On 10/18/2020 03:57 AM, Chris Albertson wrote:
The above is not the way it works. No one would design
anything like that. But let's say you did. What would
happen? The motor would vibrate and slowly rotate and have
close to zero torque
The Geckodrives G-320 series, for one, does this. A number
of other PWM servo drives from the well-known manufacturers
such as Servo Dynamics, Copley, AMC and others do the same.
The advantage is there's no dead zone around the null
point. The disadvantage is a lot of power dissipation in
the transistors and motor. Many of these drives require a
series inductor in the motor wires to control the
triangle-wave current.
Yes, the motor has zero torque at the null, that is by
design. As soon as the following error is non-zero, the PWM
duty cycle shifts from 50-50 to an asymmetric ratio, and the
torque increases. That's the whole point of a servo system.
Jon
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