Commissioning
EL70x1 157Version: 4.4
identically, as long the actual position is between 359° and 1°. If the position exceeds 0° by less than 1°, the
axis is re-positioned in positive direction at a modulo start. In both cases, a target position of 0° therefore
leads to minimum movement to exactly 0°. A target position of 360° leads to a full turn in both cases.
For values that are within the window range, the modulo tolerance window can therefore lead to movements
against the specified direction. For small windows this is usually not a problem, because system deviations
between set and actual position are compensated in both directions. This means that the tolerance window
may also be used for axes that may only be moved in one direction due to their construction.
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 0x8020:0F) is always taken into account in the "nor-
mal" types of modulo positioning. However, this is less desirable in some situations. In or-
der to eliminate this "disadvantage", the comparable start types "MODULO_SHORT_EXT",
"MODULO_PLUS_EXT", "MODULO_MINUS_EXT" and "MODULO_CURRENT_EXT" can
be used, which ignore the modulo tolerance window.
The following table shows examples of modulo positioning with less than one revolution.
Modulo start
type
Absolute start po-
sition
Modulo target po-
sition
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_MINU
S
90° 0° -90° 0° 0°
MODULO_MINU
S
90° 360° -450° -360° 0°
MODULO_MINU
S
90° 720° -810° -720° 0°
MODULO_SHOR
T
90° 0° -90° 0° 0°
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 behavior described in the example 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.
To Next Page
Loading...
