AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 19

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

5.4 Sensorless Commutation Control
This chapter concentrates on sensorless BLDC motor commutation with BEMF Zero Crossing
technique.
In order to start and run the BLDC motor, the control algorithm has to go through the following states:
Figure 5-5
the rotation is started without the position feedback. When the rotor moves, the Back-EMF is acquired
so the position is known and can be used to calculate the speed and processing of the commutation in
the Running state.
•
•
•
Alignment
Starting (Back-EMF Acquisition)
Running
shows the transitions between the states. First the rotor is aligned to a known position; then
DSP56F80x MC PWM Module in Motor Control Applications
Freescale Semiconductor, Inc.
Figure 5-5. Commutation Control Stages
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commutations done?
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(BEMF Acquisition)
Minimal correct
Alignment time
Yes
Yes
Start motor
Alignment
expired?
Running
Starting
No
No
Control Technique
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