| 1. |
- Pettersson, Karl, 1983-, et al.
(författare)
-
Simulation Aided Design and Testing of Hydromechanical Transmissions
- 2014
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Ingår i: The 9th JFPS International Symposium on Fluid Power, Matsue, 2014. - 4931070108
-
Konferensbidrag (refereegranskat)abstract
- This paper demonstrates the use of high-speed simulation in transmission conceptual design and presents a transmission test bed for hardware-in-the-loop simulations of hydromechanical transmission concepts. Complex transmissions, such as multiple-mode hydromechanical transmissions and hydraulic hybrid transmissions, present new difficulties and costs in the development process. There is today a greater demand for more efficient product development and more work has shifted towards simulation. The Hopsan simulation package allows robust, high-speed simulations suitable for both offline and hardware-in-the-loop simulation. New simulation models for hydromechanical transmissions are developed and used to simulate a known two-mode transmission concept. The same concept is also tested in hardware-in-the-loop simulations in the proposed transmission test bed. Results show good agreement with the hardware tests and highlight the proficiency of the simulation tools.
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| 2. |
- Demaziere, Christophe, 1973, et al.
(författare)
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Investigation of the MTC noise estimation with a coupled neutronic/thermal-hydraulic dedicated model – “Closing the loop”
- 2012
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Ingår i: Proc. Int. Conf. on Advances in Reactor Physics – Linking Research, Industry, and Education (PHYSOR 2012), Knoxville, TN, USA, April 15-20, 2012, American Nuclear Society. - 9781622763894 ; 1, s. 361-375
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the reliability of different noise estimators aimed at determining the Moderator Temperature Coefficient (MTC) of reactivity in Pressurized Water Reactors. By monitoring the inherent fluctuations in the neutron flux and moderator temperature, an on-line monitoring of the MTC without perturbing reactor operation is possible. In order to get an accurate estimation of the MTC by noise analysis, the point-kinetic component of the neutron noise and the core-averaged moderator temperature noise have to be used. Because of the scarcity of the in-core instrumentation, the determination of these quantities is difficult, and several possibilities thus exist for estimating the MTC by noise analysis. Furthermore, the effect of feedback has to be negligible at the frequency chosen for estimating the MTC in order to get a proper determination of the MTC. By using an integrated neutronic/thermal-hydraulic model specifically developed for estimating the three-dimensional distributions of the fluctuations in neutron flux, moderator properties, and fuel temperature, different approaches for estimating the MTC by noise analysis can be tested individually. It is demonstrated that a reliable MTC estimation can only be provided if the core is equipped with a sufficient number of both neutron detectors and temperature sensors, i.e. if the core contain in-core detectors monitoring both the axial and radial distributions of the fluctuations in neutron flux and moderator temperature. It is further proven that the effect of feedback is negligible for frequencies higher than 0.1 Hz, and thus the MTC noise estimations have to be performed at higher frequencies.
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| 3. |
- Furberg, Andreas, 1989, et al.
(författare)
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Optimal Selection of Driving Modes along a Commuter Route for a Plug-in Hybrid Electric Vehicle
- 2014
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 2405-8963 .- 1474-6670. - 9783902823625 ; , s. 7867-7872
-
Konferensbidrag (refereegranskat)abstract
- Many plug-in hybrid electric vehicles have predefined driving modes, e.g. electric drive and charge sustaining mode. For a driver it is not a trivial task to select a fuel optimal sequence of driving modes; a poor selection might even result in a severely degraded fuel economy. The purpose of this paper is therefore to investigate optimal mode selection along a well known commuter route. To obtain a predictable driving behaviour it is assumed that the driving mode is only allowed to change at a limited number of decision points, located where the driving conditions along the route changes. The optimal mode selection is computed using the well known Dynamic Programming algorithm. However, the results show that the optimal mode selection might be perceived as counterintuitive, as a mode is not necessarily optimal over a connected set with respect to battery state of charge, at a given decision point. To mitigate this type of behaviour a suboptimal algorithm is proposed, in which a mode is associated with one unique interval of state of charge at any decision point along the route. The results indicate that the proposed algorithm is only marginally suboptimal with respect to the optimal solution.
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| 4. |
- Hjort af Ornäs, Viktor, 1976, et al.
(författare)
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The spread of product development methodology: Exploring drivers and barriers in Swedish Industry
- 2014
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Ingår i: 10th Biannual NordDesign Conference, NordDesign 2014, Espoo, Finland, 27-29 August. - 9781904670582 ; , s. 540-549
-
Konferensbidrag (refereegranskat)abstract
- The outcome of Design, Innovation and Product development research is often manifested asrecommendations in the form of methods, but these do not always find their way intoindustrial application. This paper elaborates on drivers and barriers for the spread of productdevelopment methodology based on 41 interviews with managers, designers, developers andknowledge brokers. Results indicate a range of motives for adopting methods including e.g.coordination of different actors, generation of documentation, methods serving as tools forvarious design tasks etc. However; the value of tools must be seen in relation to localconditions and practices. The spread of methods occurs between and within organisations andmay be actively supported while ideally “good tools spread themselves”. Participants call formethods to be scalable or malleable, guiding, informing and enabling without constraining orenforcing too rigid procedures.
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| 5. |
- Jagtap, Santosh, et al.
(författare)
-
Comparing design processes for the BOP and TOP markets
- 2013
-
Ingår i: ICED. - 2220-4342 .- 2220-4334. - 9781904670445 ; 1, s. 211-220
-
Konferensbidrag (refereegranskat)abstract
- The base (BOP) and the top (TOP) of the world income pyramid represent the poor people and the people from developed countries, respectively. About two-fifths of the world population can be categorized as poor. Poverty is a trap because children born to poor parents are likely to grow up to be poor adults. In recent years, a poverty reduction approach that combines business development with poverty alleviation has received attention. The design of products for the BOP is an important ingredient of this poverty reduction approach. While companies are beginning to address the product needs of the BOP, there is limited practical and theoretical knowledge to support them. The current understanding of the design for the BOP is limited. This study, using a protocol analysis, compared the design processes for the BOP and TOP markets. The results indicate the differences between the design processes for these markets in terms of the design strategy employed by the designers (i.e. problem driven, solution driven strategy), their requirements handling behaviour, and their information behaviour. We have discussed the implications of the findings for design practice and education.
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| 6. |
- Jagtap, Santosh, et al.
(författare)
-
Design for the BOP and TOP markets: Strategies used by the design students
- 2013
-
Konferensbidrag (refereegranskat)abstract
- The base (BOP) and the top (TOP) of the world income pyramid represent the poor people and the people from developed countries, respectively. About two-fifths of the world population can be categorized as poor. Poverty is a trap because children born to poor parents are likely to grow up to be poor adults. In recent years, a poverty reduction approach that combines business development with poverty alleviation has received attention. The design of products for the BOP is an important ingredient of this poverty reduction approach. While companies are beginning to address the product needs of the BOP, there is limited practical and theoretical knowledge to support them. The current understanding of the design for the BOP is limited. This study aims at exploring the differences between the design strategies used by the industrial design students in designing products for the BOP and TOP markets. The results indicate the differences between their design strategies (i.e. problem driven strategy, solution driven strategy) in designing products for the BOP and TOP markets. We have discussed the implications of the findings for design practice and education. In particular, we have discussed how university-based design projects for the BOP can help in developing students’ different design skills.
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| 7. |
- Jagtap, Santosh, et al.
(författare)
-
Design methods and factors influencing their uptake in product development companies: A review
- 2014
-
Ingår i: Proceedings of the 13th International Design Conference - DESIGN'14. - 1847-9073. ; DS 77, s. 231-240, s. 231-240
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Konferensbidrag (refereegranskat)abstract
- Design methods are necessary to support product development companies in improving their product development processes, and thereby in producing high quality products. The uptake of design methods in product development companies is limited and lower than one might expect. There is a wide variety of literature related to factors that influence the uptake of design methods in companies. In this paper, we synthesised this literature, and in particular, developed a framework of factors than can influence the uptake of design methods in product development companies.
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| 8. |
- Jagtap, Santosh, et al.
(författare)
-
Fighting poverty through design: Comparing design processes for the base and the top income pyramid
- 2013
-
Ingår i: Proceedings of the International Conference on Engineering Design, ICED. - 2220-4334 .- 2220-4342. ; 1:DS75-01, s. 211-220
-
Tidskriftsartikel (refereegranskat)abstract
- The base (BOP) and the top (TOP) of the world income pyramid represent the poor people and the people from developed countries, respectively. About two-fifths of the world population can be categorized as poor. Poverty is a trap because children born to poor parents are likely to grow up to be poor adults. In recent years, a poverty reduction approach that combines business development with poverty alleviation has received attention. The design of products for the BOP is an important ingredient of this poverty reduction approach. While companies are beginning to address the product needs of the BOP, there is limited practical and theoretical knowledge to support them. The current understanding of the design for the BOP is limited. This study aims at exploring the differences between the design strategies used by the industrial design students in designing products for the BOP and TOP markets. The results indicate the differences between their design strategies (i.e. problem driven strategy, solution driven strategy) in designing products for the BOP and TOP markets. We have discussed the implications of the findings for design practice and education. In particular, we have discussed how university-based design projects for the BOP can help in developing students’ different design skills.
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| 9. |
- Jagtap, Santosh, et al.
(författare)
-
How design process for the Base of the Pyramid differs from that for the Top of the Pyramid
- 2014
-
Ingår i: Design Studies. - : Elsevier BV. - 0142-694X .- 1872-6909. ; 35:5, s. 527-558
-
Tidskriftsartikel (refereegranskat)abstract
- The base (BOP) and the top (TOP) of the world income pyramid represent the poor people and the people from developed countries, respectively. The design of products for the BOP is an important ingredient of the poverty reduction approach that combines business development with poverty alleviation. However, the current understanding of the design for the BOP is limited. This study, using a protocol analysis, compared design processes for the BOP and TOP markets. The results indicate the difference between the design processes for these markets in terms of the design strategy employed by the designers (i.e. problem driven, solution driven strategy), their requirements handling behaviour, and their information behaviour.
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| 10. |
- Jagtap, Santosh, et al.
(författare)
-
Ideation Metrics: Interdependency between Average Novelty and Variety
- 2012
-
Ingår i: DS 70: Proceedings of DESIGN 2012, the 12th International Design Conference, Dubrovnik, Croatia. - 1847-9073. - 9789537738174 ; , s. 1881-1892, s. 1881-1892
-
Konferensbidrag (refereegranskat)abstract
- Abstract in Undetermined The importance of ideation in the conceptual design phase has been widely accepted. Shah et al. (2003) developed four key metrics for evaluating a designer’s exploration and expansion of design space. The four metrics are: novelty, variety, quality, and quantity of designs. The mean of novelty scores of ideas in a set (i.e. Average Novelty - AN) has also been used in some ideation studies. However, many of the studies that have computed AN and variety, have not examined the interdependency between them. This research aims at examining the interdependency between AN and variety.
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| 11. |
- Larsson, Billy, 1956, et al.
(författare)
-
Do psychotherapists with different theoretical orientations stereotype or prejudge each other?
- 2013
-
Ingår i: Journal of Contemporary Psychotherapy. - : Springer Science and Business Media LLC. - 0022-0116 .- 1573-3564. ; 43:3, s. 169-178
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates a possible threat to the progress of psychotherapy. It aims to detect and compare stereotyped or even prejudiced views among psychotherapists of different theoretical orientations, building on social psychological theory of in-groups and out-groups. Swedish psychotherapists (n = 416) of four different orientations (psychodynamic, cognitive, behavioural, or integrative/eclectic) used the valuable elements in psychotherapy questionnaire to rate the importance of various elements in psychotherapy. They also estimated how therapists of other orientations would rate these elements. These estimates were then compared with therapists' actual self-ratings in order to detect patterns of stereotyping or prejudiced views. Psychotherapists exaggerate the differences between their own and other orientations in a stereotyped way, but correctly predict what members of their own orientation (in-group) find important. However, they overestimate how important 'orientation-typical features' are to those of other orientations (out-group), indicating a clear tendency to stereotype. Overall, integrative/eclectic therapists' estimates were less stereotyped than the estimates of therapists of other orientations. A somewhat unexpected finding was that cognitive and behavioural therapists seem more inclined towards stereotyping. The stereotyped views of other theoretical orientations among psychotherapists can be argued to have negative connotations and may thus be seen as prejudices. These prejudices could create irrational and unnecessary obstacles to the development of both the science and the practice of psychotherapy and signal the need for psychotherapists of all orientations to develop a more balanced picture of each other. © 2013 Springer Science+Business Media New York.
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| 12. |
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| 13. |
- Larsson, Viktor, 1984, et al.
(författare)
-
A coupled neutronics/thermal–hydraulics tool for calculating fluctuations in Pressurized Water Reactors
- 2012
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 43, s. 68-76
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes a tool for estimating fluctuations in neutron flux, fuel temperature, moderator density and flow velocity in Pressurized Water Reactors by coupling a dynamic thermal–hydraulic module and a dynamic neutron kinetic module. The code calculates the static solution first, giving the profile of the static fuel temperature, moderator density, velocity and neutron flux. The fluctuations (called noise in this work) are the differences between the actual time-dependent values and the corresponding mean values. The fluctuations are in general induced by perturbations in the thermal–hydraulic parameters, e.g. moderator temperature or density, at the inlet of the core. There is also a possibility to directly define the perturbations in the macroscopic cross-sections and to supply them to the neutronic part of the model. The model was validated against two separate calculations using two different commercial tools.
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| 14. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Benefit of Route Recognition in Energy Management of Plug-in Hybrid Electric Vehicles
- 2012
-
Ingår i: Proceedings of the American Control Conference. - : IEEE. - 0743-1619. - 9781457710940 ; , s. 1314-1320
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the benefit of an energymanagement system that autonomously can recognize when aplug-in hybrid electric vehicle is driven along known commutingroutes. The presented route recognition algorithm comparesthe GPS trajectory of the ongoing trip with stored commutingroutes using the well known cross-correlation operation. If aroute is recognized the energy management system switchesfrom a charge depleting charge sustaining discharge strategyto a strategy where the battery discharge rate is adapted to thelength of the recognized route, thereby decreasing the averagedischarge current and the resistive losses.The proposed system is evaluated using simulations onone month of logged commuter driving data. The resultsfor an energy management system based on the equivalentconsumption minimization strategy indicate an overall fuel costreduction of 1.5% compared to an system that only utilize acharge depleting charge sustaining strategy.
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| 15. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Commuter Route Optimized Energy Management of Hybrid Electric Vehicles
- 2014
-
Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 15:3, s. 1145-1154
-
Tidskriftsartikel (refereegranskat)abstract
- Optimal energy management of hybrid electric vehicles requires a priori information regarding future driving conditions; the acquisition and processing of this information is nevertheless often neglected in academic research. This paper introduces a commuter route optimized energy management system, where the bulk of the computations are performed on a server. The idea is to identify commuter routes from historical driving data, using hierarchical agglomerative clustering, and then precomputean optimal solution to the energy management controlproblem with dynamic programming; the obtained solution canthen be transmitted to the vehicle in the form of a lookup table. To investigate the potential of such a system, a simulation study is performed using a detailed vehicle model implemented in the Autonomie simulation environment for MATLAB/Simulink. The simulation results for a plug-in hybrid electric vehicle indicate that the average fuel consumption along the commuter route(s) can be reduced by 4%–9% and battery usage by 10%–15%.
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| 16. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Comparing two approaches to precompute discharge strategies for plug-in hybrid electric vehicles
- 2013
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823434 ; , s. 121-126
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates two alternative approaches to precompute a discharge strategy for the main commuter route of a plug-in hybrid electric vehicle. The first approach is based on the idea of computing a state of charge reference trajectory by solving a convex program; while the second approach utilizes dynamic programming to determine an optimal cost-to-go function. During real-time operation the torque split is decided by an equivalent consumption minimization strategy where the main difference between the two approaches is how the equivalence factor is determined. With the first approach it is adapted to track the state of charge reference trajectory and in the second approach it is given by the partial derivative of the cost-to-go function with respect to state of charge. To evaluate the two approaches a simulation study is performed in the dynamic vehicle modelling software Autonomie using logged commuter driving data. The simulation results indicate no clear difference between the two approaches in terms of fuel economy and battery usage. Both approaches are, however, significantly better than a charge depleting charge sustaining discharge strategy.
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| 17. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Comparison of the calculated neutron noise using finite differences and the Analytical Nodal Method
- 2012
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 43, s. 176-182
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a comparison of the calculated neutron noise, i.e. the fluctuation of the neutron flux around its average value assuming that all processes are stationary, is conducted, where the neutron noise is calculated using finite differences alone and with finite differences where the Analytical Nodal Method is used to correct the neutron currents, respectively. It is seen that the lower the frequency of the noise source, the larger difference between the two solutions. The main conclusion from this work is that the gain of calculating the neutron noise using the more sophisticated Analytical Nodal Method compared to the increase of the corresponding computational burden is too little to motivate the use of the ANM.
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| 18. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Cubic Spline Approximations of the Dynamic Programming Cost-to-go in HEV Energy Management Problems
- 2014
-
Ingår i: 13th European Control Conference, ECC 2014; Strasbourg Convention and Exhibition CenterPlace de BordeauxStrasbourg; France; 24 June 2014 through 27 June 2014. - 9783952426913 ; , s. 1699-1704
-
Konferensbidrag (refereegranskat)abstract
- The energy management problem of a hybridelectric vehicle (HEV) is a non-linear and mixed integeroptimization problem. The problem can be solved with DynamicProgramming (DP), but the algorithm requires the problem tobe gridded in time, states and control signals. To ensure a highaccuracy of the solution the grid must be dense, meaning thatthe cost-to-go can require several megabytes of memory. Thescope of this paper is therefore twofold. The first topic is asensitivity study, where the effect of a sparsely gridded state isinvestigated, both for an HEV and a plug-in HEV (PHEV). Thestudy shows that it is possible to use a sparse grid for an HEV,but not for a PHEV. The second topic and the main contributionis a method to approximate the DP cost-to-go with cubic splines.The results indicate that it is possible to use only a few splines,if the knot points are determined based on the characteristicsof the cost-to-go. Thereby it is possible to significantly reducethe memory requirements, without any noticeable increase insimulated fuel consumption.
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| 19. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Cubic Spline Approximations of the Dynamic Programming Value Function in HEV Energy Management Problems
- 2013
-
Ingår i: Workshop for new energy vehicle dynamic system and control technology.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Energy management of a hybrid electric powertrain is a non-linear and mixed integer optimization problem that often is solved with Dynamic Programming (DP); thus requiring the problem to be gridded both in time, control signals and the states. To ensure a high accuracy of the solution the grid must be dense, meaning that the resulting value function can require several megabytes of memory. The first contribution of the paper is therefore a sensitivity study where the effect of a sparsely gridded state is investigated, both for a hybrid electric vehicle (HEV) and a plug-in HEV (PHEV). The study shows that it is possible to use a sparse grid for an HEV, but not for a PHEV. The second contribution is a method to approximate the DP value function with cubic splines. The results indicate that it is possible to useonly a few splines, if the knot points are determined based on the characteristics of the value function. Thereby it is possible to significantly reduce the memory requirements of the PHEV value function, without any noticeable increase in fuel consumption.
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| 20. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Development of a numerical tool for calculating the fluctuations in PWRs
- 2011
-
Ingår i: Proc. of XV MEETING ON REACTOR PHYSICS CALCULATIONS IN THE NORDIC COUNTRIES.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the development of a tool for estimating fluctuations in neutron flux, fuel temperature, moderator density and flow velocity in Pressurized Water Reactors by coupling a dynamic thermal-hydraulic module and a dynamic neutron kinetic module. The code calculates the static solution first, giving the profile of the static fuel temperature, moderator density, velocity and neutron flux. The fluctuations (called noise in this work) are the differences between the actual time-dependent values and the corresponding mean values. The fluctuations are in general induced by perturbations in the thermal-hydraulic parameters, e.g. moderator temperature or density, at the inlet of the core. There is also a possibility to directly define the perturbations in the macroscopic cross-sections and to supply them to the neutronic part of the model.
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| 21. |
- Larsson, Viktor, 1984
(författare)
-
Development of an integrated neutronic/thermal-hydraulic tool for estimating fluctuations in PWRs
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Monitoring and diagnostics of a reactor core at a given state is very important for detecting potential problems and anomalies at an early stage. Several methods exist for these purposes, but the majority of them require a disruption of the plant operation, e.g. by shut-down or by perturbation of the system. The knowledge of the noise, i.e. the fluctuations of a parameter around its time-averaged value, can be used for on-line/off-line core monitoring and diagnostics without any disruption of normal operation. Measurements of reactor parameters can be used for estimating dynamical parameters, as the Moderator Temperature Coefficient (MTC) in a Pressurized Water Reactor (PWR), or for detecting anomalies, as unseated fuel assemblies in Boiling Water Reactors (BWRs) or flow blockages.Since the interpretation of the neutron noise aims at finding the driving perturbation responsible for the observed noise in the system and the limited number of detectors makes this attempt difficult, it would be beneficial to be able to numerically estimate in-core noise for any arbitrary noise source so that the comparison between the measured and calculated noise would allow finding the root cause of the observed fluctuations. The intention of this work is thus to calculate the in-core noise for commercial systems using coupled thermal-hydraulic/neutronic models. This includes the determination of the neutron noise, as well as of fluctuations in fuel temperature, moderator density and flow velocity.The work is divided into two main parts, neutron kinetics and thermal-hydraulics. On the neutron kinetic side, P1 and diffusion theories were compared with the conclusion that diffusion theory was accurate enough for noise calculations. The spatial discretization was also tested through the finite difference method and the Analytical Nodal Method (ANM), where it was concluded that both could be used for calculating the neutron noise. The comparisons between those two methods revealed that finite differences seems to be accurate enough for most practical applications. Both methods were successfully validated against analytical solutions.The other part covered in this work was the development for PWRs of a thermal-hydraulic model coupled to the neutronic model. This model was validated against calculations by the commercial Computational Fluid Dynamics (CFD) code FLUENT.The integrated neutronic/thermal-hydraulic model was proven viable and was also benchmarked against a RELAP5/PARCS model of a commercial PWR with mostly good results.
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| 22. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Impact of Trip Length Uncertainty on Optimal Discharging Strategies for PHEVs
- 2010
-
Ingår i: Proceedings of the 6th IFAC Symposium Advances in Automotive Control, Munich; 12 July 2010 through 14 July 2010. - 1474-6670. - 9783902661722 ; , s. 55-60
-
Konferensbidrag (refereegranskat)abstract
- When charged from the electric grid, plug-in Hybrid Electric Vehicles can be expected to have an all electric range of 10 - 60 km depending on battery size. In order to minimize the fuel cost it is vital to fully deplete the battery between two charging occasions. However, when driving distances exceeding the electric range it is in many cases energy efficient to turn on the engine at an early stage and blend power from the battery with power from the combustion engine. This paper studies how uncertainties regarding the predicted trip length affect the optimal discharging strategy of a parallel plug-in Hybrid Electric Vehicle. The predicted trip length along an otherwise perfectly known speed profile is modeled as a normally distributed stochastic variable and Dynamic Programming is used to calculate the optimal discharging strategy. Calculations are carried out for varying standard deviations on three different speed profiles. The results indicate that it is possible to decrease the fuel costs with 1-4 % even with relatively little knowledge regarding the future trip length.
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| 23. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Influence of State of Charge Estimation Uncertainty on Energy Management Strategies for Hybrid Electric Vehicles
- 2011
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902661937 ; 18:PART 1, s. 9703-9708
-
Konferensbidrag (refereegranskat)abstract
- This paper studies how the optimal energy management of a hybrid electric vehicle and a plug-in hybrid electric vehicle is affected by uncertain estimates of the battery state of charge. A simple model for the battery dynamics and the state of charge estimation is postulated, inspired by the known characteristics of previously proposed estimation schemes. Based on the assumption that the drive cycle is perfectly known, the effects of state of charge estimation uncertainty is studied by including the estimation uncertainty in the optimization of the energy management strategy. The simulations indicate lower battery usage and higher fuel consumption as the estimation uncertainty increases.
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| 24. |
- Larsson, Viktor, 1984, et al.
(författare)
-
NEUTRON NOISE CALCULATIONS IN THREE-DIMENSIONAL SYSTEMS
- 2011
-
Ingår i: Proc. of International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering 2011. - 9788563688002
-
Konferensbidrag (refereegranskat)abstract
- In this paper, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in three dimensions and two energy groups using diffusion theory. Cross-sections and other reactor parameters are realistic data coming from a commercial PWR. This work is an extension of a previous model which used finite differences in two dimensions for the spatial discretization. In this work, the calculations are still performed using finite differences for the spatial discretization, but the neutron currents and neutron noise currents are corrected using the Analytical Nodal Method. Another correction is performed by introducing discontinuity factors to improve the modelling of leakages at the face between the fuel assemblies.
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| 25. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Neutron Noise Calculations Using the Analytical Nodal Method
- 2010
-
Ingår i: Proc of PHYSOR 2010 - Advances in Reactor Physics to Power the Nuclear Renaissance, Pittsburgh May 9-14 2010. - 9781617820014 ; 2, s. 939-950
-
Konferensbidrag (refereegranskat)abstract
- In this study, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in 2-group diffusion theory using the Analytical Nodal Method. A brief description of the calculation of the static flux is also included. The static solution is benchmarked against a reference solution in the case of a homogeneous core. The same calculational scheme for the neutron noise as for the static flux is used. As a dynamical benchmark, the calculated neutron noise for a 2D fully homogeneous reactor is compared with the analytical solution, which can easily be determined for homogeneous reactors, at different frequencies. The result of the benchmarks is that the numerical calculations using ANM accurately match the analytical solutions.
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| 26. |
- Larsson, Viktor, 1984, et al.
(författare)
-
Neutron noise calculations using the Analytical Nodal Method and comparisons with analytical solutions
- 2011
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:4, s. 808-816
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the neutron noise, i.e. the stationary fluctuations of the neutron flux around its mean value, is calculated in 2-group diffusion theory using the Analytical Nodal Method. A brief description of the calculation of the static flux is also included. The static solution is benchmarked against a reference solution in the case of a homogeneous core. The same calculational scheme for the neutron noise as for the static flux is used. As a dynamical benchmark, the calculated neutron noise for a 2D fully homogeneous reactor is compared with the analytical solution of a centered noise source at different frequencies. The numerical solution is also benchmarked to an off-centered source where the analytical solution is determined using the power reactor approximation, extended to two energy groups. The results of the benchmarks are that the numerical calculations using ANM accurately match the analytical solutions.
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| 27. |
- Larsson, Viktor, 1984
(författare)
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On Discharge Strategies for Plug-in Hybrid Electric Vehicles
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During recent years electrification of vehicles has emerged as a promisingtechnology to reduce oil dependency and CO2 emissions within the transportationsector. At the present day several automotive manufacturers areabout to introduce plug-in hybrid electric vehicles to the market, i.e. hybridelectric vehicles with high capacity batteries that are grid rechargeable.As with most new technologies this introduces new control problems to besolved by engineers and researchers.This thesis investigates one of these new control problems, namely howto optimally discharge the battery of a plug-in hybrid electric vehicle ontrips that exceed the electric range. Rather than using the trivial dischargestrategy, which is to operate as an electric vehicle until the battery is depletedand then proceed in charge sustaining operation as a conventionalhybrid electric vehicle, it is possible to improve powertrain efficiency if thebattery is discharged gradually throughout the trip. A gradual dischargelowers the average discharge current, thereby lowering the resistive lossesthat are quadratic in current. However, to find a suitable discharge ratesome a priori information regarding the future trip is required.In the thesis it is shown that the a priori information needed can beobtained using route recognition; an algorithm with low computational demandis proposed and evaluated using simulations on logged commuter drivingdata. The results suggest that notable fuel cost reductions are possiblefor commuters that frequently drive along routes that exceed the electricrange. Furthermore, the impact of trip length uncertainty on the optimaldischarge rate is also studied and results indicate that it is preferable tounderestimate rather than overestimate the trip length. A separate investigationconcludes that uncertain estimates of the battery state of chargeonly has minor effects on the optimal discharge rate.
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| 28. |
- Larsson, Viktor, et al.
(författare)
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Rank Minimization with Structured Data Patterns
- 2014
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. - 9783319105772 ; 8691:PART 3, s. 250-265
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Konferensbidrag (refereegranskat)abstract
- The problem of finding a low rank approximation of a given measurement matrix is of key interest in computer vision. If all the elements of the measurement matrix are available, the problem can be solved using factorization. However, in the case of missing data no satisfactory solution exists. Recent approaches replace the rank term with the weaker (but convex) nuclear norm. In this paper we show that this heuristic works poorly on problems where the locations of the missing entries are highly correlated and structured which is a common situation in many applications. Our main contribution is the derivation of a much stronger convex relaxation that takes into account not only the rank function but also the data. We propose an algorithm which uses this relaxation to solve the rank approximation problem on matrices where the given measurements can be organized into overlapping blocks without missing data. The algorithm is computationally efficient and we have applied it to several classical problems including structure from motion and linear shape basis estimation. We demonstrate on both real and synthetic data that it outperforms state-of-the-art alternatives.
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| 29. |
- Larsson, Viktor, 1984
(författare)
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Route Optimized Energy Management of Plug-in Hybrid Electric Vehicles
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plug-in hybrid electric vehicles have the potential to significantly reducethe oil dependence within the transportation sector. However, there willalways be some trips that exceed the electric driving range, meaning thatboth electric energy and fuel must be used. For such trips the fuel economyis intimately connected with the energy management system and its abilityto schedule the use of the battery. The fundamental problem is that theoptimal fuel economy can be reached only if the future trip is known a priori.It is therefore desirable to have a system that can perform three principaltasks: i) acquire a prediction of the future trip, ii) given the predictionprecompute feedforward information for the real-time level, and iii) at thereal-time level identify the optimal operating points in the powertrain.This thesis investigates all three of the mentioned tasks. It is shown thatfrequently travelled routes can be identified from logged driving data usinghierarchical clustering. Based on the historical driving conditions along theroute, it is then possible to precompute an optimal strategy that can be usedas feedforward information for the real-time level. Two different methods forsuch a precomputation are investigated, convex optimization and DynamicProgramming. Particular attention is given to the implementation of acomputationally efficient Dynamic Programming algorithm.A real-time control strategy that is based on a closed-form minimizationof the Hamiltonian is also presented. The strategy is derived for a power-train with two degrees of freedom, and is implemented in a dynamic vehiclemodel that is used by a vehicle manufacturer. Simulations with a linearlydecreasing battery state of charge reference indicate that the fuel economycan be improved with up to 10%, compared to a depleting-sustaining strat-egy. Real-time compatible controller code is also generated and tested in aproduction vehicle. The vehicle behaviour during a test drive is similar tosimulated behaviour
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| 30. |
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| 31. |
- Pourabdollah, Mitra, 1984, et al.
(författare)
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PHEV Energy Management: A Comparison of Two Levels of Trip Information
- 2012
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Konferensbidrag (refereegranskat)abstract
- Plug-in hybrid electric vehicles (PHEVs) have rechargeable energy storage which can be used to run the vehicle on shorter range on electricity from the grid. In the absence of a priori information about the trip, a straightforward strategy is to first deplete the battery down to a minimum level and then keep the state of charge (SoC) around this level. However, largely due to the battery losses, the overall fuel economy can be improved if the battery is discharged gradually. This requires some a priori knowledge about the trip.This paper investigates the tradeoff between improved fuel economy and the need for a priori information. This investigation is done using a variant of telemetry equivalent consumption minimization strategy (T-ECMS) which is modified to be used for a PHEV. To implement this strategy, several parameters need to be tuned based on an assumption of the future trip. By studying two different levels of details, the tradeoff between fuel economy and a priori information is evaluated. It is shown that the proposed strategy improves the fuel economy considerably even when general information is available. However, increase in the details of the a priori information improves the fuel economy even further.
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| 32. |
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