AN1905 ST Microelectronics, Inc., AN1905 Datasheet - Page 69

• Manufacturer Part Number: AN1905
• Description: St7mc Three-phase BLDC Motor Control Software Library
• Manufacturer: ST Microelectronics, Inc.

– The appropriate value of K
– Confirm this result by trying several load conditions (if any) and slight speed variations to
– Repeat the procedure for several speeds to scan the entire speed range of the application;
■
The parameter K
In the current implementation, as mentioned above for sampling time set-up, the integral term
effectiveness is linked to the time interval between two PI regulator executions. This is to de-
crease the PI execution time (it removes one run-time calculation). Consequently, when
starting the parameter set-up, the sampling time T
after having tuned the K
mains constant.
The higher the K
sponse. Nevertheless, a value too too high will lead to instability (see
sponse vs K
termined below.
Figure 49. Speed error versus K
Here is an empirical method to tune the K
a reasonable phase and gain margin).
verify the system’s dynamic response. The K
in mind that the final static error cancellation will be handled by the integral part of the PI reg-
ulator. The only important points to be validated are the lack of unstable behaviour over the
whole working domain and a correct dynamic response (this last point will be further im-
proved by the integral term action).
for large speed ratios, it is most likely that several K
best results.
Tuning the Integral coefficient Ki
i
K
value). During the set-up, Kp and Ts must be kept constant with the values de-
p
= x, K
ST7MC THREE-PHASE BLDC MOTOR CONTROL SOFTWARE LIBRARY
i
, the faster the speed error cancellation will be and the better the dynamic re-
i
provides the remaining static error cancellation over time.
Speed
i
Target
=0
i
, the K
0
p
to start working with will then be K
i
parameter will have to be re-adjusted so that its influence re-
i
K
p
during the Ki set-up
and T
i
coefficient:
K
s
i
are constant
=20
p
can be slightly adjusted if necessary, keeping
s
should be frozen; if it has to be modified
K
p
i
=10
values will have to be used to get the
p
K
= K
i
=2
p limit
Figure 49
K
i
/ 2 (this is to provide
=5
Time
for speed re-
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