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Thinking in Diagrams

Chapter 9: Anticipation, Limits, and Nested Control

Drafted for Aryeh's edit.

For chapter 9: Anticipation, Limits, and Nested Control

Timing

Section titled “Timing”
  • Reading the chapter: about 11 minutes, its 1,684 words of prose at 150 words a minute. Not counted in those minutes: 2 figures, 1 pair, 2 understanding checks, the reading exercise and the exercises.
  • A session: 40 minutes, the exercises set for it. (estimate)
  • Afterwards: 105 minutes, the exercises set for then. (estimate)

Common misreadings

Section titled “Common misreadings”
  • Correcting every reading. In the bad diagram, the gallery’s humidifier changes its output at every door a visitor opens, and the lab’s check for a deadband finds none. In the chapter’s Common misreading, moving Deming’s funnel after each drop by the opposite of the last miss doubles the variance of where the marbles land (Deming, 1986, as Pyzdek reproduces it). In FC 07, the guitarist leaves the peg alone within 3 cents either way.
  • Saturation ignored: a wider gap expected to bring a larger correction. In the understanding check about a flooded basement, the dehumidifier removes at most 20 liters a day, and the air stays wet for a week. In CS 09’s self-check, once staff hours cut reaches its limit, a higher reserve required changes nothing.
  • Saturation drawn as a nonlinear effect. In the same understanding check, as a nonlinear effect on the signal from water removed to the basement’s humidity is wrong: the limit belongs to the corrective action, whichever signal reaches it.
  • Feedforward taken to replace the control loop. In the reading’s second question, Nothing while the rate of incoming fluid changes is a wrong choice for what is left for B1: a gap at the outlet, from the rule’s misjudgments or anything else, is read only through B1.
  • An override read as a new target. In the understanding check about a smoke alarm, a new target: a higher trigger for smoke is a wrong choice for the hush button, which replaces the loop’s rule for ten minutes, the trigger unchanged.

Exercises to set

Section titled “Exercises to set”

The session goes from feedforward at a concert’s gates, through a deadband and a delayed reading, to a published furnace with feedforward; shared corrective actions, an override, nested loops with a limit and the case come afterwards.

For a session

Afterwards

Sources

Section titled “Sources”