| 1. |
- Chen, Fei, et al.
(författare)
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Leader-follower Formation Control with Prescribed Performance Guarantees
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870.
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of achieving relative position-based formation control for leader-follower multi-agent systems in a distributed manner using a prescribed performance strategy. Both the first and second-order cases are treated and a leader-follower framework is introduced in the sense that a group of agents with external inputs are selected as leaders in order to drive the group of followers in a way that the entire system achieves a target formation within certain prescribed performance transient bounds. Under the assumption of tree graphs, a distributed control law is proposed for the first-order case when the decay rate of the performance functions is within a sufficient bound. Then, two classes of tree graphs that can have additional followers are investigated. For the second-order case, we propose a distributed control law based on a backstepping approach for the group ofleaders to steer the entire system achieving the target formation within the prescribed performance bounds. Finally, several simulation examples are given to illustrate the results.
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| 2. |
- Colombo, Leonardo J., et al.
(författare)
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Motion Feasibility Conditions for Multiagent Control Systems on Lie Groups
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2325-5870. ; 7:1, s. 493-502
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Tidskriftsartikel (refereegranskat)abstract
- We study the problem of motion feasibility for multiagent control systems on Lie groups with collision-avoidance constraints. We first consider the problem for kinematic left-invariant control systems and next, for dynamical control systems given by a left-trivialized Lagrangian function. Solutions of the kinematic problem give rise to linear combinations of the control inputs in a linear subspace, annihilating the collision-avoidance constraints. In the dynamical problem, motion feasibility conditions are obtained by using techniques from variational calculus on manifolds, given by a set of equations in a vector space, and Lagrange multipliers annihilating the constraint force that prevents the deviation of solutions from a constraint submanifold.
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| 3. |
- Hashimoto, Kazumune, et al.
(författare)
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Distributed l(1)-State-and-Fault Estimation for Multiagent Systems
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:2, s. 699-710
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a distributed stateand-fault estimation scheme for multiagent systems. The estimator is based on an l(1)-norm optimization problem, which is inspired by sparse signal recovery in the field of compressive sampling. Two theoretical results are given to analyze the correctness of our approach. First, we provide a necessary and sufficient condition such that the state and fault signals are correctly estimated. The result presents a fundamental limitation of the algorithm, which shows how many faulty nodes are allowed to ensure correct estimation. Second, we analyze how the estimation error grows over time by showing that the upper bound of the estimation error depends on the previous state estimate and the number of faulty nodes. An illustrative example is given to validate the effectiveness of the proposed approach.
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| 4. |
- Kluegel, Markus, et al.
(författare)
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Joint Cross-Layer Optimization in Real-Time Networked Control Systems
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:4, s. 1903-1915
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Tidskriftsartikel (refereegranskat)abstract
- Networked control system (NCS) refers to a set of control loops that are closed over a communication network. In this article, the joint operation of control and networking for NCS is investigated wherein the network serves the sensor-to-controller communication links for multiple stochastic linear time-invariant (LTI) subsystems. The sensors sample packets based on the observed plant state, which they send over a shared multihop network. The network has limited communication resources, which need to be assigned to competing links to support proper control loop operation. In this setup, we formulate an optimization problem to minimize the weighted-sum linear-quadratic-Gaussian cost of all loops, taking into account the admissible sampling, control, congestion control (CC), and scheduling policies. Under some mild assumptions on the sampling frequencies of the control loops and the communication network, we find the joint optimal solution to be given by a certainty equivalence control with a threshold-based sampling policy, as well as a back-pressure-type scheduler with a simple pass-through CC. The interface between network and control loops is identified to be the buffer state of the sensor node, which can be interpreted as network price for sampling a packet from the control perspective. We validate our theoretical claims by simulating NCSs comprised of multiple LTI stochastic control loops communicating over a two-hop cellular network.
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| 5. |
- Lindemann, Lars, et al.
(författare)
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Barrier Function-based Collaborative Control ofMultiple Robots under Signal Temporal Logic Tasks
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:4, s. 1916-1928
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the recent interest in cyber-physicaland autonomous robotic systems, we study the problem ofdynamically coupled multi-agent systems under a set of signaltemporal logic tasks. In particular, the satisfaction of each ofthese signal temporal logic tasks depends on the behavior of adistinct set of agents. Instead of abstracting the agent dynamicsand the temporal logic tasks into a discrete domain and solvingthe problem therein or using optimization-based methods, wederive collaborative feedback control laws. These control laws arebased on a decentralized control barrier function condition thatresults in discontinuous control laws, as opposed to a centralizedcondition resembling the single-agent case. The benefits of ourapproach are inherent robustness properties typically present infeedback control as well as satisfaction guarantees for continuous-time multi-agent systems. More specifically, time-varying controlbarrier functions are used that account for the semantics of thesignal temporal logic tasks at hand. For a certain fragment ofsignal temporal logic tasks, we further propose a systematic wayto construct such control barrier functions. Finally, we showthe efficacy and robustness of our framework in an experimentincluding a group of three omnidirectional robots
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| 6. |
- Milosevic, Jezdemir, et al.
(författare)
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Estimating the impact of cyber-attack strategies for stochastic networked control systems
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers Inc.. - 2325-5870. ; 7:2, s. 747-757
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Tidskriftsartikel (refereegranskat)abstract
- Risk assessment is an inevitable step in implementation of a cyber-defense strategy. An important part of this assessment is to reason about the impact of possible attacks. In this paper, we study the problem of estimating the impact of cyber-attacks in stochastic linear networked control systems. For the stealthiness constraint, we adopt the Kullback-Leibler divergence between attacked and nonattacked residual sequences. Two impact metrics are considered: the probability that some of the critical states leave a safety region and the expected value of the infinity norm of the critical states. For the first metric, we prove that the optimal value of the impact estimation problem can be calculated by solving a set of convex problems. For the second, we derive efficiency to calculate lower and upper bounds. Finally, we show compatibility of our framework with a number of attack strategies proposed in the literature and demonstrate how it can be used for risk assessment in an example.
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| 7. |
- Wu, S., et al.
(författare)
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Learning Optimal Scheduling Policy for Remote State Estimation under Uncertain Channel Condition
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:2, s. 579-591
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Tidskriftsartikel (refereegranskat)abstract
- We consider optimal sensor scheduling with unknown communication channel statistics. We formulate two types of scheduling problems with the communication rate being a soft or hard constraint, respectively. We first present some structural results on the optimal scheduling policy using dynamic programming and assuming that the channel statistics is known. We prove that the Q-factor is monotonic and submodular, which leads to threshold-like structures in both problems. Then we develop a stochastic approximation and parameter learning frameworks to deal with the two scheduling problems with unknown channel statistics. We utilize their structures to design specialized learning algorithms. We prove the convergence of these algorithms. Performance improvement compared with the standard Q-learning algorithm is shown through numerical examples, which also discuss an alternative method based on recursive estimation of the channel quality.
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| 8. |
- Xing, L., et al.
(författare)
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Robust Event-Triggered Dynamic Average Consensus Against Communication Link Failures With Application to Battery Control
- 2020
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Ingår i: IEEE Transactions on Control of Network Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2325-5870. ; 7:3, s. 1559-1570
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic average consensus (DAC) has found applications in various systems. The existing event-triggered DAC algorithms have not well addressed the issue of key communication link failures that lead to the separation of the initial communication topology. This article presents a modified event-triggered DAC algorithm that is independent of its initial conditions. As a result, it is robust against key communication link failures. In this algorithm, each agent decides locally when to transmit signals to its neighbors. In this way, the communication burden among the neighboring agents is reduced. A numerical example is provided to illustrate the effectiveness of the proposed algorithm. Moreover, the proposed algorithm is applied to a state-of-charge balance control problem of batteries in energy systems, and both simulations and hardware-in-the-loop tests are provided to demonstrate the control performance.
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