speedict said:
Ken Taylor said:
Wow that was a fast reply. I thought FOC controllers would be available in the RC world similar to this trapezoidal ESC from hobby King http://www.hobbyking.com/hobbyking/stor ... duct=10331 but as far as I can tell they aren't available anywhere.
it is difficult to develop Sinusoidal commutation controller on rc world because its lack of hall sensor, also rc just need high rpm instead !
I understand most of the noise in RC motors is from torque ripple which Sinusoidal commutation would remove and that would be very nice.
I only just realised that field oriented control and sine control is not the same thing from this post by Burtie at http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=44910#p654534 but the R8C/25 application note you posted says on pg3, "As many
brushless motors have sinusoidal BEMF (called Permanent Magnet Synchronous Motors PMSM), it is possible to
match these motors with a sinusoidal driving voltage". Therefore for these motors FOC and sinusoidal commutation produces the same controller output and the sinusoidal commutation algorithm is simpler. Burtie's Microchip dsPIC33 kit has algorithms for sensorless position detection that would be suitable for sinusoidal commutation but he finds it complicated to get them to work as described at http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=44910#p654203
speedict said:
Ken Taylor said:
I can't understand why all BLDC motors that use hall sensors are not FOC as their doesn't seem to be any negatives except perhaps MCU cost. Is their a gap in the market, is it the extra MCU cost or is it something I'm missing?
Sinusoidal commutation is complicated on both hardware and software that's what you referred to "cost" e.g. hall timing and sequence is critical on sinusoidal, Trapezoidal communication need to control 1 x pwm signal but Sinusoidal need 3 ...
The hardware cost could make it uneconomic but software cost, is once off and if sinusoidal is better it should be able to be spread across every motor controller sold. It needs good engineers but Speedict seems to have them.
speedict said:
you can see most of the china made speed controller still use transistor to drive its mosfet because of COST, cost is everything to them, i have conversation with "some of them" as per their mindset if they can save $1 component cost each, when sold 10,000 units they can save $10,000
they don't even think about if they put $2 component cost they can sold 100,000 units
I'm interpreting your statement "they don't even think about if they put $2 component cost they can sold 100,000 units" as a belief that there is a gap in the market.