Tightly coupled

From Dag Forssell [920326 - 2]

Gary asked about "Tightly coupled". Imagine that you are playing the rubber
band demonstration with a strong machine, programmed to go through a set pattern
of motion.

You have no difficulty, since the machine only influences the position of the
knot, through the tension in the rubber band.

Now "tightly couple" the knot to the machine by substituting a stick (or a rope
as I like to do when demonstrating conflict between two "pullers"). If you still
are connected to the knot by a rubber band on your side, you will pull in vain.

If the stick is extended to your hand, you will be pulled along, powerless to do
otherwise. You are being controlled by the machine with overwhelming physical
force, the only way Bill says you can be controlled.

I believe it is important to remember one of the hallmarks of control systems:
amplification. This term does not communicate well. I am shifting my language
to "the direction of resources" or something like that, with emphasis on
resources. Your heating system at home opens a valve to release (and ignite) a
stream of natural gas. The stream is not finely calibrated, but has a powerful
influence on tha air temperature.

If you have an air conditioner working at the same time, set at 68 degrees,
while the heater is set at 75, the two will pull (with tight coupling) on the
air temperature knot with as much influence as each is capable of.

If the gas line has the capability to release more resources to raise the temp
than the air cond has resources to lower it, then the air temperature will stay
at 75 degrees.

The rubber band is such a marvelous tool, because it shows influence without
tight coupling. Try the demonstration with a rope, and two dots. One towards

and one a little to the right as a target for the person on the right. This will
illustrate the heater / air cond conflict.

A detail: The heater and the air cond are separate control systems, as in wall
heater and window air cond, with separate thermostats.

Hope this helps. Enjoy your questions.

Dag