A switched ramp-metering controller for freeway traffic systems

In the paper a switched controller for freeway traffic systems is proposed. First of all, the Cell Transmission Model, a first-order model commonly used for freeway traffic systems, is described and a switched version of this model is proposed. According to this version, a freeway can be seen as a piece wise-affine system, i.e. a system which switches among different sets of linear difference equations. Then, based on this model, a switched controller is proposed so that different control laws are applied depending on the operation mode of the system. More specifically, the controller computes the current control law depending on the mode of the system and on the probabilities to reach future states, on the basis of a Discrete-Time Markov Chain modelling the state space and the possible transitions among them.