This is more of a practical question. I understand feedback and how it work s and can design controllers. However, these have been for dc (non PWM) mot ors using tachos with a dc output.
What I want to know is how you achieve this with digital tachos which give out pulses.
I am thinking that the set point is still dc as before (or software based) and you just count the pulses from the tacho in a given time and this giv es an error signal which you then generate PWM from - am I right? the rest is usual lag-lead compensators etc.
Another approach I suppose would be to have a square wave as the set-point and use the pulses from the tacho and create a phase-detector and PLL appro ach.