Can a FOC control scheme be done using a rotary encoder to measure the position, speed and acceleration directly, or is measuring current necessary?
FOC is a motor control scheme as described in links below:
http://www.atmel.com/Images/doc32126.pdf
http://www.eetimes.com/document.asp?doc_id=1279321
Quote from the second link:
Field Oriented Control is one of the methods used in variable frequency drives or variable speed drives to control the torque (and thus the speed) of three-phase AC electric motors by controlling the current. With FOC, the torque and the flux can be controlled independently. FOC provides faster dynamic response than is required for applications like washing machines. There is no torque ripple and smoother, accurate motor control can be achieved at low and high speeds using FOC.
Best Answer
You appear to have two questions.
No; The point of field orientated control is to ... control the field in the electrical machine. This relies on knowing what the field is
Well, Field orientated control relies on knowing where the rotor is so that correctly phase aligned currents can be synthesised.
A rotary encoder (resolver, analogue hall effect sensing etc...) can be used to measure the instantaneous position & thus derive speed and acceleration. The existence of position sensing is to complement current sensing.
Sensorless control would remove the need for a rotary encoder, although the workable schemes end up using voltage sensing so "sensorless" is a bit misleading.