.OpenBLDC.Blocks.DetectCommutationIntBEMFext .OpenBLDC.Blocks.DetectCommutationIntBEMFextThis block determines the time when the next commutation has to
occur by detecting the zero crossing and (if enabled) the slope of
the voltage of the open motor phase. The back-EMF is sampled with
an ADC. The ADC callback is executed each time its buffer is
(half-) full, i.e. when
...cbStart ....
The ADC buffer is then evaluated by for f in 1:bufsize loop... Depending on the
selected PWM method, it may be required to evaluate only the
samples during t_on or t_off. Furthermore some potentially noisy
samples that are close to PWM switching events can be droped by
adjusting the dropnoisysamples parameter. All good
samples are stored in a circular buffer of the size
NREG where yreg[NREG] are the sampled
values and xreg[NREG] are their respective indexes.
The voltage zero crossing is determined by applying a linear fit to
all good values in the buffer. The index of the calculated zero
crossing (from the beginning of the ADC measurement) is
k_zc. This is not neccessarily the index of a valid
sample. The time of the next commutation event
time_nextblock is either calculated by evaluation of
the voltage slope (if modeSlope) or the duration
of the last voltage zero crossing. Note that the second method will
work robustly with the most motors while the first method
potentialy provides better dynamic response / acceleration while it
may cause trouble with motors with an "ugly" back EMF shape.
TODO:
1. Investigate the spike that occurs single leg mode as in Test.Commutation.IntBEMF3.