Robust absolute stability analysis of a temperature control system for an enclosed space

This article demonstrates the possibilities of analyzing robust absolute stability of a temperature control system for an enclosed space (room, greenhouse etc.) by using an industrial drying cabinet as an example of such a closed space. The authors go tab transfer function with polynomials coefficients values of the numerator and denominator polynomials lying within intervals due to the possible range of values for time constant. In this work two methods have been used: graphical and analytical methods. Both methods are based on the application of Kharitonov's strong theory of stability of interval polynomials. The graphic al method of analyzing the system in question involves drawing a set of modified amplitude phase diagrams and Popov's line thus providing a visual demonstration of absolute robust stability of the temperature control system. The results of the analytical method, which are gotten by calculating the roots of Kharitonov's set of polynomials, are used to verify the results of using the graphical method.