Re: [CAD_CAM_EDM_DRO] Servo bandwidth

dave engvall wrote:

> Jon Elson wrote:
>
> >
> > I'm getting great performance at 1 KHz from the CNC control, but
> > about 3-4 KHz bandwidth on the velocity loop.
>
> So what do you suppose is the real small signal bandwidth of the system you are controlling? This may not be correct thinking but
> for instance if you feed the servo a 1 mm pk to pk sine wave ... where does it roll off?

I actually have these graphs, as I have analyzed the servo system with a frequency response
analyzer. I was probably running the analysis at too small an amplitude, as the graph is
pretty noisy, but I didn't want to smoke the servo amps. There are 3 responses, for the
current loop, the velocity loop and the positioning loop. I vaguely remember a 300 Hz
bandwidth on pos, about 600 Hz for a first step rolloff, and 3 Khz for the final rolloff on
velocity, and something above 3 K (small signal only) on the current. When I did the
current loop test, the motors sang audibly out to 6-8 KHz! It certainly was interesting
hearing this thing 'talking' at several hundred Hz.

I will dig out the graphs and give a better report tonight.

Jon