Change search
Refine search result
123 1 - 50 of 116
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abdalmoaty, Mohamed R.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Consistent Estimators of Stochastic MIMO Wiener Models based on Suboptimal Predictors2018Conference paper (Refereed)
  • 2.
    Abdalmoaty, Mohamed R.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Linear Prediction Error Methods for Stochastic Nonlinear Models2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836Article in journal (Refereed)
    Abstract [en]

    The estimation problem for stochastic parametric nonlinear dynamical models is recognized to be challenging. The main difficulty is the intractability of the likelihood function and the optimal one-step ahead predictor. In this paper, we present relatively simple prediction error methods based on non-stationary predictors that are linear in the outputs. They can be seen as extensions of the linear identification methods for the case where the hypothesized model is stochastic and nonlinear. The resulting estimators are defined by analytically tractable objective functions in several common cases. It is shown that, under certain identifiability and standard regularity conditions, the estimators are consistent and asymptotically normal. We discuss the relationship between the suggested estimators and those based on second-order equivalent models as well as the maximum likelihood method. The paper is concluded with a numerical simulation example as well as a real-data benchmark problem.

  • 3.
    Adaldo, Antonio
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Event-triggered and cloud-support control of multi-robot systems2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In control of multi-robot systems, the aim is to obtain a coordinated behavior through local interactions among the robots. A multi-agent system is an abstract model of a multi-robot system. In this thesis, we investigate multi-agent systems where inter-agent communication is modeled by discrete events triggered by conditions on the internal state of the agents. We consider two models of communication. In the first model, two agents exchange information directly with each other. In the second model, all information is exchanged asynchronously over a shared repository. Four contributions on control algorithms for multi-agent systems are offered in the thesis. The first contribution is an event-triggered pinning control algorithm for a network of agents with nonlinear dynamics and time-varying topology. Pinning control is a strategy to steer the behavior of the system in a desired manner by controlling only a small fraction of the agents. We express the controllability of the network in terms of an average value of the network connectivity over time, and we show that all the agents can be driven to a desired reference trajectory. The second contribution is a control algorithm for multi-agent systems where inter-agent communication is substituted with a shared remote repository hosted on a cloud. The communication between each agent and the cloud is modeled as a sequence of events scheduled recursively by the agent. We quantify the connectivity of the network and we show that it is possible to synchronize the multi-agent system to the same state trajectory, while guaranteeing that two consecutive cloud accesses by the same agent are separated by a lower-bounded time interval. The third contribution is a family of distributed controllers for coverage and surveillance tasks with a network of mobile agents with anisotropic sensing patterns. We develop an abstract model of the environment under inspection and define a measure of the coverage attained by the sensor network. We show that the network attains nondecreasing coverage, and we characterize the equilibrium configurations of the network. The fourth contribution is a distributed, cloud-supported control algorithm for inspection of 3D structures with a network of mobile sensing agents, similar to those considered in the third contribution. We develop an abstract model of the structure to inspect and quantify the degree of completion of the inspection. We demonstrate that, under the proposed algorithm, the network is guaranteed to complete the inspection in finite time. All results presented in the thesis are corroborated by numerical simulations and sometimes by experiments with aerial robotic platforms. The experiments show that the theory and methods developed in the thesis are of practical relevance.

  • 4.
    Adaldo, Antonio
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Cloud-supported effective coverage of 3D structures2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 95-100, article id 8550377Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a distributed algorithm for cloud-supported effective coverage of 3D structures with a network of sensing agents. The structure to inspect is abstracted into a set of landmarks, where each landmark represents a point or small area of interest, and incorporates information about position and orientation. The agents navigate the environment following the proposed control algorithm until all landmarks have reached a satisfactory level of coverage. The agents do not communicate with each other directly, but exchange data through a shared cloud repository which is accessed asynchronously and intermittently. We show formally that, under the proposed control architecture, the networked agents complete the coverage mission in finite time. The results are corroborated by simulations in ROS, and experimental evaluation is in progress.

  • 5.
    Adaldo, Antonio
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Liuzza, Davide
    Univ Sannio, Dept Engn, I-82100 Benevento, Italy..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Cloud-Supported Formation Control of Second-Order Multiagent Systems2018In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 5, no 4, p. 1563-1574Article in journal (Refereed)
    Abstract [en]

    This paper addresses a formation problem for a network of autonomous agents with second-order dynamics and bounded disturbances. Coordination is achieved by having the agents asynchronously upload (download) data to (from) a shared repository, rather than directly exchanging data with other agents. Well-posedness of the closed-loop system is demonstrated by showing that there exists a lower bound for the time interval between two consecutive agent accesses to the repository. Numerical simulations corroborate the theoretical results.

  • 6.
    Aleksandrauskaite, Ruth
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Analysis of Velocity Estimation Methods for High-Performance Motion Control Systems2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The majority of all commercial electronics hardware is manufactured usingSurface Mount Technology (SMT). Nevertheless, the increased complexityand miniaturization of electronics impose tough performance requirementson the automation process.The research in this paper concerns test and analysis of alternative velocityestimation methods for high-performance embedded motion control systems.The motion system in Mycronic’s pick and place machines is regulated by amotion controller consisting of a feedforward component and a feedback controller.The linear displacement is measured with an incremental encoder andthe velocity is estimated with a state observer. Previous work suggests thatthe velocity estimation is inadequate.Different observer designs including state and disturbance estimators weretested and evaluated through simulations in MATLAB SIMULINKr. Afterthat, experiments were performed on a conveyor retrieved from a pick andplace machine.The results show that a Kalman filter is the best state estimator. However,the method requires extensive tuning to attain good performance. The trackingperformance and robustness of the motion control system was highly improvedwhen using a Perturbation observer with Kalman filtering. Nonetheless,the settling time for point-to-point movements was somewhat shorterwhen using a Kalman filter alone.

  • 7.
    Andersson, Sofie
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Human in the Loop Least Violating Robot Control Synthesis under Metric Interval Temporal Logic Specifications2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 453-458, article id 8550179Conference paper (Refereed)
    Abstract [en]

    Recently, multiple frameworks for control synthesis under temporal logic have been suggested. The frameworks allow a user to give one or a set of robots high level tasks of different properties (e.g. temporal, time limited, individual and cooperative). However, the issue of how to handle tasks, which either seem to be or are infeasible, remains unsolved. In this paper we introduce a human to the loop, using the human's feedback to determine preference towards different types of violations of the tasks. We introduce a metric of violation called hybrid distance. We also suggest a novel framework for synthesizing a least violating controller with respect to the hybrid distance and the human feedback. Simulation result indicate that the suggested framework gives reasonable estimates of the metric, and that the suggested plans correspond to the expected ones.

  • 8. Ansari, R. Jaberzadeh
    et al.
    Karayiannidis, Yiannis
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Reducing the human effort for human-robot cooperative object manipulation via control design2017In: IFAC PAPERSONLINE, ELSEVIER SCIENCE BV , 2017, Vol. 50, no 1, p. 14922-14927Conference paper (Refereed)
    Abstract [en]

    This study is concerned with the shared object manipulation problem in a physical Human-Robot Interaction (pHRI) setting. In such setups, the operator manipulates the object with the help of a robot. In this paper, the operator is assigned with the lead role, and the robot is passively following the forces/torques exerted by the operator. We propose a controller that is free from the well-known translation/rotation problem and enhances the operator's ability to move the object by reducing the human effort. The key point in our study is that the controller is defined based on the instantaneous center of rotation. The passivity of the system including the object and the manipulator has been evaluated. Simulation results validate the theoretical findings on different scenarios of subsequent rotations and translations of the object.

  • 9.
    Ardah, Khaled
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440970 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, Radio Dept, S-16480 Stockholm, Sweden.
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440970 Fortaleza, Ceara, Brazil..
    Freitas, Walter C., Jr.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440970 Fortaleza, Ceara, Brazil..
    Cavalcanti, Francisco R. P.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60440970 Fortaleza, Ceara, Brazil..
    A Novel Cell Reconfiguration Technique for Dynamic TDD Wireless Networks2018In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 3, p. 320-323Article in journal (Refereed)
    Abstract [en]

    In dynamic time division duplexing (DTDD) systems, the uplink (UL) and downlink (DL) resources can be configured to adapt to changing traffic conditions. Therefiwe, DTDD systems are advantageously deployed in scenarios in which the UL and DL traffic demands are asymmetric and timevarying. Unfortunately, multicell DTDD systems give rise to base station-to-base station and user equipment-to-user equipment interference, that can severely degrade the system performance. Previous works on DTDD either assumed that the UL/DL configurations are given, or they did not take into account the negative impact of multicell DTDD interference. In this letter, we propose a novel cell reconfiguration technique that considers both the prevailing traffic conditions and multicell interference levels. The proposed technique is based on an efficient solution of a mixed integer linear program, whose objective is to maximize the overall system throughput taking into account users' traffic preferences. Realistic system level simulations indicate that the proposed scheme outperforms not only the static TDD system but also other reference schemes, that disregard the DTDD specific interference effects.

  • 10.
    Ardah, Khaled
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, SE-16480 Stockholm, Sweden.
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Freitas, Walter C., Jr.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Cavalcanti, Francisco R. P.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    A Unifying Design of Hybrid Beamforming Architectures Employing Phase Shifters or Switches2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 11, p. 11243-11247Article in journal (Refereed)
    Abstract [en]

    Hybrid beamfiorming (BF) architectures employing phase shifters or switches reduce the number of required radio frequency chains and the power consumption of base stations that employ a large number of antennas. Due to the inherent tradeoff between the number of radio frequency chains, the complexity of the employed analog and digital BF algorithms and the achieved spectral and energy efficiency, designing hybrid BF architectures is a complex task. To deal with this ormplexity, we propose a unifying design that is applicable to architectures employing either phase shifters or switches. In our design, the analog part (!if the hybrid BF architecture maximizes the capacity of the equivalent channel, while the digital part is updated using the well-known block diagonalizat' approach. We then employ the proposed joint analog-digital beamforming algorithm on lour recently proposed hybrid architectures and compare their performance in terms of spectral and energy efficiency, and find that the proposed analog-digital BF algorithm outperforms previously proposed schemes. We also find that phase shifterbased architectures achieve high spectral efficiency, whereas switching-based architectures can boost energy efficiency with increasing number of base station antennas.

  • 11.
    Ardah, Khaled
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, Fortaleza, Ceara, Brazil..
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, Fortaleza, Ceara, Brazil..
    Freitas, Walter C., Jr.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, Fortaleza, Ceara, Brazil..
    Cavalcanti, Francisco R. P.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    An ADMM Approach to Distributed Coordinated Beamforming in Dynamic TDD Networks2017In: 2017 IEEE 7TH INTERNATIONAL WORKSHOP ON COMPUTATIONAL ADVANCES IN MULTI-SENSOR ADAPTIVE PROCESSING (CAMSAP), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    We consider a dynamic time division duplexing wireless network and propose a distributed coordinated beamforming algorithm based on Alternating Direction Method of Multipliers (ADMM) technique assuming the availability of perfect channel state information. Our design objective is to minimize the sum transmit power at the base stations subject to minimum signal-to-interference-plus-noise ratio (SINR) constraints for downlink mobile stations and a maximum interference power threshold for uplink mobile stations. First, we propose a centralized algorithm based on the relaxed Semidefinite Programming (SDP) technique. To obtain the beamforming solution in a distributed way, we further propose a distributed coordinated beamforming algorithm using the ADMM technique. Detailed simulation results are presented to examine the effectiveness of the proposed algorithms. It is shown that the proposed algorithm achieves better performance in terms of the design objective and converges faster than the reference algorithm based on primal decomposition.

  • 12.
    B. da Silva Jr., Jose Mairton
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Ghauch, Hadi
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    How to Split UL/DL Antennas in Full-DuplexCellular Networks2018In: IEEE International Conference on Communication (ICC’18): ThirdWorkshop on Full-Duplex Communications for Future Wireless Networks, Kansas City, MO, USA: IEEE Communications Society, 2018Conference paper (Refereed)
    Abstract [en]

    To further improve the potential of full-duplex com-munications, networks may employ multiple antennas at thebase station or user equipment. To this end, networks thatemploy current radios usually deal with self-interference andmulti-user interference by beamforming techniques. Althoughprevious works investigated beamforming design to improvespectral efficiency, the fundamental question of how to split theantennas at a base station between uplink and downlink infull-duplex networks has not been investigated rigorously. Thispaper addresses this question by posing antenna splitting as abinary nonlinear optimization problem to minimize the sum meansquared error of the received data symbols. It is shown that thisis an NP-hard problem. This combinatorial problem is dealt withby equivalent formulations, iterative convex approximations, anda binary relaxation. The proposed algorithm is guaranteed toconverge to a stationary solution of the relaxed problem with muchsmaller complexity than exhaustive search. Numerical resultsindicate that the proposed solution is close to the optimal in bothhigh and low self-interference capable scenarios, while the usuallyassumed antenna splitting is far from optimal. For large numberof antennas, a simple antenna splitting is close to the proposedsolution. This reveals that the importance of antenna splittingdiminishes with the number of antennas.

  • 13.
    Barros da Silva Jr., José Mairton
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. Royal Inst Technol, KTH, Stockholm, Sweden..
    Ghauch, Hadi
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    How to Split UL/DL Antennas in Full-Duplex Cellular Networks2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    To further improve the potential of full-duplex communications, networks may employ multiple antennas at the base station or user equipment. To this end, networks that employ current radios usually deal with self-interference and multi-user interference by beamforming techniques. Although previous works investigated beamforming design to improve spectral efficiency, the fundamental question of how to split the antennas at a base station between uplink and downlink in full-duplex networks has not been investigated rigorously. This paper addresses this question by posing antenna splitting as a binary nonlinear optimization problem to minimize the sum mean squared error of the received data symbols. It is shown that this is an NP-hard problem. This combinatorial problem is dealt with by equivalent formulations, iterative convex approximations, and a binary relaxation. The proposed algorithm is guaranteed to converge to a stationary solution of the relaxed problem with much smaller complexity than exhaustive search. Numerical results indicate that the proposed solution is close to the optimal in both high and low self-interference capable scenarios, while the usually assumed antenna splitting is far from optimal. For large number of antennas, a simple antenna splitting is close to the proposed solution. This reveals that the importance of antenna splitting diminishes with the number of antennas.

  • 14.
    Baumann, Dominik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Max Planck Institute for Intelligent Systems.
    Fast and Resource-Efficient Control of Wireless Cyber-Physical Systems2019Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Cyber-physical systems (CPSs) tightly integrate physical processes with computing and communication to autonomously interact with the surrounding environment.This enables emerging applications such as autonomous driving, coordinated flightof swarms of drones, or smart factories. However, current technology does notprovide the reliability and flexibility to realize those applications. Challenges arisefrom wireless communication between the agents and from the complexity of thesystem dynamics. In this thesis, we take on these challenges and present three maincontributions.We first consider imperfections inherent in wireless networks, such as communication delays and message losses, through a tight co-design. We tame the imperfectionsto the extent possible and address the remaining uncertainties with a suitable controldesign. That way, we can guarantee stability of the overall system and demonstratefeedback control over a wireless multi-hop network at update rates of 20-50 ms.If multiple agents use the same wireless network in a wireless CPS, limitedbandwidth is a particular challenge. In our second contribution, we present aframework that allows agents to predict their future communication needs. Thisallows the network to schedule resources to agents that are in need of communication.In this way, the limited resource communication can be used in an efficient manner.As a third contribution, to increase the flexibility of designs, we introduce machinelearning techniques. We present two different approaches. In the first approach,we enable systems to automatically learn their system dynamics in case the truedynamics diverge from the available model. Thus, we get rid of the assumption ofhaving an accurate system model available for all agents. In the second approach, wepropose a framework to directly learn actuation strategies that respect bandwidthconstraints. Such approaches are completely independent of a system model andstraightforwardly extend to nonlinear settings. Therefore, they are also suitable forapplications with complex system dynamics.

  • 15. Beerens, R.
    et al.
    Bisoffi, Andrea
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Zaccarian, L.
    Heemels, W. P. M. H.
    Nijmeijer, H.
    Van De Wouw, N.
    Hybrid PID control for transient performance improvement of motion systems with friction2018In: 2018 Annual American Control Conference (ACC), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 539-544, article id 8431613Conference paper (Refereed)
    Abstract [en]

    We present a novel reset control approach to improve transient performance of a PID-controlled motion system subject to friction. In particular, a reset integrator is applied to circumvent the depletion and refilling process of a linear integrator when the system overshoots the setpoint, thereby significantly reducing settling times. Moreover, robustness for unknown static friction levels is obtained. A hybrid closed-loop system formulation is derived, and stability follows from a discontinuous Lyapunov-like function and a meagre-limsup invariance argument. The working principle of the controller is illustrated by means of a numerical example.

  • 16.
    Biel, Martin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Norrlof, Mikael
    Efficient Trajectory Reshaping in a Dynamic Environment2018In: 2018 IEEE 15TH INTERNATIONAL WORKSHOP ON ADVANCED MOTION CONTROL (AMC), IEEE, 2018, p. 54-59Conference paper (Refereed)
    Abstract [en]

    A general trajectory planner for optimal control problems is presented and applied to a robot system. The approach is based on timed elastic bands and nonlinear model predictive control. By exploiting the sparsity in the underlying optimization problems the computational effort can be significantly reduced, resulting in a real-time capable planner. In addition, a localization based switching strategy is employed to enforce convergence and stability. The planning procedure is illustrated in a robotics application using a realistic SCARA type robot.

  • 17.
    Bisoffi, Andrea
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    A hybrid barrier certificate approach to satisfy linear temporal logic specifications2018In: 2018 Annual American Control Conference (ACC), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 634-639, article id 8430795Conference paper (Refereed)
    Abstract [en]

    In this work we formulate the satisfaction of a (syntactically co-safe) linear temporal logic specification on a physical plant through a recent hybrid dynamical systems formalism. In order to solve this problem, we introduce an extension to such a hybrid system framework of the so-called eventuality property, which matches suitably the condition for the satisfaction of such a temporal logic specification. The eventuality property can be established through barrier certificates, which we derive for the considered hybrid system framework. Using a hybrid barrier certificate, we propose a solution to the original problem. Simulations illustrate the effectiveness of the proposed method. 2018 AACC.

  • 18. Boem, F.
    et al.
    Zhou, Y.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Parisini, T.
    Distributed Pareto-optimal state estimation using sensor networks2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 93, p. 211-223Article in journal (Refereed)
    Abstract [en]

    A novel model-based dynamic distributed state estimator is proposed using sensor networks. The estimator consists of a filtering step – which uses a weighted combination of information provided by the sensors – and a model-based predictor of the system's state. The filtering weights and the model-based prediction parameters jointly minimize – at each time-step – the bias and the variance of the prediction error in a Pareto optimization framework. The simultaneous distributed design of the filtering weights and of the model-based prediction parameters is considered, differently from what is normally done in the literature. It is assumed that the weights of the filtering step are in general unequal for the different state components, unlike existing consensus-based approaches. The state, the measurements, and the noise components are allowed to be individually correlated, but no probability distribution knowledge is assumed for the noise variables. Each sensor can measure only a subset of the state variables. The convergence properties of the mean and of the variance of the prediction error are demonstrated, and they hold both for the global and the local estimation errors at any network node. Simulation results illustrate the performance of the proposed method, obtaining better results than state of the art distributed estimation approaches.

  • 19. Bombois, X.
    et al.
    Korniienko, A.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Scorletti, G.
    Optimal identification experiment design for the interconnection of locally controlled systems2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 89, p. 169-179Article in journal (Refereed)
    Abstract [en]

    This paper considers the identification of the modules of a network of locally controlled systems (multi-agent systems). Its main contribution is to determine the least perturbing identification experiment that will nevertheless lead to sufficiently accurate models of each module for the global performance of the network to be improved by a redesign of the decentralized controllers. Another contribution is to determine the experimental conditions under which sufficiently informative data (i.e. data leading to a consistent estimate) can be collected for the identification of any module in such a network. 

  • 20.
    Cavalcante, Eduardo de Olivindo
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, SE-16480 Stockholm, Sweden.
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Freitas Jr, Walter C.
    Univ Fed Ceara, Wireless Telecom Res Grp, BR-60020181 Fortaleza, Ceara, Brazil..
    Distributed Beamforming in Dynamic TDD MIMO Networks With BS to BS Interference Constraints2018In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 5, p. 788-791Article in journal (Refereed)
    Abstract [en]

    This letter proposes distributed beamforming as a means of reducing interference in dynamic time division duplexing multiple input multiple output networks. Specifically, we formulate an optimization task, whose objective is to minimize the base station (BS) transmit power, while satisfying a predefined signal-to-interference-plus-noise ratio threshold for each downlink user equipment and keeping the BS to BS interference power below a tolerable level. An iterative decentralized solution requiring reduced signaling load based on primal decomposition is proposed. This decentralized algorithm is shown to iterate towards the centralized solution, while feasible but suboptimal solutions can be obtained at any iteration.

  • 21.
    Chong, Michelle
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Sandsten, M.
    Rantzer, A.
    Estimating the Wigner distribution of linear time-invariant dynamical systems2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1220-1225Conference paper (Refereed)
    Abstract [en]

    An estimation algorithm for the Wigner distribution (time-frequency representation) of the unmeasured states of a linear time-invariant system is presented. Given that the inputs and outputs are measured, the algorithm involves designing a Luenberger-like observer for each frequency of interest. Under noise-free conditions, we show that the es- timates converge to the true Wigner distribution under a detectability assumption on the time-frequency representation. The estimation algorithm provides estimates which converge to a neighbourhood of the true Wigner distribution where its norm is dependent on the norm of the measurement noise. We also illustrate the efficacy of the estimation algorithm on an academic example and a model of neuron populations.

  • 22.
    Colombo, Leonardo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Clark, W.
    Bloch, A.
    Time reversal symmetries and zero dynamics for simple hybrid Hamiltonian control systems2018In: 2018 Annual American Control Conference (ACC), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 2218-2223Conference paper (Refereed)
    Abstract [en]

    This paper studies Hamel's formalism for simple hybrid mechanical control systems and explores the role of time-reversal symmetries and hybrid zero dynamics to predict the existence of periodic orbits in these control system. A time reversal symmetry in the phase-space permits us to construct a time reversible hybrid Hamiltonian system. If the Hamiltonian function describing the continuous dynamics and the impact map are invariants under a time reversal symmetry on the zero hybrid dynamics, under some mild conditions, we find sufficient conditions for the existence of periodic solutions for the class of simple hybrid Hamiltonian control systems.

  • 23.
    Colombo, Leonardo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Optimal Control of Left-Invariant Multi-Agent Systems with Asymmetric Formation Constraints2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1728-1733, article id 8550238Conference paper (Refereed)
    Abstract [en]

    In this work we study an optimal control problem for a multi-agent system modeled by an undirected formation graph with nodes describing the kinematics of each agent, given by a left invariant control system on a Lie group. The agents should avoid collision between them in the workspace. Such a task is done by introducing some potential functions into the cost functional for the optimal control problem, corresponding to fictitious forces, induced by the formation constraint among agents, that break the symmetry of the individual agents and the cost functions, and rendering the optimal control problem partially invariant by a Lie group of symmetries. Reduced necessary conditions for the existence of normal extremals are obtained using techniques of variational calculus on manifolds. As an application we study an optimal control problem for multiple unicycles.

  • 24.
    Curinga, Florian
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Autonomous racing using model predictive control2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Autonomous vehicles are expected to have a significant impact on our societies by freeinghumans from the driving task, and thus eliminating the human factor in one of themost dangerous places: roads. As a matter of facts, road kills are one of the largest sourceof human deaths and many countries put the decrease of these casualties as one of their toppriorities. It is expected that autonomous vehicles will dramatically help in achieving that.Moreover, using controllers to optimize both the car behaviour on the road and higher leveltraffic management could reduce traffic jams and increase the commuting speed overall.To minimize road kills, an approach is to design controllers that would handle the car atits limits of handling, by integrating complex dynamics such as adherence loss it is possibleto prevent the car from leaving the road. A convenient setup to evaluate this type ofcontrollers is a racing context: a controller is steering a car to complete a track as fast aspossible without leaving the road and by brining the car to its limits of handling.In this thesis, we design a controller for an autonomous vehicle with the goal of driving itfrom A to B as fast as possible. This is the main motivation in racing applications. Thecontroller should steer the car with the goal to minimize the racing time.This controller was designed within the model predictive controller (MPC) framework,where we used the concept of road-aligned model. In contrast with the standard mpc techniques,we use the objective function to maximize the progress along the reference path,by integrating a linear model of the vehicle progression along the centerline. Combinedwith linear vehicle model and constraints, a optimization problem providing the vehiclewith the future steering and throttle values to apply is formulated and solved with linearprogramming in an on-line fashion during the race. We show the effectiveness of our controllerin simulation, where the designed controller exhibits typical race drivers behavioursand strategies when steering a vehicle along a given track. We ultimately confront it withsimilar controllers from the literature, and derive its strength and weaknesses compared tothem.

  • 25.
    De Campos, Gabriel Rodrigues
    et al.
    Politecn Milan, Dept DEIB, Via Ponzio 34-5, I-20133 Milan, Italy..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Seuret, Alexandre
    Univ Toulouse, CNRS LAAS, Equipe MAC, 7 Ave Colonel Roche,BP 54200, F-31031 Toulouse 4, France..
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Distributed control of compact formations for multi-robot swarms2018In: IMA Journal of Mathematical Control and Information, ISSN 0265-0754, E-ISSN 1471-6887, Vol. 35, no 3, p. 805-835Article in journal (Refereed)
    Abstract [en]

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

  • 26.
    Della Penda, Demia
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Device-to-Device Communication in Future Cellular Networks: Resource allocation and mode selection2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The widespread use of smart devices and mobile applications is leading to a massive growth of wireless data traffic. Supporting the upcoming demands of data volume, communication rate, and system capacity requires reconsideration of the existing network architecture. Traditionally, users communicate through the base station via uplink/downlink paths. By allowing device-to-device (D2D) communication, that is, direct transmission between the users, we can enhance both efficiency and scalability of future networks. In this thesis, we address some of the challenges brought by the integration of D2D communication in cellular systems, and validate the potential of this technology by means of proper resource management solutions. Our main contributions lie in the context of mode selection, power control, and frequency/time resource allocation mechanisms. First, we investigate how the integration of D2D communication in dynamic Time Division Duplex systems can enhance the energy efficiency. We propose a joint optimization of mode selection, uplink/downlink transmission time, and power allocation to minimize the energy consumption. The optimization problem is formulated as a mixed-integer nonlinear programming problem, which is NP-hard in general. By exploiting the problem structure, we develop efficient (and for some scenarios, optimal) solutions. We complement the work with a heuristic scheme that achieves near-optimal solutions while respecting practical constraints in terms of execution times and signaling overhead. Second, we study the performance of several power control strategies applicable to D2D-enabled networks. In particular, we compare 3GPP LTE uplink power control with a distributed scheme based on utility maximization. Furthermore, to extend the application of well-known power control approaches to Rician-fading environments, we propose a power allocation scheme based on the concept of coherent-measure-of-risk. This approach allows to obtain a convex and efficiently solvable problem. Third, we study the subcarrier allocation problem in D2D-enabled networks. We maximize the total transmission rate by modeling the problem as a potential game. Nash equilibria of the game correspond to local optima of the objective function, which are found via better-response dynamic implemented with message passing approach. Finally, we propose two different applications of full-duplex technology for D2D communication. First, we present a practical mode selection algorithm that leverages only the existing control signaling to minimize the users' probability of outage. Second, we investigate how the combination of D2D relaying and full-duplex operations can improve the network coverage and the communication quality without additional infrastructure deployment.

  • 27.
    Demirel, Burak
    et al.
    Paderborn Univ, Chair Automat Control EIME, D-33098 Paderborn, Germany..
    Ghadimi, Euhanna
    Huawei Technol Sweden AB, SE-16494 Kista, Sweden..
    Quevedo, Daniel E.
    Paderborn Univ, Chair Automat Control EIME, D-33098 Paderborn, Germany..
    Johansson, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Optimal Control of Linear Systems With Limited Control Actions: Threshold-Based Event-Triggered Control2018In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 5, no 3, p. 1275-1286Article in journal (Refereed)
    Abstract [en]

    We consider a finite-horizon linear-quadratic optimal control problem where only a limited number of control messages are allowed for sending from the controller to the actuator. To restrict the number of control actions computed and transmitted by the controller, we employ a threshold-based event-triggering mechanism that decides whether or not a control message needs to be calculated and delivered. Due to the nature of threshold-based event-triggering algorithms, finding the optimal control sequence requires minimizing a quadratic cost function over a nonconvex domain. In this paper, we first provide an exact solution to this nonconvex problem by solving an exponential number of quadratic programs. To reduce computational complexity, we then propose two efficient heuristic algorithms based on greedy search and the alternating direction method of multipliers technique. Later, we consider a receding horizon control strategy for linear systems controlled by event-triggered controllers, and we further provide a complete stability analysis of receding horizon control that uses finite-horizon optimization in the proposed class. Numerical examples testify to the viability of the presented design technique.

  • 28.
    Drollinger, Nadine
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Developing a System for Robust Planning using Linear Temporal Logic2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Human robot-collaborative search missions have gotten more and more attention in recent years.Especially in scenarios where the robot first scouts the scene before sending in human agents. Thissaves time and avoids unnecessary risks for the human agents. One possible configuration of such arescue team is, a human operator instructing a unmanned aerial vehicle (UAV) via speech-commandshow to traverse through an environment to investigate areas of interest. A first step to address thisproblem is presented in this master thesis by developing a framework for mapping temporal logicinstructions to physical motion of a UAV.The fact that natural language has a strong resemblance to the logic formalism of Linear-TemporalLogic (LTL) is exploited. Constraints expressed as an LTL-formula are imposed on a provided labeledmap of the environment. An LTL-to-cost-map converter including a standard input-skeleton is developed.Respective cost maps are obtained and a satisfaction-measure of fulfilling these constraints ispresented. The input-skeleton and the map-converter are then combined with a cost-map-based pathplanning algorithm in order to obtain solution sets. A clarification request is created such that theoperator can choose which solution set should be executed. The proposed framework is successivelyvalidated, first by MATLAB-experiments to ensure the validity of the cost-map-creation followed bysimulation experiments in ROS incorporating the entire framework. Finally, a real-world experimentis performed at the SML to validate the proposed framework.

  • 29.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Gkatzikis, Lazaros
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    On Maximizing Sensor Network Lifetime by Energy Balancing2018In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 5, no 3Article in journal (Refereed)
    Abstract [en]

    Many physical systems, such as water/electricity distribution networks, are monitored by battery-powered wireless-sensor networks (WSNs). Since battery replacement of sensor nodes is generally difficult, long-term monitoring can be only achieved if the operation of the WSN nodes contributes to long WSN lifetime. Two prominent techniques to long WSN lifetime are 1) optimal sensor activation and 2) efficient data gathering and forwarding based on compressive sensing. These techniques are feasible only if the activated sensor nodes establish a connected communication network (connectivity constraint), and satisfy a compressive sensing decoding constraint (cardinality constraint). These two constraints make the problem of maximizing network lifetime via sensor node activation and compressive sensing NP-hard. To overcome this difficulty, an alternative approach that iteratively solves energy balancing problems is proposed. However, understanding whether maximizing network lifetime and energy balancing problems are aligned objectives is a fundamental open issue. The analysis reveals that the two optimization problems give different solutions, but the difference between the lifetime achieved by the energy balancing approach and the maximum lifetime is small when the initial energy at sensor nodes is significantly larger than the energy consumed for a single transmission. The lifetime achieved by energy balancing is asymptotically optimal, and that the achievable network lifetime is at least 50% of the optimum. Analysis and numerical simulations quantify the efficiency of the proposed energy balancing approach.

  • 30.
    Elfeky, Ahmed
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Methods of calibration for different functions of a SCR-system2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The goal of this research is to try and compare different methods ofcalibration in order to tune the parameters of the pumping and tankheater monitoring functions of the AdBlue Delivery Module of a SelectiveCatalytic Reduction (SCR) system. The goal of the SCR systemis to reduce the emission of NOx gases, which are considered as greenhousegases.In a first step, while calibrating the parameters of the pumping function,a real-time calibration method has been used. The advantage inthis process is that a detailed model of the system is not needed totune it. Then, the tank heater monitoring function has been calibratedthrough simulations. The understanding of the system is better in thiscase, which could help tuning it more effectively.The results shows that both methods should ensure the proper functioningof the system. However, the parameters found in this studycould not be totally approved without being tested on vehicle, in reallifeconditions. Moreover, as the priority is to avoid the malfunctionof the system, the chosen parameters might not be the optimal ones interms of performance.With these two methods, most of the systems could be calibrated. Thechoice of the method should be done according to the initial level ofknowledge of the object of study

  • 31.
    Everitt, Niklas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Galrinho, Miguel
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Open-loop asymptotically efficient model reduction with the Steiglitz–McBride method2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 89, p. 221-234Article in journal (Refereed)
    Abstract [en]

    In system identification, it is often difficult to use a physical intuition when choosing a noise model structure. The importance of this choice is that, for the prediction error method (PEM) to provide asymptotically efficient estimates, the model orders must be chosen according to the true system. However, if only the plant estimates are of interest and the experiment is performed in open loop, the noise model can be over-parameterized without affecting the asymptotic properties of the plant. The limitation is that, as PEM suffers in general from non-convexity, estimating an unnecessarily large number of parameters will increase the risk of getting trapped in local minima. Here, we consider the following alternative approach. First, estimate a high-order ARX model with least squares, providing non-parametric estimates of the plant and noise model. Second, reduce the high-order model to obtain a parametric model of the plant only. We review existing methods to do this, pointing out limitations and connections between them. Then, we propose a method that connects favorable properties from the previously reviewed approaches. We show that the proposed method provides asymptotically efficient estimates of the plant with open-loop data. Finally, we perform a simulation study suggesting that the proposed method is competitive with state-of-the-art methods.

  • 32. Fang, Mengyuan
    et al.
    Galrinho, Miguel
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Recursive Identification Based on Weighted Null-Space Fitting2017In: 2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Algorithms for online system identification consist in updating the estimated model while data are being collected. A standard method for online identification of structured models is the recursive prediction error method (PEM). The problem is that PEM does not have an exact recursive formulation, and the need to rely on approximations makes recursive PEM prone to convergence problems. In this paper, we propose a recursive implementation of weighted null-space fitting, an asymptotically efficient method for identification of structured models. Consisting only of (weighted) least-squares steps, the recursive version of the algorithm has the same convergence and statistical properties of the off-line version. We illustrate these properties with a simulation study, where the proposed algorithm always attains the performance of the off-line version, while recursive PEM often fails to converge.

  • 33.
    Farokhi, Farhad
    et al.
    CSIROs Data61, Canberra, ACT, Australia.; Univ Melbourne, Dept Elect & Elect Engn, Melbourne, Vic, Australia..
    Sandberg, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Dept Automat Control, Stockholm, Sweden..
    Ensuring privacy with constrained additive noise by minimizing Fisher information2019In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 99, p. 275-288Article in journal (Refereed)
    Abstract [en]

    The problem of preserving the privacy of individual entries of a database when responding to linear or nonlinear queries with constrained additive noise is considered. For privacy protection, the response to the query is systematically corrupted with an additive random noise whose support is a subset or equal to a pre-defined constraint set. A measure of privacy using the inverse of the trace of the Fisher information matrix is developed. The Cramer-Rao bound relates the variance of any estimator of the database entries to the introduced privacy measure. The probability density that minimizes the trace of the Fisher information (as a proxy for maximizing the measure of privacy) is computed. An extension to dynamic problems is also presented. Finally, the results are compared to the differential privacy methodology. Crown Copyright

  • 34.
    Farokhi, Farhad
    et al.
    Univ Melbourne, Melbourne Informat Decis & Autonomous Syst Lab, Parkville, Vic 3010, Australia.;Univ Melbourne, Dept Elect & Elect Engn, Parkville, Vic 3010, Australia..
    Sandberg, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Fisher Information as a Measure of Privacy: Preserving Privacy of Households With Smart Meters Using Batteries2018In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 9, no 5, p. 4726-4734Article in journal (Refereed)
    Abstract [en]

    In this paper, batteries are used to preserve the privacy of households with smart meters. It is commonly understood that data from smart meters can be used by adversaries to infringe on the privacy of the households, e.g., figuring out the individual appliances that are being used or the level of the occupancy of the house. The Cramer-Rao bound is used to relate the variance of the estimation error of any unbiased estimator of the household consumption from the aggregate consumption (i.e., the household plus the battery) to the Fisher information. Subsequently, optimal policies for charging and utilizing batteries are devised to minimize the Fisher information (in the scalar case and the trace of the Fisher information matrix in the multi-variable case) as a proxy for maximizing the variance of the estimation error of the electricity consumption by adversaries (irrespective of their estimation policies). The policies are chosen to respect the physical constraints of the battery regarding capacity, initial charge, and rate constraints. The results are demonstrated on real power measurement data with non-intrusive load monitoring algorithms.

  • 35.
    Feyzmahdavian, Hamid Reza
    et al.
    ABB Corp Res Ctr, S-72226 Vasteras, Sweden..
    Besselink, Bart
    Univ Groningen, Johann Bernoulli Inst Math & Comp Sci, NL-9712 CP Groningen, Netherlands..
    Johansson, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Stability Analysis of Monotone Systems via Max-Separable Lyapunov Functions2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 3, p. 643-656Article in journal (Refereed)
    Abstract [en]

    We analyze stability properties of monotone nonlinear systems via max-separable Lyapunov functions, motivated by the following observations: first, recent results have shown that asymptotic stability of a monotone nonlinear system implies the existence of a max-separable Lyapunov function on a compact set; second, for monotone linear systems, asymptotic stability implies the stronger properties of D-stability and insensitivity to time delays. This paper establishes that for monotone nonlinear systems, equivalence holds between asymptotic stability, the existence of a max-separable Lyapunov function, D-stability, and insensitivity to bounded and unbounded time-varying delays. In particular, a new and general notion of D-stability for monotone nonlinear systems is discussed, and a set of necessary and sufficient conditions for delay-independent stability are derived. Examples show how the results extend the state of the art.

  • 36.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, Stockholm, Swede.
    Mode selection schemes for unicasting device-to-device communications supported by network coding2018In: International Journal of Communication Systems, ISSN 1074-5351, E-ISSN 1099-1131, Vol. 31, no 11, article id e3594Article in journal (Refereed)
    Abstract [en]

    Device-to-device (D2D) communication in a cellular spectrum increases the spectral and energy efficiency of local communication sessions, while also taking advantage of accessing licensed spectrum and higher transmit power levels than when using unlicensed bands. To realize the potential benefits of D2D communications, appropriate mode selection algorithms that select between the cellular and D2D communication modes must be designed. On the other hand, physical-layer network coding (NWC) at a cellular base stationwhich can be used without D2D capabilitycan also improve the spectral efficiency of a cellular network that carries local traffic. In this paper, we ask whether cellular networks should support D2D communications, physical-layer NWC, or both. To this end, we study the performance of mode selection algorithms that can be used in cellular networks that use physical-layer NWC and support D2D communications. We find that the joint application of D2D communication and NWC scheme yields additional gains compared with a network that implements only one of these schemes, provided that the network implements proper mode selection and resource allocation algorithms. We propose 2 mode selection schemes that aim to achieve high signal-to-interference-plus-noise ratio and spectral efficiency, respectively, and take into account the NWC and D2D capabilities of the network.

  • 37.
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Performance Comparison of Practical Resource Allocation Schemes for Device-to-Device Communications2018In: Wireless Communications & Mobile Computing, ISSN 1530-8669, E-ISSN 1530-8677, article id 3623075Article in journal (Refereed)
    Abstract [en]

    Device-to-device (D2D) communications in cellular spectrum have the potential of increasing the spectral and energy efficiency by taking advantage of the proximity and reuse gains. Although several resource allocation (RA) and power control (PC) schemes have been proposed in the literature, a comparison of the performance of such algorithms as a function of the available channel state information has not been reported. In this paper, we examine which large scale channel gain knowledge is needed by practically viable RA and PC schemes for network assisted D2D communications. To this end, we propose a novel near-optimal and low-complexity RA scheme that can be advantageously used in tandem with the optimal binary power control scheme and compare its performance with three heuristics-based RA schemes that are combined either with the well-known 3GPP Long-Term Evolution open-loop path loss compensating PC or with an iterative utility optimal PC scheme. When channel gain knowledge about the useful as well as interfering (cross) channels is available at the cellular base station, the near-optimal RA scheme, termedMatching, combined with the binary PC scheme is superior. Ultimately, we find that the proposed low-complexity RA + PC tandem that uses some cross-channel gain knowledge provides superior performance.

  • 38.
    Galrinho, Miguel
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    System Identification with Multi-Step Least-Squares Methods2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The purpose of system identification is to build mathematical models for dynam-ical systems from experimental data. With the current increase in complexity of engineering systems, an important challenge is to develop accurate and computa-tionally simple algorithms, which can be applied in a large variety of settings.With the correct model structure, maximum likelihood (ML) and the predictionerror method (PEM) can be used to obtain (under adequate assumptions) asymp-totically efficient estimates. A disadvantage is that these methods typically requireminimizing a non-convex cost function. Alternative methods are then needed toprovide initialization points for the optimization.In this thesis, we consider multi-step least-squares methods for identificationof dynamical systems. These methods have a long history for estimation of timeseries. Typically, a non-parametric model is estimated in an intermediate step, andits residuals are used as estimates of the innovations of the parametric model ofinterest. With innovations assumed known, it is possible to estimate the parametricmodel with afinite number of least-squares steps. When applied with an appropriateweighting orfiltering, these methods can provide asymptotically efficient estimates.The thesis is divided in two parts. In thefirst part, we propose two methods:model order reduction Steiglitz-McBride (MORSM) and weighted null-spacefitting(WNSF). MORSM uses the non-parametric model estimate to create a simulateddata set, which is then used with the Steiglitz-McBride algorithm. WNSF is a moregeneral approach, which motivates the parametric model estimate by relating thecoefficients of the non-parametric and parametric models.In settings where different multi-step least-squares methods can be applied, weshow that their algorithms are essentially the same, whether the estimates are basedon estimated innovations, simulated data, or direct relations between the modelcoefficients. However, their range of applicability may differ, with WNSF allowing usto establish a framework for multi-step least-squares methods that is quiteflexible inparametrization. This is specially relevant in the multivariate case, for which WNSFis applicable to a large variety of model structures, including both matrix-fractionand element-wise descriptions of the transfer matrices.We conduct a rigorous statistical analysis of the asymptotic properties of WNSF,where the main challenge is to keep track of the errors introduced by truncationof the non-parametric model, whose order must tend to infinity as function of thesample size for consistency and asymptotic efficiency to be attained. Moreover, weperform simulation studies that show promising results compared with state-of-the-art methods.In the second part, we consider extensions of the developed methods for appli-cability in other settings. These include unstable systems, recursive identification,dynamic networks, and cascaded systems.

  • 39.
    Gao, Yulong
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Stochastic Invariance and Aperiodic Control for Uncertain Constrained Systems2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Uncertainties and constraints are present in most control systems. For example, robot motion planning and building climate regulation can be modeled as uncertain constrained systems. In this thesis, we develop mathematical and computational tools to analyze and synthesize controllers for such systems.

    As our first contribution, we characterize when a set is a probabilistic controlled invariant set and we develop tools to compute such sets. A probabilistic controlled invariantset is a set within which the controller is able to keep the system state with a certainprobability. It is a natural complement to the existing notion of robust controlled invariantsets. We provide iterative algorithms to compute a probabilistic controlled invariantset within a given set based on stochastic backward reachability. We prove that thesealgorithms are computationally tractable and converge in a finite number of iterations. The computational tools are demonstrated on examples of motion planning, climate regulation, and model predictive control.

    As our second contribution, we address the control design problem for uncertain constrained systems with aperiodic sensing and actuation. Firstly, we propose a stochastic self-triggered model predictive control algorithm for linear systems subject to exogenous disturbances and probabilistic constraints. We prove that probabilistic constraint satisfaction, recursive feasibility, and closed-loop stability can be guaranteed. The control algorithm is computationally tractable as we are able to reformulate the problem into a quadratic program. Secondly, we develop a robust self-triggered control algorithm for time-varying and uncertain systems with constraints based on reachability analysis. In the particular case when there is no uncertainty, the design leads to a control system requiring minimum number of samples over finite time horizon. Furthermore, when the plant is linear and the constraints are polyhedral, we prove that the previous algorithms can be reformulated as mixed integer linear programs. The method is applied to a motion planning problem with temporal constraints.

  • 40.
    Ghadimi, Euhanna
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Teixeira, André
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rabbat, Michael G.
    McGill Univ, Dept Elect & Comp Engn, Montreal, PQ, Canada..
    Johansson, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    The ADMM algorithm for distributed averaging: Convergence rates and optimal parameter selection2014In: CONFERENCE RECORD OF THE 2014 FORTY-EIGHTH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS & COMPUTERS / [ed] Matthews, M B, IEEE COMPUTER SOC , 2014, p. 783-787Conference paper (Refereed)
    Abstract [en]

    We derive the optimal step-size and over-relaxation parameter that minimizes the convergence time of two ADMM-based algorithms for distributed averaging. Our study shows that the convergence times for given step-size and over-relaxation parameters depend on the spectral properties of the normalized Laplacian of the underlying communication graph. Motivated by this, we optimize the edge-weights of the communication graph to improve the convergence speed even further. The performance of the ADMM algorithms with our parameter selection are compared with alternatives from the literature in extensive numerical simulations on random graphs.

  • 41.
    Giraldo, Jairo
    et al.
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Urbina, David
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Cardenas, Alvaro
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Valente, Junia
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Faisal, Mustafa
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Ruths, Justin
    Univ Texas Dallas, Erik Jonsson Sch Engn & Comp Sci, 800 W Campbell Rd, Richardson, TX 75080 USA..
    Tippenhauer, Nils Ole
    Singapore Univ Technol & Design, Informat Syst Technol & Design Pillar, 8 Somapah Rd, Singapore 487372, Singapore..
    Sandberg, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Candell, Richard
    NIST, Networked Control Syst Grp, 100 Bur Dr, Gaithersburg, MD 20899 USA..
    A Survey of Physics-Based Attack Detection in Cyber-Physical Systems2018In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 51, no 4, article id 76Article in journal (Refereed)
    Abstract [en]

    Monitoring the "physics" of cyber-physical systems to detect attacks is a growing area of research. In its basic form, a security monitor creates time-series models of sensor readings for an industrial control system and identifies anomalies in these measurements to identify potentially false control commands or false sensor readings. In this article, we review previous work on physics-based anomaly detection based on a unified taxonomy that allows us to identify limitations and unexplored challenges and to propose new solutions.

  • 42.
    Gkatzikis, Lazaros
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Koutsopoulos, Iordanis
    AUEB, Athens, Greece.;Ctr Res & Technol Hellas CERTH, Thermi, Greece..
    Mobiles on Cloud Nine: Efficient Task Migration Policies for Cloud Computing Systems2014In: 2014 IEEE 3RD INTERNATIONAL CONFERENCE ON CLOUD NETWORKING (CLOUDNET), IEEE , 2014, p. 204-210Conference paper (Refereed)
    Abstract [en]

    Due to limited processing and energy resources, mobile devices outsource their computationally intensive tasks to the cloud. However, clouds are shared facilities and hence task execution time may vary significantly. In this paper, we investigate the potential of task migrations to reduce contention for the shared resources of a mobile cloud computing architecture in which local clouds are attached to wireless access infrastructure (e.g. wireless base stations or access points). We devise online migration strategies that at each time make migration decisions according to the instantaneous load and the anticipated execution time. We explicitly take into account the interaction of co-located tasks in a server and the cost of migrations. We propose three classes of migration policies, ranging from fully uncoordinated ones, in which each user or server autonomously makes its migration decisions, up to cloud-wide ones, where migration decisions are made by the cloud provider. The key underlying idea is that a migration should occur only if it is beneficial for the processing time of the task, including the migration delay.

  • 43.
    Gonzalez, Rodrigo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Vargas, F. J.
    Chen, J.
    Stabilization of MIMO systems over additive correlated noise channels subject to multiple SNR-constraints2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1493-1498Conference paper (Refereed)
    Abstract [en]

    This paper studies the mean square stabilization of MIMO discrete-time linear time-invariant systems over a MIMO additive correlated channel. We assume that such channel consists of multiple correlated SISO channels subject to independent input signal-to-noise ratio (SNR) constraints. We derive explicit conditions for which mean square stabilization can be achieved under such constraints for unstable minimum phase plants, and characterize the controller that achieves such SNR. We also present the set of admissible SNR constraints for mean square stability for a particular set of plants. Our results show that noise correlation can reduce the SNR requirements for stability compared to independent additive white noise channels. In addition, a numerical simulation is provided to illustrate the theoretical results.

  • 44.
    Guimaraes, Francisco R. V.
    et al.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Fodor, Gabor
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Ericsson Res, S-16483 Stockholm, Sweden.
    Freitas, Walter C., Jr.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Silva, Yuri C. B.
    Univ Fed Ceara, Wireless Telecom Res Grp GTEL, CP 6005, BR-60440970 Fortaleza, Ceara, Brazil..
    Pricing-Based Distributed Beamforming for Dynamic Time Division Duplexing Systems2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 4, p. 3145-3157Article in journal (Refereed)
    Abstract [en]

    Multicell dynamic time division duplexing (TDD) systems make it possible to adapt the number of uplink and downlink time slots in each cell to the prevailing cell-wide traffic demand. Although dynamic TDD systems can be advantageously deployed in scenarios in which the uplink and downlink traffic demands are asymmetric and time varying, dynamic TDD systems give rise to base station to base station (BS-to-BS) interference and user equipment to user equipment (UE-to-UE) interference that negatively impact the system performance. In this paper, we propose employing a distributed beamforming scheme to mitigate the BS-to-BS interference and thereby to improve the uplink performance. Specifically, the proposed scheme uses interference pricing to find the appropriate precoder vectors at the BSs, which also improves the signal-to-interference-plus-noise ratio (SINR) performance in the downlink. We compare the performance of the pricing-based (PB) beamforming scheme with that of zero-forcing beamforming in an outdoor picocell environment specified by the 3rd Generation Partnership Project using a realistic system simulator. We find that the proposed PB scheme boosts the SINR in the uplink at the expense of a small degradation of the downlink SINR compared with the zero-forcing scheme. On the other hand, the PB beamforming approach can significantly reduce the downlink transmit power levels and thereby improve the overall energy efficiency of the system.

  • 45.
    Gunnar, Anders
    et al.
    KTH, School of Electrical Engineering (EES).
    Johansson, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Robust load-balancing under statistical uncertainty: models and polynomial-time algorithms2009In: 2009 NEXT GENERATION INTERNET NETWORKS, IEEE , 2009, p. 99-+Conference paper (Refereed)
    Abstract [en]

    We study the problem of guaranteed-performance routing under statistical traffic uncertainty. Relevant traffic models are presented and a polynomial-time algorithm for solving the associated robust routing problem is given. We demonstrate how our techniques, in combination with fundamental limitations on the accuracy of estimated traffic matrices, enable us to compute bounds on the achievable performance of OSPF-routing optimized using only topology information and link count data. We discuss extensions to other types of traffic uncertainties and describe an alternative, more memory efficient, algorithm based on combined constraint and column generation. The proposed techniques are evaluated in several numerical examples to highlight the features of our approach.

  • 46.
    Guo, Meng
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, ACCESS Linnaeus Ctr, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Andersson, Sofie
    KTH. KTH Royal Inst Technol, ACCESS Linnaeus Ctr, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, ACCESS Linnaeus Ctr, Sch Elect Engn, SE-10044 Stockholm, Sweden..
    Human-in-the-Loop Mixed-Initiative Control under Temporal Tasks2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), IEEE Computer Society, 2018, p. 6395-6400Conference paper (Refereed)
    Abstract [en]

    This paper considers the motion control and task planning problem of mobile robots under complex high-level tasks and human initiatives. The assigned task is specified as Linear Temporal Logic (LTL) formulas that consist of hard and soft constraints. The human initiative influences the robot autonomy in two explicit ways: with additive terms in the continuous controller and with contingent task assignments. We propose an online coordination scheme that encapsulates (i) a mixed-initiative continuous controller that ensures all-time safety despite of possible human errors, (ii) a plan adaptation scheme that accommodates new features discovered in the workspace and short-term tasks assigned by the operator during run time, and (iii) an iterative inverse reinforcement learning (IRL) algorithm that allows the robot to asymptotically learn the human preference on the parameters during the plan synthesis. The results are demonstrated by both realistic human-in-the-loop simulations and experiments.

  • 47.
    Ha, Huong
    et al.
    Univ Newcastle, Sch Elect Engn & Comp, Newcastle, NSW, Australia..
    Welsh, James S.
    Univ Newcastle, Sch Elect Engn & Comp, Newcastle, NSW, Australia..
    Rojas, Cristian R.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Wahlberg, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    An analysis of the SPARSEVA estimate for the finite sample data case2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 96, p. 141-149Article in journal (Refereed)
    Abstract [en]

    In this paper, we develop an upper bound for the SPARSEVA (SPARSe Estimation based on a VAlidation criterion) estimation error in a general scheme, i.e., when the cost function is strongly convex and the regularized norm is decomposable for a pair of subspaces. We show how this general bound can be applied to a sparse regression problem to obtain an upper bound of the estimation error for the traditional I-1 SPARSEVA problem. Numerical results are used to illustrate the effectiveness of the suggested bound. 

  • 48.
    Hajiesmaili, Mohammad Hassan
    et al.
    Johns Hopkins Univ, Whiting Sch Engn, Baltimore, MD 21218 USA..
    Talebi, Mohammad Sadegh
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. K.
    Khonsari, Ahmad
    Univ Tehran, Dept Elect & Comp Engn, Tehran 1417614418, Iran.;Inst Res Fundamental Sci, Sch Comp Sci, Tehran 1953833511, Iran..
    Multiperiod Network Rate Allocation With End-to-End Delay Constraints2018In: IEEE Transactions on Big Data, ISSN 2325-5870, E-ISSN 2168-6750, Vol. 5, no 3, p. 1087-1097Article in journal (Refereed)
    Abstract [en]

    QoS-aware networking applications such as real-time streaming and video surveillance systems require nearly fixed average end-to-end delay over long periods to communicate efficiently, although may tolerate some delay variations in short periods. This variability exhibits complex dynamics that makes rate control of such applications a formidable task. This paper addresses rate allocation for heterogeneous QoS-aware applications that preserves the long-term end-to-end delay constraint while seeking the maximum network utility cumulated over a fixed time interval. To capture the temporal dynamics of sources, we incorporate a novel time-coupling constraint in which delay sensitivity of sources is considered such that a certain end-to-end average delay for each source over a prespecified time interval is satisfied. We propose an algorithm, as a dual-based solution, which allocates source rates for the next time interval in a distributed fashion, given the knowledge of network parameters in advance. Also, we extend the algorithm to the case that the problem data is not known fully in advance to capture more realistic scenarios. Through numerical experiments, we show that our proposed algorithm attains higher average link utilization and a wider range of feasible scenarios in comparison with the best, to our knowledge, rate control schemes that may guarantee such constraints on delay.

  • 49.
    Ishizaki, Takayuki
    et al.
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Sadamoto, Tomonori
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Imura, Jun-ichi
    Tokyo Inst Technol, Meguro Ku, 2-12-1 Ookayama, Tokyo 1528552, Japan..
    Sandberg, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Retrofit control: Localization of controller design and implementation2018In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 95, p. 336-346Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a retrofit control method for stable network systems. The proposed approach is a control method that, rather than an entire system model, requires a model of the subsystem of interest for controller design. To design the retrofit controller, we use a novel approach based on hierarchical state-space expansion that generates a higher-dimensional cascade realization of a given network system. The upstream dynamics of the cascade realization corresponds to an isolated model of the subsystem of interest, which is stabilized by a local controller. The downstream dynamics can be seen as a dynamical model representing the propagation of interference signals among subsystems, the stability of which is equivalent to that of the original system. This cascade structure enables a systematic analysis of both the stability and control performance of the resultant closed-loop system. The resultant retrofit controller is formed as a cascade interconnection of the local controller and an output rectifier that rectifies an output signal of the subsystem of interest so as to conform to an output signal of the isolated subsystem model while acquiring complementary signals neglected in the local controller design, such as interconnection signals from neighboring subsystems. Finally, the efficiency of the retrofit control method is demonstrated through numerical examples of power systems control and vehicle platoon control. 

  • 50.
    Iwaki, Takuya
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Wireless Sensor Network Scheduling and Event-based Control for Industrial Processes2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Control over wireless sensor and actuator networks is of growing interest in process industry since it enables flexible design, deployment, operation, and maintenance. An important problem in industrial wireless control is how to limit the amount of information that needs to be exchanged over the network. In this thesis, network scheduling and remote control co-design is considered to address this problem.

    In the first part, we propose a design of an optimal network schedule for state estimation over a multi-hop wireless sensor network. We formulate an optimization problem, minimizing a linear combination of the averaged estimation error and transmission energy. A periodic network schedule is obtained, which specifies when and through which routes each sensor in the network should transmit its measurement, so that an optimal remote estimate under sensor energy consideration is achieved. We also propose some suboptimal schedules to reduce the computational load. The effectiveness of the suboptimal schedules is evaluated in numerical examples.

    In the second part, we propose a co-design framework for sensor scheduling, routing, and control over a multi-hop wireless sensor and actuator network. For a decoupled plant and LQG control performance, we formulate an optimization problem and show that the optimal schedule, routing, and control can be obtained locally for each control loop. In this part, we also introduce algorithms to reconfigure the schedules and routes when a link in the network is disconnected. The results are illustrated in a numerical example.

    In the third part, we consider event-based feedforward control from a wireless disturbance sensor. We derive stability conditions when the closed-loop system is subject to actuator saturation. Feedforward control with anti-windup compensation is introduced to reduce the effect of actuator saturation. The effectiveness of the approach is illustrated in some numerical examples.

123 1 - 50 of 116
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf