Prepare process

Figure 11.18 shows the prepare process.

Figure 11.18: The prepare process.

• First the type of the SB is found. If it is a point SB it is tested if the point is in the correct position. If so, response is returned to the TCC.

Otherwise nothing further is done.

• If the SB is a crossing SB it is tested if the barriers are down. If so,YES response is returned to the TCC. Otherwise nothing further is done.

• If the SB is a plain SB or an end SB,YESis immediately returned to the TCC.

88 Control system design

Chapter 12

Glossary

This chapter presents a glossary that uses figure 12.1 as basis for the explaina-tion of terms. The figure shows a part of a railway line. The circles denotes switch boxes (SBs)and the lines denotessegments. The dots denotes that more segments could be placed here (but no junctions).

Figure 12.1: A part of a railway line

SB Aswitch boxis a controlling unit located at the boundary betweensegments (described in section 3.7). SB1,SB2,SB3and SB4areswitch boxes.

TCC A Train Control Computer is a computer in a train. It is used in the control system to reserve segments before entering them, stopping the train when it tries to enter a segment it has not reserved etc. (see also section 3.4). T1is a train. TheTCC inT1is also denotedT1.

Line segment Aline segment is a segment in asingle line. S1andS2areline segments.

Branch segment Abranch segment is a segment that connects two junctions and is a branch of both junction (remember a junction always has two branches), i.e. the stem of a junction is not abranch segment. S0a,S0b, S3aandS3barebranch segments.

90 Glossary

Single line A single line is a number of coherent segments on which trains are allowed to move in both directions. The line connects either the stem of two junctions, the stem of a junction and an end station area, or two end station areas if no junctions exist in the railway line. The segments betweenSB1toSB3form asingle line.

Single line guard A single line guard is aSB that is located at the end of a single line. I.e. the SB is either a point SB or anend SB.SB1,SB3and SB4aresingle line guards.

Reservation A reservation in general is a permission to enter a part of the railway line. In the SBs there are three different kinds of reservations, which are line-segment reservations, branch reservations, and line reser-vations. The TCCs only knows one kind of reservations called segment reservations.

Line-segment reservation A line-segment reservation is a reservation of a certainline segment. Thereservationis given when the segment has been prepared. The only situation for a denial of aline-segment reservation is, if the segment for some reason could not beprepared.

Branch reservation Abranch reservationis areservation of a certainbranch segment.

Line reservation Aline reservation is areservationof a certainsingle line in a certain direction.

Segment reservation Asegment reservationis areservationof a certain seg-ment in a certain direction. This notion is only used in the TCCs.

Request message Arequest message is either a line-branch request or a seg-ment request.

Line-branch request A line-branch request is a combined request for a line reservation and a branch reservation send from one single line guard to the opposite single line guard of thesingle line. If thesingle line ends at an end station area there is no branch segment. Therefore only the line reservation is requested.

Segment request A segment request is a request for a segment reservation send from aTCC to aSB.

Response message A response message is either aline-branch response or a segment response.

Line-branch response A line-branch response is a response to a line-branch request telling whether both a line reservation and a branch reservation could be obtained or not. If the single line ends at an end station area there is no branch segment. Therefore the line-branch response only tells if a line reservationcould be obtained or not.

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Segment response A segment response is the response to a segment request telling whether asegment reservation could be obtained or not.

Dereservation message Adereservation message is either a branch dereser-vation message, a line dereservation message or a line-branch dereserva-tion message.

Branch dereservation message A branch dereservation message is a mes-sage telling aSB to cancel itsbranch reservation.

Line dereservation message Aline dereservation messageis a message telling aSB to cancel itsline reservation.

Line-branch dereservation message A line-branch dereservation message is a message telling a SB to cancel its branch reservation and its line reservation.

Prepare a segment When a train is to enter a new segment the segment needs to be prepared. If theSB between the twosegments is apoint SB, preparing the new segment means to switch the point so that the point is connected to the correct branch. If theSB between the twosegments is a crossing SB, preparing the new segment means to close the barriers and turn on the signals at thecrossing etc. according to the algorithm (see section 9.4). If theSB between the twosegments is aplain SB or anend SB nothing is done when the segment is prepared.

Deprepare a segment When a train has left a segment, the segment must be deprepared. The only time something happens at a depreparation is when the passed SB is a crossing SB. Then the crossing should open again. If a point is switched when a segment is prepared, the point is shifted back when the segment is deprepared.

Reservation point Areservation point is a point at a segment (do not confuse this with the point at a junction). The point is not physically visible and is expressed as a distance to the end of the segment. When the train passes this point (and not before), theTCC sends a reservation request for the next segment to theSB between the segments. A segment has a reservation point in both directions. A train passes thereservation point before it passes thebrake point.

Brake point Abrake point is a point at a segment (do not confuse this with the point at a junction) at which theTCC should brake the train if it does not have areservation for the next segment. The point is not physically visible and represents a distance to the end of the segment. A segment has abrake point in both directions. A train passes thereservation point before it passes thebrake point.

Point ticks Point ticks denotes the number of seconds it takes for a point to switch from one branch to the other.

92 Glossary

Signal ticks Signal ticksdenotes the number of seconds the signal at a crossing is turned on before the barriers begin to close. In section 9.4 signal ticks are shown in the state diagram assignals only.

Barrier ticks Barrier ticks denotes the number of seconds it takes for the barriers at a crossing to either close or open. In section 9.4 barrier ticks are shown in the state diagram asbars moving.

Chapter 13

GUI design

This chapter briefly describes the overall view of graphical user interface (GUI) without going into details. The design conforms with the simulator requirements described in chapter 7.

All the figures showing the GUI designs can be found in appendix A.

13.1 Train simulator

Figure A.1 shows the design of the train simulator. The two menus are shown as they would appear when they are expanded.

The figure shows how the layout of the railway line are placed in the top. The ESAs are shown as green rectangles. SBs are shown as circles, segments as lines, and trains as colored pentagons placed on segments.

At a junction both branch segments are shown and the position of the coherent points are shown using small colored rectangles above and below it. A green rectangle denotes that the point is positioned at the branch segment near the rectangle. Red means that the point is at the opposite branch and orange means that the point is in an intermediate position.

The crossings are shown as two parallel vertical lines enclosing a SB (circle).

The colored rectangles (green, orange or red) above and below the crossing show whether the barriers are closed or not. Red means that they are open, orange that they are moving, and red that they are closed.

Below the layout of the railway line, rows of buttons are showed. These corre-sponds to the entities of the railway line. When one of the buttons is pressed the static, dynamic and control properties of the selected entity are showed below the buttons.

94 GUI design