BBT / SBT

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Block Brake Timer:

Calculation of block brake time automatically to decelerate linear from enter to in.

BBT Tab


The BBT records can be sorted by clicking on one of the columns headers.

:!: Changing the settings may not be saved when the locomotive is still in auto mode


BBT

The Block Brake Timer for this loco is only active when the BBT-option for this loco in the details tab is set and the loco enters blocks with the BBT-option set.

Steps

The number of steps preset to use for BBT.
The actual number of steps in the BBT records can differ from this number; All depends on the enter speed.
After the learning process is finished the number of actual steps should be equal.

Start interval

Default 10; Range 10…250.
This value is used as start for a new BBT record and will be used as the initial timer between the steps.
It may be, that the default 100 ms, 10 x 10 ms, is to low to get a fast learning curve.
The interval is an approximately value and is Operating System dependent.

Max. Difference

Longer differences will be reduced to this max. to avoid unusable values in case a train stops or is derailed between enter and in.
The default value is 250 = 2.5 Seconds.

Correction

After each stop in a block the BBT is re-calculated. This percentage of the difference is used as correction.
25% is the default value which has been proven to be a good choice.
Use a higher value to speed up the learning curve. 100% can also be used.

Use

This option determines which record key will be used to create and to lookup.

Block

For the block in which the loco stops a BBT record is created, independent of the entry side of the block.
Note: The From Block column is in this case irrelevant.

From Block

For each from block a separate BBT record is created.
:!: This method does not function if the loco has the Free previous block on enter active.

Route

For each route a separate BBT record is created.

Speed

For each speed a separate BBT record is created.
Note that Rocrail only knows the locos speed setting and not the locos absolute speed at enter. This is only relevant if the loco is still accelerating or decelerating when it passes the enter sensor.

Delay

Number of 10ms cycles before activating BBT.

This value can be set by the user and is for fine tuning on the brake point only.
The default value “0” will start the BBT immediately on enter.
:!: Use with care or leave it at zero.


Calculation List

To block

The block for which the calculation has been made.

Deceleration time

The deceleration time is in units of 10ms.
This is the time between enter and in and will be divided by the number of steps.

Steps

The steps column shows how many steps could be counted for last run between enter and in.
e.g. if the loco had stopped far beyond in the value will be less than target.

Count

The number of calculations for this BBT record.

Fixed

No corrections will be written in this BBT record if set to fixed.
This can be useful in order to prevent an already determined optimum setting from being inadvertantly changed automatically.
The time in which a loco brakes to V_min can be altered intentionally and set.

Generate IN

At the end of the intervals an IN event will be generated and before all other IN events will be ignored.
This can be used to create a loco dependent stopping point.

Center train

If the Block has Length and Center train set, this option can be used to calculate the interval for stopping the train approximately in the center/front/rear of the block platform. An IN event will be generated.
The Fixed option of the BBT record must be set.

:!:Notice:
before setting this option the BBT record have to be learned correctly!
Only after that set the option 'fixed' and only after that set the option 'center train'!
The lenght of the train (loc and waggons) and the block must be set: Lenght !
Further needed:
The loc lenght, waggon lenght and the Bloclenght!
The Block option center trains musst be set.

|Plus-------------------------Block--------------------------Minus|
|-OffsetPlus--|--------------Platform--------------|--OffsetMinus-|
1             2                 3                  4              5

1 = ENTER sensor
2 = Start of platform  -> REAR
3 = Center of platform -> CENTER
4 = End of platform    -> FRONT
5 = IN sensor

Train halt positions:

  1. No → The front end of the train at 5
  2. Center → The middle of the train at 3
  3. Front → The front end of the train at 4
  4. Rear → The rear end of the train at 2


Updates

No BBT updates are received if Monitoring is off. In this case closing the dialog with OK could erase existing BBT lines.

Add

A BBT line with the set parameters will be added to the list.

Delete

Delete a selected BBT line.

Copy

A copy of the selected BBT line will be added to the list.

Modify

The modified parameters are inserted in the BBT line.

Delete all

Delete all BBT lines.

Export

Export all BBT lines in a XML file.

Import

Import BBT lines from a XML file.

Fix all

If max. 1 line is selected all lines will be fixed.
If more then one line is selected the fixed flags will be inverted.


Functional description

  • It needs multiple stops in a block for (re-)calculating a right interval; The first times it won't fit.
  • At every stop block it is re-calculated.
    • Longer differences will be reduced to the max. difference to avoid unusable values in case a train did stop or derailed between enter and in.
  • The brake step is: ( V_enter - V_min ) / steps.
  • The calculation is for each block and will be saved in the Plan/Loco XML file.
  • The enter and pre2in events do not adjust speed.
  • If the BBT is too short the loco will run at V_min until in.
  • If the BBT is too long the loco will run with a higher speed than V_min until in; The loco could run over.
  • After editing the loco Train the previous calculated BBT will probably no longer fit because of the changed load; Extra learning stops are needed.
  • BBT is only for blocks without external stop.
    • Staging blocks with In event at train length is regarded as a block with external stop.


Advice

  1. Do not set the decelerate decoder CV 4 to zero.
  2. Do not use enter2in but a real enter and a real in sensor.
  3. The use of event timers will not lead to a stable interval; Reset them to zero!
  4. Use as less brake steps as possible to reduce communication overhead; 10 steps is default and a good choice.
  5. Use at least 28 decoder steps; Better are 128.
  6. To get used to this function it is advisable to set a linear speed curve in the decoder.
  7. The longer the block, or the distance from the start of braking to in, the more steps and higher CV4 value should be set.
  8. BBT needs extra CPU power so disable BBT if its not needed.


Graphic


A Enter speed.
B BBT steps; In this example 10.
C Enter event; First BBT step.
10 Last BBT step.
D In event; Step down to zero speed.
E Zero speed; Loco is in wait or idle mode.

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