| 1. |
- Amadori, Kristian, 1976-, et al.
(författare)
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Aircraft Conceptual Design Optimization
- 2008
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Ingår i: International Congress of the Aeronautical Sciences ICAS,2008. - Stockholm, Sweden : ICAS.
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Konferensbidrag (refereegranskat)abstract
- Aircraft design is an inherently multidisciplinary activity that requires different models and tools for various aspects of the design. At Linköping University a novel design framework is being developed to support the initial conceptual design phase of new aircraft. By linking together various modules via a userfriendly spreadsheet interface, the framework allows multidisciplinary analysis and optimizations to be carried out. The geometrical model created with a high-end CAD system, contains all the available information on the product and thus it plays a central role in the framework. In this work great attention has been paid to techniques that allow creating robust yet highly flexible CAD models. Two different case studies are presented. The first one is a hypothetic wing-box design that is studied with respect to aerodynamic efficiency and loads, and to structural analysis. In this study two approaches were compared. In one case the wing-box design was optimized with a fixed number of structural elements, where only dimensions and position were allowed to change. Then the same wing-box was analyzed allowing also the number of structural elements to vary. Thus only the parts that are required are left and a more efficient design can be obtained. In the second case study a mission simulation is performed on a UAV-type aircraft. Required data for the simulation are gathered from the CAD model and from aerodynamic analysis carried out with PANAIR, a high order panel code. The obtained data are then used as inputs parameters for flight simulation in order to determined hydraulic systems characteristics.
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| 2. |
- Amadori, Kristian, 1976-, et al.
(författare)
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Using CAD-Tools and Aerodynamic Codes in a Distributed Conceptual Design Framework
- 2007
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Ingår i: Aerospace Sciences Meeting and Exhibit,2007. - USA : AIAA.
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Konferensbidrag (refereegranskat)abstract
- Aircraft design is an inherently multi-disciplinary activity that requires different models and tools for various aspects of the design. At Linköping University a novel design framework is being developed to support the initial conceptual design phase of a new aircraft. Different modules are included, each one addressed to analyze and evaluate different aspects of the airplane, such as its aerodynamics, its weight and structure, its sub systems and its performances. All modules are easily accessible from a user-friendly interface based on an Excel spreadsheet. The link between all modules is based on Service Oriented Architecture (SOA) and allows both distribution and integration of all functions. This paper will present the framework, give an overview of its development status and give an indication on the future work.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Axin, Mikael, 1984-, et al.
(författare)
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A Flexible Working Hydraulic System for Mobile Machines
- 2016
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Ingår i: International Journal of Fluid Power. - : Taylor & Francis. - 1439-9776 .- 2332-1180. ; 17:2, s. 79-89
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper proposes a novel working hydraulic system architecture for mobile machines. Load sensing, flow control and open-centre are merged into a generalized system description. The proposed system is configurable and the operator can realize the characteristics of any of the standard systems without compromising energy efficiency. This can be done non-discretely on-the-fly. One electrically controlled variable displacement pump supplies the system and conventional closed-centre spool valves are used. The pump control strategies are explained in detail. Experimental results demonstrate one solution to the flow matching problem and the static and dynamic differences between different control modes.
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| 7. |
- Axin, Mikael, 1984-, et al.
(författare)
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A Hybrid of Pressure and Flow Control in Mobile Hydraulic Systems
- 2014
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Ingår i: 9th InternationalFluid Power Conference (IFK). Vol. 1. Aachen, Germany, 24-26 March 2014. - 9783981648003 ; , s. 190-201
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Konferensbidrag (refereegranskat)abstract
- This paper presents a hybrid pump controller approach for mobile hydraulic systems, influenced by both pressure and flow. The controller is tuneable to be able to set the order of importance of the pressure and flow controller, respectively. It is thus possible to realize a load sensing system, a flow control system or a mix of the two. Using a low load pressure feedback gain and a high flow control gain, a system emerges with high energy efficiency, fast system response, high stability margins and no flow matching issues. In this paper, both theoretical studies and practical implementations demonstrate the capability of a hybrid pump control approach.
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| 8. |
- Axin, Mikael, 1984-, et al.
(författare)
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Design Rules for High Damping in Mobile Hydraulic Systems
- 2013
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Ingår i: 13th Scandinavian International Conference on Fluid Power. - : Linköping University Electronic Press. - 9789175195728 ; , s. 13-20
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Konferensbidrag (refereegranskat)abstract
- This paper analyses the damping in pressure compensated closed centre mobile working hydraulic systems. Both rotational and linear loads are covered and the analysis applies to any type of pump controller. Only the outlet orifice in the directional valve will provide damping to a pressure compensated system. Design rules are proposed for how the system should be dimensioned in order to obtain a high damping. The volumes on each side of the load have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension for maximized damping; both smaller and larger orifice areas give lower damping independently of the volumes. This paper presents a method to dimension the outlet orifice area and the load volumes in order to obtain a desired system damping. Experimental results, which confirm the theoretical expectations, are also presented. The conclusions are that it is possible to obtain a high damping contribution from the outlet orifice if the system is dimensioned correctly. However, the energy efficiency needs to be considered while improving the damping
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| 9. |
- Axin, Mikael, 1984-, et al.
(författare)
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Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
- 2011
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Ingår i: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11. - 9789521525193 ; , s. 223-238
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Konferensbidrag (refereegranskat)abstract
- Interest has increased in flow controlled systems in the field of mobile fluid power. The capital distinction between traditional load-sensing (LS) systems and flow controlled systems is that the pump is controlled based on the operator’s total flow demand rather than maintaining a certain pressure margin over the maximum load pressure. One of the main advantages of flow controlled systems is the absence of the feedback of the highest load pressure to the pump controller. In this paper, a dynamic analysis is performed where flow controlled and LS systems are compared. It is shown how instability can occur in LS systems due to the pump controller and proven that no such instability properties are present in flow controlled systems. A drawback with one type of flow controlled system is that the highest load dynamically will disturb the lighter loads. This paper shows a novel way to optimize the damping in such systems by controlling the opening position of the directional valve independently of the flow. The mentioned disturbance between the highest load to the others can thereby be reduced.
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| 10. |
- Axin, Mikael, 1984-, et al.
(författare)
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Energy Efficient Fluid Power System for Mobile Machines with Open-centre Characteristics
- 2014
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Ingår i: 9th JFPS International Symposium on Fluid Power. Matsue, Japan, 28-31 October 2014. - : The Japan Fluid Power System Society. - 4931070108 ; , s. 452-459
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a flexible and energy efficient system solution which mimics the behaviour of an open-centre system. An electro-hydraulic variable displacement pump and closed-centre valves are used. Instead of having a flow in the open-centre gallery, that flow is calculated using a pressure sensor and a valve model. The variable pump is then controlled in order to only deliver the flow that would go to the actual loads. It is also possible for the operator to decide how much load dependency there should be. The extreme case is not having any load dependency at all, resulting in a system where the pump displacement setting is controlled according to the sum of all requested load flows. It is thus possible to realize a system design with open-centre characteristics, a flow control system or something in between. Each operator can thereby get their optimal control characteristic while having high energy efficiency.
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| 11. |
- Axin, Mikael, 1984-, et al.
(författare)
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Flow versus pressure control of pumps in mobile hydraulic systems
- 2014
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Ingår i: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering. - : Sage Publications. - 0959-6518 .- 2041-3041. ; 228:4, s. 245-256
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Tidskriftsartikel (refereegranskat)abstract
- This work studies an innovative working hydraulic system design for mobile applications, referred to as flow control. The fundamental difference compared to load-sensing systems is that the pump is controlled based on the operator’s command signals rather than feedback signals from the loads. This control approach enables higher energy efficiency since the pressure difference between pump and load is given by the system resistance rather than a prescribed pump pressure margin. Furthermore, load-sensing systems suffer from poor dynamic characteristics since the pump is operated in a closed-loop control mode. This might result in an oscillatory behaviour. Flow control systems have no stability issues attached to the load pressure feedback since there is none. This allows the pump to be designed to meet the response requirements without considering system stability. Pressure compensators are key components in flow control systems. This study addresses the flow matching problem which occurs when using traditional compensators in combination with a flow-controlled pump. Flow sharing pressure compensators solve this problem since the pump flow will be distributed between all active functions. Simulation results and measurements on a wheel loader application demonstrate the energy-saving potentials and the dynamic improvements for the flow control system.
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| 12. |
- Axin, Mikael, 1984-, et al.
(författare)
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Next Generation Simulation Software using Transmission Line Elements
- 2010
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Ingår i: Fluid Power and Motion Control. - : Centre for Power Transmission and Motion Control. - 9781861971814 ; , s. 265-276
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Konferensbidrag (refereegranskat)abstract
- A suitable method for simulating large complex dynamic systems is represented by distributed modelling using transmission line elements. The method is applicable to all physical systems, such as mechanical, electrical and pneumatics, but is particularly well suited to simulate systems where wave propagation is an important issue, for instance hydraulic systems. By using this method, components can be numerically isolated from each other, which provide highly robust numerical properties. It also enables the use of multi-core architecture since a system model can be composed by distributed simulations of subsystems on different processor cores.Technologies based on transmission lines has successfully been implemented in the HOPSAN simulation package, develop at Linköping University. Currently, the next generation of HOPSAN is developed using an object-oriented approach. The work is focused on compatibility, execution speed and real-time simulation in order to facilitate hardware-in-the-loop applications. This paper presents the work progress and some possible features in the new version of the HOPSAN simulation package.
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| 13. |
- Axin, Mikael, 1984-, et al.
(författare)
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Optimized Damping in Cylinder Drives Using the Meter-out Orifice : Design and Experimental Verification
- 2012
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Ingår i: 8th International Fluid Power Conference Dresden. ; , s. 579-591
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper analyses the damping of a flow controlled cylinder with a mass load and an outlet orifice. By using linear models, a mathematical expression for the damping is derived. It is shown that the volumes on each side of the piston have a high impact on the damping. In case of a small volume on the inlet side, the damping becomes low. However, the most important thing is to design the outlet orifice area properly. There exists an optimal orifice dimension; both smaller and larger orifice areas give low damping independently of the size of the volumes. In this paper a design is proposed of the outlet orifice area that optimizes the damping of the system. Experimental results which confirm the theoretical expectations are also presented. The conclusions are that without an outlet orifice, the hydraulic system will not contribute with any damping at all. Furthermore, large dead volumes in the cylinder will increase the damping, but at the expense of the system’s efficiency.
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| 14. |
- 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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| 15. |
- Baer, Katharina, 1984-, et al.
(författare)
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Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle
- 2019
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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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| 16. |
- Baer, Katharina, 1984-, et al.
(författare)
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Robustness and performance evaluations for simulation-based control and component parameter optimization for a series hydraulic hybrid vehicle
- 2020
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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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| 17. |
- 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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| 18. |
- 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
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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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| 19. |
- Eriksson, Björn, 1981-, et al.
(författare)
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Hopsan NG, A C++ Implementation using the TLM Simulation Technique
- 2010
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Ingår i: SIMS 2010 Proceedings, The 51st Conference on Simulation and Modelling, 14-15 October 2010 Oulu, Finland. - Oulu, Finland. - 9789525183429
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Konferensbidrag (refereegranskat)abstract
- The Hopsan simulation package, used primarily for hydro-mechanical simulation, was first released in 1977. Modeling in Hopsan is based on a method using transmission line modeling, TLM. In TLM, component models are decoupled from each other through time delays. As components are decoupled and use distributed solvers, the simulation environment is suitable for distributed simulations. No numerical errors are introduced at simulation time when using TLM; all errors are related to modeling errors. This yields robust and fast simulations where the size of the time step does not have to be adjusted to achieve a numerically stable simulation. The distributive nature of TLM makes it convenient for use in multi-core approaches and high speed simulations. The latest version of Hopsan was released in August 2002, but now the next generation of this simulation package is being developed. This paper presents the development version of Hopsan NG and discusses some of its features and possible uses.
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| 20. |
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| 21. |
- Gunnarsson, Svante, 1959-, et al.
(författare)
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Fluid Power Control of a Flexible Mechanical Structure
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Control of a hydraulic crane is considered. Due to the oscillatory character of the system smooth the operation of the crane is a demanding task. In order to improve the handling properties feedback control of the crane is studied. Based on linearized models feedback regulators of both LQG and PID type are designed. The feedback is based on position, pressure and acceleration measurements. Since the properties of the system change with load and operating point adaptive control is also introduced. The use of accelerometer signals for impact detection is also discussed. The proposed solutions are tested in both simulations and experiments on a real crane.
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| 22. |
- Gunnarsson, Svante, 1959-, et al.
(författare)
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LQG Control of a Hydraulic Actuator with a Flexible Mechanical Load
- 1993
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Ingår i: Proceedings of the 12th IFAC World Congress. - Linköping : Linköping University. - 9780080422121 ; , s. 469-472
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a control system based on linear quadratic state feedback and state estimation for an hydraulic actuator with a flexible mechanical load. The purpose of the control system is to improve the dynamic properties by reducing the oscillatory behavior of the load and to eliminate the steady state error in the load position caused by external disturbances. Using a simplified linear model a control system is developed and evaluated using simulations and experiments.
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| 23. |
- Hallberg, Peter, 1974-, et al.
(författare)
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Low Cost Demonstrator As A Mean For Rapid Product Realization With An Electric Motorcycle Application
- 2005
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Ingår i: 2005 ASME International Design Engineering Technical Conferences Computers and Information In Engineering Conference - 31st Design Automation Conference, 2005. - 079184739X
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the last decade, digital prototyping has become a natural part of any industrial project dealing with product development. The reasons for this differ, but the two most obvious is time saving aspects and the amount of cost effectiveness achieved when replacing the physical prototype with the cheaper digital. Time and cost are equally, or even more critical in academic projects. This paper describes the usage of a low cost demonstrator as a mean to reduce both time and cost during a product development project course as well as to guarantee educational quality. The paper also discusses the reason for using demonstrators in an industrial environment. When large product development project courses are given at educational engineering programs, they often strive for imitating a real industrial situation, trying to include all the phases and aspects of product realization. Time is of course critical in both environments, industrial and academic, but for slightly different reasons. A typical industrial project may run over several years while a large educational project-s duration is counted in months. Thus, if the course tutor wants to simulate the whole product development process, within the same project course, there are needs for means that may speed up the project without spoiling the educational message as well as the industrial authenticity.
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| 24. |
- Hallberg, Peter, 1974-, et al.
(författare)
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Modular sustainable light multi-purpose vehicle
- 2008
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Ingår i: EET-2008 European Ele-Drive Conference,2008.
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Konferensbidrag (refereegranskat)abstract
- In contrast to the major vicissitude faced by the transportation sector in developed countries due to environmental or political reasons, this contribution mainly fits into the discussion on how to make emerging markets adopt sustainable personal vehicles other than automobiles. A modularised light electric vehicle transportation system is presented.Furthermore, the vehicles included in the presented system would also hold properties suited for transportation needs in developed countries. One issue would be not only a smaller environmental footprint, but also a more attractive physical footprint, in the sense that actual space is a matter of economy in densely urbanised areas.
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| 25. |
- Hallberg, Peter, 1974-, et al.
(författare)
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Redsigning Mature Products for Substainability
- 2006
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This contribution will discuss engineering design projects with various environmental and sustainable objectives. The automotive industry is facing a major vicissitude regarding the system layouts of their products. Given the rapidly increasing demands for environmentally acceptable and sustainable vehicles, developed even faster and under increasing competition, one could expect a future, or a period of transition, where a “market pull”-situation will exact design methods more adapted for new propulsion technologies such as fuel cells, bio-fuels, hybrid configurations and so forth. When looking at two-wheeled vehicles it is also a matter of a dramatic change in the safety requirements that would affect the design process in a similar way.This paper presents studies made regarding development of two-wheeled vehicles with strict safety, environmental and sustainability requirements. It also describes what happens when a very mature product, such as a conventional motorcycle, undergoes dramatic changes in propulsion system and safety features and becomes technically immature, but still has to preserve its traditional values in the eyes of the consumer. Over the last two years, the Department of Mechanical Engineering at Linköping University has conducted various projects dealing with these issues using rapid, low-cost, demonstrator development together with digital models. The demonstrator is used as a vehicle to evaluate the integration of technology, as well as less tangible aspects such as ergonomics, drivability, appeal, visual impression etc. This approach has proven particularly fruitful when dealing with new technologies with a high level of innovation. The rapid nature of these projects also makes them suitable for exploring digital collaboration tools aimed at controlling and speeding up the design process.
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| 26. |
- Heybroek, Kim, 1981-
(författare)
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On Energy Efficient Mobile Hydraulic Systems : with Focus on Linear Actuation
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this dissertation, energy efficient hydraulic systems are studied. The research focuses on solutions for linear actuators in mobile applications, with emphasis on construction machines. Alongside the aspect of energy efficiency, the thesis deals with competing aspects in hydraulic system design found in the development of construction machines. Simulation models and controls for different concepts are developed, taking the whole machine into account. In line with this work, several proof of concept demonstrators are developed.First, pump controlled systems are studied and a novel concept based on an open-circuit pump configuration is conceived. Special consideration is paid to multi-mode capabilities that allow for a broadened operating range and potential downsizing of components. Simulation models and controls are developed and the system is experimentally validated in a wheel loader application.Second, the possibility for energy recuperation in valve controlled systems is investigated. In such solutions, a hydraulic motor, added to the meter-out port, is used for energy recovery during load lowering and in multi-function operation. Recuperated energy is either be used momentarily or is stored in a hydraulic accumulator. The proposed solution means an incremental improvement to conventional systems, which is sometimes attractive to machine manufacturers due to fewer uncertainties in reliability, safety and development cost. The energy recovery system is studied on a conceptual level where several alternative systems are proposed and a concept based on a two-machine hydraulic pressure transformer is selected for a deeper control study followed by experimental validation.Third, so-called `common pressure rail' systems are suggested. This technique is well established for rotary drives, at least for the industrial sector. However, in applying this technique to mobile hydraulics, feasible solutions for linear actuators are needed. In this dissertation, two approaches to this problem are presented. The first one is the hydraulic pressure transformer, studied in simulation as the key-component of a `series hybrid' topology for wheel loaders. In the second approach variable displacement linear actuators (VDLA) based on a 4-chamber cylinder and multi-mode control is applied. In a theoretical study a model predictive control approach is suggested and new insights to the trade-off between controllability and energy efficiency of a multi-chamber cylinder are presented. Finally, a fullscale hydraulic hybrid system based on secondary controlled hydraulic motors and VDLAs is designed and experimentally validated on a large excavator.
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| 27. |
- Hochwallner, Martin, 1976-, et al.
(författare)
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Hydraulic Infinite Linear Actuator : The Ballistic Gait Digital Hydro-Mechanical Motion
- 2017
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Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden DOI: https://doi.org/10.3384/ecp17144. - Linköping : Linköping University Electronic Press. - 9789176853696 ; , s. 10-17
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Konferensbidrag (refereegranskat)abstract
- The Hydraulic Infinite Linear Actuator, HILA, has been presented in previous publications. The novel actuator consists of one, two or more double-acting cylinders witha common piston rod and hydraulically detachable pistons. In the basic gait, one cylinderalternatingly engages and drives the load while the other retracts. The HILA thus works in akind of rope-climbing motion. The concept also allows other gaits, i.e. patterns of motion.This contribution focuses on the ballistic gait, a pattern of motion where one cylinder engagesto give the load a push. The load then carries on with its motion by inertia, cylinders disen-gaged. The actuator thus realizes hydro-mechanical pulse-frequency modulation (PFM).This gait is energy efficient and able to recuperate energy.
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| 28. |
- Hochwallner, Martin, 1976-
(författare)
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On Motion Control of Linear Incremental Hydraulic Actuators
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Linear Incremental Hydraulic Actuators combine one or more short-stroke cylinders, and two or more engaging/disengaging mechanisms into one actuator with long, medium, or even unlimited stroke length. The motion of each single short-stroke actuator concatenated by the engaging/disengaging mechanisms forms the motion of the linear incremental hydraulic actuator.The patterns of how these motions are concatenated form the gaits of a specific linear incremental hydraulic actuator. Linear incremental hydraulic actuators may have more than one gait. In an application, the gaits may be combined to achieve optimal performance at various operating points.The distinguishing characteristic of linear incremental hydraulic actuators is the incremental motion. The term incremental actuator is seen as analogous to the incremental versus absolute position sensor. Incremental actuators realize naturally relative positioning. Incremental motion means also that the behavior does not depend on an absolute position but only on the relative position within a cycle or step.Incremental actuators may realize discrete incremental or continuous incremental motion. Discrete incremental actuators can only approach discrete positions, whereby stepper drives are one prominent example. In contrast, continuous incremental actuators may approach any position. Linear electric motors are one example of continuous incremental actuators. The actuator has no inherent limitation in stroke length, as every step or cycle adds only to the state at the beginning of the step or cycle and does not depend on the absolute position. This led to the alternative working title Hydraulic Infinite Linear Actuator.Linear incremental hydraulic actuator provides long stroke, high force, and linear motion and has the potential todecrease the necessary resource usage,minimize environmental impact, e.g. from potential oil spillage,extend the range of feasible products: longer, stiffer, better, etc.This thesis presents an analysis of the characteristics and properties of linear incremental hydraulic actuators as well as the gaits and possible realizations of some gaits. The gait for continuous, smooth motion with two cylinders is comprehensively studied and a control concept for the tracking problem is proposed. The control concept encapsulates the complexity of the linear incremental hydraulic actuator so that an application does not have to deal with it. One other gait, the ballistic gait, which realizes fast, energy-efficient motion, enabling energy recuperation is studied.
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| 29. |
- Hochwallner, Martin, 1976-, et al.
(författare)
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Tracking Control for High-Performance Motion of a Hydraulic Infinite Linear Actuator
- 2018
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Ingår i: IEEE/ASME transactions on mechatronics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1083-4435 .- 1941-014X. ; 23:6, s. 2782-2793
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Tidskriftsartikel (refereegranskat)abstract
- The concept of the hydraulic infinite linear actuator consists of two double-acting cylinders with hydraulically detachable pistons driving a common rod. Alternatingly, one cylinder engages and drives the load, whereas the other retracts; the actuator, thus, works in a kind of rope-climbing motion. The actuator has three degrees of freedom, which are temporarily coupled compared with one in a conventional cylinder. Hence, the actuator is a hybrid system with both continuous and discrete states and control inputs. This paper presents a tracking control problem and a solution for high-performance motion, which is interpreted as utilizing the hardware limits in the sense of velocity, accuracy, smoothness, and usability. The concept is demonstrated by simulation for the case of a rest-to-rest motion, but the intended use cases also include arbitrary trajectories.
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| 30. |
- Hällqvist, Robert, 1983-, et al.
(författare)
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A Novel FMI and TLM-based Desktop Simulator for Detailed Studies of Thermal Pilot Comfort
- 2018
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Ingår i: ICAS congress proceeding. - : International Council of the Aeronautical Sciences. - 9783932182884
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Modelling and Simulation is key in aircraft system development. This paper presents a novel, multi-purpose, desktop simulator that can be used for detailed studies of the overall performance of coupled sub-systems, preliminary control design, and multidisciplinary optimization. Here, interoperability between industrially relevant tools for model development and simulation is established via the Functional Mockup Interface (FMI) and System Structure and Parametrization (SSP) standards. Robust and distributed simulation is enabled via the Transmission Line element Method (TLM). The advantages of the presented simulator are demonstrated via an industrially relevant use-case where simulations of pilot thermal comfort are coupled to Environmental Control System (ECS) steadystate and transient performance.
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| 31. |
- Hällqvist, Robert, 1983-, et al.
(författare)
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Early Insights on FMI-based Co-Simulation of Aircraft Vehicle Systems
- 2017
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Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden. - Linköping : Linköping University Electronic Press. - 9789176853696 ; , s. 262-270
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Modelling and Simulation is extensively used for aircraft vehicle system development at Saab Aeronautics in Linköping, Sweden. There is an increased desire to simulate interacting sub-systems together in order to reveal, and get an understanding of, the present cross-coupling effects early on in the development cycle of aircraft vehicle systems. The co-simulation methods implemented at Saab require a significant amount of manual effort, resulting in scarcely updated simulation models, and challenges associated with simulation model scalability, etc. The Functional Mock-up Interface (FMI) standard is identified as a possible enabler for efficient and standardized export and co-simulation of simulation models developed in a wide variety of tools. However, the ability to export industrially relevant models in a standardized way is merely the first step in simulating the targeted coupled sub-systems. Selecting a platform for efficient simulation of the system under investigation is the next step. Here, a strategy for adapting coupled Modelica models of aircraft vehicle systems to TLM-based simulation is presented. An industry-grade application example is developed, implementing this strategy, to be used for preliminary investigation and evaluation of a cosimulation framework supporting the Transmission Line element Method (TLM). This application example comprises a prototype of a small-scale aircraft vehicle systems simulator. Examples of aircraft vehicle systems are environmental control systems, fuel systems, and hydraulic systems. The tightly coupled models included in the application example are developed in Dymola, OpenModelica, and Matlab/Simulink. The application example is implemented in the commercial modelling tool Dymola to provide a reference for a TLM-based master simulation tool, supporting both FMI and TLM. The TLM-based master simulation tool TLMSimulator is investigated in terms of model import according to the FMI standard with respect to a specified set of industrial needs and requirements.
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| 32. |
- Hällqvist, Robert, 1983-
(författare)
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On Standardized Model Integration : Automated Validation in Aircraft System Simulation
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Designing modern aircraft is not an easy task. Today, it is not enough to optimize aircraft sub-systems at a sub-system level. Instead, a holistic approach is taken whereby the constituent sub-systems need to be designed for the best joint performance. The State-of-the-Art (SotA) in simulating and exchanging 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 analysing coupled sub-systems in simulators. Furthermore, if aircraft sub-system simulation models are to be utilized to their fullest extent, opensource tooling and the use of open standards, interoperability between domain specific modeling tools, alongside robust and automated processes for model Verification and Validation (V&V) 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 sub-system 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 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, supporting on-line simulator credibility assessment according to the presented proposed method.
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| 33. |
- 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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| 34. |
- Hällqvist, Robert, 1983-, et al.
(författare)
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Optimal Selection of Model Validation Experiments : Guided by Coverage
- 2021
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Ingår i: Journal of Verification, Validation and Uncertainty Quantification. - New York : The American Society of Mechanical Engineers. - 2377-2158 .- 2377-2166. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Modeling and Simulation (M&S) is seen as a means to mitigate the difficulties associated with increased system complexity, integration, and cross-couplings effects encountered during development of aircraft subsystems. As a consequence, knowledge of model validity is necessary for taking robust and justified design decisions. This paper presents a method for using coverage metrics to formulate an optimal model validation strategy. Three fundamentally different and industrially relevant use-cases are presented. The first use-case entails the successive identification of validation settings, and the second considers the simultaneous identification of n validation settings. The latter of these two use-cases is finally expanded to incorporate a secondary model-based objective to the optimization problem in a third use-case. The approach presented is designed to be scalable and generic to models of industrially relevant complexity. As a result, selecting experiments for validation is done objectively with little required manual effort.
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| 35. |
- Hällqvist, Robert, 1983-, et al.
(författare)
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Toward Objective Assessment of Simulation Predictive Capability
- 2023
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Ingår i: Journal of Aerospace Information Systems. - : American Institute of Aeronautics and Astronautics. - 1940-3151. ; 20:3, s. 152-167
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Tidskriftsartikel (refereegranskat)abstract
- Two different metrics quantifying model and simulator predictive capability are formulated and evaluated; both metrics exploit results from conducted validation experiments where simulation results are compared to the corresponding measured quantities. The first metric is inspired by the modified nearest neighbor coverage metric and the second by the Kullback-Liebler divergence. The two different metrics are implemented in Python and in a here-developed general metamodel designed to be applicable for most physics-based simulation models. These two implementations together facilitate both offline and online metric evaluation. Additionally, a connection between the two, here separated, concepts of predictive capability and credibility is established and realized in the metamodel. The two implementations are, finally, evaluated in an aeronautical domain context.
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| 36. |
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| 37. |
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| 38. |
- Johansson, Björn, 1974-, et al.
(författare)
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Distributed aircraft analysis using web service technology
- 2003
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Ingår i: SAE Transactions Journal of Aerospace. - New York : SAE International. - 0096-736X. ; 112:1, s. 445-453, s. 2003-01-3007-
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Tidskriftsartikel (refereegranskat)abstract
- The design of modern aircraft requires the integration of multidisciplinary mouels for analysis in the early design phase to increase the chances of a successful project. In this paper, a framework for distributed aircraft analysis in the conceptual design including several domains is presented. The framework is based on so-called Web Service Standards, allowing integration of distributed models for system simulation and optimization using standardized interfaces. The analysis is controlled by a so-called sequencer which manages the interaction between simulation modules and an XML-based design data repository. This repository includes all design data and an executable process description defining the sequence for execution of the modules. In the paper, the framework with its underlying concepts is described. The approach is further illustrated using thedesign of an Unmanned Aerial Vehicle as an example. This includes the definition of the stimulation modules, the process model, and definition and execution of an optimization problem.
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| 39. |
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| 40. |
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| 41. |
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| 42. |
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| 43. |
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| 44. |
- Jouannet, Christopher, 1974-, et al.
(författare)
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Aerodynamic database of a subscale demonstrator
- 2017
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Ingår i: 35th AIAA Applied Aerodynamics Conference. - Reston, VA, USA : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- This paper reports the current status of a joint Swedish-Brazilian research project aiming at exploring sub scale flight testing. A 13% scale fighter aircraft is used as a test bench for developing methods and procedures for data acquisition. This paper will present an aerodynamic database as a partial result of the collaborative project.
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| 45. |
- Jouannet, Christopher, 1974-, et al.
(författare)
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Aircraft design education at Linköpings University
- 2007
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part G, Journal of Aerospace Engineering. - 0954-4100 .- 2041-3025. ; 221:2, s. 217-224
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Tidskriftsartikel (refereegranskat)abstract
- Aircraft design is a complex multi-disciplinary task and teaching can easily tend to be too theoretical, not providing the students the tools they need to successfully participate in industrial projects. The approach chosen at Linköping University is intended to create the right balance between theory and practice, and to place the student in the centre of the problem, in order to achieve an overall perspective of the aircraft design process. This article presents in brief layout of the courses, and in more detail, the aircraft design project course given in the last year of the aeronautical masters program, where flying hardware is designed and build, in response to a design challenge. © IMechE 2007.
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| 46. |
- Jouannet, Christopher, 1974-, et al.
(författare)
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Aircraft manoeuvers simulation, steady and unsteady aerodynamic
- 2003
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Ingår i: SAE Technical Paper. - Montreal, Canada : World Aviation Congress. - 0148-7191. ; , s. 2003-01-3034-
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Konferensbidrag (refereegranskat)abstract
- The current work present a simple model to integrate non-linear aerodynamic in conceptual design phase, before wind tunnel testing. A presentation of a simple pitch up maneuver based on three different aerodynamic models is simulated. The simulation indicates different behaviors depending on the aerodynamic model, and shows the importance of including unsteady aerodynamic.
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| 47. |
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| 48. |
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| 49. |
- Jouannet, Christopher, 1974-, et al.
(författare)
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Design process for micro air vehicles
- 2003
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Ingår i: Bristol International UAV systems conference,2003. - Bristol, UK : UAV. - 0862925347
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Konferensbidrag (refereegranskat)abstract
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| 50. |
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