Reconstruction

Tim Wescott wrote:

A little RC to round the corners sets my mind at ease. I squirm if I can
hear the DAC on the radio.

Jerry
--
Engineering is the art of making what you want from things you can get.
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wrote:

Most actuators provide enough roll-off to filter the output from the
DAC, but I suppose if the control software didn't implement smooth
switching between control modes that might cause a transition from Max
to Min output, then a low pass filter might be needed to prevent the
excitation of high frequencies in the system.

In sampled-data theory (which has similarities with discrete-time digital
systems), the
sample-and-hold device (the DAC in a digital system) is itself a low-pass filter
which does the
reconstruction of the signal to produce a continuous-time signal from a
discrete-time (sampled)
signal. Of course, the reconstructed signal then still has a stair-case like
appearance; but this
is not usually a problem because, as you say, the appropriate choice of sampling
frequency as a
function of the plant's frequency bandwidth means that the controlled system
itself provides
further low-pass filtering; so that the stair-case like output signal becomes an
smoothed
response in the actual controlled system.
Kelvin B. Hales
Kelvin Hales Associates Limited
Consulting Process Control Engineers
Web: www.khace.com

I haven't used it; but I would think the design considerations would be
covered in articles/books on microstepping of stepping motors.  The
engineering theory must consider both the time and space resolution in
order to do the design.
Never had to do microstepping myself though, so I can say for sure.

Rrogers