Re: [CAD_CAM_EDM_DRO]
Posted by
Jon Elson
on 2003-04-02 10:27:41 UTC
Dave Lantz wrote:
machine tool
servo amps use a velocity servo, which contains a torque servo as the
inner loop.
The torque servo has a feedback loop, so its command causes the amp to
make the
armature current in the motor proportional to the command. So, it has a
current
sensor and an amplifier that compares actual current to commanded current.
The velocity servo has a feedback loop that compares some measurement of
velocity (either by tachometer or encoder) to a command from the CNC
control. Its amplifier creates a torque command proportional to the
difference
between sensed and commanded velocity.
The positioning loop is generally made to include the CNC control, so
the encoder
feeds back to the control, and a velocity command is sent as an analog
signal
to the velocity servo amp.
Now, all the above applies to traditional servo systems from the 1960's
to the mid
1980's or so.
Many drives since then have more integrated functions, and get rid of
all the
analog signals. I think that's what your servopack is. The position
and velocity
commands are sent digitally between the CNC control and the drive.
Jon
>I am interested in understanding the difference between position servoWell, the traditional types of servo amps are torque and velocity. Most
>drives and velocity/torque servo drives. I have a wasterjet here that needs
>a replacement controller, and I need to know what I've got. Its a yaskawa
>servopack 200v, p/n: sgda-08ap, it appears to be an AC drive, and is labeled
>"position" as a type on a web page i found. another interesting thing is
>that the encoders appear to be wired to the servopack... does this mean the
>servopack is a servo amp taking step/direction pulses from the controlling
>computer, or that its a ±10V input from the controlling computer, thanks in
>advance, Dave L.
>
>
machine tool
servo amps use a velocity servo, which contains a torque servo as the
inner loop.
The torque servo has a feedback loop, so its command causes the amp to
make the
armature current in the motor proportional to the command. So, it has a
current
sensor and an amplifier that compares actual current to commanded current.
The velocity servo has a feedback loop that compares some measurement of
velocity (either by tachometer or encoder) to a command from the CNC
control. Its amplifier creates a torque command proportional to the
difference
between sensed and commanded velocity.
The positioning loop is generally made to include the CNC control, so
the encoder
feeds back to the control, and a velocity command is sent as an analog
signal
to the velocity servo amp.
Now, all the above applies to traditional servo systems from the 1960's
to the mid
1980's or so.
Many drives since then have more integrated functions, and get rid of
all the
analog signals. I think that's what your servopack is. The position
and velocity
commands are sent digitally between the CNC control and the drive.
Jon