The "Radio-Controlled Railroad Crossing"-system describes a decentral and autonomic closing and opening of a railroad barrier at railroad crossings if a train is nearing this crossing. This is it, that this system (illustrated in the picture above) extends the railroad barrier with a control system for closing and opening the barrier (Control_Track) and the train with a control system for accelerating/decelerating (Control_Train_AccDec) the train as well as determining the position of the train on the track (Determine_Train_Pos). Both, the track and the train exchange these information via a radio communication (Comm_Rad).
In this system, the train continously tracks its position by the Determine_Train_Pos-component. If the train gets near a railroad crossing (specific point Pos_Start) it triggers a signal via Comm_Rad for closing the barrier. If Control_Track-component receives this signal it start closing the barriers. This closing-process requires several seconds up to minute because light and sound signals for warning road participants has to be acitivated before closing the barriers finally. If the barriers are closed, the Control_Track-component responds to the train with a receive-message via the Comm_Rad-component and the train can pass the crossing. If the the train does not receive these response-message up to the point Pos_Stop the Control_Train_AccDec-componet will immmediatly start the emergency brake of the train. After the train pass the crossing or after a maximum allowed closing time (tracked by time Ti_Track) the barriers are opened again.
In the corresponding SAML-model depicts the barrier and the train in seperate components.
Within the barrier component a state machine handles the behavior for opening and closing process if the radio communication triggers the closing signal. Moreover in a subcomponent Physic some failure components illustrate some physical failures of the barriers e.g. actuator fails to properly close or open the barrier.
Within the train component a control-component manage the different states of the train as "wait for closing" or "emergeny brake". Changing these states influences another subcomponent Physics of the train which deals with the trains position, velocity as well as its acceleration. For example by setting the trains state to "emergeny brake" the acceleration switches to a negative value and the velocity decreases.