AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 41

• Manufacturer Part Number: AN1914
• Description: 3-Phase BLDC Motor Control with Sensorless Back EMF Zero Crossing Detection Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

7.3.4.1 Commutation Control - Running State
Drive starts by setting the Alignment stage where the Alignment commutation step is set and
Alignment stage is timed. After the time-out the Starting stage is entered with initialization of BEMF
Zero Crossing algorithms. After the required number of successive commutations with correct Zero
Crossing are done, the Running stage is entered. If the number of commutations with wrong Zero
Crossing exceeds a pre-determined Maximal number, the Running and Starting stages are exited to the
Stop stage. The commutation control is determined by the variable StatusCommutation.
The State diagram of Commutation Control state Running is shown in
Section
BEMF Zero Crossing during previous commutation period. If no BEMF Zero Crossing was detected,
the commutation period is corrected using Corrective Calculation 1. Then the Next Commutation time
Error commutations
exceeded Maximal
•
•
•
Zero Crossing
— motor is powered with current through 2 phases - no commutations provided.
Starting (Back-EMF Acquisition) State
— motor is started with making first 2 commutations, then it is running as at Running state
Running state
— motor is running with Run parameters for commutation calculation RunComputInit.
Stopped state
— motor is stopped with no power going to motor phases.
5. The selection of the state after the motor commutation depends on the detection of the
using Start parameters for commutation calculation StartComputInit (so the
commutation advance angle and the Per_Toff time are different)
Figure 7-7. State Diagram - Process Commutation Control
Reset
DSP56F80x MC PWM Module in Motor Control Applications
Stopped
Set Stop
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BLDC Run
Running
BLDC Stop
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Set Alignment
done
Set Running
Alignment
done
Set Starting
Starting
Alignment Time-out
Figure 7-7
Minimal commutations
with Zero Crossing OK
done
passed
and is explained in
SW Design
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