why we need to measure current in servo ac drive for PMSM motor?
i think we can use high resolution absolute encoder for speed calculation feedback and no need for current measurement.
totally we can use inner loop with speed PI and outer loop with position PI.
i don't know why all design trying to measure current...
if anyone know more please write your opinion here.
Controlling the current is a classical control technique for improving the system response. Slower outer loop with faster inner loop. It helps to simplify the overall transfer function of the speed and position loops, and enables them to be tuned in a better way.
Sorry for the long delay in replying...for some reason, updates from this forum had stopped coming to my email.