7903 .- 1095-9513. ; 137, s. 200-209
-
Tidskriftsartikel (refereegranskat)abstract
- Old World orioles (Oriolidae) are medium-sized passerine birds confined largely to forested areas of Africa, Eurasia and Australasia. We present a new complete molecular (mtDNA) subspecies level phylogeny of the Oriolidae including all 113 taxa (35 species) together with a backbone phylogeny of 19 taxa from the main Oriolus clades based on (i) 21 nuclear genes, (ii) whole mito-genomes, and (iii) genome-wide ultraconserved elements. We use this phylogeny to assess systematic relationships and the biogeographical history of this avian family. Furthermore, we use morphological measurements to investigate the relationship between size and shape axes and upstream or back-colonization of this extensive island region from Asia. We show that several subspecies or groups of subspecies may warrant species rank and we find a continental example of two morphologically distinct species (O. mellianus/O. traillii) being genetically (mtDNA) very similar. Biogeographically, we confirm previous findings that members of the Oriolidae originated in Australo-Papua. Dispersal out of this area took place around 15 Mya to southeast Asia and Africa, and from Africa to the Palearctic followed by recolonization of the Indonesian and Philippine island region during the Plio-Pleistocene. Recolonisation of the Indonesian and Philippine islands coincided with an increase in body size, which may have facilitated the ability to co-exist with other congenerics.
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| 40. |
- Kärnell, Samuel, 1993-
(författare)
-
Fluid Power Pumps and the Electrification : With a Focus on Discrete Displacement Control in Load Handling Applications
- 2020
-
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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| 41. |
- Kärnell, Samuel, 1993-
(författare)
-
On Electrified Fluid Power Systems in Mobile Machinery
- 2022
-
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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| 42. |
- Larsson, L. Viktor, 1990-
(författare)
-
Control of Hybrid Hydromechanical Transmissions
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with control aspects of complex hybrid hydromechanical transmissions for heavy mobile working machines. Control problems are identified and solved to facilitate the implementation and use of these systems.Fuel prices and environmental concerns have increased the interest in hybrid hydromechanical transmissions for heavy mobile working machines. Hybridisation, the introduction of a secondary energy source in the transmission, offers attractive improvements in terms of both fuel efficiency and performance. These improvements are, in turn, enabled by software control. A complex transmission architecture has several components that need to interact in a stable manner. In addition, optimal utilisation of the added energy source is required to maximise fuel savings. Meanwhile, there is a strong trend towards automation, where many of the operator’s difficult control tasks need to be managed by computers. Sophisticated control strategies are therefore needed, along with a deeper understanding of dynamic properties.Previous research on the control of hybrid hydromechanical transmissions has primarily focussed on on-road applications. The working conditions of heavy working machines place different requirements on the transmission, which is also reflected in the control strategy.This thesis highlights the importance of fast response of the variable displacement pump/motors used in hybrid hydromechanical transmissions. Their central position in the interface between hydraulics and mechanics makes their dynamic performance a limiting factor both for the stability of the transmission control loops and in the realisation of smooth mode shifts in multiplemode transmissions. Dynamic models and control strategies for displacement actuators are derived and validated in simulation and experiments. A linear model for dynamic analysis of a general hybrid hydromechanical transmission for heavy working machines is derived and a powertrain control strategy based on decoupled control is proposed. The strategy is verified in simulations and experiments in hardware-in-the-loop simulations, and may be used in a working machine with or without a human operator.
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| 43. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
-
Low-Level Control of Hybrid Hydromechanical Transmissions for Heavy Mobile Working Machines
- 2019
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:9
-
Tidskriftsartikel (refereegranskat)abstract
- Fuel efficiency has become an increasingly important property of heavy mobile working machines. As a result, Hybrid Hydromechanical Transmissions (HMTs) are often considered for the propulsion of these vehicles. The introduction of hybrid HMTs does, however, come with a number of control-related challenges. To date, a great focus in the literature has been on high-level control aspects, concerning optimal utilization of the energy storage medium. In contrast, the main topic of this article is low-level control, with the focus on dynamic response and the ability to realize requested power flows accurately. A static decoupled Multiple-Input-Multiple-Output (MIMO) control strategy, based on a linear model of a general hybrid HMT, is proposed. The strategy is compared to a baseline approach in Hardware-In-the-Loop (HWIL) simulations of a reference wheel loader for two drive cycles. It was found that an important benefit of the decoupled control approach is that the static error caused by the system’s cross-couplings is minimized without introducing integrating elements. This feature, combined with the strategy’s general nature, motivates its use for multiple-mode transmissions in which the transmission configuration changes between the modes.
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| 44. |
- Larsson, Viktor, 1990-, et al.
(författare)
-
Hardware-In-the-Loop Simulation of Hybrid Hydromechanical Transmissions
- 2020
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Increased demands on fuel-efficient propulsion motivate the use of complex hybrid hydromechanical transmissions in heavy construction machines. These transmissions offer attractive fuel savings but come with an increased level of complexity and dependency on computer-based control. This trend has increased the use of computer-based simulations as a cost-effective alternative to hardware prototyping when developing and testing control strategies. Hardware-In-the-Loop (HWIL) simulations that combine physical and virtual model representations of a system may be considered an attractive compromise that combine the benefits of these two concepts. This paper explores how HWIL simulations may be used to evaluate powertrain control strategies for hybrid hydromechanical transmissions. Factors such as hardware/software partitioning and causality are discussed and applied to a test rig used for HWIL simulations of an example transmission. The results show the benefit of using HWIL simulations in favour of pure offline simulations and prototyping and stress the importance of accurate control with high bandwidth in the HWIL interface.
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| 45. |
-
Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden
- 2017
-
Proceedings (redaktörskap) (refereegranskat)abstract
- SICFP2017This is the proceedings of the 15th Scandinavian International Conference on Fluid Power held at Linköping University in Sweden on 7-9 June 2017. The theme of the conference was “Fluid Power in the Digital Age”. The contributions are well aligned with this theme, and are indeed reflecting the great developments. We are very grateful to the effort put in by the authors to produce such high quality papers, and also to those taking time to review papers to further enhance the quality. The contributions clearly shows that the fluid power industry, and academia, have both challenges as well as opportunities in keeping up with the evolving capabilities provided by the digitalization. It was with great joy to see old and new colleagues and friends attending our conference and the division of Fluid and mechatronic systems, at Linköping University. The conference is a bi-annual event, with alternating localization between Linköping in Sweden and Tampere in Finland. The process of hosting such an event is a great effort for our organization and I would like to thank all those involved in organizing this conference, and wish good luck with the next one to our Finnish colleagues. Thank you!Prof. Petter KrusHead of DivisionFluid and Mechatronic SystemsReview ProcessEach author attending the conference days had the opportunity to select from three different ways of presenting their contribution. Firstly, a reviewed process with at least two international reviewers of each contribution. The process resulted in most cases with feedback from the reviewers with comments spanning everything between diagram legends to scientific methods. Some proposed papers where rejected upon recommendations from reviewers. Secondly contributions where also presented in industry sessions where the review process where internal only by the staff of the division. A third extended abstract presentation format where also presented during the conference.This proceedings contain all presented contributions from the reviewed papers in the first section and thereafter the non-reviewed papers in second section. All reviewed papers are marked in the footer by the acceptance date.
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| 46. |
- Raduenz, Henrique, 1990-, et al.
(författare)
-
Energy Management Based on Neural Networks for a Hydraulic Hybrid Wheel Loader
- 2020
-
Ingår i: 2020 IEEE Global Fluid Power Society PhD Symposium. - 9781728141381
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a method to derive optimized energy management strategies for a hydraulic hybrid wheel loader. Energy efficiency is a key aspect for the sustainability of off-road mobile machines. Energy management strategies for on-road hybrid vehicles cannot be directly applied to off-road hybrid machines. One significant reason is that there are added degrees of freedom with respect to how power can be recovered, exchanged and reused in the different functions, such as drivetrain or work functions. This results in more complex energy management strategies being derived. This paper presents an analysis and preliminary conclusions for a proposed method to derive optimised online energy management strategies for a hydraulic hybrid wheel loader. Dynamic programming is used to obtain optimal offline energy management strategies for a series of drive cycles. The results are used as examples to train a neural network. The trained neural network then implements the energy management strategy and is used to make optimised control decisions. Through simulation, the neural network’s ability to learn the dynamic programming decision-making process is shown, resulting in the machine operating with fuel consumption similar to that of the offline optimal energy management strategy. Aspects of simplicity to model these machines for dynamic programming optimisation, the data necessary to train the network, the training process, variables used to learn the dynamic programming decision-making process and the robustness of the network when facing unseen operational conditions are discussed. The paper demonstrates the simplicity of the method for taking into account variables that affect the control decisions, therefore achieving optimised solutions.
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| 47. |
- Raduenz, Henrique, et al.
(författare)
-
Energy Management Based on Neural Networks for a Hydraulic Hybrid Wheel Loader
- 2022
-
Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 23:3, s. 411-432
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method to derive optimised energy management strate-gies for a hydraulic hybrid wheel loader. Energy efficiency is a key aspect for the sustainability of off-road mobile machines. Energy management strategies for on-road hybrid vehicles cannot be directly applied to off-road hybrid machines. One significant reason is that there are added degrees of freedom with respect to how power can be recovered, exchanged and reused in the different functions, such as drivetrain or work functions. This results in more complex energy management strategies being derived. This paper presents an analysis and preliminary conclusions for a proposed method to derive optimised online energy management strategies for a hydraulic hybrid wheel loader. Dynamic programming is used to obtain optimal offline energy management strategies for a series of drive cycles. The results are used as examples to train a neural network. The trained neural network then implements the energy management strategy and is used to make optimised control decisions. Through simulation, the neural networks ability to learn the dynamic programming decision-making process is shown, resulting in the machine operating with fuel consumption similar to that of the offline optimal energy management strategy. Aspects of simplicity to model these machines for dynamic programming optimisation, the data necessary to train the network, the training process, variables used to learn the dynamic pro-gramming decision-making process and the robustness of the network when facing unseen operational conditions are discussed. The paper demonstrates the simplicity of the method for taking into account variables that affect the control decisions, therefore achieving optimised solutions.
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| 48. |
- Raduenz, Henrique, et al.
(författare)
-
Extended Analysis of a Valve-Controlled System with Multi-Chamber Actuator
- 2022
-
Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 23:1, s. 79-108
-
Tidskriftsartikel (refereegranskat)abstract
- This paper outlines an extended analysis on how multi-chamber actuators can improve the efficiency of valve-controlled systems. Resistive control is a major source of energy losses in valve-controlled systems that share the same pump to drive multiple loads. By combining different chambers, the load on multi-chamber actuators can be transformed into different pressure and flow rate levels. This allows the adaptation of its load to the loads on other actuators. This can lead to a reduction of resistive control energy losses that occur between pump and actuators when driven simultaneously. As a case study to highlight how the system efficiency can be improved, a load sensing system with a conventional and a multi-chamber actuator is analysed. The equations that describe the system steady state behaviour are presented to evaluate the effect of the load transformations on the system efficiency. A disadvantage of such architecture is the fact that load transformations result in different actuator speeds. To reduce this effect, a compensation factor for the command signal to the proportional valve is presented. The highlight from this paper is the potential for efficiency improvement enabled by the adoption of multi-chamber actuators in a valve-controlled architecture. Further research is required for the selection of number of chambers and their areas since they directly affect the system efficiency.
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| 49. |
- Raduenz, Henrique, 1990-, et al.
(författare)
-
Improving the efficiency of valve-controlled systems by using multi-chamber actuators
- 2021
-
Ingår i: Proceedings of the 17:th Scandinavian International Conference on Fluid Power, SICFP’21, June 1-2, 2021, Linköping, Sweden. - : Linköping University Electronic Press. - 9789179290139 ; , s. 224-236
-
Konferensbidrag (refereegranskat)abstract
- This paper outlines how multi-chamber actuatorscan improve the efficiency of valve-controlled systems.Resistive control is a major source of energy losses invalve-controlled systemsthat share the same pumpto drive multiple loads. In the proposed concept, by selectingdifferent chambers,the load on the multi-chamber actuator can be transformed into different pressure and flow rate levels, allowingthe adaptation of its load to the loads on otheractuators. Thiscan lead to a reduction of resistive control energy losses that occur between pump and actuatorswhen driven simultaneously.Suchsystemsareseen as an intermediate solution between resistive conventionalhydraulics and throttle-less digital hydraulics. As a casestudyto highlight the possible efficiency improvement, a concept of a load sensing system with a conventional and a multi-chamber actuatoris analysed. To determine itsefficiency,the equations that describe its static behaviour are presented. Evaluating them for a set ofload forces and speeds demonstrates how the load transformation occursand how it canimprove efficiency.
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| 50. |
- Raduenz, Henrique, et al.
(författare)
-
Multi-Chamber Actuator Mode Selection through Reinforcement Learning-Simulations and Experiments
- 2022
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:14
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the development and implementation of a reinforcement learning agent as the mode selector for a multi-chamber actuator in a load-sensing architecture. The agent selects the mode of the actuator to minimise system energy losses. The agent was trained in a simulated environment and afterwards deployed to the real system. Simulation results indicated the capability of the agent to reduce energy consumption, while maintaining the actuation performance. Experimental results showed the capability of the agent to learn via simulation and to control the real system.
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