Control systems or Cybernetics are characterized by the fact that they have goals: states of affairs that they try to achieve and maintain, in spite of obstacles or perturbations
Control systems are combinations of components (electrical, mechanical, thermal, or hydraulic) that act together to maintain actual system performance close to a specified set of performance specifications. Open-loop control systems (e.g. alarm clocks) are those in which the output has no effect on the input. Closed-loop control systems (e.g. automotive cruise-control systems) are those in which the output has an effect on the input in such a way as to maintain the specified output value. A closed-loop system must include some way to measure its output to sense changes so that corrective action can be taken. The speed with which a simple closed-loop control system moves to correct its output is described by its natural frequency and damping ratio. A system with a small damping ratio is characterized by overshooting the desired output before settling down. Systems with larger damping ratios do not overshoot the desired output, but respond more slowly.
Mechanistic World ViewEdit
In the mechanistic world view, there is no place for goal-directedness or purpose. All mechanical processes are determined by their cause, which lies in the past. A goal, on the other hand, is something that determines a process, yet lies in the future.
The thesis that natural processes are determined by their future purpose is called teleology. It is closely associated with vitalism, the belief that life is animated by a vital force outside the material realm. Our mind is not a goalless mechanism; it is constantly planning ahead, solving problems, trying to achieve goals. How can we understand such goal-directedness without recourse to the doctrine of teleology?
Probably the most important innovation of cybernetics is its explanation of goal-directedness. An autonomous system, such as a person or an organism, can be characterized by the fact that it pursues its own goals, resisting obstructions from the environment that would make it deviate from its preferred state of affairs. Thus, goal-directedness implies regulation of or control over distractions.
A good example is a room in which the temperature is controlled by a thermostat. The setting of the thermostat determines the desired temperature or goal state. Perturbations may be caused by changes in the outside temperature, opening of windows or doors, drafts, etc. The task of the thermostat is to minimize the effects of such influences, and thus to keep the temperature as much as possible constant with respect to the specified temperature.
On the most fundamental level, the goal of an autopoietic or autonomous system is survival, that is, maintenance of its essential organization. This goal has been built into all living organisms by natural selection: those that were not focused on survival have simply been eliminated. In addition to this main goal, the system will have various subsidiary goals, such as keeping warm or finding food, that indirectly contribute to its survival. Artificial systems, such as automatic pilots and thermostats, are not autonomous: their primary goals are constructed in them by their designers. They are allopoietic: which means their function is to produce something other ("allo") than themselves.
Goals as StatesEdit
Goal-directedness can be defined most simply as suppression of deviations from an invariant goal state. In that respect, a goal is similar to a stable equilibrium, to which the system returns after any disruptions. Both goal-directedness and stability are characterized by equifinality: different initial states lead to the same final state, implying the destruction of variety. What distinguishes them is that a stable system automatically returns to its equilibrium state, without performing any work or effort. But a goal-directed system must actively engage to achieve and maintain its goal, which would not be equilibrium otherwise. Control may appear essentially conservative, resisting all departures from a preferred state. But the net effect can be very progressive or dynamic, depending on the complexity of the goal. For example, if the goal is defined as the rate of increase of some quantity, or the distance relative to a moving target, then suppressing deviation from the goal implies constant change. A simple example is a heat-seeking head in a Stinger missile attempting to reach a fast moving enemy jet, cruise missile or helicopter.
A system's "goal" can also be a range of acceptable states, similar to an attractor. The dimensions defining these states are called the essential variables, and they must be kept within a limited range compatible with the survival of the system. For example, a person's body temperature must be kept within a range of approximately 35-40 degrees C. Even more generally, the goal can be seen as a gradient, or "fitness" function, defined on state space, which defines the degree of "preference" or "value" of one state relative to another one. In the latter case, the problem of control becomes one of on-going optimization or maximization of fitness.
- Heylighen F. & Joslyn C. (2001): "Cybernetics and Second Order Cybernetics", in: R.A. Meyers (ed.), Encyclopedia of Physical Science & Technology , Vol. 4 (3rd ed.), (Academic Press, New York), p. 155-170