Monday, January 26, 2009

Encoder has arrived

I purchased a BEI encoder from ebay a while ago and now have it in my hot hands. I intend to attach it to whatever motor I use as velocity feedback. That should allow me to create some sort of vector control for the motor. I've been reading a lot, but I am still unsure how the math works, but at least I think I know what the pieces are.

angular velocity of the rotating magnetic field, or frequency of the output (I can control this)
total voltage (I can control this)
output current (I can measure this)
speed difference between magnetic field and rotor, also called slip (I can measure this)

My thoughts are that the gas pedal will be attached to a pot that will essentially be a torque request. The controller will always output a frequency a bit faster than the moving speed of the rotor based on the motors slip. Based on the torque request, the voltage will be changed to get the requested current.

We'll see. Now I just need a few hundred volts dc and a motor to try it on.

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