拒绝服务攻击下网络化多率采样系统的触发策略与安全控制研究

The security modeling, attack detection, flexible communication and resilient control of networked multi-rate sampling system (NMCS) under denial of service (DoS) attacks will be studied in this project. Firstly, the flexible communication scheme that combines multi-rate sampling with event-triggered transmission is proposed by considering the constraints of the network resource and complexity of the physical system; Also, the unify model of NMCS that integrates with the dynamic property of control and communication is established to reveal the dynamic evolution rules of physical system under DoS attacks. Then, according to the deficiency of control capacity and the property of multi-rate sampling, the DoS attack detection method is studied based on the traffic characteristics of channel. In addition, state reconstruction and predication strategies are studied in case of incomplete information. Subsequently, based on the time varying and non-deterministic resources due to DoS attacks, the flexible event-triggered communication schemes with a certain perception of network resources and control performance are designed in order to realize that the flexible and efficient states transmission of each control loop under the different sampling periods. On these basis and by taking the energy-constraints of the DoS attacks into account, the secure controller that resilient to the DoS attacks is designed to self-adaptive to the changes of network resources. At last, the simulation and application verification is conducted to refine the secure theory by exploiting the obtained theorem results.

本项目面向DoS攻击下网络化多率采样系统的安全建模、攻击检测、柔性通信与弹性控制等问题展开研究。针对通信资源的有限性和物理系统的复杂性，提出多率采样与事件触发相结合的通信机制，进行融合控制系统和通讯网络动态性能的NMCS统一建模，揭示DoS攻击下物理系统动态演化规律；其次，针对通讯网络接纳控制能力的缺失，结合多率采样特性，基于信道流量行为特征进行DoS攻击检测，研究非完整信息情形下NMCS的状态重构与预测方法，为控制器设计提供决策依据；然后，针对DoS攻击导致的可用网络资源的时变性和不确定性，设计对网络资源与系统性能具有一定感知能力的柔性事件触发通信策略，实现不同检测周期下不同控制回路状态信息灵活、高效传输；在此基础上，考虑DoS攻击的能量约束，设计对DoS攻击具有一定弹性的安全控制器，使系统性能自主适应网络资源变化；最后，将所得理论成果进行仿真与应用验证，完善所提出的安全理论方法。

针对网络化系统(Networked Control System，NCS)在通过共享通信网络进行数据传输时的开放性和脆弱性问题，研究了具有拒绝服务攻击(Denial of Service, DoS)和虚假数据注入攻击(False Data Injection, FDI)的NCS安全控制策略设计问题。考虑到DoS和FDI攻击的本质机理和特征，建立了非完整信息下的NCS状态空间统一模型，设计了事件触发机制和安全控制器分别来保证控制回路状态信息的高效传输和系统的安全运行，实现了在网络攻击下的NCS控制与通信协同分析；综合考虑到DoS和FDI攻击通常对闭环控制回路造成的时延、数据丢包问题，致使采样周期、信道数据传输速率随攻击行为实时变化，造成各个闭环控制策略的差异化采样。在此基础上研究了一类受DoS和FDI攻击影响的网络化多率控制系统(Networked Multi-rate Control Systems，NMCS)安全控制策略设计问题；针对DoS和FDI攻击的无规律性、难预测性及其对系统造成的大时滞及不确定性，提出了基于模型预测控制的安全控制器设计方法。当检测机制表明攻击发生时，利用前一时刻对未来时域的预测值和卡尔曼滤波器的估计值来重构控制器的输入输出序列，并设定等待周期来进一步降低攻击造成的影响，以此保证NCS的整体性能安全可靠。