Table of Contents
Train movement related features and concepts
The track network of the WinterTrain will be formed by:
- Track sections of various length
- Points, diverging trains in one of two directions
- Buffer stops and end of track
- Road level crossings
Within the network one particular driving direction will be defined as direction up. The opposite direction will be called direction down.
In order to simplify implementation of data structures and algorithms in the RBC/IL, the possible track topology will be limited:
- The track network has to be connected, i.e. all tracks must be reachable from any other track. This excludes a track network, having “islands” of tracks.
- Direction has to be unambiguous, that is: direction up has to remain direction up when driving in the network. As a consequence of this, a so-called “turning loop” cannot be realized.
Train positioning and direction of movement
In order for the interlocking to e.g prevent collisions and the RBC to provide movement authority to trains, the position of each train has to be established with a certain accuracy.
The WinterTrain OBU will establish the actual position of the train by means of balises, driving direction and distance. A balise is a transponder mounted in the track. When a train passes a balise, the train will read the telegram conveyed by the balise and by this get a reference to where the train is. Each balise will provide a unique ID, but otherwise no specific information. The ID and location of each balise within the track network will be known to the interlocking and RBC. To simplify the balise system only single balises will be used.
The actual driving direction will be derived from the polarity of the DC voltage in the rails - i.e. whether the polarity at the right side wheels are positive or negative. To ensure an unambiguous definition of directions and distances, nominal driving direction up (and hence down) will be defined for the track layout. The polarity of the traction voltage of the rails will be arranged so that the right side rail as seen in direction up will be positive.
Distances will be measured by counting wheel turns. In the RBC number of wheel turns can be converted to a distance in cm based on the wheel diameter of each train.
Actual train position will hence be expressed as a relative distance - with sign - from the latest read balise. A positive value will indicate, that the train is located at a position further away in direction up from the latest read balise. A negative value will tell, that the train is located in direction down, compared to the balise in question.
Nominal driving direction up and down are not to be confused with the train moving directions forward and backward. The former is statically defined for the track network, while the latter is a dynamic property of a moving train. The train has a defined front end and compared to this, the train is said to be moving either forward or backward. Hence if a train is located with its front end pointing in direction down, it will be moving backwards when driving in direction up.
Every few seconds the OBU will transmit a position report to the RBC indicating the current position of the train.
The OBU will not keep the current position during power down or OBU reset. After power up or re-start, the OBU will send a position report indicating the lack of valid position information. In this situation, the driver has to run the train to the next balise in mode SR or SH.
The RBC will keep the most recently received train position for a specific time (10 - 30 seconds). If the OBU restarts within this period, the RBC will assume this position as actual position of this train.
If the position stored in the RBC is obsolete, the OBU will get an order to move at low speed to the first read balise.
If all trains within an RBC has no valid position, they will be requested to find the first balise by moving in the same direction.
Mode authorization and train mission
The operational mode of each train will be managed in the following way depending on the actual operational situation of the (model) railway. For each train the operator will be able to mark which modes the train is allowed to operate in. In addition to this, mode SR can as well be allowed by a dedicated switch in the OBU (mostly for test runs without the RBC).
For mode SH the shunting area assigned to the train has to be clear of other trains in order for the RBC to allow mode SH.
When the driver selects a particular mode (and the direction selector is in position Neutral) the OBU will send a Mode request for that mode to the RBC. The RBC will then grant or reject the mode. If the requested mode is granted this is indicated to the driver via the “Mode authority indicator” being off.
If a particular mode is not allowed according to the above, a request from the train driver for this mode will be rejected. This will be indicated to the driver via the “Mode authority indicator” being Red.
Mode N is implicit allowed and requires no authorization form the RBC.
Each train will be authorized by the RBC to move depending on the granted operational mode and the operational situation of the railway. The mechanism for getting a movement authority (or MA for short) is as follows:
Mode SR The authority is implicit given by the mode. The movement of a train i mode SR is not limited by the system. The driver has the responsibility of the train.
Mode SH The OBU will get an MA indicating the maximum allowed speed for shunting. The driver can move the train within a predefined shunting area specified by OBU data.
Mode FS When the driver selects a driving direction, the OBU will send an MA request for that driving direction to the RBC. The RBC can then grant a movement authority indicating how far and how fast the train can move. Before a moving train has to break due to reaching the end of the current MA, the OBU will send a new MA request. If conditions allows the RBC will then extend the MA.
Mode ATO The RBC can grant movement authorities. The ATO function of the OBU will then drive the train accordingly. Before a moving train has to break due to reaching the end of the current MA, the OBU will send a new MA request. If conditions allow the RBC can then extend the MA.
Give various conditions are fulfilled the RBC will issue an MA to a particular train.
For a train in mode SH the MA authorizes the train to move with a certain maximum speed. The area in which the train can move is specified by other means. The MA includes:
- Maximum driving speed
- Train ID
For a train in mode FS or ATO the MA authorizes the train to move from its current position to a specific new position called “End of authority” or EoA for short. The MA includes:
- Driving direction (up or down)
- Location of EoA in terms of a signed distance from a specific balise
- Maximum driving speed
- Train ID
The MA will be based on the latest train position known by the RBC. As a moving train may have read another balise since requesting an MA, the OBU has to keep track of the position of the train according to more balises.
An MA received by a train remains valid until:
- The train has reached EoA within a certain margin or
- The driver selects driving direction Neutral or
- The driver selects a different mode
The RBC can withdraw an MA, in which case the train has to stop.
In mode FS the OBU will supervise the traction power and driving direction according to the current Movement Authority given by the RBC. If no MA is available traction will be disabled and the train will stop.
In mode SH the traction will be supervised against a maximum speed provided by the RBC in the MA following the authorization to operate in mode SH. Further both traction and direction will be supervised, in order to prevent the train from leaving a predefined shunting area.
In mode SR traction and direction is not limited; the driver have full responsibility of the train.
Automatic train operation
In mode Automatic Train Operation (ATO) the train will run automatically according to the actual Movement Authority (MA) given by the RBC. The speed will be commanded to maximum whereby the actual speed will be controlled by the supervision system and hence follow the maximum allowed speed in the MA. The driving directions will be as allowed by the MA.
A shunting area is an area in which a train may operate in SH mode. The extent of the shunting area will be statically defined in the OBU. It is defined by a list of shunting area borders, each of which is specified as a signed distance from a balise. This list will be part of the configuration data of each train. In a later version this area specification may be updated dynamically by the RBC.
Each border specification will provide:
- Balise ID
- Distance with sign from balise to shunting area border. A positive distance indicates that the border is located in direction up compared to the balise, while a negative distance indicates that the border is located in direction down.
The balise of a border specification must per definition be located inside the shunting area. Several border specifications (and hence several balises) can point at the same border, increasing the chance that the OBU will observe the border.
When the OBU reads a balise, this balise will be compared against the border list. If the current balise is found in the border list, the train is near a border and must observe this border. The index of the balise in the border list will be stored. When the train moves, the distance from the current balise (equal to the border balise) will be compared with the border distance. When passing the border, the OBU will start braking the train. Braking distance has to be taken into consideration when engineering the borders.
If the current balise is not in the border list, the train can continue without checking the distance.
If a train is located outside the shunting area and current balise is a border balise, mode SH will be rejected by the OBU. If the current balise is not in the border list, mode SH will be accepted, assuming the train is within a shunting area.
In any case, mode SH has to be allowed by the RBC.
The signaler may issue an overall Emergency Stop command whereby the RBC will send an Emergency Stop MA to all trains.
When a train receives an Emergency Stop MA the current MA will be deleted and the train will stop.