2017.09.01 - Trying to figure out an algorithm to automatically adjust ui8_position_correction_value

Trying to figure out an algorithm to automatically adjust ui8_position_correction_value

The next oscilloscope screenshots were taken when the motor had a constant PWM duty_cycle value. Blue line represents hall sensors signal (at every 180º and not at 60º). Yellow line is the phase B current signal.
I sent commands by UART, to increase or decrease ui8_position_correction_value and saw the results when this value is above and bellow the correct value.
I repeated this test with other different PWM duty_cycle values/motor speeds and got similar results.

ui8_position_correction_value above value
As we can see, if we look at negative to positive transition of blue line, the current is negative (lower than half of max amplitude). The higher the ui8_position_correction_value, the higher amplitude of the sinewave and also the time difference between the transition of the blue line and zero cross of the yellow line. In this situation, the motor made a lot of vibrations, noise and was using to much current.



ui8_position_correction_value bellow
At the negative to positive transition of blue line, the current is now positive (see that the current sinewave is now inverted!). The lower the ui8_position_correction_value, the higher amplitude of the sinewave and also the time difference between the transition of the blue line and zero cross of the yellow line. In this situation, the motor made a lot of vibrations, noise and was using to much current.



ui8_position_correction_value best value
At the negative to positive transition of blue line, the current is almost zero as also the time difference to the zero cross of the yellow line. In this situation, the motor was quiet, didn't make vibrations and was using very few current.