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  • 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.
    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.

  • 5. 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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9. 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.

  • 10.
    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.

  • 11.
    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.

  • 12. 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.

  • 13. 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. 

  • 14.
    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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    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

  • 23.
    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.

  • 24. 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.

  • 25.
    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.

  • 26.
    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.

  • 27.
    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.

  • 28.
    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.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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.

  • 33.
    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. 

  • 34.
    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.

  • 35.
    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. 

  • 36.
    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.

  • 37.
    Iwaki, Takuya
    et al.
    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.
    LQG Control and Scheduling Co-design for Wireless Sensor and Actuator Networks2018In: 2018 IEEE 19TH INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING ADVANCES IN WIRELESS COMMUNICATIONS (SPAWC), IEEE , 2018, p. 146-150Conference paper (Refereed)
    Abstract [en]

    This paper studies a co-design problem of control, scheduling and routing over a multi-hop sensor and actuator network subject to energy-saving consideration. Sensors are observing multiple independent linear systems and transmit their data to actuators in which controllers are co-located. We formulate an optimization problem, minimizing a linear combination of the averaged linear quadratic Gaussian control performance and the averaged transmission energy consumption. Optimal solutions are derived and their performance is illustrated in a numerical example. Algorithms to reconfigure routing between sensors and actuators in case of link disconnection are also provided.

  • 38.
    Jafarian, Matin
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Robust consensus of unicycles using ternary and hybrid controllers2017In: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 27, no 17, p. 4013-4034Article in journal (Refereed)
    Abstract [en]

    This paper presents consensus of the orientations and average positions for a group of unicycles using ternary and hybrid controllers. The decentralized controllers designed to reach consensus of the average positions take only values in the set {-1; 0; +1}. In addition, a hybrid controller is introduced to control the orientations. Finite-time practical consensus of the average positions is proven despite the simple ternary control laws together with asymptotic consensus of the orientations. Furthermore, the consensus problem is studied in the presence of matched input disturbances that are locally rejected using an internal-model-based controller. The analysis is performed in a hybrid framework. Simulation results illustrate the effectiveness of the design.

  • 39. Jin, L.
    et al.
    Čičić, Mladen
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Amin, S.
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Modeling the impact of vehicle platooning on highway congestion: A fluid qeuing approach2018In: HSCC 2018 - Proceedings of the 21st International Conference on Hybrid Systems: Computation and Control (part of CPS Week), Association for Computing Machinery (ACM), 2018, p. 237-246Conference paper (Refereed)
    Abstract [en]

    Vehicle platooning is a promising technology that can lead to significant fuel savings and emission reduction. However, the macroscopic impact of vehicle platoons on highway traffic is not yet well understood. In this article, we propose a new fluid queuing model to study the macroscopic interaction between randomly arriving vehicle platoons and the background traffic at highway bottlenecks. This model, viewed as a stochastic switched system, is analyzed for two practically relevant priority rules: proportional (or mixed) and segmented priority. We provide intuitive stability conditions, and obtain bounds on the long-run average length and variance of queues for both priority rules. We use these results to study how platoon-induced congestion varies with the fraction of platooned vehicles, and their characteristics such as intra-platoon spacing and arrival rate. Our analysis reveals a basic tradeoff between congestion induced by the randomness of platoon arrivals, and efficiency gain due to a tighter intra-platoon spacing. This naturally leads to conditions under which the proportional priority is preferred over segmented priority. Somewhat surprisingly, our analytical results are in agreement with the simulation results based on a more sophisticated two-class cell transmission model.

  • 40.
    Jin, Ming
    et al.
    Univ Calif Berkeley, Dept Elect Engn & Comp Sci, Berkeley, CA 94720 USA..
    Lavaei, Javad
    Univ Calif Berkeley, Dept Ind Engn & Operat Res, Berkeley, CA 94720 USA..
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    A Semidefinite Programming Relaxation under False Data Injection Attacks against Power Grid AC State Estimation2017In: 55th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 236-243Conference paper (Refereed)
    Abstract [en]

    The integration of sensing and information technology renders the power grid susceptible to cyber-attacks. To understand how vulnerable the state estimator is, we study its behavior under the worst attacks possible. A general false data injection attack (FDIA) based on the AC model is formulated, where the attacker manipulates sensor measurements to mislead the system operator to make decisions based on a falsified state. To stage such an attack, the optimization problem incorporates constraints of limited resources (allowing only a limited number of measurements to be altered), and stealth operation (ensuring the cyber hack cannot be identified by the bad data detection algorithm). Due to the nonlinear AC power flow model and combinatorial selection of compromised sensors, the problem is nonconvex and cannot be solved in polynomial time; however, it is shown that convexification of the original problem based on a semidefinite programming (SDP) relaxation and a sparsity penalty is able to recover a near-optimal solution. This represents the first study to solve the AC-based FDIA. Simulations on a 30-bus system illustrate that the proposed attack requires only sparse sensor manipulation and remains stealthy from the residual-based bad data detection mechanism. In light of the analysis, this study raises new challenges on grid defense mechanism and attack detection strategy.

  • 41.
    Koch, Christian Ernst Siegfried
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Model Predictive Control for Six Degrees-of-Freedom Station-Keeping of an Underwater Vehicle-Manipulator System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Underwater robotics are a reliable and ecient mean for exploration and surveysin a submarine environment. Albeit, intervention tasks, e.g. installationand maintenance, require the expansive and hazardous deployment of professionaldivers. Lightweight unmanned underwater vehicles equipped with a multi-degreeof-freedom manipulator, have been proposed as an alternative. However, the controlof these vehicle-manipulator systems is challenging due to their non-linearhigh-dimensional coupled dynamics. The central problem explored in this thesis,is station keeping of an underwater vehicle under the inuence of a moving manipulator.The manipulator is represented by predictable disturbing forces andmoments. The proposed control scheme is a Model Predictive Control (MPC) algorithmwith preview of the disturbances. In simulation, performance of the MPCscheme is evaluated for dierent degrees of knowledge about the disturbances.Results are compared to a classical feedback controller.

  • 42.
    Kokogias, Stefanos
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Integrated Transport Research Lab, ITRL.
    Svensson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Pereira, Goncalo Collares
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Oliveira, Rui
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, Dept Automat Control, S-10044 Stockholm, Sweden..
    Zhang, Xinhai
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Song, Xinwu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Mårtensson, Jonas
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Development of Platform-Independent System for Cooperative Automated Driving Evaluated in GCDC 20162018In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 19, no 4, p. 1277-1289Article in journal (Refereed)
    Abstract [en]

    Cooperative automated driving is a promising development in reducing energy consumption and emissions, increasing road safety, and improving traffic flow. The Grand Cooperative Driving Challenge (GCDC) 2016 was an implementation oriented project with the aim to accelerate research and development in the field. This paper describes the development of the two vehicle systems with which KTH participated in GCDC 2016. It presents a reference system architecture for collaborative automated driving as well as its instantiation on two conceptually different vehicles: a Scania truck and the research concept vehicle, built at KTH. We describe the common system architecture, as well as the implementation of a selection of shared and individual system functionalities, such as V2X communication, localization, state estimation, and longitudinal and lateral control. We also present a novel approach to trajectory tracking control for a four-wheel steering vehicle using model predictive control and a novel method for achieving fair data age distribution in vehicular communications.

  • 43.
    Korniienko, A.
    et al.
    Univ Lyon, Ecole Cent Lyon, Lab Ampere, F-69134 Ecully, France..
    Bombois, X.
    Univ Lyon, Ecole Cent Lyon, Lab Ampere, F-69134 Ecully, France..
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Scorletti, G.
    Univ Lyon, Ecole Cent Lyon, Lab Ampere, F-69134 Ecully, France..
    Hierarchical Robust Analysis for Identified Systems in Network2018In: IFAC PAPERSONLINE, ELSEVIER SCIENCE BV , 2018, Vol. 51, no 25, p. 383-389Conference paper (Refereed)
    Abstract [en]

    This paper considers worst-case robustness analysis of a network of locally controlled uncertain systems with uncertain parameter vectors belonging to the ellipsoid sets found by identification procedures. In order to deal with computational complexity of large-scale systems, an hierarchical robustness analysis approach is adapted to these uncertain parameter vectors thus addressing the trade-off between the computation time and the conservatism of the result.

  • 44.
    Lee, Seung Jae
    et al.
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea.;Seoul Natl Univ, Automat & Syst Res Inst, Seoul, South Korea..
    Yoo, Jaehyun
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH Royal Inst Technol, Sch Elect Engn, Stockholm, Sweden..
    Kim, H. Jin
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea.;Seoul Natl Univ, Automat & Syst Res Inst, Seoul, South Korea..
    Design, Modeling and Control of T-3-Multirotor: a Tilting Thruster Type Multirotor2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), IEEE Computer Society, 2018, p. 1214-1219Conference paper (Refereed)
    Abstract [en]

    This paper presents a new design of multirotor, named as 'Tilting Thruster Type' (T-3)-multirotor. The new platform is equipped with mechanically separated thrusters, which can take any fuselage posture within a specified range regardless of any direction of translational acceleration. A specially designed servo-linkage mechanism is employed for relative attitude control between the thruster and the fuselage. Mathematical modeling and analysis of the new platform are conducted to explore the control method of the dynamically complex system. For demonstrating the potential of the new T(3-)multirotor, an autonomous level flight is performed where the fuselage maintains zero roll and pitch angle during the entire flight. Both simulation and experimental results are provided with detailed analysis.

  • 45. Li, Bo
    et al.
    Wu, Junfeng
    Qi, Hongsheng
    Proutiere, Alexandre
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Shi, Guodong
    Boolean Gossip Networks2018In: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 26, no 1, p. 118-130Article in journal (Refereed)
    Abstract [en]

    This paper proposes and investigates a Boolean gossip model as a simplified but non-trivial probabilistic Boolean network. With positive node interactions, in view of standard theories from Markov chains, we prove that the node states asymptotically converge to an agreement at a binary random variable, whose distribution is characterized for large-scale networks by mean-field approximation. Using combinatorial analysis, we also successfully count the number of communication classes of the positive Boolean network explicitly in terms of the topology of the underlying interaction graph, where remarkably minor variation in local structures can drastically change the number of network communication classes. With general Boolean interaction rules, emergence of absorbing network Boolean dynamics is shown to be determined by the network structure with necessary and sufficient conditions established regarding when the Boolean gossip process defines absorbing Markov chains. Particularly, it is shown that for the majority of the Boolean interaction rules, except for nine out of the total 2(16) - 1 possible nonempty sets of binary Boolean functions, whether the induced chain is absorbing has nothing to do with the topology of the underlying interaction graph, as long as connectivity is assumed. These results illustrate the possibilities of relating dynamical properties of Boolean networks to graphical properties of the underlying interactions.

  • 46.
    Lima, Pedro F.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. ECPM, Scania CV AB.
    Optimization-Based Motion Planning and Model Predictive Control for Autonomous Driving: With Experimental Evaluation on a Heavy-Duty Construction Truck2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis addresses smooth motion planning and path following control of autonomous large and heavy industrial vehicles, such as trucks and buses, using optimization-based techniques. Autonomous driving is a rapidly expanding technology that promises to play an important role in future society, since it aims at more energy efficient, more convenient, and safer transport systems.

    First, we propose a clothoid-based path sparsification algorithm to describe a reference path. This approach relies on a sparseness regularization technique such that a minimal number of clothoids is used to describe the reference path.

    Second, we introduce a novel framework, in which path planning problems are posed in a convex optimization format, even when considering the vehicle dimension constraints, which maximizes the path planning performance in very constrained environments. 

    Third, we present a progress maximization (i.e., traveling time minimization) model predictive controller for autonomous vehicles. The proposed controller optimizes the vehicle lateral and longitudinal motion simultaneously and its effectiveness is demonstrated, in simulation, even in the presence of obstacles.

    Fourth, we design a smooth and accurate model predictive controller tailored for industrial vehicles, where the main goal is to reduce the vehicle "wear and tear" during its operation. The controller effectiveness is shown both in simulation and experimentally in a Scania construction truck. We showed that the proposed controller has an extremely promising performance in real experiments.

    Fifth, we propose a novel terminal cost and a terminal state set in order to guarantee closed-loop stability when designing and implementing a linear time-varying model predictive controller for autonomous path following. The controller successfully stabilizes an autonomous Scania construction truck.

  • 47.
    Lindemann, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Robust Motion Planning employing Signal Temporal Logic2017In: 2017 AMERICAN CONTROL CONFERENCE (ACC), IEEE , 2017, p. 2950-2955Conference paper (Refereed)
    Abstract [en]

    Motion planning classically concerns the problem of accomplishing a goal configuration while avoiding obstacles. However, the need for more sophisticated motion planning methodologies, taking temporal aspects into account, has emerged. To address this issue, temporal logics have recently been used to formulate such advanced specifications. This paper will consider Signal Temporal Logic in combination with Model Predictive Control. A robustness metric, called Discrete Average Space Robustness, is introduced and used to maximize the satisfaction of specifications which results in a natural robustness against noise. The comprised optimization problem is convex and formulated as a Linear Program.

  • 48.
    Magureanu, Stefan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Efficient Online Learning under Bandit Feedback2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis we address the multi-armed bandit (MAB) problem with stochastic rewards and correlated arms. Particularly, we investigate the case when the expected rewards are a Lipschitz function of the arm and extend these results to bandits with arbitrary structure that is known to the decision maker. In these settings, we derive problem specific regret lower bounds and propose both an asymptotically optimal algorithm (OSLB and OSSB respectively) and (pareto) optimal algorithms (POSLB and POSB, in the generic setting). We further examine the \emph{learning to rank} problem, as viewed from a MAB perspective. We construct the regret lower bound and determine its closed form for some particular settings, as well as propose two asymptotically optimal algorithms PIE and PIE-C. We further present a mathematical model of the learning to rank problem where the need for diversity appears naturally and devise an order optimal, numerically competitive algorithm, LDR. For all algorithms mentioned above, we present performance analysis in the form of theoretical regret guarantees as well as numerical evaluation on artificial as well as real-world datasets.

  • 49.
    Mariniello, Dario
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Distributed event-triggered control for collective target localization and circumnavigation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is concerned with accomplishing a localization and circumnavigationmission with a network of autonomous mobile agents. An estimatealgorithm and a decentralized control law are designed, such that every agentestimates the position of a target, and the mobile agents eventually exhibitpersistent rotations about the target at a desired distance, while forming aregular polygon around it. Both the estimator and the controller are based onevent-triggered measurements of the bearing vector (i.e., the unit norm vectorpointing from the agent towards the target location), and event-triggered communicationwithin a communication radius. The convergence proprieties of theproposed algorithm are proven formally for different scenarios, such as stationaryor slowly drifting target with one or more agents. The designed algorithmsare tested through simulations in ROS and experiments using CrazyFlie 2.0nano-quadrotors.

  • 50. Masoumzadeh, Amin
    et al.
    Nekouei, Ehsan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Alpcan, Tansu
    Chattopadhyay, Deb
    Impact of Optimal Storage Allocation on Price Volatility in Energy-Only Electricity Markets2018In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 2, p. 1903-1914Article in journal (Refereed)
    Abstract [en]

    Recent studies show that the fast growing expansion of wind power generation may lead to extremely high levels of price volatility in wholesale electricity markets. Storage technologies, regardless of their specific forms, e.g., pump-storage hydro, large-scale, or distributed batteries, are capable of alleviating the extreme price volatility levels due to their energy usage time shifting, fast-ramping, and price arbitrage capabilities. In this paper, we propose a stochastic bilevel optimization model to find the optimal nodal storage capacities required to achieve a certain price volatility level in a highly volatile energy-only electricity market. The decision on storage capacities is made in the upper level problem and the operation of strategic/regulated generation, storage, and transmission players is modeled in the lower level problem using an extended stochastic (Bayesian) Cournot-based game. The South Australia (SA) electricity market, which has recently experienced high levels of price volatility, and a 30-bus IEEE system are considered as the case studies. Our numerical results indicate that 50% price volatility reduction in the SA electricity market can be achieved by installing either 430-MWh regulated storage or 530-MWh strategic storage. In other words, regulated storage firms are more efficient in reducing the price volatility than strategic storage firms.

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