The Research Of Robust Nonlinear Control In Semiconductor Refrigeration System

In this thesis, robust nonlinear control is considered for semiconductor refrigerationbased aluminum plate thermal process, where peltier device, consisting of semiconductorcomponent, is nonlinear because the process temperature depends not only on inputcurrent, but also on the square of the input current and two side’s temperatures of thepeltier device. Also, absorb and give off heat are related to two temperatures and affectedby outside temperature such that there exist some uncertainty in the system. The peltieractuated aluminum plate thermal process is a typical nonlinear control affine system withuncertainties.For the nonlinear system with uncertainties, some nonlinear control designmethodologies have been presented, such as feedback linearization method, Lyapunovdesign method and so on. Most of them assume that measurements of all states areavailable, which are acquired in the systems modeling such that the mathematical modelsare obtained to represent the nonlinear systems and some states are required to feedbackto design nonlinear controllers. However, as a matter of fact, some states are measurablein the control system. Moreover, robust stability conditions are complex for somemethods. As a result, the existed control design methods often cannot generatesatisfactory performance. Therefore, robust nonlinear control is proposed for the peltieractuated refrigeration system by using operator based robust right coprime factorizationtechnology.Firstly, the basic theory of nonlinear system and operator theory is introduced.Definition of operator and operator based right coprime factorization are described. Also,the robust stability conditions of operator based right coprime factorization are analyzed.Then, the mathematic model of the peltier actuated aluminum plate thermal process isset up, and operator based robust nonlinear control is proposed without considering heatradiation. According to the heat balance of the aluminum plate and the basis of thermodynamics, a mathematic model of the aluminum plate is built only consideringheat conduction and convection. Because of the nonlinearity of the given system,operator based robust nonlinear control method is presented. The right factorization isgiven for the model and then the right coprime factorization controllers are designedaccording to robust stability conditions to ensure the stability robustness of the wholesystem. The simulation results show the validity of the model and the effectiveness of theproposed method.When the cooling temperature is larger, the influence of the heat radiation is larger,such that the effect of the radiation must be considered. However, after considering theheat radiation, it is not easy to right factorize the system by solving differential equations,so a method based on SVM is proposed to estimate heat radiation. Then, to ensure therobust stability of the nonlinear affine system considering the heat radiation, operatorbased robust right coprime factorization technology is proposed. Finally, simulationresults show that the influence of the heat radiation can be cancelled by using theproposed method.