| 1. |
- Alam, Assad, et al.
(författare)
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Look-Ahead Cruise Control for Heavy Duty Vehicle Platooning
- 2013
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Ingår i: Proceedings of the 16th International IEEE Annual Conference onIntelligent Transportation Systems (ITSC 2013). - : IEEE conference proceedings. - 9781479929146 ; , s. 928-935
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Konferensbidrag (refereegranskat)abstract
- Vehicle platooning has become important for thevehicle industry. Yet conclusive results with respect to thefuel reduction possibilities of platooning remain unclear, inparticular when considering constraints imposed by the topography.The focus of this study is to establish whether itis more fuel-efficient to maintain or to split a platoon that isfacing steep uphill and downhill segments. Two commercialcontrollers, an adaptive cruise controller and a look-aheadcruise controller, are evaluated and alternative novel controlstrategies are proposed. The results show that an improvedfuel-efficiency can be obtained by maintaining the platoonthroughout a hill. Hence, a cooperative control strategy basedon preview information is presented, which initiates the changein velocity at a specific point in the road for all vehiclesrather than simultaneously changing the velocity to maintainthe spacing. A fuel reduction of up to 14% can be obtainedover a steep downhill segment and a more subtle benefit of0.7% improvement over an uphill segment with the proposedcontroller, compared to the combination of the commerciallyavailable cruise controller and adaptive cruise controller thatcould be used for platooning. The findings show that it isboth fuel-efficient and desirable in practice to consider previewinformation of the topography in the control strategy.
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| 2. |
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| 3. |
- Börjesson, Karl, 1982, et al.
(författare)
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A Bioinspired Self Assembled Dimeric Porphyrin Pocket that Binds Electron Accepting Ligands
- 2012
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 48:12, s. 1793-1795
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Tidskriftsartikel (refereegranskat)abstract
- A binding pocket consisting of two zinc porphyrins self assembled by Watson-Crick base pairing is presented. The porphyrin binding pocket is located in the confined environment of a lipid membrane whereas the DNA is located in the water phase. Bidentate electron accepting ligands are shown to coordinate in-between the two porphyrins.
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| 4. |
- Börjesson, Karl, 1982, et al.
(författare)
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Functionalized Nanostructures: Redox-Active Porphyrin Anchors for Supramolecular DNA Assemblies
- 2010
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 4:9, s. 5037-5046
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Tidskriftsartikel (refereegranskat)abstract
- We have synthesized and studied a supramolecular system comprising a 39-mer DNA with porphyrin-modified thymidine nucleosides anchored to the surface of large unilamellar vesicles (liposomes). Liposome porphyrin binding characteristics, such as orientation, strength, homogeneity, and binding site size, was determined, suggesting that the porphyrin is well suited as a photophysical and redox-active lipid anchor, in comparison to the inert cholesterol anchor commonly used today. Furthermore, the binding characteristics and hybridization capabilities were studied as a function of anchor size and number of anchoring points, properties that are of importance for our future plans to use the addressability of these redox-active nodes in larger DNA-based nanoconstructs. Electron transfer from photoexcited porphyrin to a lipophilic benzoquinone residing in the lipid membrane was characterized by steady-state and time-resolved fluorescence and verified by femtosecond transient absorption.
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| 5. |
- Liang, Kuo-Yun, 1987-
(författare)
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Coordination and Routing for Fuel-Efficient Heavy-Duty Vehicle Platoon Formation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heavy-duty vehicle (HDV) manufacturers and fleet owners are facing great challenges for a maintained sustainable transport system as the demand for road freight transport is continuously increasing. HDV platooning is one potential solution topartially mitigate the environmental impacts as well as to reduce the fuel consumption, improve safety, and increase the throughput on congested highways. Although the concept of vehicle platooning has existed for decades, it has only been recently possible to implement in practice. Advancement in information and communications technology as well as in on-board technology allow the vehicles to connect with each other and the infrastructure. As goods have different origins, destinations, and time restrictions, it is not evident how the HDVs can fully utilize the platooning benefits during transport missions. There is a need to systematically coordinate scattered vehicles on the road network to form platoons in order to maximize the benefits of platooning. This thesis presents a framework for the coordination of HDV platoon formations. The focus lies on analyzing and validating the possibility to form platoons through fuel-efficient coordination decisions. A functional architecture for goods transport is presented, which divides the overall complex transport system into manageable layers. A vehicle model is developed to compute the impact a coordination decision has on the fuel cost. Platoon coordination consists of rerouting vehicles, adjusting departure times, and adjusting speed profiles. The focus in this thesis is on adjusting vehicles’ speeds through catch-up coordination. The first main contribution of the thesis is the investigation of how and when a pair of vehicles should form platoons given their position, speed, and destination. We derive a break-even ratio where the fuel cost of catching up and platooning is equal to the fuel cost of maintaining the original profile. By comparing the distance to destination and the distance to the candidate vehicle ahead with the break-even ratio, we can conclude whether a catch-up coordination would be beneficial or not. We also show that the road topography has little or no impact on the fuel savings of catch-up coordination. The second contribution is the study of extending the catch-up coordination into a road network with scattered vehicles with the possibility to form platoons and plan routes on junctions. Incoming vehicles on a road junction are aware of other incoming vehicles and of their position, speed, and destination. The vehicles can decide if a platoon should be formed and which path to take. Simulations on the German road network show fuel savings exceeding 5% with a few thousand vehicles. For our third contribution, we use real vehicle probe data obtained from a fleet management system to investigate how catch-up coordination and departure time adjustments can increase the fuel savings from today’s spontaneous platooning. The results show that coordination can increase the fuel savings and the platooning rate significantly. We managed to increase it with a factor of nine despite having only 200–350 active HDVs on the network. The main results of the thesis indicate that it is possible to increase fuel savings noticeably with simple regional coordination schemes for vehicle platoons.
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| 6. |
- Liang, Kuo-Yun, et al.
(författare)
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Fuel-Saving Potentials of Platooning Evaluated through Sparse Heavy-Duty Vehicle Position Data
- 2014
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Konferensbidrag (refereegranskat)abstract
- Vehicle platooning is important for heavy-duty vehicle manufacturers, due to the reduced aerodynamic drag for the follower vehicles, which gives an overall lower fuel consumption. Heavy-duty vehicle drivers are aware this fact and sometimes drive close to other heavy-duty vehicles. However, it is not currently well known how many vehicles are actually driving in such spontaneous platoons today. This paper studies the platooning rate of 1,800 heavy-duty vehicles by analyzing sparse vehicle position data from a region in Europe during one day. Map-matching and path-inference algorithms are used to determine which paths the vehicles took. The spontaneous platooning rate is found to be 1.2 %, which corresponds to a total fuel saving of 0.07% compared to if none of the vehicles were platooning. Furthermore, we introduce several virtual coordination schemes. We show that coordinations can increase the platooning rate and fuel saving with a factor of ten with minor adjustments from the current travel schedule. The platooning rate and fuel savings can be significantly greater if higher flexibility is allowed.
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| 7. |
- Madjidian, Daria, et al.
(författare)
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A Distributed Power Coordination Scheme for Fatigue Load Reduction in Wind Farms
- 2011
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Ingår i: ; , s. 5219-5224
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Konferensbidrag (refereegranskat)abstract
- Wind turbines operating in wind farms are coupled by the wind flow. This coupling results in increased turbulence levels for downwind turbines, and consequently higher maintenance costs. In this paper, we consider a scenario where a wind farm is asked to produce less than maximum power. The objective is to minimize fatigue loads on the turbines, while maintaining the desired power production. We show how this can be achieved by coordinating neighboring turbines. The result is a control structure where each turbine only need to communicate with a limited set of neighboring turbines. Moreover, the synthesis of the controllers is also distributed.
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| 8. |
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| 9. |
- Mårtensson, Karl, et al.
(författare)
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A Scalable Modularized Synthesis Method for Distributed Kalman Filters
- 2011
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Konferensbidrag (refereegranskat)abstract
- This paper presents a scheme to construct distributed observers for a system consisting of agents interconnected in a graph structure. The scheme is an iterative procedure to improve the observers with respect to global performance. It is modular in the sense that each agent iterates using only local model information. As a consequence, the complexity of the scheme scales linearly with the size of the system. The resulting observers estimate states for each agent using only local measurements and model knowledge of its neighbors. Distributed observers are suboptimal to centralized ones and it is desirable to measure the amount of performance degradation. We show how to use the variables of the synthesis scheme to also determine such a measure of the suboptimality.
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| 10. |
- Mårtensson, Karl, et al.
(författare)
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Distributed resource management using iterative gradient update synthesis
- 2011
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Ingår i: ; , s. 3435-3440
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Konferensbidrag (refereegranskat)abstract
- We consider load balancing on a network. Servers of limited bandwidth move a single commodity through a network of buffers (or queues) while external random processes generate and consume this commodity. Our contribution is a distributed algorithm for regulating the backlogs of these queues to a given reference while balancing the mean flow in the network. We formulate this as a fluid buffer regulation problem and use distributed gradient descent to update the feedback gains for an LQG controller. Our proposed distributed algorithm both implicitly and explicitly estimates the statistics of the external process flows using only local information on fixed time intervals and updates the feedback matrix for the regulator accordingly. We demonstrate our method on a simulation of an industrial floor where autonomous vehicles remove palettes from production line buffers.
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| 11. |
- Mårtensson, Karl
(författare)
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Gradient Methods for Large-Scale and Distributed Linear Quadratic Control
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis considers methods for synthesis of linear quadratic controllers for large-scale, interconnected systems. Conventional methods that solve the linear quadratic control problem are only applicable to systems with moderate size, due to the rapid increase in both computational time and memory requirements as the system size increases. The methods presented in this thesis show a much slower increase in these requirements when faced with system matrices with a sparse structure. Hence, they are useful for control design for systems of large order, since they usually have sparse systems matrices. An equally important feature of the methods is that the controllers are restricted to have a distributed nature, meaning that they respect a potential interconnection structure of the system. The controllers considered in the thesis have the same structure as the centralized LQG solution, that is, they are consisting of a state predictor and feedback from the estimated states. Strategies for determining the feedback matrix and predictor matrix separately, are suggested. The strategies use gradient directions of the cost function to iteratively approach a locally optimal solution in either problem. A scheme to determine bounds on the degree of suboptimality of the partial solution in every iteration, is presented. It is also shown that these bounds can be combined to give a bound on the degree of suboptimality of the full output feedback controller. Another method that treats the synthesis of the feedback matrix and predictor matrix simultaneously is also presented. The functionality of the developed methods is illustrated by an application, where the methods are used to compute controllers for a large deformable mirror, found in a telescope to compensate for atmospheric disturbances. The model of the mirror is obtained by discretizing a partial differential equation. This gives a linear, sparse representation of the mirror with a very large state space, which is suitable for the methods presented in the thesis. The performance of the controllers is evaluated using performance measures from the adaptive optics community.
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| 12. |
- Mårtensson, Karl, et al.
(författare)
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Sub-Optimality Bound on a Gradient Method for Iterative Distributed Control Synthesis
- 2010
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Konferensbidrag (refereegranskat)abstract
- A previous paper introduced an online gradient method to iteratively update local controllers for improved performance. In this paper we modify that method to get an offline method for distributed control synthesis. The complexity of the method is linear in the number of neighbors to each agent. Since the controllers are constructed to be distributed and the method is an iterative scheme, the controllers will always be sub-optimal compared to a centralized controller. We describe a method to calculate bounds of the sub-optimality of the controllers, using the same variables that take part in the update scheme.
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| 13. |
- Turri, Valerio, et al.
(författare)
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Fuel-efficient heavy-duty vehicle platooning by look-ahead control
- 2014
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Ingår i: Decision and Control (CDC), 2014 IEEE 53rd Annual Conference on. - : IEEE conference proceedings. - 9781479977468 ; , s. 654-660
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Konferensbidrag (refereegranskat)abstract
- The operation of groups of heavy-duty vehicles at close intervehicular distances (known as platoons) has been shown to be an effective way of reducing fuel consumption. For single vehicles, it is also known that the availability of preview information on the road topography can be exploited to obtain fuel savings. The current paper aims at the inclusion of preview information in platooning by introducing a two-layer control system architecture for so-called look-ahead platooning. Here, the layers are responsible for the inclusion of preview information and real-time vehicle control for platooning, respectively. Within this framework, a control strategy is presented, where dynamic programming is used for the calculation of fuel-optimal speed profiles, while a model predictive control approach is exploited for the real-time vehicle control. The feasibility of this approach is illustrated by means of the simulation of relevant scenarios.
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