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  • 101.
    Cavaliere, Clara
    et al.
    Univ Naples Federico II, Dept Elect Engn & Informat Technol, Naples, Italy..
    Mariniello, Dario
    Univ Naples Federico II, Dept Elect Engn & Informat Technol, Naples, Italy..
    Adaldo, Antonio
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Lo Iudice, Francesco
    Univ Naples Federico II, Dept Elect Engn & Informat Technol, Naples, Italy..
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    di Bernardo, Mario
    Univ Naples Federico II, Dept Elect Engn & Informat Technol, Naples, Italy..
    Cloud-supported self-triggered control for multi-agent circumnavigation2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 5090-5095Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a cloud-supported control framework for multi-agent circumnavigation missions. We consider a network of planar autonomous agents. Our objective is for the agents to circumnavigate a target with a desired angular speed, while forming a regular polygon around the target. We propose self-triggered rules to schedule the bearing measurements and the cloud accesses for each agent.

  • 102.
    Champati, Jaya Prakash
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Mamduhi, Mohammad H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    Gross, James
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap.
    Performance Characterization Using AoI in a Single-loop Networked Control System2019Inngår i: IEEE INFOCOM 2019 - IEEE Conference on Computer Communications Workshops, INFOCOM Workshops 2019, IEEE , 2019, s. 197-203Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The joint design of control and communication scheduling in a Networked Control System (NCS) is known to be a hard problem. Several research works have successfully designed optimal sampling and/or control strategies under simplified communication models, where transmission delays/times are negligible or fixed. However, considering sophisticated communication models, with random transmission times, result in highly coupled and difficult-to-solve optimal design problems due to the parameter inter-dependencies between estimation/control and communication layers. To tackle this problem, in this work, we investigate the applicability of Age-of-Information (AoI) for solving control/estimation problems in an NCS under i.i.d. transmission times. Our motivation for this investigation stems from the following facts: 1) recent results indicate that AoI can be tackled under relatively sophisticated communication models, and 2) a lower AoI in an NCS may result in a lower estimation/control cost. We study a joint optimization of sampling and scheduling for a single-loop stochastic LTI networked system with the objective of minimizing the time-average squared norm of the estimation error. We first show that, under mild assumptions on information structure the optimal control policy can be designed independently from the sampling and scheduling policies. We then derive a key result that minimizing the estimation error is equivalent to minimizing a non-negative and non-decreasing function of AoI. The parameters of this function include the LTI matrix and the covariance of exogenous noise in the LTI system. Noting that the formulated problem is a stochastic combinatorial optimization problem and is hard to solve, we resort to heuristic algorithms by extending existing algorithms in the AoI literature. We also identify a class of LTI system dynamics for which minimizing the estimation error is equivalent to minimizing the expected AoI.

  • 103. Chen, J.
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Olariu, S.
    Paschalidis, I.Ch.
    Stojmenovic, I.
    Guest Editorial Special Issue on Wireless Sensor and Actuator Networks2011Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, nr 10, s. 2244-2246Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    networked_control_si_tac11
  • 104. Chen, J.
    et al.
    Wei, Jieqiang
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Chen, Wei
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. University of California at Berkeley, United States.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Protecting Positive and Second-Order Systems against Undetectable Attacks2017Inngår i: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, nr 1, s. 8373-8378Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Undetectable attacks in security studies of cyber-physical systems render the measurements of the system equal to a possible physical response. In this paper, we investigate defense strategies against the undetectable single-attack for positive systems and second-order systems, which both can be reinterpreted in terms of graphs with nodes and edges, while the undetectable attack is added through one of the nodes. We show that an arbitrary placement of a sensor prevents undetectable single-attack for these classes of systems. It is worth emphasising that we do not need to measure at the corrupted node to prevent the undetectable single-attack, but can measure at any node. The defense strategy is of a low complexity and can be readily implemented.

  • 105.
    Chen, Phoebus
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ramesh, Chithrupa
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Reducing Packet Loss Bursts in a Wireless Mesh Network for Stochastic Bounds on Estimation Error2011Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2011, s. 3130-3135Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A big challenge for wireless networked control systems is how to design the underlying networking algorithms and protocols to provide high reliability, defined as the end-to-end probability of packet delivery, despite the high packet loss rates of individual wireless links. This paper formulates the problem of jointly designing a set of packet forwarding policies on a multipath mesh network to meet control application requirements. We derive several results to help understand the problem space. First, we demonstrate that some common approaches, like applying a single forwarding policy to all packets or always routing packets on disjoint paths, are not optimal for the application when the links are bursty. Second, we introduce the notion of dominance to give a partial ordering to sets of forwarding policies, used to prove that an optimal policy schedules all outgoing links at each node and that an upper bound on the performance attained by unicast forwarding policies on the network graph can be computed assuming a flooding policy. Third, we demonstrate how to convert application performance metrics to packet forwarding policy objectives, using the probability that the error covariance of a Kalman filter stays within a bound as our application metric. Fourth, we provide an algorithm to compute the joint probability mass function that a sequence of packets are delivered, given a set of policies and a network graph. Finally, we describe how to obtain optimal policies via an exhaustive search, motivating future research for more computationally efficient solutions.

  • 106.
    Chen, Phoebus
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ramesh, Chithrupa
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Network Estimation and Packet Delivery Prediction for Control over Wireless Mesh Networks2011Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline), 2011, s. 6573-6579Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Much of the current theory of networked control systems uses simple point-to-point communication models as an abstraction of the underlying network. As a result, the controller has very limited information on the network conditions and performs suboptimally. This work models the underlying wireless multihop mesh network as a graph of links with transmission success probabilities, and uses a recursive Bayesian estimator to provide packet delivery predictions to the controller. The predictions are a joint probability distribution on future packet delivery sequences, and thus capture correlations between successive packet deliveries. We look at finite horizon LQG control over a lossy actuation channel and a perfect sensing channel, both without delay, to study how the controller can compensate for predicted network outages.

  • 107.
    Chen, Wei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liu, Ji
    Chen, Yongxin
    Khong, Sei Zhen
    Wang, Dan
    Basar, Tamer
    Qiu, Li
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Characterizing the Positive Semidefiniteness of Signed Laplacians via Effective Resistances2016Inngår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 985-990, artikkel-id 7798396Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A symmetric signed Laplacian matrix uniquely defines a resistive electrical circuit, where the negative weights correspond to negative resistances. The positive semidefiniteness of signed Laplacian matrices is studied in this paper using the concept of effective resistance. We show that a signed Laplacian matrix is positive semidefinite with a simple zero eigenvalue if, and only if, the underlying graph is connected, and a suitably defined effective resistance matrix is positive definite.

  • 108.
    Chen, Wei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wang, D.
    Liu, J.
    Başar, T.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Qiu, L.
    On Semidefiniteness of Signed Laplacians with Application to Microgrids2016Inngår i: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 49, nr 22, s. 97-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper investigates the positive semidefiniteness of signed Laplacians. It is noted that a symmetric signed Laplacian defines a unique resistive electrical network, wherein the negative weights correspond to negative resistances. As such, the positive semidefiniteness of the signed Laplacians is equivalent to the passivity of the associated resistive networks. By utilizing n-port circuit theory, we obtain several equivalent conditions for signed Laplacians to be positive semidefinite with a simple zero eigenvalue. These conditions characterize a set of negative weights that maintain the semidefiniteness of the Laplacian. The results are used to analyze the small-disturbance angle stability of microgrids as an application.

  • 109.
    Cho, K.-H.
    et al.
    Univ. of Ulsan, Ulsan, Korea.
    Johansson, Karl Henrik
    KTH.
    Wolkenhauer, O
    Univ. of Rostock, Rostock, Germany.
    A system-theoretic modeling framework for cellular processes2004Konferansepaper (Fagfellevurdert)
    Fulltekst (pdf)
    bio_icsb04
  • 110. Cho, Kwang-Hyun
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Wolkenhauer, Olaf
    A hybrid systems framework for cellular processes2005Inngår i: Biosystems (Amsterdam. Print), ISSN 0303-2647, E-ISSN 1872-8324, Vol. 80, nr 3, s. 273-282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the availability of technologies that allow us to obtain stimulus-response time series data for modeling and system identification, there is going to be an increasing need for conceptual frameworks in which to formulate and test hypotheses about intra- and inter-cellular dynamics, in general and not just dependent on a particular cell line, cell type, organism, or technology. While the semantics can be quite different, biologists and systems scientists use in many cases a similar language (notion of feedback, regulation, etc.). A more abstract system-theoretic framework for signals, systems, and control could provide the biologist with an interface between the domains. Apart from recent examples to identify functional elements and describing them in engineering terms, there have been various more abstract developments to describe dynamics at the cell level in the past. This includes Rosen's (M,R)-systems. This paper presents an abstract and general compact mathematical framework of intracellular dynamics, regulation and regime switching inspired by (M,R)-theory and based on hybrid automata.

    Fulltekst (pdf)
    hybrid_bio05
  • 111. Dai, L.
    et al.
    Gao, Yulong
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Xie, L.
    Johansson, Karl Henrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Xia, Y.
    Stochastic self-triggered model predictive control for linear systems with probabilistic constraints2018Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 92, s. 9-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stochastic self-triggered model predictive control (SSMPC) algorithm is proposed for linear systems subject to exogenous disturbances and probabilistic constraints. The main idea behind the self-triggered framework is that at each sampling instant, an optimization problem is solved to determine both the next sampling instant and the control inputs to be applied between the two sampling instants. Although the self-triggered implementation achieves communication reduction, the control commands are necessarily applied in open-loop between sampling instants. To guarantee probabilistic constraint satisfaction, necessary and sufficient conditions are derived on the nominal systems by using the information on the distribution of the disturbances explicitly. Moreover, based on a tailored terminal set, a multi-step open-loop MPC optimization problem with infinite prediction horizon is transformed into a tractable quadratic programming problem with guaranteed recursive feasibility. The closed-loop system is shown to be stable. Numerical examples illustrate the efficacy of the proposed scheme in terms of performance, constraint satisfaction, and reduction of both control updates and communications with a conventional time-triggered scheme.

  • 112.
    De Campos, Gabriel Rodrigues
    et al.
    Politecn Milan, Dept DEIB, Via Ponzio 34-5, I-20133 Milan, Italy..
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Seuret, Alexandre
    Univ Toulouse, CNRS LAAS, Equipe MAC, 7 Ave Colonel Roche,BP 54200, F-31031 Toulouse 4, France..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Distributed control of compact formations for multi-robot swarms2018Inngår i: IMA Journal of Mathematical Control and Information, ISSN 0265-0754, E-ISSN 1471-6887, Vol. 35, nr 3, s. 805-835Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article proposes a distributed algorithm for the compact deployment of robots, using both distance-and angular-based arguments in the controllers' design. Our objective is to achieve a configuration maximizing the coverage of the environment while increasing the graph's connectivity. First, we provide: (i) a dispersion protocol guaranteeing connectivity maintenance; and (ii) a compactness controller with static and variable control gains that minimizes the inter-agent angles. Second, we present a sequential, multi-stage strategy and analyse its stability. Finally, we validate our theoretical results with simulations, where a group of robots are deployed to carry out sensing or communication tasks.

  • 113. De Castro, N. C.
    et al.
    De Wit, C. C.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On energy-aware communication and control co-design in wireless networked control systems2010Inngår i: Estimation and Control of Networked Systems, 2010, s. 49-54Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Energy is a key resource in Networked Control Systems, in particular in applications concerning wireless networks. This paper reviews the multi-layer architecture of those systems in the light of their energy-use, and points out major contributions in the area of energy-management policies, layer per layer. This review of the literature is organized according to the layered communication architecture covering from bottom to top the Physical, Data Link, Network, and Application layers. We specifically focus on advances that concern energy-aware management in wireless communication and control co-design. It is argued that existing work is limited to single layer approaches, with a lack of design methods taking into account several layers.

  • 114. de Sousa, Joao Borges
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Silva, Jorge
    Speranzon, Alberto
    A verified hierarchical control architecture for co-ordinated multi-vehicle operations2007Inngår i: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 21, nr 02-3, s. 159-188Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    multirobot_ijacsp06
  • 115. Di Benedetto, M. D.
    et al.
    Bicchi, A.
    D'Innocenzo, A.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Robertsson, A.
    Santucci, F.
    Tiberi, U.
    Tzes, A.
    Networked control2009Inngår i: Handbook of Hybrid Systems Control, Cambridge University Press, 2009Kapittel i bok, del av antologi (Fagfellevurdert)
  • 116. Di Benedetto, M. D.
    et al.
    Innocenzo, A. D.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Isaksson, A. J.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Niculescu, S. -I
    Olaru, S.
    Sandou, G.
    Santucci, F.
    Serra, E.
    Tennina, S.
    Tiberi, U.
    Witrant, E.
    Wireless ventilation control for large-scale systems: The mining industrial case2009Inngår i: 2009 6th IEEE Annual Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009, Vol. SECON Workshops 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mining ventilation is an interesting example of a large scale system with high environmental impact where advanced control strategies can bring major improvements. Indeed, one of the first objectives of modern mining industry is to fulfill environmental specifications [1] during the ore extraction and crushing, by optimizing the energy consumption or the production of polluting agents. The mine electric consumption was 4 % of total industrial electric demand in the US in 1994 (6 % in 2007 in South Africa) and 90 % of it was related to motor system energy [2]. Another interesting figure is given in [3] where it is estimated that the savings associated with global control strategies for fluid systems (pumps, fans and compressors) represent approximately 20 % of the total manufacturing motor system energy savings. This motivates the development of new control strategies for large scale aerodynamic processes based on appropriate automation and a global consideration of the system. More specifically, the challenge in this work is focused on the mining ventilation since as much as 50 % or more of the energy consumed by the mining process may go into the ventilation (including heating the air). It is clear that investigating automatic control solutions and minimizing the amount of pumped air to save energy consumption (proportional to the cube of airflow quantity [4]) is of great environmental and industrial interest.

  • 117.
    Di Benedetto, Maria Domenica
    et al.
    Univ Aquila, Coll Engn, Ctr Excellence DEWS, I-67100 Laquila, Italy..
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Santucci, Fortunato
    Univ Aquila, Coll Engn, Ctr Excellence DEWS, I-67100 Laquila, Italy..
    Industrial control over wireless networks2010Inngår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 20, nr 2, s. 119-122Artikkel i tidsskrift (Annet vitenskapelig)
  • 118. Di Bernardo, M.
    et al.
    Johansson, Karl H.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Vasca, F.
    Self-oscillations and sliding in relay feedback systems: Symmetry and bifurcations2001Inngår i: International Journal of Bifurcation and Chaos in Applied Sciences and Engineering, ISSN 0218-1274, Vol. 11, nr 4, s. 1121-1140Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    relay_ijbc01
  • 119. Di Bernardo, Mario
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Jönsson, Ulf
    KTH, Tidigare Institutioner, Matematik.
    Vasca, Francesco
    On the robustness of periodic solutions in relay feedback systems2002Inngår i: Proceedings of the 15th IFAC World Congress, 2002, IFAC , 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Structural robustness of limit cycles in relay feedback systems is studied. Motivated by a recent discovery of a novel class of bifurcations in these systems, it is illustrated through numerical simulation that small relay perturbations may change the appearance of closed orbits dramatically. It is shown analytically that certain stable periodic solutions in relay feedback systems are robust to relay perturbations.

    Fulltekst (pdf)
    relay_ifac02
  • 120. Di Cairano, S.
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bemporad, A.
    Murray, R.
    Discrete and hybrid stochastic state estimation algorithms for networked control systems2008Inngår i: Hybrid Systems: Computation and Control / [ed] Egerstedt, M; Mishra, B, Springer-Verlag New York, 2008, s. 144-157Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Networked control systems enable for flexible systems operation and reduce cost of installation and maintenance, potentially at the price of increasing the uncertainty due to information exchange over the network. We focus on the problem of information loss in terms of packet drops, which are modelled as stochastic events that depend on the current state of the network. To design reliable control systems the state of the network must be estimated online, together with the state of the controlled process. This paper proposes various approaches to discrete and hybrid stochastic estimation of network and process states, where the network is modelled as a Markov chain and the packet drop probability depends on the states of the Markov chain. The proposed techniques are evaluated on simulations and experimental data.

    Fulltekst (pdf)
    networked_control_hscc08networked_control_hscc08
  • 121. Di Marco, P.
    et al.
    Rinaldi, C.
    Santucci, F.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Möller, N.
    Performance analysis and optimization of TCP over adaptive wireless links2006Inngår i: Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on          , IEEE , 2006, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes an analytical framework for performance evaluation of TCP (transport control protocol) over adaptive wireless links. Specifically, we include adaptation of power, modulation format and error recovery strategy, and incorporate some features of wireless fading channels. This framework is then used to pursue joint optimization through maximization of an objective functional, that expresses a trade-off between achievable throughput and energy costs. A set of numerical results is reported, and it is seen that hybrid ARQ schemes may provide significant benefits in the optimization framework.

    Fulltekst (pdf)
    network_pimrc06
  • 122.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Santucci, F.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Effects of Rayleigh-lognormal fading on IEEE 802.15.4 networks2013Inngår i: Communications (ICC), 2013 IEEE International Conference on, IEEE conference proceedings, 2013, s. 1666-1671Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The IEEE 802.15.4 communication protocol is a de-facto standard for wireless applications in industrial and home automation. Although the performance of the medium access control (MAC) of the IEEE 802.15.4 has been thoroughly investigated under the assumption of ideal wireless channel, there is still a lack of understanding of the cross-layer interactions between MAC and physical layer in the presence of realistic wireless channel models that include path loss, multi-path fading and shadowing. In this paper, an analytical model of these dynamics is proposed. The analysis considers simultaneously a composite Rayleigh-lognormal channel fading, interference generated by multiple terminals, the effects induced by hidden terminals, and the MAC reduced carrier sensing capabilities. It is shown that the reliability of the contention-based MAC over fading channels is often far from that derived under ideal channel assumptions. Moreover, it is established to what extent fading may be beneficial for the overall network performance.

  • 123.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Santucci, F.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Modeling cross-layer interactions of IEEE 802.15.4 wireless networks in cyber-physical systemsArtikkel i tidsskrift (Annet vitenskapelig)
  • 124.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Santucci, Fortunato
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Modeling IEEE 802.15.4 Networks Over Fading Channels2014Inngår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 13, nr 10, s. 5366-5381Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although the performance of the medium access control (MAC) of the IEEE 802.15.4 has been investigated under the assumption of ideal wireless channel, the understanding of the cross-layer dynamics between MAC and physical layer is an open problem when the wireless channel exhibits path loss, multi-path fading, and shadowing. The analysis of MAC and wireless channel interaction is essential for consistent performance prediction, correct design and optimization of the protocols. In this paper, a novel approach to analytical modeling of these interactions is proposed. The analysis considers simultaneously a composite channel fading, interference generated by multiple terminals, the effects induced by hidden terminals, and the MAC reduced carrier sensing capabilities. Depending on the MAC parameters and physical layer thresholds, it is shown that the MAC performance indicators over fading channels can be far from those derived under ideal channel assumptions. As novel results, we show to what extent the presence of fading may be beneficial for the overall network performance by reducing the multiple access interference, and how this information can be used for joint selection of MAC and physical layer parameters.

  • 125.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A dynamic energy-efficient protocol for reliable and timely communications for wireless sensor networks in control and automation2009Inngår i: 2009 6th IEEE Annual Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009, Vol. SECON Workshops 2009, s. 146-148Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Designing quality of service (QoS) guaranteed communication protocol for wireless sensor networks (WSNs) is essential to exploit the advantages and flexibilities offered by this technology for real-time control and actuation applications. A novel cross-layer protocol that embraces altogether a semirandom routing, MAC, data aggregation, and radio power control for clustered WSNs is presented. The protocol leverages the combination of a randomized and a deterministic approach to ensure robustness over unreliable channels and packet losses. An optimization problem, whose objective function is the network energy consumption, and the constraints are reliability and latency of the packets is modelled and solved to adaptively select the protocol parameters by a simple algorithm. As a relevant contribution, the proposed protocol is completely implemented on a test-bed, and it is compared to existing protocols. Experimental results validate the analysis and show excellent performance in terms of reliability, latency, low node duty cycle, load balancing and dynamic adaptation to the application requirements.

  • 126.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Analytical Modeling of Multi-hop IEEE 802.15.4 Networks2012Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, nr 7, s. 3191-3208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many of existing analytical studies of the IEEE 802.15.4 medium access control (MAC) protocol are not adequate because they are often based on assumptions such as homogeneous traffic and ideal carrier sensing, which are far from reality for multi-hop networks, particularly in the presence of mobility. In this paper, a new generalized analysis of the unslotted IEEE 802.15.4 MAC is presented. The analysis considers the effects induced by heterogeneous traffic due to multi-hop routing and different traffic generation patterns among the nodes of the network and the hidden terminals due to reduced carrier-sensing capabilities. The complex relation between MAC and routing protocols is modeled, and novel results on this interaction are derived. For various network configurations, conditions under which routing decisions based on packet loss probability or delay lead to an unbalanced distribution of the traffic load across multi-hop paths are studied. It is shown that these routing decisions tend to direct traffic toward nodes with high packet generation rates, with potential catastrophic effects for the node's energy consumption. It is concluded that heterogeneous traffic and limited carrier-sensing range play an essential role on the performance and that routing should account for the presence of dominant nodes to balance the traffic distribution across the network.

    Fulltekst (pdf)
    wsn_tvt12
  • 127.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Park, Pan Gun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    TREnD: A timely, reliable, energy-efficient and dynamic wsn protocol for control applications2010Inngår i: IEEE International Conference on Communications, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Control applications over wireless sensor networks (WSNs) require timely, reliable, and energy efficient communications. Cross-layer interaction is an essential design paradigm to exploit the complex interaction among the layers of the protocol stack and reach a maximum efficiency. Such a design approach is challenging because reliability and latency of delivered packets and energy are at odds, and resource constrained nodes support only simple algorithms. In this paper, the TREnD protocol is introduced for control applications over WSNs in industrial environments. It is a cross-layer protocol that embraces efficiently routing algorithm, MAC, data aggregation, duty cycling, and radio power control. The protocol parameters are adapted by an optimization problem, whose objective function is the network energy consumption, and the constraints are the reliability and latency of the packets. TREnD uses a simple algorithm that allows the network to meet the reliability and latency required by the control application while minimizing for energy consumption. TREnD is implemented on a test-bed and compared to some existing protocols. Experimental results show good performance in terms of reliability, latency, low duty cycle, and load balancing for both static and time-varying scenarios.

    Fulltekst (pdf)
    wsn_icc10
  • 128.
    Di Marco, Piergiuseppe
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Park, Pangun
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Analytical Modelling of IEEE 802.15.4 for Multi-hop Networks with Heterogeneous Traffic and Hidden Terminals2010Inngår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    IEEE 802.15.4 multi-hop wireless networks are an important communication infrastructure for many applications, including industrial control, home automation, and smart grids. Existing analysis of the IEEE 802.15.4 medium access control (MAC) protocol are often based on assumptions of homogeneous traffic and ideal carrier sensing, which are far from the reality when predicting performance for multi-hop networks. In this paper, a generalized analysis of the unslotted IEEE 802.15.4 MAC is presented. The model considers heterogeneous traffic and hidden terminals due to limited carrier sensing capabilities, and allows us to investigate jointly IEEE 802.15.4 MAC and routing algorithms. The analysis is validated via Monte Carlo simulations, which show that routing over multi-hop networks is significantly influenced by the IEEE 802.15.4 MAC performance. Routing decisions based on packet loss probability may lead to an unbalanced distribution of the traffic load across paths, thus motivating the need of a joint optimization of routing and MAC.

    Fulltekst (pdf)
    wsn_globecom10
  • 129.
    Dibaji, S. M.
    et al.
    MIT, Dept Mech Engn, Cambridge, MA 02139 USA..
    Pirani, Mohammad
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Annaswamy, A. M.
    MIT, Dept Mech Engn, Cambridge, MA 02139 USA..
    Johansson, Karl Henrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Chakrabortty, A.
    North Carolina State Univ, Dept Elect Engn, Raleigh, NC USA..
    Secure Control of Wide-Area Power Systems: Confidentiality and Integrity Threats2018Inngår i: 2018 IEEE Conference on Decision and Control  (CDC), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 7269-7274, artikkel-id 8618862Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A cyber-physical model for wide-area control of power systems is considered, where the state variables of each generator are measured and sent to the cyber-network and the corresponding control inputs are computed distributively. The secure control of such wide-area power systems is considered in the presence of cyber attacks that introduce threats that compromise their integrity and confidentiality. Detection, prevention, and resilience for these attacks and algorithms for accomplishing these goals are proposed. In particular, an algorithm to overcome confidentiality attacks of the underlying control gains is presented. Also proposed is an algorithm for defense against integrity attacks that might take place on the cyber-network. For this purpose, a resilient information retrieval approach is leveraged which recovers the true state variables despite the malicious attacks on both virtual machines and communication links. The retrieved states are then used to detect possible attacks on phasor measurement units (PMU) in the next time-step. Simulation studies are included to validate our proposed approaches.

  • 130.
    Dibaji, Seyed Mehran
    et al.
    MIT, Dept Mech Engn, Cambridge, MA 02139 USA..
    Pirani, Mohammad
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Flamholz, David Bezalel
    MIT, Dept Mech Engn, Cambridge, MA 02139 USA..
    Annaswamy, Anuradha M.
    MIT, Dept Mech Engn, Cambridge, MA 02139 USA..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Chakrabortty, Aranya
    North Carolina State Univ, Dept Elect Engn, Raleigh, NC USA..
    A systems and control perspective of CPS security2019Inngår i: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 47, s. 394-411Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The comprehensive integration of instrumentation, communication, and control into physical systems has led to the study of Cyber-Physical Systems (CPSs), a field that has recently garnered increased attention. A key concern that is ubiquitous in CPS is a need to ensure security in the face of cyber attacks. In this paper, we carry out a survey of systems and control methods that have been proposed for the security of CPS. We classify these methods into three categories based on the type of defense proposed against the cyberattacks: prevention, resilience, and detection & isolation. A unified threat assessment metric is proposed in order to evaluate how CPS security is achieved in each of these three cases. Also surveyed are the risk assessment tools and the effect of network topology on CPS security. Furthermore, an emphasis has been placed on power and transportation applications in the overall survey.

  • 131. Dimarogonas, Dimos V.
    et al.
    Frazzoli, E.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed self-triggered control for multi-agent systems2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is desirable to limit the amount of communication and computation generated by each agent in a large multi-agent system. Event- and self-triggered control strategies have been recently proposed as alternatives to traditional time-triggered periodic sampling for feedback control systems. In this paper we consider self-triggered control applied to a multi-agent system with an agreement objective. Each agent computes its next update time instance at the previous time. This formulation extends considerably our recent work on event-based control, because in the self-triggered setting the agents do not have to keep track of the state error that triggers the actuation between consecutive update instants. Both a centralized and a distributed self-triggered control architecture are presented and shown to achieve the agreement objective. The results are illustrated through simulated examples.

    Fulltekst (pdf)
    multiagent_event_cdc10
  • 132.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Frazzoli, Emilio
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed Event-Triggered Control for Multi-Agent Systems2012Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 57, nr 5, s. 1291-1297Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Event-driven strategies for multi-agent systems are motivated by the future use of embedded microprocessors with limited resources that will gather information and actuate the individual agent controller updates. The controller updates considered here are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem. A centralized formulation is considered first and then its distributed counterpart, in which agents require knowledge only of their neighbors' states for the controller implementation. The results are then extended to a self-triggered setup, where each agent computes its next update time at the previous one, without having to keep track of the state error that triggers the actuation between two consecutive update instants. The results are illustrated through simulation examples.

  • 133.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bounded control of network connectivity in multi-agent systems2010Inngår i: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 4, nr 8, s. 1330-1338Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A distributed control law that guarantees connectivity maintenance in a network of multiple mobile agents is presented. The control law, which lets the agents perform formation manoeuvres, respects sensor limitations by allowing each agent to only take into account agents within its sensing radius. In contrast to previous approaches to the problem, the proposed control law does not attain infinite values whenever an edge of the communication graph tends to be lost. This is achieved via the use of decentralised navigation functions, which are bounded potential fields. The navigation functions are defined to take into account the connectivity maintenance objective. The authors first treat the case of connectivity maintenance for a static communication graph and then extend the result to the case of dynamic graphs. The results are illustrated on a formation control problem.

    Fulltekst (pdf)
    multirobot_iet10
  • 134.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Stability analysis for multi-agent systems using the incidence matrix: Quantized communication and formation control2010Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 46, nr 4, s. 695-700Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The spectral properties of the incidence matrix of the communication graph are exploited to provide solutions to two multi-agent control problems. In particular, we consider the problem of state agreement with quantized communication and the problem of distance-based formation control. In both cases, stabilizing control laws are provided when the communication graph is a tree. It is shown how the relation between tree graphs and the null space of the corresponding incidence matrix encode fundamental properties for these two multi-agent control problems.

    Fulltekst (pdf)
    multiagent_automatica10
  • 135.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Analysis of robot navigation schemes using Rantzer's Dual Lyapunov Theorem2008Inngår i: 2008 AMERICAN CONTROL CONFERENCE, 2008, s. 201-206Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When robots are driven by the negative gradient of a potential field that consists of the sum of an attractive and a repulsive term, convergence to the desired configuration cannot be guaranteed by traditional Lyapunov techniques. In this paper, sufficient conditions for convergence of such systems are provided instead with the use of Rantzer's Dual Lyaptinov Theorem. In particular, a condition that involves the trace of the Hessian matrix of the potential function is derived and then applied to the cases of navigation of a single robot and of multi-robot formation stabilization. The main result of the paper states that a sufficient condition for convergence to a desired configuration in both cases is that the attractive potential admits a sufficiently large gain. A lower bound on the attractive potential is computed. Computer simulations that support the new results are provided.

    Fulltekst (pdf)
    multirobot_acc08_rantzer
  • 136.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Decentralized connectivity maintenance in mobile networks with bounded inputs2008Inngår i: 2008 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, 2008, s. 1507-1512Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A distributed control law that guarantees connectivity maintenance in a network of multiple mobile agents is presented. The control law respects the limited sensing capabilities of the agents by allowing each agent to take into account only agents within its sensing radius in the controller implementation. In contrast to previous approaches to the problem, the proposed control law does not attain infinite values whenever an edge tends to be lost, and is therefore a bounded distributed control law. This is achieved via the use of decentralized navigation functions which are potential fields with guaranteed boundedness and are redefined in this paper in order to take into account the connectivity maintenance objective. We first treat the case of connectivity maintenance in a static initial position based communication graph and extend the results to the case of dynamic edge addition. The results are then applied to a formation control problem.

    Fulltekst (pdf)
    multirobot_icra08
  • 137.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-triggered control for multi-agent systems2009Inngår i: Proceedings of the IEEE Conference on Decision and Control, 2009, s. 7131-7136Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Event-driven strategies for multi-agent systems are motivated by the future use of embedded microprocessors with limited resources that will gather information and actuate the individual agent controller updates. The control actuation updates considered in this paper are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem. A centralized formulation of the problem is considered first and then the results are extended to the decentralized counterpart, in which agents require knowledge only of the states of their neighbors for the controller implementation.

    Fulltekst (pdf)
    event-triggered_cdc09
  • 138.
    Dimarogonas, Dimos V.
    et al.
    Massachusetts Institute of Technology, United States.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Event-triggered cooperative control2015Inngår i: 2009 European Control Conference, ECC 2009, IEEE Press, 2015, s. 3015-3020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Future multi-agent systems will include embedded microprocessors with limited resources to gather information and actuate the individual agent controller updates. In this paper we examine the stability of such scheme in a cooperative control problem where the actuation updates are event-driven, depending on the ratio of a certain measurement error with respect to the norm of the state. In the centralized case, we obtain a strictly positive lower bound in the inter-event times, while relevant, yet more conservative, results are obtained in the decentralized case.

  • 139.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Further results on the stability of distance-based multi-robot formations2009Inngår i: 2009 AMERICAN CONTROL CONFERENCE, VOLS 1-9, 2009, s. 2972-2977Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An important class of multi-robot formations is specified by desired distances between adjacent robots. In previous work, we showed that distance-based formations can be globally stabilized by negative gradient, potential field based, control laws, if and only if the formation graph is a tree. In this paper, we further examine the relation between the cycle space of the formation graph and the resulting equilibria of cyclic formations. In addition, the results are extended to the case of distance based formation control for nonholonomic agents. The results are supported through computer simulations.

    Fulltekst (pdf)
    multirobot_acc09
  • 140.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On the stability of distance-based formation control2008Inngår i: Proceedings of the IEEE Conference on Decision and Control, 2008, s. 1200-1205Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper examines stability properties of distance-based formations. These are formations encoded by inter-agent relative distances. A negative gradient control law is proposed and is shown to be provably correct when the formation graph is a tree. Moreover, it is shown that the tree structure is a necessary and sufficient condition for distancebased formation stabilization with negative gradient control laws. For graphs that contain cycles, a characterization of the resulting equilibria is given based on the properties of the cycle space of the graph. The results are also applied to flocking motion for double integrator agents.

    Fulltekst (pdf)
    multirobot_cdc08
  • 141.
    Dimarogonas, Dimos V.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Quantized agreement under time-varying communication topology2008Inngår i: 2008 AMERICAN CONTROL CONFERENCE, 2008, s. 4376-4381Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cooperative control under quantized information for multi-agent systems with continuous models of motion is considered. Time-varying communication topology is taken into account and we distinguish between uniform and logarithmic quantization. Convergence guarantees are provided when the graph is a tree sufficiently often for the logarithmic quantizer, using tools from algebraic graph theory and Lyapunov stability. The results are illustrated by computer simulations.

    Fulltekst (pdf)
    multirobot_acc08_quant
  • 142. D'Innocenzo, A.
    et al.
    Weiss, G.
    Alur, R.
    Isaksson, A.J.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Pappas, G. J.
    Scalable scheduling algorithms for wireless networked control systems2009Inngår i: 2009 IEEE INTERNATIONAL CONFERENCE ON AUTOMATION SCIENCE AND ENGINEERING, IEEE , 2009, s. 409-414Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we address the problem of designing scalable scheduling and routing policies over a time-triggered multi-hop control network, when closing a considerable number of control loops on the same network. The key idea is to formally define by means of regular languages the set of schedules for each control loop that satisfy a given control specification, and to exploit operators on regular languages to compute the set of schedules for the whole system. In order to test our methodology, we address a mineral floatation control problem derived from the Boliden (a swedish mining company) mine in Garpenberg, and propose a scheduling solution that can be implemented on systems compliant with communication protocols for wireless networks (e.g. the WirelessHART specification).

    Fulltekst (pdf)
    networked_control_case09
  • 143.
    Du, Wen
    et al.
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Yi, Xinlei
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    George, Jemin
    US Army Res Lab, Adelphi, MD 20783 USA..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 76203 USA..
    Distributed Optimization with Dynamic Event-Triggered Mechanisms2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 969-974Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the distributed optimization problem, whose objective is to minimize the global objective function, which is the sum of local convex objective functions, by using local information exchange. To avoid continuous communication among the agents, we propose a distributed algorithm with a dynamic event-triggered communication mechanism. We show that the distributed algorithm with the dynamic event-triggered communication scheme converges to the global minimizer exponentially, if the underlying communication graph is undirected and connected. Moreover, we show that the event-triggered algorithm is free of Zeno behavior. For a particular case, we also explicitly characterize the lower bound for inter-event times. The theoretical results are illustrated by numerical simulations.

  • 144. Duerr, Hans-Bernd
    et al.
    Stankovic, Milos S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ebenbauer, Christian
    Extremum seeking on submanifolds in the Euclidian space2014Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 50, nr 10, s. 2591-2596Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Extremum seeking is a powerful control method to steer a dynamical system to an extremum of a partially unknown function. In this paper, we introduce extremum seeking systems on submanifolds in the Euclidian space. Using a trajectory approximation technique based on Lie brackets, we prove that uniform asymptotic stability of the so-called Lie bracket system on the manifold implies practical uniform asymptotic stability of the corresponding extremum seeking system on the manifold. We illustrate the approach with an example of extremum seeking on a torus.

  • 145. Durr, H. -B
    et al.
    Stankovic, M. S.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Ebenbauer, C.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Obstacle avoidance for an extremum seeking system using a navigation function2013Inngår i: Proceedings of the American Control Conference 2013, AACC American Automatic Control Council , 2013, s. 4062-4067Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of autonomously steering a vehicle to a destination point, while avoiding obstacles, is considered. The vehicle is modeled as a single-integrator in the plane and it is assumed that the obstacles are unknown a priori. The control law is an extremum seeking algorithm, which steers the vehicle to the minimum of a navigation function. In this framework, obstacle avoidance and practical uniform convergence to a destination point for almost all initial conditions is proven. The theoretic results are illustrated using numerical examples.

  • 146. Durr, H. -B
    et al.
    Stankovic, M. S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ebenbauer, C.
    Examples of distance-based synchronization: An extremum seeking approach2013Inngår i: 2013 51st Annual Allerton Conference on Communication, Control, and Computing, Allerton 2013, IEEE conference proceedings, 2013, s. 366-373Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we consider two examples of synchronization problems, i.e., a network of oscillators and a network of rigid bodies. We propose a controller that requires only the knowledge of the relative distances among the neighboring systems in the network. The controller is based on an extremum seeking controller, that steers the overall system to the minimum of an optimization problem on a manifold. Using a Lie bracket approximation for extremum seeking systems, we show that the controller leads to a synchronization of the overall network in both examples.

  • 147. Durr, H.-B.
    et al.
    Stankovic, Milos S.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nash equilibrium seeking in multi-vehicle systems: A Lie bracket approximation-based approachArtikkel i tidsskrift (Annet vitenskapelig)
  • 148. Dürr, Hans-Bernd
    et al.
    Stankovic, Milos S.
    Ebenbauer, Christian
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lie bracket approximation of extremum seeking systems2013Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 49, nr 6, s. 1538-1552Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Extremum seeking feedback is a powerful method to steer a dynamical system to an extremum of a partially or completely unknown map. It often requires advanced system-theoretic tools to understand the qualitative behavior of extremum seeking systems. In this paper, a novel interpretation of extremum seeking is introduced. We show that the trajectories of an extremum seeking system can be approximated by the trajectories of a system which involves certain Lie brackets of the vector fields of the extremum seeking system. It turns out that the Lie bracket system directly reveals the optimizing behavior of the extremum seeking system. Furthermore, we establish a theoretical foundation and prove that uniform asymptotic stability of the Lie bracket system implies practical uniform asymptotic stability of the corresponding extremum seeking system. We use the established results in order to prove local and semi-global practical uniform asymptotic stability of the extrema of a certain map for multi-agent extremum seeking systems.

  • 149.
    Dürr, Hans-Bernd
    et al.
    Institute for Systems Theory and Automatic Control, University of Stuttgart.
    Stankovic, Milos S.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Lie Bracket Approximation for Extremum Seeking Vehicles2011Inngår i: Proc. 18th IFAC World Congress, 2011, s. 11393-11398Konferansepaper (Fagfellevurdert)
  • 150.
    Dürr, Hans-Bernd
    et al.
    Institute for Systems Theory and Automatic Control, University of Stuttgart.
    Stankovic, Milos S.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lie Bracket Averaging for Nash Equilibrium Seeking in Multi-Vehicle SystemsArtikkel i tidsskrift (Fagfellevurdert)
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