110
Installation and user guide
Rev: 4.0
NTT 240/460
Operation mode
Images below show tipical step of fisical closed loop system (current loop in the image at the low of graph and
speed in the image above of graph).
•
Step responce with low proporzional gain:
internal current reference, provided
by speed regulator, is too slow andlead to overshoots around the constant
condition reference, before get stability.
Note that, in correspondence with current reference variation (origin of the
axes), current loop responds correctly without overshoots; then the problem
is caused by speed control gain.
•
Step responce with acceptable proporzional gain
: current reference is fast
enough and speed step responce shows anly one overshoot.
In these cases, a too high integral gain, could leads to get more speed
overshoots.
P
R
•
Step responce with optimum gain
:
This condition leads to get performance and stability of system.
It’s recommended that noise amplitude
R
is lower than 15% of peak drive
current value.
6.16.3 Position observer tuning
Observer function allows to filter motor position information in order to reduce application noise due to speed
loop ruggedness, while maintaining sufficiently static and dinamic performances. This function is very usefull
when motor provide a low resolution feedback (lower than 1000ppr) or with Hall sensor only applications.
Observer function is available with all supported feedback type (sensorless not supported).
Position observer tuning must be performed with load connected to motor and only after speed loop tuning is
correctly done.
Usefull parameters are a Gain and a Bandwidth; the major filtering effect is due to bandwidth parameter, while
observer responce is due to gain parameter, whose default value is correctly set for a lot of application.
For a correct and safety tuning, it’s recommended to start with high bandwidth value, for example 300Hz where
observer filtering is very low, then decrease this parameter gradually untill the application noise reduction desired
is obtained.
!
Decreasing parameters excessively could lead to instability condition and to loss of motor controll, with
consequently risk of damage equipment.
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