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  • 101. 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)
  • 102. 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.

  • 103.
    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)
  • 104. 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)
  • 105. 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.

  • 106. 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.

  • 107. 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.

  • 108.
    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.

  • 109.
    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)
  • 110.
    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.

  • 111.
    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.

  • 112.
    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.

  • 113.
    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.

  • 114.
    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.

  • 115. 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.

  • 116.
    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.

  • 117.
    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.

  • 118.
    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.

  • 119.
    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.

  • 120.
    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.

  • 121.
    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.

  • 122.
    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.

  • 123.
    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.

  • 124.
    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.

  • 125.
    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.

  • 126. 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).

  • 127.
    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.

  • 128. 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.

  • 129. 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.

  • 130. 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.

  • 131. 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)
  • 132. 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.

  • 133.
    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)
  • 134.
    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)
  • 135.
    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), 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.
    Distributed Positioning of Autonomous Mobile Sensors with Application to Coverage Control2011Inngår i: Proc. American Control Conference (ACC), IEEE , 2011, s. 4822-4827Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider problems in multi-agent systems where a network of mobile sensors needs to self-organize such that some global objective function is maximized. To deal with the agents' lack of global information we approach the problem in a game-theoretic framework where agents/players are only able to access local measurements of their own local utility functions whose parameters and detailed analytical forms may be unknown. We then propose a distributed and adaptive algorithm, where each agent applies a local extremum seeking feedback adopted to its specific motion dynamics, and prove its global practical stability, implying that the agents asymptotically reach a configuration that is arbitrary close to the globally optimal one. For the stability analysis we introduce a novel methodology based on a Lie bracket trajectory approximation and combine it with a potential game approach. We apply the proposed algorithm to the sensor coverage problem and solve it in a distributed way where the agents do not need any a priori knowledge about the distribution of the events to be detected and about the detection probabilities of the individual agents. The proposed scheme is illustrated through simulations.

  • 136.
    Ebadat, Afrooz
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Bottegal, Giulio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Molinari, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Varagnolo, Damiano
    Division of Signals and Systems, Department of Computer Science, Electrical and Space Engineering, Luleå University of Innovation and Technology.
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multi-room occupancy estimation through adaptive gray-box models2015Inngår i: Decision and Control (CDC), 2015 IEEE 54th Annual Conference on, IEEE conference proceedings, 2015, s. 3705-3711Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    We consider the problem of estimating the occupancylevel in buildings using indirect information such as CO2 concentrations and ventilation levels. We assume that oneof the rooms is temporarily equipped with a device measuringthe occupancy. Using the collected data, we identify a gray-boxmodel whose parameters carry information about the structuralcharacteristics of the room. Exploiting the knowledge of thesame type of structural characteristics of the other rooms inthe building, we adjust the gray-box model to capture the CO2dynamics of the other rooms. Then the occupancy estimatorsare designed using a regularized deconvolution approach whichaims at estimating the occupancy pattern that best explainsthe observed CO2 dynamics. We evaluate the proposed schemethrough extensive simulation using a commercial software tool,IDA-ICE, for dynamic building simulation.

  • 137.
    Ebadat, Afrooz
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Bottegal, Giulio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Varagnolo, Damiano
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Blind identification strategies for room occupancy estimation2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose and test on real data a two-tier estimation strategy for inferring occupancy levels from measurements of CO2 concentration and temperature levels. The first tier is a blind identification step, based either on a frequentist Maximum Likelihood method, implemented using non-linear optimization, or on a Bayesian marginal likelihood method, implemented using a dedicated Expectation-Maximization algorithm. The second tier resolves the ambiguity of the unknown multiplicative factor, and returns the final estimate of the occupancy levels. The overall procedure addresses some practical issues of existing occupancy estimation strategies. More specifically, first it does not require the installation of special hardware, since it uses measurements that are typically available in many buildings. Second, it does not require apriori knowledge on the physical parameters of the building, since it performs system identification steps. Third, it does not require pilot data containing measured real occupancy patterns (i.e., physically counting people for some periods, a typically expensive and time consuming step), since the identification steps are blind.

  • 138.
    Ebadat, Afrooz
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bottegal, Giulio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Varagnolo, Damiano
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    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.
    Estimation of building occupancy levels through environmental signals deconvolution2013Inngår i: Proceedings of the 5th ACM Workshop on Embedded Systems For Energy-Efficient Buildings, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We address the problem of estimating the occupancy levelsin rooms using the information available in standardHVAC systems. Instead of employing dedicated devices, weexploit the significant statistical correlations between the occupancylevels and the CO2 concentration, room temperature,and ventilation actuation signals in order to identify adynamic model. The building occupancy estimation problemis formulated as a regularized deconvolution problem, wherethe estimated occupancy is the input that, when injected intothe identified model, best explains the currently measuredCO2 levels. Since occupancy levels are piecewise constant,the zero norm of occupancy is plugged into the cost functionto penalize non-piecewise constant inputs. The problemthen is seen as a particular case of fused-lasso estimator byrelaxing the zero norm into the `1 norm. We propose bothonline and offline estimators; the latter is shown to performfavorably compared to other data-based building occupancyestimators. Results on a real testbed show that the MSE ofthe proposed scheme, trained on a one-week-long dataset, is half the MSE of equivalent Neural Network (NN) or SupportVector Machine (SVM) estimation strategies.

  • 139.
    Ebadat, Afrooz
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Bottegal, Giulio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Varagnolo, Damiano
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Regularized Deconvolution-Based Approaches for Estimating Room Occupancies2015Inngår i: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 12, nr 4, s. 1157-1168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We address the problem of estimating the number of people in a room using information available in standard HVAC systems. We propose an estimation scheme based on two phases. In the first phase, we assume the availability of pilot data and identify a model for the dynamic relations occurring between occupancy levels, CO2 concentration and room temperature. In the second phase, we make use of the identified model to formulate the occupancy estimation task as a deconvolution problem. In particular, we aim at obtaining an estimated occupancy pattern by trading off between adherence to the current measurements and regularity of the pattern. To achieve this goal, we employ a special instance of the so-called fused lasso estimator, which promotes piecewise constant estimates by including an l(1) norm-dependent term in the associated cost function. We extend the proposed estimator to include different sources of information, such as actuation of the ventilation system and door opening/closing events. We also provide conditions under which the occupancy estimator provides correct estimates within a guaranteed probability. We test the estimator running experiments on a real testbed, in order to compare it with other occupancy estimation techniques and assess the value of having additional information sources.

  • 140.
    Ebadat, Afrooz
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Varagnolo, D.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Bottegal, G.
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Application-oriented input design for room occupancy estimation algorithms2017Inngår i: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the problem of occupancy estimation in buildings using available environmental information. In particular, we study the problem of how to collect data that is informative enough for occupancy estimation purposes. We thus propose an application-oriented input design approach for designing the ventilation signal to be used while collecting the system identification datasets. The main goal of the method is to guarantee a certain accuracy in the estimated occupancy levels while minimizing the experimental time and effort. To take into account potential limitations on the actuation signals we moreover formulate the problem as a recursive nonlinear and nonconvex optimization problem, solved then using exhaustive search methods. We finally corroborate the theoretical findings with some numerical examples, which results show that computing ventilation signals using experiment design concepts leads to occupancy estimator performing 4 times better in terms of Mean Square Error (MSE).

  • 141. Eilers, S.
    et al.
    Mårtensson, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Pettersson, H.
    Pillado, M.
    Gallegos, D.
    Tobar, M.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Ma, Xiaoliang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Transportplanering, ekonomi och teknik.
    Friedrichs, T.
    Borojeni, S. S.
    Adolfson, M.
    COMPANION-Towards Co-operative Platoon Management of Heavy-Duty Vehicles2015Inngår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, IEEE , 2015, s. 1267-1273Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of the EU project COMPANION is to develop co-operative mobility technologies for supervised vehicle platooning, in order to improve fuel efficiency and safety for goods transport. The potential social and environmental benefits inducted by heavy-duty vehicle platoons have been largely proven. However, until now, the creation, coordination, and operation of such platoons have been mostly neglected. In addition, the regulation and standardization of coordinated platooning, together with its acceptance by the end-users and the society need further attention and research. In this paper we give an overview over the project and present the architecture of the off-board and onboard platforms of the COMPANION cooperative platoon management system. Furthermore, the consortium reports on the first results of the human factors for platooning, legislative analysis of platooning aspects, clustering and optimization of platooning plans and prediction of congestion due to planned special events. Finally, we present the method of validation of the system via simulation and trials.

  • 142. Epstein, M.
    et al.
    Lynch, K.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Murray, R. M.
    Using hierarchical decomposition to speed up average consensus2008Inngår i: Proceedings of the 17th IFAC World Congress, 2008, 2008, s. 612-618Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study the continuous-time consensus problem where nodes on a graph attempt to reach average consensus. We consider communication graphs that can be decomposed into a hierarchical structure and present a consensus scheme that exploits this hierarchical topology. The scheme consists of splitting the overall graph into layers of smaller connected subgraphs. Consensus is performed within the individual subgraphs starting with those of the lowest layer of the hierarchy and moving upwards. Certain ``leader'' nodes bridge the layers of the hierarchy. By exploiting the increased convergence speed of the smaller subgraphs, we show how this scheme can achieve faster overall convergence than the standard single-stage consensus algorithm running on the full graph topology. The result presents some fundamentals on how the communication architecture influences the global performance of a networked system. Analytical performance bounds are derived and simulations provided to illustrate the effectiveness of the scheme.

  • 143. Fagnani, Fabio
    et al.
    Johansson, Karl Henrik
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Speranzon, Alberto
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Zampieri, Sandro
    On multi-vehicle rendezvous under quantized communication2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A rendezvous problem for a team of autonomous vehicles, which communicate over quantized channels, is analyzed. The paper illustrates how communication topologies based on uniform and logarithmic quantizations influence the performance. Since a logarithmic quantizer in general imposes fewer bits to be communicated compared to a uniform quantizer, the results indicate estimates of lower limits on the amount of information that needs to be exchanged in order for the vehicles to meet. Simulation examples illustrate the results.

  • 144.
    Fang, Song
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Ishii, Hideaki
    Tokyo Inst Technol, Dept Comp Sci, Tokyo, Japan..
    Chen, Jie
    City Univ Hong Kong, Dept Elect Engn, Hong Kong, Peoples R China..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    A Frequency-Domain Characterization of Optimal Error Covariance for the Kalman-Bucy Filter2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 6366-6371Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we discover that the trace of the division of the optimal output estimation error covariance over the noise covariance attained by the Kalman-Bucy filter can be explicitly expressed in terms of the plant dynamics and noise statistics in a frequency-domain integral characterization. Towards this end, we examine the algebraic Riccati equation associated with Kalman-Bucy filtering using analytic function theory and relate it to the Bode integral. Our approach features an alternative, frequency-domain framework for analyzing algebraic Riccati equations and reduces to various existing related results.

  • 145. Farhad, Farokhi
    et al.
    Johansson, Karl
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A piecewise-constant congestion taxing policy for repeated routing games2015Inngår i: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 78, s. 123-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider repeated routing games with piecewise-constant congestion taxing in which a central planner sets and announces the congestion taxes for fixed windows of time in advance. Specifically, congestion taxes are calculated using marginal congestion pricing based on the flow of the vehicles on each road prior to the beginning of the taxing window (and, hence, there is a time-varying delay in setting the congestion taxes). We motivate the piecewise-constant taxing policy by that users or drivers may dislike fast-changing prices and that they also prefer prior knowledge of the prices. We prove for this model that the multiplicative update rule and the discretized replicator dynamics converge to a socially optimal flow when using vanishing step sizes. Considering that the algorithm cannot adapt itself to a changing environment when using vanishing step sizes, we propose adopting constant step sizes in this case. Then, however, we can only prove the convergence of the dynamics to a neighborhood of the socially optimal flow (with the size of the neighbourhood being of the order of the selected step size). The results are illustrated on a nonlinear version of Pigou's famous routing game.

  • 146. Farokhi, F.
    et al.
    Shames, I.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Private and Secure Coordination of Match-Making for Heavy-Duty Vehicle Platooning2017Inngår i: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, nr 1, s. 7345-7350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A secure and private framework for inter-agent communication and coordination is developed. This allows an agent, in our case a fleet owner, to ask questions or submit queries in an encrypted fashion using semi-homomorphic encryption. The submitted query can be about the interest of the other fleet owners for using a road at a specific time of the day, for instance, for the purpose of collaborative vehicle platooning. The other agents can then provide appropriate responses without knowing the content of the questions or the queries. Strong privacy and security guarantees are provided for the agent who is submitting the queries. It is also shown that the amount of the information that this agent can extract from the other agent is bounded. In fact, with submitting one query, a sophisticated agent can at most extract the answer to two queries. This secure communication platform is used subsequently to develop a distributed coordination mechanisms among fleet owners.

  • 147.
    Farokhi, Farhad
    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.
    Adaptive control design under structured model information limitation: A cost-biased maximum-likelihood approach2015Inngår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 75, s. 8-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Networked control strategies based on limited information about the plant model usually result in worse closed-loop performance than optimal centralized control with full plant model information. Recently, this fact has been established by utilizing the concept of competitive ratio, which is defined as the worst-case ratio of the cost of a control design with limited model information to the cost of the optimal control design with full model information. We show that an adaptive controller, inspired by a controller proposed by Campi and Kumar, with limited plant model information, asymptotically achieves the closed-loop performance of the optimal centralized controller with full model information for almost any plant. Therefore, there exists, at least, one adaptive control design strategy with limited plant model information that can achieve a competitive ratio equal to one. The plant model considered in the paper belongs to a compact set of stochastic linear time-invariant systems and the closed-loop performance measure is the ergodic mean of a quadratic function of the state and control input.

  • 148.
    Farokhi, Farhad
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Using piecewise-constant congestion taxing policy in repeated routing games2015Inngår i: SIAM Conference on Control and Its Applications 2015, 2015, s. 274-281Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider repeated routing games with piecewise-constant congestion taxing in which a central planner sets and announces the congestion taxes for fixed windows of time in advance. Specifically, congestion taxes are calculated using marginal congestion pricing based on the flow of the vehicles on each road prior to the beginning of the taxing window. The piecewise-constant taxing policy in motivated by that users or drivers may dislike fast-changing prices and that they also prefer prior knowledge of the prices. We prove that the multiplicative update rule converges to a socially optimal flow when using vanishing step sizes. Considering that the algorithm cannot adapt itself to a changing environment when using vanishing step sizes, we propose using constant step sizes in this case. Then, however, we can only prove the convergence of the dynamics to a neighborhood of the socially optimal flow (with its size being of the order of the selected step size).

  • 149.
    Farokhi, Farhad
    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.
    A Game-Theoretic Framework for Studying Truck Platooning Incentives2013Inngår i: Proceedings of the 16th International IEEE Annual Conference on Intelligent Transportation Systems (ITSC 2013), IEEE conference proceedings, 2013, s. 1253-1260Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An atomic congestion game with two types of agents, cars and trucks, is used to model the traffic flow on a road over certain time intervals. In this game, the drivers make a trade-off between the time they choose to use the road, the average velocity of the flow at that time, and the dynamic congestion tax that they are paying to use the road. The trucks have platooning capabilities and therefore, have an incentive for using the road at the same time as their peers. The dynamics and equilibria of this game-theoretic model for the interaction between car traffic and truck platooning incentives are investigated. We use traffic data from Stockholm to validate the modeling assumptions and extract reasonable parameters for the simulations. We perform a comprehensive simulation study to understand the influence of various factors, such as the percentage of the trucks that are equipped with platooning devices on the properties of the pure strategy Nash equilibrium that is learned using a joint strategy fictitious play.

  • 150.
    Farokhi, Farhad
    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.
    A Study of Truck Platooning Incentives Using a Congestion Game2015Inngår i: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 16, nr 2, s. 581-595, artikkel-id 6847185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We introduce an atomic congestion game with two types of agents, namely, cars and trucks, to model the traffic flow on a road over various time intervals of the day. Cars maximize their utility by finding a tradeoff between the time they choose to use the road, the average velocity of the flow at that time, and the dynamic congestion tax that they pay for using the road. In addition to these terms, the trucks have an incentive for using the road at the same time as their peers because they have platooning capabilities, which allow them to save fuel. The dynamics and equilibria of this game-theoretic model for the interaction between car traffic and truck platooning incentives are investigated. We use traffic data from Stockholm, Sweden, to validate parts of the modeling assumptions and extract reasonable parameters for the simulations. We use joint strategy fictitious play and average strategy fictitious play to learn a pure strategy Nash equilibrium of this game. We perform a comprehensive simulation study to understand the influence of various factors, such as the drivers' value of time and the percentage of the trucks that are equipped with platooning devices, on the properties of the Nash equilibrium.

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