A separate acceleration can be set for the start with ud_AccStart_s. ud_Acc_s is used once the setpoint value is reached. If you would like to start the virtual master axis without a ramp, for example, i.e. to reach the selected velocity immediately after the start, but then change the velocity via a ramp, you can use ud_AccStart_s with maximum acceleration. This is possible when the slave axes start from a rest state due to the selected technology, e.g. with cams.

The virtual master axis can be stopped in three different ways.

1. The setpoint velocity is set to 0 and the master axis ramps down with the set deceleration.
2. x_Start is set to FALSE. The axis brakes with ud_DecStop_s and stops at the stop position ud_StopPos.
3. x_StopRapid is set to TRUE. The axis stops immediately with the deceleration ud_DecRapid_s.

If you would like to use the virtual master axis to couple Motion Control function modules such as MC_GearIn or MC_CamIn, you must specify a resolution to create the reference of user units per MC_Periode. This resolution is specified per break, e.g. in 360°/1 MC_Periode or 54,554 mm/1,000 MC_Periods.

If you use the virtual master axis with function modules from the technology library, such as TB_SyncLin or TB_SyncRot, you do not need to specify the resolution, as these function modules work with user units.

To make pre-control calculations and the like possible, the function module also outputs the current velocity and target velocity in user units, the remaining acceleration time in ms and the respective current brake time (based on ud_DecStop_s) until a standstill is reached. These values can be used when employing the TB_TimeToTravel function module or the cam module with dead time compensation TB_CamSwitch.

Required processing time measured with BM4_O_PLC01:

Without resolution/without period:             141 µ
Without resolution / with period:                152 µs
With resolution / without period:                161 µ
With resolution / with period:                     172 µs