查看更多>>摘要：This study addresses the resilient sliding mode control(SMC)problem for two-dimensional cyber-physical systems(2D CPSs)characterized by the Roesser model under denial-of-service attack(DoS-A),which can interfere with signal transmission over the communication network.First,the DoS-A model is established by introducing constraints on the DoS frequency and duration.Then,based on active or silent attack situations,the considered system is described as a switched mode.Furthermore,together with Lyapunov theory,the average dwell time technique is employed to deduce sufficient criteria that assure the existence of the desired sliding mode controller.Finally,verification examples are provided to show the validity of the established SMC scheme.
查看更多>>摘要：The robust finite-time synchronization control problem is investigated for master-slave networked nonlinear telerobotics systems(NNTSs)in this article.Although there have been some research achievements on finite-time control for the NNTSs,these studies are based on the strong assumptions of communication time delays or can only achieve finite-time bounded convergence even when the external forces are zero.Accordingly and in view of the importance of these issues,a novel robust composite learning adaptive control scheme rendering the finite-time master-slave synchronization is proposed in this paper.In particular,the influence of time delays on finite-time convergence of the system is analyzed by employing the multi-dimension finite-time small-gain framework.Meanwhile,in order to achieve accurate and fast estimation of uncertain parameters of the system,both the online historical and the instantaneous data of the estimation data are explored to derive the new parameter adaptive law under a more realizable interval-excitation(IE)condition.Therefore,the convergence of the position/force synchronization errors and the adaptive parameter estimation errors is obtained in finite time,and enhanced robustness of the closed-loop system will also be ensured.Finally,the superior performance of the proposed control algorithms is validated by numerical simulations and hardware experiments.
查看更多>>摘要：Robust open-set recognition(OSR)performance has become a prerequisite for pattern recogni-tion systems in real-world applications.However,the existing OSR methods are primarily implemented on the basis of single-modal perception,and their performance is limited when single-modal data fail to provide sufficient descriptions of the objects.Although multimodal data can provide more comprehensive informa-tion than single-modal data,the learning of decision boundaries can be affected by the feature representation gap between different modalities.To effectively integrate multimodal data for robust OSR performance,we propose logit prototype learning(LPL)with active multimodal representation.In LPL,the input multimodal data are transformed into the logit space,enabling a direct exploration of intermodal correlations without the impact of scale inconsistency.Then,the fusion weights of each modality are determined using an entropy-based uncertainty estimation method.This approach realizes adaptive adjustment of the fusion strategy to provide comprehensive descriptions in the presence of external disturbances.Moreover,the single-modal and multimodal representations are jointly optimized interactively to learn discriminative decision boundaries.Finally,a stepwise recognition rule is employed to reduce the misclassification risk and facilitate the distinc-tion between known and unknown classes.Extensive experiments on three multimodal datasets have been done to demonstrate the effectiveness of the proposed method.
查看更多>>摘要：In this paper,we explore state-based potential games using the semi-tensor product of matrices.First,applying the potential equation,we derive both a necessary and sufficient condition as well as a sufficient condition to verify whether a state-based game qualifies as a potential game.Next,we present two static equivalence conditions of state-based potential games.We then delve into dynamic equivalence.We propose a criterion that allows us to identify state-based games that are dynamically equivalent to state-based potential games and share similar dynamic properties.Ultimately,we introduce the concept of state-based networked evolutionary games.We provide a necessary and sufficient condition to ensure that a state-based networked evolutionary game can be classified as a state-based potential game.
查看更多>>摘要：This paper is concerned with event-triggered H∞ control of sampled-data systems.Its novelties lie in three aspects:(ⅰ)A novel accumulated-state-error-based event-triggered scheme is introduced by com-paring the integral of the state error fromtkto t with the system state sampled at tk.This condition works well due to the fact that the so-called Zeno behaviour does not occur.(ⅱ)A novel Lyapunov functional is constructed to establish a criterion to ensure some certain H∞ performance of the closed-loop system.This Lyapunov functional is dependent on the integral of the state error involved in the event-triggered scheme.(ⅲ)Under the event-triggered sampling scheme,suitable state-feedback controllers can be designed rather than be given a priori.Moreover,a self-triggered implementation of the proposed event-triggered sampling scheme is presented as well.Finally,a batch reactor model and an inverted pendulum system are given to demonstrate the effectiveness of the proposed method.
查看更多>>摘要：Exploration targeting outer planets and even the edge of the solar system is an emerging direction for the deep-space exploration in the next decades.To address this challenge,a novel two-layer Lagrange-based relay network topology is proposed in this study.Specifically,we utilize the Sun-Mars and Sun-Saturn Lagrange points(LPs)L4 and L5 to build a two-layer backbone relay network,which ensures continuous and high-efficiency communication capability for the exploration of the solar system.Furthermore,we utilize the planetary gravity assist and design the transfer trajectory of backbone relays with the help of planetary celestial body motion equations and Kepler's laws.Moreover,we conduct link budget analysis for multihop relay transmission under Gamma-Gamma distribution,shadowed Rician fading,and additive white Gaussian noise channels in several typical exploration scenarios and validate that the LP relays can effectively support future deep-space exploration missions.
查看更多>>摘要：Hardware components can cause different impairments,including power amplifier(PA)non-linearities,which inevitably impact the system performance of satellite communications(SATCOM).In this work,we consider a multi-beam SATCOM downlink system and investigate the distortion-aware beamforming scheme with the characteristics of PA non-linearities.Notably,we aim to maximize the resource efficiency(RE),defined as the weighted sum of energy efficiency(EE)with spectral efficiency(SE),to obtain a flexible EE-SE tradeoff while accounting for the characteristics of PA distortion and the total power constraints.Given that the optimization objective is a sum of ratios and the high non-convexity involved in constraints,we propose an efficient approach that exploits the quadratic transformation,the Lagrange multiplier method,and the gradient ascent approach to handle this issue.Simulation results demonstrate the effectiveness of the distortion-aware beamforming approach in achieving the EE-SE tradeoff and exhibit a substantial RE performance gain over the conventional approach with ideal linear PAs assumed at the satellite transmitters.
查看更多>>摘要：Extremely large-scale antenna array(ELAA)at millimeter wave(mmWave)and Terahertz(THz)band has been considered a key technology for combating high attenuation in high-frequency bands in future 6G communications.Uniform circular arrays(UCAs)have attracted much attention because of their ability to provide flat beamforming gain at all angles.To realize efficient beamforming,beam training is widely used to acquire channel state information.However,with a large antenna number,the beam training overhead in ELAA systems becomes overwhelming.Moreover,with a large bandwidth,the beam defocus effect severely degrades beam training accuracy.To address these issues,this paper proposes a frequency-dependent focusing(FDF)-based beam training scheme to realize effective beam training in near-field wideband ELAA systems with UCA.Specifically,we first analyze the FDF property of UCA,where signals at different subcarriers can simultaneously focus on different distances.Then,by exploiting the FDF property to search different distances using different subcarriers simultaneously,we design a hierarchical codebook and propose an FDF-based beam training scheme.To reveal the effectiveness of the proposed scheme,we compare its necessary beam training overhead with that of existing schemes.Finally,the simulation results demonstrate that the proposed scheme can achieve accurate beam training in near-field wideband UCA systems with a low beam training overhead.
查看更多>>摘要：This paper explores covert broadcast communication in a challenging situation in which the transmitter,Alice,faces uncertainty regarding the position of the passive adversary,Willie.In this situation,controlling the signal exposure becomes difficult.Specifically,this paper focuses on the cases where Alice can delimit the suspicious areas where Willie may be located.The suspicious areas can have arbitrary number and shapes.Under the Rician fading model,the analytical expression of Willie's detection performance is derived.Then,the transmit power,the beamforming direction,and the number of channel uses are jointly designed to minimize the optimal Willie's detection performance among all the possible positions of Willie,on the premise of satisfying receivers'quality-of-service requirements.To tackle the formulated knotty problem with an infinite number of irregular and discontinuous Willie's possible positions,the continuous nature of the antenna pattern is exploited to convert the original problem into the one with a finite number of possible positions,by sampling the suspicious areas.Then,different algorithms are developed to address the resultant non-convex optimization problem for single-antenna Willie and multi-antenna Willie,respectively.Numerical results demonstrate significant performance gains of the proposed scheme over the widely-adopted maximum ratio transmission scheme,which indicates that simply adjusting the main lobe towards the receiver is indeed far away from optimum and shows the importance of leveraging Alice's limited knowledge of Willie's position.
查看更多>>摘要：Memory corruption attacks(MCAs)refer to malicious behaviors of system intruders that modify the contents of a memory location to disrupt the normal operation of computing systems,causing leakage of sensitive data or perturbations to ongoing processes.Unlike general-purpose systems,unmanned systems cannot deploy complete security protection schemes,due to their limitations in size,cost and performance.MCAs in unmanned systems are particularly difficult to defend against.Furthermore,MCAs have diverse and unpredictable attack interfaces in unmanned systems,severely impacting digital and physical sectors.In this paper,we first generalize,model and taxonomize MCAs found in unmanned systems currently,laying the foundation for designing a portable and general defense approach.According to different attack mechanisms,we found that MCAs are mainly categorized into two types—return2libc and return2shellcode.To tackle return2libc attacks,we model the erratic operation of unmanned systems with cycles and then propose a cycle-task-oriented memory protection(CToMP)approach to protect control flows from tampering.To defend against return2shellcode attacks,we introduce a secure process stack with a randomized memory address by leveraging the memory pool to prevent Shellcode from being executed.Moreover,we discuss the mechanism by which CToMP resists the return-oriented programming(ROP)attack,a novel variant of return2libc attacks.Finally,we implement CToMP on CUAV V5+with Ardupilot and Crazyflie.The evaluation and security analysis results demonstrate that the proposed approach CToMP is resilient to various MCAs in unmanned systems with low footprints and system overhead.
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