| 1. |
- Biel, Martin, et al.
(författare)
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SiMpLIfy : A toolbox for structured model reduction
- 2015
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Ingår i: 2015 European Control Conference, ECC 2015. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783952426937 ; , s. 1159-1164
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present a toolbox for structured model reduction developed for MATLAB. In addition to structured model reduction methods using balanced realizations of the subsystems, we introduce a numerical algorithm for structured model reduction using a subgradient optimization algorithm. We briefly present the syntax for the toolbox and its features. Finally, we demonstrate the applicability of various model reduction methods in the toolbox on a structured mass-spring mechanical system.
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| 2. |
- Farhad, Farokhi, et al.
(författare)
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A piecewise-constant congestion taxing policy for repeated routing games
- 2015
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Ingår i: Transportation Research Part B. - : Elsevier BV. - 0191-2615 .- 1879-2367. ; 78, s. 123-143
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider repeated routing games with piecewise-constant congestion taxing in which a central planner sets and announces the congestion taxes for fixed windows of time in advance. Specifically, congestion taxes are calculated using marginal congestion pricing based on the flow of the vehicles on each road prior to the beginning of the taxing window (and, hence, there is a time-varying delay in setting the congestion taxes). We motivate the piecewise-constant taxing policy by that users or drivers may dislike fast-changing prices and that they also prefer prior knowledge of the prices. We prove for this model that the multiplicative update rule and the discretized replicator dynamics converge to a socially optimal flow when using vanishing step sizes. Considering that the algorithm cannot adapt itself to a changing environment when using vanishing step sizes, we propose adopting constant step sizes in this case. Then, however, we can only prove the convergence of the dynamics to a neighborhood of the socially optimal flow (with the size of the neighbourhood being of the order of the selected step size). The results are illustrated on a nonlinear version of Pigou's famous routing game.
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| 3. |
- Farokhi, Farhad, 1987-, et al.
(författare)
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A Game-Theoretic Framework for Studying Truck Platooning Incentives
- 2013
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Ingår i: Proceedings of the 16th International IEEE Annual Conference on Intelligent Transportation Systems (ITSC 2013). - : IEEE conference proceedings. ; , s. 1253-1260
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Konferensbidrag (refereegranskat)abstract
- An atomic congestion game with two types of agents, cars and trucks, is used to model the traffic flow on a road over certain time intervals. In this game, the drivers make a trade-off between the time they choose to use the road, the average velocity of the flow at that time, and the dynamic congestion tax that they are paying to use the road. The trucks have platooning capabilities and therefore, have an incentive for using the road at the same time as their peers. The dynamics and equilibria of this game-theoretic model for the interaction between car traffic and truck platooning incentives are investigated. We use traffic data from Stockholm to validate the modeling assumptions and extract reasonable parameters for the simulations. We perform a comprehensive simulation study to understand the influence of various factors, such as the percentage of the trucks that are equipped with platooning devices on the properties of the pure strategy Nash equilibrium that is learned using a joint strategy fictitious play.
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| 4. |
- Farokhi, Farhad, 1987-, et al.
(författare)
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A Heterogeneous Routing Game
- 2013
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Ingår i: 2013 51st Annual Allerton Conference on Communication, Control, and Computing, Allerton 2013. - : IEEE conference proceedings. - 9781479934096 ; , s. 448-455
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Konferensbidrag (refereegranskat)abstract
- Most literature on routing games make the assumption that drivers or vehicles are of the same type and, hence, experience the same latency or cost when traveling along the edges of the network. In contrast, in this article, we propose a heterogeneous routing game in which each driver or vehicle belongs to a certain type. The type determines the cost of traveling along an edge as a function of the flow of all types of drivers or vehicles over that edge. We examine the existence of a Nash equilibrium in this heterogeneous routing game. We study the conditions for which the problem of finding a Nash equilibrium can be posed as a convex optimization problem and is therefore numerically tractable. Numerical simulations are presented to validate the results.
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| 5. |
- Farokhi, Farhad, et al.
(författare)
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A Robust Control-Design Method Using Bode’s Ideal Transfer Function
- 2011
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Ingår i: Proceedings of the 19th Mediterranean Conference on Control and Automation. - : IEEE conference proceedings. - 9781457701245 ; , s. 712-717
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Konferensbidrag (refereegranskat)abstract
- We propose a method for designing loop-shaping controllers using Bode's ideal transfer function. Bode's ideal transfer function is introduced using fractional calculus. The ideal loop transfer function is approximated using the first generation CRONE approximation, and then implemented by means of Hinfinity-optimization followed by closed-loop controller order reduction of the resulting controller. The design method is confirmed to be powerful and robust by simulating on a flexible transmission system.
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| 6. |
- Farokhi, Farhad, 1987-, et al.
(författare)
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A Study of Truck Platooning Incentives Using a Congestion Game
- 2015
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Ingår i: IEEE transactions on intelligent transportation systems (Print). - 1524-9050 .- 1558-0016. ; 16:2, s. 581-595
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Tidskriftsartikel (refereegranskat)abstract
- We introduce an atomic congestion game with two types of agents, namely, cars and trucks, to model the traffic flow on a road over various time intervals of the day. Cars maximize their utility by finding a tradeoff between the time they choose to use the road, the average velocity of the flow at that time, and the dynamic congestion tax that they pay for using the road. In addition to these terms, the trucks have an incentive for using the road at the same time as their peers because they have platooning capabilities, which allow them to save fuel. The dynamics and equilibria of this game-theoretic model for the interaction between car traffic and truck platooning incentives are investigated. We use traffic data from Stockholm, Sweden, to validate parts of the modeling assumptions and extract reasonable parameters for the simulations. We use joint strategy fictitious play and average strategy fictitious play to learn a pure strategy Nash equilibrium of this game. We perform a comprehensive simulation study to understand the influence of various factors, such as the drivers' value of time and the percentage of the trucks that are equipped with platooning devices, on the properties of the Nash equilibrium.
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| 7. |
- Farokhi, Farhad, et al.
(författare)
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Adaptive control design under structured model information limitation : A cost-biased maximum-likelihood approach
- 2015
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Ingår i: Systems & control letters (Print). - : Elsevier BV. - 0167-6911 .- 1872-7956. ; 75, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- Networked control strategies based on limited information about the plant model usually result in worse closed-loop performance than optimal centralized control with full plant model information. Recently, this fact has been established by utilizing the concept of competitive ratio, which is defined as the worst-case ratio of the cost of a control design with limited model information to the cost of the optimal control design with full model information. We show that an adaptive controller, inspired by a controller proposed by Campi and Kumar, with limited plant model information, asymptotically achieves the closed-loop performance of the optimal centralized controller with full model information for almost any plant. Therefore, there exists, at least, one adaptive control design strategy with limited plant model information that can achieve a competitive ratio equal to one. The plant model considered in the paper belongs to a compact set of stochastic linear time-invariant systems and the closed-loop performance measure is the ergodic mean of a quadratic function of the state and control input.
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| 8. |
- Farokhi, Farhad, 1987-, et al.
(författare)
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Complexity Reduction for Parameter-Dependent Linear Systems
- 2013
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Ingår i: 2013 American Control Conference (ACC). - : American Automatic Control Council. - 9781479901777 ; , s. 2624-2630
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Konferensbidrag (refereegranskat)abstract
- We present a complexity reduction algorithm for a family of parameter-dependent linear systems when the system parameters belong to a compact semi-algebraic set. This algorithm potentially describes the underlying dynamical system with fewer parameters or state variables. To do so, it minimizes the distance (i.e., $H_\infty$-norm of the difference) between the original system and its reduced version. We present a sub-optimal solution to this problem using sum-of-squares optimization methods. We present the results for both continuous-time and discrete-time systems. Lastly, we illustrate the applicability of our proposed algorithm on numerical examples.
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| 9. |
- Farokhi, Farhad, et al.
(författare)
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Control Design with Limited Model Information
- 2011
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Ingår i: Proceedings of the 2011 American Control Conference. - : AACC. - 9781457700804 ; , s. 4697-4704
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Konferensbidrag (refereegranskat)abstract
- We introduce the family of limited model information control design methods, which construct controllers by accessing the plant’s model in a constrained way, according to a given design graph. This class generalizes the notion of communication-less control design methods recently introduced by one of the authors, which construct each sub-controller using only local plant model information. We study the tradeoff between the amount of model information exploited by a control design method and the quality of controllers it can produce. In particular, we quantify the benefit (in terms of the competitive ratio and domination metrics) of giving the control designer access to the global interconnection structure of the plant-to-be-controlled, in addition to local model information.
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| 10. |
- Farokhi, Farhad, et al.
(författare)
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Cooperation Patterns between Fleet Owners for Transport Assignments
- 2015
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Ingår i: 2015 IEEE CONFERENCE ON CONTROL AND APPLICATIONS (CCA 2015), IEEE conference proceedings. - : IEEE. - 9781479977871 ; , s. 1124-1129
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Konferensbidrag (refereegranskat)abstract
- We study cooperation patterns between the heavy- duty vehicle fleet owners to reduce their costs, improve their fuel efficiency, and decrease their emissions. We consider a distributed cooperation pattern in which the fleet owners can communicate directly with each other to form alliances. A centralized cooperation pattern is studied in which the fleet owners pay to subscribe to a third-party service provider that pairs their vehicles for cooperation. The effects of various pricing strategies on the behaviour of fleet owners and their inclusiveness are analyzed. It is shown that the fleet size has an essential role.
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