Method of Stability Analysis for Nonlinear Automatic Control Systems of Peltier Thermoelectric Modules

Peltier thermoelectric modules (TEM) have several significant advantages over classic compressor-based cooling systems, such as better mass characteristics, non-dependence on special orientation, absence of moving parts, possibility of the precise temperature control over time, etc. In order to adjust different temperature regimes based on TEM, high quality automatic control systems are strongly needed. The development of such systems necessitates the use of complex models which take into account nonlinearities of the Peltier module itself, as well as different other blocks of the control system. The Functional diagram and model of the TEM-based climate control system have been represented. The transfer coefficients of nonlinear links and a scheme as a whole based on piecewise linear approximation have been obtained. A new methodology for modeling the nonlinear stability of climate control systems based on TEM under arbitrarily large impacting disturbances have been deleloped. The presented technique based on the Popov's frequency criterion and piecewise linear approximation allows an analytical study of absolute stability in general for any order of the model and with an arbitrary nonlinearities of components. Based on the proposed approach, Modeling of nonlinear stability of climate conltol systems based on TEM was done. As a result of the simulation, the stability areas of the system with various filters in the feedback loop were estimated. The possible application of the proposed approach in a future for optimization and synthesis of TEM control systems was briefly discussed.