My application is a direct drive PNP part rotator <https://hackaday.io/project/165115/log/162673-rotator-runout>. AKA... basically zero load beyond rotor inertia, and comparatively slow speeds.
The BLDC motor will be used more like a stepper... but a really smooth and extremely light one. I would say there is an 85% chance I'll just be running this open-loop, and just following a sine wave for the amplitude (via PWM) of the 3 phases. Kinda like how microstepping works for a regular stepper for 2 phases (ignoring current chopping).. that will be this for 3 phases. It will work <https://youtu.be/667XSSxieXM>, I just need to generate the 3 channels of PWM tied to a sine calculation or lookup table, space them 120 degrees apart, and then tie that to a rotational axis. This is the minimal implementation and assumes your motor can handle full current stalled all day and not overheat. A proper implementation would be also PWM one or all of the enable lines. Then add a reading on the coil current/back EMF of all 3 phases would give you what you need to do field oriented control <https://en.wikipedia.org/wiki/Vector_control_(motor)>. Those could happen, just like a Hall effect rotation sensor could happen if I'm desperate, but I think I'll be fine with just open-loop. I could just build it up with the other components, but I'm inherently lazy (usually an asset for a programmer actually) and looking for a canned solution before I do so. Or I could just add it to the existing bldc component but I'll probably screw that up for a while.. Thank you. On Saturday, April 27, 2019 at 5:06:36 PM UTC-4, justin White wrote: > > I run a brushless spindle motor with the BLDC component and a Mesa 8i20. > The waveform depends on the personality selected and usually only starts in > trapezoidal mode if using hall sensors then switches to sinusoidal. I can't > much of the gritty details of setting it up and waveform wasn't a huge > thing when I configured my mill. I had more of a fun time getting the PID > setup than anything, but that's mostly due to the fact that the 8i20 is a > torque mode drive rather than a velocity mode drive. I haven't touched the > config in a while as my mill just runs now. > > I'm not sure what "resembling microstepping" means for a brushless DC > motor. Alot of the BLDC component relies on the feedback. It's best for > running servo's where the drive itself can be dumb and the Linuxcnc > hardware/software can handle commutation based on feedback. There's a few > modes which can run without feedback but the usefullness depends on what > you're doing. > > On Saturday, April 27, 2019 at 4:03:59 PM UTC-4, [email protected] > wrote: >> >> Got a project where I will be doing pwm of the three phases of a bldc >> motor implementing sinesoudial drive for something resembling micro >> stepping. >> I saw the bldc component but it looks to be a trapezoidal implementation. >> Anyone whipped this up before I do? Basically 3 pwm lines following a >> sine wave 120 degrees apart. >> >> Thank you. >> > -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
