Inductive message transmission

from Wikipedia, the free encyclopedia
IMU sign and coil at the Kaiserstuhlbahn .

The inductive signaling transmission (IMU) is a train control system which is used mainly for trams.

The system is widespread across Germany and was procured in many places as a replacement for the outdated contact wire contacts (banned in Germany since 1996). Systems of a similar design also exist in (mainly western) countries, but in Eastern Europe, for example, contact wire contacts are still available in many places. The information transfer is carried out by inductive coupling of transmit and receive coils , which are mounted on the vehicle and between the rails and are often referred to as "magnet". The areas of application of the IMU mainly include three areas:

Travel lock

The purpose of the driving lock is to bring the vehicle to a standstill if signals indicating stopping are passed by by triggering an emergency brake in such cases . In addition to signals, turnouts can also be equipped with them; In this way, in the event of a malfunction, the vehicle is safely stopped in front of the switch. Since trams do not reach high speeds (max. 70 km / h on sight) and high braking decelerations (over 2 m / s²), this is the only backup. Since only one piece of information has to be transmitted (automatic braking yes / no?), The system is kept simple and can be triggered for testing purposes in the workshop with an appropriately prepared piece of sheet metal.

Inductive point control (IWS)

This part of the system is used to set the points according to the route of the train. This is necessary because there are usually no signal boxes in tram networks due to driving at sight. In order to make the driver's work easier, the most frequent routes (normal line journeys and also the regularly required entry and exit journeys to the depot) are already preprogrammed, so that the driver only has to enter the appropriate identifier into the control unit and the points are then set according to this identifier become. Alternatively (e.g. for diversions) it can also be controlled manually, in this case a button for the desired direction of travel usually has to be pressed while passing the point control magnet.

Depending on the preference of a transport company, the driver can generally only set the switch manually, who then has to press the corresponding setting button for the desired direction of travel each time he approaches a switch that is being driven across.

Signal control

This area can be subdivided into three subsections:

Pure train protection

Since trams usually run on sight, systems of this type are less common. However, it can be used for single-track sections of the route or to circumvent a speed limit in places with limited visibility. The relevant route areas then work in a similar way to an interlocking in self-setting mode , with the corresponding route being set when the vehicles log on to the system (taking into account the IWS identifier, if necessary).

Level crossing protection

Easy intersections with road traffic - d. H. not in combination with a traffic light system (LSA) at a street crossing - work in a similar way to driver-monitored level crossings (BÜ) on "real railways". When passing the switch-on magnet - track contacts that work separately from the IMU are less common - the level crossing safety system is activated. In contrast to railroads, the signal covering the intersection, which can be a bar or monitoring signal, only starts moving when the road signals are red and a certain clearance time has passed. In order not to hold up the trains unnecessarily, this switch-on time is taken into account for the approach route. When the train passes the switch-off magnet, the train is logged off from the system and the level crossing is set to its basic position.

Control of a traffic light priority circuit

In order to reduce the waiting times at more complex intersections (BÜ + normal LSA ), a so-called traffic light priority circuit has been installed in many cities, i. H. the trams are only taken into account as required and are not given e.g. every 40 s for 10 s travel. Here, too, the IMU takes on the task of registering trams with the LSA. Normally, a “green phase” for the tram is then inserted at the next possible point, with a certain delay at stops in order to provide time for the passenger change. Under certain circumstances, the IWS identifier can also be taken into account, for example at intersections with the possibility of turning off the tram, or in order to request a passage without stopping for express trains at stops at an intersection.

Web links