AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 38

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

SW Design
7.2.4 Process Current PI Controller
7.2.5 Process PWM Generation
7.2.6 Process Fault Control
7.3 State Diagram
38
(Omega_Desired)
.
The speed closed loop control is characterized by the feedback of the actual motor speed. This
information is compared with the reference set point and the error signal is generated. The magnitude
and polarity of the error signal corresponds to the difference between the actual and desired speed.
Based on the speed error, the PI controller generates the corrected motor voltage in order to
compensate for the error.
The speed controller works with a constant execution (sampling) period. The request is driven from the
timer interrupt with the constant PER_SPEED_SAMPLE_S. The PI controller is proportional and
integral constants were set experimentally.
The process is similar to the Speed controller. The I_Dc_Bus current is controlled based on the
U_Dc_Bus_Desired Reference current. The current controller is processed only during Alignment
stage.
The current controller works with a constant execution (sampling) period. determined by PWM
frequency:
Current Controller period = 1/pwm frequency.
The PI controller is proportional and integral constants were set experimentally.
The Process PWM Generation creates:
The Process Fault Control is used for drive protection. It can be understood from
DriveFaultStatus is passed to the PWM Generation process and to the Application State Machine
process in order to disable the PWMs and to control the application accordingly.
The state diagrams of the whole SW are described below.
Reference
Speed
•
•
the BLDC motor commutation pattern as described in
required duty cycle
-
DSP56F80x MC PWM Module in Motor Control Applications
Freescale Semiconductor, Inc.
Figure 7-5. Closed Loop Control System
Speed
Error
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Controller
PI
(U_Desired)
Corrected
Speed
Section 1.
Controlled
System
(Omega_Actual)
Actual Motor
Speed
Figure
7-4. The