Abstract:

In this paper,the hierarchical structure and the fuzzy control are adopted to solve the coordinated control of multiple sections on freeway.A finite-difference model of macroscopic traffic flow is first established.A multilayer control structure is then proposed according to the characteristics of traffic systems.In this structure,the control problems of freeway traffic systems are divided into three layers,that is,an adaptation layer,a coordination layer and a direct control layer.The direct control layer is in charge of the ramp metering rate via fuzzy control,the coordination layer determines the desired traffic density for the direct control layer,and the adaptation layer answers for the selection of traffic models and the adjustment of model parameters according to the real·time freeway traffic status.Simulated results show that the coordinated fuzzy logic control is of good dynamic and steady-state perfor-mance.This method can efectively eliminate traffic jams and maintain stability of main traffic flows.

Key words: freeway, coordinated control, fuzzy control, traffic flow model, simulation