Pardon, but somehow my mailer got hopelessly confused in this last batch
so, I will probably be lacking references.
Bill Powers
Thank you once again for a fine discussion of a fundamental precept of
PCT.
I admit that I "sorta got lead into that one" with the "... even to the
destruction of the system of interest!" I still maintain however, that
even if the effect of the disturbance is ultimately the distruction of
the "system of interest" it is still just a disturbance.
I see that you are rather familiar with power steering systems. Please
note also that I am quite familiar with them (actually a great deal more
than I would like to be).
Please note, that I am fully aware that the typical power steering
control valve is actually one composite valve assembly and thus is in a
sense not two independent systems (short of mechanical failure).
Think about that, Bill. You're saying that if you center the steering
wheel, the front wheels will wobble left and right in an uncontrolled
way with every bump in the road. You know that isn't what happens. The
power steering works equally well with the steering wheel in any
position. What's the matter with this argument?
Well, what's the matter with that arguement is that is said that the
valve must be set to its' center and kept there. Something like what so
frequently actually happened quite often to the famous (infamous?) Ford
power steering valve. I was not talking about "centering" the steering
wheel (which indeed does not center the valve - normally the control loop
does that).
As far as I can understand your posting (and I think that I do), you
supported what I stated though I will admit that I was not particularly
clear on making the distinction between setting the valves position (as
in my example) and what happens when you move the steering wheel.
-bill