| 1. |
- Bengtsson, Johan, et al.
(författare)
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Closed-loop Combustion Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: International Journal of Adaptive Control and Signal Processing. - : Wiley. - 0890-6327 .- 1099-1115. ; 18:2, s. 167-179
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Tidskriftsartikel (refereegranskat)abstract
- Homogeneous charge compression ignition (HCCI) is a hybrid of the sparkignition and compression ignition engine concepts. As in a sparkignition engine, a homogeneous fuel-air mixture is created in theinlet system. During the compression stroke the temperature of themixture increases and reaches the point of auto ignition, just as in acompression ignition engine (or Diesel). One challenge with HCCI engines isthe need for good timing control of the combustion. Auto ignition of ahomogeneous mixture is very sensitive to operating condition. Evensmall variations of the load can change the timing from too early totoo late combustion. Thus a fast combustion timing control isnecessary since it sets the performance limitation of the loadcontrol. As measurement for combustion timing feedback, the crank angleof 50% burnt has been used. This paper performs a comparative studyof different cylinder-pressure based methods for estimating the crankangle of 50% burnt. The estimates are compared in terms of accuracy,robustness and feasibility for cycle-to-cycle real-time control.Dynamic models of CA50 are estimated using system identification asa means to find models relevant to engine control.
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| 2. |
- Bengtsson, Johan, et al.
(författare)
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Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: Proceedings of the 2004 American Control Conference, ACC : June 30 - July 2, 2004, Boston Sheraton Hotel, Boston, Massachusetts. - 0743-1619. - 0780383354 ; 5, s. 4048-4053
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Konferensbidrag (refereegranskat)abstract
- The Homogeneous Charge Compression Ignition (HCCI) combustionconcept lacks direct ignition timing control, instead the autoignition depends on the operating condition. Since auto ignition of ahomogeneous mixture is very sensitive to operating conditions, a fastcombustion timing control is necessary for reliable operation. Hence,feedback is needed and the crank angle of 50% burnt (CA50) has provedto be a reliable feedback indicator of on-going combustion inpractice. CA50 or other methods for detecting on-going cylinderpressure used in the feedback control of a HCCI engine all rely onpressure sensors. This paper presents a newcandidate for control of HCCI engine by using the electronicconductive properties in the reaction zone. This phenomenon is calledion current. This paper perform combustion timing control based on ioncurrent and compare it with control based on pressure sensor. Thecombustion timing control is performed on cycle-to-cycle basis and the engine is a one-cylinder version of a heavy duty engine equipped with a port injection system using dual fuels.
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| 3. |
- Bengtsson, Johan, et al.
(författare)
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System Identification of Homogenous Charge Compression Ignition (HCCI) Engine Dynamics
- 2004
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Ingår i: Advances in Automotive Control. - 0080442501 ; 37:22, s. 37-37
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Konferensbidrag (refereegranskat)abstract
- Homogeneous Charge Compression Ignition (HCCI) combustion lacksdirect ignition timing control, instead the auto ignition depends on the operatingcondition. Since auto ignition of a homogeneous mixture is very sensitive tooperating condition a fast combustion timing control is necessary for reliableoperation, the ignition timing control design requiring appropriate modelsand system output variables for its feedback design. This paper demonstratesthe use of system modeling and identification as a means to find modelsrelevant to the engine control. The identification methods used were varioussubspace-based methods. An LQG controller was designed based on the estimatedmodels and tested on a six-cylinder heavy duty engine running in HCCI operation.
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| 4. |
- Johansson, Lars-Olof, 1957, et al.
(författare)
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Goal conflicts in political decision making: a survey of municipality politicians' view of road pricing.
- 2004
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Ingår i: Environment & Planning C: Government & Policy. - 0263-774X .- 1472-3425. ; 21:4, s. 615-624
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Tidskriftsartikel (refereegranskat)abstract
- Investigates the existence of goal conflicts in political decision-making in the case of municipality politicians in Sweden on the issue of road pricing scheme. Goals of municipality politicians other than reducing car use; Possibility of failure in achieving environmental goals because of goal conflicts.
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| 5. |
- Strandh, Petter, et al.
(författare)
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Cycle-to-Cycle Control of a Dual-Fuel HCCI Engine
- 2004
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Ingår i: SAE Paper 2004-01-0941. - 0148-7191. - 0768013550 ; SP-1819
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Konferensbidrag (refereegranskat)abstract
- A known problem of the HCCI engine is its lack of direct control andits requirements of feedback control. Today there exists severaldifferent means to control an HCCI engine, such as dual fuels,variable valve actuation, inlet temperature and compression ratio.Independent of actuation method a sensor is needed. In this paper weperform closed-loop control based on two different sensors, pressureand ion current sensor. Results showing that they give similar controlperformance within their operating range are presented.Also a comparison of two methods of designing HCCI timing controller,manual tuning and model based design is presented. A PIDcontroller is used as an example of a manually tuned controller. ALinear Quadratic Gaussian controller exemplifies model basedcontroller design. The models used in the design were estimated usingsystem identification methods.The system used in this paper performs control on cycle-to-cyclebasis. This leads to fast and robust control. Dual fuels withdifferent octane numbers were used to control the combustion timing.The engine was a 12 liter 6 cylinder heavy-duty diesel engine modifiedwith a port fuel injection system which has dual fuels connected.
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| 6. |
- Strandh, Petter, et al.
(författare)
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Ion Current Sensing for HCCI Combustion Feedback
- 2003
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Ingår i: SAE Technical Papers. - 0148-7191. ; :2003-01-3216
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Konferensbidrag (refereegranskat)abstract
- Measurement of ion current signal from HCCI combustionwas performed. The aim of the work was to investigateif a measurable ion current signal exists and if it is possible to obtain useful information about the combustion process. Furthermore, influence of mixture quality in termsof air/fuel ratio and EGR on the ion current signal wasstudied. A conventional spark plug was used as ionizationsensor. A DC voltage (85 Volt) was applied acrossthe electrode gap. By measuring the current through thegap the state of the gas can be probed. A comparisonbetween measured pressure and ion current signal wasperformed, and dynamic models were estimated by usingsystem identification methods.The study shows that an ion current signal can be obtainedfrom HCCI combustion and that the signal levelis very sensitive to the fuel/air equivalence ratio. Themost important result from this study is that the ion current signal proved to be an excellent indicator of the actual combustion timing which is crucial piece of information for HCCI control.
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| 7. |
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| 8. |
- Hall, Lars, et al.
(författare)
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On the role of brain-imaging technologies in the calibration of learning strategies
- 2003
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Ingår i: Proceedings 3rd IEEE International Conference on Advanced Technologies. - 0769519679 ; , s. 396-397
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Konferensbidrag (refereegranskat)abstract
- We discuss the process of calibration and verification of learning strategies, and argue that a careful consideration of data from brain-imaging methodologies, as well as a systematic treatment of first-person subjective reports, is the most promising route for educational researchers to answer the age-old question about what a learning strategy really amounts to. In addition we argue that such considerations may pave the ground for a future breed of ICT learning applications based on a refined concept of neurofeedback
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| 9. |
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| 10. |
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| 11. |
- 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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| 12. |
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| 13. |
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| 14. |
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| 15. |
- Johansson, Daniel, et al.
(författare)
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A multivariate approach applied to microarray data for identification of genes with cell cycle-coupled transcription
- 2003
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Ingår i: Bioinformatics. - : Oxford University Press (OUP). - 1367-4811 .- 1367-4803. ; 19:4, s. 467-73
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Tidskriftsartikel (refereegranskat)abstract
- We have analyzed microarray data using a modeling approach based on the multivariate statistical method partial least squares (PLS) regression to identify genes with periodic fluctuations in expression levels coupled to the cell cycle in the budding yeast, Saccharomyces cerevisiae. PLS has major advantages for analyzing microarray data since it can model data sets with large numbers of variables and with few observations.A response model was derived describing the expression profile over time expected for periodically transcribed genes, and was used to identify budding yeast transcripts with similar profiles. PLS was then used to interpret the importance of the variables (genes) for the model, yielding a ranking list of how well the genes fitted the generated model. Application of an appropriate cutoff value, calculated from randomized data, allows the identification of genes whose expression appears to be synchronized with cell cycling. Our approach also provides information about the stage in the cell cycle where their transcription peaks.Three synchronized yeast cell microarray data sets were analyzed, both separately and combined. Cell cycle-coupled periodicity was suggested for 455 of the 6,178 transcripts monitored in the combined data set, at a significance level of 0.5%. Among the candidates, 85% of the known periodic transcripts were included. Analysis of the three data sets separately yielded similar ranking lists, showing that the method is robust.
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| 16. |
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| 17. |
- Johansson, Lena, 1967-, et al.
(författare)
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Phosphate removal using blast furnace slags and opoka-mechanisms
- 2000
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Ingår i: Water Research. - 0043-1354 .- 1879-2448. ; 34:1, s. 259-265
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Tidskriftsartikel (refereegranskat)abstract
- The abiotic sorption efficiency of on-site wastewater treatment systems can be improved by using a strongly sorbing filter material that, if it retains phosphorus (P) in a plant available way, can be used as fertiliser when P saturation is achieved. Two materials, blast furnace slag and the siliceous sedimentary rock opoka, have shown a high P sorption capacity and were included in a set of experiments to investigate the P retention mechanisms from model P-solution. Experiments focusing on the P sorption, capacity and calcium (Ca) and PO4 determination were carried out. The pH was also measured. The P sorption experiment showed that some slags were efficient P retainers, while the opoka was the least efficient P retainer. The pH decreased in all samples as a function of P addition. In the slag samples, the Ca concentration also decreased as a function of P addition, suggesting Ca-P precipitation as the major P removal mechanism for the slag. The Ca and PO4 speciation data ruled out the formation of amorphous calcium phosphates and/or octacalcium phosphate as the major P removal mechanism. However, the calculated ion activity products displayed clear evidence that hydroxyapatite had precipitated above a certain critical supersaturation limit. This would explain the poor P retention efficiency of the opoka samples in this study as the ion activity products were too low. The finding that direct hydroxyapatite formation is the predominant P removal mechanism might have important implications for their possible use as fertiliser due to the poor solubility of hydroxyapatite.
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| 18. |
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| 19. |
- Lognoli, D, et al.
(författare)
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Fluorescence lidar imaging of the cathedral and baptistery of Parma
- 2003
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171. ; 76:4, s. 457-465
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Tidskriftsartikel (refereegranskat)abstract
- Extensive fluorescence multispectral imaging of the cathedral and baptistery of Parma, Italy, is reported and discussed. In particular, the first fluorescence imaging data from protection-treated stony materials were recorded. Fluorescence spectra were taken with a mobile lidar system scanning the monument surfaces with a frequency-tripled Nd:YAG laser beam from a distance of about 80 m. For each pixel of the area investigated, a high-spectral-resolution spectrum in the full visible range was acquired. The principal-component analysis technique was used to obtain thematic maps that outlined areas subject to protective treatment and biological growth, and other features, such as different types of stones and decoration pigments.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Vressner, Andreas, et al.
(författare)
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Multiple Point Ion Current Diagnostics in an HCCI Engine
- 2004
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Ingår i: SAE Transactions, Journal of Engines. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0096-736X. ; 113:3, s. 544-550
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Tidskriftsartikel (refereegranskat)abstract
- Interest in ion current sensing for HCCI combustion arises when a feedback signal from some sort of combustion sensor is needed in order to determine the state of the combustion process. A previous study has revealed that ion current sensors in the form of spark plugs can be used instead of expensive piezoelectric transducers for HCCI combustion sensing. Sufficiently high ion current levels were achieved when using relatively rich mixtures diluted with EGR. The study also shows that it is not the actual dilution per se but the actual air/fuel equivalence ratio which is important for the signal level. Conclusions were made that it is possible to obtain information on combustion timing and oscillating wave phenomena from the measurements. However, the study showed that the ion current is local compared to the pressure which is global in the combustion chamber. This observation triggered the present study where the aim is to investigate the ion current at different locations in the combustion chamber. The ion current was measured simultaneously at seven locations in the combustion chamber. In order to achieve this, 6 spark plugs were fitted circumferentially in a spacer placed between the cylinder block and the head. The seventh spark plug was placed in the cylinder head. Individual DC sources of 85 volts were applied across the spark plug gaps. The present study indicates that the combustion timing seems to be dependent on the wall temperature at the different spark plug locations. The largest difference in timing between different locations in the combustion chamber was 2 CAD. The ion current amplitude varies with different spark plug locations up to 1.5 μA. The signal strength increases with decreasing air/fuel ratio and is also affected by dilution.
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| 24. |
- Weibring, Petter, et al.
(författare)
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Fluorescence lidar imaging of historical monuments
- 2001
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Ingår i: Applied Optics. - 2155-3165. ; 40:33, s. 6111-6120
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Tidskriftsartikel (refereegranskat)abstract
- What is believed to be the first fluorescence imaging of the facades of a historical building, which was accomplished with a scanning fluorescence lidar system, is reported. The mobile system was placed at a distance of similar to 60 m from the medieval Lund Cathedral (Sweden), and a 355-nm pulsed laser beam was swept over the stone facades row by row while spectrally resolved fluorescence signals of each measurement point were recorded. By multispectral image processing, either by formation of simple spectral-band ratios or by use of multivariate techniques, areas with different spectral signatures were classified. In particular, biological growth was observed and different stone types were distinguished. The technique can yield data for use in facade status assessment and restoration planning. (C) 2001 Optical Society of America.
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| 25. |
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