| 1. |
- Bahraini, Masoud, 1991, et al.
(author)
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Communication Demand Minimization for Perturbed Networked Control Systems with Coupled Constraints
- 2023
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In: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; , s. 3468-3473
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Conference paper (peer-reviewed)abstract
- Communication scheduling is needed when control loops of several safety-critical systems are closed through a shared communication medium. To enable schedulability, control for each system is designed primarily to minimize its communication demand. In this paper, we study communication demand minimization for a class of perturbed multi-agent networked control systems with a shared communication medium and subject to input and coupled state constraints. First, a framework to design communication schedule and control is recalled such that state and input constraints are satisfied under no coupling assumption. Then, a heuristic method is proposed to decouple state constraints such that the overall communication demand of the systems is minimized. Effectiveness of the proposed results are illustrated through a numerical example.
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| 2. |
- Bahraini, Masoud, 1991
(author)
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Control and Communication-Schedule Co-design For Networked Control Systems
- 2023
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Doctoral thesis (other academic/artistic)abstract
- In a networked control system (NCS), the control loop is closed through a communication medium. This means that sensor measurements and/or control signals can be exchanged through a communication link. NCSs have many benefits, such as wiring reduction (elimination in the case of wireless communication), installation cost reduction, and simplification of upgrades and restructuring. However, network congestion, impairments of the wireless links (such as bandwidth limitations, packet losses, delays, and noises) may degrade system performance and even cause instability. These issues have motivated a great deal of research over the past 20 years and have given rise to a number of approaches to prevent congestion and compensate for delays and/or packet losses. An interesting class of NCSs that has not received enough attention is an NCS whose systems are uncertain and subject to state and inputs hard constraints.These hard constraints may stem from the system itself, its environment, or be proposed by the designer in order to guarantee safety or a certain performance. The contribution of this thesis is introducing a design framework that guarantees robust constraint satisfaction for a class of multi-agent NCSs with a shared communication medium that is subject to bandwidth limitation and prone to packet losses. The proposed framework is built upon reachability analysis to determine the communication demand for each system such that local constraints are satisfied and scheduling techniques to guarantee satisfaction of the communication demands. The thesis explores offline and online scheduling designs under various communication topologies, optimal control designs under state and output feedback, and scheduling and control co-design for NCSs with hard constraints.
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| 3. |
- Bahraini, Masoud, 1991, et al.
(author)
-
Optimal Control Design for Perturbed Constrained Networked Control Systems
- 2021
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In: IEEE Control Systems Letters. - 2475-1456. ; 5:2, s. 553-558
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Journal article (peer-reviewed)abstract
- This letter focuses on an optimal control design problem for a class of perturbed networked control systems where a number of systems, subject to state and input constraints, share a communication network with limited bandwidth. We first formulate an optimal control design problem with a constant feedback gain in order to minimize the communication demand for each system while guaranteeing satisfaction of state and input constraints; we show that this optimization problem is very hard to solve. Then, we formulate the same optimal control design problem with a non-constant feedback gain; we argue that this problem is less difficult and results in a lower, or equal, communication demand in comparison to the design with the constant feedback gain. We illustrate and compare these optimal control designs by a simple example.
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| 4. |
- Bahraini, Masoud, 1991, et al.
(author)
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Optimal scheduling and control for constrained multi-agent networked control systems
- 2022
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In: Optimal Control Applications and Methods. - : Wiley. - 1099-1514 .- 0143-2087. ; 43:1, s. 23-43
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Journal article (peer-reviewed)abstract
- In this paper, we study optimal control and communication schedule co-design for multi-agent networked control systems, with assuming shared parallel communication channels and uncertain constrained linear time-invariant discrete-time systems. To that end, we specify the communication demand for each system using an associated robust control invariant set and reachability analysis. We use these communication demands and invariant sets to formulate tube-based model predictive control and offline/online communication schedule co-design problems. Since the scheduling part includes an infinite dimension integer problem, we propose heuristics to find suboptimal solutions that guarantee robust constraints satisfaction and recursive feasibility. The effectiveness of our approach is illustrated through numerical simulations.
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| 5. |
- Bahraini, Masoud, 1991, et al.
(author)
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Receding-horizon robust online communication scheduling for constrained networked control systems
- 2019
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In: 2019 18th European Control Conference, ECC 2019. ; , s. 2969-2974
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Conference paper (peer-reviewed)abstract
- This paper proposes a novel online scheduling approach for perturbed Networked Control Systems (NCS) over lossy networks, subject to state and input constraints and limited network capacity. The paper shows how an online communication schedule can be found for the considered class of systems, as the solution of a constrained optimization problem, which is solved in receding horizon and is proven to be persistently feasible. The resulting online schedule is proven to preserve the system invariance w.r.t. state and input constraints. A communication scheduler is also derived for lossy networks, starting from a feasible baseline schedule calculated offline. Numerical examples are given to illustrate the proposed contributions.
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| 6. |
- Bahraini, Masoud, 1991, et al.
(author)
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Robust Control Invariance for Networked Control Systems with Output Feedback
- 2022
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In: Proceedings of the IEEE Conference on Decision and Control. - 0743-1546 .- 2576-2370. ; 2022-December, s. 7676-7681
-
Conference paper (peer-reviewed)abstract
- This paper focuses on robust output feedback design for multi-agent networked control systems with a shared communication medium, where each system is subject to state and input constraints. We first compute the communication demand for each system given constant observer and controller gains; we argue that minimization of the communication demand with respect to the control or observer gains is very hard. Then, given a constant observer gain, we compute the minimum communication demand for each system and a corresponding control policy using model predictive control; we argue that the second approach is less difficult to solve and results in a communication demand which is no larger than for a linear controller. We illustrate and compare these design methods by a numerical example.
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| 7. |
- Bahraini, Masoud, 1991, et al.
(author)
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Scheduling and Robust Invariance in Networked Control Systems
- 2022
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In: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 67:6, s. 3075-3082
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Journal article (peer-reviewed)abstract
- In Networked Control Systems (NCS), impairments of the communication channel can be disruptive to stability and performance. In this paper, we consider the problem of scheduling the access to limited communication resources for a number of decoupled systems subject to state and input constraints, whose loops need to be closed over the network. The schedule must be designed to robustly preserve the invariance property of each system, which in turn guarantees constraint satisfaction. To that end, we first focus on systematic offline scheduling design to preserve robust invariance, and afterwards on online scheduling design with the aim of improving performance and compensating for packet losses while guaranteeing recursive schedulability.
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| 8. |
- Bahraini, Masoud, 1991, et al.
(author)
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Sliding mode control revisited
- 2020
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In: Transactions of the Institute of Measurement and Control. - : SAGE Publications. - 1477-0369 .- 0142-3312. ; 42:14, s. 2698-2707
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Journal article (peer-reviewed)abstract
- Controller design for nonlinear systems in its general form is complicated and an open problem. Finding a solution to this problem becomes more complicated when unwanted terms, such as disturbance, are taken into account. To provide a robust design for a subclass of nonlinear systems, sliding mode controllers (SMCs) are used. These controllers have a systematic design procedure and can reject bounded disturbances and at the same time guarantee stability. The guaranteed stability is achieved by separating system states into two parts and assuming that the input to state stability (ISS) condition holds for internal dynamics. This condition restricts the applicability of the SMC and limits the system performance when the controller is designed based on that. In order to remove this restriction and improve the performance, the ISS condition has been relaxed in this study. The relaxation is performed by redesigning SMCs based on suggested Lyapunov functions. The proposed idea insures global asymptotic stability of the closed loop system and is used to revise different well-known SMCs such as conventional SMC, terminal SMC, non-singular terminal SMC, integral SMC, super-twisting SMC, and super-twisting integral SMC. Comparisons between conventional and revised versions are made using simulation to demonstrate excellence of the revisited controllers.
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| 9. |
- Colombo, Alessandro, et al.
(author)
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Measurement Scheduling for Control Invariance in Networked Control Systems
- 2018
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In: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; 2018-December, s. 3361-3366
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Conference paper (peer-reviewed)abstract
- We discuss a new reachability problem for networked controlled system where a master node - the controller - broadcasts commands to a set of slave nodes, which must take turn to relay back state measurements. This problem finds applications in some robotics and intelligent transportation systems setups. Constraints on communication demand a coupled design of the controller and the measurement schedule. We prove that the problem is formally equivalent to the Pinwheel Problem from scheduling theory, and building on this result we provide conditions for schedulability and reachability. The results are illustrated in three numerical examples.
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| 10. |
- Colombo, Alessandro, et al.
(author)
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Simultaneously Stabilizing Networked Systems with Minimal Communication
- 2024
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In: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 69:6, s. 3589-3601
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Journal article (peer-reviewed)abstract
- Self-triggered feedback control is used as a means to reduce the energy and communication requirements of networked systems. Triggered-control schemes result in aperiodic communications, with a potential for communication conflicts when multiple feedback loops are closed over a shared network. In this paper, we analyze the necessary/sufficient conditions for simultaneous stabilizability of a set of nonlinear systems over a network from the perspective of scheduling theory, using Lyapunov functions and input to state stability. We then propose a recursively feasible self-triggering scheme that minimizes the usage of the communication channel while ensuring the stability of all systems.
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