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| 2. |
- Gustafsson, Fredrik, et al.
(author)
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Event Based Sampling with Application to Vibration Analysis in Pneumatic Tires
- 2001
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In: Proceedings of the 2001 IEEE International Conference on Acoustics, Speech and Signal Processing. - Linköping : Linköping University Electronic Press. - 0780370414 ; , s. 3885-3888 vol.6
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Conference paper (peer-reviewed)abstract
- Event based sampling occurs when the time instants are measured everytime the amplitude passes certain pre-defined levels. This is in contrast with classical signal processing where the amplitude is measured at regular time intervals. The signal processing problem is to separate the signal component from noise in both amplitude and time domains. Event based sampling occurs in a variety of applications. The purpose here is to explain the new types of signal processing problems that occur, and identify the need for processing in both the time and event domains. We focus on rotating axles, where amplitude disturbances are caused by vibrations and time disturbances from measurement equipment. As one application, we examine tire pressure monitoring in cars where suppression of time disturbance is of utmost importance.
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| 3. |
- Gustafsson, Fredrik, et al.
(author)
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Indirect Tire Pressure Monitoring using Sensor Fusion
- 2002
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In: Proceedings of the SAE 2002 World Congress. - Linköping : Linköping University Electronic Press.
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Conference paper (peer-reviewed)abstract
- Vehicle handling depends critically on the tire-road contact patch. When the tire inflation pressure changes the contact patch is no longer optimal and the handling properties deteriorate. Furthermore fuel consumption increases and the lifetime of the tires decreases. Therefore it is very important that the tires are correctly inflated.We here focus on an indirect tire pressure monitoring system, where no pressure sensors are needed. The system is based on vibration and wheel radius analysis. These two approaches are combined for optimal performance concerning sensitivity to detect pressure losses and robustness to different driving conditions. When these two approaches are combined, it is possible to detect pressure losses larger than 15% in one, two, three, or four (diffusion) tires within 1 minute. It is also possible to detect which of the tires that are underinflated.
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| 4. |
- Gustafsson, Fredrik, et al.
(author)
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Sensor Fusion for Accurate Computation of Yaw Rate and Absolute Velocity
- 2001
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In: Proceedings of the SAE 2001 World Congress. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Conference paper (peer-reviewed)abstract
- In the presented sensor fusion approach, centralized filtering of related sensor signals is used to improve and correct low price sensor measurements. From this, we compute high-quality state information as drift-free yaw rate and exact velocity (accounting for unknown tire radius and slipping wheels on 4WD vehicles). The basic tool here is a Kalman filter supported by change detection for sensor diagnosis. Results and experience of real-time implementations are presented.
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| 5. |
- Gustafsson, Fredrik, et al.
(author)
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Virtual Sensors of Tire Pressure and Road Friction
- 2001
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In: Proceedings of the SAE 2001 World Congress. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
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Conference paper (peer-reviewed)abstract
- The idea of a virtual sensor is to extract information of parameters that cannot be measured directly, or at least would require very costly sensors, by only using available information. Virtual sensors are described for the friction between road and tire, the tire inflation pressure and wheel imbalance. There are certain interconnections between these virtual sensors so they are preferably implemented in one unit. Results from a real-time implementation, using mainly sensor information from the CAN bus, are given.
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| 6. |
- Hallén, Anders., et al.
(author)
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Ion implantation of silicon carbide
- 2002
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In: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 186-194
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Journal article (peer-reviewed)abstract
- Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.
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| 7. |
- Olhager, Jan, 1955-, et al.
(author)
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Supply chain impacts at Ericsson - From production units to demand-driven supply units
- 2002
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In: International Journal of Technology Management. - 0267-5730 .- 1741-5276. ; 23:1-3, s. 40-59
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Journal article (peer-reviewed)abstract
- This paper deals with the impact of supply chains on operations management at Ericsson Mobile Communications. It specifically deals with the transition of the Link÷ping plant from being a production unit to the role of a supply unit in a demand-driven supply chain. This change has had a great impact on many factors. We discuss and analyse the most important issues. These are related to supply chain structure and flexibility, reengineering the information flow, the management of the supply process, and performance measurement.
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| 8. |
- Persson, Fredrik, 1971-, et al.
(author)
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Performance simulation of supply chain designs
- 2002
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In: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 77:3, s. 231-245
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Journal article (peer-reviewed)abstract
- The focus on supply chain management has increased in recent years, among academics as well as among practitioners. In this paper, we present a supply chain simulation study for a real case, concerned with the manufacturing of mobile communication systems. The purpose of the study is twofold. One objective is to evaluate alternative supply chain designs with respect to quality, lead-times and costs as the key performance parameters. A second objective is to increase the understanding of the interrelationships among these and other parameters, relevant for the design of the supply chain structure. The design alternatives differ in terms of the level of integration and synchronisation between supply chain stages. Modelling and validation issues are highlighted since these are fundamental to a supply chain simulation study. The results are discussed and a model capturing the relationships among cost, quality, and lead-times, based on the simulation study, is presented. ⌐ 2002 Elsevier Science B.V. All rights reserved.
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| 9. |
- Persson, Fredrik, 1971-, et al.
(author)
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The Effect of Differentiation on Prison Population : A Simulation Study of the Swedish Prison System
- 2004
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In: European Simulation Symposium,2004. - San Diego, USA : SCS International. ; , s. 144-
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Conference paper (peer-reviewed)abstract
- This paper describes the case of a simulation study of the Swedish Prison and Probation system regarded as a queuing system. The situation in Swedish prisons today is not acceptable with a utilisation over 100 per cent. The short-term solution of the problem has been to overcrowd the prisons. The purpose of this work is to describe the relations between waiting time in remand prison, the official number of cells in prisons and the degree of differentiation regarding to the expected torrent of criminals. Differentiation is the attempt to keep different categories of clients apart during their prison time. The degree of differentiation is defined as the number of defined categories used for client placement. The conclusions from this study is that there are not enough number of prison cell available. The situation for male inmates/clients is more critical than for female clients. The results from the study suggest that there needs to be approximately 11,000 prison cells in total to meet the unofficial recommendation of a maximum of seven days in remand prison.
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| 10. |
- Persson, Fredrik
(author)
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The impact of different levels of detail in manufacturing systems simulation models
- 2002
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In: Robotics and Computer-Integrated Manufacturing. - : Pergamon Press. - 0736-5845 .- 1879-2537. ; 18:3-4, s. 319-325
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Journal article (peer-reviewed)abstract
- Modelling and simulating manufacturing systems often involves several different organisational units. This can make data collection difficult and it can be hard to obtain data that allows for the model to be built with a consistent level of detail. To investigate the impact of a varying level of detail, a manufacturing system was modelled using different levels of detail. The first model was modelled at a high level of detail containing all elements in the system. The second model was an aggregation of some of the processes in the system and the third model consisted only of the main processes. The experiments performed with the models, aimed at finding differences between models' outputs that originated from the choice of the level of detail. The results show that there are significant differences between the models. The simulation models used for this paper are made in collaboration with a company in the mobile communications industry and deals with supply chain problems.
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