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  • 301. Jurado, I.
    et al.
    Quevedo, D. E.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ahlén, A.
    Cooperative Dynamic MPC for Networked Control Systems2014Inngår i: Intelligent Systems, Control and Automation: Science and Engineering, ISSN 2213-8986, Vol. 69, s. 357-373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work studies cooperative MPC for Networked Control Systems with multiple wireless nodes. Communication between nodes is affected by random packet dropouts. An algorithm is presented to decide at each time instant which nodes will calculate the control input and which will only relay data. The nodes chosen to calculate the control values solve a cooperative MPC by communicating with their neighbors. This algorithm makes the control architecture flexible by adapting it to the possible changes in the network conditions.

  • 302. Jurado, Isabel
    et al.
    Quevedo, Daniel E.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ahlén, Anders
    Cooperative Dynamic MPC for NCSs2013Inngår i: Distributed MPC Made Easy / [ed] J. M. Maestre and R. R. Negenborn, Eds., Springer-Verlag New York, 2013Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    This work studies cooperative MPC for Networked Control Systems with multiple wireless nodes. Communication between nodes is affected by random packet dropouts. An algorithm is presented to decide at each time instant which nodes will calculate the control input and which will only relay data. The nodes chosen to calculate the control values solve a cooperative MPC by communicating with their neighbors. This algorithm makes the control architecture flexible by adapting it to the possible changes in the network conditions.

    Fulltekst (pdf)
    networked_control_coop_mpc12
  • 303.
    Karasalo, Maja
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Johansson, Linda-Maria
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Multi-robot terrain servoing with proximity sensors2005Inngår i: 2005 IEEE International Conference on Robotics and Automation (ICRA), 2005, s. 2791-2796Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of coordinating a team of robots with heterogeneous sensing capabilities is studied in this paper. A control structure is proposed that combines terrain servoing for the leading robot with on-line formation planning and path following for the followers, while enabling obstacle avoidance for all the robots.

  • 304. Katsilieris, Fotios
    et al.
    Lindhé, Magnus
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ögren, Petter
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Demonstration of multi-robot search and secure2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the search and secure problem, where intruders are to be detected in a bounded area without allowing them to escape. The problem is tackled by representing the area to be searched as a traversability graph, which is reduced to a tree graph by placing stationary robots to remove loops. The search of the remaining tree is performed using two strategies that represent different trade-offs between the needed search time and the number of robots. Proof of correctness is provided for these two strategies. The proposed algorithm was implemented and demonstrated as part of an outfield experiment involving a team of Rotundus spherical robots.

    Fulltekst (pdf)
    multirobot_icra10_workshop
  • 305.
    Keimer, Alexander
    et al.
    Univ Calif Berkeley, Inst Transportat Studies, Berkeley, CA 94720 USA..
    Laurent-Brouty, Nicolas
    Univ Cote dAzur, CNRS, LJAD, INRIA, Nice, France.;Ecole Ponts ParisTech, INRIA, F-06902 Sophia Antipolis Champs, France..
    Farokhi, Farhad
    Univ Melbourne, Dept Elect & Elect Engn, Parkville, Vic 3010, Australia..
    Signargout, Hippolyte
    Ecole Normale Super Lyon, Edole Normale, F-69342 Lyon, France..
    Cvetkovic, Vladimir
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Bayen, Alexandre M.
    Univ Calif Berkeley, Inst Transportat Studies, Berkeley, CA 94720 USA..
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES).
    Information Patterns in the Modeling and Design of Mobility Management Services2018Inngår i: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256, Vol. 106, nr 4, s. 554-576Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of sustainable transportation infrastructure for people and goods, using new technology and business models, can prove beneficial or detrimental for mobility, depending on its design and use. The focus of this paper is on the increasing impact new mobility services have on traffic patterns and transportation efficiency in general. Over the last decade, the rise of the mobile internet and the usage of mobile devices have enabled ubiquitous traffic information. With the increased adoption of specific smartphone applications, the number of users of routing applications has become large enough to disrupt traffic flow patterns in a significant manner. Similarly, but at a slightly slower pace, novel services for freight transportation and city logistics improve the efficiency of goods transportation and change the use of road infrastructure. This paper provides a general four-layer framework for modeling these new trends. The main motivation behind the development is to provide a unifying formal system description that can at the same time encompass system physics (flow and motion of vehicles) as well as coordination strategies under various information and cooperation structures. To showcase the framework, we apply it to the specific challenge of modeling and analyzing the integration of routing applications in today's transportation systems. In this framework, at the lowest layer (flow dynamics), we distinguish routed users from nonrouted users. A distributed parameter model based on a nonlocal partial differential equation is introduced and analyzed. The second layer incorporates connected services (e.g., routing) and other applications used to optimize the local performance of the system. As inputs to those applications, we propose a third layer introducing the incentive design and global objectives, which are typically varying over the day depending on road and weather conditions, external events, etc. The high-level planning is handled on the fourth layer taking social long-term objectives into account. We illustrate the framework by considering its ability to model at two different levels. Specific to vehicular traffic, numerical examples enable us to demonstrate the links between the traffic network layer and the routing decision layer. With a second example on optimized freight transport, we then discuss the links between the cooperative control layer and the lower layers. The congestion pricing in Stockholm is used to illustrate how also the social planning layer can be incorporated in future mobility services.

  • 306. Keviczky, Tamás
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A study on distributed model predictive consensus2008Inngår i: Proceedings of the 17th IFAC World Congress, 2008, 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We investigate convergence properties of a proposed distributed model predictive control (DMPC) scheme, where agents negotiate to compute an optimal consensus point using an incremental subgradient method based on primal decomposition as described in Johansson et al. [2006, 2007]. The objective of the distributed control strategy is to agree upon and achieve an optimal common output value for a group of agents in the presence of constraints on the agent dynamics using local predictive controllers. Stability analysis using a receding horizon implementation of the distributed optimal consensus scheme is performed. Conditions are given under which convergence can be obtained even if the negotiations do not reach full consensus.

    Fulltekst (pdf)
    multiagent_ifac08_dmpc
  • 307. Khan, U. A.
    et al.
    Korniienko, A.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    An H∞-based approach for robust sensor localization2016Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, s. 1719-1724Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the problem of sensor localization, i.e., finding the positions of an arbitrary number of sensors located in a Euclidean space, ?m, given at least m+1 anchors with known locations. Assuming that each sensor knows pairwise distances in its neighborhood and that the sensors lie in the convex hull of the anchors, we provide a DIstributed LOCalization algorithm in Continuous-Time, named DILOCCT, that converges to the sensor locations. This representation is linear and is further decoupled in the coordinates. By adding a proportional controller in the feed-forward loop of each location estimator, we show that the convergence speed of DILOC-CT can be made arbitrarily fast. Since a large gain may result into unwanted transients especially in the presence of disturbance introduced, e.g., by communication noise in the network, we use H∞ theory to design local controllers that guarantee certain global performance while maintaining the desired steady-state. Simulations are provided to illustrate the concepts described in this paper.

  • 308. Khan, Usman A.
    et al.
    Korniienko, Anton
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    An H-infinity-based approach for robust sensor localization2015Inngår i: 2015 54TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 1719-1724Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the problem of sensor localization, i.e., finding the positions of an arbitrary number of sensors located in a Euclidean space, R-m, given at least m + 1 anchors with known locations. Assuming that each sensor knows pairwise distances in its neighborhood and that the sensors lie in the convex hull of the anchors, we provide a DIstributed LOCalization algorithm in Continuous-Time, named DILOC-CT, that converges to the sensor locations. This representation is linear and is further decoupled in the coordinates. By adding a proportional controller in the feed-forward loop of each location estimator, we show that the convergence speed of DILOC-CT can be made arbitrarily fast. Since a large gain may result into unwanted transients especially in the presence of disturbance introduced, e.g., by communication noise in the network, we use H-infinity theory to design local controllers that guarantee certain global performance while maintaining the desired steady-state. Simulations are provided to illustrate the concepts described in this paper.

  • 309.
    Kiener, Georg Alexander
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lehmann, Daniel
    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.
    Actuator saturation and anti-windup compensation in event-triggered control2014Inngår i: Discrete event dynamic systems, ISSN 0924-6703, E-ISSN 1573-7594, Vol. 24, nr 2, s. 173-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Event-triggered control aims at reducing the communication load over the feedback link in networked control systems by sending information only if certain event conditions, which guarantee a desired control performance, are satisfied. This article investigates the consequences of actuator saturation on the behavior of the event-triggered control loop in terms of its stability and information exchange. Stability properties are derived using linear matrix inequalities (LMIs) which show how the stability of the event-triggered control loop depends on the selection of the event threshold. Moreover, it is shown that a lower bound on the minimum inter-event time exists being likewise affected by the event threshold. As actuator saturation might severely degrade the performance of the event-triggered closed-loop system, the scheme is extended by incorporating an anti-windup mechanism in order to overcome this problem. The results are illustrated by simulations and experiments.

    Fulltekst (pdf)
    event_deds12
  • 310.
    Kim, Dohwan
    et al.
    DGIST, Daegu, South Korea..
    Won, Yuchang
    DGIST, Daegu, South Korea..
    Kim, Seunghyeon
    DGIST, Daegu, South Korea..
    Eun, Yongsoon
    DGIST, Daegu, South Korea..
    Park, Kyung-Joon
    DGIST, Daegu, South Korea..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Sampling Rate Optimization for IEEE 802.11 Wireless Control Systems2019Inngår i: ICCPS '19: PROCEEDINGS OF THE 2019 10TH ACM/IEEE INTERNATIONAL CONFERENCE ON CYBER-PHYSICAL SYSTEMS / [ed] Ramachandran, GS Ortiz, J, ASSOC COMPUTING MACHINERY , 2019, s. 87-96Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Design of wireless control systems has been extensively studied, which is one of the fundamental issues in cyber-physical systems. In this paper, we empirically investigate heterogeneous sampling rate assignment with a testbed when multiple physical systems are controlled through an IEEE 802.11 network. Among the critical design variables in wireless control systems, we focus on the sampling rates because they are always key control knobs regardless of network protocols. There has been little experimental research on heterogeneous sampling rate optimization for IEEE 802.11 wireless control systems, where the sampling rates of each control loop may have different values. We first formulate the co-design problem in an optimization framework with respect to the heterogeneous sampling rates by explicitly taking into account the relations of the sampling rates with the control cost, network energy consumption, and network delay. We further relax the problem as convex optimization, which is provably solved in polynomial time. Our empirical study ensures that the approximate solution is tightly close to the original optimum. To validate the proposed optimization framework, we build a disk-levitation tube testbed, which wirelessly controls the height of 20 disks at the same time. Our empirical study confirms that our optimization formulation is highly effective in practice.

  • 311. Kim, W.
    et al.
    Stankovic, M. S.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kim, H. J.
    A distributed support vector machine learning over wireless sensor networks2015Inngår i: IEEE Transactions on Cybernetics, ISSN 2168-2267, E-ISSN 2168-2275, Vol. 45, nr 11, s. 2599-2611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is about fully-distributed support vectormachine (SVM) learning over wireless sensor networks. With theconcept of the geometric SVM, we propose to gossip the set ofextreme points of the convex hull of local data set with neighboringnodes. It has the advantages of a simple communicationmechanism and finite-time convergence to a common global solution.Furthermore, we analyze the scalability with respect to theamount of exchanged information and convergence time, witha specific emphasis on the small-world phenomenon. First, withthe proposed naive convex hull algorithm, the message lengthremains bounded as the number of nodes increases. Second, byutilizing a small-world network, we have an opportunity to drasticallyimprove the convergence performance with only a smallincrease in power consumption. These properties offer a greatadvantage when dealing with a large-scale network. Simulationand experimental results support the feasibility and effectivenessof the proposed gossip-based process and the analysis.

  • 312.
    Koller, Julian Phillip Johann
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Grossmann Colin, Alex
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Besselink, Bart
    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.
    Fuel-Efficient Control of Merging Maneuvers for Heavy-Duty Vehicle Platooning2015Inngår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, IEEE conference proceedings, 2015, s. 1702-1707Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The formation of groups of closely-spaced heavy-duty vehicles, known as platoons, reduces the overall aerodynamic drag and therefore leads to reduced fuel consumption and reduced greenhouse gas emissions. This paper focuses on the optimal control of merging maneuvers for the formation of a growing platoon. Hereto, the merging problem is formulated as a hybrid optimal control problem and an algorithm for the computation of optimal merging times and corresponding optimal vehicle trajectories is developed by exploiting an extension of Pontryagin's maximum principle. Moreover, a model predictive control approach on the basis of this algorithm is presented that makes the merging maneuvers robust to modelling uncertainties and external disturbances. The results are illustrated by evaluating a scenario involving three vehicles, which indicates fuel savings of up to 13% with respect to the vehicles driving alone.

  • 313.
    Larson, Jeffrey
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kammer, Christoph
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Liang, Kuo-Yun
    Research and Developement, Scania CV AB.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Coordinated route optimization for heavy-duty vehicle platoons2013Inngår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, IEEE conference proceedings, 2013, s. 1196-1202Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heavy-duty vehicles traveling in platoons consume fuel at a reduced rate. In this paper, we attempt to maximize this benefit by introducing local controllers throughout a road network to facilitate platoon formations with minimal information. By knowing a vehicle's position, speed, and destination, the local controller can quickly decide how its speed should be possibly adjusted to platoon with others in the near future. We solve this optimal control and routing problem exactly for small numbers of vehicles, and present a fast heuristic algorithm for real-time use. We then implement such a distributed control system through a large-scale simulation of the German autobahn road network containing thousands of vehicles. The simulation shows fuel savings from 1-9%, with savings exceeding 5% when only a few thousand vehicles participate in the system. We assume no vehicles will travel more than the time required for their shortest paths for the majority of the paper. We conclude the results by analyzing how a relaxation of this assumption can further reduce fuel use.

    Fulltekst (pdf)
    fulltext
  • 314. Larson, Jeffrey
    et al.
    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 .
    Johanson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A Distributed Framework for Coordinated Heavy-Duty Vehicle Platooning2015Inngår i: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 16, nr 1, s. 419-429Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heavy-duty vehicles (HDVs) traveling in single file with small intervehicle distances experience reduced aerodynamic drag and, therefore, have improved fuel economy. In this paper, we attempt to maximize the amount of fuel saved by coordinating platoon formation using a distributed network of controllers. These virtual controllers, placed at major intersections in a road network, help coordinate the velocity of approaching vehicles so they arrive at the junction simultaneously and can therefore platoon. This control is initiated only if the cost of forming the platoon is smaller than the savings incurred from platooning. In a largescale simulation of the German Autobahn network, we observe that savings surpassing 5% when only a few thousand vehicles participate in the system. These results are corroborated by an analysis of real-world HDV data that show significant platooning opportunities currently exist, suggesting that a slightly invasive network of distributed controllers, such as the one proposed in this paper, can yield considerable savings.

  • 315.
    Larsson, Martin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lindberg, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lycke, Jens
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Hansson, Karl
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Khakulov, Aziz
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Ringh, Emil
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Svensson, Fredrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Tjernberg, Isak
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Alam, Assad
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Araujo, Jose
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Farokhi, Farhad
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Ghadimi, Euhanna
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Teixeira, Andre
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    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.
    Towards an Indoor Testbed for Mobile Networked Control Systems2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the design of an indoor testbed composed of multiple aerial and ground unmanned vehicles for experimentation in Mobile Networked Control Systems. Taking several motivational aspects from both research and education into account, we propose an architecture to cope with the scale and mobility aspects of the overall system. Currently, the testbed is composed of several low-cost ARdrones quadrotors, small-scale heavy duty vehicles, wireless sensor nodes and a vision-based localization system. As an example, the automatic control of an ARdrone is shown.

    Fulltekst (pdf)
    fulltext
  • 316. Lee, Seung Jae
    et al.
    Kim, Suseong
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kim, H. Jin
    Robust Acceleration Control of a Hexarotor UAV with a Disturbance Observer2016Inngår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 4166-4171, artikkel-id 7798901Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an acceleration control of a hexarotor unmanned aerial vehicle (UAV) in the earth fixed frame with a disturbance observer (DOB). Unlike conventional cascade control structures where the outer-loop position controller generates the desired attitude command, the position controller in this paper generates the desired acceleration command in X, V. Z axis of the earth-fixed frame. With acceleration control combined with DOB, the UAV could manage the lateral disturbance force that makes the trajectory tracking very challenging. This is a new concept compared with existing DOB-based UAV control approaches which aim to cancel the moment disturbance for precise attitude control. The small-gain theorem is used for stability analysis and Q-filter bandwidth design. Both simulation and actual experiment are shown to validate the performance of the proposed design.

  • 317.
    Lehmann, Daniel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Henriksson, Erik
    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 Model Predictive Control of Discrete-Time Linear Systems Subject to Disturbances2013Inngår i: 2013 European Control Conference (ECC), IEEE , 2013, s. 1156-1161Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an approach to event-triggered model predictive control for discrete-time linear systems subject to input and state constraints as well as exogenous disturbances. Stability properties are derived by evaluating the difference between the event-triggered implementation and the conventional time-triggered scheme. It is shown that the event-triggered implementation, in stationarity, is able to keep the state in an explicitly computable set given by the disturbance bound and the event threshold. Simulation results underline the effectiveness of the proposed scheme in terms of reducing the communication and computational effort while guaranteeing a desired performance.

  • 318.
    Lehmann, Daniel
    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 PI control subject to actuator saturation2012Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline) v2 Part 1, 2012, s. 430-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Event-triggered control aims at reducing the communication load over the feedback link in networked control systems by adapting the information exchange to the current needs. This paper firstly extends a common approach to event-triggered control by incorporating a PI controller and by showing the setpoint-tracking properties of the extended scheme. Second, it investigates the consequences of actuator saturation on the behavior of the event-triggered PI-control loop. Simulations show that the effect of actuator saturation depends on the selection of the event threshold which might even destabilize the closed-loop system due to integrator windup. Finally anti-windup techniques are discussed to overcome this problem.

  • 319.
    Lehmann, Daniel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Kiener, Georg Alexander
    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.
    Event-triggered PI control: Saturating actuators and anti-windup compensation2012Inngår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE conference proceedings, 2012, s. 6566-6571Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Event-triggered control aims at reducing the communication load over the feedback link in networked control systems by adapting the information exchange to the current needs. This paper investigates the consequences of actuator saturation on the behavior of event-triggered PI control. Stability properties are derived using linear matrix inequalities (LMIs) which show how the stability of the event-triggered control loop depends on the selection of the event threshold. In order to overcome the potential performance degradation due to integrator windup caused by actuator saturation, the proposed scheme is extended by incorporating a static anti-windup mechanism. The results are illustrated by simulations.

    Fulltekst (pdf)
    fulltext
  • 320.
    Lehmann, Daniel
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Lunze, J.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Comparison between sampled-data control, deadband control and model-based event-triggered control2012Inngår i: 4th IFAC Conference on Analysis and Design of Hybrid Systems, IFAC , 2012, s. 7-12Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the stability as well as communication properties of sampleddata control and two event-triggered control schemes: deadband control and model-based eventtriggered control. After proposing a uniform representation, these schemes are compared by deriving approximation error bounds with respect to the behavior of the continuous-time statefeedback loop and by specifying lower bounds on the minimum inter-sampling times. The results show that, under the conditions derived in this paper, the model-based approach guarantees the best stability and communication properties which is also demonstrated by a numerical example.

  • 321. Leong, A. S.
    et al.
    Quevedo, D. E.
    Ahlén, A.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Network topology reconfiguration for state estimation over sensor networks with correlated packet drops2014Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline), IFAC Papers Online, 2014, s. 5532-5537Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies the problem of optimal network topology reconfiguration in sensor networks for state estimation. Multiple sensors make observations of a process, which are then transmitted, possibly via intermediate sensors, to a central gateway. Transmission over each link can experience packet drops. The time-varying wireless network environment is modelled by the notion of a network state as in Quevedo et al. (2013a). For each network state, different network configurations can be used, which govern the network topology and routing of packets. Switching between different configurations incurs a cost, in that unwanted links will need to be removed before the establishment of new links, leading to a transient time in which some links may not be available. The problem is to determine the optimal network configurations to use in each network state, in order to minimize an expected error covariance measure that takes into account the cost of reconfiguration. A simpler suboptimal method which minimizes the upper bound of the expected error is also proposed, which in numerical simulations gives essentially identical results to the optimal method.

  • 322. Leong, Alex S.
    et al.
    Quevedo, Daniel E.
    Ahlen, Anders
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    On Network Topology Reconfiguration for Remote State Estimation2016Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 61, nr 12, s. 3842-3856Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we investigate network topology reconfiguration in wireless sensor networks for remote state estimation, where sensor observations are transmitted, possibly via intermediate sensors, to a central gateway/estimator. The time-varying wireless network environment is modelled by the notion of a network state process, which is a randomly time-varying semi-Markov chain and determines the packet reception probabilities of links at different times. For each network state, different network configurations can be used, which govern the network topology and routing of packets. The problem addressed is to determine the optimal network configuration to use in each network state, in order to minimize an expected error covariance measure. Computation of the expected error covariance cost function has a complexity of O(2(M Delta max)), where M is the number of sensors and Delta max is the maximum time between transitions of the semi-Markov chain. A sub-optimal method which minimizes the upper bound of the expected error covariance, that can be computed with a reduced complexity of O(2(M)), is proposed, which in many cases gives identical results to the optimal method. Conditions for estimator stability under both the optimal and suboptimal reconfiguration methods are derived using stochastic Lyapunov functions. Numerical results and comparisons with other low complexity approaches demonstrate the performance benefits of our approach.

  • 323. Li, K.
    et al.
    Rojas, Cristian R.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Yang, T
    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.
    Distributed Signal Recovery Via Piecewise Orthogonal Matching Pursuit and Finite-Time Consensus2014Inngår i: IEEE Explore, Institute of Electrical and Electronics Engineers (IEEE), 2014Konferansepaper (Fagfellevurdert)
  • 324.
    Li, Kezhi
    et al.
    Imperial College London, United Kingdom.
    Rojas, Cristian R.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Yang, Tao
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Cong, S.
    Piecewise sparse signal recovery via piecewise orthogonal matching pursuit2016Inngår i: 2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 4608-4612Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the recovery of piecewise sparse signals from incomplete noisy measurements via a greedy algorithm. Here piecewise sparse means that the signal can be approximated in certain domain with known number of nonzero entries in each piece/segment. This paper makes a two-fold contribution to this problem: 1) formulating a piecewise sparse model in the framework of compressed sensing and providing the theoretical analysis of corresponding sensing matrices; 2) developing a greedy algorithm called piecewise orthogonal matching pursuit (POMP) for the recovery of piecewise sparse signals. Experimental simulations verify the effectiveness of the proposed algorithms.

  • 325.
    Li, Yuchao
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Integrated Transport Research Lab, ITRL.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för industriell teknik och management (ITM), Centra, Integrated Transport Research Lab, ITRL.
    Mårtensson, Jonas
    KTH, Skolan för industriell teknik och management (ITM), Centra, Integrated Transport Research Lab, ITRL. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik.
    A hierarchical control system for smart parking lots with automated vehicles: Improve efficiency by leveraging prediction of human drivers2019Inngår i: Proceedings 2019 18TH EUROPEAN CONTROL CONFERENCE (ECC), IEEE , 2019, s. 2675-2681Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this work, we introduce a hierarchical architecture for management of multiple automated vehicles in a parking lot provided the existence of human-driven vehicles. The proposed architecture consists of three layers: behavior prediction, vehicle coordination and maneuver control, with the first two sitting in the infrastructure and the third one equipped on individual vehicles. We assume all three layers share a consistent view of the environment by considering it as a grid world. The grid occupancy is modeled by the prediction layer via collecting information from automated vehicles and predicting human-driven vehicles. The coordination layer assigns parking spots and grants permissions for vehicles to move. The vehicle control embraces the distributed model predictive control (MPC) technique to resolve local conflicts occurred due to the simplified vehicle models used in the design of the prediction and coordination layers. Numerical evaluation shows the effectiveness of the proposed control system.

  • 326. Liang, K. -Y
    et al.
    Martensson, 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.
    When is it fuel eficient for a heavy duty vehicle to catch up with a platoon?2013Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline), 2013, nr PART 1, s. 738-743Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle platooning has in recent years become an important research field for the vehicle industry. By establishing a platoon of heavy duty vehicles, the fuel consumption can be reduced for the follower vehicles due to the slipstream effect. However, as vehicles are scattered on the road driving by themselves, coordination amongst the vehicles is required. In this paper we study the problem of when it is beneficial for a heavy duty vehicle to drive faster in order to catch up and join a platoon. We derive a formula, based on at road and with no vehicle accelerations, to calculate if it is more fuel-eficient for a vehicle to drive faster and platoon or keep driving alone. Depending on the distance between the vehicles and the distance to the destination, the fuel savings vary. For a trip of 350 km, with a distance of 10km to the vehicle ahead, the fuel saving could be up to 7% if the follower vehicle decides to increase the speed from 80 km/h to 90 km/h in order to catch up and form a platoon, assuming an air drag reduction of 32% when platooning. Sensitivity analysis has shown that the speeds need to be relatively accurate in order to not give any false positive catch up decisions.

  • 327.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. Scania CV AB, Sweden.
    Deng, Qichen
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Transportplanering, ekonomi och teknik.
    Mårtensson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Ma, Xiaoliang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Transportplanering, ekonomi och teknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The Influence of Traffic on Heavy-Duty Vehicle Platoon Formation2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heavy-duty vehicle (HDV) platooning is a mean to significantly reduce the fuel consumption for the trailing vehicle. By driving close to the vehicle in front, the air drag is reduced tremendously. Due to each HDV being assigned with different transport missions, platoons will need to be frequently formed, merged, and split. Driving on the road requires interaction with surrounding traffic and road users, which will influence how well a platoon can be formed. In this paper, we study how traffic may affect a merging maneuver of two HDVs trying to form a platoon. We simulate this for different traffic densities and for different HDV speeds. Even on moderate traffic density, a platoon merge could be delayed with 20% compared to the ideal case with no traffic. 

    Fulltekst (pdf)
    fulltext
  • 328.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. Scania CV AB, Sweden.
    Mårtensson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Experiments on Platoon Formation of Heavy Trucks in Traffic2016Inngår i: 2016 IEEE 19TH INTERNATIONAL CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC), IEEE, 2016, s. 1813-1819Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Truck platooning is a means to significantly reduce the fuel consumption for the follower vehicle as the air drag is reduced when the inter-vehicle gap between the trucks is reduced. As each truck is assigned with different start and end locations, platoons will be frequently formed and split, while driving to their respective destinations. Additionally, the trucks are not the only ones driving on the road as there are other road users, which may influence how well a platoon can be formed. In this paper, an experimental study is conducted to investigate how traffic may affect a merging maneuver of two trucks trying to form a platoon on a public highway during rush hours. We obtained traffic data from Stockholm's motorway control system to determine the traffic condition for each testrun. Furthermore, we tried different truck speeds to study if it had any impacts on merge delay. Even in light traffic condition, a platoon merge could be delayed with over 10 % compared to the ideal case with the absence of traffic. This is partially caused by persistent drivers in which we encountered them in a fourth of the runs.

  • 329.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Scania CV AB, Sweden.
    Mårtensson, Jonas
    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.
    Fuel-Saving Potentials of Platooning Evaluated through Sparse Heavy-Duty Vehicle Position Data2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle platooning is important for heavy-duty vehicle manufacturers, due to the reduced aerodynamic drag for the follower vehicles, which gives an overall lower fuel consumption. Heavy-duty vehicle drivers are aware this fact and sometimes drive close to other heavy-duty vehicles. However, it is not currently well known how many vehicles are actually driving in such spontaneous platoons today. This paper studies the platooning rate of 1,800 heavy-duty vehicles by analyzing sparse vehicle position data from a region in Europe during one day. Map-matching and path-inference algorithms are used to determine which paths the vehicles took. The spontaneous platooning rate is found to be 1.2 %, which corresponds to a total fuel saving of 0.07% compared to if none of the vehicles were platooning. Furthermore, we introduce several virtual coordination schemes. We show that coordinations can increase the platooning rate and fuel saving with a factor of ten with minor adjustments from the current travel schedule. The platooning rate and fuel savings can be significantly greater if higher flexibility is allowed.

    Fulltekst (pdf)
    fulltext
  • 330.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Mårtensson, Jonas
    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.
    Heavy-Duty Vehicle Platoon Formation for Fuel Efficiency2016Inngår i: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 17, nr 4, s. 1051-1061Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heavy-duty vehicles driving close behind each other, also known as platooning, experience a reduced aerodynamic drag, which reduces the overall fuel consumption up to 20% for the trailing vehicle. However, due to each vehicle being assigned with different transport missions (with different origins, destinations, and delivery times), platoons should be formed, split, and merged along the highways, and vehicles have to drive solo sometimes. In this paper, we study how two or more scattered vehicles can cooperate to form platoons in a fuel-efficient manner. We show that when forming platoons on the fly on the same route and not considering rerouting, the road topography has a negligible effect on the coordination decision. With this, we then formulate an optimization problem when coordinating two vehicles to form a platoon. We propose a coordination algorithm to form platoons of several vehicles that coordinates neighboring vehicles pairwise. Through a simulation study with detailed vehicle models and real road topography, it is shown that our approach yields significant fuel savings.

  • 331.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Mårtensson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    When is it Fuel Efficient for a Heavy Duty Vehicle to Catch Up With a Platoon?2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Vehicle platooning has in recent years become an important research eld for thevehicle industry. By establishing a platoon of heavy duty vehicles, the fuel consumption can bereduced for the follower vehicles due to the slipstream eect. However, as vehicles are scatteredon the road driving by themselves, coordination amongst the vehicles is required. In this paperwe study the problem of when it is benecial for a heavy duty vehicle to drive faster in orderto catch up and join a platoon. We derive a formula, based on at road and with no vehicleaccelerations, to calculate if it is more fuel-ecient for a vehicle to drive faster and platoonor keep driving alone. Depending on the distance between the vehicles and the distance to thedestination, the fuel savings vary. For a trip of 350 km, with a distance of 10km to the vehicleahead, the fuel saving could be up to 7% if the follower vehicle decides to increase the speed from80 km/h to 90 km/h in order to catch up and form a platoon, assuming an air drag reductionof 32% when platooning. Sensitivity analysis has shown that the speeds need to be relativelyaccurate in order to not give any false positive catch up decisions.

    Fulltekst (pdf)
    fulltext
  • 332.
    Liang, Kuo-Yun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    van de Hoef, Sebastian
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Terelius, Hakan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Turri, Valerio
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Besselink, Bart
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Martensson, Jonas
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Networked control challenges in collaborative road freight transport2016Inngår i: European Journal of Control, ISSN 0947-3580, E-ISSN 1435-5671, Vol. 30, s. 2-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Freight transport is of major importance for the European economy and is growing thanks to increasing global trade. About three quarters of inland freight transport in the European Union is on roads. It has the potential to go through a dramatic change over the next decades thanks to the recent development of technologies such as wireless communication, cloud computing, sensor devices, and vehicle electronics. They enable a new integrated goods transport system based on optimized logistics, real-time traffic information, vehicular communications, collaborative driving, and autonomous vehicles. In this paper, we discuss challenges in creating a more efficient and sustainable goods road transportation system and how some of them can be tackled with a networked control approach. In particular, we discuss a method to improve the efficiency of the transportation system by minimizing the number of empty transports needed to fulfill the assignments on a given road network. Assignments with overlapping route segments might lead to further improvements, as the formation of vehicle platoons yields reduced fuel consumption. For realistic scenarios, it is shown that such collaboration opportunities arise already with relatively few vehicles. The fuel-efficient formation and control of platoons is also discussed. Some of the presented methods have been tested on real vehicles in traffic. The paper shows experimental results on automatic formation of vehicle platoons on a Swedish highway. The influence of traffic density on the merge maneuver is illustrated. The results indicate that platoon coordination could be improved by support from appropriate traffic monitoring technologies.

  • 333. Libal, U.
    et al.
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Reglerteknik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Yule-Walker Equations Using Higher Order Statistics for Nonlinear Autoregressive Model2019Inngår i: 2019 Signal Processing Symposium, SPSympo 2019, Institute of Electrical and Electronics Engineers Inc. , 2019, s. 227-231Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents the derivation of Yule-Walker equations for the nonlinear autoregressive model NAR(p) of a time-series. The proposed method allows for easy calculation of parameters of the model. In the determined equations, higher order statistics are used, instead of autocovariances. For the linear autoregressive model AR(p), the standard Yule-Walker equations are directly based on autocovariances of time-series, or equivalently autocorrelations if the equations are rescaled. Unfortunately, it does not apply for nonlinear model. The authors show a compact matrix notation of Yule-Walker equations for the nonlinear autoregressive model with the nonlinearity of polynomial type of degree 2, with the use of higher order statistics up to 4th order, and numerical examples for electromyography signals for different hand movements.

  • 334.
    Lindhé, M.
    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.
    USING ROBOT MOBILITY TO EXPLOIT MULTIPATH FADING2009Inngår i: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 16, nr 1, s. 30-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Communication-aware motion control allows mobile networked robots to increase the average communication throughput. We exploit that in a multipath fading channel, robots can measure the SNR and adapt their motion to spend slightly more time at positions where the channel is good. Two new such cross-layer strategies are analyzed and evaluated: periodic stopping, where the stop duration is a function of the SNR, and controlled stopping, where the robot stops when the communication buffer is filling up. It is shown that the expected average channel capacity can be twice as high as when no cross-layer information is utilized. Experimental evaluation of the strategies confirms the theoretical results.

    Fulltekst (pdf)
    fulltext
  • 335.
    Lindhé, Magnus
    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 formation control algorithm using Voronoi regions2007Inngår i: Taming Heterogeneity and Complexity of Embedded Control / [ed] Françoise Lamnabhi-Lagarrigue, Antonio Loria, Elena Panteley, Salah Laghrouche, John Wiley & Sons, 2007Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    We present an algorithm for stabilizing a hexagonal lattice formation of autonomous robotic agents. The algorithm is decentralized and each agent only needs to detect the relative positions of its neighbors. By partitioning the plane into Voronoi regions we can guarantee collision safety, even when the algorithm is used to produce waypoints for a non-holonomic agent to follow. In each iteration every agent moves to the centroid of the vertices of its Voronoi region, which yields formation cohesion. We define asymptotic formation stability that is independent of rotation or translation of the whole formation and prove local asymptotic stability. Finally we present simulations that confirm the stability analysis and illustrate the use of the algorithm with car-like robots.

    Fulltekst (pdf)
    multirobot_cts-hycon06
  • 336.
    Lindhé, Magnus
    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 formation control algorithm using Voronoi regions2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an algorithm for stabilizing a hexagonal lattice formation of autonomous robotic agents. The algorithm is decentralized and each agent only needs to detect the relative positions of its neighbors. By partitioning the plane into Voronoi regions we can guarantee collision safety, even when the algorithm is used to produce waypoints for a non-holonomic agent to follow. In each iteration every agent moves to the centroid of the vertices of its Voronoi region, which yields formation cohesion. We define asymptotic formation stability that is independent of rotation or translation of the whole formation and prove local asymptotic stability. Finally we present simulations that confirm the stability analysis and illustrate the use of the algorithm with car-like robots.

    Fulltekst (pdf)
    multirobot_cts-hycon06
  • 337.
    Lindhé, Magnus
    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.
    Adaptive Exploitation of Multipath Fading for Mobile Sensors2010Inngår i: 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) / [ed] Rakotondrabe M; Ivan IA, IEEE , 2010, s. 1934-1939Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mobile wireless sensors in indoor environments will experience multipath fading, causing rapid variations in the capacity of the radio link. We present a strategy that increases the throughput by modifying the trajectory of the sensor so it spends more time at positions where the capacity is high. While doing so, it still maintains some desired average velocity. Our approach includes closed-loop estimation of the parameters of the fading, which may change when moving between rooms. We prove stability of the feedback system and illustrate its behavior through simulations. Finally, we demonstrate robustness to errors in the channel model.

    Fulltekst (pdf)
    communication-aware_robotics_icra10
  • 338.
    Lindhé, Magnus
    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), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Communication-aware trajectory tracking2008Inngår i: 2008 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, IEEE , 2008, s. 1519-1524Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the scenario of a robot making a tradeoff between tracking a time-varying reference trajectory and stopping to communicate at points where the radio signal strength is high. Under the assumption that the signal is subject to multipath fading, we formulate this as a hybrid optimal control problem with penalties on tracking error, communication buffer length and control power. The problem is then solved using relaxed dynamic programming, resulting in control laws for the discrete switching sequence and the continuous control. We finally illustrate the results through simulations under non-ideal conditions, confirming that the system maintains a bounded buffer size and zero-mean tracking error.

    Fulltekst (pdf)
    fulltext
  • 339.
    Lindhé, Magnus
    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.
    Bicchi, A.
    An experimental study of exploiting multipath fading for robot communications2008Inngår i: Proceedings of Robotics: Science and Systems, 2008, s. 289-296Konferansepaper (Fagfellevurdert)
    Abstract [en]

     A simple approach for mobile robots to exploit multipath fading in order to improve received radio signal strength (RSS), is presented. The strategy is to sample the RSS at discrete points, without deviating too far from the desired  position. We first solve the problem of how many samples are needed for given communications performance and how they should be spaced. Second, we propose a circular and a grid trajectory for sampling and give lower bounds on how many samples they will yield. Third, we estimate the parameters of our strategy from measurements. Finally we demonstrate the validity of our analysis through experiments.

    Fulltekst (pdf)
    robot-comm_rss07
  • 340.
    Lindhé, Magnus
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Keviczky, Tamas
    TU Delft.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Multi-Robot Path Following with Visual Connectivity2011Inngår i: Conference Record: Asilomar Conference on Signals, Systems and Computers, IEEE , 2011, s. 1466-1471Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider a group of N robots moving through an obstacle field, where only robots that have a clear line of sight can communicate. When passing the obstacles, the group must coordinate its motion to remain connected. We propose using the path–velocity decomposition: Given obstacle-free paths that fulfill a higher-level goal, we propose a method to coordinate the robot motions along the paths so visual connectivity is maintained. The problem is shown to be equivalent to finding a path through an N-dimensional configuration space, avoiding unconnected configurations. We solve this problem with a rapidly exploring random tree algorithm and demonstrate by simulations how the solution time varies with the obstacle density.

    Fulltekst (pdf)
    lindhe2011mrp
  • 341.
    Lindhé, Magnus
    et al.
    Swedish Defence Research Agency.
    Ögren, Petter
    Swedish Defence Research Agency.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Flocking with obstacle avoidance: A new distributed coordination algorithm based on Voronoi partitions2005Inngår i: 2005 IEEE International Conference on Robotics and Automation (ICRA), Vols 1-4, IEEE , 2005, s. 1785-1790Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new distributed coordination algorithm for multi-vehicle systems is presented in this paper. The algorithm combines a particular choice of navigation function with Voronoi partitions. This results not only in obstacle avoidance and motion to the goal, but also in a desirable geographical distribution of the vehicles. Our algorithm is decentralized in that each vehicle needs only to know the position of neighboring vehicles, but no other inter-vehicle communication or centralized control are required. The algorithm gives a natural priority to safety, goal convergence, and formation keeping, in that (1) collision avoidance is guaranteed under all circumstances, (2) the vehicles will move toward the goal as long as a given optimization problem is feasible, and (3) if prior criteria admit, the vehicles tend to a desirable lattice formation. These theoretical properties are discussed in the paper and the performance of the algorithm is illustrated in simulations with realistic models of twenty all-terrain vehicles. Planned experimental evaluation using customized miniature cars is also briefly described.

    Fulltekst (pdf)
    multirobot_icra05
  • 342.
    Liu, Hanxiao
    et al.
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore, Singapore..
    Yan, Jiaqi
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore, Singapore..
    Mo, Yilin
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore, Singapore..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    An On-line Design of Physical Watermarks2018Inngår i: 2018 IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2018, s. 440-445Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers the problem of designing physical watermark signals to protect a control system against replay attacks. We first introduce the replay attack model, where an adversary replays the previous sensory data in order to fool the controller to believe the system is still operating normally. The physical watermarking scheme, which leverages a random control input as a watermark to detect the replay attack is introduced. The optimal watermark signal design problem is then proposed as an optimization problem, which achieves the optimal trade-off between the control performance and attack detection performance. For the system with unknown parameters, we provide a procedure to asymptotically derive the optimal watermarking signal. Numerical examples are provided to illustrate the effectiveness of the proposed strategy.

  • 343. Liu, K.
    et al.
    Fridman, E.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Xia, Y.
    Generalized Jensen inequalities with application to stability analysis of systems with distributed delays over infinite time-horizons2016Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 69, s. 222-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Jensen inequality has been recognized as a powerful tool to deal with the stability of time-delay systems. Recently, a new inequality that encompasses the Jensen inequality was proposed for the stability analysis of systems with finite delays. In this paper, we first present a generalized integral inequality and its double integral extension. It is shown how these inequalities can be applied to improve the stability result for linear continuous-time systems with gamma-distributed delays. Then, for the discrete-time counterpart we provide an extended Jensen summation inequality with infinite sequences, which leads to less conservative stability conditions for linear discrete-time systems with Poisson-distributed delays. The improvements obtained by the introduced generalized inequalities are demonstrated through examples.

  • 344. Liu, K.
    et al.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fridman, E.
    Xia, Y.
    Stability analysis of discrete-time systems with poisson-distributed delays2016Inngår i: Proceedings of the IEEE Conference on Decision and Control, IEEE conference proceedings, 2016, s. 7736-7741Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper is concerned with the stability analysis of linear discrete-time systems with poisson-distributed delays. Firstly, the exponential stability condition of system with poisson-distributed delays is derived when the corresponding system with the zero-delay or the system without the delayed term is asymptotically stable. Then, an augmented Lyapunov functional is suggested to handle the case that the corresponding system without the delay as well as the system without the delayed term are not necessary to be asymptotically stable. Furthermore, we show that the results can be further improved by formulating the system as a higher-order augmented one and applying the corresponding augmented Lyapunov functional. Finally, the efficiency of the proposed results is illustrated by some numerical examples.

  • 345.
    Liu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fridman, Emilia
    Tel Aviv University.
    Henrik Johansson, Karl
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Networked Control with a Stochastic Scheduling: a Time-Delay  Approach2014Inngår i: The 19th World Congress of IFAC, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper is concerned with the stability analysis of networked control systems with communication constraints, variable delays and variable sampling intervals.The scheduling of sensor communication is defined by a stochastic protocol.The activation probability of each sensor node is a given constant, whereas it is assumed that collisions occur with a certain probability.The resulting closed-loop system is a stochastic impulsive system withdelays in the continuous dynamics and in the reset equations. The system matrices have stochastic parameters with Bernoulli distributions.Sufficient conditions for the exponential mean-square stabilityare derived via a Lyapunov-Krasovskii-based method. The efficiency of the method is illustrated on the examples of a cart-pendulum system and a batch reactor.It is demonstrated how our time-delay approach allows treating network-induced delays larger thanthe sampling intervals.

    Fulltekst (pdf)
    KunIFAC2014
  • 346. Liu, Kun
    et al.
    Fridman, Emilia
    Johansson, Karl H.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Xia, Yuanqing
    Quantized Control Under Round-Robin Communication Protocol2016Inngår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 63, nr 7, s. 4461-4471Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper analyzes the exponential stability of a discrete-time linear plant in feedback control over a communication network with N sensor nodes, dynamic quantization, large communication delays, variable sampling intervals, and round-robin scheduling. The closedloop system is modeled as a switched system with multiple-ordered time-varying delays and bounded disturbances. We propose a time-triggered zooming algorithm implemented at the sensors that preserves exponential stability of the closed-loop system. A direct Lyapunov approach is presented for initialization of the zoom variable. The proposed framework can be applied to the plants with polytopic type uncertainties. The effectiveness of the method is illustrated on cart-pendulum and quadruple-tank processes.

  • 347.
    Liu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Beijing Institute of Technology, China.
    Fridman, Emilia
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dynamic quantization of uncertain linear networked control systems2015Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 59, s. 248-255Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is concerned with the stability analysis of networked control systems with dynamic quantization, variable sampling intervals and communication delays. A time-triggered zooming algorithm for the dynamic quantization at the sensor side is proposed that leads to an exponentially stable closed-loop system. The algorithm includes proper initialization of the zoom parameter. More precisely, given a bound on the state initial conditions and the values of the quantizer range and error, we derive conditions for finding the initial value of the zoom parameter, starting from which the exponential stability is guaranteed by using "zooming-in" only. Polytopic type uncertainties in the system model can be easily included in the analysis. The efficiency of the method is illustrated on an example of an uncertain cart-pendulum system.

  • 348.
    Liu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fridman, Emilia
    Tel Aviv University.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Networked control with stochastic scheduling2015Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, nr 99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper develops the time-delay approach to networked control systems with scheduling protocols, variable delays and variable sampling intervals. The scheduling of sensor communication is defined by a stochastic protocol. Two classes of protocols are considered. The first one is defined by an independent and identically-distributed stochastic process. The activation probability of each sensor node for this protocol is a given constant, whereas it is assumed that collisions occur with a certain probability. The resulting closed-loop system is a stochastic impulsive system with delays both in the continuous dynamics and in the reset equations, where the system matrices have stochastic parameters with Bernoulli distributions. The second scheduling protocol is defined by a discrete-time Markov chain with a known transition probability matrix taking into account collisions. The resulting closed-loop system is a Markovian jump impulsive system with delays both in the continuous dynamics and in the reset equations. Sufficient conditions for exponential mean-square stability of the resulting closed-loop system are derived via a Lyapunov-Krasovskii-based method. The efficiency of the method is illustrated on an example of a batch reactor. It is demonstrated how the time-delay approach allows treating network-induced delays larger than the sampling intervals in the presence of collisions.

    Fulltekst (pdf)
    fulltext
  • 349. Liuzza, D.
    et al.
    Dimarogonas, Dimos. V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Di Bernardo, M.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Distributed model based event-triggered control for synchronization of multi-agent systems2013Inngår i: IFAC Proceedings Volumes (IFAC-PapersOnline), 2013, nr PART 1, s. 329-334Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the problem of event-based control for the synchronization of networks of nonlinear dynamical agents. A distributed model based approach able to guarantee that all the agents converge to an adjustable synchronization region is derived. In such control scheme all the agents use a model of their neighborhood in order to generate triggering instants in which the local controller is updated and, if needed, local information is broadcasted to neighboring agents. The existence of a minimum lower bound between inter-event times is proven both for broadcasted information as well as for control signal updating, thus allowing implementation of the proposed strategy in applications where both the communication bandwidth and the maximum updating frequency of actuators are critical.

  • 350.
    Liuzza, Davide
    et al.
    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), Centra, ACCESS Linnaeus Centre.
    Distributed model based event-triggered control for synchronization of multi-agent systems2016Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 73, s. 1-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the problem of event-triggered control for the synchronization of networks of nonlinear dynamical agents; distributed model-based approaches able to guarantee the synchronization of the overall system are derived. In these control schemes all the agents use a model of their neighbourhood in order to generate triggering instants in which the local controller is updated and, if needed, local information based on the adopted control input is broadcasted to neighbouring agents, Synchronization of the network is proved and the existence of Zeno behaviour is excluded; an event triggered strategy able to guarantee the existence of a minimum lower bound between inter-event times for broadcasted information and for control signal updating is proposed, thus allowing applications where both the communication bandwidth and the maximum updating frequency of actuators are critical. This idea is further extended in an asynchronous periodic event-triggered schemes where the agents check a trigger condition via a periodic distributed communication without requiring a model based computation.

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