①
Green curve = amount
Y-axis left = absolute value of isd/isdref
②
Blue curve = phase response
Y-axis right = Phase response Isd/isdref
Legend for Current controller transfer function
7.3.3 Decoupling
The current control has a decoupling of the d- and q-axis by means of feed-forward
control of the corresponding coupling voltages. The decoupling depends on the
stator inductance P 471 MOT_Lsig and can be scaled with parameter P 434.3. This
is helpful, for example, if the inductance has been estimated inaccurately.
If the decoupling is set too high, current control is unstable.
7.3.4 Current actual value filter
A first-order digital filter (PT1) can be configured in order to smooth the measured
“isd” and “isq” actual current values. This is particularly useful when using drives
with high speeds.
NOTE
l
The control dynamic performance will be reduced when using the
current actual value filter. Using the current actual value filter is
not advisable for drives that require a high control dynamic
performance.
The current actual value filter is configured with P 1960[0] - CON_ACT_ISDQ_TF,
with the filter time constant being defined in milliseconds.
Filtered actual currents “isd” and “isq” can be visualized with scope signals 25 and
26. The unfiltered values can be visualized using scope signals “isd_unfil” (129) and
“isq_unfil” (130).
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
115
7 Control
7.3.5 Detent torque compensation
Image 7.9: Typical positioning sequence
In speed and position-controlled operation, the ripple of the torque and power
causes a current ripple in the q-current. When detent torque compensation is used,
these q-current input data are imported to a teach table in the controller (teaching
routine, learning). The compensation table is created from this (calculation) which is
then ultimately used for the feed forward control of the q-current in the controller
(compensation).
In the low speed range, these disturbance torques can be eliminated well by the
control system. In the medium to high speed range, the disturbance torques can be
reduced very well using the table-based compensation described here. In the high
