| 2311. |
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| 2312. |
- Chen, Guanpu, et al.
(författare)
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Continuous-Time Damping-Based Mirror Descent for a Class of Non-Convex Multi-Player Games with Coupling Constraints
- 2024
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Ingår i: 2024 IEEE 18th International Conference on Control and Automation, ICCA 2024. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 12-17
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Konferensbidrag (refereegranskat)abstract
- We study the computation of the global generalized Nash equilibrium (GNE) for a class of non-convex multi-player games, where players' actions are subject to both local and coupling constraints. Due to the non-convex payoff functions, we employ canonical duality to reformulate the setting as a complementary problem. Under given conditions, we reveal the relation between the stationary point and the global GNE. According to the convex-concave properties within the complementary function, we propose a continuous-time mirror descent to compute GNE by generating functions in the Bregman divergence and the damping-based design. Then, we devise several Lyapunov functions to prove that the trajectory along the dynamics is bounded and convergent.
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| 2313. |
- Chen, H.Q., et al.
(författare)
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Critical behavior of vortices in epitaxial Tl-2201 films at zero external field
- 2004
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Ingår i: PHYSICA STATUS SOLIDI B-BASIC RESEARCH. - : Wiley. - 0370-1972 .- 1521-3951. ; 241:15, s. 3556-3562
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Tidskriftsartikel (refereegranskat)abstract
- The resistive transition and current–voltage characteristics of a Tl-2201 superconducting microbridge are measured close to the critical temperature in zero external magnetic field. The dissipation mechanism is studied by analyzing dV/dI and power dissipation P(= IV) as functions of transport current. The Jc–T curves exhibit three distinct types of behavior depending on temperature. In the low temperature regime, the critical current density is proportional to (1 – T/Tc). At intermediate temperatures, thermally activated flux creep dominates and Jc is proportional to 1 – n(T/Tc) – m(T/Tc)2. In the high temperature regime, Jc is equal to the G–L depairing current. The depinning current, Jc1, is determined, taking into account thermally activated flux motion and flux motion induced by the transport current. Jc1 depends linearly on temperature and vanishes at 82 K, Jc1 = Jc1(0) (1 – T/Tc1).
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| 2314. |
- Chen, Jianqi, et al.
(författare)
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Geometrical Characterization Of Sensor Placement For Cone-Invariant And Multi-Agent Systems Against Undetectable Zero-Dynamics Attacks\Ast
- 2022
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Ingår i: SIAM Journal of Control and Optimization. - : Society for Industrial & Applied Mathematics (SIAM). - 0363-0129 .- 1095-7138. ; 60:2, s. 890-916
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Tidskriftsartikel (refereegranskat)abstract
- Undetectable attacks are an important class of malicious attacks threatening the security of cyber-physical systems, which can modify a system's state but leave the system output measurements unaffected and hence cannot be detected from the output. This paper studies undetectable attacks on cone-invariant systems and multi-agent systems. We first provide a general characterization of zero-dynamics attacks, which characterizes fully undetectable attacks targeting the nonminimum phase zeros of a system. This geometrical characterization makes it possible to develop a defense strategy seeking to place a minimal number of sensors to detect and counter the zero-dynamics attacks on the system's actuators. The detect and defense scheme amounts to computing a set containing potentially vulnerable actuator locations and nodes and a defense union for feasible placement of sensors based on the geometrical properties of the cones under consideration.
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| 2315. |
- Chen, Phoebus, et al.
(författare)
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Reducing Packet Loss Bursts in a Wireless Mesh Network for Stochastic Bounds on Estimation Error
- 2011
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - : IEEE conference proceedings. - 9781612848013 ; , s. 3130-3135
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A big challenge for wireless networked control systems is how to design the underlying networking algorithms and protocols to provide high reliability, defined as the end-to-end probability of packet delivery, despite the high packet loss rates of individual wireless links. This paper formulates the problem of jointly designing a set of packet forwarding policies on a multipath mesh network to meet control application requirements. We derive several results to help understand the problem space. First, we demonstrate that some common approaches, like applying a single forwarding policy to all packets or always routing packets on disjoint paths, are not optimal for the application when the links are bursty. Second, we introduce the notion of dominance to give a partial ordering to sets of forwarding policies, used to prove that an optimal policy schedules all outgoing links at each node and that an upper bound on the performance attained by unicast forwarding policies on the network graph can be computed assuming a flooding policy. Third, we demonstrate how to convert application performance metrics to packet forwarding policy objectives, using the probability that the error covariance of a Kalman filter stays within a bound as our application metric. Fourth, we provide an algorithm to compute the joint probability mass function that a sequence of packets are delivered, given a set of policies and a network graph. Finally, we describe how to obtain optimal policies via an exhaustive search, motivating future research for more computationally efficient solutions.
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| 2316. |
- Chen, Wei, et al.
(författare)
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Characterizing the Positive Semidefiniteness of Signed Laplacians via Effective Resistances
- 2016
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Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509018376 ; , s. 985-990
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Konferensbidrag (refereegranskat)abstract
- A symmetric signed Laplacian matrix uniquely defines a resistive electrical circuit, where the negative weights correspond to negative resistances. The positive semidefiniteness of signed Laplacian matrices is studied in this paper using the concept of effective resistance. We show that a signed Laplacian matrix is positive semidefinite with a simple zero eigenvalue if, and only if, the underlying graph is connected, and a suitably defined effective resistance matrix is positive definite.
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| 2317. |
- Chen, Wei, et al.
(författare)
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On Semidefiniteness of Signed Laplacians with Application to Microgrids
- 2016
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 49:22, s. 97-102
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Tidskriftsartikel (refereegranskat)abstract
- The paper investigates the positive semidefiniteness of signed Laplacians. It is noted that a symmetric signed Laplacian defines a unique resistive electrical network, wherein the negative weights correspond to negative resistances. As such, the positive semidefiniteness of the signed Laplacians is equivalent to the passivity of the associated resistive networks. By utilizing n-port circuit theory, we obtain several equivalent conditions for signed Laplacians to be positive semidefinite with a simple zero eigenvalue. These conditions characterize a set of negative weights that maintain the semidefiniteness of the Laplacian. The results are used to analyze the small-disturbance angle stability of microgrids as an application.
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| 2318. |
- Chen, Wei, et al.
(författare)
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On Spectral Properties of Signed Laplacians With Connections to Eventual Positivity
- 2021
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 66:5, s. 2177-2190
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Tidskriftsartikel (refereegranskat)abstract
- Signed graphs have appeared in a broad variety of applications, ranging from social networks to biological networks, from distributed control and computation to power systems. In this article, we investigate spectral properties of signed Laplacians for undirected signed graphs. We find conditions on the negative weights under which a signed Laplacian is positive semidefinite via the Kron reduction and multiport network theory. For signed Laplacians that are indefinite, we characterize their inertias with the same framework. Furthermore, we build connections between signed Laplacians, generalized M-matrices, and eventually exponentially positive matrices.
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| 2319. |
- Chen, Xiaochang, et al.
(författare)
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Automatic Overtaking on Two-way Roads with Vehicle Interactions Based on Proximal Policy Optimization
- 2021
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Ingår i: 2021 32nd IEEE Intelligent Vehicles Symposium (IV). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1057-1064
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Konferensbidrag (refereegranskat)abstract
- Overtaking the lead vehicle on two-way roads in the presence of several oncoming vehicles is a complex task for autonomous vehicles. In this paper, we formulate the overtaking behavior of an ego vehicle based on a deep reinforcement learning (DRL) method. First, a two-way urban road is created, wherein the ego vehicle aims to reach the destination safely and efficiently while considering multiple traffic participants. We use different intelligent driver model (IDM) parameters to account for different drivers' habits. Furthermore, we introduce different responses of other vehicles when the ego vehicle takes overtaking maneuver. Then, a hierarchical control framework is proposed to manage vehicles on the road, which supervises vehicle behaviors at the high layer and controls the motion at the lower layer. The DRL method named Proximal Policy Optimization is applied to derive the high-level decision-making policies. A self-attention mechanism is further introduced to improve the performance of our algorithm. Finally, the overtaking maneuvers of the ego vehicle in different training timesteps are analyzed and how the responses of other vehicles affect the ego one's overtaking behavior is investigated. Simulation results show that our approach can achieve good performance to deal with the two-way road autonomous overtaking task. Supplementary video is available at https://youtu.be/jPEGjM7cBuk.
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| 2320. |
- Chen, Xiao, et al.
(författare)
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Safe Intersection Coordination with Mixed Traffic : From Estimation to Control
- 2023
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose an integrated framework for safe intersection coordination of connected and automated vehicles (CAVs) in mixed traffic. An intelligent intersection is introduced as a central node to orchestrate state data sharing among connected agents and enable CAV to acknowledge the presence of human-driven vehicles (HDVs) beyond the line of sight of onboard sensors. Since state data shared between agents might be uncertain or delayed, we design the intelligent intersection to safely compensate for these uncertainties and delays using robust set estimation and forward reachability analysis. When the intersection receives state data from an agent, it first generates a zonotope to capture the possible measurement noise in the state estimate. Then, to compensate for communication and processing delays, it uses forward reachability analysis to enlarge the set to capture all the possible states the agent could have occupied throughout the delays. Finally, using the resulting set as the initial condition, a distributed model predictive control onboard the CAV will plan an invariant safe motion by considering the worst-case behavior of human drivers. As a result, the vehicle is guaranteed to be safe while driving through the intersection. A prototype of our proposed framework is implemented using.
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