Principles of Feedback Control

Mafuyu KitaharaEnglish Theme8

2006-05-08

Summary of Chapter 2, Carver & Scheier (1998), On the Self-Regulation of Behavior, Cambridge Univ. Press.

Feedback control

Goal of Chapter 2To show abstract princplesExamples from domains other than psychology

Feedback processControl of regulation of values within a systemCybernetics: coined by Wiener (1948)BackgroundFirst computer in history: ENIAC (1946)Information science: bit, entropy, noiseSystems without internal control: e.g., clock, camera

Negative feedback (1)

Concept4 elements: input, reference, comparator, output

Negative feedback (2)

Example: thermostat

Effect on evironment? Output has indirect connection with input

Additional issues (1)

Sloppy vs. Tight controlhow precisely the comparator worksThermostat: 0.01, 0.1, or 1 degree deviation?

Lag TimeOutput function cannot work immediatelyThermostat:

Slow heater (steam) vs. Quick heater (gas)

Additional issues (2)

Intermittent feedbackDiscontinuous:

Output side: heater is only ON or OFFInput side: sensor works occasionally

Continuous: Automatic steering system in a ship

Further constructs (1)

Positive feedback loops

Thermostat example: set goal as more than 20C (needs upper limit)

Further constructs (2)

Open loop systems

No checking on the consequencese.g. Spark plugs in a car engine

Order: prespecifiedTiming: depends on the speed

Useful for high-speed control Precise, No lag time, No intermittency

Not useful for psychology

Feedforward

Anticipatory outputBest estimate

First cycle No input is available

Interdependency

Interaction between feedback loopsNot explicitly connected but disturbing each other

Reference value and input function

Slow adjustment of reference valuee.g.

Sleep hours

Hierarchies

Superordinate and subordinate systemse.g., person and thermostat