On 10/18/2020 12:07 PM, John Dammeyer wrote:
From: Jon Elson [mailto:el...@pico-systems.com]
I thought all servo motors did it that way. I can see they could also remove
the PWM from the windings completely for 0 power but if there's even the
slightest bit of load on the motor the closed loop would cause a correction to
hold it in place resulting in essentially the same behavior?
No, there are other schemes. My servo amps use a
sign-magnitude scheme, so zero PWM duty cycle is idle, and
it needs a direction signal, also. Due to the optocoupler's
distortion of really narrow pulses, there is a slight
deadband right near the null, but it really isn't that much
of a problem.
Also, the servo systems measure the current through the windings.
Yes, the classic velocity and torque servo systems do that.
But, some other systems don't, as the accurate current
measurement of a wire with huge voltage excursions is a
tricky problem.
Jon
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