The main thing I accomplished this week was looking into the details of the STM32F4’s timer. One of the basic elements of motor control is providing PWM signals to the MOSFETs, and care must be taken in exactly how the signals interact. The high side MOSFET (attached to power) and the low side MOSFET (attached to ground) cannot be turned on at the same time (or they explode), so the timers provide complementary PWM outputs and allow you to insert dead time in between (where neither output is turned on). This will ensure that we don’t short power and ground together, so getting it right is critical.

 

I spent time reading the manufacturer’s timer drivers and cross-referencing with the microcontroller datasheet to make sure I understood exactly what the drivers are doing, so that I can use them properly to run the timers. During the next week, I plan to get the timers working and begin working on the ADC triggering, which needs to happen at a specific time in the PWM cycle. We will need this to properly sense voltage and current in the motor phases. I also plan to read an in-depth paper on sensorless motor control to get a better understanding of the theory before working on the actual motor control firmware in the future weeks.