Flying Electron wrote: > > The Pico system you make looks very nice and is something I will > consider. I don't really have a full understanding of how the brushless > servos work, but I'm slowly learning. So far I think I understand that > they are like stepper motors just with 3 steps instead of 200, which > allows them to spin at high rpms since there is more time for the > magnetic field to build in the coils This is mostly true, but the common brushless motors have 24 "steps" if you want to think of it like that. > since the coils only have to be > switched on and off 3 times per rev. But if this is correct, wouldn't > stopping and holding the position of the motor somewhere between the > poles be like how microstepping works on stepper motors and it wouldn't > be that accurate? > The ENCODER is the difference. A stepper can only stop on full or half steps, or to some extent between them by microstepping, but the position is influenced by any torques on the motor shaft, such as spring or friction. A servo measures actual position and applies torque as needed to correct the error. So, applying a little torque to a stepper deflects it from the true position, and it has no way to sense this has happened. A servo applies torque as needed to keep within whatever error bound you have set it for. I have some brushless servos on my minimill with 500 cycle/rev encoders, and they can position to very fine tolerance, and stay within small error even up to high speed.
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