Graphical Representation of Signals

Abstract

Control engineering is mainly concerned with the control of large amounts of energy by means of ‘signals’ derived from a low-power source. A signal may be defined as a time-varying physical quantity carrying ‘information’ or ‘intelligence’. In the testing of systems the signals may be very simple in form but in actual operation they may be very complicated and even entirely random; for instance, consider a tracking radar system whose object is simply to point an aerial at a randomly moving target. During tests, artificial targets which perform simple movements such as ‘steps’, ‘ramps’ and ‘sinusoids’ will often be used. However, when the system is attempting to follow a target which is taking evasive action, the command signal will be virtually random.