[sdiy] Block based design was: Favourite VCO designs

[David G. Dixon]

> Frequency domain modeling? Can you give an example?

We don't do frequency domain modeling in process engineering, generally.
All process control modeling is done in the Laplace domain.  However, I
would imagine that structural engineers do a fair bit of it, to analyze
cyclic stresses on structures, etc.  I've done some frequency domain
modeling personally, to analyze fluid flow and dispersion in packed beds,
but this is not a standard technique in chemical engineering.  I never even
heard about the Fourier transform during my undergraduate days.


> D.
> 
> On Thu, Feb 25, 2010 at 19:39, David Ingebretsen <dingebre at 3dphysics.net>
> wrote:
> > There are comparable "components" across many engineering disciplines. I
> > took a whole course as an undergraduate where we learned frequency
> domain
> > modeling and the similarities between the building blocks used in
> different
> > engineering disciplines with emphasis on mechanical and electrical
> systems.
> > Quite fascinating.
> >
> > David
> >
> > ~~ -----Original Message-----
> > ~~ From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> > ~~ bounces at dropmix.xs4all.nl] On Behalf Of David G. Dixon
> > ~~ Sent: Thursday, February 25, 2010 10:27 AM
> > ~~ To: 'cheater cheater'
> > ~~ Cc: 'synth-diy'
> > ~~ Subject: RE: [sdiy] Block based design was: Favourite VCO designs
> > ~~
> > ~~ > it's indeed very useful to break up your designs into blocks and
> this
> > ~~ > happens in every discipline of engineering...
> > ~~ >
> > ~~ > However it's not good to think of them as completely separate
> blocks,
> > ~~ > since they can often negatively affect or even interrupt each
> other's
> > ~~ > operation...
> > ~~
> > ~~ Yes, of course.  In process (e.g., chemical, metallurgical,
> petroleum)
> > ~~ engineering, sub-plants are designed as discrete blocks, but they
> must be
> > ~~ sized to play their proper role within the overall mass and heat
> balances
> > ~~ of
> > ~~ the plant.  In other words, each block has a specific task to perform
> > ~~ within
> > ~~ the whole, but can effectively be isolated from the whole for
> detailed
> > ~~ design, just like electronics.
> > ~~
> > ~~ The analogy between chemical and electronic engineering is
> remarkable.
> > ~~ Indeed, I would classify electronics as just another branch of
> process
> > ~~ engineering.  The major difference is that process engineers are
> mostly
> > ~~ concerned with the steady state, while electronics is mostly
> concerned
> > ~~ with
> > ~~ the transient or cyclic response.  Where process engineering really
> > ~~ approaches electronics very closely is in the realm of process
> control.
> > ~~ Here, the engineer is mostly concerned with the transient response,
> and
> > ~~ how
> > ~~ to control the plant to ensure proper and smooth functioning in the
> face
> > ~~ of
> > ~~ various process upsets.  These upsets include delta functions
> (triggers),
> > ~~ step functions (gates), cyclic responses (waves), and noise.  Common
> > ~~ process
> > ~~ control elements include sensors (keyboard), controllers (VCFs and
> > ~~ envelopes) and valves (VCAs).  Indeed, when you get right down to it,
> a
> > ~~ chemical plant is really just one big modular analog synthesizer!
> > ~~
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