PI controller is often used to control active queue management(AQM)

but its trial method of tuning controller is aimless

and the dynamic performance of algorithm is not enough satisfying.Simplified network model based on fluid flow theory is derived in this paper

and based on this model

an improved algorithm

i.e.particle swarm optimization (PSO) algorithm is applied to optimization of PID controller parameters.In the following

a new performance function including the system adjusting time

rise time

overshoot

steady state error and sinusoidal position tracking error is defined.It is fast to calculate a group of PID controller parameters that minimize the evaluation function by searching in the given controller parameter area

and then the PID controller is applied to AQM system.The simulation experimental results show that under the two conditions of large time delay and sudden business flow

the overshoot is both less than 5%

the adjusting time is less than 5 seconds and 4 seconds separately

and the steady error is less than 2 packets and 3 packets separately

so the dynamic state and steady state performances of the proposed algorithm are obviously superior to those of the existing RED and PI algorithms under the two conditions.