Re: [CAD_CAM_EDM_DRO] +/- 10V Gecko

mariss92705@... wrote:

> Hi,
>
> In responding to a previous post I neglected to mention what I'm
> doing with the +/- 10V servo-amplifier. This will be the next drive
> coming out (45 days or so) and will be called the G330. In short:
>
> 18 to 80 VDC supply
> 20A max motor current
>
> Inputs: (jumper selected)
> -------------------------
> +/- 10 volt input
> 0 to 5 volt input
> PWM input (5V logic compatible)
>
> Operating modes: (jumper selected)
> ----------------------------------
> Velocity mode (output voltage proportional to input)
> Torque mode (output voltage proportional to input)
> IR compensated (motor speed proportional to input)
>
> Same size/price as G320.
>
> If it needs something else besides the above, please let me know. The
> board layout is nearly done and there is room left over. I can still
> fill it with something useful, (4 to 20 mA current loop input?).

I wonder how you accomplish tuning on this. I have a PWM velocity
servo amp, with an entirely analog front end (instrumentation amps
on all inputs, and op amps for each control loop). There are a great
number of pots on the thing, and all of them seem pretty important.
(command gain, tach gain, vel. loop comp, current gain, current limit,
current loop comp, and offset for the 2 loops). So, how do you
tune the response of your amp?

My velocity amps are set up as follows:

velocity error = Velocity command - tach

Current command = sign(velocity error) * | velocity error |

Current error = current command - measured current

Pulse width = current error

(of course, the compensation terms aren't shown above)

I can't tell from your description :
Velocity mode (output voltage proportional to input)
whether you are really doing the current loop or not. But, for
it to work well on large motors, the output voltage leads the
armature current by a lot. I guess I have a torque servo inside
a velocity servo.

Jon