Siemens SINUMERIK 840Di Function Manual page 434

Detailed Description
2.5 Optimization of the control
To illustrate this, the difference in position between two measuring systems is generated
and injected as an additional current setpoint for the feedforward control, according to the
weighting of machine data:
MD32950 $MA_POSCTRL_DAMPING.
The function is used predominantly for axes with strong tendency to vibrate.
Functionality
The positional deviation is injected in the NC in the position controller cycle of the higher-
level position control loop in the NC.
The difference in position between a direct and an indirect measuring system is generated
and injected as an additional current setpoint, depending on the weighting of machine data:
MD32950 $MA_POSCTRL_DAMPING.
Direct measuring system:
MD31040 $MA_ENC_IS_DIRECT[1]=1
The encoder for position actual-value acquisition is connected directly to the machining
process of the machine (load encoder).
Indirect measuring system:
MD31040 $MA_ENC_IS_DIRECT[0]=0
The encoder for position actual-value acquisition is located on the motor (motor encoder).
MD32950
The function is activated via the following machine data setting:
MD32950 $MA_POSCTRL_DAMPING = 1.
It is possible to enter both positive and negative values,
which will then serve to scale the injection of the positional deviation.
Standard setting:
MD32950 $MA_POSCTRL_DAMPING = 0.
In this case, the injection of positional deviation is inactive.
Note
The weighting of machine data:
MD32950 $MA_POSCTRL_DAMPING
can be set on the basis of step responses, for example.
If the control approaches the stability limit (vibration inclination increases), then the
parameter is too large.
2-60
Velocities, Setpoint/Actual-Value Systems, Closed-Loop Control (G2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0