主动队列管理中的PID控制器

作为对终端系统上拥塞控制的一种补充，中间节点上的主动队列管理（AQM）策略在保护较高吞吐量的基础上有效地控制队列长度，从而实现了控制端到端的时延，保证QoS的目的。C.Hollot等人（2001）用经典控制理论中频域校正的方法设计了用于AQM的PI控制器，但参数整定上的试凑方法不免代有盲目性；算法的瞬态性能指标也不够理想。为此，该文引入了微分环节来增强系统的响应能力，同时给出了基于稳定裕度的参数整定方法，使PID控制器的稳定性有了绝对保障。仿真试验表明PID算法的调节时间远远短于PI控制器，从而为在负载瞬息万变的网络环境中实现控制分组排队等待时间的目标提供了有力的技术保障。

PID controller for active queue management

Acting on the intermediate nodes, Active Queue Management (AQM) either keeps the high throughput for routers or effectively controls the queue lengths, so that arrives the object to control end-to-end delay for QoS guarantees. C. Hollot, et al. (2001) designed the PI controller for AQM with the frequency approach in classical control theory, but it seems to be unscientific to tune the controller parameters through trial-errors, moreover the transient performance of the PI controller is not perfect, such as the adjusting time is very long, etc. In this paper, the differential component is introduced to enhance the responsibility, and an approach for tuning controller parameters is put forward based on the explicit gain and phase margins. The simulation results show that the integrated performance of PID controller designed with the new approach is obviously superior to that of the PI controller.