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Software Design Considerations
5.6.1 Processes: Latest Position Capture, Period Measuring, and Speed Calculation
The latest position capture, period measuring, and speed calculation
processes relate to the inputs of the Hall sensors. The sensors generate
streams of pulses that are captured (separately for each sensor) by the
input capture (IC) function. The process latest position capture captures
the latest state of the Hall sensors.
The processes period measuring and speed calculation read the time
between the adjacent rising edges of Hall sensor output and calculate
the actual motor speed variable speed.
5.6.2 Process Speed Controller
This process calculates the duty cycle of the PWM based on the output
of the speed controller (the PI controller).
5.6.3 Process MOSFET Gating Selection
This process calculates which PWM channel is enabled for PWM
generation. Two commutation schemes are present here. In the file
main.h, a compiler directive allows the programmer to select between
the two MOSFET scheme and the three MOSFET scheme. For the
deadtime insertion there are things which should be noted.
If the three MOSFET commutation scheme is selected by the directive:
#define MOS_3_COM
#undef MOS_2_COM
The PWM module automatically makes deadtime insertion by
hardware.
If the two MOSFET commutation scheme is selected by the directive:
#undef MOS_3_COM
#define MOS_2_COM
Deadtime insertion is done by software and PWM module
configuration.
DRM007
BLDC Motor Control Board for Industrial and Appliance Applications
84 Software Design Considerations MOTOROLA