| 1. |
- Decuyper, Jan, et al.
(författare)
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Decoupling multivariate polynomials for nonlinear state-space models
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 3:3, s. 745-750
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Tidskriftsartikel (refereegranskat)abstract
- Multivariate polynomials are omnipresent in black-box modelling. They are praised for their flexibility and ease of manipulation yet typically fall short in terms of insight and interpretability. Hence, often an alternative representation is desired. Translating the coupled polynomials into a decoupled form, containing only univariate polynomials has hence become a popular option. In this letter, two new polynomial decoupling techniques are introduced. The features and performance of both methods are illustrated on a nonlinear state-space model identified from data of the forced Duffing oscillator.
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| 2. |
- Georgiou, T. T., et al.
(författare)
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Dynamic Relations in Sampled Processes
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 2475-1456. ; 3:1, s. 144-149
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Tidskriftsartikel (refereegranskat)abstract
- Linear dynamical relations that may exist in continuous-time, or at some natural sampling rate, are not directly discernable at reduced observational sampling rates. Indeed, at reduced rates, matricial spectral densities of vectorial time series have maximal rank and thereby cannot be used to ascertain potential dynamic relations between their entries. This hitherto undeclared source of inaccuracies appears to plague off-the-shelf identification techniques seeking remedy in hypothetical observational noise. In this letter we explain the exact relation between stochastic models at different sampling rates and show how to construct stochastic models at the finest time scale that data allows. We then point out that the correct number of dynamical dependencies can only be ascertained by considering stochastic models at this finest time scale, which in general is faster than the observational sampling rate.
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| 3. |
- Gupta, Ankit, 1988, et al.
(författare)
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Full-complexity characterization of control-invariant domains for systems with uncertain parameter dependence
- 2019
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 3:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- This letter proposes an algorithm to find a robust control invariant (RCI) set of desired complexity and the associated linear, state-feedback control law. The candidate RCI set is restricted to be symmetric around the origin. The algorithm is applicable to rational parameter dependent systems with bounded additive disturbance. The system constraints are framed as simple affine inequalities whereas the invariance condition as a set of sufficient LMI conditions. The proposed iterative algorithm is guaranteed to be recursively feasible and converge to some stationary point.
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| 4. |
- Hashimoto, K., et al.
(författare)
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A Symbolic Approach to the Self-Triggered Design for Networked Control Systems
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 3:4, s. 1050-1055
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we investigate novel self-triggered controllers for nonlinear control systems with reachability and safety specifications. To synthesize the self-triggered controller, we leverage the notion of symbolic models, or abstractions, which represent abstracted expressions of control systems. The symbolic models will be constructed through the concepts of approximate alternating simulation relations, based on which, and by employing a reachability game, the self-triggered controller is synthesized. We illustrate the effectiveness of the proposed approach through numerical simulations.
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| 5. |
- Knorn, Steffi, et al.
(författare)
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Effects of jamming attacks on a control system with energy harvesting
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 3:4, s. 829-834
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Tidskriftsartikel (refereegranskat)abstract
- We consider the problem of control and remote state estimation with battery constraints and energy harvesting at the sensor (transmitter) under DoS/jamming attacks. We derive the optimal non-causal energy allocation policy that depends on current properties of the channel and on future energy usage. The performance of this policy is analyzed under jamming attacks on the wireless channel, in which the assumed and the true channel gains differ, and we show that the resulting control cost is not monotonic with respect to the assumed channel gain used in the transmission policy. Additionally, we show that, in case there exists a stabilizing policy, then the optimal causal policy ensures stability of the estimation process. The results were illustrated for non-causal and causal energy allocation policies under different jamming attacks.
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| 6. |
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| 7. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Multi-Agent Systems under Conflicting Local Signal Temporal Logic Tasks
- 2019
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Ingår i: IEEE Control Systems Letters. - : IEEE Institute of Electrical and Electronics Engineers Inc.. - 2475-1456. ; 3:3, s. 757-762
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the recent interest in cyber-physical and interconnected autonomous systems, we study the problem of dynamically coupled multi-agent systems under conflicting local signal temporal logic (STL) tasks. Each agent is assigned a local STL task regardless of the tasks that the other agents are assigned to. Such a task may be dependent, i.e., the satisfaction of the task may depend on the behavior of more than one agent, so that the satisfaction of the conjunction of all local tasks may be conflicting. We propose a hybrid feedback control strategy using time-varying control barrier functions. Our control strategy finds least violating solutions in the aforementioned conflicting situations based on a suitable robustness notion and by initiating collaboration among agents.
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| 8. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Multi-Agent Systemsunder Conflicting Local Signal Temporal LogicTasks
- 2019
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Ingår i: IEEE LCSS Letters. - 2475-1456.
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Tidskriftsartikel (refereegranskat)abstract
- Abstract—Motivated by the recent interest in cyber-physicaland interconnected autonomous systems, we study the problemof dynamically coupled multi-agent systems under conflictinglocal signal temporal logic tasks. Each agent is assigned a localsignal temporal logic task regardless of the tasks that the otheragents are assigned to. Such a task may be dependent, i.e., thesatisfaction of the task may depend on the behavior of more thanone agent, so that the satisfaction of the conjunction of all localtasks may be conflicting. We propose a hybrid feedback controlstrategy using time-varying control barrier functions. Our controlstrategy finds least violating solutions in the aforementionedconflicting situations based on a suitable robustness notion andby initiating collaboration among agents.
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| 9. |
- Lindemann, Lars, et al.
(författare)
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Control Barrier Functions for Signal Temporal Logic Tasks
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 3:1, s. 96-101
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Tidskriftsartikel (refereegranskat)abstract
- The need for computationally-efficient control methods of dynamical systems under temporal logic tasks has recently become more apparent. Existing methods are computationally demanding and hence often not applicable in practice. Especially with respect to multi-robot systems, these methods do not scale computationally. In this letter, we propose a framework that is based on control barrier functions and signal temporal logic. In particular, time-varying control barrier functions are considered where the temporal properties are used to satisfy signal temporal logic tasks. The resulting controller is given by a switching strategy between a computationally-efficient convex quadratic program and a local feedback control law.
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| 10. |
- Ljungberg, Fredrik, et al.
(författare)
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Obtaining Consistent Parameter Estimators for Second-Order Modulus Models
- 2019
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Ingår i: IEEE Control Systems Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2475-1456. ; 3:4, s. 781-786
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Tidskriftsartikel (refereegranskat)abstract
- This letter deals with the issue of obtaining consistent parameter estimators in nonlinear regression models where the regressors are second-order modulus functions, which is a structure that is often used in models of marine vessels. It is shown that the accuracy of an instrumental variable estimator can be improved by conducting experiments where the input signal has a static offset of sufficient amplitude and the instruments are forced to have zero mean. The proposed method is then evaluated in a simulation example.
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