Image 7.77: Hydraulic - “position control" PosCon_TrackingError(3))
Position monitoring:
A tracking error can be set to monitor the positioning operation. If this tracking error
is exceeded due to an increased load or an error in the system, the controller
switches off and reports an error reaction.
Moreover, continuous readjustment of the position can be prevented by defining a
position window (P 2870.0 PosWindowLo, P 2870.1 PosWindowUp). When the
actual position reaches this window, the motion is stopped and the cylinder is
tensioned by switching off the directional valves. In addition, the “InWindow” bit is set
in the status word to provide feedback concerning the completion of the positioning
operation. It is important to bear in mind that the position window is turned in
dependence on the direction of the positioning operation (see Image 7.79: Position
window and position hysteresis). If no readjustment of the position is desired, it is
also possible to define a hysteresis in addition to the position window (P 2870.6
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
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7 Control
PosHysLo, P 2870.7 PosHysUp). The position controller then positions into the
position window but only corrects the position again after a departure from the set
hysteresis range.
Image 7.78: Position tracking error and position window
PosHysUp
PosHysLo
PosWindowUp
PosWindowLo
PosWindowLo
PosWindowUp
PosHysLo
PosHysUp
RefPos
x
t
Image 7.79: Position window and position hysteresis
