18.07.2013 Views

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Checking sextant s 23 again for this new scheme reveals that a double transition would occur.<br />

S S S S S S S<br />

0 2 3 7 3 2 0<br />

LLLHHLLHLHHHLHLHHLLLL The fix for that could be to reverse the null states for sextant s 23 .<br />

S S S S S S S<br />

7 2 3 0 3 2 7<br />

HHH HHLLHLLLLLHLHHLHHH <br />

But then when the SV crosses a boundary, there would be a triple transition between the ending<br />

null state of the period for one sextant and the beginning null state of the period for the next<br />

sextant. Instead, the same null state order can be used for all sextants, but instead of always<br />

asserting X S<br />

<br />

before Y S<br />

<br />

, the order could be reversed for alternate sextants.<br />

S S S S S S S<br />

S S S S S S S<br />

0 X Y 7 Y X 0<br />

0 Y X 7 X Y 0<br />

For example, the sequences for sextant s 12 and s 23 would be as follows.<br />

s 12 :<br />

s 23 :<br />

S0<br />

SX SY S7 SY SX S0<br />

<br />

S0<br />

S1 S2 S7 S2 S1 S0<br />

<br />

<br />

LLL HLL HHL HHH HHL HLL LLL S0<br />

SY SX S7 SX SY S0<br />

<br />

S0<br />

S3 S2 S7 S2 S3 S0<br />

<br />

<br />

LLL LHL HHL HHH HHL LHL LLL Sextants s 12 , s 34 , and s 56 would be switched in the same order, and sextants s 23 , s 45 , and s 61<br />

would be switched using the alternate order. One reference calls this the “alternate reversing”<br />

sequence [83, p.260]. One SVM period is shown in Figure 4.38 for a commanded SV in sextants<br />

s 12 . The periods are equal in the figure but as the magnitude and angle of the commanded SV<br />

change, the time spent in each state will change. The leg control signals are shown; the<br />

instantaneous pole voltage waveforms would look the same but would switch between VDC<br />

and<br />

VDC<br />

as usual.<br />

195

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!