I spoke to the motor specialist this morning, he says DC induction motors exist, in one design considered to be the most commonly used, the use of an exciter coil to start the flux conversion process is required because the transfered flux generated by the electromagnetic energy from the stator is insufficient to start the motor turning but sufficient enough to keep it turning.
Some require a separate excitation power source and others use the existing stator power source and generate/create the excitation power source, he also says this common type typically operate at a voltage of 400VDC to 600VDC, he further explained that unless your looking for massive power and minimum on times of > 1sec without direction changes such as conveyor systems and this type of motor is not really suitable for servo applications used in machining equipment.
Another design not so common has it's own flexible PCB inside which contains the components to take a lower stator voltage and create a higher voltage for excitation which is constantly applied but is also not suitable for servo applications due to the high starting current requirements, I have one of these motors and I was hoping to convert it to a servo motor so that's now out the window cause he said it wont work as a servo motor.
This kinda sucks cause I was thinking it would be nice to make a small induction motor specifically for this driver but he says without major changes and a costly motor design it wouldn't be possible in such a low voltage application to do it efficiently or inexpensively.
He also told me that some of the other motors I have which are AC/DC motors have both a squirrel cage and magnetic material but are not considered induction motors because of the magnetic material and operate at much higher RPM but induction is used at the higher RPM (above 4000) to offset the flux loss due to gravitational magnet force loss and this confuses me because magnet force I thought was constant based on it's material so how can it be affected by rotating it, not as simple as I thought it was.
On the weekend when I'm assembling my asynchronous servo spindle motors he'll have some drawings I can examine that shows the internals of a DC induction motor made for Georgia Pacific (I think they're a lumber company) and I'll get a more detailed explanation of the principles and technology involved.