Linköping Electronic Conference Proceedings
Not a member yet
1113 research outputs found
Sort by
The Fundamental Modeling Practices and Specifications to support the Preservation and Reuse of Analytical Simulations
Full text linkSignificant opportunities exist to preserve and reusesimulation and analytical models and data. Based on thecapabilities developed by the Modelica Association (MA),LOTAR International (Lotar), and other contributing tooldevelopers, multiple engineering and manufacturingindustries can compile extensive archives of reusable andinteroperable performance, behavior and integrated productinformation. Through the development and implementation ofa preservation plan, the use of compliant off-the shelfsoftware applications, and packaging using compatible datastandards, a repository of analytical interactions,simulations and functional prototypes can be archived,maintained, and resourced by future users. This paperidentifies progress made since the publication of (Coïc2021, Coïc 2023) with respect to maturity of the LOTARdraft standards – ASD-STAN 9300 series, (ASD-STAN, 2025)and accompanying prototype implementations. There has alsobeen significant progress on the side of ModelicaAssociation relevant standards with the standardization oflayered standards in FMI and SSP (Modelica Association2024-11., Modelica Association 2024-12), and new versionsof both standards. The soon to be released layered standardSSP Traceability (Modelica Association 2025-04) providesmechanisms to document and preserve relevant metadata formodel archiving – Long Term Archiving and Retrieval(LOTAR). The FMI layered standard FMI-LS-Ref standardizesparameter sets and reference results, which are animportant subset of the required LOTAR Internationalarchiving data
Modeling and Simulation of a Direct Heat Recovery System for Cabin Heating in Battery-Powered Mobile Machines
Full text linkThe transition from internal combustion engines toalternative technologies—such as battery-electricpowertrains—in mobile machinery places increased demands onthermal management systems. Cooling requirements below theambient temperature during the summer, and intensiveheating requirements during the winter, lead to holisticbut complex integrated solutions where energy efficiency isof high priority. Research into integrated system solutionsincluding heat pumps and waste-heat recovery has beencarried out mainly on passenger cars. In this study, mobilemachines are considered, and an articulatedexcavator-loader—also known as backhoe loader—is used as anexample. Apart from operating tasks, times, and conditions,the system architecture under the hood differs fromarchitectures usually found in passenger cars, includingworking hydraulic systems. During the early stages ofvehicle development, modeling and simulation of integratedthermal management systems are crucial forproof-of-concept, developing control strategies, andunderstanding subsystem interactions. These processes relyon data that would otherwise require testing on a completevehicle. This paper presents a model of a heat recoverysystem for cabin heating using the DLR Thermofluid StreamModelica library, together with input data from previousresearch based on experiments on a series-hybrid electricmachine. The study investigates the initial feasibility andperformance of a direct heat recovery system for thearchitecture of a battery-powered mobile machine. Theresults show that a simple system design can provide astrong foundation for cabin heating under many of thestudied excavating conditions, though it does not fullymatch the performance of the reference system, which issupplied with heat from an internal combustion engine
Requirement Verification with CRML and OpenModelica
Full text linkCommon Requirement Modeling Language (CRML) is alanguage designed to express requirements in an intuitivemanner, in this paper we present the recent advancementsin tool support for the requirement modeling and verifica-tion workflow in OpenModelica and illustrate this on theTraffic Light use-case
Context-Aware Mission Planning and Decentralized Execution for Heterogeneous Teammates in Dynamic Environments
Full text linkThis paper presents a novel concept for a context-aware framework for mission planning anddecentralized execution that integrates heterogeneous teammates such as autonomous drones,agents, and human responders into a unified, resilient system for dynamic operational scen-arios. At the operational level, the system utilizes a Mission Planning function that receiveshigh-level objectives, interprets mission intent, and decomposes complex objectives into a seriesof clear, actionable Mission-Essential tasks and sub-tasks. The process leverages contextual in-formation from various sources such as sensor feeds, human reports and operational databasesto dynamically assess resource availability and execution timing, while also considering opera-tional constraints, including ethical constraints, and cost considerations. The system orchestratesa two-tier command structure, where the first level ensures that subordinates possess a robustunderstanding of mission objectives and the autonomy to adapt to changes in its operational en-vironment. The second level comprises of diverse agents with varying levels of autonomy andcapabilities, enabling iterative adaptation and collaboration. Experiments will be conducted indynamic scenarios, such as deploying diverse drone platforms for Intelligence, Surveillance andReconnaissance, and Search and Rescue missions to validate the framework’s feasibility. Thisresearch aims to develop context-awareness for system adaptation to its operational environmentwith a safety-monitoring function to enhance the safety, adaptability, and efficiency of coordin-ated drone-human teams in operational applications
Numerical investigation of dynamic stall on wings following curved trajectory
Full text linkUnsteady aerodynamic flows play a pivotal role in both engineering applications and natural phenomena, with dynamic stall representing a particularly critical challenge. This phenomenon not only degrades aerodynamic efficiency but also induces unsteady loads and aeroelastic responses that can compromise structural integrity. However, the evolution of dynamic stall under complex kinematics remains inadequately understood. This study aims to advance the understanding of dynamic stall mechanisms and to develop computationally efficient models that retain essential nonlinear flow features. We first employ high-fidelity direct numerical simulations (DNS) using the spectral element solver Nek5000 to study a wing undergoing circular motion at the reduced frequencies k = 0.6, representing light stall conditions. Modal analysis, such as proper orthogonal decomposition, was applied to the spanwise vorticity field to better understand the evolution of the dynamic stall vortex and the corresponding flow structures. Despite the accuracy of DNS, its high computational cost limits its practical application and the feasibility to study the far wake. Thus, the second part of this study explores a reduced-order modelling approach using an advanced actuator line model to investigate dynamic stall on a plunging wing. While conventional actuator line models have inherent limitations in capturing unsteady phenomena, we incorporate force coefficients extracted from DNS results to reconstruct the flow fields within the actuator line model to bridge this gap. The spectrum of the induced velocity is compared with analytical results from a novel linear theory for unsteady aerodynamics in actuator line method (Alva et al. 2025). The results demonstrate that the advanced actuator line method is capable of capturing parts of the unsteady effect from dynamic stall and the near wake. This highlights the potential to model dynamic stall using the actuator line method and underscores the feasibility of integrating a dynamic stall model and wake study within this approach
Combining Equation-based and Multibody Models
Full text linkThis article highlights the combination of equationbased modeling with multibody models. In other words, it combines the equation-based modeling language Modia and the multibody module Modia3D. The multibody system is defined in an object-oriented way and parts of it are defined by equations. Algebraic loops are treated that appear due to the connection of multibody and equation-based components. A new approach to variable structure systems are socalled predefined acausal components which consist of pre-compiled causal parts and acausal equations. To generalize the concepts for variable structure systems, the multibody module is defined as a predefined acausal component. As a result, the number of degrees of freedom of the multibody system can vary during simulation. This is demonstrated with a non-trivial example of a walking space robot from the MOSAR space project
Aerothermal performance of an open source methane-fueled rocket engine
Full text linkThis study investigates the feasibility of integrating all relevant physics into a single simulation of a rocket engine nozzle, including the supercritical coolant, the supersonic reacting flame, along with the heat transfer between them. Traditionally, multiple simulations coupled with a thermal boundary condition would be utilized, which is time-consuming as it requires manually iterating between the simulations. A holistic simulation approach within one simulation was therefore developed. By comparing two CFD codes, STAR-CCM+ and Fluent, their suitability for this holistic simulation approach was evaluated based on accuracy, time consumption, and the required amount of manual input needed to complete a holistic simulation.
The methodology involved setting up comprehensive models in both CFD codes, ensuring that all relevant physical phenomena were accurately represented. The simulations were run under identical conditions to ensure a fair comparison. The results indicated that both codes produced outputs consistent with previous studies and with each other, validating the holistic approach. However, STAR-CCM+ demonstrated greater efficiency, making it more suitable for practical applications.
These findings suggest that a single, integrated simulation approach can significantly streamline the design and analysis process for rocket engine nozzles, potentially leading to more efficient and cost-effective development cycles
Amplitude and Phase Imbalance Calibration for Space-Based Precision Direction Finding System
Full text linkModern space systems rely heavily on the Radio Frequency Direction Finder (RF DF) for various
applications, where multichannel receivers are used to determine signal arrival angles. Accurate
angle estimation requires precise front-end and signal processing. However, high-frequency elec
tronics are susceptible to variations in electronic components due to manufacturing processes,
temperature fluctuations, and voltage fluctuations, leading to errors. To mitigate these errors,
amplitude and phase calibration of the multichannel front-end are crucial. This work presents
and implements, using a Software Defined Radio (SDR), a simplified calibration technique for a
dual-channel X-band RF front-end designed for space-based DF. The method involves applying a
calibration signal to the front-end and measuring the amplitude and phase errors in the baseband
signals using an SDR system. These measurements are used to create an error vector that is then
applied in the software domain to compensate for system imbalances. Experimental validation
was conducted within the 8.5 to 9.5 GHz X-band range, employing a modular dual-channel RF
front-end connected to a dual-channel SDR, considering two scenarios of calibration in the soft
ware domain for the entire bandwidth
Quality Control of Carbon Fiber Structures by Acoustic Method
Full text linkA method for quality control, using impact excitation and sound measurements, is investigated.
The Eigenmodes of a structure are unique if all properties, i.e. the shape, the resonance frequency, and the damping, are considered. It is, however, demanding to experimentally determine the vibration shape of the Eigenmodes, compared to getting estimates of the Eigenfrequency and the Damping.
For a specific structure it may, however, be possible to use identified peaks in a measured sound spectrum, and from them make estimates of the Eigenfrequencies and Damping, establishing enough information for quality control, even without knowing the mode shapes. The risk associated with this approach is if a match of peaks in the response spectra is found in terms of frequency and damping, but this match is in fact for different Eigenmodes (i.e. the correlation in frequency and damping is for Eigenmodes with different shapes). This may happen for one pair of Eigenmodes, but is unlikely if more Eigenfrequencies are included in the comparison.
Another risk with the used approach is if the acoustic radiation is poor from one or more of the Structural Eigenmodes, or if the excitation is sensitive to the impact (excitation) location. Further, with a single microphone used, there is a risk the sound radiation in this particular direction is low. The strategy to reduce such risks is to used multiple impact locations, and to use a non-fixed test rig for the test object.
Demonstration of the method’s applicability is made using aircraft components manufactured in Carbon Fiber Reinforced Polymer, and show promising results in terms of ability to detect variations in manufacturing quality, with a very simple test setup and short time required for the test
Fluid Property Functions in Polar and Parabolic Coordinates
Full text linkThis paper presents two methods for reallizing fluid property functions in Modelica simulation models. Each makes use of a coordinate transformation that aligns one coordinate with the saturation curve. This provides for a precise representation of the fluid property function at the saturation curve, and for connected domains of interest including the liquid, vapor, supercritical and two-phase regions. Both approaches make use of spline function approximation in the aligned coordinates, and are numerically efficient, well conditioned, and allow for efficient calculation of derivatives up to any desired order that are precise up to processor numerical tolerance