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BLDC sensorless control Using LPC17xx

Question asked by Milad Mohammadi on May 16, 2016

Hi guys, recently I've been working on LPC1768 for sensorless control of BLDC motors, but I have numerous problems regarding of ADC sampling for BEMF zero crossing detection and in short position estimation. Actually I want to start with the simplest possible ways of sensorless control and then I will move to FOC. The method I'm using is like sampling free phase in the middle of PWM pulses, so I set the PWM mode on center aligned mode and I have activated the LIM register interrupt, so when ever I have an interrupt of LIM register, it means I'm in the middle of the PWM pulse.After that I start the Burst mode of ADC and then as soon as the result of 4 ADC channels including DC bus voltage, Phase A to PhaseC voltage become ready using an ADC ISR I will read them all. Actually the method of interrupt is like this: I activate interrupt only for channel 5 of the ADC, then when the interrupt occurs I start reading the ADC value of 1-4 channels. ( channel 5 is not important, just used to trigger the interrupt when all the other channels are ready to be read). As a matter of fact I'm not sure what am I doing is right or wrong? what is your opinion ?