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  • 1.
    Abdalmoaty, Mohamed
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Henrion, D.
    Rodrigues, L.
    Measures and LMIs for optimal control of piecewise-affine systems2013In: 2013 European Control Conference, ECC 2013, IEEE, 2013, 3173-3178 p., 6669627Conference paper (Refereed)
    Abstract [en]

    This paper considers the class of deterministic continuous-time optimal control problems (OCPs) with piecewise-affine (PWA) vector field, polynomial Lagrangian and semialgebraic input and state constraints. The OCP is first relaxed as an infinite-dimensional linear program (LP) over a space of occupation measures. This LP is then approached by an asymptotically converging hierarchy of linear matrix inequality (LMI) relaxations. The relaxed dual of the original LP returns a polynomial approximation of the value function that solves the Hamilton-Jacobi-Bellman (HJB) equation of the OCP. Based on this polynomial approximation, a suboptimal policy is developed to construct a state feedback in a sample-and-hold manner. The results show that the suboptimal policy succeeds in providing a suboptimal state feedback law that drives the system relatively close to the optimal trajectories and respects the given constraints.

  • 2. Abu-Rmileh, Amjad
    et al.
    Garcia-Gabin, Winston
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Detection and Prevention of Hypoglycemia in Automated Insulin Delivery Systems for Type 1 Diabetes Patients2012In: Advances in Medicine and Biology / [ed] Leon V. Berhardt, Nova Science Publishers, Inc., 2012, 249-266 p.Chapter in book (Refereed)
  • 3. Abu-Rmileh, Amjad
    et al.
    Garcia-Gabin, Winston
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Hypoglycemia prevention in closed-loop artificial pancreas for patients with type 1 diabetes2011In: Diabetes: Damages and treatments / [ed] Everlon Cid Rigobelo, IN-TECH, 2011, 207-226 p.Chapter in book (Refereed)
  • 4.
    Abu-Rmileh, Amjad
    et al.
    Universidad de Gerona.
    Garcia-Gabin, Winston
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Smith Predictor Sliding Mode Closed-loop Glucose Controller in Type 1 Diabetes2011In: Proceedings of the 18th IFAC World Congress, 2011, 2011Conference paper (Refereed)
    Abstract [en]

    Type 1 diabetic patients depend on external insulin delivery to keep their blood glucose within near-normal ranges. In this work, two robust closed-loop controllers for blood glucose control are developed to prevent the life-threatening hypoglycemia, as well as to avoid extended hyperglycemia. The proposed controllers are designed by using the sliding mode control technique in a Smith predictor structure. To improve meal disturbance rejection, a simple feedforward controller is added to inject meal-time insulin bolus. Simulation studies were used to test the controllers, and shown the controllers ability to regulate the blood glucose within the safe limits in the presence of errors in measurements, modeling, and meal estimation.

  • 5. Abu-Rmileh, Amjad
    et al.
    Garcia-Gabin, Winston
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Wiener sliding-mode control for artificial pancreas: A new nonlinear approach to glucose regulation2012In: Computer Methods and Programs in Biomedicine, ISSN 0169-2607, E-ISSN 1872-7565, ISSN 0169-2607, Vol. 107, no 2, 327-340 p.Article in journal (Refereed)
    Abstract [en]

    Type 1 diabetic patients need insulin therapy to keep their blood glucose close to normal. In this paper an attempt is made to show how nonlinear control-oriented model may be used to improve the performance of closed-loop control of blood glucose in diabetic patients. The nonlinear Wiener model is used as a novel modeling approach to be applied to the glucose control problem. The identified Wiener model is used in the design of a robust nonlinear sliding mode control strategy. Two configurations of the nonlinear controller are tested and compared to a controller designed with a linear model. The controllers are designed in a Smith predictor structure to reduce the effect of system time delay. To improve the meal compensation features, the controllers are provided with a simple feedforward controller to inject an insulin bolus at meal time. Different simulation scenarios have been used to evaluate the proposed controllers. The obtained results show that the new approach out-performs the linear control scheme, and regulates the glucose level within safe limits in the presence of measurement and modeling errors, meal uncertainty and patient variations.

  • 6.
    Ackeberg, Anders
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Control of Periodic Solutions in Chemical Reactors2003Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 7.
    Adaldo, Antonio
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Liuzza, D.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Coordination of multi-agent systems with intermittent access to a cloud repository2017In: Workshop on Sensing and Control for Autonomous Vehicles: Applications to Land, Water and Air Vehicles, 2017, Springer, 2017, Vol. 474, 453-471 p.Conference paper (Refereed)
    Abstract [en]

    A cloud-supported multi-agent system is composed of autonomous agents required to achieve a common coordination objective by exchanging data over a shared cloud repository. The repository is accessed asychronously by different agents, and direct inter-agent commuication is not possible. This model is motivated by the problem of coordinating a fleet of autonomous underwater vehicles, with the aim to avoid the use of expensive and power-hungry modems for underwater communication. For the case of agents with integrator dynamics, a control law and a rule for scheduling the cloud access are formally defined and proven to achieve the desired coordination. A numerical simulation corroborate the theoretical results.

  • 8.
    Adaldo, Antonio
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Liuzza, Davide
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multi-Agent Trajectory Tracking with Self-Triggered Cloud Access2016In: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, 2207-2214 p., 7798591Conference paper (Refereed)
    Abstract [en]

    This paper presents a cloud-supported control algorithm for coordinated trajectory tracking of networked autonomous agents. The motivating application is the coordinated control of Autonomous Underwater Vehicles. The control objective is to have the vehicles track a reference trajectory while keeping an assigned formation. Rather than relying on inter-agent communication, which is interdicted underwater, coordination is achieved by letting the agents intermittently access a shared information repository hosted on a cloud. An event-based law is proposed to schedule the accesses of each agent to the cloud. We show that, with the proposed scheduling of the cloud accesses, the agents achieve the required coordination objective. Numerical simulations corroborate the theoretical results.

  • 9.
    Aglert, Johan
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Digital feedback control of the frequency response of a conventional loudspeaker2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Automatic control design and Hi-Fi loudspeakers are two areas that not very often are combined. In 1976 Karl Erik Ståhl performed a master thesis project at KTH where he, with analog circuits, made a positive feedback loop to manipulate the mechanical parameters of a loudspeaker. That project introduced the idea to use control design when constructing loudspeakers. In this project this idea is pursued.

    For a subwoofer, the interesting thing from a control perspective is that it is the low frequency range that has to be controlled as opposed to the high frequency range which is normally the case in disturbance and servo problems. This master thesis project will present a solution to this problem where a digital signal processor is used to handle the feed back information. The IMC controller implemented in the processor is based on models derived from data, measured in the tailor made laboratory set-up that was built for the project. In order to satisfy the sampling rate requirements, the complexity of the control algorithm had to be restricted. Despite this limitation in the equipment, the frequency response of the loudspeaker was improved significantly at low frequencies.

  • 10.
    Agüero, Juan C.
    et al.
    The University of Newcastle, Australia.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Goodwin, Graham C.
    The University of Newcastle, Australia.
    Fundamental Limitations on the Accuracy of MIMO Linear Models Obtained by PEM for Systems Operating in Open Loop2009In: Proceedings of the Joint 48th IEEE Conference on Decision and Control (CDC’09) and 28th Chinese Control Conference (CCC’09), 2009, 482-487 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we show that the variance of estimated parametric models for open loopMultiple-Input Multiple-Output (MIMO) systems obtained by the prediction error method (PEM) satisfies a fundamental integral limitation. The fundamental limitation gives rise to a multivariable 'water-bed' effect.

  • 11.
    Agüero, Juan C.
    et al.
    The University of Newcastle, Australia.
    Rojas, Cristian R.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Goodwin, Graham C.
    The University of Newcastle, Australia.
    Accuracy of linear multiple-input multiple-output (MIMO) models obtained by maximum likelihood estimation2012In: Automatica, ISSN 0005-1098, Vol. 48, no 4, 632-637 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the accuracy of linear multiple-input multiple-output (MIMO) models obtained by maximum likelihood estimation. We present a frequency-domain representation for the information matrix for general linear MIMO models. We show that the variance of estimated parametric models for linear MIMO systems satisfies a fundamental integral trade-off. This trade-off is expressed as a multivariable 'water-bed' effect. An extension to spectral estimation is also discussed.

  • 12.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kennedy, M. W.
    Fritzsch, R.
    Aune, R. E.
    An investigation on permeability of ceramic foam filters (CFF)2015In: TMS Light Metals, 2015, 949-954 p.Conference paper (Refereed)
    Abstract [en]

    CFFs are used to filter liquid metal in the aluminum industry. CFFs are classified in grades or pores per inch (PPI), ranging from 10-100 PPI. Their properties vary in everything from pore and strut size to window size. CFFs of 80-100 PPI are generally not practical for use by industry, as priming of the filters by gravitational forces requires an excessive metal head. Recently, co-authors have invented a method to prime such filters using electromagnetic Lorentz forces, thus allowing filters to be primed with a low metal head. In the continuation of this research work, an improved experimental setup was developed in the present study to validate previous results and to measure the permeability of different filters, as well as a stack of filters. The study of permeability facilitates estimation of the required pressure drop to prime the filters and the head required to generate a given casting rate.

  • 13. Akcay, H.
    et al.
    Hjalmarsson, Håkan
    Department of Electrical Engineering, Linköping University.
    Ljung, Lennart
    Department of Electrical Engineering, Linköping University.
    On the choice of norms in system identification1996In: IEEE Transactions on Automatic Control, ISSN 00189286 (ISSN), Vol. 41, no 9, 1367-1372 p.Article in journal (Refereed)
    Abstract [en]

    In this paper we discuss smooth and sensitive norms for prediction error system identification when the disturbances are magnitude bounded. Formal conditions for sensitive norms, which give an order of magnitude faster convergence of the parameter estimate variance, are developed. However, it also is shown that the parameter estimate variance convergence rate of sensitive norms is arbitrarily bad for certain distributions. A necessary condition for a norm to be statistically robust with respect to the family F(C) of distributions with support [-C, C] for some arbitrary C > 0 is that its second derivative does not vanish on the support. A direct consequence of this observation is that the quadratic norm is statistically robust among all ℓp-norms, p ≀ 2 < ∞ for F(C). ©1996 IEEE.

  • 14.
    Akçay, H.
    et al.
    Linköping University.
    Hjalmarsson, Håkan
    Linköping University.
    The least-squares identification of FIR systems subject to worst-case noise1994In: System & Control Letters, Vol. 23, 329-338 p.Article in journal (Refereed)
  • 15.
    Akçay, H.
    et al.
    Linköping University.
    Hjalmarsson, Håkan
    Linköping University.
    The Least-Squares Identification of FIR Systems Subject to Worst-Case Noise1994In: 10th IFAC Symposium on System Identification, 1994, Vol. 2, 85-90 p.Conference paper (Refereed)
  • 16.
    Akçay, H.
    et al.
    Linköping University.
    Hjalmarsson, Håkan
    Linköping University.
    Ljung, Lennart
    Department of Electrical Engineering, Linköping University.
    On the choice of norms i system identification1994In: 10th IFAC Symposium on System Identification, 1994, Vol. 2, 103-108 p.Conference paper (Refereed)
  • 17.
    Al Alam, Assad
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimally Fuel Ecient Speed Adaptation2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An optimal velocity trajectory for a heavy duty vehicle, obtained with the aid of modern GPS and digital map devices, depends on several variables. Curvature speed limitations, road grade, and posted road speed are common constraints imposed by the road travelled. This thesis presents a method for modelling and analysing a switching controller through the use of the former mentioned constraints. A non-linear model for the heavy duty vehicle is derived, enabling suitable control methods to be applied. Pontryagin’s Principal and LQR are discussed to get a profound understanding of how the controller should be designed. It is discovered that a switching controller based on optimal control and engineering experience is most favourable for the problem at hand. The controller is designed to address the main objectives set in this paper of minimising fuel consumption, travelling time, and brake wear.

    Gauss-Newtons’s algorithm for non-linear equations is used to estimate curve radii. Other input parameters are presumed to be available. GPS data error is discussed to perform a sensitivity analysis. An electronic horizon is produced on three road segments, entailed with data of the future road topology. Finally the switching controller is applied to the road segments. Experimental results show that the controller produces a velocity trajectory, which reduces fuel consumption by 5-15% and brake wear by 15-35%, while the travelling time is only increased by 1-2%.

  • 18.
    Al Alam, Assad
    et al.
    Scania CV AB.
    Gattami, Ather
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    An experimental study on the fuel reduction potential of heavy duty vehicle platooning2010In: 13th International IEEE Conference on Intelligent Transportation Systems (ITSC), 2010, IEEE , 2010, 306-311 p.Conference paper (Refereed)
    Abstract [en]

    Vehicle platooning has become important for the vehicle industry. Yet conclusive results with respect to the fuel reduction possibilities of platooning remain unclear. The focus in this study is the fuel reduction that heavy duty vehicle platooning enables and the analysis with respect to the influence of a commercial adaptive cruise control on the fuel consumption. Experimental results show that by using preview information of the road ahead from the lead vehicle, the adaptive cruise controller can reduce the fuel consumption. A study is undertaken for various masses of the lead vehicle. The results show that the best choice with respect to a heavier or lighter lead vehicle depends on the desired time gap. A maximum fuel reduction of 4.7-7.7% depending on the time gap, at a set speed of 70 km/h, can be obtained with two identical trucks. If the lead vehicle is 10 t lighter a corresponding 3.8-7.4% fuel reduction can be obtained depending on the time gap. Similarly if the lead vehicle is 10 t heavier a 4.3-6.9% fuel reduction can be obtained. All results indicate that a maximum fuel reduction can be achieved at a short relative distance, due to both air drag reduction and suitable control.

  • 19.
    Al Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Gattami, Ather
    Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley CA, 94720-1770, United States .
    Johansson, Karl Henrik
    Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley CA, 94720-1770, United States .
    Tomlin, Claire Jennifer
    Scania CV AB, Södertälje, Sweden.
    Establishing safety for heavy duty vehicle platooning: a game theoretical approach2011In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2011, 3818-3823 p.Conference paper (Refereed)
    Abstract [en]

    It is fuel efficient to minimize the relative distance between vehicles to achievea maximum reduction in air drag. However, the relative distance can only be reduced to acertain extent without endangering a collision. Factors such as the vehicle velocity, the relativevelocity, and the characteristics of the vehicle ahead has a strong impact on what minimumrelative distance can be obtained. In this paper, we utilize optimal control and game theory toestablish safety criteria for heavy duty vehicle platooning applications. The derived results showthat a minimum relative distance of 1.2m can be obtained for two identical vehicles withoutendangering a collision, assuming that there is no delay present in the feedback system. If aworst case delay is present in the system, a minimum relative distance is deduced based uponthe vehicle’s maximum deceleration ability. The relative distance can be reduced if the followervehicle has a greater overall braking capability, which suggests that vehicle heterogeneity andorder has substantial impact. The findings are verified by simulations and the main conclusion isthat the relative distance utilized in commercial applications today can be reduced significantlywith a suitable advanced cruise control system.

  • 20.
    Alam, Assad
    KTH, School of Electrical Engineering (EES).
    Fuel-Efficient Distributed Control for Heavy Duty Vehicle Platooning2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Freight transport demand has escalated and will continue to do so as economiesgrow. As the traffic intensity increases, the drivers are faced with increasinglycomplex tasks and traffic safety is a growing issue. Simultaneously, fossil fuel usageis escalating. Heavy duty vehicle (HDV) platooning is a plausible solution to theseissues. Even though there has been a need for introducing automated HDV platooningsystems for several years, they have only recently become possible to implement.Advancements in on-board and external technology have ushered in new possibilitiesto aid the driver and enhance the system performance. Each vehicle is able to serveas an information node through wireless communication; enabling a cooperativenetworked transportation system. Thereby, vehicles can semi-autonomously travel atshort intermediate spacings, effectively reducing congestion, relieving driver tension,improving fuel consumption and emissions without compromising safety.

    This thesis presents contributions to a framework for the design and implementation of HDV platooning. The focus lies mainly on establishing and validating realconstraints for fuel optimal control for platooning vehicles. Nonlinear and linearvehicle models are presented together with a system architecture, which dividesthe complex problem into manageable subsystems. The fuel reduction potentialis investigated through simulation models and experimental results derived fromstandard vehicles traveling on a Swedish highway. It is shown through analyticaland experimental results that it is favorable with respect to the fuel consumption tooperate the vehicles at a much shorter intermediate spacing than what is currentlydone in commercially available systems. The results show that a maximum fuelreduction of 4.7–7.7 % depending on the inter-vehicle time gap, at a set speedof 70 km/h, can be obtained without compromising safety. A systematic designmethodology for inter-vehicle distance control is presented based on linear quadraticregulators (LQRs). The structure of the controller feedback matrix can be tailoredto the locally available state information. The results show that a decentralizedcontroller gives good tracking performance, a robust system and lowers the controleffort downstream in the platoon. It is also shown that the design methodologyproduces a string stable system for an arbitrary number of vehicles in the platoon,if the vehicle configurations and the LQR weighting parameters are identical for theconsidered subsystems.

    With the results obtained in this thesis, it is argued that a vast fuel reductionpotential exists for HDV platooning. Present commercial systems can be enhancedsignificantly through the introduction of wireless communication and decentralizedoptimal control.

  • 21.
    Alam, Assad
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fuel-Efficient Heavy-Duty Vehicle Platooning2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The freight transport industry faces big challenges as the demand for transport and fuel prices are steadily increasing, whereas the environmental impact needs to be significantly reduced. Heavy-duty vehicle (HDV) platooning is a promising technology for a sustainable transportation system. By semi-autonomously governing each platooning vehicle at small inter-vehicle spacing, we can effectively reduce fuel consumption, emissions, and congestion, and relieve driver tension. Yet, it is not evident how to synthesise such a platoon control system and how constraints imposed by the road topography affect the safety or fuel-saving potential in practice.

    This thesis presents contributions to a framework for the design, implementation, and evaluation of HDV platooning. The focus lies mainly on establishing fuel-efficient platooning control and evaluating the fuel-saving potential in practice. A vehicle platoon model is developed together with a system architecture that divides the control problem into manageable subsystems. Presented results show that a significant fuel reduction potential exists for HDV platooning and it is favorable to operate the vehicles at a small inter-vehicle spacing. We address the problem of finding the minimum distance between HDVs in a platoon without compromising safety, by setting up the problem in a game theoretical framework. Thereby, we determine criteria for which collisions can be avoided in a worst-case scenario and establish the minimum safe distance to a vehicle ahead. A systematic design methodology for decentralized inter-vehicle distance control based on linear quadratic regulators is presented. It takes dynamic coupling and engine response delays into consideration, and the structure of the controller feedback matrix can be tailored to the locally available state information. The results show that a decentralized controller gives good tracking performance and attenuates disturbances downstream in the platoon for dynamic scenarios that commonly occur on highways. We also consider the problem of finding a fuel-efficient controller for HDV platooning based on road grade preview information under road and vehicle parameter uncertainties. We present two model predictive control policies and derive their fuel-saving potential. The thesis finally evaluates the fuel savings in practice. Experimental results show that a fuel reduction of 3.9–6.5 % can be obtained on average for a heterogenous platoon of HDVs on a Swedish highway. It is demonstrated how the savings depend on the vehicle position in the platoon, the behavior of the preceding vehicles, and the road topography. With the results obtained in this thesis, it is argued that a significant fuel reduction potential exists for HDV platooning.

  • 22.
    Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Asplund, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Behere, Sagar
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Björk, Mattias
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Garcia Alonso, Liliana
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Khaksari, Farzad
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Khan, Altamash
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Kjellberg, Joakim
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Liang, Kuo-Yun
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lyberger, Rickard
    Scania CV AB.
    Mårtensson, Jonas
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Pettersson, Henrik
    Scania CV AB.
    Pettersson, Simon
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Stålklinga, Elin
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sundman, Dennis
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Cooperative driving according to Scoop2011Report (Other academic)
    Abstract [en]

    KTH Royal Institute of Technology and Scania are entering the GCDC 2011 under the name Scoop –Stockholm Cooperative Driving. This paper is an introduction to their team and to the technical approach theyare using in their prototype system for GCDC 2011.

  • 23.
    Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Scania CV AB, SE-15187 Södertälje, Sweden.
    Gattami, Ather
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tomlin, Claire J.
    UC Berkeley.
    Guaranteeing safety for heavy duty vehicle platooning: Safe set computations and experimental evaluations2014In: Control Engineering Practice, ISSN 0967-0661, Vol. 24, no 1, 33-41 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider the problem of finding a safety criteria between neighboring heavy duty vehicles traveling in a platoon. We present a possible framework for analyzing safety aspects of heavy duty vehicle platooning. A nonlinear underlying dynamical model is utilized, where the states of two neighboring vehicles are conveyed through radar information and wireless communication. Numerical safe sets are derived through the framework, under a worst-case scenario, and the minimum safe spacing is studied for heterogenous platoons. Real life experimental results are presented in an attempt to validate the theoretical results in practice. The findings show that a minimum relative distance of 1.2 m at maximum legal velocity on Swedish highways can be maintained for two identical vehicles without endangering a collision. The main conclusion is that the relative distance utilized in commercial applications today can be reduced significantly with a suitable automatic control system.

  • 24. Alam, Assad
    et al.
    Gattami, Ather
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Suboptimal Decentralized Controller Design for Chain Structures: Applications to Vehicle Formations2011In: IEEE 50th Annual Conference on Decision and Control and European Control Conference, Orlando, December, 2011, IEEE , 2011, 6894-6900 p.Conference paper (Refereed)
    Abstract [en]

    We consider suboptimal decentralized controllerdesign for subsystems with interconnected dynamics and costfunctions. A systematic design methodology is presented overthe class of linear quadratic regulators (LQR) for chain graphs.The methodology is evaluated on heavy duty vehicle platooningwith physical constraints. A simulation and frequency analysisis performed. The results show that the decentralized controllergives good tracking performance and a robust system. We alsoshow that the design methodology produces a string stablesystem for an arbitrary number of vehicles in the platoon, ifthe vehicle configurations and the LQR weighting parametersare identical for the considered subsystems.

  • 25.
    Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Mårtensson, Jonas
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Look-Ahead Cruise Control for Heavy Duty Vehicle Platooning2013In: Proceedings of the 16th International IEEE Annual Conference onIntelligent Transportation Systems (ITSC 2013), IEEE conference proceedings, 2013, 928-935 p.Conference paper (Refereed)
    Abstract [en]

    Vehicle platooning has become important for thevehicle industry. Yet conclusive results with respect to thefuel reduction possibilities of platooning remain unclear, inparticular when considering constraints imposed by the topography.The focus of this study is to establish whether itis more fuel-efficient to maintain or to split a platoon that isfacing steep uphill and downhill segments. Two commercialcontrollers, an adaptive cruise controller and a look-aheadcruise controller, are evaluated and alternative novel controlstrategies are proposed. The results show that an improvedfuel-efficiency can be obtained by maintaining the platoonthroughout a hill. Hence, a cooperative control strategy basedon preview information is presented, which initiates the changein velocity at a specific point in the road for all vehiclesrather than simultaneously changing the velocity to maintainthe spacing. A fuel reduction of up to 14% can be obtainedover a steep downhill segment and a more subtle benefit of0.7% improvement over an uphill segment with the proposedcontroller, compared to the combination of the commerciallyavailable cruise controller and adaptive cruise controller thatcould be used for platooning. The findings show that it isboth fuel-efficient and desirable in practice to consider previewinformation of the topography in the control strategy.

  • 26.
    Alam, Assad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sahlholm, Per
    KTH, School of Electrical Engineering (EES), Automatic Control.
    A Method for Determining an Economical Speed for Heavy Vehicles2008In: Proceedings of the 15th World Congress on Intelligent Transport Systems, World Congress on Intelligent Transport Systems (ITS), 2008Conference paper (Refereed)
  • 27.
    Alberer, Daniel
    et al.
    Johannes Kepler University.
    Hjalmarsson, HåkanKTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.del Re, LuigiJohannes Kepler University.
    Identification for Automotive Systems2012Collection (editor) (Refereed)
  • 28.
    Alberer, Daniel
    et al.
    Johannes Kepler University.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    del Re, Luigi
    Johannes Kepler University.
    System Identification for Automotive Systems: Opportunities and Challenges2012In: Identification for Automotive Systems / [ed] Daniel Alberer, Håkan Hjalmarsson, Luigi del Re, Springer London, 2012, 1-10 p.Chapter in book (Refereed)
    Abstract [en]

    Without control many essential targets of the automotive industry could not be achieved. As control relies directly or indirectly on models and model quality directly influences the control performance, especially in feedforward structures as widely used in the automotive world, good models are needed. Good first principle models would be the first choice, and their determination is frequently difficult or even impossible. Against this background methods and tools developed by the system identification community could be used to obtain fast and reliably models, but a large gap seems to exist: neither these methods are sufficiently well known in the automotive community, nor enough attention is paid by the system identification community to the needs of the automotive industry. This introduction summarizes the state of the art and highlights possible critical issues for a future cooperation as they arose from an ACCM Workshop on Identification for Automotive Systems recently held in Linz, Austria.

  • 29. Alexandre, Seuret
    et al.
    Dimarogonas, Dimos V.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Automatic Control.
    Consensus of Double Integrator Multi-agents under Communication Delay2009In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2009, 376-381 p.Conference paper (Refereed)
    Abstract [en]

    This paper deals with the consensus problem under network induced communication delays. It is well-known that introducing a delay generally leads to a reduce of the performance or to instability. Thus, investigating the impact of time-delays in the consensus problem is an important issue. Another important issue is to obtain an estimate of the convergence rate, which is not straightforward when delays appear in the network. In this paper, the agents are modelled as double integrator systems. It is assumed that each agent receives instantaneously its own output information but receives the information from its neighbors after a constant delay. A stability criterion is provided based on Lyapunov-Krasovskii techniques and is expressed in terms of LMI. An expression of the consensus equilibrium which depends on the delay and on the initial conditions taken in an interval is derived. The results are supported through several simulations for different network symmetric communication schemes.

  • 30.
    Almeida, Diogo
    KTH, School of Electrical Engineering (EES). KTH.
    Event-Triggered Attitude Stabilization of a Quadcopter2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are many possible ways to perform the attitude control of a quadcopter and, recently, the subject of event-triggered control has become relevant in the scientic community. This thesis deals with the analysis and implementation of a saturating attitude controller for a quadcopter system, together with the derivation of an event-triggering rule to work with it. Two distinct rules are presented, one that ensures the stability of the closed loop system, the other, a linearised version that does not. The way those were derived consists in the use of a Lyapunov based approach. The stability of the system when under these rules was veried experimentally.

  • 31. Almstrom, Peter
    et al.
    Rabi, Maben
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Networked state estimation over a Gilbert-Elliot type channel2009In: Proceedings of the IEEE Conference on Decision and Control, 2009, 2711-2716 p.Conference paper (Refereed)
    Abstract [en]

    We characterize the stability and achievable performance of networked estimation under correlated packet losses described by the Gilbert-Elliot model. For scalar continuous-time linear systems, we derive closed-form expressions for the mean-square distortion of the optimal estimator. The conditions for stable mean square estimation error are equivalent to those obtained previously for stability of 'peak distortions' [3]. We study how the estimator performance depends on loss probability and loss burst length, and show that the mean-square distortion remains bounded if the average burst length does not exceeda calculated bound. The main new finding is that, once we fix the mean length of loss bursts, the average packet loss rate influences the estimator's performance but not its stability. 

  • 32.
    Almér, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Fujioka, Hisaya
    KTH. Kyoto University, Japan.
    Jönsson, Ulf
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Kao, Chung Yao
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Patino, D.
    Riedinger, P.
    Geyer, T.
    Beccuti, A.
    Papafotiou, G.
    Morari, M.
    Wernrud, A.
    Rantzer, A.
    Hybrid control techniques for switched-mode DC-DC converters part I: The step-down topology2007In: 2007 American Control Conference, IEEE , 2007, 5450-5457 p.Conference paper (Refereed)
    Abstract [en]

    Several recent techniques from hybrid and optimal control are evaluated on a power electronics benchmark problem. The benchmark involves a number of practically interesting operating scenarios for a fixed-frequency synchronous step-down dc-dc converter. The specifications are defined such that good performance only can be obtained if the switched and nonlinear nature of the problem is respected during the design phase.

  • 33.
    Almér, Stefan
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Jönsson, Ulf T.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Dynamic phasor analysis of a class of PWM systems2015In: 2007 European Control Conference, ECC 2007, 2015, 1940-1947 p.Conference paper (Refereed)
    Abstract [en]

    The paper makes use of the so-called dynamic phasor model for stability and performance analysis of a class of PWM systems. The dynamic phasor model allows for the state to be represented in the frequency domain where a harmonic Lyapunov function is defined. The analysis covers both periodically switched systems and non-periodic systems where the switching is controlled by feedback.

  • 34.
    Altaf, Faisal
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Modeling and Event-Triggered Control ofMultiple 3D Tower Cranes over WSNs2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless control of 3D tower cranes is a topic of great industrial significance as it offers greater flexibility and lower maintenance cost. But the reduction in shared network resource utilization and the desired level of control performance against packet losses and delays are main concerns.

    Our first aim is to develop a mathematical model of the 3D tower crane for the control design purpose. The second aim is to design a model-based eventtriggered controller for wireless control of multiple 3D tower cranes to asymptotically track step reference inputs. The controller and cranes are connected in a star topology over simulated wireless sensor network with IEEE 802.15.4 MAC protocol for channel access. The third aim is to numerically evaluate and compare the performance of the event-triggered controller with that of a periodic controller under network induced delays, packet dropouts and with respect to scalability and the effect of MAC protocol on the stability.

    The dynamic model for the 3D tower crane has been identified through physical modeling followed by lumped parametric estimation. The proposed event-triggered control policy for tracking problem uses the integral control structure for which theoretical results have been derived using Lyapunov input-to-state stability theorem.

    Under nominal network settings, the event-triggered controller reduces the network resource utilization by 4 times but achieves almost the same control performance as compared to periodic controller executions. The network cost under event-triggered control policy not only depends on the point network induced delay enters into the system, but also increases almost monotonically with it. The event-triggered control policy utilizes the lower communication cost as compared to periodic case only up to certain amount of delay in a loop and hence must only be preferred over periodic case after considering the level and location of delay in the system. Under these conditions, up to 13 crane tasks are schedulable over network under event-triggered control policy using CSMA/CA random access. All the simulations have been done in MATLAB® Simulink using TrueTime toolbox.

  • 35.
    Altaf, Faisal
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Araujo, José
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hernandez, Aitor
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wireless event-triggered controller for a 3D tower crane lab process2011In: 2011 19th Mediterranean Conference on Control and Automation, MED 2011, 2011, 994-1001 p.Conference paper (Refereed)
    Abstract [en]

    This paper studies the design and real-time implementation of an event-triggered controller for a nonlinear 3D tower crane where the communication between the controller and the actuators is performed over a low-power wireless network. A flexible Event-Generation Circuit (EGC) is proposed in order to implement event-driven controllers for Networked Control Systems. Furthermore, a detailed experimental analysis on the performance of the event-triggered controller and the influence of packet losses on the transmitted actuation messages are presented. The results show that the event-triggered controllers in networked control systems are able to maintain the same level of performance as compared to periodic controllers, while increasing the sensors/actuators lifetime by reducing network bandwidth utilization.

  • 36.
    Altafini, Claudio
    et al.
    SISSA-ISAS International School for Advanced Studies.
    Speranzon, Alberto
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl Henrik
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hybrid control of a truck and trailer vehicle2002In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 2289, 21-34 p.Article in journal (Other academic)
    Abstract [en]

    A hybrid control scheme is proposed for the stabilization of backward driving along simple paths for a miniature vehicle composed of a truck and a two-axle trailer. When reversing, the truck and trailer can be modelled as an unstable nonlinear system with state and input saturations. Due to these constraints the system is impossible to globally stabilize with standard smooth control techniques, since some initial states necessarily lead to that the so called jack-knife locks between the truck and the trailer. The proposed hybrid control method, which combines backward and forward motions, provide a global attractor to the desired reference trajectory. The scheme has been implemented and successfully evaluated on a radio-controlled vehicle. Results from experimental trials are reported.

  • 37.
    Altafini, Claudio
    et al.
    KTH, Superseded Departments, Mathematics.
    Speranzon, Alberto
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Wahlberg, Bo
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A feedback control scheme for reversing a truck and trailer vehicle2001In: IEEE transactions on robotics and automation, ISSN 1042-296X, Vol. 17, no 6, 915-922 p.Article in journal (Refereed)
    Abstract [en]

    A control scheme is proposed for stabilization of backward driving along simple paths for a miniaturized vehicle composed of a truck and a two-axle trailer. The paths chosen are straight lines and arcs of circles. When reversing, the truck and trailer under examination can be modeled as an unstable nonlinear system with state and input saturations. The simplified goal of stabilizing along a trajectory (instead of a point) allows us to consider a system with controllable linearization. Still, the combination of instability and saturations makes the task impossible with a single controller. In fact, the system cannot be driven backward from all initial states because of the jack-knife effects between the parts of the multibody vehicle; it is sometimes necessary to drive forward to enter into a specific region of attraction. This leads to the use of hybrid controllers. The scheme has been implemented and successfully used to reverse the radio-controlled vehicle.

  • 38. Alur, R.
    et al.
    D'Innocenzo, A.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pappas, G. J.
    Weiss, G.
    Modeling and analysis of multi-hop control networks: RTAS 2009, Proceedings2009In: 15TH IEEE REAL-TIME AND EMBEDDED TECHNOLOGY AND APPLICATION SYMPOSIUM: RTAS 2009, Proceedings, IEEE Computer Society, 2009, 223-232 p.Conference paper (Refereed)
    Abstract [en]

    We propose a mathematical framework, inspired by the WirelessHART specification, for modeling and analysing multi-hop communication networks. The framework is designed for systems consisting of multiple control loops closed over a multi-hop communication network. We separate control, topology, routing, and scheduling and propose formal syntax and semantics for the dynamics of the composed system. The main technical contribution of the paper is an explicit translation of multi-hop control networks to switched systems. We describe a Mathematica notebook that automates the translation of multihop control networks to switched systems, and use this tool to show how techniques for analysis of switched systems can be used to address control and networking co-design challenges.

  • 39. Alur, Rajeev
    et al.
    D'Innocenzo, Alessandro
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pappas, George J.
    Weiss, Gera
    Compositional Modeling and Analysis of Multi-Hop Control Networks2011In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, no 10, 2345-2357 p.Article in journal (Refereed)
    Abstract [en]

    We propose a mathematical framework for modeling and analyzing multi-hop control networks designed for systems consisting of multiple control loops closed over a multi-hop (wireless) communication network. We separate control, topology, routing, and scheduling and propose formal syntax and semantics for the dynamics of the composed system, providing an explicit translation of multi-hop control networks to switched systems. We propose formal models for analyzing robustness of multi-hop control networks, where data is exchanged through a multi-hop communication network subject to disruptions. When communication disruptions are long, compared to the speed of the control system, we propose to model them as permanent link failures. We show that the complexity of analyzing such failures is NP-hard, and discuss a way to overcome this limitation for practical cases using compositional analysis. For typical packet transmission errors, we propose a transient error model where links fail for one time slot independently of the past and of other links. We provide sufficient conditions for almost sure stability in presence of transient link failures, and give efficient decision procedures. We deal with errors that have random time span and show that, under some conditions, the permanent failure model can be used as a reliable abstraction. Our approach is compositional, namely it addresses the problem of designing scalable scheduling and routing policies for multiple control loops closed on the same multi-hop control network. We describe how the translation of multi-hop control networks to switched systems can be automated, and use it to solve control and networking co-design challenges in some representative examples, and to propose a scheduling solution in a mineral floatation control problem that can be implemented on a time triggered communication protocols for wireless networks.

  • 40.
    Alvehag, Karin
    et al.
    KTH, School of Electrical Engineering (EES).
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    A stochastic approach for modeling residential interruption costs2008In: 16th Power Systems Computation Conference, PSCC 2008, Power Systems Computation Conference (PSCC) , 2008Conference paper (Refereed)
    Abstract [en]

    In power system planning and operation, accurate assessment of reliability worth is essential for making informed decisions. The accuracy of the reliability worth estimation is directly affected by the interruption cost model used in the analysis. Residential interruption costs vary with season, day of week and time of day, and can be difficult to handle because of their intangible characteristics. This paper develops a cost model for residential customers that includes the timing of the outage by modeling the underlying factors that give rise to the temporal variations in residential interruption costs. By considering the stochastic nature of the underlying factors, as for example outdoor temperature, the proposed model makes it possible to estimate the costs for an event that is extreme in other senses than having a long duration. Time sequential Monte Carlo simulations were applied to a test system in order to assess reliability worth. The results show that the commonly used customer damage function overestimates the reliability worth. By accounting for the timing of the outages a more realistic estimation of the interruption costs can be obtained.

  • 41.
    Aminian, Behdad
    KTH, School of Electrical Engineering (EES), Automatic Control.
    GISOO: A Virtual Testbed for Wireless Networked Control Systems2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Networked control over wireless sensor and actuator networks is of growing importance in cyber-physical systems as in industrial process control and building management systems. The correct design of wireless communication solutions and control algorithms is therefore a major requirement in such systems. Simulators and emulators of wireless networked control systems (WNCSs) are tools that help the system designer to develop, optimize and validate solutions prior to the deployment in a real system. Without such tools the development and validation of complex systems would be highly costly, both financially and timely.

    Considering the special characteristic of WNCSs, which is a complex combination of control systems and a wireless network, WNCSs’ simulators must be able to model and emulate/simulate both the control systems and wireless systems together.

    In this thesis project, GISOO, a new simulation platform for WNCSs has been created. GISOO stands for Graphical Integration of Simulink and Cooja and is a hybrid simulation environment which simulates both the physical system to be controlled and the wireless devices and their networking behavior. Simulink, developed by Mathworks, is a tool for modeling, simulation and analysis of dynamic systems and is widely used by the control engineers. The Cooja network simulator, is able to emulate the operation of a real wireless device and its networking behavior. In this way, developers can set up simulations both to debug the developed software and the behavior of the system before running it in the target hardware. This specification makes GISOO a powerful virtual testbed for developing and evaluating novel communication protocols, control techniques and their interactions in large scale complex systems. We validate the correct operation of GISOO in the closed-loop control of a double tank system.

  • 42.
    Aminian, Behdad
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Araújo, José
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    GISOO: A virtual testbed for wireless cyber-physical systems2013In: Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE, IEEE , 2013, 5588-5593 p.Conference paper (Refereed)
    Abstract [en]

    The increasing demand for wireless cyber-physical systems requires correct design, implementation and validation of computation, communication and control methods. Traditional simulation tools, which focus on either computation, communication or control, are insufficient when the three aspects interact. Efforts to extend the traditional tools to cover multiple domains, e.g., from simulating only control aspects to simulating both control and communication, often rely on simplistic models of a small subset of possible communication solutions. We introduce GISOO, a virtual testbed for simulation of wireless cyber-physical systems that integrates two state-of-the art simulators, Simulink and COOJA. GISOO enables users to evaluate actual embedded code for the wireless nodes in realistic cyber-physical experiments, observing the effects of both the control and communication components. In this way, a wide range of communication solutions can be evaluated without developing abstract models of their control-relevant aspects, and changes made to the networking code in simulations is guaranteed to be translated into production code without errors. A double-tank laboratory experimental setup controlled over a multi-hop relay wireless network is used to validate GISOO and demonstrate its features.

  • 43.
    Anderson, James
    et al.
    Oxford University.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Papachristodoulou, Antonis
    Oxford University.
    Dynamical System Decomposition Using Dissipation Inequalities2011In: Proceedings of the 50th IEEE Conference on Decision and Control and European Control Conference,  Orlando, Florida, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper we investigate stability and inter-action measures for interconnected systems that have beenproduced by decomposing a large-scale linear system into aset of lower order subsystems connected in feedback. We beginby analyzing the requirements for asymptotic stability throughgeneralized dissipation inequalities and storage functions. Usingthis insight we then describe various metrics based on a system’senergy dissipation to determine how strongly the subsystemsinteract with each other. From these metrics a decompositionalgorithm is described.

  • 44. Anderson, R. P.
    et al.
    Milutinovic, D.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Self-triggered stabilization of continuous stochastic state-feedback controlled systems2013In: 2013 European Control Conference, ECC 2013, 2013, 1151-1155 p.Conference paper (Refereed)
    Abstract [en]

    Event-triggered and self-triggered control, in which the time of update to the controls is based on either current or outdated sampled data, have recently been employed to reduce the computational load or resource consumption for distributed real-time control systems. In this work, we propose a self-triggered scheme for nonlinear controlled stochastic differential equations with additive noise terms. A self-triggering update condition is derived that guarantees stability in the p-th moment of the state distribution. We show that the length of the times between controller updates as computed from the proposed scheme is strictly positive and provide examples.

  • 45. Anderson, R. P.
    et al.
    Milutinović, D.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Self-triggered sampling for second-moment stability of state-feedback controlled SDE systems2015In: Automatica, ISSN 0005-1098, Vol. 54, 8-15 p.Article in journal (Refereed)
    Abstract [en]

    Event-triggered and self-triggered control, whereby the times for controller updates are computed from sampled data, have recently been shown to reduce the computational load or increase task periods for real-time embedded control systems. In this work, we propose a self-triggered scheme for nonlinear controlled stochastic differential equations with additive noise terms. We find that the family of trajectories generated by these processes demands a departure from the standard deterministic approach to event- and self-triggering, and, for that reason, we use the statistics of the sampled-data system to derive a self-triggering update condition that guarantees second-moment stability. We show that the length of the times between controller updates as computed from the proposed scheme is strictly positive and provide related examples.

  • 46.
    Anderson, Sören
    et al.
    Department of Electrical Engineering, Linköping University.
    Millnert, Mille
    Department of Electrical Engineering, Linköping University.
    Viberg, Mats
    Department of Electrical Engineering, Linköping University.
    Wahlberg, Bo
    Department of Electrical Engineering, Linköping University.
    An adaptive array for mobile communication systems1991In: IEEE Transactions on Vehicular Technology, ISSN 00189545 (ISSN), Vol. 40, no 1 pt 2, 230-236 p.Article in journal (Refereed)
    Abstract [en]

    The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting modes. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

  • 47.
    Andersson, Joel
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Minimering av förväntad reparationskostnad, I2007Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 48.
    Andersson, Marika
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Investigation of dynamic information in reactor noise measurements2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this master´s thesis is to investigate if it is possible to extract more dynamic information out of physical signals from nuclear reactor noise measurements than what is possible today. This was achieved by investigating methods to examine and determine the process signal quality, and studying the corresponding transfer function. Accurate measurements of for example the core stability and the control system interference are required for detailed process diagnostics.

    By analysing real reactor signals, (here neutron flux and reactor pressure), it is observed that they are correlated. Becuase the structure of the real system is not perfectly known, two hypothesis have been made regarding the real system. Identification of the transfer function of the two simulated systems have been done using Matlab with process noise added to the system, with measurement noise added to the system, and with feedback added to the system. The identification models ARX (Auto Regression Moving Average), AR (a special case of ARX) and BJ (Box-Jenkin) have been used.

    From the results, it follows difficult to adapt a good transfer function using the ARX model to data. This is because of bad coherence. When identifying the transfer function using a spectrum, an AR model, a good approximation was seen, since the approximation does agree well with the spectral estimate. Here the input is not used.

    When identifying using an uncorrelated noise vector as input, we get a bias in the approximation, since the output can not be fully explained by the input signal.

  • 49.
    Andersson, Sofie
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Nikou, Alexandros
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Control Synthesis for Multi-Agent Systems under Metric Interval Temporal Logic Specifications2017In: IFAC-PapersOnLine, Elsevier, 2017, Vol. 50, 2397-2402 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a framework for automatic synthesis of a control sequence for multi-agent systems governed by continuous linear dynamics under timed constraints. First, the motion of the agents in the workspace is abstracted into individual Transition Systems (TS). Second, each agent is assigned with an individual formula given in Metric Interval Temporal Logic (MITL) and in parallel, the team of agents is assigned with a collaborative team formula. The proposed method is based on a correct-by-construction control synthesis method, and hence guarantees that the resulting closed-loop system will satisfy the desired specifications. The specifications considers boolean-valued properties under real-time bounds. Extended simulations has been performed in order to demonstrate the efficiency of the proposed methodology.

  • 50.
    Andersson, Sören
    et al.
    Linköping University.
    Millnert, Mille
    Linköping University.
    Viberg, Mats
    Linköping University.
    Wahlberg, Bo
    KTH, Superseded Departments, Signals, Sensors and Systems.
    A study of adaptive arrays for mobile communication systems1991In: Proceedings - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing, Toronto, Ont, Can, 1991, Vol. 5, no Piscataway, NJ, United States, 3289-3292 p.Conference paper (Refereed)
    Abstract [en]

    The application of adaptive antenna techniques to increase the channel capacity in mobile radio communication is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding following by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.

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