Department of Adaptive Systems

Hierarchical control of transportation nets

The task aims at building a multi-level control of the traffic in large urban transportation nets. The basic unit we operate with is the traffic microregion. It is a logically delimited collection of crossroads and the communications joining the crossroads. We suppose, some of the crossroads are controlled by signal lights and the arms of the controlled crossroads are equipped by detectors -- measuring devices, providing us with transportation data (intensities and densities of the traffic flow).

The basic variable, we model and control is a vector of column lengths forming in the arms of the controlled crossroads. These columns are basically modeled on the physical principle "the increment of the column is given by the difference in the amount of incoming and outgoing cars". In addition to this, a linear dependence of the car density measured on the remote detector on the column length is considered. Thus a state space model for column lengths in the microregion is constructed.

The controlled, built on the basic of the presented model, has three levels:

1. Local control which cares of a single microregion, only. It predicts column lengths of the microregion (which are no measurable) and computes ratios of the greens for signal lights, so that the columns would be minimal. The estimation is performed by Kalman filtering, for the optimization is used linear programming..
2. Coordinating control cares about the "good relations" between the microregion. With no coordination, the microregions incline to overload their neighbors, if convenient for them. The coordination prevents this phenomenon. Both the model and the optimization are just slight modifications of those from the local control.
3. Exceptional states control cares about the states of the traffic, which do not belong to the common transportation. They are e.g. accidents, closures, big over-saturations etc. They are supposed to be described by discrete model and through them, mostly control using the collected expert knowledge will be realized.

The traffic control algorithm should be practically realized in cooperation with the well known Czech transportation company ELTODO.

Contact:

Support of grants

The project is developed under support of the following grants:  

• Ministry of Transportation of the Czech Republic, No. 1F43A/003/120.
• Research center DAR
  

Local SVN repository (accessible with password only):

http://mys.utia.cas.cz:1800/svn/doprava