| 1. |
- Ahmadi, Seyed Alireza, et al.
(författare)
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Towards more efficient building energy management systems
- 2012
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Ingår i: Proceedings - 2012 7th International Conference on Knowledge, Information and Creativity Support Systems, KICSS 2012. - : IEEE. - 9780769548616 ; , s. 118-125
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Konferensbidrag (refereegranskat)abstract
- As a first step towards developing efficient building energy management techniques, in this paper, we first study the energy consumption patterns of heating, ventilation and cooling (HVAC) systems across the KTH Royal Institute of Technology campus and we identify some possible areas where energy consumption can be made less wasteful. Later, we describe a test-bed where wireless sensor networks are used to collect data and eventually control the HVAC system in a distributed way. We present some of the data, temperature, humidity, and CO2 measurements, that are collected by the aforementioned network and compare them with the measurements collected by the legacy sensors already in place. In the end we present a preliminary result on modelling the dynamics of the temperature, humidity, and CO2 using the data gather by the sensor network. We check the validity of the model via comparing the out put of the system with measured data. As a future work we identify the possibility of using the models obtained here for model based control, and fault detection and isolation techniques.
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| 2. |
- Altaf, Faisal, et al.
(författare)
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Wireless event-triggered controller for a 3D tower crane lab process
- 2011
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Ingår i: 2011 19th Mediterranean Conference on Control and Automation, MED 2011. - 9781457701252 - 9781457701245 ; , s. 994-1001
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Konferensbidrag (refereegranskat)abstract
- This paper studies the design and real-time implementation of an event-triggered controller for a nonlinear 3D tower crane where the communication between the controller and the actuators is performed over a low-power wireless network. A flexible Event-Generation Circuit (EGC) is proposed in order to implement event-driven controllers for Networked Control Systems. Furthermore, a detailed experimental analysis on the performance of the event-triggered controller and the influence of packet losses on the transmitted actuation messages are presented. The results show that the event-triggered controllers in networked control systems are able to maintain the same level of performance as compared to periodic controllers, while increasing the sensors/actuators lifetime by reducing network bandwidth utilization.
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| 3. |
- Andersson, G., et al.
(författare)
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Cyber-security of SCADA systems
- 2012
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Ingår i: 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012. - : IEEE. - 9781457721588 ; , s. 6175543-
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Konferensbidrag (refereegranskat)abstract
- After a general introduction of the VIKING EU FP7 project two specific cyber-attack mechanisms, which have been analyzed in the VIKING project, will be discussed in more detail. Firstly an attack and its consequences on the Automatic Generation Control (AGC) in a power system are investigated, and secondly the cyber security of State Estimators in SCADA systems is scrutinized.
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| 4. |
- Andreasson, Martin, et al.
(författare)
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Correlated Failures of Power Systems : Analysis of the Nordic Grid
- 2011
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Ingår i: Preprints of Workshop on Foundations of Dependable and Secure Cyber-Physical Systems.
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Konferensbidrag (refereegranskat)abstract
- In this work we have analyzed the effectsof correlated failures of power lines on the total systemload shed. The total system load shed is determined bysolving the optimal load shedding problem, which is thesystem operator’s best response to a system failure.We haveintroduced a Monte Carlo based simulation framework forestimating the statistics of the system load shed as a functionof stochastic network parameters, and provide explicitguarantees on the sampling accuracy. This framework hasbeen applied to a 470 bus model of the Nordic power systemand a correlated Bernoulli failure model. It has been foundthat increased correlations between Bernoulli failures ofpower lines can dramatically increase the expected valueas well as the variance of the system load shed.
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| 5. |
- Andreasson, Martin, et al.
(författare)
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Distributed Control of Networked Dynamical Systems : Static Feedback, Integral Action and Consensus
- 2014
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 59:7, s. 1750-1764
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Tidskriftsartikel (refereegranskat)abstract
- This paper analyzes distributed control protocols for first- and second-order networked dynamical systems. We propose a class of nonlinear consensus controllers where the input of each agent can be written as a product of a nonlinear gain, and a sum of nonlinear interaction functions. By using integral Lyapunov functions, we prove the stability of the proposed control protocols, and explicitly characterize the equilibrium set. We also propose a distributed proportional-integral (PI) controller for networked dynamical systems. The PI controllers successfully attenuate constant disturbances in the network. We prove that agents with single-integrator dynamics are stable for any integral gain, and give an explicit tight upper bound on the integral gain for when the system is stable for agents with double-integrator dynamics. Throughout the paper we highlight some possible applications of the proposed controllers by realistic simulations of autonomous satellites, power systems and building temperature control.
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| 6. |
- Andreasson, Martin, et al.
(författare)
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Distributed integral action : stability analysis and frequency control of power systems
- 2012
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Ingår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC). - : IEEE. - 9781467320665 ; , s. 2077-2083
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Konferensbidrag (refereegranskat)abstract
- This paper analyzes distributed proportional-integral controllers. We prove that integral action can be successfully applied to consensus algorithms, where attenuation of static disturbances is achieved. These control algorithms are applied to decentralized frequency control of electrical power systems. We show that the proposed algorithm can attenuate step disturbances of power loads. We provide simulations of the proposed control algorithm on the IEEE 30 bus test system that demonstrate its efficiency.
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| 7. |
- Araujo, Jose, et al.
(författare)
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Control over a Hybrid MAC Wireless Network
- 2010
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Ingår i: 2010 IEEE 1ST INTERNATIONAL CONFERENCE ON SMART GRID COMMUNICATIONS. ; , s. 197-202
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Konferensbidrag (refereegranskat)abstract
- Wireless Sensor Networks and Control Systems are an essential part of the Smart Grid. We consider the problem of performing control over large complex networked systems with packet drops. More specifically, we are interested in improving the performance of the regulation of control loops when the communication is made over low-cost wireless networks. In control over wireless networks it is common to use Contention-Free (CF) schemes where no losses occur with the price of low scalability and complicated scheduling policies. In this work we propose a hybrid MAC and control architecture, where a small number of control loops with high demand of attention are scheduled in a CF scheme and well regulated loops are scheduled in a lossy, asynchronous and highly scalable, Contention-Access (CA) scheme. We model and analyze the performance of such system with Markov Jump Linear System (MJLS) tools and compare it with other architecture types. Performance is evaluated using a quadratic cost function of the state.
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| 8. |
- Besselink, Bart, et al.
(författare)
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Controllability of a class of networked passive linear systems
- 2013
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Ingår i: Proceedings of the 52nd IEEE Conference on Decision and Control, Florence, Italy. - : IEEE conference proceedings. ; , s. 4901-4906
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Konferensbidrag (refereegranskat)abstract
- In this paper, controllability properties of networks of diffusively coupled linear systems are considered through the controllability Gramian. For a class of passive linear systems, it is shown that the controllability Gramian can be decomposed into two parts. The first part is related to the dynamics of the individual systems whereas the second part is dependent only on the interconnection topology, allowing for a clear interpretation and efficient computation of controllability properties for a class of networked systems. Moreover, a relation between symmetries in the interconnection topology and controllability is given. The results are illustrated by an example.
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| 9. |
- 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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| 10. |
- Farokhi, Farhad, 1987-, et al.
(författare)
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Complexity Reduction for Parameter-Dependent Linear Systems
- 2013
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Ingår i: 2013 American Control Conference (ACC). - : American Automatic Control Council. - 9781479901777 ; , s. 2624-2630
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Konferensbidrag (refereegranskat)abstract
- We present a complexity reduction algorithm for a family of parameter-dependent linear systems when the system parameters belong to a compact semi-algebraic set. This algorithm potentially describes the underlying dynamical system with fewer parameters or state variables. To do so, it minimizes the distance (i.e., $H_\infty$-norm of the difference) between the original system and its reduced version. We present a sub-optimal solution to this problem using sum-of-squares optimization methods. We present the results for both continuous-time and discrete-time systems. Lastly, we illustrate the applicability of our proposed algorithm on numerical examples.
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