AN1913 Motorola / Freescale Semiconductor, AN1913 Datasheet - Page 52

• Manufacturer Part Number: AN1913
• Description: AN1913 3-phase BLDC Motor Control with Sensorless Back-EMF ADC Zero Crossing Detection using DSP 56F80x
• Manufacturer: Motorola / Freescale Semiconductor

Setting of Software Parameters for Other Motors
10.2.1 Alignment Period
#define x_PER_ALIGNMENT_S
Notes: For the first tuning, it is recommended to set this duration long enough (for example, 5 seconds).
10.2.2 Start-up Periods
#define x_PER_CMTSTART_US
#define x_PER_TOFFSTART_US
Notes: It is recommended to set
Notes: Setting these constants is an experimental process. It is difficult to use a precise formula because
Notes: Slowing down the speed regulator (see
52
The time duration of the Alignment state must be long enough to stabilize the motor, before it starts.
This duration is set in seconds in bldcadczcdefines.h.
The constants defining the start up need to be changed according to the drive dynamic.
All settings in this section are in bldcadczcdefines.h:
x_PER_CMTSTART_US
x_PER_TOFFSTART_US
Crossing is not sensed).
The unit of this constant is 1 s.
Next, set the first motor commutation period =
The Back-EMF Zero Crossing is not sensed during the first duration since it is very short. Hence, the
Zero Crossing information is not reliable during this period.
Table 10-2
Then, if the motor works well, it can be significantly shortened (for example, 0.1 seconds).
there are many factors involved which are difficult to obtain in case of real drive (motor and load
mechanical inertia, motor electromechanical constants, and sometimes also the motor load).
Therefore, constants need to be set for a specific motor.
above stated setting) is encountered.
high load motor
high load motor
Slow motor/
Fast motor /
mechanical
mechanical
Motor size
inertia
inertia
aids in the setting of constants.
is the commutation period used to compute the first (start) commutation period.
x_PER_CMTSTART_US
BLDC control with BEMF Zero Crossing using ADC
is the first (start) Toff interval after commutation (where Back-EMF Zero
x_PER_TOFFSTART_US = 2*x_PER_CMTSTART_US.
>5000
<5000
[ s]
Table 10-2. Start-up Periods
14400.0
7200.0
0.5
Section
x_PER_CMTSTART_US * 2
x_PER_TOFFSTART_US
/* Alignment period [s] */
/* Start Commutation Period [micros] */
/* Start Zero Crossing
10.3.1) helps if a problem with start up (using the
Toff Period [micros] */
>10000
<10000
[ s]
First commutation
period
>10ms
<10ms
[s]