Uncorrelated multisymbol signals for MIMO system identification

This paper presents a new approach to the system identification of a two-in put two-output multivariable system. In a similar manner to that used for t he single-input/single-output system, the multi-input multi-output (MIMO) s ystem response may be obtained directly from measured input output frequenc y responses. An investigation of compact multifrequency data measurement si gnals, which have been extensively cataloged by the authors, has provided c ompact multifrequency ternary and quaternary input signals that have uncorr elated spectra. They are powerful multisymbol, multilevel computer generate d measurement signals whose signal power is concentrated in either two or t hree dominant harmonics. As the signals, which are given in this paper, hav e six, seven, or eight symbols in their measurement codes, both the computa tion time for the frequency estimates and the experimental time are minimiz ed, Two multifrequency quaternary signals with uncorrelated spectra are use d to identify a simulated distillation column. It is shown that the cross c oupling terms between the measurement channels may be removed by these digi tal measurement signals with the same number of symbols but different measu rement codes.