Siemens SIMATIC ET 200S - Page 319

1PosUniversal/Digital
7.5 Fundamentals of Controlled Positioning Using Rapid/Creep Feed
ET 200S Positioning
Operating Instructions, 05/2007, A5E00124871-04
319
Definitions
Term Explanation
Operating range Defines the range, which you set for a particular task by means of the hardware limit
switches.
At an SSI encoder the operating range is limited additionally by the range covered by the
SSI encoder.
You enter the encoder range in the parameters for:
• Number of increments
• Number of rotations
Encoder range = Number of rotations * Number of increments
Maximum operating range:
• Linear axis - max. 0 to (encoder range -1)
• Rotary axis from 0 to (encoder range - 1)
At an incremental encoder the operating range is limited to:
• Max. 0 to 16,777,215 increments at a linear axis
• 0 to the assigned parameter end of a rotary axis at a rotary axis
Switchover difference Defines the distance from the destination at which the drive is switched over from rapid feed
to creep feed.
Switchover point Defines the position at which the drive is switched over from rapid feed to creep feed.
Switch-off difference Defines the distance from the destination at which the drive is switched off.
If the switch-off difference ≥ the switchover difference, there is no switchover point. There is
no change from rapid feed to creep feed.
Switch-off point Defines the position at which the drive is switched off.
The 1PosU reports the end of the run at this point.
Start position Defines the position of the drive within the operating range from which the run is started.
If the start position is within the switch-off difference, the drive is not triggered. The 1PosU
reports the end of the run at this point.
If the start position is within the switchover difference, the run is only executed in creep feed
mode.
Target XE "Target" Defines the absolute or relative position of the axis approached during positioning.
The destination is the position to be reached on an axis during a run.
In the case of an absolute run, you specify the destination directly by means of your control
program.
In the case of a relative run, the destination is calculated from the start position and the path
specified in the control program.
If you want to find out how accurately you have reached the destination, you have to
compare the actual value with the position specified.
Linear axis XE "Linear axis" Defines the axis type with a limited operating range.
It is limited by the following:
• The encoder range
• The numeric range that can be represented (0 to 16 777 215 increments)
• The hardware limit switch
Rotary axis Defines the axis type with an infinite operating range.
This includes resetting the axis position to 0 after one rotation (assigned parameter end of a
rotary axis at an incremental encoder or parameterized encoder range at an SSI encoder).
Minus direction If the drive moves in the minus direction, the actual value displayed is decreased.
Plus direction If the drive moves in the plus direction, the actual value displayed is increased.