SwePub - sökning: L773:9783907144008

Numrering	Referens	Omslagsbild	Hitta
1.	Ahmadi, Shervin Parvini, et al. (författare) Efficient Robust Model Predictive Control using Chordality 2019 Ingår i: 2019 18TH EUROPEAN CONTROL CONFERENCE (ECC). - : IEEE. - 9783907144008 ; , s. 4270-4275 Konferensbidrag (refereegranskat)abstract In this paper we show that chordal structure can be used to devise efficient optimization methods for robust model predictive control problems. To this end, first the problem is converted to an equivalent robust quadratic programming formulation. We then illustrate how the chordal structure can be used to distribute the computations in a primal-dual interior-point method among computational agents, which in turn allows us to accelerate the algorithm by efficient parallel computations. We investigate performance of the framework in Julia using numerical examples.
2.	Barbosa, Fernando S., et al. (författare) Integrated motion planning and control under metric interval temporal logic specifications 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783907144008 ; , s. 2042-2049 Konferensbidrag (refereegranskat)abstract This paper proposes an approach that combines motion planning and hybrid feedback control design in order to find and follow trajectories fulfilling a given complex mission involving time constraints. We use Metric Interval Temporal Logic (MITL) as a rich and rigorous formalism to specify such missions. The solution builds on three main steps: (i) using sampling-based motion planning methods and the untimed version of the mission specification in the form of Zone automaton, we find a sequence of waypoints in the workspace; (ii) based on the clock zones from the satisfying run on the Zone automaton, we compute time-stamps at which these waypoints should be reached; and (iii) to control the system to connect two waypoints in the desired time, we design a low-level feedback controller leveraging Time-varying Control Barrier Functions. Illustrative simulation results are included.
3.	Batkovic, Ivo, 1992, et al. (författare) Real-Time Constrained Trajectory Planning and Vehicle Control for Proactive Autonomous Driving with Road Users 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 256-262 Konferensbidrag (refereegranskat)abstract For motion planning and control of autonomous vehicles to be proactive and safe, pedestrians' and other road users' motions must be considered. In this paper, we present a vehicle motion planning and control framework, based on Model Predictive Control, accounting for moving obstacles. Measured pedestrian states are fed into a prediction layer which translates each pedestrians' predicted motion into constraints for the MPC problem. Simulations and experimental validation were performed with simulated crossing pedestrians to show the performance of the framework. Experimental results show that the controller is stable even under significant input delays, while still maintaining very low computational times. In addition, real pedestrian data was used to further validate the developed framework in simulations.
4.	Berkane, Soulaimane, et al. (författare) A hybrid controller for obstacle avoidance in an n-dimensional euclidean space 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783907144008 ; , s. 764-769 Konferensbidrag (refereegranskat)abstract For a vehicle moving in an n-dimensional Euclidean space, we present a construction of a hybrid feedback that guarantees both global asymptotic stabilization of a reference position and avoidance of an obstacle corresponding to a bounded spherical region. The proposed hybrid control algorithm switches between two modes of operation: stabilization (motion-to-goal) and avoidance (boundary-following). The geometric construction of the flow and jump sets of the hybrid controller, exploiting a hysteresis region, guarantees robust switching (chattering-free) between stabilization and avoidance. Simulation results illustrate the performance of the proposed hybrid control approach for a 3-dimensional scenario.
5.	Chong, Michelle, et al. (författare) A Tutorial Introduction to Security and Privacy for Cyber-Physical Systems 2019 Ingår i: Proceedings 2019 18th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 968-978 Konferensbidrag (refereegranskat)abstract This tutorial provides a high-level introduction to novel control-theoretic approaches for the security and privacy of cyber-physical systems (CPS). It takes a risk-based approach to the problem and develops a model framework that allows us to introduce and relate many of the recent contributions to the area. In particular, we explore the concept of risk in the context of CPS under cyber-attacks, paying special attention to the characterization of attack scenarios and to the interpretation of impact and likelihood for CPS. The risk management framework is then used to give an overview of and map different contributions in the area to three core parts of the framework: attack scenario description, quantification of impact and likelihood, and mitigation strategies. The overview is by no means complete, but it illustrates the breadth of the problems considered and the control-theoretic solutions proposed so far.
6.	Darup, Moritz Schulze, et al. (författare) Towards real-time ADMM for linear MPC 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 4276-4282 Konferensbidrag (refereegranskat)abstract We present a novel predictive control scheme for linear constrained systems that uses the alternating direction method of multipliers (ADMM) for online optimization. In contrast to existing works on ADMM-based model predictive control (MPC), we only consider a single ADMM-iteration in every time step. The resulting real-time ADMM scheme is tailored for embedded and fast MPC implementations. The main difference to existing MPC schemes based on real-time iterations is that the proposed controller allows to include state and input constraints of the system. The paper derives the dynamics of the resulting closed-loop system, identifies important parameters of the real-time ADMM, and compares its performance to classical MPC.
7.	Fjällström, Eva, 1980-, et al. (författare) Courses-Concepts-Graphs as a Tool to Measure the Importance of Concepts in University Programmes 2019 Ingår i: 2019 18th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 3076-3083 Konferensbidrag (refereegranskat)abstract This paper investigates methods for quantitatively assessing the importance and relative importance of concepts taught in a university program. This assessment has many uses, e.g., to aid program design and inventory, and for communicating what concepts a course may rely on at a given point in the program. We propose to perform this quantitative assessment in two steps: first, representing the university program as an opportune graph with courses and concepts as nodes and connections between courses and concepts as edges; second, by quantitatively defining each concept's importance as its centrality as a node within the network. We thus perform two investigations, both leveraging a practical case - data collected from two engineering programs at two Swedish university: a) how to represent university programs in terms of graphs (here called Courses-Concepts Graph (CCG)), and b) how to reinterpret the most classical graph-theoretical node centrality indexes in the pedagogical term of concept centrality index.
8.	Greiff, Marcus, et al. (författare) Temporal Viability Regulation for Control Affine Systems with Applications to Mobile Vehicle Coordination under Time-Varying Motion Constraints 2019 Ingår i: The 2019 European Control Conference. - 9783907144008 Konferensbidrag (refereegranskat)abstract Controlled invariant set and viability regulation of dynamical control systems have played important roles in many control and coordination applications. In this paper we develop a \textit{temporal} viability regulation theory for general dynamical control systems, and in particular for control affine systems. The time-varying viable set is parameterized by time-varying constraint functions, with the aim to regulate a dynamical control system to be invariant in the time-varying viable set so that temporal state-dependent constraints are enforced. We consider both time-varying equality and inequality constraints in defining a temporal viable set. We also present sufficient conditions for the existence of feasible control input for the control affine systems. The developed temporal viability regulation theory is applied to mobile vehicle coordination.
9.	Grussler, Christian, et al. (författare) Optimality interpretations for atomic norms 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 1473-1477 Konferensbidrag (refereegranskat)abstract Atomic norms occur frequently in data science and engineering problems such as matrix completion, sparse linear regression, system identification and many more. These norms are often used to convexify non-convex optimization problems, which are convex apart from the solution lying in a non-convex set of so-called atoms. For the convex part being a linear constraint, the ability of several atomic norms to solve the original non-convex problem has been analyzed by means of tangent cones. This paper presents an alternative route for this analysis by showing that atomic norm convexifcations always provide an optimal convex relaxation for some related non-convex problems. As a result, we obtain the following benefits: (i) treatment of arbitrary convex constraints, (ii) potentially obtaining solutions to the non-convex problem with a posteriori success certificates, (iii) utilization of additional prior knowledge through the design or learning of the non-convex problem.
10.	Hult, Robert, 1984, et al. (författare) Optimal Coordination of Automated Vehicles at Intersections with Turns 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 225-230 Konferensbidrag (refereegranskat)abstract In this paper we address the problem of co- ordinating automated vehicles at intersections, with a spe- cial focus on turning maneuvers. The inclusion of rear-end collision avoidance constraints into the problem is decided during turning maneuvers by a smooth function of the vehicle state, rather than integer variables. Moreover, curvature-based acceleration constraints are introduced, which limit the velocity of the vehicle during the turn, and a term in the objective function accounts for passenger comfort. We discuss how the coordination problem is formulated as a nonlinear program and show though simulations that for practical problem instances the proposed approximation is either exact or introduces very little conservativeness.
11.	Jafarian, Matin, et al. (författare) Stochastic phase-cohesiveness of discrete-time Kuramoto oscillators in a frequency-dependent tree network 2019 Ingår i: Proceedings 2019 18th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 1987-1992 Konferensbidrag (refereegranskat)abstract This paper presents the notion of stochastic phase-cohesiveness based on the concept of recurrent Markov chains and studies the conditions under which a discrete-time stochastic Kuramoto model is phase-cohesive. It is assumed that the exogenous frequencies of the oscillators are combined with random variables representing uncertainties. A bidirectional tree network is considered such that each oscillator is coupled to its neighbors with a coupling law which depends on its own noisy exogenous frequency. In addition, an undirected tree network is studied. For both cases, a sufficient condition for the common coupling strength (kappa) and a necessary condition for the sampling-period are derived such that the stochastic phase-cohesiveness is achieved. The analysis is performed within the stochastic systems framework and validated by means of numerical simulations.
12.	Karlsson, Johan, 1991, et al. (författare) Optimal Trajectory Planning and Decision Making in Lane Change Maneuvers Near a Highway Exit 2019 Ingår i: European control conference. - 9783907144008 ; , s. 3254-3260 Konferensbidrag (refereegranskat)abstract In this paper, an optimization based algorithmfor safe and efficient collaborative driving in intersections isformulated. The problem is to determine the optimal orderin which vehicles should travel through an intersection underthe assumptions that the longitudinal velocity of all vehiclescan be controlled along a predefined path. In the originalformulation one quadratic optimization program was solved foreach possible crossing order of the vehicles and collisions wereavoided by formulating constraints that only allowed one vehicleat the time inside the intersection. To make this algorithmmore effective, we formulate less restrictive collision avoidanceconstraints by introducing one critical zone for each point wheretwo predefined paths cross. It is shown that this formulationleads to a decrease in the number of quadratic optimizationprograms that need to be solved to find the best crossingorder. Further, an algorithm is provided that finds the numberof crossing sequences which yield unique formulations of theoptimization program. The results show that when simulatingmore complex scenarios, like four vehicles traveling throughan ordinary intersection, the reduction of computational timeand the total time it takes for all vehicles to make it throughthe intersection can be significantly reduced using these lessrestrictive constraints.
13.	Lindmark, Gustav, 1983-, et al. (författare) Combining centrality measures for control energy reduction in network controllability problems 2019 Ingår i: Proceedings of the 2019 European Control Conference (ECC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9783907144008 - 9783907144015 - 9781728113142 ; , s. 1518-1523 Konferensbidrag (refereegranskat)abstract This paper investigates the problem of controlling a complex network with reduced control energy. Two centrality measures are defined, one related to the energy that a control, placed on a node, can exert on the entire network, and the other related to the energy that the network exerts on a node. We show that by combining these two centrality measures conflicting control energy requirements, like minimizing the average energy needed to steer the state in any direction and the energy needed for the worst direction, can be simultaneously taken into account. From an algebraic point of view, the node ranking that we obtain from the combination of our centrality measures is related to the non-normality of the adjacency matrix of the graph.
14.	Lionello, M., et al. (författare) Lumped-parameters control-oriented gray-box modelling of liquid immersion cooling systems 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9783907144008 ; , s. 3861-3866 Konferensbidrag (refereegranskat)abstract Liquid cooling systems have better heat dissipation capabilities than air based ones, and are expected to become a standard choice in future data centers, due to the ever increasing power density and heat rejection needs of the compute infrastructure. A convenient side-effect of implementing liquid cooling is that it facilitates the efficient recovery of the heat waste. However designing and managing these heat recovery infrastructures benefit from having control-oriented models that can accurately describe how different operating conditions of the to-be-cooled heat sources will affect the thermal status of the coolant. The aim of this manuscript is to derive control-oriented models of liquid immersion cooling systems, i.e., systems where the compute infrastructure is immersed in a vessel filled with dielectric fluid. More specifically we derive, starting from physical interpretations, a general lumped-parameters gray box dynamical model that has-as inputs-the electrical consumption of the heat sources and the working point of the heat recovery system, and has-as outputs-the temperature distribution of the coolant in the most relevant points of the system. Beyond proposing this modelling methodology we also validate the generalization capabilities of the obtainable models. In specific, we test the achievable statistical performances in a field case, plus compare with the ones of classical black box system identification strategies. We thus report that in the considered field case our gray box model reached a fit index of 91.08% when simulating test sets, while the best black box model we have been able to identify reached (on the same test sets) fit indexes of only 72.56%.
15.	Müller, Matias I., et al. (författare) Risk-Coherent H∞-optimal Filter Design Under Model Uncertainty with Applications to MISO Control 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783907144008 ; , s. 1461-1466 Konferensbidrag (refereegranskat)abstract This work presents a framework to address the problem of designing discrete-time LTI (linear and time-invariant) multiple-input and multiple-output (MIMO) filters, aiming to optimize the performance of a system when model uncertainty is considered. Additionally, we present an interesting application to control design for disturbance rejection under model uncertainty. To account for this uncertainty we employ coherent measures of risk, which are a family of measures in theory of risk. We particularly discuss which measures are suitable by comparing the conditional value-at-risk (CVaR) to other three common designs. Using a scenario approach, we derive a convex optimization problem based on linear matrix inequalities (LMIs), whose solution minimizes the risk of falling into poor mathcal{H}{ infty} performance. Finally, we present an application to multiple-input and single-output (MISO) control design under model uncertainty in the auto-covariance function of the output noise, comparing approaches minimizing different notions of risk.
16.	Pirani, Mohammad, et al. (författare) Design of Attack-Resilient Consensus Dynamics : A Game-Theoretic Approach 2019 Ingår i: Proceedings 2019 18th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 2227-2232 Konferensbidrag (refereegranskat)abstract We propose a game-theoretic framework for improving the resilience of multi-agent consensus dynamics in the presence of a strategic attacker. In this game, the attacker selects a set of network nodes to inject the attack signals. The attacker's objective is to minimize the required energy for steering the consensus towards its desired direction. This energy is captured by the trace of controllability Gramian of the system when the input is the attack signal. The defender improves the resilience of dynamics by adding self-feedback loops to certain nodes of the system and its objective is to maximize the trace of controllability Gramian. The Stackelberg equilibrium of the game is studied with the defender as the game leader. When the underlying network topology is a tree and the defender can select only one node, we show that the optimal strategy of the defender is determined by a specific distance-based network centrality measure, called network's f-center. In addition, we show that the degree-based centralities solutions may lead to undesirable payoffs for the defender. At the end, we discuss the case of multiple attack and defense nodes on general graphs.
17.	Proskurnikov, Anton V., et al. (författare) A simple positive state observer for multidimensional Goodwin's oscillator 2019 Ingår i: Proc. 17th European Control Conference. - : IEEE. - 9783907144008 ; , s. 1671-1676 Konferensbidrag (refereegranskat)
18.	Rantzer, Anders (författare) Realizability and internal model control on networks 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 3475-3477 Konferensbidrag (refereegranskat)abstract It is proved that network realizability of controllers can be enforced without conservatism using convex constraints on the closed loop transfer function. Once a network realizable closed loop transfer matrix has been found, a corresponding controller can be implemented using a network structured version of Internal Model Control.
19.	Ruuskanen, Johan, et al. (författare) Event-Based State Estimation Using the Auxiliary Particle Filter 2019 Ingår i: 2019 European Control Conference (ECC). - 9783907144008 Konferensbidrag (refereegranskat)abstract Event-based sampling provides a way of lowering the resource utilization in sensing and communication applications. By sending a sample only when some triggering condition is fulfilled, we can ensure that the transmitted samples actually carry innovation. However, in an event-based system, the state estimation problem becomes complicated, as the information of not receiving a measurement must be taken into consideration. Recent research has examined the feasibility of using particle filters for solving the event-based state estimation problem. To the best of our knowledge, only the simple bootstrap particle filter has so far been considered in this setting. We argue that, as this filter does not fully utilize the current measurement, it is not well suited for state estimation in event-based systems.We propose an extension to the auxiliary particle filter for systems with event-based measurements, in which certain existing techniques for finding an approximation of the fully adapted filter can easily be utilized. In a simulation study, we demonstrate that at new measurement events, the benefits of using the auxiliary particle filter increases when fewer measurements are being sent.
20.	Salimi, Somayeh, et al. (författare) Sequential Detection of Deception Attacks in Networked Control Systems with Watermarking 2019 Ingår i: 2019 18th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 883-890 Konferensbidrag (refereegranskat)abstract In this paper, we investigate the role of a physical watermarking signal in quickest detection of a deception attack in a scalar linear control system where the sensor measurements can be replaced by an arbitrary stationary signal generated by an attacker. By adding a random watermarking signal to the control action, the controller designs a sequential test based on a Cumulative Sum (CUSUM) method that accumulates the log-likelihood ratio of the joint distribution of the residue and the watermarking signal (under attack) and the joint distribution of the innovations and the watermarking signal under no attack. As the average detection delay in such tests is asymptotically (as the false alarm rate goes to zero) upper bounded by a quantity inversely proportional to the Kullback-Leibler divergence(KLD) measure between the two joint distributions mentioned above, we analyze the effect of the watermarking signal variance on the above KLD. We also analyze the increase in the LQG control cost due to the watermarking signal, and show that there is a tradeoff between quick detection of attacks and the penalty in the control cost. It is shown that by considering a sequential detection test based on the joint distributions of residue/innovations and the watermarking signal, as opposed to the distributions of the residue/innovations only, we can achieve a higher KLD, thus resulting in a reduced average detection delay. We also present some new structural results involving the associated KLD and its behaviour with respect to the attacker's signal power and the watermarking signal power. These somewhat non-intuitive structural results can be used by either the attacker to choose their power to minimize the KLD, and/or by the system designer to choose its watermarking signal variance appropriately to increase the KLD. Numerical results are provided to support our claims.
21.	Stålberg, Rasmus, et al. (författare) On Robustness of Equilibria in Dynamical Transportation Networks 2019 Ingår i: 2019 18th European Control Conference (ECC). - 9783907144008 ; , s. 2209-2214 Konferensbidrag (refereegranskat)abstract With growing traffic demands, transportation networks become more and more congested and prone to disruptions. In this paper, we study how different perturbations affect the free flow equilibria, i.e., equilibria where no congestion effects are present, in transportation networks. More specifically, if and when the equilibrium of the perturbed dynamics is still in free flow. A generalized cell transmission model models the dynamics of the transportation network, and the perturbations considered are perturbations in the exogenous inflows, flow capacity drops, and perturbations in the routing, i.e., when drivers deviate from their normal route preferences. The paper also shows that social optimum assignments in traffic networks, may not be the most robust ones.
22.	Teixeira, André M.H. (författare) Data Injection Attacks against Feedforward Controllers 2019 Ingår i: 2019 18Th European Control Conference (ECC). - : IEEE. - 9783907144008 ; , s. 2233-2239 Konferensbidrag (refereegranskat)abstract This paper studies data injection attacks on disturbance measurements, which are forwarded to a feedforward controller. Fundamental limitations to the detectability of such attacks are examined, from which a class of stealthy attacks are characterized in terms of the zero dynamics of the plant and disturbance models. The impact of such attacks to the plant output and state estimates is also examined, in both cases of perfect and imperfect disturbance rejection by the feedforward controller. The analysis shows that, under perfect rejection, the impact of stealthy attacks on the plant output is exponentially decaying, while an exponentially increasing bias is induced on the state estimation error. The results are illustrated through numerical examples.
23.	Thelander Andrén, Marcus (författare) Using Radial Basis Functions to Approximate the LQG-Optimal Event-Based Sampling Policy 2019 Ingår i: 2019 18th European Control Conference (ECC). - 9783907144008 Konferensbidrag (refereegranskat)abstract A numerical method based on radial basis functions (RBF) has been developed to find the optimal event-based sampling policy in an LQG problem setting. The optimal sampling problem can be posed as a stationary partial differential equation with a free boundary, which is solved by reformulatingthe optimal RBF approximation as a linear complementarity problem (LCP). The LCP can be efficiently solved using any quadratic program solver, and we give guarantees of existence and uniqueness of the solution. The RBF method is validated numerically, and we showcase what the different types of optimal policies look like for 2D systems.
24.	Troeng, Olof, et al. (författare) Sparsity-constrained optimization of inputs to second-order systems 2019 Ingår i: 2019 18th European Control Conference, ECC 2019. - 9783907144008 ; , s. 406-410 Konferensbidrag (refereegranskat)abstract We propose an efficient algorithm, that given a strictly proper, second-order system, finds a sparse input signal so that the system's output optimally approximates a given trajectory in least-squares sense. As an illustration, we apply the algorithm to an estimation problem from medicine.

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