One side positioning is useful to overcome mechanical inaccuracies in the spindle. Final
positioning of the axis is always done from a higher to a lower position. So when the axis
moves from a high to a low position, positioning is done immediatly. When the axis moves
from a low to a high position, the axis will move to the overrun position (= programmed
position +OR). After that, the axis starts moving in the opposite direction and positioning
takes place.
When the difference between the new programmed position and the actual position is smaller
then BSS the axis is always moved to the overrun position first, also in case of two side
positioning.
Choosing 1-side or 2-side positioning is done with the parameter ‘Spindle allowance’.
2.3.3. Unipolar system
A unipolar system is a modified AC system. Normally, the analog output can be used for AC
control: positive voltage (one or two levels) for one direction, negative voltage for the other
direction.
In a unipolar system the output voltage is always positive, the movement direction is indicated
by digital outputs. This is the only difference between standard AC implementation and
unipolar AC implementation.
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