Use of Identification Equations for a Model of the Black-Box Type in the Case of its Instability

A chemical-engineering system represented in the form of a black box with an input and an output is considered. The heat and mass transfer in this system was defined with the use of ordinary differential equations with constant coefficients of definite order. A method of use of "unstable" equations for the description of practical problems is proposed. The term instability was taken to mean that a differential operator has eigenvalues with a positive real part. The coefficients of an equation were determined on the basis of an analysis of the curve of response of the system to a disturbance in the form of a step. A concrete example of realization of the algorithm proposed is considered.