Siemens SINUMERIK 840Di Function Manual page 450

Detailed Description
2.5 Optimization of the control
Stability risk
The expanded position controller algorithm will reduce the risks that a stable control admits
only a rather poor setting of the gain, or that the position control loop does not remain stable
despite the effective extensions, to a minimum.
Supplementary conditions
The functional expansion is available for all control variants.
The low-pass filter is only activated if dynamic stiffness control is inactive:
MD32640 $MA_STIFFNESS_CONTROL_ENABLE = 0.
If the low-pass filter is active, the modeled following error is larger than usual during
acceleration phases.
It can, therefore, be necessary to increase machine data:
MD36400 $MA_CONTOUR_TOL
above the standard value,
in order to prevent activation of axial contour monitoring (alarm 25050).
If the adjustable "dead zone" of the position controller retains its standard setting:
MD32960 $MA_POSCTRL_ZERO_ZONE = 0,
this corresponds to an input value, which is the same size as the current encoder fine
resolution.
Therefore, the standard setting is compatible with earlier software versions.
If the "dead zone":
MD32960 $MA_POSCTRL_ZERO_ZONE
is configured to be larger than the zero-speed tolerance:
MD36030 $MA_STANDSTILL_POS_TOL,
zero-speed monitoring (alarm 25040) could be activated on termination of a positioning
process.
If the "dead zone":
MD32960 $MA_POSCTRL_ZERO_ZONE
is larger than the exact stop limits:
MD36000 $MA_STOP_LIMIT_COARSE,
no exact stop signals are output.
This can lead to activation of position monitoring (alarm 25080)
and prevent block change.
2-76
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0