I've just signed-up for this group, searched for an answer, couldn't find it, but am impressed with the knowledge here.
My requirement is to drive a leadscrew at a fairly constant rate, but with a large speed change for traversing quickly. Thus I need a motor whose speed can be controlled fairly tightly at low r.p.m., and then can be told to 'take off' at a speed maybe 50 times the normal 'controlled' speed. The load is light and fixed, and the motor will have to be geared-down quite a bit anyway, affording substantial torque multiplication.
Originally I was going to use a micro-stepped stepper motor, but the rotational output really needs to be more 'analog' than 'digital'; that is, very smooth, not composed of small, fixed incremental steps. I have not played with a BLDC yet and will probably start with one off eBay, along with a ready-made controller board.
Obviously the higher get-there speed can be close to motor's maximum; again, the load is very light. So my question is, can a speed between 1/25 and 1/50 (4% to 2%) of the top speed of a BLDC motor be electronically controlled with decent precision, maintaining that lower, 'working' speed within a few percent, assuming that the load does not change appreciably? And... what characteristics of the motor and ready-made controller (DC or PWM speed input) should one watch out for?