Project 06/2005 Danaher Motion
70 Rev E M-SS-005-03l
The MC checks realtime limits each SERCOS update cycle. Changes in
these limits affect current operations. VELOCITYFEEDBACK is checked
against VELOCITYOVERSPEED in every SERCOS cycle.
Drive limits are imposed by the SERVOSTAR CD drive. Changes in these
limits affect current operations. For example, ILIM limits the peak current that
is output by the drive. These limits are imposed independently of the position
and velocity commands issued by the controller.
3.9.1. Position Limits
There are several limits in the MC related to position:
POSITIONMIN or PMIN
POSITIONMAX or PMAX
POSITIONMIN (PMIN) and POSITIONMAX (PMAX) place minimum and
maximum limits on the position feedback for an axis. Set the limits with:
A1.PositionMin = -10
A1.PositionMax = 200.5
or you can use the short form:
A1.PMin = -10
A1.PMax = 200.5
Position limits must be enabled before they can operate. Limits are enabled
with POSITIONMINENABLE and POSITIONMAXENABLE. Position Units
are discussed above.
Position limits are checked two ways. First, they are checked in the motion
generator. If you command a position move beyond the position limits, an
error is generated and the move does not start. Second, they are checked
each SERCOS update cycle (generally, 2 or 4 ms). If the axis is moving and
crosses the position limit, this generates an error.
If the axis has already stopped because the position limits were crossed, the
MC does allow you to back out. In other words, you can enter commands
that move the axis back within the limits. The axis will move without
generating errors.
Position limits are continuously checked only when the drive is in master-
slave mode. Some conditions may occasionally result in the motor moving
outside PMIN or PMAX limits which are not detected by the MC. SERCOS
loop instability may also cause position errors.
You can control whether the MC watches either one or both of the limits in
position limit. To do this, set POSITIONMINENABLE and
POSITIONMAXENABLE to either ON or OFF.
A1.PositionMinEnable = ON
A1.PositionMaxEnable = ON
or, you can use the short forms:
A1.PMinEn = ON
A1.PMaxEn = ON
The default state of PMINEN and PMAXEN is off. You must enable them to
use these limits.
You should limit the maximum position error your system tolerates. You do
this by setting <axis>.POSITIONERRORMAX (<axis>.PEMAX).
