列车控制系统的抗拒绝服务攻击弹性控制策略

当遭受拒绝服务(DoS)攻击时,分布式列车控制系统的弹性控制问题受到广泛关注.本文提出了一种基于分布式领导车状态观测器和障碍李雅普诺夫函数的弹性控制策略,不仅可以避免列车碰撞,同时实现了编队控制的目标.首先,给出了一种分布式的领导车状态观测器设计方法,用于实时估计领导车的状态.理论分析表明,在DoS攻击满足一定约束的条件下,该状态观测器的估计误差具有指数稳定特性.在此基础上,通过将列车碰撞避免问题转化为状态受限问题,提出一种基于障碍李雅普诺夫函数的状态受限控制律,解决了DoS攻击下确保碰撞避免的车队控制问题.最后,数值仿真证实了本文方法的有效性.     

Dynamic Event-Triggered Scheduling and Platooning Control Co-Design for Automated Vehicles Over Vehicular Ad-Hoc Networks

This paper deals with the co-design problem of event-triggered communication scheduling and platooning control over vehicular ad-hoc networks (VANETs) subject to finite communication resource. First, a unified model is presented to describe the coordinated platoon behavior of leader-follower vehicles in the simultaneous presence of unknown external disturbances and an unknown leader control input. Under such a platoon model, the central aim is to achieve robust platoon formation tracking with desired inter-vehicle spacing and same velocities and accelerations guided by the leader, while attaining improved communication efficiency. Toward this aim, a novel bandwidth-aware dynamic event-triggered scheduling mechanism is developed. One salient feature of the scheduling mechanism is that the threshold parameter in the triggering law is dynamically adjusted over time based on both vehicular state variations and bandwidth status. Then, a sufficient condition for platoon control system stability and performance analysis as well as a co-design criterion of the admissible event-triggered platooning control law and the desired scheduling mechanism are derived. Finally, simulation results are provided to substantiate the effectiveness and merits of the proposed co-design approach for guaranteeing a trade-off between robust platooning control performance and communication efficiency.      

Data-iteration cooperative adaptive cruise control of mixed heterogeneous vehicle platoons with unknown dynamic characteristics

This paper considers the cooperative adaptive cruise control (CACC) problem of mixed heterogeneous vehicle platoons composed of human-driven and CACC vehicles with unknown dynamic characteristics and an alternative to CACC for platooning of the heterogeneous vehicle platoon is presented. Adaptive dynamic programming is firstly used to learn the dynamic characteristics of acceleration of vehicles from the sampled data. Then the data-iteration optimal CACC controller is computed to ensure that each CACC vehicle can reach a desired inter-vehicle distance and desired common velocity with no prior knowledge of the dynamics of vehicles in the mixed platoon. Moreover, the string stability of the mixed vehicle platoon is derived by establishing some sufficient conditions on the acceleration transfer function of adjacent vehicles. Two simulation experiments of a six-vehicle mixed platoon are used to illustrate the effectiveness of the proposed CACC method.     

Decentralized Resilient H∞ Load Frequency Control for Cyber-Physical Power Systems Under DoS Attacks

This paper designs a decentralized resilient H_∞ load frequency control (LFC) scheme for multi-area cyber-physical power systems (CPPSs). Under the network-based control framework, the sampled measurements are transmitted through the communication networks, which may be attacked by energy-limited denial-of-service (DoS) attacks with a characterization of the maximum count of continuous data losses (resilience index). Each area is controlled in a decentralized mode, and the impacts on one area from other areas via their interconnections are regarded as the additional load disturbance of this area. Then, the closed-loop LFC system of each area under DoS attacks is modeled as an aperiodic sampled-data control system with external disturbances. Under this modeling, a decentralized resilient H_∞ scheme is presented to design the state-feedback controllers with guaranteed H_∞ performance and resilience index based on a novel transmission interval-dependent loop functional method. When given the controllers, the proposed scheme can obtain a less conservative H_∞ performance and resilience index that the LFC system can tolerate. The effectiveness of the proposed LFC scheme is evaluated on a one-area CPPS and two three-area CPPSs under DoS attacks.      

Event-driven intermittent control for vehicle platooning over vehicular ad-hoc networks

This article is concerned with the problem of vehicle platooning control over vehicular ad-hoc networks (VANETs). Compared with the existing platooning control strategies, an event-driven intermittent control method is developed to reduce control costs and extend the operating life of controllers while ensuring the desired platooning performance. By establishing suitable boundary functions and Lyapunov function, the control input is determined according to the relationship among the trajectories of these functions. Thereafter, sufficient conditions for platooning control performance analysis are derived by a set of linear matrix inequalities. Wherein, the vehicle platooning based on intermittent control is obtained to maintain the desired inter-vehicle distance and a uniform speed in the platoon. Furthermore, a simple optimization algorithm is constructed to calculate the smallest upper bound on tracking errors. Finally, several simulations based on different topologies are provided to verify the validity of the proposed method.     

Wheeled Mobile Robots Control in a Linear Platoon

Future transportation systems will require a number of drastic measures, mostly to lower traffic jams and air pollution in urban areas. Automatically guided vehicles capable of driving in a platoon fashion will represent an important feature of such systems. Platooning of a group of automated wheeled mobile robots relying on relative sensor information only is addressed in this paper. Each vehicle in the platoon must precisely follow the path of the vehicle in front of it and maintain the desired safety distance to that same vehicle. Vehicles have only distance and azimuth information to the preceding vehicle where no inter-vehicle communication is available. Following vehicles determine their reference positions and orientations based on estimated paths of the vehicles in front of them. Vehicles in the platoon are then controlled to follow the estimated trajectories. Then presented platooning control strategies are experimentally validated by experiments on a group of small-sized mobile robots and on a Pioneer 3AT mobile robot. The results and robustness analysis show the proposed platooning approach applicability.     

Fully Distributed Resilient Cooperative Control of Vehicular Platoon Systems Under DoS Attacks

Dear Editor, This letter is concerned with distributed resilient platoon control of multiple vehicles subject to denial-of-service (DoS) attacks. In order to ac...     

Fuel efficiency‐oriented platooning control of connected nonlinear vehicles: A distributed economic MPC approach

This paper considers the fuel efficiency‐oriented platooning control problem of connected vehicles. We present a novel distributed economic model predictive control (EMPC) approach to solve the problem of the vehicle platoon subject to nonlinear dynamics and safety constraints. In order to improve fuel economy of the whole vehicle platoon, the fuel consumption criterion is used to design the distributed EMPC strategy for the platoon. Meanwhile, the car‐tracking performance is exploited to guarantee stability and string stability of the platoon. Then the fuel efficiency control problem of the platoon is formulated as a distributed dual‐layer economic optimal control problem, which is solved in a fashion of receding horizon. It is proved that the proposed strategy guarantees asymptotic stability and predecessor‐follower string stability as well as fuel economy of the whole platoon by minimizing the fuel consumption cost. Finally, the effectiveness of the proposed strategy is highlighted by comparing its performance with that of the traditional distributed MPC strategy in numerical simulations.     

On distributed constrained formation control in operator–vehicle adversarial networks

We consider an operator–vehicle network where each vehicle is remotely maneuvered by an operator. The objective of the operators is to steer the vehicles to the desired formation subject to the given state and input constraints. Each operator–vehicle pair is attacked by an adversary who is able to maliciously replay the control commands sent from the operator. To play against attackers, we come up with a novel distributed resilient algorithm based on the receding-horizon control methodology, and show that the algorithm is able to allow vehicles, on the one hand, satisfy state and input constraints, and on the other hand, asymptotically achieve the desired formation despite replay attacks. With slight modifications, our proposed algorithm shows an analogous resilience to denial-of-service attacks.     

String stability for vehicular platoon control: Definitions and analysis methods

The platooning of connected and automated vehicles (CAVs) is expected to have a transformative impact on road transportation, e.g, enhancing highway safety, improving traffic efficiency, and reducing fuel consumption. One critical task of platoon control is to achieve string stability, for which various models and methods had been proposed. However, different types of definitions and analysis methods for string stability were proposed over the years and were not thoroughly compared. To fill these gaps, this paper aims to clarify the relationship of ambiguous definitions and various analysis methods, providing a rigorous foundation for future studies. A series of equivalences are summarized and discussed. The pros and cons of different analysis methods and definitions are discussed, too. All these discussions provide insights for practical selection of analyzing methods for vehicle platoons.     

Robust event‐triggered model predictive control for cyber‐physical systems under denial‐of‐service attacks

This paper investigates the resilient control problem for constrained continuous‐time cyber‐physical systems subject to bounded disturbances and denial‐of‐service (DoS) attacks. A sampled‐data robust model predictive control law with a packet‐based transmission scheduling is taken advantage to compensate for the loss of the control data during the intermittent DoS intervals, and an event‐triggered control strategy is designed to save communication and computation resources. The robust constraint satisfaction and the stability of the closed‐loop system under DoS attacks are proved. In contrast to the existing studies that guarantee the system under DoS attacks is input‐to‐state stable, the predicted input error caused by the system constraints can be dealt with by the input‐to‐state practical stability framework. Finally, a simulation example is performed to verify the feasibility and efficiency of the proposed strategy.     

A centralized control system for ecological vehicle platooning using linear quadratic regulator theory

This paper presents an ecological vehicle platooning control system that aims in reducing overall fuel consumption of the vehicles in a platoon. A centralized linear quadratic regulator system for controlling the vehicles in the platoon has been developed considering the aerodynamic characteristics of the vehicle and the resistance due to the road slope. The proposed control system is simulated on a highway with up?Cdown slopes for high speed driving. Its fuel saving performance is compared with a conventional decentralized vehicle platooning control system. Computer simulation results reveal the significant improvement in fuel economy by the proposed control system.     

智能交通系统车道保持纵横向耦合控制

考虑车辆纵横向运动之间的相互影响,采用位置预瞄和固定车辆间距跟随策略,对基于一列车队的自动化公路系统车道保持纵横向耦合控制进行了研究.利用车载前后双位置传感器检测车辆位置偏差,基于车辆纵横向动力学耦合模型,推导了基于预瞄的车道保持控制系统数学模型;采用非奇异的终端滑模控制技术,设计了车道保持纵横向耦合控制规律.通过构造李雅普诺夫函数,结合相平面方法,分析了控制系统的有限时间收敛性.采用6车辆编队,通过计算机仿真,对文中设计的控制规律进行了验证.仿真结果显示,车队中每个被控车辆在纵向上跟随期望状态的同时能够实现对期望车道轨迹的理想跟踪,跟踪误差精度不超过0.05 m.     

Guaranteeing safety for heavy duty vehicle platooning: Safe set computations and experimental evaluations

In this paper, we consider the problem of finding a safety criteria between neighboring heavy duty vehicles traveling in a platoon. We present a possible framework for analyzing safety aspects of heavy duty vehicle platooning. A nonlinear underlying dynamical model is utilized, where the states of two neighboring vehicles are conveyed through radar information and wireless communication. Numerical safe sets are derived through the framework, under a worst-case scenario, and the minimum safe spacing is studied for heterogenous platoons. Real life experimental results are presented in an attempt to validate the theoretical results in practice. The findings show that a minimum relative distance of 1.2 m at maximum legal velocity on Swedish highways can be maintained for two identical vehicles without endangering a collision. The main conclusion is that the relative distance utilized in commercial applications today can be reduced significantly with a suitable automatic control system.     

Resilient Time-Varying Formation-Tracking of Multi-UAV Systems Against Composite Attacks: A Two-Layered Framework

This paper studies the countermeasure design problems of distributed resilient time-varying formation-tracking control for multi-UAV systems with single-way communications against composite attacks, including denial-of-services (DoS) attacks, false-data injection attacks, camouflage attacks, and actuation attacks (AAs). Inspired by the concept of digital twin, a new two-layered protocol equipped with a safe and private twin layer (TL) is proposed, which decouples the above problems into the defense scheme against DoS attacks on the TL and the defense scheme against AAs on the cyber-physical layer. First, a topology-repairing strategy against frequency-constrained DoS attacks is implemented via a Zeno-free event-triggered estimation scheme, which saves communication resources considerably. The upper bound of the reaction time needed to launch the repaired topology after the occurrence of DoS attacks is calculated. Second, a decentralized adaptive and chattering-relief controller against potentially unbounded AAs is designed. Moreover, this novel adaptive controller can achieve uniformly ultimately bounded convergence, whose error bound can be given explicitly. The practicability and validity of this new two-layered protocol are shown via a simulation example and a UAV swarm experiment equipped with both Ultra-WideBand and WiFi communication channels.      

智能车辆队列横纵向有限时间滑模控制

针对智能车辆队列横纵向控制及误差快速收敛问题,本文提出一种分布式横纵向有限时间滑模控制策略.首先,考虑跟踪误差的连锁反应及横纵向耦合效应,利用投影变换建立车辆队列横纵向误差模型,提出一种车辆队列横纵向控制框架.而后,针对误差快速收敛问题,设计非奇异积分终端滑模面(NITSM)与自适应幂次积分趋近律(APIRL),通过构造Lyapunov函数分析系统的有限时间稳定性与队列稳定性.最后,基于Trucksim/Simulink联合仿真以及实车实验进一步验证了本文方法的有效性.结果表明,本文所提方法能保证队列稳定性,并实现误差快速收敛,规避跟踪误差的连锁反应及车辆横向运动对纵向车间距误差的影响.     

基于模型预测控制的电动车辆队列控制研究

针对车辆队列建模时参数不确定导致控制存在误差的问题,以及队列中跟随车辆稳定性问题,分析车辆纵向动力学,设计一个鲁棒MPC控制器和滑移率控制器来提高队列车辆的控制精度和稳定性.首先对纵向MPC控制器进行改进,提高车辆队列控制精度；同时为防止跟随车辆的轮胎打滑,设计一个MPC滑移率控制器对跟随车辆的轮胎滑移率进行控制约束,保证了跟随车辆的纵向稳定性.最后,进行仿真实验验证其有效性.仿真实验结果表明,与传统的LQR、MPC控制器相比,改进的鲁棒MPC纵向控制器控制精度更高,同时MPC滑移率控制器可防止跟随车辆的轮胎打滑,保证了跟随车辆的纵向稳定性.     

空气流动阻力下非线性车辆队列最优能耗控制方法

为了优化车辆队列在长距离行驶过程中的能源消耗,对空气流动阻力下车辆队列能耗优化间距策略以及相应的队列控制方法进行了研究;首先根据车辆队列在行驶过程中受到的空气流动阻力,建立基于异构风阻系数的车辆动力学模型;其次,设计基于滑模控制的非线性车辆队列控制方法,使其能够在不同风阻系数下稳定地收敛到期望的车辆队列;在此基础上,构建稳态下车辆队列能量消耗评价模型,并通过优化分析,计算能量消耗最优下的车辆队列期望车间距;最后通过数值仿真的手段验证所提控制方法的有效性与可行性;该结果表明:所设计的控制器能够使整个车辆队列达到期望的控制效果;得到的最优车间距能够使得特定条件下车辆队列稳态能量消耗降低。     

Encryption–decryption-based event-triggered consensus control for nonlinear MASs under DoS attacks

In this article, the consensus tracking problem is discussed for a class of discrete-time nonlinear multi-agent systems (MASs) subject to denial-of-service (DoS) attacks. The individual agents interact with each other via communication network whose topology is assumed to be time-varying and strongly connected. Two techniques are employed to deal with the network-induced complexities. On one hand, an event-triggering scheme is adopted to regulate the data transmission among agents with the purpose of making full utilization of the limited communication resources; and on the other hand, an encryption–decryption mechanism is designed with the aim to provide compensation, thereby mitigating the DoS attack effects. It is the objective of the addressed problem to develop a distributed model-free adaptive control law to enforce the MASs achieve desirable consensus performance. By using a specific projection algorithm in combination with a dynamic linearization method, the desired control protocol is formulated explicitly, whose effectiveness and applicability are demonstrated via an illustrative numerical example.     

Centralized and decentralized distributed control of longitudinal vehicular platoons with non‐uniform communication topology

In this paper, the distributed control of a longitudinal platoon of vehicles with non‐uniform communication topology is studied. In the case of non‐uniform communication topology, some eigenvalues of the network's matrix may be complex which complicates the stability analysis of the platoon. Most previous studies on vehicular platooning focus mainly on uniform topologies such as uni‐directional, bi‐directional, and multi predecessors following. Since all eigenvalues of these topologies are real, the stability analysis can be performed in a straightforward manner. A third‐order linear differential model is employed to describe the upper‐level dynamics of each vehicle. The 3 N‐order closed‐loop dynamics of the platoon are decoupled to individual third‐order dynamics by presenting a new approach. Two new centralized and decentralized control protocols are introduced to perform the stability analysis of the closed‐loop dynamics. A constant time headway strategy is employed to adjust the inter‐vehicle spacing. Simulation results with different scenarios are presented to illustrate the effectiveness of the proposed approaches.