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FOC 4.3 Dual Motor Control:  incorrect RPMs

Question asked by scott boeshart on Jun 2, 2017

Using STM32F415 for dual motor control with FOC 4.3:  ST Forum users:  FOC library is running the dual BLDC motors higher than the RPM setpoint.  I'm using setpoint values that are divisible by 6 to get the even tenths of a mechanical hz.  At RPM of 3102, the motors run at about ~3114 RPM.  Has anybody run into this?  I've used different electrical angle settings, along with PID gain adjustments, but can't get past this problem.  Thank you in advance!

 

Update:  Somewhere there is a latency or incorrect calculation.  Slowed the PLL down by .5Mhz (.35%) and the RPM is nearly spot on.  Overall, the motor control library thinks the system is running at 3102 but physically the motor is turning at 3112-3114RPM.  

 

Will dig into source code to see if timers and speed calculations are correct.

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