| 1. |
- Al Alam, Assad, et al.
(författare)
-
An experimental study on the fuel reduction potential of heavy duty vehicle platooning
- 2010
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Ingår i: 13th International IEEE Conference on Intelligent Transportation Systems (ITSC), 2010. - : IEEE. ; , s. 306-311
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Konferensbidrag (refereegranskat)abstract
- Vehicle platooning has become important for the vehicle industry. Yet conclusive results with respect to the fuel reduction possibilities of platooning remain unclear. The focus in this study is the fuel reduction that heavy duty vehicle platooning enables and the analysis with respect to the influence of a commercial adaptive cruise control on the fuel consumption. Experimental results show that by using preview information of the road ahead from the lead vehicle, the adaptive cruise controller can reduce the fuel consumption. A study is undertaken for various masses of the lead vehicle. The results show that the best choice with respect to a heavier or lighter lead vehicle depends on the desired time gap. A maximum fuel reduction of 4.7-7.7% depending on the time gap, at a set speed of 70 km/h, can be obtained with two identical trucks. If the lead vehicle is 10 t lighter a corresponding 3.8-7.4% fuel reduction can be obtained depending on the time gap. Similarly if the lead vehicle is 10 t heavier a 4.3-6.9% fuel reduction can be obtained. All results indicate that a maximum fuel reduction can be achieved at a short relative distance, due to both air drag reduction and suitable control.
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| 2. |
- Al Alam, Assad, et al.
(författare)
-
Establishing safety for heavy duty vehicle platooning : a game theoretical approach
- 2011
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). ; , s. 3818-3823
-
Konferensbidrag (refereegranskat)abstract
- It is fuel efficient to minimize the relative distance between vehicles to achievea maximum reduction in air drag. However, the relative distance can only be reduced to acertain extent without endangering a collision. Factors such as the vehicle velocity, the relativevelocity, and the characteristics of the vehicle ahead has a strong impact on what minimumrelative distance can be obtained. In this paper, we utilize optimal control and game theory toestablish safety criteria for heavy duty vehicle platooning applications. The derived results showthat a minimum relative distance of 1.2m can be obtained for two identical vehicles withoutendangering a collision, assuming that there is no delay present in the feedback system. If aworst case delay is present in the system, a minimum relative distance is deduced based uponthe vehicle’s maximum deceleration ability. The relative distance can be reduced if the followervehicle has a greater overall braking capability, which suggests that vehicle heterogeneity andorder has substantial impact. The findings are verified by simulations and the main conclusion isthat the relative distance utilized in commercial applications today can be reduced significantlywith a suitable advanced cruise control system.
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| 3. |
- Alam, Assad, 1982-
(författare)
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Fuel-Efficient Distributed Control for Heavy Duty Vehicle Platooning
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Freight transport demand has escalated and will continue to do so as economiesgrow. As the traffic intensity increases, the drivers are faced with increasinglycomplex tasks and traffic safety is a growing issue. Simultaneously, fossil fuel usageis escalating. Heavy duty vehicle (HDV) platooning is a plausible solution to theseissues. Even though there has been a need for introducing automated HDV platooningsystems for several years, they have only recently become possible to implement.Advancements in on-board and external technology have ushered in new possibilitiesto aid the driver and enhance the system performance. Each vehicle is able to serveas an information node through wireless communication; enabling a cooperativenetworked transportation system. Thereby, vehicles can semi-autonomously travel atshort intermediate spacings, effectively reducing congestion, relieving driver tension,improving fuel consumption and emissions without compromising safety. This thesis presents contributions to a framework for the design and implementation of HDV platooning. The focus lies mainly on establishing and validating realconstraints for fuel optimal control for platooning vehicles. Nonlinear and linearvehicle models are presented together with a system architecture, which dividesthe complex problem into manageable subsystems. The fuel reduction potentialis investigated through simulation models and experimental results derived fromstandard vehicles traveling on a Swedish highway. It is shown through analyticaland experimental results that it is favorable with respect to the fuel consumption tooperate the vehicles at a much shorter intermediate spacing than what is currentlydone in commercially available systems. The results show that a maximum fuelreduction of 4.7–7.7 % depending on the inter-vehicle time gap, at a set speedof 70 km/h, can be obtained without compromising safety. A systematic designmethodology for inter-vehicle distance control is presented based on linear quadraticregulators (LQRs). The structure of the controller feedback matrix can be tailoredto the locally available state information. The results show that a decentralizedcontroller gives good tracking performance, a robust system and lowers the controleffort downstream in the platoon. It is also shown that the design methodologyproduces a string stable system for an arbitrary number of vehicles in the platoon,if the vehicle configurations and the LQR weighting parameters are identical for theconsidered subsystems. With the results obtained in this thesis, it is argued that a vast fuel reductionpotential exists for HDV platooning. Present commercial systems can be enhancedsignificantly through the introduction of wireless communication and decentralizedoptimal control.
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| 4. |
- Alam, Assad, et al.
(författare)
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Guaranteeing safety for heavy duty vehicle platooning : Safe set computations and experimental evaluations
- 2014
-
Ingår i: Control Engineering Practice. - : Elsevier. - 0967-0661 .- 1873-6939. ; 24:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the problem of finding a safety criteria between neighboring heavy duty vehicles traveling in a platoon. We present a possible framework for analyzing safety aspects of heavy duty vehicle platooning. A nonlinear underlying dynamical model is utilized, where the states of two neighboring vehicles are conveyed through radar information and wireless communication. Numerical safe sets are derived through the framework, under a worst-case scenario, and the minimum safe spacing is studied for heterogenous platoons. Real life experimental results are presented in an attempt to validate the theoretical results in practice. The findings show that a minimum relative distance of 1.2 m at maximum legal velocity on Swedish highways can be maintained for two identical vehicles without endangering a collision. The main conclusion is that the relative distance utilized in commercial applications today can be reduced significantly with a suitable automatic control system.
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| 5. |
- Alam, Assad, 1982-, et al.
(författare)
-
Suboptimal Decentralized Controller Design for Chain Structures : Applications to Vehicle Formations
- 2011
-
Ingår i: IEEE 50th Annual Conference on Decision and Control and European Control Conference, Orlando, December, 2011. - : IEEE. ; , s. 6894-6900
-
Konferensbidrag (refereegranskat)abstract
- We consider suboptimal decentralized controllerdesign for subsystems with interconnected dynamics and costfunctions. A systematic design methodology is presented overthe class of linear quadratic regulators (LQR) for chain graphs.The methodology is evaluated on heavy duty vehicle platooningwith physical constraints. A simulation and frequency analysisis performed. The results show that the decentralized controllergives good tracking performance and a robust system. We alsoshow that the design methodology produces a string stablesystem for an arbitrary number of vehicles in the platoon, ifthe vehicle configurations and the LQR weighting parametersare identical for the considered subsystems.
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| 6. |
- Farokhi, Farhad, 1987-
(författare)
-
Decentralized Control Design with Limited Plant Model Information
- 2012
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Large-scale control systems are often composed of several smaller interconnected units. For these systems, it is common to employ local controllers, which observe and act locally. At the heart of common control design procedures for distributed systems lies the often implicit assumption that the designer has access to the global plant model information when designing a local controller. However, there are several reasons why such plant model information would not be globally known. One reason could be that the designer wants the parameters of each local controller to only depend on local model information, so that the controllers are not modified if the model parameters of a particular subsystem change. It might also be the case that the design of each local controller is done by individual designers with no access to the global plant model, for instance, due to the fact that the designers refuse to share their model information since they consider it private. This class of problems, which we refer to as limited model information control design, is the topic of the thesis. First, we investigate the achievable closed-loop performance of discrete-time linear time-invariant plants under a separable quadratic cost performance with structured static state-feedback controllers. To do so, we introduce control design strategies as mappings, which construct controllers by accessing the plant model information in a constrained way according to a given design graph. We compare control design strategies using the competitive ratio as a performance metric, that is, we compare the worst case control performance for a given design strategy normalized with the optimal control performance based on full model information. An explicit minimizer of the competitive ratio is sought. As this minimizer might not be unique, we further search for the ones that are undominated, that is, there is no other control design strategy in the set of limited model information design strategies with a better closed-loop performance for all possible plants while maintaining the same worst-case ratio. We study the trade-off between the amount of model information exploited by a control design strategy and the best possible closed-loop performance. We generalize this setup to structured dynamic state-feedback controllers for H_2-performance. Surprisingly, the optimal control design strategy with limited model information is still a static one. This is the case even though the optimal decentralized state-feedback controller with full model information is dynamic. Finally, we discuss the design of dynamic controllers for disturbance accommodation under limited model information. This problem is of special interest because the best limited model information control design in this case is a dynamic control design strategy. The optimal controller can be separated into a static feedback law and a dynamic disturbance observer. For constant disturbances, it is shown that this structure corresponds to proportional-integral control.
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| 7. |
- Feyzmahdavian, Hamid Reza, et al.
(författare)
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Distributed Output-Feedback LQG Control with Delayed Information Sharing
- 2012
-
Ingår i: Estimation and Control of Networked Systems, Volume 3, Part 1.
-
Konferensbidrag (refereegranskat)abstract
- This paper develops a controller synthesis method for distributed LQG controlproblems under output-feedback. We consider a system consisting of three interconnected linearsubsystems with a delayed information sharing structure. While the state-feedback case haspreviously been solved, the extension to output-feedback is nontrivial as the classical separationprinciple fails. To nd the optimal solution, the controller is decomposed into two independentcomponents: a centralized LQG-optimal controller under delayed state observations, and a sumof correction terms based on additional local information available to decision makers. Explicitdiscrete-time equations are derived whose solutions are the gains of the optimal controller.
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| 8. |
- Feyzmahdavian, Hamid Reza, et al.
(författare)
-
Optimal Distributed Controller Design with Communication Delays : Application to vehicle formations
- 2012
-
Ingår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC). - : IEEE conference proceedings. - 9781467320665 ; , s. 2232-2237
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of optimal distributed control with delayed information sharing over chain structures motivated by applications of heavy duty vehicle platooning. We introduce a novel approach to find distributed controllers that take into account communication delays and correlation between the dynamic interconnection. The design decomposes the solution into separate optimization problems. The results show that a tight control is achieved, even in the presence of delays, and behaves well with respect to the imposed disturbances. The computed theoretical cost of the proposed optimal controller is significantly better than the theoretical cost for the centralized control with a global delay and close to the cost for a fully centralized control with full state information at all times.
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| 9. |
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| 10. |
- Gattami, Ather, et al.
(författare)
-
A frequency domain condition for stability of interconnected MIMO systems
- 2004
-
Ingår i: Proceedings of the 2004 American Control Conference. - 0780383354 ; , s. 3723-3728
-
Konferensbidrag (refereegranskat)abstract
- Analysis of interconnected dynamical systems is considered. A framework for the analysis of stability of the interconnection is given. The results of Fax and Murray that studies the SISO-case for a constant interconnection matrix are generalized to the MIMO-case where arbitrary interconnection is allowed. The analysis shows the existence of a separation principle that is very useful in the sense of the simplicity for stability analysis. Stability could be checked graphically using a Nyquist-like criterion. The problem with time-delays and interconnection variation and robustness appear to be natural special cases of the general framework, and hence, simple stability criteria are derived easily
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| 11. |
- Gattami, Ather, 1981-
(författare)
-
Deterministic Team Problems with Signaling
- 2011
-
Ingår i: 2011 50th IEEE Conference on Decision and Control andEuropean Control Conference (CDC-ECC). ; , s. 5529-5534
-
Konferensbidrag (refereegranskat)abstract
- This paper considers linear quadraticteam decision problems where the players inthe team affect each others information structurethrough their decisions. It shows that linear decisionsare optimal and can be found by solving alinear matrix inequality.
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| 12. |
- Gattami, Ather
(författare)
-
Distributed Stochastic Control: A Team Theoretic Approach
- 2006
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of stochastic control under constraints on the information structure. We review some old results from static team theory, where new simple proofs are given. The signaling phenomenon in distributed optimal linear quadratic Gaussian control plays a central role because of the NP-hardness it implicates. Necessary and sufficient conditions for eliminating the signaling incentive are given in terms of the interconnection structure.
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| 13. |
- Gattami, Ather
(författare)
-
Feedback Capacity of Gaussian Channels Revisited
- 2019
-
Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 65:3, s. 1948-1960
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we revisit the problem of finding the average capacity of the Gaussian feedback channel. First, we consider the problem of finding the average capacity of the analog Gaussian noise channel where the noise has an arbitrary spectral density. We introduce a new approach to the problem where we solve the problem over a finite number of transmissions and then consider the limit of an infinite number of transmissions. Further, we consider the important special case of stationary Gaussian noise with finite memory. We show that the channel capacity at stationarity can be found by solving a semi-definite program, and hence computationally tractable. We also give new proofs and results of the non stationary solution which bridges the gap between results in the literature for the stationary and non stationary feedback channel capacities. It’s shown that a linear communication feedback strategy is optimal. Similar to the solution of the stationary problem, it’s shown that the optimal linear strategy is to transmit a linear combination of the information symbols to be communicated and the innovations for the estimation error of the state of the noise process.
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| 14. |
- Gattami, Ather
(författare)
-
Generalized Linear Quadratic Control
- 2010
-
Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 55:1, s. 131-136
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of stochastic finite- and infinite- horizon linear quadratic control under power constraints. The calculations of the optimal control law can be done off-line as in the classical linear quadratic Gaussian control theory using dynamic programming, which turns out to be a special case of the new theory developed in this technical note. A numerical example is solved using the new methods.
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| 15. |
- Gattami, Ather
(författare)
-
Generalized linear quadratic control theory
- 2006
-
Ingår i: Proceedings of the 45th IEEE Conference on Decision and Control (IEEE Cat. No. 06CH37770). - 1424401704 ; , s. 1510-1514
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of stochastic control under power constraints. Problems such as linear quadratic optimal control with information constraints are instances of the problem considered. The calculations of the optimal control law can be done off-line as in the classical linear quadratic Gaussian control theory using dynamic programming, which turns out to be a special case of the new theory developed in this paper
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| 16. |
- Gattami, Ather, et al.
(författare)
-
Linear Quadratic Performance Criteria for Cascade Control
- 2005
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Ingår i: Decision and Control, 2005 and 2005 European Control Conference. CDC-ECC '05. - 0780395670 ; , s. 3632-3637
-
Konferensbidrag (refereegranskat)abstract
- In this paper we consider the problem of linear quadratic regulator (LQR) performance for cascade control structures of series coupled systems. The necessary and sufficient condition for the linear quadratic performance of a cascade control structure to achieve the same performance as any given centralized LQR is obtained. The cascade problem could be seen as a special case of the network control problem with a special network structure. The results presented show that decentralized control is possible with some natural fundamental limitations in this particular case. Also, a constructive proof is given for the inverse LQR problem that can be used to calculate the decentralized LQR from a given centralized one.
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| 17. |
- Gattami, Ather, et al.
(författare)
-
Minimax Team Decision Problems
- 2007
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Ingår i: ; , s. 4333-4338, s. 766-771
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of distributed decision making in a quadratic game between a "team" of players and nature. Each player has limited information that could be different from the other players in the team. We show that if there is a solution to the minimax team problem, then the linear policies are optimal, and we show how to find the linear optimal solution by solving a linear matrix inequality. The result is used to solve the distributed H infinity control problem. It shows that the information structure restricted to exchange information with neighbours only, is enough to obtain a linear optimal feedback law.
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| 18. |
- Gattami, Ather
(författare)
-
Optimal Decisions with Limited Information
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis considers static and dynamic team decision problems in both stochastic and deterministic settings. The team problem is a cooperative game, where a number of players make up a team that tries to optimize a given cost induced by the uncertainty of nature. The uncertainty is modeled as either stochastic, which gives the stochastic team problem, or modelled as deterministic where the team tries to optimize the worst case scenario. Both the stochastic and deterministic static team problems are stated and solved in a linear quadratic setting. It is shown that linear decisions are optimal in both the stochastic and deterministic framework. The dynamic team problem is formulated using well known results from graph theory. The dynamic interconnection structure is described by a graph. It appears natural to use a graph theoretical formulation to examine how a decision by a member of the team affects the rest of the members. Conditions for tractability of the dynamic team problem are given in terms of the graph structure. Tractability of a new class of information constrained team problems is shown, which extends existing results. For the presented tractable classes, necessary and sufficient conditions for stabilizability are given. The state feedback $mathcal{H}_2$ and $mathcal{H}_{infty}$ dynamic team problems are solved using a novel approach. The new approach is based on the crucial idea of disturbance feedback, which is used to separate the controller effect from the measured output, to eliminate the controller's dual role. Finally, a generalized stochastic linear quadratic control problem is considered. A broad class of team problems can be modeled by imposing quadratic constraints of correlation type. Also, power constraints on the control signals are very common. This motivates the development of a generalized control theory for both the finite and infinite horizon case, where power constraints are imposed. It is shown that the solution can be found using finite dimensional convex optimization.
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| 19. |
- Gattami, Ather, et al.
(författare)
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Robust Team Decision Theory
- 2012
-
Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 57:3, s. 794-798
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Tidskriftsartikel (refereegranskat)abstract
- This technical note considers linear quadratic team decision problems. It shows that linear decisions are optimal and can be found by solving a linear matrix inequality.
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| 20. |
- Gattami, Ather, et al.
(författare)
-
Stabilization of Vehicle Formations-A Case Study
- 2005
-
Ingår i: Book of Abstracts of Third Swedish Workshop on Autonomous Robotics. - 1650-1942.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work treats a specific multi-vehicle control case, namely six vehicles on the Multi-Vehicle Wireless Testbed (MTWT), wich is an arena at Caltech, California, built for doing experiments on small vehicles. A model is set up and a controller is found through simulations that stabilizes the system. Stability is proven through a Nyquist-like criterion.
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| 21. |
- Gattami, Ather, et al.
(författare)
-
Time localization and capacity of faster-than-nyquist signaling
- 2015
-
Ingår i: 2015 IEEE Global Communications Conference, GLOBECOM 2015. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479959525
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we consider communication over the bandwidth limited analog white Gaussian noise channel using non-orthogonal pulses. In particular, we consider non-orthogonal transmission by signaling samples at a rate higher than the Nyquist rate. Using the faster-than- Nyquist (FTN) framework, Mazo showed that one may transmit symbols carried by sinc pulses at a higher rate than that dictated by Nyquist without loosing bit error rate. However, as we will show in this paper, such pulses are not necessarily well localized in time. In fact, assuming that signals in the FTN framework are well localized in time, one can construct a signaling scheme that violates the Shannon capacity bound. We also show directly that FTN signals are in general not well localized in time. We also consider FTN signaling in the case of pulses that are different from the sinc pulses. We show that one may use a precoding scheme of low complexity, in order to remove the intersymbol interference. This leads to the possibility of increasing the number of transmitted samples per time unit and compensate for spectral inefficiency due to signaling at the Nyquist rate of the non sinc pulses. We demonstrate the power of the precoding scheme by simulations.
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| 22. |
- Karlsson, Johannes, et al.
(författare)
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Iterative Source-Channel Coding Approach to Witsenhausen's Counterexample
- 2011
-
Ingår i: Proceedings of the American Control Conference. - NEW YORK : IEEE. - 9781457700811 ; , s. 5348-5353
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Konferensbidrag (refereegranskat)abstract
- In 1968, Witsenhausen introduced his famous counterexample where he showed that even in the simple linear quadratic static team decision problem, complex nonlinear decisions could outperform any given linear decision. This problem has served as a benchmark problem for decades where researchers try to achieve the optimal solution. This paper introduces a systematic iterative source-channel coding approach to solve problems of the Witsenhausen Counterexample-character. The advantage of the presented approach is its simplicity. Also, no assumptions are made about the shape of the space of policies. The minimal cost obtatined using the introduced method is 0.16692462, which is the lowest known thus far.
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| 23. |
- Khorsand, Omid, et al.
(författare)
-
A Decentralized Stabilization Scheme for a Class of Large-scale Interconnected Systems
- 2011
-
Ingår i: Proceedings of the 18th IFAC World Congress, 2011. Volume 18, Part 1.
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a decentralized control approach for a class of large-scale interconnected systems is proposed. A set of local decentralized controllers is constructed to guarantee the stability of the global system utilizing the notion of superstability. The control scheme and design are based on local state information and model knowledge of the adjacent subsystems. The approach leads to a computationally ecient method where the design procedure is performed on the subsystem level using linear programming. The solutions have been optimized and it is shown that the scheme has some useful features such as monotonic convergence and robustness under interval matrix uncertainty.
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| 24. |
- Khorsand, Omid, et al.
(författare)
-
Optimal distributed controller synthesis for chain structures applications to vehicle formations
- 2012
-
Ingår i: ICINCO 2012 - Proceedings of the 9th International Conference on Informatics in Control, Automation and Robotics. - 9789898565211 ; , s. 218-223
-
Konferensbidrag (refereegranskat)abstract
- We consider optimal distributed controller synthesis for an interconnected system subject to communication constraints, in linear quadratic settings. Motivated by the problem of finite heavy duty vehicle platooning, we study systems composed of interconnected subsystems over a chain graph. By decomposing the system into orthogonal modes, the cost function can be separated into individual components. Thereby, derivation of the optimal controllers in state-space follows immediately. The optimal controllers are evaluated under the practical setting of heavy duty vehicle platooning with communication constraints. It is shown that the performance can be significantly improved by adding a few communication links. The results show that the proposed optimal distributed controller outperforms a suboptimal controller in terms of control input energy.
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| 25. |
- Kjellqvist, Olle, et al.
(författare)
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Learning Optimal Team-Decisions
- 2022
-
Ingår i: 2022 IEEE 61st Conference on Decision and Control, CDC 2022. - 0743-1546 .- 2576-2370. - 9781665467612 ; 2022-December, s. 1441-1446
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we linear quadratic team decision problems, where a team of agents minimizes a convex quadratic cost function over T time steps subject to possibly distinct linear measurements of the state of nature. We assume that the state of nature is a Gaussian random variable and that the agents do not know the cost function nor the linear functions mapping the state of nature to their measurements. We present a gradient-descent based algorithm with an expected regret of O(log(T)) for full information gradient feedback and O(√(T)) for bandit feedback. In the case of bandit feedback, the expected regret has an additional multiplicative term O(d) where d reflects the number of learned parameters.
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| 26. |
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| 27. |
- Liang, Kuo-Yun, et al.
(författare)
-
The Impact of Heterogeneity and Order in Heavy Duty Vehicle Platooning Networks
- 2011
-
Konferensbidrag (refereegranskat)abstract
- It is formally known that by establishing a heavy duty vehicle platoon, the fuel consumption is reduced for the follower vehicle due to the lower air drag. However, it is not clear how the platoon should be formed with respect to the heavy duty vehicle properties. String stability is a well discussed issue in vehicle platooning. However, each vehicle’s properties have to be taken into consideration when analyzing the platoon system. In this paper, we analyze one property of heavy duty vehicles − the mass. The results show that the robustness is influenced by the order and physical characteristics of the vehicles in the platoon. When utilizing identical PID controllers for all vehicles in the platoon, it is better to arrange the heaviest vehicle first with decreasing mass order when considering the platoon behavior. However, in reality it is difficult to start rearranging a platoon in the middle of a highway and it would also require V2Vcommunication. A controller is often optimized for a particular configuration set that can cause slinky effects to the platoon. Therefore, a mass-dependent PID controller is introduced to establish a better platoon behavior for heavy duty vehicles. The results show no slinky effects regardless of the vehicle order in the platoon.
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| 28. |
- Sahlholm, Per, et al.
(författare)
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Piecewise linear road grade estimation
- 2011
-
Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE international. - 0148-7191.
-
Tidskriftsartikel (refereegranskat)abstract
- Emerging heavy duty vehicle control systems increasingly rely on advance knowledge of the road topography, described by the longitudinal road grade. Highway road grade profiles are restricted by road design specifications to be piecewise affine. This characteristic is used herein to derive a method for road grade estimation based on standard on-vehicle sensors and optimal piecewise linear estimation through dynamic programming. The proposed method is demonstrated with on-road experiments. It is able to represent the road grade profile for two studied 15 km road sections, by 20 linear segments for each, with a root mean square error between 0.42 % and 0.55 % grade.
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| 29. |
- Terelius, Håkan, et al.
(författare)
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Converging an Overlay Network to a Gradient Topology
- 2011
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Konferensbidrag (refereegranskat)abstract
- In this paper, we investigate the topology convergence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors containing higher utility values, such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.
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| 30. |
- Wu, Hanwei, et al.
(författare)
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Conditional mutual information-based contrastive loss for financial time series forecasting
- 2020
-
Ingår i: Proceedings ICAIF '20: The First ACM International Conference on AI in Finance. - New York, NY, USA : Association for Computing Machinery (ACM).
-
Konferensbidrag (refereegranskat)abstract
- We present a representation learning framework for financial time series forecasting. One challenge of using deep learning models for finance forecasting is the shortage of available training data when using small datasets. Direct trend classification using deep neural networks trained on small datasets is susceptible to the overfitting problem. In this paper, we propose to first learn compact representations from time series data, then use the learned representations to train a simpler model for predicting time series movements. We consider a class-conditioned latent variable model. We train an encoder network to maximize the mutual information between the latent variables and the trend information conditioned on the encoded observed variables. We show that conditional mutual information maximization can be approximated by a contrastive loss. Then, the problem is transformed into a classification task of determining whether two encoded representations are sampled from the same class or not. This is equivalent to performing pairwise comparisons of the training datapoints, and thus, improves the generalization ability of the encoder network. We use deep autoregressive models as our encoder to capture long-term dependencies of the sequence data. Empirical experiments indicate that our proposed method has the potential to advance state-of-the-art performance.
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