Bill Powers

An Introduction to Perceptual Control Theory— Standing at the Crossroads

Many people have some sense of what control is about, but very few understand clearly how control works and even fewer (including control engineers) understand clearly what a control systems controls: Not “output” or “action” but perception of whatever is being controlled; that which action accomplishes. When you stop to think about it, you realize that a control system knows nothing about output or actions; it “knows” only what it senses. The distinction may seem trivial, but the consequences are profound. Bill Powers puts it all in context. […]

I control therefore I am therefore I control

Once around the loop

Elements of the control loop have been labeled slightly different by different people at different times and for different purposes, whether for a very plain explanation or for more mathematical treatment of the physical functions.  […]

Geese flying

PCT in 11 steps

Control is a process of acting on the world we perceive to make it the way we want it to be, and to keep it that way. Examples of control: standing upright; walking; steering a car; scrambling eggs; scratching an itch; knitting socks; singing a tune. Extruding a pseudopod to absorb a nanospeck of food (all organisms control, not only human beings). The smallest organisms control by biochemical means, bigger ones by means of a nervous system. […]