Hi, everyone,

It seems that the main problem here is to measure a fast dicturbance/
influence by slow sensor while low speed on the output. So, it may
need to think about additional sensor and feedback loop for slower
speeds. What's 0.2 RPM, it's nothing for IR leds, if something let's
assume we have 0.02 RPM, what we could do now? We could say we cannot
to measure the speed, and to break our feedback loop with the IR, and
try to measure some another parameter such as output current while a
PWM pulse that depends on the influence.
So, I see a way is to have approximated data array for a range of
the slower speeds(it mean no loop, just control in normal mode), that
could be dynamicaly adjusted/corrected in accordance with a current
influence(here we begin to feel something about our motor).
As soon as the motor speed is so high to be measured, the element
could be controled by actual speed.

Best regards,
Oleg