3. Drive functions
3−10
Festo P.BE−CPX−CMA X−CONTROL−EN en 0908NH
3.1.3 Standstill control
Standstill control starts by ending a positioning task (MC).
There is a switch from position to force control to keep the
drive safely at its standstill position. Here, the force currently
applied to the piston is measured and is specified as a set
point for the force control. Due to pressure compensation
operations,
the force for the setpoint specification is not
measured directly after the standstill condition has been re
ached, but:
200 ms afterwards or
when the change in the actual force exceeds a certain
value (> 25% of the frictional hysteresis).
When switching from position to force control, the drive is
under standstill control.
If
the drive exits the tolerance window for the standstill condi
tion while under standstill control, which can be caused by
external forces, the position control is reactivated until the
switching condition for the standstill control has been re
ached again.
Attention: At the end of a positioning task, the drive comes to
a standstill
due to static friction. For this reason, the standstill
force can also vary in the range of the static friction. The force
which is displayed at standstill therefore varies from stroke to
stroke.
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