•
MID: Config El DQ-switch
- Axis switch for AC signal (0 for d-axis, 1 for q-axis).
•
MID: Config El I DC req (d-axis)
- Required DC current in d-axis.
•
MID: Config El I DC req (q-axis)
- Required DC current in q-axis.
•
MID: Config El I AC req
- Required AC current.
•
MID: Config El I AC frequency
variable - Required frequency of the AC signal.
8.6 MID algorithms
This section describes how each MID algorithm works.
Stator resistance measurement
For the stator resistance
R
s
measurement, please, refer to the documentation of
AMCLIB_EstimRL
.
Stator inductance
For the inductances
L
d
and
L
q
measurement, please, refer to the documentation of
AMCLIB_EstimRL
function from
BEMF constant measurement
Before the actual BEMF constant (
K
e
) measurement, the MCAT tool calculates the current controllers and BEMF observer
constants from the previously measured
R
s
,
L
d
, and
L
q
. To measure
K
e
, the motor must spin.
I
d
is controlled through
I
d meas
and the
electrical open-loop position is generated by integrating the required speed, which is derived from
N
nom
. When the motor reaches
the required speed, the BEMF voltages obtained by the BEMF observer are filtered and
K
e
is calculated:
When
K
e
is being measured, you have to visually check to determine whether the motor is spinning properly. If the motor is not
spinning properly, perform these steps:
• Ensure that the number of
pp
is correct. The required speed for the
K
e
measurement is also calculated from
pp
. Therefore,
inaccuracy in
pp
causes inaccuracy in the resulting
K
e
.
• Increase
I
d meas
to produce higher torque when spinning during the open loop.
• Decrease
N
nom
to decrease the required speed for the
K
e
measurement.
Number of pole-pair assistant
The number of pole-pairs cannot be measured without a position sensor. However, there is a simple assistant to determine the
number of pole-pairs (
pp
). The number of the
pp
assistant performs one electrical revolution, stops for a few seconds, and then
repeats it. Because the pp value is the ratio between the electrical and mechanical speeds, it can be determined as the number
of stops per one mechanical revolution. It is recommended not to count the stops during the first mechanical revolution because
the alignment occurs during the first revolution and affects the number of stops. During the
pp
measurement, the current loop is
enabled and the
I
d
current is controlled to
I
d meas
. The electrical position is generated by integrating the open-loop speed. If the
rotor does not move after the start of the number of
pp
assistant, stop the assistant, increase
I
d meas
, and restart the assistant.
Mechanical parameters measurement
The moment of inertia
J
and the viscous friction
B
can be identified using a test with the known generated torque
T
and the
loading torque
T
load
.
NXP Semiconductors
Remote control using FreeMASTER
MCUXpresso SDK Field-Oriented Control (FOC) of 3-Phase PMSM and BLDC motors, Rev. 0, 01/2022
User Guide
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