Introduction

Abstract

Modern control systems include an important subclass of systems which coordinate the processes with a discrete state set. Although the term “system state” is intuitively clear to the reader, in the subsequent discussion it can be, and will be, refined as may be required, depending upon the particular syntax and semantics of a system model description language. A typical example of a system with a finite number of states is the data exchange control in computer networks. This, however, does not exclude the presence of continuous, or analogue, variables. For example, the tool displacement in a metal-cutting machine can be characterized by coordinates of the cutting edge of the tool, by speeds of coordinate drives, by components of forces on the tool, etc. However, such variables as turn-on and turn-off of driving motors, the status of the reduction gear, the presence of information about the next operation modes and many other variables constitute the system’s discrete state. A sequence of such states realizes the discrete control of the machining process. Similar examples can be found in various fields, for example, in control of the starting and stopping of a power plant, or in control of motions and displacements of robot arms, to mention but a few.

And so time does not exist per se, on its own. Objects themselves create a sense of what has gone with centuries, What is going on now and what awaits us in the future

Lucretius Carus