Introduction to binary signals used in system identification

Concerns the design of input perturbation signals for system identification. It is possible in many cases to get a reasonable idea of the dynamics of a system from simple step response tests, but this is by no means always so. Quite often, process noise masks the step response, and to get round this the size of the step may have to be increased to a level that at best takes the system into a nonlinear region and at worst is too large for safe plant operation. This has led to considerable interest in periodic input perturbation signals whose amplitude can be kept small, with the input and output signals being processed in some way to give a reasonable estimate of the dynamics of the system. One particular type of signal, a pseudo-random binary signal has become widely used because it can be generated using simple shift register circuitry. These signals are discussed, together with binary multifrequency signals; other types of signal are mentioned briefly.<>