Block diagram of a program control system

Conventional signs:

1. Program block;

2. Control device;

3. Controlled process.

Such a regulation may be executed using an open-loop or closed loop contour, or their combination.

There are two kinds of program control systems:

- systems with a time program (devices which transform, say, balanced clockwork running into the movement of function converters - profiled rheostats or cams);

- systems with a special program (program motion control according to the established trajectory, say, the motion of milling cutter in NC lathe etc.).

1. Servo (follow up) system

In servo systems functional algorithm is unknown beforehand. Usually controlled variable in servo systems must reproduce the change in some external factor, “follow” it.

Example:

- Air-defense gun installation must trace air target maneuver, being directed to the calculated anticipating heading taking into account the trajectory of gun projectile.

Servo systems may be built according to any fundamental principle.

We may indicate as one of the first servo systems the device invented by Mishelle (1750) designated to turn windmill’s tower towards wind direction.

Further the number of control algorithms increased. We must also mention extremum seeking, optimization and adaptation algorithms.