BECKHOFF EL7037 - Manual (Page 151)

Commissioning
Modulo positioning by less than one turn
Modulo positioning from a starting position to a non-identical target position is unambiguous and requires no
special consideration. A modulo target position in the range [0 ≤; position < 360] reaches the required target
in less than one whole turn. No motion occurs if target position and starting position are identical. Target
positions of more than 360 ° lead to one or more full turns before the axis travels to the required target
position.
For a movement from 270° to 0°, a modulo target position of 0° (not 360°) should therefore be specified,
because 360° is outside the basic range and would lead to an additional turn.
The modulo positioning distinguishes between three direction specifications: positive direction, negative
direction and along the shortest path (MODULO_PLUS, MODULO_MINUS, MODULO_SHORT). For
positioning along the shortest path, target positions of more than 360° are not sensible, because the
movement towards the target is always direct. In contrast to positive or negative direction, it is therefore not
possible to carry out several turns before the axis moves to the target.
Attention
Only basic periods of less than 360° are permitted
For modulo positioning with start type "MODULO_SHORT", only modulo target positions
within the basic period (e.g. less than 360°) are permitted, otherwise an error is returned.
Note
Positioning without the modulo tolerance window
The Modulo tolerance window” (Index 8020:0F [ } 183]) is always taken into account in the
“normal” types of modulo positioning. However, this is less desirable in some situations. In
order to eliminate this "disadvantage", the comparable start types "MOD-
ULO_SHORT_EXT", "MODULO_PLUS_EXT", "MODULO_MINUS_EXT" and "MOD-
ULO_CURRENT_EXT" can be used, which ignore the modulo tolerance window.
The following table shows some positioning examples:
Modulo start
type Absolute start
position Modulo target
position Relative travel
path Absolute end
position Modulo end
position
MODULO_PLUS 90° 0° 270° 360° 0°
MODULO_PLUS 90° 360° 630° 720° 0°
MODULO_PLUS 90° 720° 990° 1080° 0°
MODULO_MINUS 90° 0° -90° 0° 0°
MODULO_MINUS 90° 360° -450° -360° 0°
MODULO_MINUS 90° 720° -810° -720° 0°
MODULO_SHOR
T 90° 0° -90° 0° 0°
Examples of modulo positioning with less than one revolution
Modulo positioning with full turns
In principle, modulo positioning by one or full turns are no different than positioning to an angle that differs
from the starting position. No motion occurs if target position and starting position are identical. For a full
turn, 360° has to be added to the starting position. The behaviour described in the example [
} 150] shows
that special attention must be paid to positionings with whole revolutions. The following table shows
positioning examples for a starting position of approximately 90°. The modulo tolerance window is set to 1°
here. Special cases for which the starting position is outside this window are identified.
Modulo start
type Absolute
start posi-
tion Modulo
target po-
sition Relative
travel path Absolute
end position Modulo end
position Note
MODULO_PLUS 90.00° 90.00° 0.00° 90.00° 90.00°
MODULO_PLUS 90.90° 90.00° -0.90° 90.00° 90.00°
MODULO_PLUS 91.10° 90.00° 358.90° 450.00° 90.00° outside TF
EL70x7 151 Version 1.0