AN1913 Motorola / Freescale Semiconductor, AN1913 Datasheet - Page 42

• 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

Software Design
7.3.4.1 Commutation Control - Running state
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The drive starts by setting the Alignment state where the Alignment commutation step is set and
Alignment state is timed. After the time-out the Starting state is entered with initialization of
Back-EMF Zero Crossing algorithms for the Starting state. After the required number of successive
commutations with correct Zero Crossing, the Running state is entered. The Running and Starting
states are exited to the Stopped state, if the number of commutations with wrong Zero Crossing
exceeds the Maximal number. The commutation control is determined by the variable
StatusCommutation.
The State diagram of the Commutation Control Running state is shown in
in
Back-EMF Zero Crossing during the previous commutation period. If no Back-EMF Zero Crossing
was detected, the commutation period is corrected (Corrective Calculation 1). Next, the Commutation
time and commutation registers are preset. If Zero Crossing happens during the Per_Toff time period,
the commutation period is corrected using the Corrective Calculation 2. When the commutation time
expires, a new commutation is performed.
Error commutations
Section
Exceeded Maximal
Zero Crossing
5. The selection of the state after the motor commutation depends on the detection of the
Figure 7-8. State Diagram - Process Commutation Control
Reset
Stopped
Set Stop
BLDC control with BEMF Zero Crossing using ADC
BLDC Run
Running
BLDC Stop
Set Alignment
done
Set Running
Alignment
done
Set Starting
Starting
Alignment Timeout
with Zero Crossing OK
Minimal commutations
done
Figure 7-9
passed
and is explained