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Old 09-30-2015, 05:45 PM   #2120 (permalink)
MPaulHolmes's Avatar
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
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Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
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Here are a couple graphs:

back emf angle (found sensorlessly vs the rotor flux angle found using the encoder and a bunch of random formulas haha):

Here is a graph of the sensorless BACK EMF angle lagging behind the sensored rotor flux angle at about 1.5Hz mechanical:

Here's a graph of the motor post spinning at 30.1Hz (x-axis ticks are 0.0001 sec):

Notice how nicely the back emf angle is tracking the rotor flux angle!! Even at 1.5Hz it's really not doing that horribly. I think I can improve on the 1.5Hz thing too and push it below 1Hz.

I'll get a hex file to you, and you can try out the sensorless code. although, I haven't actually used the sensorless to drive the motor yet. I was just trying to verify that I could obtain the rotor flux angle from the back emf angle somehow. It looks like you just subtract off like 20% of a period, but I think I remember someone saying that it's actually 90 degrees offset, so maybe my sensored rotor flux angle is off by a few %?

Hey! We could have a contest to see which spins the motor post faster. The one that spins it the fastest is making better use of the fixed Id and Iq!
First, we need to determine your motor's stator and rotor inductance, and a stator coil resistance. In my case, it works fine to just use the same rotor inductance as stator inductance. To figure out the stator inductance, we have to run a test and measure the offset of 2 waveforms. I'll set it up, and make sure it's working on my end before sending it over to you so you don't get stuck with a crappy hex file.
kits and boards

Last edited by MPaulHolmes; 09-30-2015 at 06:44 PM..
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