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  • 51. Astrom, K. J.
    et al.
    Lee, T. H.
    Tan, K. K.
    Johansson, Karl Henrik
    Recent advances in relay feedback methods—a survey1995Konferansepaper (Fagfellevurdert)
  • 52.
    Auvert, Marine
    et al.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Hjalmarsson, Håkan
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Johansson, Karl H.
    KTH, Tidigare Institutioner, Signaler, sensorer och system.
    Karlsson, Gunnar
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    On Router Control for Congestion Avoidance2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This short paper deals with active queue management for computer networks. The goal is to develop control mechanisms for routers in heterogeneous networks that reduce traffic fluctuations. The proposed control strategy operates with local information (such as estimated arrival rates) and actively use the buffers to smooth traffic, and thus it avoids the buildup and propagation of traffic bursts.

  • 53. Bagloee, S. A.
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Asadi, M.
    A hybrid machine-learning and optimization method for contraflow design in post-disaster cases and traffic management scenarios2019Inngår i: Expert systems with applications, ISSN 0957-4174, E-ISSN 1873-6793, Vol. 124, s. 67-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growing number of man-made and natural disasters in recent years has made the disaster management a focal point of interest and research. To assist and streamline emergency evacuation, changing the directions of the roads (called contraflow, a traffic control measure) is proven to be an effective, quick and affordable scheme in the action list of the disaster management. The contraflow is computationally a challenging problem (known as NP-hard), hence developing an efficient method applicable to real-world and large-sized cases is a significant challenge in the literature. To cope with its complexities and to tailor to practical applications, a hybrid heuristic method based on a machine-learning model and bilevel optimization is developed. The idea is to try and test several contraflow scenarios providing a training dataset for a supervised learning (regression) model which is then used in an optimization framework to find a better scenario in an iterative process. This method is coded as a single computer program synchronized with GAMS (for optimization), MATLAB (for machine learning), EMME3 (for traffic simulation), MS-Access (for data storage) and MS-Excel (as an interface), and it is tested using a real dataset from Winnipeg, and Sioux-Falls as benchmarks. The algorithm managed to find globally optimal solutions for the Sioux-Falls example and improved accessibility to the dense and congested central areas of Winnipeg just by changing the direction of some roads.

  • 54. Balluchi, A.
    et al.
    Benvenuti, L.
    Engell, S.
    Geyer, T.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lamnabhi-Lagarrigue, F.
    Lygeros, J.
    Morari, M.
    Papafotioug, G.
    Sangiovanni-Vincentelli, A. L.
    Santuchi, F.
    Stursberg, O.
    Hybrid control of networked embedded systems2005Inngår i: European Journal of Control, ISSN 0947-3580, E-ISSN 1435-5671, Vol. 11, nr 4-5, s. 478-508Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid systems that involve the interaction of continuous and discrete dynamics have been an active area of research for a number of years. In this paper, we start by briefly surveying the main theoretical control problems that have been treated in the hybrid systems setting and classify them into stabilization, optimal control and language specification problems. We then provide an overview of recent developments in four of the most prominent areas where these hybrid control methods have found application: control of power systems, industrial process control, design of automotive electronics and communication networks.

  • 55. Bao, L.
    et al.
    Skoglund, M.
    Fischione, Carlo
    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.
    Rate allocation with power constraints for quantized control over binary symmetric channelsManuskript (preprint) (Annet vitenskapelig)
  • 56. Bao, L.
    et al.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Encoder-decoder design for feedback control over the binary symmetric channel2006Inngår i: 2006 IEEE International Symposium on Information Theory, Vols 1-6, Proceedings, IEEE , 2006, s. 2481-2485Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Encoder-decoder design is considered for a closed-loop scalar control system with feedback transmitted over a binary symmetric channel. We propose an iterative procedure which can jointly optimize adaptive encoder-decoder pairs for a certainly equivalence controller. The goal is to minimize a design criterion, in particular, the linear quadratic (LQ) cost function over a finite horizon. The algorithm leads to a practically feasible design of time-varying non-uniform encoding and decoding. Numerical results demonstrate the promising performance obtained by employing the proposed iterative optimization algorithm.

  • 57.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Optimized Rate Allocation for State Estimation over Noisy Channels2009Inngår i: 2009 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, NEW YORK: IEEE , 2009, s. 2684-2688Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optimal rate allocation in a networked control system with limited communication resources is instrumental to achieve satisfactory overall performance. In this paper, a practical rate allocation technique for state estimation in linear dynamic systems over a noisy channel is proposed. The method consists of two steps: (i) the overall distortion is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved by using Lagrange duality. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance when compared to arbitrarily selected rate allocations.

  • 58.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Optimized rate allocation for state feedback control over noisy channels2009Inngår i: Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009. Proceedings of the 48th IEEE Conference on, IEEE , 2009, s. 573-578Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optimal rate allocation in a networked control system with highly limited communication resources is instrumental to achieve satisfactory overall performance. In this paper, we propose a rate allocation technique for state feedback control in linear dynamic systems over a noisy channel. Our method consists of two steps: (i) the overall distortion is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved. We show that a non-uniform quantization is in general the best strategy for state feedback control over noisy channels. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance compared to arbitrarily selected rate allocations.

  • 59.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Rate Allocation for Quantized Control Over Binary Symmetric Channels2012Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, nr 6, s. 3188-3202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Utility maximization in networked control systems (NCSs) is difficult in the presence of limited sensing and communication resources. In this paper, a new communication rate optimization method for state feedback control over a noisy channel is proposed. Linear dynamic systems with quantization errors, limited transmission rate, and noisy communication channels are considered. The most challenging part of the optimization is that no closed-form expressions are available for assessing the performance and the optimization problem is nonconvex. The proposed method consists of two steps: (i) the overall NCS performance measure is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize a weighted quadratic objective function is solved. The proposed method is applied to the problem of state feedback control and the problem of state estimation. Monte Carlo simulations illustrate the performance of the proposed rate allocation. It is shown numerically that the proposed method has better performance when compared to arbitrarily selected rate allocations. Also, it is shown that in certain cases nonuniform rate allocation can outperform the uniform rate allocation, which is commonly considered in quantized control systems, for feedback control over noisy channels.

  • 60.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    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.
    Rate allocation for quantized control over noisy channels2009Inngår i: Final Proceedings of the 2009 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, 2009, Vol. WiOpt 2009, s. 595-603Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To achieve satisfactory overall performance, optimal rate allocation in a networked control system with highly limited communication resources is instrumental. In this paper, a rate allocation technique for state feedback control in linear dynamic systems over a noisy channel is proposed. The method consists of two steps: (i) the overall cost is expressed as a function of rates at all time instants by means of high-rate quantization theory, and (ii) a constrained optimization problem to minimize the overall distortion is solved. It is shown that a non-uniform quantization is in general the best strategy for state feedback control over noisy channels. Monte Carlo simulations illustrate the proposed scheme, which is shown to have good performance when compared to arbitrarily selected rate allocations.

  • 61. Bao, Lei
    et al.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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 scheme for joint quantization, error protection and feedback control over noisy channels2007Inngår i: 2007 AMERICAN CONTROL CONFERENCE, VOLS 1-13: PROCEEDINGS OF THE AMERICAN CONTROL CONFERENCE, IEEE , 2007, s. 2456-2461Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study a closed-loop scalar control system with feedback transmitted over a discrete noisy channel. For this problem, we propose a joint design of the state measurement quantization, protection against channel errors, and control. The goal is to minimize a linear quadratic cost function over a finite horizon. In particular we focus on a special case where we verify that certainty equivalence holds, and for this case we design joint source-channel encoder and decoder/estimator pairs. The proposed algorithm leads to a practically feasible design of time-varying non-uniform quantization and control. Numerical results demonstrate the promising performance obtained by employing the proposed iterative optimization algorithm.

  • 62.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Encoder-decoder design for event-triggered feedback control over bandlimited channels2006Inngår i: 2006 American Control Conference, IEEE , 2006, Vol. 1-12, s. 4183-4188Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Bandwidth limitations and energy constraints set severe restrictions on the design of control systems that utilize wireless sensor and actuator networks. It is common in these systems that a sensor node needs not be continuously monitored, but communicates to the controller only at certain instances when it detects a disturbance event. In this paper, such a scenario is studied and particular emphasis is on efficient utilization of the shared communication resources. Encoder-decoder design for an event-based control system with the plant affected by pulse disturbances is considered. A new iterative procedure is proposed which can jointly optimize encoder-decoder pairs for a certainty equivalent controller. The goal is to minimize a design criterion, in particular, a linear quadratic cost over a finite horizon. The algorithm leads to a feasible design of time-varying non-uniform encoder-decoder pairs. Numerical results demonstrate significant improvements in performance compared to a system using uniform quantization.

  • 63.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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.
    Iterative Encoder-Controller Design for Feedback Control Over Noisy Channels2011Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, nr 2, s. 265-278Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study a closed-loop control system with state feedback transmitted over a noisy discrete memoryless channel. With the objective to minimize the expected linear quadratic cost over a finite horizon, we propose a joint design of the sensor measurement quantization, channel error protection, and controller actuation. It is argued that despite that this encoder-controller optimization problem is known to be hard in general, an iterative design procedure can be derived in which the controller is optimized for a fixed encoder, then the encoder is optimized for a fixed controller, etc. Several properties of such a scheme are discussed. For a fixed encoder, we study how to optimize the controller given that full or partial side-information is available at the encoder about the symbols received at the controller. It is shown that the certainty equivalence controller is optimal when the encoder is optimal and has full side-information. For a fixed controller, expressions for the optimal encoder are given and implications are discussed for the special cases when process, sensor, or channel noise is not present. Numerical experiments are carried out to demonstrate the performance obtained by employing the proposed iterative design procedure and to compare it with other relevant schemes.

  • 64.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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 Iterative System Design and Separation in Control Over Noisy Channels2008Inngår i: IFAC World Congress, Volume 17, Part 1, IFAC , 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study a closed-loop control system with feedback transmitted over a noisy discrete memoryless channel. We design encoder-controller pairs that jointly optimize the sensor measurement quantization, protection against channel errors, and control. The designgoal is to minimize an expected linear quadratic cost over a finite horizon. As a result of deriving optimality criteria for this problem, we present new results on the validity of theseparation principle subject to certain assumptions. More precisely, we show that the certainty equivalence controller is optimal when the encoder is optimal and has full side-information about the symbols received at the controller. We then use this result to formulate tractable design criteria in the general case. Finally, numerical experiments are carried out to demonstrate the performance obtained by various design methods. 

  • 65. Bao, Lei
    et al.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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 optimal system design for feedback control over noisy channels2007Inngår i: 2007 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY PROCEEDINGS, VOLS 1-7, IEEE , 2007, s. 2486-2490Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study a closed-loop multivariable control system with sensor feedback transmitted over a discrete noisy channel. For this problem, we propose a joint design of the state measurement quantization, protection against channel errors, and control. The proposed algorithm leads to a practically feasible design of time-varying non-uniform encoding and control. Numerical results demonstrate the performance obtained by employing the proposed iterative optimization algorithm.

  • 66.
    Bao, Lei
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. 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 separation principle in optimal control over noisy channels2008Konferansepaper (Fagfellevurdert)
  • 67. Bemporad, Alberto
    et al.
    Di Cairano, Stefano
    Henriksson, Erik
    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.
    Hybrid Model Predictive Control Based on Wireless Sensor Feedback: an experimental study2007Inngår i: Proceedings of the 46th IEEE Conference on Decision and Control, New Orleans, Louisiana, USA., 2007, s. 5062-5067Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the design and the experimental validation of model predictive control (MPC) of a hybrid dynamical process based on measurements collected by a wireless sensor network. The proposed setup is the prototype of an industrial application in which a remote station controls the process via wireless network links. The experimental platform is a laboratory process consisting of four infrared lamps, controlled in pairs by two on/off switches, and of a transport belt, where moving parts equipped with wireless sensors are heated by the lamps. By approximating the stationary heat spatial distribution as a piecewise affine function of the position along the belt, the resulting plant model is a hybrid dynamical system. The control architecture is based on the reference governor approach: the process is actuated by a local controller, while a hybrid MPC algorithm running on a remote base station sends optimal belt velocity set-points and lamp on/off commands over a network link exploiting the information received through the wireless network. A discrete-time hybrid model of the process is used for the hybrid MPC algorithm and for the state estimator.

  • 68. Bemporad, Alberto
    et al.
    Di Cairano, Stefano
    Henriksson, Erik
    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.
    Hybrid model predictive control based on wireless sensor feedback: An experimental study2010Inngår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 20, nr 2, s. 209-225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Design and experimental validation of model predictive control (MPC) of a hybrid dynamical laboratory process with wireless sensors is presented. The laboratory process consists of four infrared lamps, controlled in pairs by two on/off switches, and of a transport belt, where moving parts equipped with wireless sensors are heated by the lamps. The process, which is motivated by heating processes in the plastic and printing industry, presents interesting hybrid dynamics. By approximating the stationary heat spatial distribution as a piecewise affine function of the position along the belt, the resulting plant model is a hybrid dynamical system. The control architecture is based on the reference governor approach: the process is actuated by a local controller, while a hybrid MPC algorithm running on a remote base station sends optimal belt velocity setpoints and lamp on/off commands over a wireless link, exploiting the sensor information received through the wireless network. A discrete-time hybrid model of the process is used for the hybrid MPC algorithm and for the state estimator. The physical modelling of the process and the hybrid MPC algorithm are presented in detail, together with the hardware and software architectures. The experimental results show that the presented theoretical framework is well suited for control of the new laboratory process, and that the process can be used as a prototype system for evaluating hybrid and networked control strategies.

  • 69.
    Bemporad, Alberto
    et al.
    Univ Siena, Fac Engn, Dept Informat Engn, I-53100 Siena, Italy..
    Di Cairano, Stefano
    Univ Siena, Fac Engn, Dept Informat Engn, I-53100 Siena, Italy..
    Henriksson, Erik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hybrid model predictive control based on wireless sensor feedback: An experimental study2007Inngår i: PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14, IEEE , 2007, s. 5583-+Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the design and the experimental validation of model predictive control (MPC) of a hybrid dynamical process based on measurements collected by a wireless sensor network. The proposed setup is the prototype of an industrial application in which a remote station controls the process via wireless network links. The experimental platform is a laboratory process consisting of four infrared lamps, controlled in pairs by two on/off switches, and of a transport belt, where moving parts equipped with wireless sensors are heated by the lamps. By approximating the stationary heat spatial distribution as a piecewise affine function of the position along the belt, the resulting plant model is a hybrid dynamical system. The control architecture is based on the reference governor approach: the process is actuated by a local controller, while a hybrid MPC algorithm running on a remote base station sends optimal belt velocity set-points and lamp on/off commands over a network link exploiting the information received through the wireless network. A discrete-time hybrid model of the process is used for the hybrid MPC algorithm and for the state estimator.

  • 70.
    Bern, Zvi
    et al.
    Univ Calif Los Angeles, Mani L Bhaumik Inst Theoret Phys, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Carrasco, John Joseph
    Univ Paris Saclay, CEA Saclay, Inst Theoret Phys, F-91191 Gif Sur Yvette, France.;CNRS, F-91191 Gif Sur Yvette, France..
    Chen, Wei-Ming
    Univ Calif Los Angeles, Mani L Bhaumik Inst Theoret Phys, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Edison, Alex
    Univ Calif Los Angeles, Mani L Bhaumik Inst Theoret Phys, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Johansson, Karl H.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Uppsala Univ, Dept Phys & Astron, S-75108 Uppsala, Sweden..
    Parra-Martinez, Julio
    Univ Calif Los Angeles, Mani L Bhaumik Inst Theoret Phys, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Roiban, Radu
    Penn State Univ, Inst Gravitat & Cosmos, University Pk, PA 16802 USA..
    Zeng, Mao
    Univ Calif Los Angeles, Mani L Bhaumik Inst Theoret Phys, Dept Phys & Astron, Los Angeles, CA 90095 USA..
    Ultraviolet properties of N=8 supergravity at five loops2018Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, nr 8, artikkel-id 086021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use the recently developed generalized double-copy construction to obtain an improved representation of the five-loop four-point integrand of N = 8 supergravity whose leading ultraviolet behavior we analyze using state-of-the-art loop-integral expansion and reduction methods. We find that the five-loop critical dimension where ultraviolet divergences first occur is D-c = 24/5, corresponding to a (DR4)-R-8 counterterm. This ultraviolet behavior stands in contrast to the cases of four-dimensional N = 4 supergravity at three loops and N = 5 supergravity at four loops whose improved ultraviolet behavior demonstrates enhanced cancellations beyond implications from standard symmetry considerations. We express this D-c = 24/5 divergence in terms of two relatively simple positive-definite integrals with vanishing external momenta, excluding any additional ultraviolet cancellations at this loop order. We note nontrivial relations between the integrals describing this leading ultraviolet behavior and integrals describing lower-loop behavior. This observation suggests not only a path towards greatly simplifying future calculations at higher loops, but may even allow us to directly investigate ultraviolet behavior in terms of simplified integrals, avoiding the construction of complete integrands.

  • 71. Bernhardsson, B.
    et al.
    Johansson, Karl H.
    Malmborg, J.
    Some properties of switched systems1999Konferansepaper (Fagfellevurdert)
  • 72. Bernhardsson, B.
    et al.
    Johansson, Karl Henrik
    On simultaneous H2-optimization of several performance bounds1993Konferansepaper (Fagfellevurdert)
  • 73. Besselink, Bart
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    String Stability and a Delay-Based Spacing Policy for Vehicle Platoons Subject to Disturbances2017Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 62, nr 9, s. 4376-4391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel delay-based spacing policy for the control of vehicle platoons is introduced together with a notion of disturbance string stability. The delay-based spacing policy specifies the desired intervehicular distance between vehicles and guarantees that all vehicles track the same spatially varying reference velocity profile, as is for example required for heavy-duty vehicles driving over hilly terrain. Disturbance string stability is a notion of string stability of vehicle platoons subject to external disturbances on all vehicles that guarantees that perturbations do not grow unbounded as they propagate through the platoon. Specifically, a control design approach in the spatial domain is presented that achieves tracking of the desired spacing policy and guarantees disturbance string stability with respect to a spatially varying reference velocity. The results are illustrated by means of simulations.

  • 74.
    Besselink, Bart
    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.
    Control of platoons of heavy-duty vehicles using a delay-based spacing policy2015Konferansepaper (Fagfellevurdert)
  • 75.
    Besselink, Bart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    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.
    Clustering-based model reduction of networked passive systems2016Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 61, nr 10, s. 2958-2973, artikkel-id 7350110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The model reduction problem for networks of interconnected dynamical systems is studied in this paper. In particular, networks of identical passive subsystems, which are coupled according to a tree topology, are considered. For such networked systems, reduction is performed by clustering subsystems that show similar behavior and subsequently aggregating their states, leading to a reduced-order networked system that allows for an insightful physical interpretation. The clusters are chosen on the basis of the analysis of controllability and observability properties of associated edge systems, representing the importance of the couplings and providing ameasure of the similarity of the behavior of neighboring subsystems. This reduction procedure is shown to preserve synchronization properties (i.e., the convergence of the subsystem trajectories to each other) and allows for the a priori computation of a bound on the reduction error with respect to external inputs and outputs. The method is illustrated by means of an example of a thermal model of a building.

  • 76.
    Besselink, Bart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    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.
    Model reduction of networked passive systems through clustering2014Inngår i: 2014 European Control Conference, ECC 2014, IEEE , 2014, s. 1069-1074Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a model reduction procedure for a network of interconnected identical passive subsystems is presented. Here, rather than performing model reduction on the subsystems, adjacent subsystems are clustered, leading to a reduced-order networked system that allows for a convenient physical interpretation. The identification of the subsystems to be clustered is performed through controllability and observability analysis of an associated edge system and it is shown that the property of synchronization (i.e., the convergence of trajectories of the subsystems to each other) is preserved during reduction. The results are illustrated by means of an example.

  • 77.
    Besselink, Bart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    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), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Imura, Jun-ichi
    Tokyo Institute of Technology.
    Controllability of a class of networked passive linear systems2013Inngår i: Proceedings of the 52nd IEEE Conference on Decision and Control, Florence, Italy, IEEE conference proceedings, 2013, s. 4901-4906Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, controllability properties of networks of diffusively coupled linear systems are considered through the controllability Gramian. For a class of passive linear systems, it is shown that the controllability Gramian can be decomposed into two parts. The first part is related to the dynamics of the individual systems whereas the second part is dependent only on the interconnection topology, allowing for a clear interpretation and efficient computation of controllability properties for a class of networked systems. Moreover, a relation between symmetries in the interconnection topology and controllability is given. The results are illustrated by an example.

  • 78.
    Besselink, Bart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Turri, Valerio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Van De Hoef, Sebastian Hendrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liang, Kuo-Yun
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Scania CV AB, Sweden.
    Alam, A.
    Mårtensson, Jonas
    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.
    Cyber-Physical Control of Road Freight Transport2016Inngår i: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256, Vol. 104, nr 5, s. 1128-1141, artikkel-id 7437386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Freight transportation is of outmost importance in our society and is continuously increasing. At the same time, transporting goods on roads accounts for about 26% of the total energy consumption and 18% of all greenhouse gas emissions in the European Union. Despite the influence the transportation system has on our energy consumption and the environment, road transportation is mainly done by individual long-haulage trucks with no real-time coordination or global optimization. In this paper, we review how modern information and communication technology supports a cyber-physical transportation system architecture with an integrated logistic system coordinating fleets of trucks traveling together in vehicle platoons. From the reduced air drag, platooning trucks traveling close together can save about 10% of their fuel consumption. Utilizing road grade information and vehicle-to-vehicle communication, a safe and fuel-optimized cooperative look-ahead control strategy is implemented on top of the existing cruise controller. By optimizing the interaction between vehicles and platoons of vehicles, it is shown that significant improvements can be achieved. An integrated transport planning and vehicle routing in the fleet management system allows both small and large fleet owners to benefit from the collaboration. A realistic case study with 200 heavy-duty vehicles performing transportation tasks in Sweden is described. Simulations show overall fuel savings at more than 5% thanks to coordinated platoon planning. It is also illustrated how well the proposed cooperative look-ahead controller for heavy-duty vehicle platoons manages to optimize the velocity profiles of the vehicles over a hilly segment of the considered road network.

  • 79. Bicchi, A.
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Palopoli, L.
    Picasso, B.
    Quantised control in distributed embedded systems2004Konferansepaper (Fagfellevurdert)
  • 80.
    Björk, Joakim
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Harnefors, Lennart
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Fundamental Performance Limitations in Utilizing HVDC to Damp Interarea Modes2019Inngår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 34, nr 2, s. 1095-1104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers power oscillation damping (POD) using active power modulation of high-voltage dc transmissions. An analytical study of how the proximity between interarea modal frequencies in two interconnected asynchronous grids puts a fundamental limit to the achievable performance is presented. It is shown that the ratio between the modal frequencies is the sole factor determining the achievable nominal performance. To illustrate the inherent limitations, simulations using a proportional controller tuned to optimize performance in terms of POD are done on a simplified two-machine model. The influence of limited system information and unmodeled dynamics is shown. The analytical result is then further validated on a realistic model with two interconnected 32-bus networks.

  • 81. Boccia, Antonio
    et al.
    Adaldo, Antonio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    di Bernardo, Mario
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Tracking a mobile target by multi-robot circumnavigation using bearing measurements2017Inngår i: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, IEEE , 2017, s. 1076-1081Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we study a problem of target tracking and circumnavigation with a network of autonomous agents. We propose a distributed algorithm to estimate the position of the target and drive the agents to rotate around it while forming a regular polygon and keeping a desired distance. We formally show that the algorithm attains exponential convergence of the agents to the desired polygon if the target is stationary, and bounded convergence if the target is moving with bounded speed. Numerical simulations corroborate the theoretical results and demonstrate the resilience of the network to addition and removal of agents.

  • 82. Borges de Sousa, 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.
    Speranzon, A.
    Silva, J.
    A control architecture for multiple submarines in coordinated search missions2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A control architecture for executing multi-vehicle search algorithms is presented. The proposed hierarchical structure consists of three control layers: maneuver controllers, vehicle supervisors and team controllers. The system model is described as a dynamic network of hybrid automata in the programming language Shift and allows reasoning about specification and dynamical properties in a formal setting. The particular search problem that is studied is that of finding the minimum of a scalar field using a team of autonomous submarines. As an illustration, a coordination scheme based on the Nelder-Mead simplex optimization algorithm is presented and illustrated through simulations.

  • 83. Borges De Sousa, João
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Speranzon, Alberto
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Silva, Jorge
    A control architecture for multiple submarines in coordinated search missions2005Inngår i: Proceedings of the 16th IFAC World Congress, IFAC , 2005, s. 109-114Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A control architecture for executing multi-vehicle search algorithms is presented. The proposed hierarchical structure consists of three control layers: maneuver controllers, vehicle supervisors and team controllers. The system model is described as a dynamic network of hybrid automata in the programming language Shift and allows reasoning about specification and dynamical properties in a formal setting. The particular search problem that is studied is that of finding the minimum of a scalar field using a team of autonomous submarines. As an illustration, a coordination scheme based on the Nelder-Mead simplex optimization algorithm is presented and illustrated through simulations.

  • 84. Borri, A.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Di Benedetto, M. D.
    Pola, G.
    Decentralized symbolic control of interconnected systems with application to vehicle platooning2013Inngår i: IFAC Proceedings Volumes, 2013, nr PART 1, s. 285-292Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work aims at extending some concepts of symbolic control design to decentralized control structures, with an approximate simulation approach. Symbolic models and controllers are based on abstractions of continuous dynamics where one symbol corresponds to an aggregate of continuous states. We consider a serial interconnection of continuous nonlinear systems and we address the decentralized design of local controllers to accomplish a given specification on the overall system. The results are applied to a vehicle platooning problem, where we jointly fulfill a safety constraint (collision avoidance) and reduce the fuel consumption.

  • 85. Briat, C.
    et al.
    Yavuz, E.A
    Hjalmarsson, Håkan
    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.
    Jönsson, Ulf T.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The Conservation of Information, Towards an Axiomatized Modular Modeling Approach to Congestion Control2015Inngår i: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 23, nr 3, s. 851-865Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We derive a modular fluid-flow network congestion control model based on a law of fundamental nature in networks: the conservation of information. Network elements such as queues, users, and transmission channels and network performance indicators like sending/acknowledgment rates and delays are mathematically modeled by applying this law locally. Our contributions are twofold. First, we introduce a modular metamodel that is sufficiently generic to represent any network topology. The proposed model is composed of building blocks that implement mechanisms ignored by the existing ones, which can be recovered from exact reduction or approximation of this new model. Second, we provide a novel classification of previously proposed models in the literature and show that they are often not capable of capturing the transient behavior of the network precisely. Numerical results obtained from packet-level simulations demonstrate the accuracy of the proposed model.

  • 86.
    Briat, Corentin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    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.
    Jönsson, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nonlinear state-dependent delay modeling and stability analysis of internet congestion control2010Inngår i: 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), 2010, s. 1484-1491Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is shown that the queuing delay involved in the congestion control algorithm is state-dependent and does not depend on the current time. Then, using an accurate formulation for buffers, networks with arbitrary topologies can be built. At equilibrium, our model reduces to the widely used setup by Paganini et al. Using this model, the delay-derivative is analyzed and it is proved that the delay time-derivative does not exceed one for the considered topologies. It is then shown that the considered congestion control algorithm globally stabilizes a delay-free single buffer network. Finally, using a specific linearization result for systems with state-dependent delays from Cooke and Huang, we show the local stability of the single bottleneck network.

  • 87.
    Briat, Corentin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    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.
    Jönsson, Ulf T.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Karlsson, Gunnar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Yavuz, Emre Altug
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsnät.
    An axiomatic fluid-flow model for congestion control analysis2011Inngår i: 2011 50th IEEE Conference on Decision and Control andEuropean Control Conference (CDC-ECC), 2011, s. 3122-3129Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An axiomatic model for congestion control isderived. The proposed four axioms serve as a basis for theconstruction of models for the network elements. It is shownthat, under some assumptions, some models of the literature canbe recovered. A single-buffer/multiple-users topology is finallyderived and studied for illustration.

  • 88.
    Cabrera Molero, Inés
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Möller, Niels
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Petersson, Justus
    Skog, Robert
    Arvidsson, Åke
    Flärdh, Oscar
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Cross-layer adaptation for TCP-based applications in WCDMA systems2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider TCP-based applications over a high bandwidth wireless channel, such as the High-Speed Downlink Packet Access (HSDPA) channel in aWCDMAsystem, in two setups: a nominal one that employs end-to-end TCPReno and a new one that employs Cross-Layer Adaptation (CLA) in the form of Radio Network Feedback (RNF). For theCLAsetup, the Radio Resource Management unit in the Radio Network Controller (RNC) provides a proxy with reports on the radio link bandwidth and the queue level. The proxy transport layer takes appropriate actions on these reports. By doing so, it utilizes the air-interface spectrum more efficiently and keeps the layer-2 queue in the RNCclose a predetermined level. These new control mechanisms are evaluated through ns-2 simulations. In a number of realistic use cases it is shown that the new CLAsetup reduces the time to serve users, and substantially increases the radio link utilization and decreases the required buffer size in the RNC.

  • 89.
    Carvalho, J. Frederico
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Robotik, perception och lärande, RPL. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Pequito, S.
    Aguiar, A. P.
    Kar, S.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Composability and controllability of structural linear time-invariant systems: Distributed verification2017Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 78, s. 123-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Motivated by the development and deployment of large-scale dynamical systems, often comprised of geographically distributed smaller subsystems, we address the problem of verifying their controllability in a distributed manner. Specifically, we study controllability in the structural system theoretic sense, structural controllability, in which rather than focusing on a specific numerical system realization, we provide guarantees for equivalence classes of linear time-invariant systems on the basis of their structural sparsity patterns, i.e., the location of zero/nonzero entries in the plant matrices. Towards this goal, we first provide several necessary and/or sufficient conditions that ensure that the overall system is structurally controllable on the basis of the subsystems’ structural pattern and their interconnections. The proposed verification criteria are shown to be efficiently implementable (i.e., with polynomial time-complexity in the number of the state variables and inputs) in two important subclasses of interconnected dynamical systems: similar (where every subsystem has the same structure) and serial (where every subsystem outputs to at most one other subsystem). Secondly, we provide an iterative distributed algorithm to verify structural controllability for general interconnected dynamical system, i.e., it is based on communication among (physically) interconnected subsystems, and requires only local model and interconnection knowledge at each subsystem.

  • 90.
    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.

  • 91. 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)
  • 92.
    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.

  • 93.
    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.

  • 94.
    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.

  • 95.
    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)
  • 96. 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.

  • 97.
    Cicic, Mladen
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik. KTH Royal Inst Technol, Dept Automat Control, Stockholm, Sweden..
    Traffic regulation via individually controlled automated vehicles: a cell transmission model approach2018Inngår i: 2018 21ST INTERNATIONAL CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC), IEEE , 2018, s. 766-771Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The advent of automated, infrastructure-controlled vehicles offers new opportunities for traffic control. Even when the number of controlled vehicles is small, they can significantly affect the surrounding traffic. One way of regulating traffic is by using the automated vehicles as controlled moving bottlenecks. We present an extension of the cell transmission model that includes the influence of moving bottlenecks, consistently with the corresponding PDE traffic model. Based on this model, a control strategy is derived for traffic jam resolution. The strategy is tested in simulations, and shown to reduce the average travel time of surrounding vehicles, while also helping dissipate the traffic jam faster and ensuring the controlled vehicle avoids it.

  • 98.
    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.

  • 99. 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.

  • 100. 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)
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