4 Apr 2009

Trask, The Story of Cybernetics, Ch1, "Control"

by Corry Shores
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Maurice Trask

The Story of Cybernetics

Chapter 1: Control

Cybernetics is a matter of control. All our actions are controlled in either of two ways,
1) because we chose to do make some movement, or
2) we make an automatic reflex movement, like pulling our hands away from fire.

Cybernetics comes from the Greek word kubernetes, which means steersman or helmsman. It is also the root for the English word 'to govern,' which means also 'to rule,' 'to regulate,' and 'to control.' "The skill used in steering is one of continuous judgment."
The helmsman continually adjusts his tiller to keep the boat on course. He observes any variation from his course, estimates the adjustment needed to overcome it, moves the tiller, observes the result and repeats the process. (9c-d)
Our course of action is a series of approximations. So we control by minimizing error.
The helmsman corrects the error resulting from his previous attempt to correct a previous error. At the same time he must compensate for the effect of wind, current, speed and their resultant forces on the hull and rudder. (10d)
So to control our actions toward a goal, we must know our degree of progress. This requires some form of communication, which allows us to gauge efforts and compensations. (9d)

Trask offers this example: we pick-up an egg and put it in an eggcup.

First our hand moves toward the egg. Then our body corrects our balance. Our fingers grasp the egg with just enough pressure so that we do not break it. We lift it and place it in the cup.

We do not consciously tell each muscle to contract at the right time. Rather, we just set a goal: move the egg into the cup. Nonetheless, some of the actions, such as gripping the egg, require much care. If our hand is not regulated by feedback, we will crush the egg.

To reach the egg, we must guide our arm until we close the gap between our hand and the egg. This involves feedback, which are the messages our senses send to our nervous system with information regarding our hand's progress toward its goal. Then our nervous system sends messages to our muscles with instructions on how to act. As the muscles use energy to move closer, the feedback cycles repeat until we reach the egg.

We call the senses and the nervous system the "information" system. It carries reports and instructions. We call the muscles an "energy" system. It performs the work.
Cybernetics is the study and use of information systems to regulate energy systems. (14a)
Another example: we must park a car in the tight space between two other cars. Our passenger gets out and watches from the sidewalk. He uses his hand to motion us backward, and to tell us to halt. In this case, the passenger is the sensor. His hand signals are the messages. We, the driver, are the receiver. We put the messages into actions. So we are called the "effector." Together the two of us form the information cycle. And the car is the energy system. (14bc)

But consider when conditions change. If one of the neighboring cars begins to depart, we must make some decision. Should we wait? Continue parking? How we respond depends on the contingencies of the circumstance.

The classic example of a feedback loop is an automatic heating system. For contrast, first consider a simple heater. We turn it on, and leave it running. It will continue to heat the room until we can no longer stand the heat, and we must manually turn it off. Then, the heat will fall until the room drops to the outside temperature. Such a system is an open loop. It has no way to control itself or adapt to changing conditions.

We now consider a thermostat that can be set to maintain a certain temperature. When the room gets too cold, it turns on. Then when the air warms up to a certain degree, the heater turns off. This is a closed loop system. It oscillates between limits. And it can be designed to attain more efficiently the desired temperature. And if conditions change, such as a sudden rise in temperature outside, the thermostat can adapt. Closed loop systems, then, are governed by feedback. We find them in all cybernetic processes.

Many things can be cybernetic systems: children, animals, political systems, production lines, traffic, computers, storms, stock exchanges, and so on. (17d)

Trask, Maurice. The Story of Cybernetics. London: Institute of Contemporary Arts, 1971.

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