主动队列管理的约束H_∞状态反馈控制方法

考虑Internet网络的时滞、物理量变化复杂、物理约束等因素,将主动队列管理问题(AQM)描述为约束系统的干扰抑制问题,运用约束H1控制理论设计AQM鲁棒控制器.首先将时变且不可准确测量的可用链路容量建模为已知名义常值加上未知时变干扰;同时考虑网络中存在的物理约束,利用双椭圆域方法将时域硬约束转化为一组LMI约束;最后通过求解LMI约束的优化问题得到状态反馈增益,解决网络拥塞控制系统的干扰抑制问题.同时与随机早期检测(RED)和PI算法的仿真结果比较显示,约束H1状态反馈控制器降低了链路容量的不确定性对系统动态特性的影响,提高了AQM算法的鲁棒性.

State-feedback constrained H-infinity control for active queue management

We propose a robust active queue management (AQM) algorithm based on constrained H-infinity control for the Internet system with time-delay, complex variations and physical constraints. Firstly, the available link bandwidth is modeled as a nominal constant value, which is known to the link, plus a time-variant disturbance, which is unknown. Furthermore, the double-ellipsoid method is used to translate time-domain hard constraints into LMI conditions. Then, the problem of AQM algorithm can be converted into the disturbance attenuation problem of constrained systems, and the controller is designed using constrained H-infinity control theory. By solving an optimization problem with a set of linear matrix inequalities, we obtain the state feedback gain. The results show that the proposed approach is robust against the disturbance caused by the link capacity. The transient response and tracking capability of the proposed approach are superior to that of the RED and PI controller. The effectiveness of the proposed approach is validated via simulations in MATLAB and NS2 (network simulator, version 2).