The H_∞ Control Of The Coordination Of The Variable Speed Limits And Control For Ramp Metering

Highway speed limit system is nonlinear,time-varying.Therefore,it is disturbed by many factors.Two methods of robust control of the highway speed limit system was adopt in this paper:one is the robust control for freeway,that is when the external interference appears on the highway,design the robust speed controller to make the closed loop system of highway to be stable,and the parameters of traffic flow to be asymptotic stable,be unlike in great change.The other one is the controlling of entrance ramp,as an auxiliary means:with the combination of the control for the inflow of ramp and mainline speed limit,to achieve the coordinated control of main line speed limit and ramp control.In the aspect of freeway mainline robust speed limit control,this paper makes analysis and operation with the following steps:1.Establish nonlinear equation of state with the macroscopic traffic flow model under speed limit;2.Linearizing the nominal affine nonlinear systems;3.by considering uncertainties of the affine nonlinear systems,design the robust controller to make the closed-loop control system internal stable;4.according to the feedback linearization system,design of linear robust controller with D-K iterative method or μ-K iterative method;5.Backward the linear robust controller into the affine nonlinear system,then obtain the nonlinear robust controller.In the aspect of coordinated control of ramp control and main line speed control,using the improved macroscopic traffic flow model to characterize the object,and make the steady operation of expressway traffic flow as the target,set up a coordinated control model for freeway mainline control and ramp control,and solve the problem with the robust algorithm.The robust control method is applied to the highway speed limit control,which can improve the anti-interference ability of the system,and this method has a strong practical value in actual use.when accidents,repairs,and other disturbances appears in the highway system,it can make the parameters of the traffic flow will not fluctuate greatly,and it will improve the highway capacity and reduce the travel time under the disturbance of the non external factors effectively.