Technical data

Technology objects
CPU 317T: Technology Functions
A5E00251798-03
3-3
3.1.2 Axis types
You can set two different types of axes in your axis configuration. The axis type
(linear or rotary, each also as modulo axis) is in essence determined by
mechanical conditions and by the units in which the axis-specific variables are
computed, for example, the position or velocity.
• Linear axes
Linear axes are usually configured where the traversing range is mechanically
limited. The position profile is linear within the traversing range. Basic physical
units of the motions are the length units such as millimeter.
• Rotary axes
Rotary axes are usually configured for a rotary motion range. The traversing
range is not limited mechanically. Basic physical units of the motions are
rotatory units such as degrees. Rotary axes are usually also configured for
operation as modulo axis.
Linear and rotary axes can be configured for operation as modulo axes. In this
case, the axis position is defined (reference and actual values) within a range
which is determined by the modulo start value, as the low limit, and by the modulo
start value plus modulo length as high limit.
Example: A rotary axis with a traversing range from 0° to 360" has a modulo start
value of 0°, and a modulo length of 360°. The axis position is reset to 0° when it
exceeds its high limit of 360°. When it passes the low limit (0°), the axis position is
set to the modulo start value plus the modulo length (360°). The position profile is
linear within the modulo length.
Note
The position value increments continuously when linear or rotary axes are
operated as infinite axes driven only in one direction (axis not configured as
modulo axis). The variables representing the setpoint and actual position values
are of the data type REAL, at a resolution of 23 binary digits (mantissa). The effect
is, that the axis positioning accuracy deteriorates with increasing position values.
Hence, you should preferably use modulo axes for infinite axis mode, or reset the
position to zero at appropriate times.