| 1. |
- Altafini, Claudio, et al.
(författare)
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Achieving unanimous opinions in signed social networks
- 2014
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Ingår i: Control Conference (ECC), 2014 European. - : IEEE. - 9783952426913 ; , s. 184-189
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Konferensbidrag (refereegranskat)abstract
- Being able to predict the outcome of an opinion forming process is an important problem in social network theory. However, even for linear dynamics, this becomes a difficult task as soon as non-cooperative interactions are taken into account. Such interactions are naturally modeled as negative weights on the adjacency matrix of the social network. In this paper we show how the Perron-Frobenius theorem can be used for this task also beyond its standard formulation for cooperative systems. In particular we show how it is possible to associate the achievement of unanimous opinions with the existence of invariant cones properly contained in the positive orthant. These cases correspond to signed adjacency matrices having the eventual positivity property, i.e., such that in sufficiently high powers all negative entries have disappeared. More generally, we show how for social networks the achievement of a, possibily non-unanimous, opinion can be associated to the existence of an invariant cone fully contained in one of the orthants of ℝless thansupgreater thannless than/supgreater than.
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| 2. |
- Besselink, Bart, et al.
(författare)
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Model reduction of networked passive systems through clustering
- 2014
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Ingår i: 2014 European Control Conference, ECC 2014. - : IEEE. - 9783952426913 ; , s. 1069-1074
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Konferensbidrag (refereegranskat)abstract
- In this paper, a model reduction procedure for a network of interconnected identical passive subsystems is presented. Here, rather than performing model reduction on the subsystems, adjacent subsystems are clustered, leading to a reduced-order networked system that allows for a convenient physical interpretation. The identification of the subsystems to be clustered is performed through controllability and observability analysis of an associated edge system and it is shown that the property of synchronization (i.e., the convergence of trajectories of the subsystems to each other) is preserved during reduction. The results are illustrated by means of an example.
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| 3. |
- Charalambous, Charalambos D., et al.
(författare)
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Team Optimality Conditions of Differential Decision Systems with Nonclasssical Information Structures
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 2851-2856
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Konferensbidrag (refereegranskat)abstract
- We derive team optimality conditions for differential decision systems with nonclassical information structures. The necessary conditions of optimality are given in terms of Hamiltonian system of equations consisting of a coupled backward and forward differential equations and a Hamiltonian projected onto the subspace generated by the information structures. Under certain global convexity conditions it is shown that person-by-person optimality implies team optimality.
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| 4. |
- Dadhich, Siddharth, et al.
(författare)
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Analysis and control of an extended Quadruple tank process
- 2014
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Ingår i: 2014 European Control Conference (ECC), June 24-27, 2014. Strasbourg, France. - Piscataway, NJ : IEEE Communications Society. - 9783952426913 ; , s. 838-843
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Konferensbidrag (refereegranskat)abstract
- An extension to the standard Quadruple tank process is proposed and analyzed. It is shown that the extended setup provides an improved platform for experimental and educational studies of MIMO control systems. Based on dynamic models for the process a control configuration selection is performed and both decentralized and decoupling control schemes are designed and tested. Moreover sparse IMC controllers have been evaluated against a decentralized control scheme for improvement in the stochastic performance. It is shown how a performance assessment method based on the FCOR algorithm can be used to find the optimal tuning of the IMC controller. It can be concluded that the proposed extension to the quadruple tank process is useful for benchmark and educational purposes.
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| 5. |
- Ebadat, Afrooz, et al.
(författare)
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Application Set Approximation in Optimal Input Design for Model Predictive Control
- 2014
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Ingår i: 2014 European Control Conference (ECC). - 9783952426913 ; , s. 744-749
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Konferensbidrag (refereegranskat)abstract
- This contribution considers one central aspect of experiment design in system identification, namely application set approximation. When a control design is based on an estimated model, the achievable performance is related to the quality of the estimate. The degradation in control performance due to plant-modeling missmatch is quantified by an application cost function. A convex approximation of the set of models that satisfy the control specification is typically required in optimal input design. The standard approach is to use a quadratic approximation of the application cost function, where the main computational effort is to find the corresponding Hessian matrix. Our main contribution is an alternative approach for this problem, which uses the structure of the underlying optimal control problem to considerably reduce the computations needed to find the application set. This technique allows the use of applications oriented input design for MPC on much more complex plants. The approach is numerically evaluated on a distillation control problem.
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| 6. |
- Eriksson, Daniel, 1984-, et al.
(författare)
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Sequential Residual Generator Selection for Fault Detection
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 932-937
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Konferensbidrag (refereegranskat)abstract
- Structural methods in model-based fault diagnosis applications are simple and efficient tools for finding candidates for residual generation. However, the structural methods do not take model uncertainties and information about fault behavior into consideration. This may result in selecting residual generators with bad performance to be included in the diagnosis system. By using the Kullback-Leibler divergence, the performance of different residual generators can be compared to find the best one. With the ability to quantify diagnostic performance, the design of residual generators can be optimized by, for example, combining several residual generators such that the diagnostic performance is maximized. The proposed method for residual generation selection is applied to a water tank system to show that the achieved residual performance is improved compared to only use a structural method.
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| 7. |
- Forgione, M., et al.
(författare)
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Experiment design for parameter estimation in nonlinear systems based on multilevel excitation
- 2014
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Ingår i: 2014 European Control Conference, ECC 2014. - 9783952426913 ; , s. 25-30
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Konferensbidrag (refereegranskat)abstract
- An experiment design procedure for parameter estimation in nonlinear dynamical systems is presented in this paper. The input to the system is designed in such a way that the information content of the data, as measured by a scalar function of the information matrix, is maximized. By restricting the input to a finite number of possible levels, the experiment design problem is formulated as a convex optimization problem which can be solved efficiently. The method is applied to a Continuous Stirred Tank Reactor in a simulation study. The parameter estimation based on the input signal obtained in our procedure is shown to outperform the one based on random binary signals.
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| 8. |
- Godoy, B. I., et al.
(författare)
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A novel input design approach for systems with quantized output data
- 2014
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Ingår i: 2014 European Control Conference, ECC. - : IEEE. - 9783952426913 ; , s. 1049-1054
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Konferensbidrag (refereegranskat)abstract
- In this paper, we explore the problem of input design for systems with quantized measurements. For the input design problem, we calculate and optimize a function of the Fisher Information Matrix (FIM). The calculation of the FIM is greatly simplified by using known relationships of the derivative of the likelihood function, and the auxiliary function arising from the Expectation Maximization (EM) algorithm. To optimize the FIM, we design an experiment using a recently published method based on graph theory. A numerical example shows that the proposed experiment can be successfully used in quantized systems.
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| 9. |
- Hjalmarsson, Håkan, et al.
(författare)
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Model Structure Selection - An Update
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 2382-2385
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Konferensbidrag (refereegranskat)abstract
- While the topic has a long history in research, model structure selection is still one of the more challenging problems in system identification. In this tutorial we focus on impulse response modelling, and link classical techniques such as hypothesis testing and information criteria (e.g. AIC) to recent model estimation approaches, including regularisation. We discuss the problem from minimum mean-square error and maximum-likelihood perspectives.
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| 10. |
- Jansson, Daniel, et al.
(författare)
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Volterra modeling of the smooth pursuit system with application to motor symptoms characterization in Parkinson's disease
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 1856-1861
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Konferensbidrag (refereegranskat)abstract
- A new way of modeling the Smooth Pursuit System (SPS) in humans by means of Volterra series expansion is suggested and utilized together with Gaussian Mixture Models (GMMs) to successfully distinguish between healthy controls and Parkinson patients based on their eye movements. To obtain parsimonious Volterra models, orthonormal function expansion of the Volterra kernels in Laguerre functions with the coefficients estimated by SParse Iterative Covariance-based Estimation (SPICE) is used. A combination of these two techniques is shown to greatly reduce the number of model parameters without significant performance loss. In fact, the resulting models outperform the Wiener models of previous research despite the significantly lower number of model parameters. Furthermore, the results of this study indicate that the nonlinearity of the system is likely to be dynamical in nature, rather than static which was previously presumed. The difference between the SPS in healthy controls and Parkinson patients is shown to lie largely in the higher order dynamics of the system. Finally, without the model reduction provided by SPICE, the GMM estimation fails, rendering the model unable to separate healthy controls from Parkinson patients.
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| 11. |
- Katselis, Dimitrios, et al.
(författare)
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Least Squares End Performance Experiment Design in Multicarrier Systems : The Sparse Preamble Case
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 13-18
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Konferensbidrag (refereegranskat)abstract
- In this paper, the problem of experiment design for the task of channel identification in cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM) systems is revisited. So far, the optimal input sequences for least squares (LS) channel identification with respect to minimizing the channel mean square error (MSE) under an input energy constraint have been derived. Here, we investigate the same problem for the LS channel estimator, but when the design takes into account an end performance metric of interest, namely, the symbol estimate MSE. Based on some convex approximations, we verify that optimal sparse preambles, i.e, input vectors employing as many pilots as the channel length, for LS channel estimation in its classical context are near optimal in the aforementioned application-oriented context for the symbol estimate MSE.
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| 12. |
- Kulcsár, Balázs Adam, 1975, et al.
(författare)
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Impulse response parameter based internal model control for discrete-time LPV systems
- 2014
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Ingår i: 13th European Control Conference, ECC 2014, Strasbourg Convention and Exhibition Center, Place de Bordeaux, Strasbourg, France, 24-27 June 2014. - 9783952426913 ; , s. 424-429
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel impulse response parameter based solution for internal model control (IMC) within the linear parameter varying framework. First, based on a discrete-time state-space representation, a finite horizon vector autoregressive model with exogenous disturbance (VARX) is obtained to describe the I/O relationship of an affine LPV plant. In this paper, inversion of the VARX model w.r.t. control input directly leads to a IMC law where analytic solution can be derived for unconstrained and optimal reference tracking error minimization. When the bias term in the finite horizon I/O predictor is neglected, asymptotic properties of closed-loop IMC is analyzed. The VARX parameters of the I/O LPV model can be factorized into a scheduling dependent data matrix and a sequence of constant impulse response parameters (IRPs). The latter part can consistently be identified from data as a single least-squares problem. Without the need to build or identify an LPV state-space model, this methodology is able to address IMC tracking error minimization by using IRPs. The viability of the proposed method is numerically tested in simulation environment.
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| 13. |
- Köroglu, Hakan, 1971, et al.
(författare)
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State Feedback Synthesis for Homogenous Platoons under the Leader and Predecessor Following Scheme
- 2014
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Ingår i: Proceedings of European Control Conference, June 24-27, 2014, Strasbourg, France. - 9783952426913 ; , s. 2655-2660
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Konferensbidrag (refereegranskat)abstract
- Synthesis of state-feedback controllers is considered for a homogenous platoon operating under the leader and predecessor following scheme. The problem is formulated as a multi-objective H-infinity type synthesis. The performance specifications are shaped by the string stability objective and prevention of extensive control effort, as well as by the concerns about the communication problems with the leader. Sufficient LMI conditions are then provided for the synthesis of common statefeedback gains. Some aspects of the developed approach are illustrated in the longitudinal control of a vehicle platoon.
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| 14. |
- Larsson, Viktor, 1984, et al.
(författare)
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Cubic Spline Approximations of the Dynamic Programming Cost-to-go in HEV Energy Management Problems
- 2014
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Ingår i: 13th European Control Conference, ECC 2014; Strasbourg Convention and Exhibition CenterPlace de BordeauxStrasbourg; France; 24 June 2014 through 27 June 2014. - 9783952426913 ; , s. 1699-1704
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Konferensbidrag (refereegranskat)abstract
- The energy management problem of a hybridelectric vehicle (HEV) is a non-linear and mixed integeroptimization problem. The problem can be solved with DynamicProgramming (DP), but the algorithm requires the problem tobe gridded in time, states and control signals. To ensure a highaccuracy of the solution the grid must be dense, meaning thatthe cost-to-go can require several megabytes of memory. Thescope of this paper is therefore twofold. The first topic is asensitivity study, where the effect of a sparsely gridded state isinvestigated, both for an HEV and a plug-in HEV (PHEV). Thestudy shows that it is possible to use a sparse grid for an HEV,but not for a PHEV. The second topic and the main contributionis a method to approximate the DP cost-to-go with cubic splines.The results indicate that it is possible to use only a few splines,if the knot points are determined based on the characteristicsof the cost-to-go. Thereby it is possible to significantly reducethe memory requirements, without any noticeable increase insimulated fuel consumption.
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| 15. |
- Liu, Kun, 1982-, et al.
(författare)
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Discrete-time Network-based Control under Try-Once-Discard Protocol and Actuator Constraints
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 442-447
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the solution bounds for discrete-time Networked Control Systems (NCSs) via delay-dependent Lyapunov-Krasovskii methods. Solution bounds are widely used for systems with input saturation caused by actuator saturation or by the quantizers with saturation. A time-delay approach was introduced recently for continuous-time NCS under a weighted Try-Once-Discard (TOD) protocol in [12], where actuator saturation was not taken into account. In the present paper, we develop the time-delay approach for linear (probably, uncertain) discrete-time NCS under the weighted TOD protocol in the presence of actuator saturation. A novel Lyapunov-based method is presented for finding the domain of attraction. Polytopic uncertainties in the system model can be easily included in our analysis. The efficiency of the time-delay approach is illustrated on the example of a cart-pendulum system.
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| 16. |
- Liu, Kun, et al.
(författare)
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Networked Control Systems : A Time-Delay Approach
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 1434-1439
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Konferensbidrag (refereegranskat)abstract
- Networked control systems (NCSs) are spatially distributed systems for which the communication between sensors, actuators, and controllers is supported by a shared communication network. This paper gives an overview of the time-delay approach to NCSs. Firstly, the modelling on the Networked Control Systems (NCSs) with one sensor node is recalled. Then, for the NCSs with distributed sensor nodes and Round-Robin (RR) protocol, the closed-loop system can be presented as a switched system with multiple ordered delays. Next, a continuous-time hybrid system model for the closed-loop system, where time-varying delays appear in the dynamics and in the reset equations, is introduced to NCSs under RR and Try-Once-Discard (TOD) protocols. Lastly, the hybrid system modelling for the closed-loop system is extended to the discrete-time case. Differently from other approaches to NCSs in the presence of scheduling protocols (in the frameworks of hybrid and discrete-time systems), the time-delay approach allows the communication delays to be greater than the sampling intervals.
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| 17. |
- Nilsson, Magnus, et al.
(författare)
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Assessing the potential of prediction in energy management for ancillaries in heavy-duty trucks
- 2014
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Ingår i: 2014 European Control Conference, ECC 2014. - : Institute of Electrical and Electronics Engineers Inc.. - 9783952426913 ; , s. 1693-1698
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Konferensbidrag (refereegranskat)abstract
- The degree of importance of prediction in the control of ancillary systems for conventional heavy-duty trucks is investigated, with focus on fuel economy. An optimal control law that utilizes prediction is compared with a suboptimal causal control law. The incentive for this investigation is that the suboptimal control law is less complex to develop and implement for the considered system. The results are not general since only a limited amount of ancillary systems have been modeled, only two different drive cycles have been evaluated and simplified mathematical component models for a specific test truck have been used in the optimization problem. Nevertheless, preliminary results from this investigation indicate that simple suboptimal control laws can yield close to the same improvements in fuel efficiency as a predictive controller, when compared to a baseline control law. Tuning complexity is expected to rise when more ancillaries are included in the energy management problem. This can be a valid argument to incorporate prediction in future work.
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| 18. |
- Potters, M. G., et al.
(författare)
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Optimal Experiment Design in Closed Loop with Unknown, Nonlinear and Implicit Controllers using Stealth Identification
- 2014
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Ingår i: 2014 European Control Conference, ECC 2014. - : IEEE. - 9783952426913 ; , s. 726-731
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Konferensbidrag (refereegranskat)abstract
- We present a novel optimal experiment design method that is applicable to linear time-invariant systems regulated by unknown, nonlinear and implicitly-defined controllers. Current methods require an explicit expression for the controller in order to construct the optimal excitation spectrum. Consequently, these are limited to linearly-controlled systems. The identification scheme suggested in this paper circumvents the aforementioned requirement by ensuring that the excitation signal remains unnoticed by the controller, i.e., the identification data is gathered in an open-loop fashion. Our theoretical analysis is complemented with a numerical study on a six-parameter, single-input single-output linear system controlled by an MPC. We find that our method generates least-costly excitation signals which deliver identified models that lie close to the true system whilst honoring quality constraints, validating the novel optimal experiment design framework.
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| 19. |
- Sayyaddelshad, Saleh, et al.
(författare)
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Observer design for a class of nonlinear systems subject to unknown inputs
- 2014
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Ingår i: 2014 European Control Conference (ECC), June 24-27, 2014. Strasbourg, France. - Piscataway, NJ : IEEE Communications Society. - 9783952426913 ; , s. 970-974
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Konferensbidrag (refereegranskat)abstract
- We consider a novel method to design an observer for a class of nonlinear discrete-time systems with unknown inputs. Based on Lyapunov functional, we derive a sufficient condition for existence of the designed observer which requires solving a nonlinear matrix inequality. In light of linear algebra, the achieved condition will be formulated in terms of linear matrix inequality (LMI) that can be solved by popular methods easily. Compared to recent researches, the developed approach shows a significant better performance than other techniques previously published in literature and is less conservative in terms of Lipschitz constant. Finally, the proposed observer is illustrated by implementing the proposed method on a single- link flexible manipulator and the results are compared to some recent similar researches in terms of performance and conservativeness.
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| 20. |
- Sou, Kin Cheong, 1979, et al.
(författare)
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Nonserial Dynamic Programming with Applications in Smart Home Appliances Scheduling - Part I : Precedence Graph Simplification
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 1643-1648
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Konferensbidrag (refereegranskat)abstract
- In this and a companion paper a dynamic programming (DP) approach to solve a smart home appliances scheduling problem is considered. The challenge with solving the scheduling problem is the coupling of decision variables due to some time precedence constraints. In general, the system of precedence constraints may contain redundant constraints that offer opportunities for simplification. This simplification is desirable for reducing the computation effort of the nonserial DP procedure presented in the companion paper (i.e., Part II). The current paper establishes the uniqueness of the maximum set of redundant constraints and its polynomial-time solvability with optimality guarantee, under the sufficient and necessary condition that the precedence graph (a graph representation of the precedence constraints system) does not contain any cycle with nonnegative weight. A numerical case study indicates the efficiency of the proposed simplification algorithm versus the brute-force enumerative search. Besides helping to reduce the computation effort in the DP procedure described in the companion paper, the algorithm in the current paper solves a generalization of a precedence graph simplification problem arising from application areas such as parallel computing.
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| 21. |
- Sou, Kin Cheong, 1979, et al.
(författare)
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Nonserial Dynamic Programming with Applications in Smart Home Appliances Scheduling - Part II : Nonserial Dynamic Programming
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 1663-1668
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Konferensbidrag (refereegranskat)abstract
- In this paper a dynamic programming (DP) solution approach to a nonconvex resource allocation problem (RAP) is presented. The problem in this paper generalizes the smart home appliances scheduling problem introduced in the companion paper (i.e., Part I). The computation difficulty with solving the RAP depends on the decision variable coupling, which can be described by an interaction graph. This paper proposes a DP algorithm to solve the RAP in the special setting where the interaction graph is a tree. This extends the applicability result of DP to RAP beyond the standard serial case where the interaction graph is a line. The extension of the result is achieved by establishing that even in the tree case DP computation effort is polynomial in the number of decision variables. For RAP in its general form, this paper proposes a modification to the nonserial DP procedure originally introduced by Bertele and Brioschi. Contrary to that of the previous method, the computation effort of the proposed method can be characterized by a well-known minimum feedback vertex set problem. Case studies on known examples indicate that both nonserial DP methods are similarly efficient.
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| 22. |
- Trollberg, Olle, et al.
(författare)
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On the Convergence Rate of Extremum Seeking Control
- 2014
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Ingår i: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 2115-2120
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Konferensbidrag (refereegranskat)abstract
- Extremum seeking control (ESC) is an adaptive optimization method originally proposed for static systems but later extended to Hammestein/Wiener-like systems and more recently also to more general dynamic systems. In the latter case the focus has been on proving convergence and stability of solutions in the vicinity of the optimum. The proofs are in general based on combining asymptotic methods like singular perturbations and averaging, which leads to a three timescale factorization of the problem where the control action is forced to be several orders of magnitude slower than the openloop dynamics of the plant. This implies that the convergence rate will be impractically slow for many applications. In this paper, we employ Tikhonov theory and averaging to study the rate of convergence while employing only two time-scales. In particular, the analysis places no restrictions on the rate of the gradient estimation and therefore allows for significantly faster control compared to the conventional approach. The plant is approximated as a linear parameter varying system (LPV) which is then used to derive a global quantitative expression for the convergence rate in terms of the ESC parameters and the frequency response of the LPV plant. For Hammerstein/Wienerlike systems, the derived expression is used to show that the ESC loop behaves like a gradient descent method while it has a more complex behavior in the general case. Finally, an isothermal biochemical reactor is used to illustrate the results and some of the difficulties which might arise in the general case, such as the fact that the convergence rate can be low locally even if the gradient of the cost function is large.
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| 23. |
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| 24. |
- Zanon, Mario, 1985, et al.
(författare)
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Control of Dual-Airfoil Airborne Wind Energy Systems Based on Nonlinear MPC and MHE
- 2014
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Ingår i: European Control Conference. - 9783952426913
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Konferensbidrag (refereegranskat)abstract
- Abstract:Airborne Wind Energy (AWE) systems generate energy by flying a tethered airfoil across the wind flow at a high velocity. Tethered flight is a fast, strongly nonlinear, unstable and constrained process, motivating control approaches based on fast Nonlinear Model Predictive Control (NMPC) and state estimation approaches based on Moving Horizon Estimation (MHE). Dual-Airfoil AWE systems, i.e. systems with two airfoils attached to a Y-shaped tether have been shown to be more effective than systems based on a single airfoil. This paper proposes a control scheme for a dual-airfoil AWE system based on NMPC and MHE and studies its performance in a realistic scenario based on state-of-the-art turbulence models.
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| 25. |
- Zhusubaliyev, Zhanybai T., et al.
(författare)
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Time Delay Induced Multistability and Complex Dynamics in an Impulsive Model of Endocrine Regulation
- 2014
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Ingår i: 2014 European Control Conference (ECC). - 9783952426913 ; , s. 2304-2309
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Konferensbidrag (refereegranskat)abstract
- The effects caused by the introduction of a time delay in the continuous part of an impulsive (hybrid) model of endocrine feedback regulation are studied by bifurcation analysis. It is concluded that larger (in some well-defined sense) values of the time delay give rise to a broad range of nonlinear dynamics phenomena that have not been observed for the smaller ones. Among such behaviors are e.g. border-collision bifurcations, bistability, and quasiperiodic solutions. The reason for the more complex dynamics exhibited by the model in this case is a discontinuity of the Jacobian of a discrete mapping describing the propagation of the model dynamics from one firing of the impulsive feedback to another.
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