| 1. |
- Andersson, Christian, et al.
(författare)
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Import and Export of Functional Mock-up Units in JModelica.org
- 2011
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Ingår i: [Host publication title missing]. - 9789173930963
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Konferensbidrag (refereegranskat)abstract
- Different simulation and modeling tools often use their own definition of how a model is represented and how model data is stored. Complications arise when trying to model parts in one tool and importing the resulting model in another tool or when trying to verify a result by using a different simulation tool. The Functional Mock-up Interface (FMI) is a standard to provide a unified model execution interface. In this paper we present an implementation of the FMI specification in the JModelica.org platform, where support for import and export of FMI compliant models has been added. The JModelica.org FMI import interface is written in Python and offers a complete mapping of the FMI C API. JModelica.org also offers a set of Pythonic convenience methods for interacting with the model in an object-oriented manner. In addition, a connection to the simulation environment Assimulo which is part of JModelica.org is offered to allow for simulation of models following the FMI specification using state of the art numerical integrators. Generation of FMI compliant models from JModelica.org will also be discussed.
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| 2. |
- Andersson, Lennart, et al.
(författare)
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Praktikfall i reglerteknik - Råspritbränneriet i Nöbbelöv
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- During spring 1998 the course Industrial Case Studies in Control was given at the Department of Automatic Control in Lund. The course consisted of a project at an industry with control applications. This report considers a project at the crude alcohol distillery in Nöbbelöv, where the base product for the liquor Absolut Vodka is produced. The distillery had problems with fluctuations in the concentration of ethanol in the crude alcohol. The purpose of the project was to analyze the cause of the fluctuations, and if possibly eliminate it. The fluctuations were cause by an output limiter on a controller, and were relatively easily eliminated. To examine if control performance could be further improved, a series of experiments was carried out on the plant. The result of the experiments were then used to derive a simple process model, and a suggestion for new controller parameters.
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| 3. |
- Andersson, Mats, et al.
(författare)
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Road Friction Estimation
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This project is part of the Swedish IVSS program. The aim of IVSS is to stimulate research and development for the road safety of the future. Road conditions with low friction have been identified as a frequent cause of traffic accidents. Therefore, technology to automaticallydetect changes in road conditions and alert the driver or take proper actions with active driver support systems would be a key contribution to increased road safety.The aim of this project was to investigate the possibilities to estimate the tire to road friction.Three different approaches have been developed and evaluated, from concept to early prototypes in test vehicles. In the first method, the estimation of the coefficient of friction is based on the forces and torques that are produced at the front tires at cornering maneuvers.The second method is based on a physical model of the tire behavior and estimates road friction from information on the forces that are produced at straight driving. The third method is based on an optical sensor that classifies the road surface ahead of the vehicle.The three methods have been successfully evaluated in proving ground and public road tests in summer and winter conditions with different tires, and have been compared with reference measurements. The conclusion is that all three methods can be used for tire to road frictionestimation and are recommended for further development and industrialization.
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| 4. |
- Askerdal, Örjan, 1973, et al.
(författare)
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A Control Theory Approach for Analyzing the Effects of Data Errors in Safety-Critical Control Systems
- 2002
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Ingår i: Pacific Rim International Symposium on Dependable Computing, 2002. Proceedings. 2002. - 0769518524 ; , s. 105-114
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Konferensbidrag (refereegranskat)abstract
- Computers are increasingly used for implementing controlalgorithms in safety-critical embedded applications, such asengine control, braking control and flight surfacecontrol. Addressing the consequent coupling of control performancewith computer related errors, this paper develops a composite computerdependability/control theory methodology for analyzing the effectsdata errors have on control system dependability. The effect is measured as theresulting control error (defined as the difference between the desired value ofa physical property andits actual value). We use maximum bounds on this measure as the criterion forcontrol system failure (i.e., if the control error exceeds a certain threshold,the system has failed).In this paper we a) present suitable models of computer faults for analysis of control level effects andrelated analysis methods, and b) apply traditional control theoryanalysis methods for understanding the effects of data errors onsystem dependability. An automobile slip-control brake-system is used as an example showing the viability of our approach.
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| 5. |
- Askerdal, Örjan, et al.
(författare)
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Analyzing the Impact of Data Errors in Safety-Critical Control Systems
- 2003
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Ingår i: IEICE Transactions on Information and Systems. - 0916-8532. ; E86-D:12, s. 2623-2633
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Tidskriftsartikel (refereegranskat)abstract
- Computers are increasingly used for implementing controlalgorithms in safety-critical embedded applications, such asengine control, braking control and flight surfacecontrol. Consequently, computer errors can have severe impact on the safety of such systems. Addressing the coupling of control performance with computer related errors, this paper develops a methodology for analyzing the impact data errors have on control system dependability. The impact of a data error is measured as the resulting control error. We use maximum bounds on this measure as the criterion forcontrol system failure (i.e., if the control error exceeds a certain threshold, the system has failed).In this paper we a) develop suitable models of computer faults for analysis of control level effects andrelated analysis methods, and b) apply traditional control theoryanalysis methods for understanding the impacts of data errors onsystem dependability. An automobile slip-control brake-system is used as an example showing the viability of our approach.
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| 6. |
- Bengtsson, Johan, et al.
(författare)
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Modeling of HCCI Engine Combustion for Control Analysis
- 2004
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Ingår i: Proceedings 43rd IEEE Conference on Decision and Control. - 0191-2216. - 0780386825 ; 2, s. 1682-1687
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Konferensbidrag (refereegranskat)abstract
- Operation of homogeneous charge compression ignition (HCCI) enginesare very sensitive to timing variations in the combustion of theair-fuel charge mixture and require precise control of the ignitioninstant to run properly. It is therefore essential to understand thecharacteristics of timing variations under various operatingconditions in order to find suitable control strategies. This paperpresents a first step towards the construction of an HCCI enginemodel aimed at studies on timing control strategies. The goal is to(qualitatively) reproduce the timing effects that may be observed ona real engine. The proposed model includes a lumped chemical kineticmodel for hydrocarbon fuels to predict autoignition. Single-cyclesimulations are compared with experimental results from a realengine to validate the model.
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| 7. |
- Bruzelius, Fredrik, et al.
(författare)
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Experimental Validation of the Brush Tire Model
- 2007
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Konferensbidrag (refereegranskat)abstract
- The paper presents an experimental validation of the physically based brush-tire model towards the tire behavior in a number of different realistic conditions. Results are presented of measurements performed with summer, winter and studded tires on different road foundations such as wet and dry asphalt, basalt, snow and ice. The purpose behind the validation is to study the possibilities to use the brush model to estimate the friction coefficient from measurements or estimates of the longitudinal tire forces and tire slip. The article both validates the model agreement and investigates the sensitivity of the included tire parameters toward various factors that may change during normal run of the vehicle. The study has been performed within the Road Friction Estimation project that has been a part the IVSS-program financed by the Swedish government and a framework of automotive related companies. The measurements were conducted by VTI, the Swedish National Road and Transport Research Institute using the test truck BV12.
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| 8. |
- de Wit, Carlos Canudas, et al.
(författare)
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Friction Models and Friction Compensation
- 1998
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Ingår i: European Journal of Control. - 1435-5671. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews friction phenomena and friction models of interest for automatic control. Particular emphasis is given to two recently developed dynamic friction models, the Bliman-Sorine model and the LuGre model. These models capture many frictional phenomena observed in laboratory experiments. The behaviors of the models in different situations are discussed in detail. Methods for friction compensation are presented and illustrated with results from practical experiments.
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| 9. |
- Gäfvert, Magnus, et al.
(författare)
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A 9-DOF Tractor-Semitrailer Dynamic Handling Model for Advanced Chassis Control Studies
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A nonlinear dynamic handling model for a tractor-semitrailer combination vehicle is presented in this report. The equations of motion are derived from the fundamental equations of dynamics in Euler's formulation without approximations. The model is modular in the sense that it is easy to change axle configuration, tyre model, suspension model, or to add new features. The primary aim of the model is simulations of handling scenarios with active yaw control, using unilateral braking and possibly tractor rear wheel steering. Other applications of the model may include real-time hardware-in-the-loop simulations of tractor-semitrailer handling scenarios. The model is formulated as a state-space model that may be implemented in standard simulation environments. A Simulink (TM) implementation is presented. Simulation results are compared with experiments to validate the model.
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| 10. |
- Gäfvert, Magnus, et al.
(författare)
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A 9-DOF Tractor-Semitrailer Dynamic Handling Model for Advanced Chassis Control Studies
- 2004
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 41:1, s. 51-82
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a flexible and modular 9-degrees-of-freedomnonlinear dynamic handling model for a tractor-semitrailer combinationvehicle. The equations of motion are derived from the fundamentalequations of dynamics in Euler's formulation. The primary aim of themodel is simulations of handling scenarios with active yaw control,using unilateral braking and possibly tractor rear wheel steering. Theapplications of the model are not limited to this domain, but mayprove useful in other areas of tractor-semitrailer handling analysisor hardware-in-the-loop simulations. The model is formulated as astate-space model that may be implemented in standard simulationenvironments. A Simulink implementation is presented. Simulationresults are compared with experiments to validate the model.
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