C
CC
- Jan 1, 1970
- 0
Hi:
An idea has been floating in my head for a few weeks, ever since
building an analog block commutation drive for a brushless DC (BLDC) motor.
It is a way to implement a sinewave drive on a BLDC motor which lacks an
encoder. The sine drives that I have seen so far require a high
resolution encoder to provide angular information from which to
synthesize the sinewave.
My idea is to use a PLL to multiply the hall sensor (or back EMF derived
position information if a non-sensor motor) frequency by some multiple
to create a sine generation clock.
Of course, there would be no dependable angular frequency to lock on
before the motor is running. So startup would be performed with simple
block (6-step, trapezoidal, so many terms...) commutation.
Once the motor was running and the PLL could track, the drive could
morph to sinewave mode.
Acceleration and deceleration of the motor would result in small
glitches in the sinewaves, but would still probably produce much less
harmonic current than plain block commutation. Very strong acceleration
could perhaps use block commutation temporarily.
Anyone ever tried this? Obviously not applicable to position servo
applications.
I just wanted to get it out in the public domain in case it hadn't been
patented yet ;-)
Good day!
An idea has been floating in my head for a few weeks, ever since
building an analog block commutation drive for a brushless DC (BLDC) motor.
It is a way to implement a sinewave drive on a BLDC motor which lacks an
encoder. The sine drives that I have seen so far require a high
resolution encoder to provide angular information from which to
synthesize the sinewave.
My idea is to use a PLL to multiply the hall sensor (or back EMF derived
position information if a non-sensor motor) frequency by some multiple
to create a sine generation clock.
Of course, there would be no dependable angular frequency to lock on
before the motor is running. So startup would be performed with simple
block (6-step, trapezoidal, so many terms...) commutation.
Once the motor was running and the PLL could track, the drive could
morph to sinewave mode.
Acceleration and deceleration of the motor would result in small
glitches in the sinewaves, but would still probably produce much less
harmonic current than plain block commutation. Very strong acceleration
could perhaps use block commutation temporarily.
Anyone ever tried this? Obviously not applicable to position servo
applications.
I just wanted to get it out in the public domain in case it hadn't been
patented yet ;-)
Good day!