Re: [CAD_CAM_EDM_DRO] Bandit servo drives and tach

bankgarter wrote:

>Guys,
>
>I inherited a SuperMAX fitted with a VERY old closed-loop Bandit
>(still Summit/Dana) from a buddy of mine. As I have built antenna
>positioners in the past I think I can actually do something with this
>rig! However, the many years of wipe-downs have left the Dana
>RapidSyn servo motor labels shiny clean, as in NO data. Any idea what
>kind of voltage and current these guys like? I hotted up the X axis
>leads with a DC power supply and got the motor to spin with 5-30 VDC
>at about 2A.
>

If you measure the no-load speed of the motor, or spin the motors at a known
speed and measure the voltage output, you get the Kv, in volts/thousand RPM
for the motor. The Kt (torque/Amp can be computed directly from the Kv.)
The only other measurements you need are the continuous and peak torque
ratings, which are harder to get.

But, RapidSyn sounds a lot like a trademark for a STEPPER motor. I guess
if you got it to spin with a DC supply, then it is a DC servo, for sure.

> However, I know there's more top end but I don't want to
>burn things up. Moose took good care of this old bugger and I'll be
>danged if I'm going to be the one that cooks things. Also, any
>feedback on the...feedback? I know it is resolver based but does
>anyone know if it is multi-speed and what the characteristics of the
>resolvers are?
>
>

Multi-speed? I have no idea what that means. Do you mean that the motor
can run at different speeds? Yes, of course, a servo drive moves at the
speed commanded by the CNC control.

A resolver is a magnetic device that measures position. It has a coil that
is excited by a high frequency (400 Hz to 8 KHz, typically) sine wave.
The magnetic coupling between that coil and two pickup coils varies as
the shaft is rotated. The pickup coils are arranged so that as the signal
peaks on one coil, it is near zero on the other. This provides the familiar
90 degree phase relationship that is used by optical encoders and glass
scale linear encoders to derive distance and direction. But, since most
resolvers have much coarser resolution, interpolation is almost always
used.

You can buy resolver to quadrature converters, but they are probably
more expensive than an optical shaft encoder. So, the easiest thing
is to put shaft encoders on the machine.

Then, you can choose a servo amplifier based on the characteristics
of the motors. You can go with Gecko step/direction servo drives,
or Rutex units if you need more voltage. Or, you can use real analog
servo amps with a program and motion control interface.

Jon